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Working Draft January 2011

Inflow and Infiltration Management Plan Template

metro metro metro metro vancouvervancouvervancouvervancouver

Working Draft January 2011

Inflow and Infiltration Management Plan Template

KWL File No. 251.242-300

INFLOW AND INFILTRATION MANAGEMENT PLAN TEMPLATE WORKING DRAFT

JANUARY 2011

KERR WOOD LEIDAL ASSOCIATES LTD. Consulting Engineers 251-242

METRO VANCOUVER

STATEMENT OF LIMITATIONS

This document has been prepared by Kerr Wood Leidal Associates Ltd. (KWL) for the exclusive use and benefit of Metro Vancouver and the member municipalities. No other party is entitled to rely on any of the conclusions, data, opinions, or any other information contained in this document. This document represents KWL's best professional judgement based on the information available at the time of its completion and as appropriate for the project scope of work. Services performed in developing the content of this document have been conducted in a manner consistent with that level and skill ordinarily exercised by members of the engineering profession currently practising under similar conditions. No warranty, expressed or implied, is made.


JANUARY 2011

KERR WOOD LEIDAL ASSOCIATES LTD. Consulting Engineers 251.242

METRO VANCOUVER

CONTENTS

1. EXECUTIVE SUMMARY...................................................................................1-1 1.1 BACKGROUND.................................................................................................................................1-1 1.2 OVERVIEW OF I&IMP TEMPLATE......................................................................................................1-1

CONTEXT FOR I&I MANAGEMENT......................................................................................................1-2 I&I QUANTIFICATION ........................................................................................................................1-2 I&I SOURCES ..................................................................................................................................1-3 ACTION AND IMPLEMENTATION .........................................................................................................1-3 BENCHMARKING AND VALIDATION.....................................................................................................1-4

2. CONTEXT FOR I&I MANAGEMENT ................................................................2-1 2.1 OVERVIEW ......................................................................................................................................2-1 2.2 BACKGROUND STUDIES AND REPORTS ............................................................................................2-1

SEWER CONDITION REPORTING TEMPLATE STANDARD .....................................................................2-1 I&I ENVELOPE METHODOLOGY.........................................................................................................2-2 STUDY OF EFFECTIVENESS OF I&I REDUCTION MEASURES................................................................2-2 PRIVATE SEWER LATERAL REHABILITATION ......................................................................................2-2 I&I RELATIVE TO CATCHMENT AGE ...................................................................................................2-3

3. I&I QUANTIFICATION ......................................................................................3-1 3.1 INTRODUCTION ................................................................................................................................3-1 3.2 ROLES ............................................................................................................................................3-1

FLOW MONITORING/ANALYSIS ROLES FOR METRO VANCOUVER ........................................................3-1 FLOW MONITORING/ANALYSIS ROLES FOR MUNICIPALITIES ...............................................................3-2

3.3 KEY ISSUES ....................................................................................................................................3-2 3.4 GUIDING PRINCIPLES.......................................................................................................................3-3 3.5 METHODS .......................................................................................................................................3-3

DOCUMENTING FLOW MONITORING IN THE I&IMP .............................................................................3-3 FLOW MONITORING CATCHMENT SELECTION ....................................................................................3-4 FLOW MONITORING SITE SELECTION................................................................................................3-4 FLOW MONITORING TECHNOLOGY SELECTION ..................................................................................3-4 FIELD WORK: MUNICIPAL/REGIONAL CREWS AND CONTRACTORS......................................................3-5 QA/QC PROCEDURES .....................................................................................................................3-5 ANALYZING THE DATA: I&I ENVELOPE METHODOLOGY ......................................................................3-6 I&I – CATCHMENT AGE RELATIONSHIPS............................................................................................3-7

4. SOURCES OF I&I .............................................................................................4-1 4.1 ROLES ............................................................................................................................................4-1 4.2 KEY ISSUES ....................................................................................................................................4-1 4.3 GUIDING PRINCIPLES.......................................................................................................................4-2 4.4 METHODS .......................................................................................................................................4-3

I&I AGE CURVE ...............................................................................................................................4-4 RDII HYDROGRAPH ANALYSIS..........................................................................................................4-5 I&I FIELD INVESTIGATION TECHNIQUES.............................................................................................4-6 HYDROLOGIC MODELLING ................................................................................................................4-8

5. ACTION AND IMPLEMENTATION...................................................................5-1 5.1 INTRODUCTION ................................................................................................................................5-1

GOAL-BASED VS. PRESCRIPTIVE PLANS ...........................................................................................5-1 5.2 ROLES ............................................................................................................................................5-1 5.3 KEY ISSUES ....................................................................................................................................5-3

INFLOW AND INFILTRATION MANAGEMENT PLAN TEMPLATE WORKING DRAFT JANUARY 2011

KERR WOOD LEIDAL ASSOCIATES LTD.

Consulting Engineers 251.242

METRO VANCOUVER

5.4 GUIDING PRINCIPLES.......................................................................................................................5-4 5.5 METHODS .......................................................................................................................................5-4

IDENTIFY GOAL-BASED VS. PRESCRIPTIVE PROGRAM........................................................................5-4 GOAL-BASED ACTION AND IMPLEMENTATION ....................................................................................5-5 PRESCRIPTIVE ACTION AND IMPLEMENTATION...................................................................................5-6 ACTION AND IMPLEMENTATION PROGRAM COMPONENTS ...................................................................5-6

6. MONITORING AND VERIFICATION ................................................................6-1 6.1 ROLES ............................................................................................................................................6-1 6.2 METHODS .......................................................................................................................................6-1

7. REPORT SUBMISSION....................................................................................7-1 7.1 REPORT SUBMISSION ......................................................................................................................7-1

FIGURES

Figure 3-1: Typical Sewer Flow Monitoring Data Plot ..........................................................................3-1 Figure 3-2: Flow Hydrograph Showing DWF, RDII and Total Flow .....................................................3-6 Figure 3-3: Typical Relationship Between 24-Hr RDII and 24-Hr Rainfall ..........................................3-7 Figure 3-4: Example of an I&I Rate – Catchment Age Relationship ...................................................3-8 Figure 4-1: Example of an I&I-Age Curve as Tool for Identifying Abnormal I&I ................................4-4 Figure 4-2: Example of an RDII Envelope ..............................................................................................4-6 Figure 4-3: Example of Smoke Test Data Geocoded and Overlaid with Sewer System...................4-7 Figure 5-1: Example of Selection of a Sanitary Catchment for I&I Rehabilitation.............................5-7


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TABLES

Table 4-1: I&I Components and Points-of-Entry ...................................................................................4-3 Table 4-2: Summary of I&I Source Identification Methods ..................................................................4-3 Table 5-1: Rehabilitation Work Targeting I&I Sources .........................................................................5-6

APPENDICES

Appendix A: Flow Monitoring Program Development and Data Analysis Appendix B: Flow Monitoring Contract Guidelines Appendix C: QA/QC for Flow Monitoring Data Appendix D: I&I Envelope Methodology Appendix E: I&I – Age Relationship WEF paper Appendix F: Description of Rehabilitation Technologies

Section 1

Executive Summary


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KERR WOOD LEIDAL ASSOCIATES LTD. 1-1 Consulting Engineers 251.242

METRO VANCOUVER

1. EXECUTIVE SUMMARY

1.1 BACKGROUND

The Greater Vancouver Sewerage & Drainage District (GVS&DD) of Metro Vancouver serves a population of approximately 2.2 million and is responsible for the conveyance of municipally collected sewage and for the treatment of the collected liquid wastes at its five wastewater treatment plants. The GVS&DD and its members are regulated by the BC Ministry of Environment under the Environmental Management Act through an approved Liquid Waste Management Plan. The new Liquid Waste Management Plan, titled Integrated Liquid Waste and Resource

Management (ILWRM), was adopted by the GVS&DD Board on May 21, 2010 and has been submitted to the Minister of Environment for approval. This plan applies to the GVS&DD and its member municipalities. A key strategy in the plan is the reduction of wet weather sewer overflows through regional and municipal asset management, co-ordinated planning, combined sewer separation and wet weather treatment and storage. To implement this plan, several actions have been required to reduce and control inflow and infiltration (I&I) into the sanitary sewer system through ongoing management of whole sewer system: regional, municipal and private, using formalized Inflow and Infiltration Management Plans (I&IMPs). This I&IMP template has developed with the intent to guide GVS&DD and its member municipalities in the preparation of I&IMPs as identified by ILWRM Actions 1.1.8 and 1.1.18. ILWRM Action 1.1.8

Metro Vancouver will develop and implement inflow and infiltration management plans that identify reduction strategies and timelines to ensure wet weather inflow and infiltration are within targeted levels (2012).

ILWRM Action 1.1.18

Municipalities will develop and implement inflow and infiltration management plans, using the Metro Vancouver template as a guide, to ensure wet weather inflow and infiltration volumes are within Metro Vancouver’s allowances as measured at Metro Vancouver’s flow metering stations ( by 2012).

1.2 OVERVIEW OF I&IMP TEMPLATE

The contents of the template are organized in an order that addresses the following questions: � Why are we doing this? (Context for I&I Management)

� How much I&I do we have? (I&I Quantification)


1-2 KERR WOOD LEIDAL ASSOCIATES LTD.


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� Where is our I&I coming from? (Sources of I&I)

� What will we do to reduce I&I? (Action and Implementation Plan)

� How did we do? (Follow-up Monitoring and Verification) An I&IMP template document is included as Schedule A. It is intended that Municipalities use the form of Schedule A to develop their own I&IMPs, referring to this report as a guide. The plan and this report are organized in sections as identified by the following subheadings.

CONTEXT FOR I&I MANAGEMENT

The Context for I&I Management section summarizes findings from previous studies and presents a rationale for whole system management: private lateral, municipal collector, and regional trunk sewers. The ILWRM identifies I&IMPs as part of broader asset management plans that will support sanitary sewer overflow reduction strategies.

I&I QUANTIFICATION

I&I quantification begins with accurate, reliable, and repeatable sewer flow data. Measurement of the success of repair and rehabilitation programs and initiation of capital projects is often tied to this data, so Metro Vancouver and Member Municipalities should place a high value on this resource. There are opportunities to share responsibility for collection and analysis of sanitary sewer flow data between Metro Vancouver and the member Municipalities. It is envisioned that the main role of Metro Vancouver is to build, operate, and maintain a network of wet-weather meter stations. In most cases this network already exists, although some upgrades and/or new stations are required. This network (in the context of I&I) could provide each municipality with the data and a transparent analysis of their overall I&I rates. The goal of flow monitoring conducted by and within the Member Municipalities is thus to focus on discretization of that global (I&I rate) into smaller, discrete catchments. This information is crucial in assisting with prioritizing repair and rehabilitation efforts within the municipality, and quantifying the success of such efforts. Analysis of the data must use consistent, repeatable methods that are accurately applied. Two methods for this analysis are summarized in the text of this template and described in detail in appendix material. The I&I Envelope Method is relatively easy to apply to collected data and provides a means for normalizing I&I results measured both within a Municipality and across the wider Metro Vancouver area. This method was introduced to Metro Vancouver in the


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Sewer Condition Reporting Template Standard, (DRAFT Sept. 2002). It is adopted in various regions throughout North America and is still recommended, with some modifications, for use by Metro Vancouver. The Catchment Age Relationship is a newer concept which relates I&I rates to the average age of the pipes within a catchment. This method can assist in highlighting areas that are not behaving “normally” for their age. The goal of this template section is to provide the reader with the knowledge needed to plan and execute a flow monitoring program with subsequent analysis for I&I values, regardless of whether the work is conducted in-house or by qualified contractors and consultants.

I&I SOURCES

I&I sources change both spatially and temporally, depending upon a range of local conditions including soils, pipe condition, materials and construction practices, storm drainage and presence of cross-connections, age of systems and climatic conditions. Isolation of individual flow components and points of origin is an ideal goal (to guide rehabilitation programs). Techniques to characterize the components of I&I include deriving an I&I-Age relationship, RDII Hydrograph Analysis, Field Investigations, and Hydrologic Modelling. Direction for application of each of these techniques is provided. A linkage between specific field investigation techniques and observed flow data is made to assist with characterizing I&I components. The intent is to provide direction for specific rehabilitation techniques.

ACTION AND IMPLEMENTATION

This section of the I&I Management Plan Template provides a summary of actions a municipality may proceed with in order to achieve I&I reduction based on the completion of I&I quantification and characterization. The objective of the action plan is to identify repair or replacement works, help establish priorities for rehabilitation, and meet I&I reduction targets. There are two approaches for Metro Vancouver and its member municipalities to choose from in preparation of their respective I&IMPs: (A) Prescriptive or (B) Goal-based. (A) A Goal-based approach seeks to achieve a specified I&I target (e.g. 11,200 L/ha/d city-wide, or 20,000 L/ha/d in a particular catchment). Flow monitoring is used to measure the effectiveness of the work performed, and incremental (e.g. Tier 1, Tier 2, Tier 3) work programs may be applied successively until the target is achieved. Where




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targets are below 20,000 L/ha/d, it is likely that the plan will require a private lateral rehabilitation component (B) A Prescriptive approach applies best practices based on available assessment data to reduce or maintain I&I rates, but differs from the Goal-Based approach in that the work plan is not iterative, and no specific I&I rate is targeted at the outcome of the work. Measurement of the success of the work (through post-rehabilitation flow monitoring) is still recommended to determine program effectiveness and refine cost-benefit analyses. The Prescriptive approach allows municipalities to remediate sewer systems by following a prescribed rehabilitation program and allows annual expenditure certainty. It is recommended that Prescriptive plans be adopted where I&I targets are currently being met. It is recommended that Goal-Based plans be adopted where I&I targets are being exceeded, or where capacity concerns warrant aggressive I&I reduction (e.g. overflows or capacity is limiting development). Program Components described in the template include Infrastructure Rehabilitation, Prioritization of Rehabilitation Works, Private Lateral Programs, Public Education, Municipal Bylaws, Preventative Measures (such as specifications and design standards), and a Funding Plan.

BENCHMARKING AND VALIDATION

The ILWRM requires that Metro Vancouver review progress in reducing I&I every four years. Municipalities should update their I&IMPs on the same timeline. Furthermore, every two years municipalities will summarize and forward to the Metro Vancouver a biennial LWMP progress report that includes, but is not limited to: � The extent of new sewer construction and sewer repair and replacement work over

the past two years; and

� A summary of the results of all flow monitoring work undertaken as part of the sewer system evaluation program.

It is anticipated that the I&I–Age relationship established for each individual municipality will change over time, as sewers age and deteriorate, or as rehabilitation works are performed and construction standards / technologies improve, or as climate change alters rainfall patterns. Nevertheless, the relationship remains a useful benchmarking tool both within a municipality and regionally. A need exists for a central or regional repository for the I&I-Age curves so that they may be shared for mutual benefit.

Section 2

Context for I&I Management


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2. CONTEXT FOR I&I MANAGEMENT

2.1 OVERVIEW

Uncontrolled I&I in sanitary sewer systems can have detrimental effects on social, economic, and environmental aspects of urban areas. Excessive flows as a result of I&I can result in health risks associated with sanitary overflows, increase operation and maintenance costs, and may limit capacity otherwise reserved in the existing sanitary sewer system to serve future populations. As I&I becomes a significant component of sanitary flow, it may be cost-effective to reduce I&I rather than upgrade infrastructure to convey additional flows. The literature shows that success reducing I&I has been mixed, and that a well-planned I&I management plan is required to achieve satisfactory I&I control with the limited infrastructure funds available. Traditionally, most I&I reduction efforts have been targeted at rehabilitating public-owned sewer infrastructure. Dealing with private service laterals for I&I reduction now occupies a sizable space at most international sewer collection system conferences. To achieve an effective I&I reduction, it is becoming recognized that a complete and holistic approach to managing the entire sanitary sewer system (regional trunk sewers, municipal collectors, and private laterals) is necessary. Expanding programs to include service laterals is now gaining momentum throughout North America as many cities are arriving at the same conclusion.

2.2 BACKGROUND STUDIES AND REPORTS

SEWER CONDITION REPORTING TEMPLATE STANDARD

In response to 2002 Liquid Waste Management Plan commitments C19 and C23, a common reporting standard1 for Metro Vancouver member municipalities was developed. The reporting standard ensures that biennial LWMP progress reports submitted by the member municipalities are consistent. The 2010 ILWRM extends the biennial reporting requirement, and the Sewer Condition Reporting Template Standard continues to be a tool used by municipalities to report their infrastructure management progress.

1 Sewer Condition Reporting Template Standard, Working Draft Reporting, Nov 2002. KWL and Earth Tech




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I&I ENVELOPE METHODOLOGY

The I&I Envelope method was identified in the Sewer Condition Reporting Template Standard (2002) as an economical and practical method of standardizing I&I analysis in Metro Vancouver. It is a graphical method based on a summary of rainfall and sewer flow data from flow monitoring. By plotting these results, a relationship between rainfall and rainfall-dependent I&I (RDI&I) can be developed. It is then possible to develop ‘return-period’ design values for RDI&I, based on the rainfall analysis. The I&I Envelope method is relatively easy to apply to collected data and provides a means for normalizing I&I results measured both within a municipality and across the wider Metro Vancouver area.

STUDY OF EFFECTIVENESS OF I&I REDUCTION MEASURES

A 2008 study2 for Metro Vancouver looked at two subjects: the work conducted to reduce I&I upstream of two historic SSO locations, and the effectiveness of various I&I reduction measures employed across North America. The study found the highest reductions have been achieved where the entire system was rehabilitated. The next highest I&I reductions were noted where the private laterals were rehabilitated.

PRIVATE SEWER LATERAL REHABILITATION

A 2007 study by Metro Vancouver3 explores governance issues and strategies used by communities across North America to tackle I&I problems associated with private sewer laterals. The 2008 Sheltair report4 provides a synopsis of the range of private lateral I&I reduction programs that have been carried out in other jurisdictions, analyzes these options within the context of the Metro Vancouver regulatory environment, and provides recommendations / pathways for moving forward.

2 Study of Effectiveness of I&I Reduction Measures, Final Report, July 2008, KWL

3 Private Sewer Laterals: A Summary of Governance Issues and Strategies to Address Infiltration and Inflow, GVRD, August 2007

4 Private Sewer Lateral Programs: A Study of Approaches and Legal Authority for Metro Vancouver Municipalities. Final Report,

December 2008, The Sheltair Group


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I&I RELATIVE TO CATCHMENT AGE

Studies have shown that I&I tends to increase as a sewer system ages. A relationship between sewer catchment ages and I&I rates can be developed to demonstrate, on average, how I&I rates in a typical catchment will change over time. This relationship is a useful tool to identify practical I&I reduction targets as part of broader I&I management practices.

Section 3

I&I Quantification


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3. I&I QUANTIFICATION

3.1 INTRODUCTION

I&I quantification begins with accurate, reliable, and repeatable sewer flow data. “Flow data” is defined as continuously recorded, electronic, time-series sewer flow. Depending on the metering technology, other parameters including level and velocity may also be recorded at the same time. Figure 3-1 shows a sample of typical sewer flow monitoring data plotted along with rainfall data.

Figure 3-1: Typical Sewer Flow Monitoring Data Plot

3.2 ROLES

There are opportunities to share responsibility for collection and analysis of sanitary sewer flow data between Metro Vancouver and the member Municipalities.

FLOW MONITORING/ANALYSIS ROLES FOR METRO VANCOUVER

A need exists to build, operate, and maintain a network of wet-weather meter stations. In most cases this network already exists, although some upgrades and/or new stations are required. The goal of this network (in the context of I&I) is to provide each municipality with the data and a transparent analysis of their overall I&I rates. Metro Vancouver is well suited to take on the role of capturing and analyzing the monitoring data.




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One of the benefits of the proposed I&I analysis method (I&I Envelope Method) is that it can be updated as new flow data is acquired with relatively little effort. It is therefore technically feasible to provide yearly updates on global I&I values to each municipality.

FLOW MONITORING/ANALYSIS ROLES FOR MUNICIPALITIES

The goal of flow monitoring conducted by and within the member municipalities is to focus on discretization of the cumulative, system I&I into smaller, discrete catchments. This information is crucial in: � Prioritizing repair and rehabilitation efforts within the municipality;

� Quantifying the success of such efforts. The Metro Vancouver monitoring points will generally not be able to resolve the results of specific individual programs within a municipality, thus it is essential that each municipality conduct their own flow monitoring efforts tied to repair and rehabilitation programs.

3.3 KEY ISSUES

Flow data is of little value if it does not meet the following criteria: � Reliable – much of the analysis technique for I&I relies on successful capture of

significant storm events. A flow meter that works correctly 360 days in a year may not be of use for I&I analysis if the meter fails to work correctly during the other 5 days when crucial storm events occur.

� Accurate – the very nature of open channel sewage monitoring makes good accuracy a challenging goal to achieve. Realistic accuracies in the field can range from 5-10% for a well-calibrated, carefully maintained primary device (such as a flume or weir), to 30% or worse for a temporary area-velocity meter installed in difficult conditions. Accuracy is a function of equipment type and condition, site conditions, and field staff techniques.

� Repeatable – flow measurement must be repeatable from year to year, otherwise the net benefits obtained by repair and rehabilitation programs could easily be lost in the inaccuracies caused by using and installing different equipment from season to season.

� Expense – The equipment, training, and maintenance required to produce good data require an investment commensurate with the value of the exercise.


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Without data collected following these criteria, expensive decisions relying on the data may be at risk.

3.4 GUIDING PRINCIPLES

The following principles are suggested when developing flow monitoring and I&I analysis procedures. Quantifying the success of repair/rehabilitation programs and initiation of capital

projects are based on the quality and reliability of sewer flow data. Good quality data

can be achieved by:

� Building, repairing or upgrading the Metro Vancouver metering network where

needed, in order to provide each member municipality with a fair and accurate assessment of their total I&I contributions.

� Conducting field studies and analysis using flow monitoring specialists. And;

Analysis of the data must use consistent, repeatable methods that are accurately applied,

by:

� Committing to a consistent quality control program for source data.

� Adopting a standard method for calculation of I&I values.

3.5 METHODS

DOCUMENTING FLOW MONITORING IN THE I&IMP

The I&IMP records a municipality’s intended monitoring program and progress to date, and as such identifies: � All discrete flow monitoring catchments in the municipality/region; � History and results of previous monitoring; and � Time frame for monitoring all catchments, with known monitoring priorities stated.

The I&IMP should also contain an I&I vs. catchment age graph, as outlined in detail later in this section, to present the current conditions of the catchments and show potential candidates for rehabilitation or repair.




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Methods for designing and conducting a flow monitoring program, and subsequent analysis of the data, are described in detail in Appendix A. The following material is a summary of the key points from that material.

FLOW MONITORING CATCHMENT SELECTION

Selecting which catchments to monitor is a balancing act between the need for data and budget restrictions. Numerous factors are considered when designing a flow monitoring program, including: � Characterizing catchments by factors such as pipe age, material, soil conditions, and

land use;

� Selecting suitably sized areas for measurement;

� Prioritizing monitoring programs based on expected areas of development and existing planned programs; and

� Looking for opportunities to share the data with other users that could benefit.

FLOW MONITORING SITE SELECTION

Sometimes what seems like a simple exercise on paper turns into something quite different once manhole locations are inspected for potential monitoring sites. Select sites that have: � Easy access or reasonable traffic control requirements; and

� Good hydraulic conditions allowing accurate measurement. Be aware of possible pitfalls such as: � Undocumented sewer laterals; and

� Manholes that simply do not exist or were paved over.

FLOW MONITORING TECHNOLOGY SELECTION

Technology to monitor sewer flows varies widely in cost, accuracy, and suitability for a given condition. Some of the more common types used include: � Area-velocity (AV) meters – relatively inexpensive to deploy but intrusive and with

less accuracy than other systems;


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� Flumes and Weirs – better accuracy but intrusive and can cause deposition or grease issues in some locations;

� Radar velocity meters – non-intrusive with good accuracy but expensive; and

� Acoustic Doppler Profilers – very good accuracy but intrusive and expensive.

FIELD WORK: MUNICIPAL/REGIONAL CREWS AND CONTRACTORS

Many factors weigh into the decision to use municipal/regional staff, contractors, or a blend of both to implement the field portion of the flow monitoring program: � Best results will come from continuously dedicated staff (a minimum of two are

required to satisfy confined space entry requirements), who will benefit from and maintain their skills through ongoing practise and training;

� Significant investment is needed in flow monitoring and support equipment, including vehicles, confined space entry equipment, field computers and a variety of flow monitoring gear to meet onsite requirements;

� Costs of ongoing repair and replacement of equipment;

� Maintenance of safety programs and permits to satisfy WorkSafeBC requirements;

� Costs for training programs for confined space entry and flow monitoring concepts; and

� Occupational health and safety workplace requirements (e.g. medical vaccinations for those who work in and around the sewer sites).

The alternate to in-house staff is to hire a dedicated flow monitoring services contractor. Guidelines on hiring and using their services are provided in detail in Appendix B.

QA/QC PROCEDURES

Quality control and assurance of the sewage flow data is essential, but may be overlooked. Assumptions may be made by contractors that “the engineers will check it”, and engineers may assume the same of the contractors. Responsibility for this important task must be clearly defined during the planning and hiring stages. A set of QA/QC guidelines is provided in Appendix C for reviewing flow monitoring data. These guidelines are meant to help prevent of some of the most common problems that occur before they can have serious impact on the I&I analysis.




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ANALYZING THE DATA: I&I ENVELOPE METHODOLOGY

The I&I Envelope Method was first introduced to Metro Vancouver in the Sewer

Condition Reporting Template Standard, (DRAFT Sept. 2002). With various modifications it is used by many agencies and consultants throughout Canada and the United States to assess the magnitude of I&I using data from a flow monitoring program. While not as detailed as other methods that use computer modelling, it benefits from being relatively simple (i.e. inexpensive), and transparent to use. With a few modifications from the 2002 version, the Envelope Method is applicable for use by Metro Vancouver and member municipalities. A detailed discussion on how to perform this analysis is provided in Appendix D. The purpose of the I&I Envelope Method is to use a collection of recorded storm events to create a correlation between the amount of rain that falls in a catchment and the amount of I&I that shows up at the flow monitoring site. Knowing the return period of the rainfall, combined with the assumption that rainfall return period correlates to I&I return, allows the correlation to be used to produce estimates for return period based I&I. This allows catchments that were monitored in different seasons with different storm events to be compared on an “apples to apples” basis. Figure 3-2 shows the breakdown of a storm into the dry weather flow (DWF), rainfall dependent I&I (RDI&I) and total flow components.

Figure 3-2: Flow Hydrograph Showing DWF, RDII and Total Flow


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With enough storms analyzed and plotted, Figure 3-3 shows the correlation developed for a typical site, correlating rainfall (and return period) with 24-Hour RDI&I.

Figure 3-3: Typical Relationship Between 24-Hr RDII and 24-Hr Rainfall

In the above figure, the value for the 5-Year, 24-Hour RDI&I can be read directly off the graph as 45 L/s. The flow rate can then be normalized using catchment area, converting L/s into L/ha/day. Area-weighted I&I rates can be directly compared against other catchments, and also against targets and guidelines as set out by Metro Vancouver.

I&I – CATCHMENT AGE RELATIONSHIPS

I&I – Catchment Age Relationships can be derived from multiple I&I analyses. The calculated I&I total for each catchment can be plotted on the Y-axis of a graph. On the X-axis, the average age of the catchment (determined by a pipe length-weighted average using a GIS calculation) is plotted. With enough catchments plotted, a curve fit through the data can represent the average I&I response for all of the catchments considered within the dataset. The catchments could include just those from a specific municipality, or, where rainfall and soil conditions are similar there could be benefit in combining and comparing data from multiple municipalities as well. The intent of this graph is to show catchments that have excessive I&I response for their age, relative to other catchments in the data set. There are several opportunities to use this type of analysis when planning and assessing the success of infrastructure rehabilitation efforts, as well as identifying potential candidates for such programs.




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Another potential use for this method is as a predictor for how infrastructure will decay (and hence how I&I will increase) as the catchments grow older. The following figure is excerpted from a paper that was submitted to Water Environment Federation in 2005 on the topic. A copy of this paper is provided in Appendix E. Important note: the procedure described in the WEF paper analyzes 100-year return

peak one-hour RDI&I and uses I&I envelope methodology that differs to the

recommended procedure for Metro Vancouver municipalities. The paper is included in

the appendix for context only. Analysis of Metro Vancouver data should be based on

5-year return, peak 24-hour RDI&I for regional reporting, using the I&I envelope

methodology described in Section 3.2 and Appendix D.

SANITARY SEWER AGE VERSUS RAINFALL-DEPENDENT I&I RATE

5 to 40 Year Age-of-Sewer

Relationship Using Only Data up to 40 Years

y = 542x + 12,418

R2 = 0.4177

Relationship Using All Data

y = 12355e0.0325x

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

0 10 20 30 40 50 60 70 80 90 100

Age (years)

Peak 1

-ho

ur,

100-y

ear

RD

I&I

(L/H

a/d

)

Areas Less than 40-Years Areas Greater Than 40-Years

Figure 4

Figure 3-4: Example of an I&I Rate – Catchment Age Relationship

Section 4

Sources of I&I


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4. SOURCES OF I&I

4.1 ROLES

It is estimated by Metro Vancouver that the length of installed linear sanitary infrastructure is +/- 15,350km. This infrastructure is distributed as follows: � Metro Vancouver 2.9% � Municipalities: 41.7% � Connections to Private Homes: 55.4% Key roles in determining the sources of I&I include: � Metro Vancouver: Facilitates regional benchmarking of I&I sources, and sets

regional targets to protect trunk sewers, WWTPs, and to minimize SSOs.

� Member Municipalities: Has the largest role to play, in that I&I source identification is generally carried out through asset management and detailed I&I investigations leading into I&I reduction work; and

� Private Property: where Municipalities are conducting I&I investigations, most sewer bylaws require residents and business owners to allow access to private property for inspections.

Generally, roles in determining sources of I&I are dependent upon the nature of the I&I investigation being conducted. Currently, regular inspection and maintenance is performed only on collector and trunk sewers that account for only 45% of the sewer system. The remaining 55% of the system – the small diameter sewer connections – have not been assessed, reconditioned or replaced except in small number of pilot projects or after failure.

4.2 KEY ISSUES

I&I sources change both spatially and temporally, depending upon a range of local conditions including soils, pipe condition, materials and construction practices, storm drainage and presence of cross-connections, age of systems and climatic conditions. On a region-wide basis, sources of I&I are not easy to identify. Key Issues identified for determining sources of I&I include: � Relative contributions from Metro Vancouver, member municipalities and private

sewers vary and may not be easily generalized;




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� Identification of the hydrologic components of I&I requires extensive data collection and modelling;

� Access to private property may be required to confirm the presence of stormwater inflow; and

� Identified sources of I&I can often dictate the best approach to I&I reduction.


� Isolation of individual flow components and points of origin is an ideal goal (to guide rehabilitation programs);

� I&I contribution from all system levels (regional, municipal, private) should be understood;

� Reliable and high-quality data is required for determining I&I sources; and,

� Determinations of I&I sources should be verified with independent data, if possible.

HYDROLOGIC COMPONENTS

“Total I&I” is comprised of several flow components, which were introduced in the 2001 Draft Sewer Condition Reporting Template. These are described in the following table.

Component Acronym Calculated As Definition / Explanation

Groundwater Infiltration

GWI Extraneous flow from the ambient long-term water table, not influenced by individual rainfall events

Rainfall-Induced Infiltration

RIIRP

RIIRP-slow

RIIRP-fast

Rainfall that follows a path to the sewer through the soil and/or from short-term, rainfall-based increases in water table elevation. Often occurs in two discernible components, slow and fast.

Snowmelt-Induced Infiltration

SII Snowmelt that follows a path to the sewer through the soil.

Stormwater Inflow SWIRP Rainwater that enters the sewer through direct (non-soil) connections to the runoff surface.

Snowmelt Inflow SMI Snowmelt that runs overland and enters the sewer through direct (non-soil) connections to the surface.

Rainfall-Dependant Inflow & Infiltration

RDI&IRP SWIRP + RIIRP

Total peak rainfall-sourced extraneous flow, averaged over short-terms ranging from 5 minutes to 24 hours depending on catchment characteristics.


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Component Acronym Calculated As Definition / Explanation

Snowmelt-Dependant Inflow & Infiltration

SDI&I SMI + SII

Total peak snowmelt-sourced extraneous flow, averaged over short-terms ranging from 5 minutes to 24 hours depending on catchment characteristics.

RP=Return Period. All of the rainfall-related parameters must be expressed with a return period if they have been derived from flow data or have been estimated with a hydrologic model. It may be appropriate to express the return period as ‘major event’ in some cases.

I&I sources should be understood in terms of these definitions, as they relate to the different parts of the system in which extraneous water can enter the sanitary sewer system. Table 4-2 cross-references the I&I components with the different parts of the sanitary sewer system. Table 4-1: I&I Components and Points-of-Entry

Main Manhole Public Lateral Private Lateral

GWI X X High GW only High GW only

RIIslow (+ SII) X X X X

RIIfast (+ SII) X X X

SWI + SMI X X X

The above cross-reference introduces the possibility of linking specific field investigation techniques with observed flow data to characterize the I&I behaviour of a basin. This can also lead to selection of specific rehabilitation methods to target problematic sources of I&I.

4.4 METHODS

Several methods are available for determining sources of I&I, all of which have different requirements for data and expertise in I&I assessment. The following table provides a brief guideline for determining which methods are appropriate based on availability of data and I&I planning requirements. Table 4-2: Summary of I&I Source Identification Methods

I&I Source Identification

Data / Systems Expertise Required

Results Relative Costs

I&I-Age Curve I&I Rates Catchment Age

Moderate Indicative, not conclusive

Low if data already available

RDII Hydrograph Analysis

RDII Hydrograph I&I Envelope

Moderate Indicative, not conclusive

Low if data already available

Field Investigations

Smoke Testing Dye Testing Air Testing CCTV

Low

Potential points of origin, not conclusive for flows

Moderate to High

Hydrologic Model Collection System Model Hydrologic Model

High

Determines points of origin and flow composition

High




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These methods are discussed below. It is envisioned these methods would be implemented sequentially from least-expensive to most-expensive.

I&I AGE CURVE

The I&I Age Curve can be used to identify catchments with abnormal I&I rates given their age, or as compared with other catchments of a similar nature. In some cases, as shown in the following figure, the ‘outlier’ catchments become obvious.

0

50,000

100,000

150,000

200,000

250,000

0 10 20 30 40 50 60 70 80 90 100

Average Catchment Age (Years)

To

tal I&

I (L

/ha/d

ay)

Monitored Results I&I-Age Curve

Typical I&I

(CRD + Surrey)

Figure 4-1: Example of an I&I-Age Curve as Tool for Identifying Abnormal I&I

The outlier catchments likely have a different I&I profile than the catchments landing nearer or on the line. A catchment significantly above the line at an early age would tend to indicate excessive SWI. In older catchments, it may indicate SWI as well as deteriorating laterals and mainlines. Such catchments can be targeted for smoke testing or lateral inspections to further diagnose I&I sources. If a municipality has several catchments with flow monitoring data, the I&I Age Curve is an inexpensive way to initially determine whether additional investigation to identify I&I sources is required. Catchments ‘behaving their age’ would generally not be targeted for additional investigations outside planned asset management activities. Over time the I&I-Age relationship will change because of changing construction standards, materials, and climate variations. A new relationship could be established at a


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frequency coinciding with infrastructure renewal cycles, climate change intervals or a period of industry adoption of new pipe materials that might be on the order of 10-30 years. More study is proposed to clarify this timeframe.

RDII HYDROGRAPH ANALYSIS

Hydrologic analysis involves examining responses to various rainfall events, and in doing so, paying particular attention to the shape and magnitude of an RDII hydrograph, or the slope of an I&I envelope. I&I components are generally indicated on a hydrograph as follows: � RIIslow – deep groundwater, delayed response to rainfall, attenuated peak occurs up to

several hours after peak rainfall, observed as decay toward the end of an RDII event;

� RIIfast – shallow groundwater, fast response to rainfall, generally only fully developed during saturated conditions; and

� SWI – surface runoff, immediate response to rainfall, presence during dry antecedent conditions can be indicated using I&I envelope.

Hydrologic analysis alone is generally not sufficient to draw conclusions regarding specific sources of I&I, but is most useful for identifying SWI (inflow). SWI sources may be identified by examining RDII responses to storms after long periods of dry weather, in particular, summertime convective storms greater than 10-15 mm in 24 hours. When plotted as an envelope, this will form a ‘lower bound’ line and indicate the amount of SWI present. If compared with total rainfall during the event a rough approximation of cross-connected area can be estimated.




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Figure 4-2: Example of an RDII Envelope

If I&I envelopes have been developed, the necessary data to conduct hydrologic analysis is already present. Reviewing storm drainage practices, soils mapping and any knowledge of ambient groundwater conditions is also helpful. Hydrologic analysis requires the time of someone with sufficient experience to review the RDII responses to rainfall events. Modelling and/or field investigations would generally be required to verify any assumptions derived from the hydrologic analysis.

I&I FIELD INVESTIGATION TECHNIQUES

There are several methods to detect I&I in the field using physical investigation techniques: � Smoke Testing – forcing smoke compound under pressure into sanitary or storm drain

system to identify leaks and cross-connections;

� Dye Testing – used to trace the pathway of water from a known entry point to an exit point;

� Visual – typically with CCTV robotic or push camera;


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� Air Testing – pressurizing isolated sections of sewer to determine whether system is airtight to specified test pressure; and

� Exfiltration Test – filling an isolated section of sewer with a known volume of water, and measuring the drawdown rate.

Smoke and dye testing are most often used to indicate SWI (inflow), while the latter three are indicative of infiltration. Smoke testing is often carried out across basins or entire municipalities, and is relatively inexpensive to complete. Leaks noted during smoke tests should be referenced to addresses, and use a standard description. Once completed, it is most effective to geo-reference the smoke test results by using the address information. This can be cross-referenced against flow monitoring catchments to correlate I&I results with field data, as shown in the following figure. Areas with higher frequencies of leak reports may have higher SWI rates.

Highlighted Catchments havehigh indication of stormwatercross-connections.

Figure 4-3: Example of Smoke Test Data Geocoded and Overlaid with Sewer System

Dye testing is generally used to follow smoke testing, in order to confirm the presence of cross-connections. Dye testing programs can be difficult to conduct on private property, and require the consent of property owners before proceeding. Communications to residents are important prior to initiating smoke and dye testing programs, as these will affect private property. In particular, smoke testing may affect people with respiratory problems if smoke enters buildings, and local fire departments should be notified of smoke testing programs.

Potential Cross-Connection

Sanitary Sewer

Flow Monitoring Catchment




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Air and exfiltration testing are more time-consuming and costly than smoke and dye testing. In particular, exfiltration testing is generally only used when commissioning new sewers as it requires the sewer not be in service during the test. Air testing costs may vary between different types of sewer pipe, for instance, clay pipe will cost up to four times as much as PVC simply because there are more joints to test. CCTV inspections can provide vital clues to the presence of infiltration. Areas with high ratios of connections versus buildings are likely to have abandoned service laterals, which can contribute significant amounts of I&I. Visual assessments are sometimes combined with dye testing to identify abandoned laterals. In order to get reliable information from field investigations, it is important to select a contractor with I&I experience, and have a comprehensive set of specifications when tendering investigation works. In particular, the reporting requirements should include electronic submissions in an electronic database or spreadsheet format to assist in archiving.

HYDROLOGIC MODELLING

A hydrologic computer model can be used to simulate the response of sewer catchments to rainfall. Once calibrated using flow monitoring data, the models can simulate historical antecedent moisture and rainfall patterns and run design wet-weather events. A ‘design rainfall event’ is usually selected to simulate the typical response of each of the basins. Typically, hydrologic models are complex and require specialist knowledge and significant time to calibrate. Recently, the USEPA developed the public-domain Sanitary Sewer Overflow Analysis and Planning (SSOAP) Toolbox. The SSOAP toolbox uses the synthetic unit hydrograph (SUH) approach for predicting RDII. Specifically, this approach employs the RTK method to characterize the RDII response to a rainfall event. This methodology is currently the only means of characterizing I&I approved by the USEPA. The free SSOAP software is a powerful means to determine the amount of inflow, fast infiltration, slow infiltration and groundwater measured in a sanitary sewer as a percentage of rainfall.

Section 5

Action and Implementation


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5. ACTION AND IMPLEMENTATION

5.1 INTRODUCTION

This section of the I&I management plan provides a summary of actions a municipality intends to proceed with in order to achieve I&I reduction based on the completion of I&I quantification and characterization. The objective of the action plan is to identify repair or replacement works, help establish priorities for rehabilitation, and meet I&I reduction targets. There are two approaches for Metro Vancouver and its member municipalities to choose from in preparation of their respective I&IMPs: Prescriptive or Goal-based.

GOAL-BASED VS. PRESCRIPTIVE PLANS

A Goal-based approach seeks to achieve a specified I&I target (e.g. 11,200 L/ha/d city-wide, or 20,000 L/ha/d in a particular catchment). Flow monitoring is used to measure the effectiveness of the work performed, and incremental (e.g. Tier 1, Tier 2, Tier 3) work programs may be applied successively until the target is achieved. Where targets are below 20,000 L/ha/d, it is likely that the plan will require a private lateral rehabilitation component. A Prescriptive approach applies best practices based on available assessment data to reduce or maintain I&I rates, but differs from the Goal-Based approach in that the work plan is not iterative, and no specific I&I rate is targeted at the outcome of the work. Measurement of the success of the work (through post-rehabilitation flow monitoring) is still recommended to determine program effectiveness and refine cost-benefit analyses. The Prescriptive approach allows municipalities to remediate sewer systems by following a prescribed rehabilitation program and allows annual expenditure certainty. It is recommended that Prescriptive plans be adopted where I&I targets are currently being met. It is recommended that Goal-Based plans be adopted where I&I targets are being exceeded, or where capacity concerns warrant aggressive I&I reduction (e.g. overflows or capacity is limiting development).

5.2 ROLES

The role of Metro Vancouver is to: � Maintain regional conveyance infrastructure.




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In addition, selected Metro Vancouver roles from the ILWRM that apply to this IIMPT include: � Work with the real estate industry and their regulators, and the municipalities to

develop and implement a process for the inspection and certification of private sewer laterals being in good condition as a required component of real estate transactions within Metro Vancouver (ILWRM 1.1.7 - 2011action)

� Develop and implement inflow and infiltration management plans that identify reduction strategies and timelines to ensure wet weather inflow and infiltration are within targeted levels. (ILWRM 1.1.8 - 2012 action)

� Work with municipalities to review historical data and adjust as necessary the average inflow and infiltration allowance for regional trunk sewers and wastewater treatment plants, and develop associated target allowances for municipal sewer catchments associated with a 1:5 year return frequency storm event for sanitary sewers to a level that ensures environmental and economic sustainability. (ILWRM 1.1.9 - 2013 action)

� Review progress in reducing inflow and infiltration every four years. (ILWRM 1.1.10 - action every 4 years)

� Enhance enforcement of sewer use bylaw prohibition against the unauthorized discharge of rainwater and groundwater to sanitary sewers. (ILWRM 1.1.11 - 2010 action)

The role of the Municipalities is to: � Maintain municipal infrastructure (sanitary & drainage);

� Manage infrastructure renewal funding;

� Select appropriate remediation practices; and

� Enact appropriate bylaws for control of private lateral I&I. In addition, the ILWRM requires municipalities to: � Develop and implement inflow and infiltration management plans, using the Metro

Vancouver template as a guide, to ensure wet weather inflow and infiltration volumes are within Metro Vancouver’s allowances as measured at Metro Vancouver’s flow metering stations (ILWRM 1.1.18 - develop by 2012);

� Enhance enforcement of sewer use bylaw prohibition against the unauthorized discharge of rainwater and groundwater to sanitary sewers. (ILWRM 1.1.19 - 2010 action);


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� Update municipal bylaws to require on-site rainwater management sufficient to meet criteria established in municipal integrated stormwater plans or baseline region-wide criteria. (ILWRM 1.1.20 - 2014 action);

� Biennially produce a progress report on plan implementation for distribution to the Ministry of the Environment that:

(a) summarizes progress from the previous two years on plan implementation for all municipal actions, including the status of performance measures. (ILWRM 3.5.8 – biennial action).

Private property owners play a role by complying with enacted bylaws, being responsible for maintaining private sewer laterals and disconnecting stormwater cross-connections from the sanitary system.

5.3 KEY ISSUES

Based on the LWMP Biennial Report (2010), there were 28 and 41 sanitary sewer overflows (SSOs) recorded at Metro Vancouver’s trunk sewer system in 2008 and 2009, respectively. Metro Vancouver is striving to maintain conveyance capacity in the regional sewer system to reduce incidence of overflows during wet weather. The member municipalities are also faced with SSOs issues. The 2010 LWMP Biennial Report records a total of 87 SSOs within the municipalities’ sewer collection systems during the 2008-2009 reporting period. Other issues faced by the municipalities include: � Legality framework regarding access and liability exposure for damages due to work

on private property; � Quality control of new sewer installation and repair;

� Funding; and

� Prioritizing remediation. For private homeowners, financial burden incurred as a result of repair or inspection of private laterals is a primary concern. Quality of service for lateral repairs and access to qualified contractors is also a key issue.




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When developing the Action and Implementation section of the I&IMP, the following Guiding Principles can be considered:

Metro Vancouver

� Minimize the occurrence of SSOs.

� Delay or eliminate the need for capacity upgrade of conveyance and treatment facilities due to I&I.

� Reduce or eliminate the need for on-site storage/treatment of SSOs through I&I reduction.

Municipalities

� Minimize the occurrence of SSOs.

� Reduce or eliminate the need for on-site storage/treatment of SSOs through I&I reduction.

� Design a program to meet ILWRM/Metro Vancouver targets.

� Clearly define responsibility for removing I&I from municipal sewers and private sewer laterals.

� Develop a cost effective program.

� Ensure there are enforceable legal means for actions/methods.

� Employ actions/methods that are measurable.

� Promote public acceptance of the I&I Management Plan.

5.5 METHODS

IDENTIFY GOAL-BASED VS. PRESCRIPTIVE PROGRAM

The initial step required to determine the proper course of action is differentiating between the need for a Goal-Based or Prescriptive Program. This decision can be made at two levels – City-wide, and at the catchment level. If a municipality is not achieving the Metro Vancouver target for I&I city-wide, a Goal-Based approach is recommended. If the city-wide target is being met, a Prescriptive


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approach is appropriate, however, special conditions may dictate a Goal-Based program at the catchment level. These conditions could include: � Sanitary sewer overflows in a catchment;

� Reduced conveyance capacity limiting development;

� Excessive pumping/energy costs; or,

� An I&I response that greatly exceeds the measured rates in other catchments with

similar characteristics (i.e. above the municipality’s Age-I&I rate relationship).

GOAL-BASED ACTION AND IMPLEMENTATION

Recommended components of a Goal-Based plan include: � Flow monitoring to identify I&I rates in all catchments greater than 20 ha within 20

years (at a minimum, a 10-year cycle is recommended where targets are greatly exceeded).

� CCTV inspection of all linear sewer assets on a maximum 20-year cycle (more frequent for assets in poor condition).

� Tracking of I&I rates using the I&I-Age relationship.

� In catchments not achieving the target I&I rate, characterization of I&I components through hydrologic modeling or field programs.

� Incremental, targeted I&I reduction including one or more of the following: - “Tier 1” rehabilitation (mainline and lateral interface repairs); - “Tier 2” rehabilitation (public lateral repair/replacement); - “Tier 3” rehabilitation (private lateral repair/replacement); - Private lateral evaluation or certification and repair/replacement; - Inflow reduction (manhole repair, cross-connection elimination); and

- Targeted infiltration reduction (service lateral repair, manhole repair, abandoned lateral elimination, mainline repair/replacement).

� Iterative follow-up flow monitoring (to determine program effectiveness and to

evaluate next rehabilitation steps) and successive rehabilitation works until target is achieved.

A Goal-Based program seeks to reduce I&I to a target level, and the success of the program can be quantified by the L/s reduction in I&I. For city-wide programs, a flow-balance can be calculated to determine the required reduction overall, and progress can be tracked catchment by catchment.




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PRESCRIPTIVE ACTION AND IMPLEMENTATION

Recommended components of a Prescriptive Plan include: � Flow monitoring to identify I&I rates in all catchments greater than 20ha within 20-

years;

� CCTV inspection of all linear sewer assets on a maximum 20-year cycle (more frequent for assets in poor condition);

� Tracking of I&I rates using the I&I-Age relationship; and

� Where warranted (as per Section 5.5.1), targeted I&I reduction. A Prescriptive program employs responsible management practices to monitor rates and rehabilitate catchments as a preventative measure to maintain compliance with ILWRM/Metro Vancouver targets.

ACTION AND IMPLEMENTATION PROGRAM COMPONENTS

Infrastructure Rehabilitation

The Action and Implementation Program documents intended rehabilitation works as they become evident. I&I reduction achieves the greatest result when rehabilitation works are based on the results of I&I quantification and characterization (and preferably in concert with asset condition assessment). Selection of appropriate sewerage remediation measures will depend on local conditions (soil, groundwater, rainfall) and pipe condition. A brief description of rehabilitation technologies is included in Appendix G. Table 5-1 shows rehabilitation work targeted at removing specific sources of I&I. Table 5-1: Rehabilitation Work Targeting I&I Sources

I&I Source Common Causes Repair Work

SWI - Defective manhole cover - Storm-sanitary cross-connection

- Repair defective manhole - Correct storm-sanitary cross

connection

RII (fast) - Defects at upper portion of manhole - Defective service connections

- Plug abandoned service connections - Repair service lateral - Repair manhole

GWI + RII (slow)

- Defects in sewer mainline (cracks, defective joints, etc)

- Defects at lower portion of manhole - Defects at service lateral-mainline

interface

- Repair sewer mainline - Repair manhole


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A secondary consideration when prioritizing repair work is the cost per work type. Based on average cost per meter of mainline in a rehabilitation basin, cost increases (from $5/m to $1,000 +/m) in the following order:

� Storm-sanitary cross-connection and abandoned service lateral removal; � Pipe lining, grouting, etc, mainline rehabilitation; � Pipe and manhole replacement; and � Service lateral rehab / replacement. It is not recommended that rehabilitation works be selected by cost alone, as this will result in random I&I reduction effectiveness.

Prioritization of Rehabilitation Program

In areas tributary to combined sewer treatment plants, combined sewer overflow plans will take precedence over I&I management because of the potential for vastly greater flow reduction and CSO control relative to the investment required. In separated sewer systems, rather than referring only to the absolute I&I rate, it is suggested that the I&I-Age relationship be used to prioritize rehabilitation works, as demonstrated in Figure 5-1 below.

Figure 5-1: Example of Selection of a Sanitary Catchment for I&I Rehabilitation

The advantage to this is that catchments with I&I rates well above the I&I-Age relationship are likely to yield the greatest reductions. Catchments near the line may still




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exceed the I&I target, but significant I&I reduction is likely to require multiple work types and larger expenditures relative to the amount of I&I reduced. It is recommended that municipalities develop their own I&I-Age relationships to account for local variations (rainfall intensities, soil conditions, construction practices). It is anticipated that the relationship will change over time, as sewers age and deteriorate, or as rehabilitation works are performed and construction standards improve, or as climate change alters rainfall patterns. I&I rehabilitation programs can be integrated with structural repair programs for increased cost-effectiveness. However, local work has shown that a structural program alone commonly results in no I&I reduction.

Private Lateral Rehabilitation Programs

In the two Metro Vancouver municipalities that have experimented with private lateral rehabilitation, a 69% reduction in 5-year, 24-hour I&I was achieved. A public side I&I reduction program in these catchments would never have reduced I&I to a target level associated with a Goal-based program. Where I&I management opportunities on municipal collector sewers have been exhausted or would deliver limited benefit, a private lateral program may be necessary in some jurisdictions. A private lateral program may also be required for catchments with very high groundwater infiltration or with a history of poor lateral sewer construction. The December 2008 Sheltair Private Sewer Lateral Programs study identifies multiple approaches and legal authority for municipalities to implement private lateral rehabilitation programs. The study notes that “Implementing a private sewer lateral program is the responsibility of the individual municipalities; however, a coordinated effort made by all levels of government (federal, provincial, and municipal) will ensure municipalities have the required resources to effectively address the issue of I&I from the private system.” Further work by Metro Vancouver and the member municipalities to establish components of a common private lateral program is recommended in the report.

A summary of possible private lateral rehabilitation approaches identified in the Sheltair report include:

� Incentive-based - Incentive-based programs encourage a targeted activity by offering a reward (e.g. a refund for some or all of the costs involved, reduction in taxes, or reduced sewer rate).

� Regulatory - Enforcement-based programs impose requirements on private property owners to maintain their private sewer laterals in good condition. (e.g. a bylaw requiring replacement of a private lateral when an owner applies for a development permit for work exceeding a value threshold).


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� Municipally-driven - A municipally-driven approach is one in which the municipality conducts the work on private property, as selected by evaluation of need.

Where private lateral programs are considered, the Action and Implementation section of the I&IMP should identify any requirements of the program, and outline the proposed approach.

Public Education for Dealing with I&I Issues

A public education program is recommended both to inform citizens about the consequences of I&I, and to encourage cooperation with I&I reduction programs. Targets of the program are to raise awareness of the causes and consequences of I&I, identify regulatory provisions, convince citizens that the benefits of the program outweigh the costs, and prepare residents for a private lateral program. Alternately, the benefits could be explained in terms of risk management i.e. the benefits of preventing sewer back-up and the potential for costs and damages to home owners if I&I is not managed adequately. Typical methods could include: � Public media announcement; � Rates notice insert; � Local advertising; � Brochures, displays; � Signage at work sites; � Mailout bulletins; and � Website features. A sample Private Sewer Lateral Program brochure is included in the 2008 Sheltair report. The brochure is centered around adoption of a private lateral certification program, but could easily be modified to communicate broader private lateral I&I issues. When developing the action and implementation section of the I&IMP, an organization could include the following: � extent of education program (timeframe, region); � target audience of public education program; � messages to be conveyed; and � media to be used to convey message.

Development of Municipal Bylaws

In British Columbia, the Community Charter (SBC 2003) Chapter 26 provides the basis and the powers for municipalities to develop bylaws to address I&I on private property.




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The 2008 Sheltair Report presents an exhaustive study of bylaw options available to Metro Vancouver municipalities for inspection and repair/replacement of private sewer laterals. A draft bylaw is included that is drawn around inspection and certification of private laterals as a condition of sale, construction, or renovation. Municipalities are encouraged to modify this draft bylaw to suit, or at a minimum to adopt bylaws that grant access and the means to execute repairs such as those enacted by the City of Surrey or the City of Vancouver. Key wording from the City of Surrey Sanitary Sewer Regulation and Charges Bylaw, 2008, No. 16611 includes: “Every owner of real property and every occupier of premises to which a service connection has been installed must allow, suffer and permit the General Manager, Engineering and all associated inspection equipment, to enter into or upon the real property and premises for the purpose of inspecting the premises including building sanitary sewer, drains, fixtures and any other apparatus used with the service connection or plumbing system, as well as to observe, measure, sample and test the quantity and nature of sewage being discharged into the sanitary sewerage

system, to ascertain whether the terms of this Bylaw are being complied with.” “No person may discharge or continue to allow to be discharged into a building sanitary sewer or the sanitary sewerage system any storm water or permit any groundwater infiltration.” I&IMP actions relevant to bylaws include: � review of existing bylaw to determine property access rights for inspection and/or

repair of sanitary sewer laterals; and � intent to draft (and adopt) a bylaw restricting owners from permitting stormwater or

groundwater from entering sanitary sewer laterals.

Preventative Measures

Efforts to prevent I&I occurring in new construction should be ongoing as the I&I reduction program addresses existing I&I sources. Preventative measures may include:

� the use of sound engineering specifications in the design and inspection; � enforcement of specifications and design standards during construction; and � plumbing inspections and certifications can also help prevent I&I.

Funding Plan for I&I Rehabilitation Work

It is recommended that funding for the I&IMP be identified in the Action and Implementation section of the plan. Approaches for determining the level of funding may differ depending on whether the work is Goal-Based or Prescriptive. At a minimum, a funding level could be derived based on the ILWRM commitment to target a 100-year cycle of replacement or rehabilitation of sewerage infrastructure.

Section 6

Monitoring and Verification


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6. MONITORING AND VERIFICATION

6.1 ROLES

Key roles in I&I reduction progress monitoring and verification include: � Metro Vancouver:

� review progress in reducing inflow and infiltration every four years (ILWRM 1.1.10 - every 4 years)

� Member Municipalities:

� Maintain and, if necessary, expand the existing municipal sewer flow and sewer level monitoring network. (ILWRM 3.3.8 - Ongoing)

� Benchmark I&I rates through development of I&I-Age relationship

� Update I&I Management Plan

6.2 METHODS

REVIEW I&I REDUCTION PROGRESS

The ILWRM requires that Metro Vancouver review progress in reducing I&I every four years. Typical activities may include:

� Flow monitoring;

� I&I quantification using I&I Envelope method, taking into account possible expanded

development area; � Comparison of I&I rates with previous historic values (i.e., quantified 4 years ago, or

initial baseline I&I rates); � Determine whether I&I targets are being met; and � Summarize findings and discuss results with municipalities to help update I&IMPs as

necessary. Every two years, municipalities will summarize and forward to the Metro Vancouver a biennial LWMP progress report that includes, but is not limited to:




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� The extent of new sewer construction and sewer repair and replacement work over the past two years; and

� A summary of the results of all flow monitoring work undertaken as part of the sewer

system evaluation program. Where a goal-based approach is adopted for targeted I&I reduction, effectiveness of each phase of the I&I rehabilitation efforts should be quantified using catchment flow monitoring and I&I analysis.

BENCHMARK I&I RATES

It is anticipated that the I&I–Age relationship established for each individual municipality will change over time, as sewers age and deteriorate, or as rehabilitation works are performed and construction standards / technologies improve, or as climate change alters rainfall patterns. Nevertheless, the relationship remains a useful benchmarking tool both within a municipality and regionally. A need exists for a central or regional repository for the I&I-Age curves so that they may be shared for mutual benefit.

UPDATE I&I MANAGEMENT PLANS

As the ILWRM requires that Metro Vancouver review progress in reducing I&I every four years, it is recommended that I&IMPs be updated every four years at a minimum.

Section 7

Report Submission


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7. REPORT SUBMISSION

7.1 REPORT SUBMISSION

Prepared by: KERR WOOD LEIDAL ASSOCIATES LTD.

_______________________________________

Andrew Boyland, P.Eng. Municipal Sewer Sector Leader

Reviewed by:

_______________________________________

Chris Johnston, P.Eng. Vice President

Appendix A

Flow Monitoring Program Development and Data Analysis

INFLOW AND INFILTRATION MANAGEMENT PLAN TEMPLATE DRAFT REPORT JANUARY 2011


APPENDIX A

I&IMP TEMPLATE

1. APPENDIX A – FLOW MONITORING PROGRAM DEVELOPMENT

1.1 INTRODUCTION

The task of laying out a successful flow monitoring program and analyzing the results is complex. The following sections provide guidance on the process, regardless of whether the planning and execution of a flow monitoring program is done entirely in-house, entirely by qualified contractors and consultants, or by a mixture of both.

1.2 CATCHMENT SELECTION

Assume that the goal is to determine discrete I&I values for catchments within your municipal boundaries. 1. Establish a rough budget for the flow monitoring program. As an approximation, use

$2,000/site/month for a full-service flow monitoring contractor to supply data for a site. Consider a 6 month period, from October to March, as the time period for a winter flow monitoring season.

2. Based on your budget, determine the approximate number of sites that can be implemented over the winter season. Your budget may be insufficient for monitoring all of your desired catchments in a given season, but it is useful to have an idea of the number of sites that your organization can afford per year.

3. As a way of addressing budget issues, consider monitoring some catchments as

indicators of conditions in larger areas. For example, if you are faced with a need to monitor four neighbouring catchments (all of which have similar pipe age, material, and soil conditions), consider monitoring just one or two as indicators of likely conditions in the others.

4. Decide on the base mapping to be used for catchment delineation. Access to a GIS database will produce the best results. A suggested mapping scheme is:

• Use an aerial photo with muted colours as the background image, to help you

identify land use and large, unsewered areas such as regional parks; • Colour pipes by type (AC, PVC, etc.) in order to help distinguish areas with

similar pipe material. Alternately or as well, try colouring pipes by their age; • Show manholes in order to assist with locating potential flow monitoring sites; • Overlay subtly coloured contour lines to establish areas with steep grades from

those in low lying or flat areas; • If available, prepare a separate map, replacing the aerial photo with soil type to

distinguish between fast and slow draining areas;



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5. With base mapping in hand, the goal is to establish catchments with similar pipe

materials, age, slopes and soil types. Delineating catchments with these similar characteristics will increase the odds of finding “smoking gun” catchments. Choosing catchments with broadly mixed characteristics will likely just produce “average” I&I results.

6. To a lesser extent, consider land use when delineating catchments. Catchments that mix residential with significant industrial, commercial, or institutional sources can make identifying some components of the I&I difficult, as the dry weather components of the flow are often not as repeatable or predictable as residential areas.

7. Consider catchment size carefully. A good limit for the lower size is 20-30 hectares. While achievable, catchments much smaller than this tend to produce too little flow and have higher solids content. This can result in failure to flush debris from the flow monitoring equipment. Monitoring of a catchment smaller than this requires special equipment and techniques, and should only be used as necessary in specialized pilot projects.

8. On the opposite end of the spectrum, try to keep catchment size under 300 hectares. While there is no hard upper limit to the size of a catchment that can be monitored, eventually the results collected from an excessively large catchment become of little practical value aside from reporting a “total” I&I value (i.e. totals for each municipality). Factors such as travel times, attenuation, difference in rainfall distribution, and non-uniform pipe characteristics will yield little information to guide targeted repair and replacement programs.

9. Be aware of diversion pipes (both intentionally installed and undocumented), which can “move” water from one catchment to another during wet weather events. In such cases it may be necessary to monitor the diversion flow as well as the main outlet flow for a catchment. These monitors must be operated concurrently in order for the results to be conclusive. If you discover a diversion in a catchment which has already been monitored, you should consider re-monitoring the outlet along with the diversion simultaneously for true results to be obtained.

10. When drawing catchment boundaries, do not include large unsewered areas (such as regional parks, industrial areas such as gravel pits or large material storage yards), rail yards, etc. (especially when those areas are on the outside edge of the catchment). These areas do not contribute to I&I and will artificially reduce the stated I&I when expressed as an area-weighted value.

11. It is generally acceptable to leave in smaller neighbourhood parks and school yards in

a catchment. A rule of thumb is that when a catchment is viewed as a whole on the map, it should not include visually “obvious” non-contributing areas.



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12. Use other information such as planned upcoming developments, known replacement programs, and need for computer model calibration data to assist in prioritizing areas to monitor. Could others use the data for model calibration? Will flow estimates for bypass pumping be required during a replacement program? Alternate funding sources may be identified to assist in monitoring costs, which would also allow for the flow monitoring data to serve additional needs beyond I&I measurement.

1.3 TECHNOLOGY SELECTION

When the process of delineating catchments is complete, begin to identify potential manholes for monitoring. A brief understanding of the usual measurement technologies is helpful for this, and can be broadly broken into four categories for temporary monitoring programs. 1. Area-velocity meters – these units are intrusive (a sensor is placed in the flow, usually

at the bottom of the pipe). Different sensors measure the depth and velocity of the sewage, and the meter then calculates the flow rate using the principle of continuity (cross sectional area of water multiplied by velocity equals flow rate). Uses: • Generally works best in shallow grade pipes with uniform flow. Overall the most

economical.

Disadvantages: • Will not work on steep sites with low depth and high velocity. • Should be avoided in pipes above 600mm in diameter as velocity tends to under-

report. • Requires extensive field maintenance, as they are subject to debris fouling.

2. Weir/flume – specially shaped weirs and flume inserts are available for temporary

deployment, having proven fairly reliable at remaining clear of debris. The sensor used is often a downward facing ultrasonic to measure the water level behind the weir. Examples of these types of stations exist in the Lower Mainland that have been running continuously for years with little maintenance. Uses: • Weirs generally work best at steeper slopes (has been used successfully at grades

up to 15%). Shallow slopes are better suited for flumes. • Tends to require less maintenance but with slightly more upfront cost; • Weirs in particular have good low flow resolution.

Disadvantages: • Backwater pool can cause gravel and grease buildup on shallower grade sites; • Requires more extensive installation at each site;



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• Not well suited for sites that surcharge; • Weirs are not suitable for larger diameter pipes such as interceptors where head

loss across the weir would be unacceptably high.

3. Radar Velocity – non-invasive sensors hang in the manhole barrel and shine down on to the water surface to measure level and surface velocity, from which flow is computed.

Uses: • Most pipe grades where ease of maintenance is desired; • Can handle larger diameter pipes;

Disadvantages: • Average velocity measurement is inferred from surface velocity. Requires

calibration with manual site profiling measurements if high accuracy is required; • Limited functionality in surcharge conditions; • Relatively expensive when compared to options 1 and 2.

4. Acoustic Doppler Profiling Meter – invasive sensor that sits at the bottom of the pipe,

similar to an area-velocity meter. High power sensor and acoustic binning allow the unit to handle large diameter pipes and flow asymmetry.

Uses: • Large diameter (up to 6 metres), and/or significant flow asymmetry;

Disadvantages: • Expensive

Choice of equipment is dictated by site conditions, available budget, and equipment availability (either rental or purchase). Ultimately, an experienced flow monitoring specialist should approve the technology selection for each site, based on their experience and professional judgement.

1.4 SITE SELECTION

With catchments delineated, begin to select manholes for each site. Consider the following:

1. Regardless of which technology is used, all flow monitoring sites benefit from a

straight through manhole with no contributing laterals or other disturbances. Always opt for this configuration if available.

2. Avoid manholes with significant bends. It is possible to monitor sharp bends, if

necessary, by using weirs.



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3. Avoid manholes with contributing laterals. It is possible to monitor in these

manholes, if necessary, by using weirs to either include or exclude flow from the lateral.

4. Consider traffic control issues for installation, maintenance, and removal of the equipment. When possible choose a manhole that would not require traffic control to access.

5. In many areas within Metro Vancouver, the municipal collection system flows down a steep grade into the Metro Vancouver sewer, which is often laid at a flat grade. Many of the Metro Vancouver sewers were designed to surcharge, so choose sites that are high enough up the hill to stay out of the surcharge zone of the Metro Vancouver sewer. Look for any evidence of surcharge when doing the field check of each site (toilet paper and other debris hanging from the rungs is a common sign of a manhole that surcharges and should be avoided).

6. Never rely purely on the desktop site selection exercise. Always have a field inspection of each manhole done prior to final selection to ensure that any unforeseen circumstances are avoided prior to site installation. Sites that are particularly dirty or greasy should be power washed and flushed prior to site installation.

7. In many areas locating the manhole can be problematic. Some manholes have been covered over by repaving, while others may be lost in a right of way overgrown with blackberry bushes. In other locations, the manhole may simply never have been built even if it is shown on a GIS system.

8. Be wary of bolted manhole lids. On some systems (especially Metro Vancouver’s), bolted lids are often a sign of a system that surcharges. Other lids may be bolted to eliminate odour complaints, or to prevent metal theft.

1.5 PERSONNEL SELECTION: CONTRACTOR OR IN-HOUSE

Within Metro-Vancouver, there are municipalities that contract out their flow monitoring needs and others that use in-house staff. There are pros and cons to each, and in some cases a mixture of both may be useful. This decision is an individual choice for each municipality based on policy, staffing levels, and available budget. Consider the following when deciding to develop an internal flow monitoring services team: 1. Installing and maintaining sanitary flow monitoring sites is a 2-person job. During

many phases of installation and removal, confined space entry procedures must be followed mandating 2 staff members. Additional crew may be needed if traffic control requirements for the site dictate.



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2. Minimum equipment consisting of a vehicle, confined space entry tripod, blower with generator or invertor for ventilation, harness, traffic signage, and gas detector is required for confined space entry. In addition, each member of the crew should have undergone a confined space entry course and be currently certified as such. Gas detector maintenance must be undertaken and bump tests done daily.

3. Owning and maintaining sewage flow monitoring equipment is an ongoing cost that escalates as time goes on. It is not unusual for sensors to need calibration after every season, typically an ongoing cost that is best handled by shipping the equipment back to the factory for recertification. Loss of equipment due to theft, sewer surcharge, and even rats chewing cables is a common occurrence.

4. Specific staff should be dedicated to the task, otherwise poor quality data will likely the outcome. Ongoing maintenance including battery changes, calibration checks, site documentation, and inspection/cleaning must be undertaken ritually. If this work is being done in-house, timely data QA/QC must also be done by in-house staff to avoid collecting an entire season of poor quality data.

5. Many techniques including onsite calibration checks are best done by well-practised staff, both to ensure accuracy and repeatability of the data. Senior staff should oversee junior staff until satisfied that the knowledge gained through years of experience is passed on.

6. All staff that work around sewers should have Hepatitis A and B vaccinations and

refer to WorkSafe BC for a list of additional health and safety precautions.

7. A rugged laptop is required to program and retrieve data from the flow meters. Even flow monitoring units that use wireless services to send their data to a central server still need initial programming that requires a laptop.

8. Train your staff to recognize and step back from a site or situation that is beyond their abilities, either due to safety concerns or lack of appropriate monitoring equipment. In these cases, it may make more sense to hire a dedicated flow monitoring contractor, to take advantage of their experience and specialized equipment.

9. A current safety plan must be prepared and kept onsite with staff at all times. The safety plan outlines the procedure to be performed, the conditions under which the crew can operate and those under which they must cease operations. A site permit must be filled out ahead of each installation during a tailgate meeting, and the completed documentation kept for auditing purposes.



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CONTRACTOR QUALIFICATIONS

If the decision is made to hire a contractor to perform the flow monitoring services, consider the following: 1. Even if the project is small enough to sole-source, prepare a specification so that the

contractor clearly understands the scope of the work. Important points to cover in the specification include:

a. Table of the site locations, with alternates if the sites have not yet been inspected

for suitability. Clarify if the contractor is permitted to select an alternate site with/without approval;

b. Indication of which technology is suitable with or without approval; c. Period of monitoring; d. Format, method, and frequency of data delivery; e. Required reports; f. Quality control expectations; g. Payment terms relative to percentage of good data.

2. An appendix is provided which contains sample specifications for a typical temporary

flow monitoring program.

3. If tendering the work, ensure an understanding of what each contractor is providing in order to ensure comparable pricing. Some contractors focus on raw data delivery with little or no data manipulation, while others employ dedicated engineers or technologists to “scrub” the raw data into a final product. If the latter is the case, always ensure that the unfiltered raw data is also delivered alongside the final data, along with clear explanations of what was done to the final dataset.

4. Request and check a recent list of references.

5. Verify your insurance requirements against the contractor’s coverage well before the start of the monitoring season. Pay special attention to coverage for accidental and sudden environmental releases, and also to total amounts for comprehensive. Most contractors can obtain extra insurance as needed but this process takes time and additional funds.

6. Review the data in a timely manner, not just for payment purposes but to ensure that problems that occur are rectified early in the monitoring season. Utilize techniques from the next section to assist in your data review.

Appendix B

Flow Monitoring Contract Guidelines

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APPENDIX B - FLOW MONITORING SPECIFICATION

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SPECIFICATIONS

1.1 Scope of Work

.1 The City is undertaking sanitary sewer flow monitoring as part of its sewer assessment and performance program.

.2 The Work to be performed is described as:

o Installation and operation of temporary flow monitoring sites (and associated reporting of sanitary flow) at seven manholes for a period of five-months during the winter of 2010/2011.

o Traffic control per site, as required.

.3 The sites are located within the City, and most are categorized as steep slope, high velocity sites (slopes from 3-15%, with full-pipe velocities from 2-5 m/s). Some sites require monitoring of the combined flow from two laterals. These sites are listed in the table in Section 1.6. The Tenderer shall visit each of the pre-selected sites prior to submitting their Tender.

.4 Pricing is required for the complete set of installations as described above as shown in the Schedule of Prices.

1.2 Schedule

.1 The target date for having the seven temporary winter stations operational is November 1, 2010. The five-month operating period would then be from November 1, 2010 until March 31, 2011.

1.3 Basis for a Contractual Relationship

.1 This document is a "performance specification". Within it, the City has defined what it requires as deliverables. The Contractor has the flexibility and discretion to determine how the Contract deliverables can be most effectively provided within the spirit of the guidelines presented herein.

The Contract includes supply, installation, calibration, and operating of equipment (including data quality assurance) to collect reliable flow data for the operational duration.

1.4 Description of Contract Tasks

.1 The "performance specification" as presented is comprehensive and detailed in describing the contract deliverables. The key points are summarized below to provide an overview of the program requirements:

� Commissioning of Stations: supply, installation and calibration of approved equipment to measure sewer flow for the operational period.

� Station Operation: maintenance and operation of flow monitors for the operational period.

� Flow Data Reporting: monthly reports in approved format of quality-assured data in graphical

(hydrograph) and electronic form to the Engineer (both raw and corrected data to be provided, as well as documentation of calibration procedures).

.2 The Contractor is encouraged to develop innovative and cost-effective ways of providing the deliverables. Approval of methods and equipment by the Engineer is required prior to proceeding with any proposed work.

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1.5 Selection of Monitoring Sites

.1 The Contractor is advised that most sites that will be encountered are steep slope, high velocity conditions (slopes from 2-15%, full-pipe velocities from 2-5 m/s). Some sites require monitoring the combined flow from two laterals. Traditional AV meters are not expected to work in most of the encountered sites. As a result, a limited number of approved technologies will be accepted, as detailed in Section 2.

.2 The City has identified the required monitoring sites based on field investigations and the City’s information needs. Use of alternate manhole locations for pre-selected sites, or selection of new sites, must be approved in writing by the City.

1.6 Existing Field Conditions

.1 Station numbers, manhole numbers, and pipe diameters are listed in the following table:

STATION NAMEMH #

LOCATION DESCRIPTION Slope Pipe Status

Station Name # 1 SM008903Lane east of Street A south of Street B 5.0% 200mm Repeat

Station Name # 2 SM007151Street C at Street D 6.0% 200mm New

Station Name # 3 SM009565Street E. south of Street F

4.0% 200mm New

Station Name # 4 SM006333Avenure A, north of Street G. 9.0% 250mm Repeat

Station Name # 5 SM001504Steet H at Street I 15.0% 375mm Repeat

Station Name # 6 SM007682Street J, N of Highway A

12.0% 300mm Repeat

Station Name # 7 SM003001Street K at Streek L 7.0% 200mm Repeat

.2 Additional site information required to select equipment shall be collected by the Tenderer during a site visit

prior to submitting their Tender. 1.7 Wet Weather Event Response Time

.1 The Contractor will meet the performance specification for site visits during high flow events, local representation is required. Refer to clause 3.3.

PART 2 PRODUCTS 2.1 Flow Measurement Methodologies

.1 Due to the hydraulic conditions in many of the proposed sites, the Contractor may only use and install approved

methodology and equipment for monitoring steep-slope, high velocity sewer flow. This is limited to weirs with elevated weir crests designed to dissipate the excessive velocity head, and to velocity-area meters that are capable of correctly measuring depth under high-velocity conditions. In either case, the Tenderer must demonstrate that they have successfully used the proposed equipment in previous multi-site, steep-slope, high-velocity conditions. The Contractor is required to submit laboratory documentation that the proposed equipment and methodologies are capable of operating under the anticipated range of conditions. Laboratory results shall be submitted in accordance with Section 1.4.

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.2 Pre-Approved equipment is described in Section 2.7.

2.2 Electronic File Formats

.1 Data shall be submitted in monthly comma-separated ASCII files. Tab-separated ASCII files will not be

accepted. .2 File names shall indicate STATION NAME AND MANHOLE NUMBER, month, and year of data contained

within. Files shall contain homogeneous month-long data records, starting at the first day of each month at 00:00:00 and ending on the last day of each month at 23:55:00. File names shall indicate the station identification and the month and year of data contained in each file, and shall be of consistent format from month to month.

.3 Files shall be provided via email to [email protected]

2.3 Time and Date

.1 All times and dates shall be reported in Pacific Standard Time, synchronised to coordinated universal time (1-303-499-7111).

2.4 Data Recording Frequency

.1 All data shall be recorded at an interval of 5 minutes.

2.5 Data Reporting Frequency

.1 All data shall be reported in electronic files at a frequency of 5 minutes, on even 5-minute increments (i.e. 00:05, 00:10, 00:15 etc.).

2.6 Sewer Flow Reports

.1 Monthly reports shall be provided within two weeks of the end of each month.

.2 Each monthly report shall contain the following information:

� Site sketch and installation data sheet � Monthly Data files for each site � Documentation of quality assurance procedures, which may include but is not limited to scatter plots

(for VA meters), manual flow profiling reports, offset tracking narratives, and site maintenance records

� Electronic files as specified containing both raw and corrected data, including correction information and flagging of all suspect data

� Confined space entry reports

2.7 Approved Equipment

.1 Equipment pre-approved is outlined below. Any other equipment proposed is subject to the approval of the Engineer. Approval will not be unreasonably withheld, however the Engineer must be satisfied that the proposed equipment suits the needs of the City. The Contractor assumes responsibility for the appropriate operation of all equipment.

.2 Weirs pre-approved for use in flow monitoring include designs from the following manufacturers:

� Southwestern Flowtech and Environmental (SFE)

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.3 V-A meter (‘flow meter’) equipment pre-approved for use in flow monitoring includes equipment from the following manufacturers:

� Marsh-McBirney � American Sigma � ISCO � ADS

.4 The Contractor is reminded that these instruments typically have limitations in terms of velocity and depth ranges that must be considered prior to installation. Pre-approval does not warrant that these instruments are necessarily applicable for the sites to be monitored under this Contract.

.5 Equipment pre-approved for manual flow profiling includes:

� Marsh-McBirney Model 2000.

.6 Equipment pre-approved as ultrasonic level monitors include:

1. American Sigma model 950 2. Telog RU33 with Massa ultrasonic module

PART 3 EXECUTION

3.1 Equipment Installation Approval

.1 Design drawings shall be provided for approval by the City prior to installation of any non-temporary equipment.

.2 Provide information on confined space entry training of installation personnel.

.3 Provide safety plan, including details of confined space entry plan.

.4 Submit Equipment Installation Plan including items 3.1.1, 3.1.2 and 3.1.3.

3.2 Flow Site Calibration

.1 All instruments used shall be calibrated by manual flow (velocity) profiling throughout the full range of flows recorded at each station. Documentation of profiling exercises shall be provided in the monthly reports.

.2 The ‘full range of flows’ is defined as the range of recorded depths of flow from dry weather nighttime low flow conditions up to a minimum of 80 percent of the highest depth peak wet-weather event flow recorded.

3.3 Site Visits

.1 The sites shall be visited at a frequency appropriate to ensure proper equipment operation to meet the Data

Capture specified and for manual flow profiling during wet-weather events to confirm equipment calibration over the range of flows defined.

3.4 Data Capture

.1 The Contractor is required to obtain a data capture of at least 95 percent of readings over each one-month period. This is calculated as the number of 5-minute recordings reported out of the total number of 5-minute intervals between the start and end of the billing month.

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.2 Of the data captured, at least 95 percent of readings must accurately represent sewer flow after quality assurance and approved correction if required.

.3 The overall capture of approved and usable data is therefore 90 percent (95 percent * 95 percent = 90 percent).

3.5 Quality Assurance

.1 Data shall be examined by the Contractor and corrected as necessary to provide an accurate representation of sewage flow for all readings. Both the raw and corrected data shall be provided in electronic and hydrograph (for sewer flow) or hyetograph (for rainfall) formats. Documentation of corrections made and reasons for corrections shall be provided in the reports.

.2 The data reported shall be of high calibre and should not require extensive examination or correction by the Engineer. However sufficient data shall be reported to allow the Engineer to fully audit all corrections made by the Contractor.

Appendix C

QA/QC for Flow Monitoring Data



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2. APPENDIX C – FLOW MONITORING DATA QA/QC PROCEDURES

2.1 QA/QC PROCEDURES

The purpose of this section is to provide guidance and procedures for reviewing sewer flow monitoring data. Reviewing this type of data is both an art and a science; with regular review and practise it is possible to identify numerous issues with the data early on. Doing so avoids collection of data that would otherwise require complex repair or, worse, be unusable.

SCATTER PLOTS

A traditional method of reviewing flow monitoring data is to plot two variables (level vs. velocity, or level vs. flow) and establish a baseline for normal operation. Then, for example, if the site were to experience a sudden change such as backwatering or sensor shifting, the data would plot off of the “normal” curve.

In the example in Figure 1, plotting level vs. flow yields a good scatter plot. A curve fit (such as a polynomial fit) can then be applied to a portion of “good” data to determine what is normal for this location. By plotting future data to be reviewed against the curve fit, variation from the “norm” is usually identifiable which can then trigger further investigation as to the cause.

The scatter plot approach is of limited use for weirs and flumes, as plotting the level vs. flow curve will always yield a perfect fit, corresponding to the level vs. flow relationship for the weir or curve. However, were the relationship to accidently change partway through a season due to human error or a meter fault, the change would be obvious. See Figure 2 for an example.



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Figure 1: Example Scatter Plot of Level and Velocity Data

Figure 2: Example Scatter Plot of a Weir or Flume

TIME SERIES REVIEW

With practise and enough examples, reviewing the data plotted directly as time series (i.e. flow vs. time) is a convenient and quick way to identify issues. The method looks for consistency in the data. If for example, on a weekly basis, one week of non-validated data is plotted along with the preceding 3-weeks of validated data, a reference point from which to view the new data is provided. Looking for inconsistencies in magnitude, baseline, etc. will routinely identify issues.



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The following sections outline the major issues that often appear in sanitary flow monitoring data.

SUDDEN UPWARD BASELINE SHIFT

A sudden upward baseline shift almost always indicates a weir or flume has become obstructed by an object. Common items can do this including blocks of wood and other types of debris. The clearing of the object (either by maintenance staff or self-clearing) should be clearly identifiable in the data as well.

Figure 3: Sudden Rapid Rise/Fall w/o Rainfall Indicates Likely Blockage and Removal

BENCHING INTERFERENCE - SENSOR MISALIGNMENT

A sudden flattening of the baseline at night almost always indicates that an ultrasonic sensor has been knocked out of alignment. If the sensor is not pointing directly downwards, it may be picking up the manhole benching instead of the sewage level.

No rainfall



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Figure 4: Sensor Echo Off of Benching from Misaligned Sensor

GRADUAL UPWARD SHIFT

Gradual upward shift is almost always caused by gradual debris build-up, which can include gravel, grease, rags, etc. The upward shift is easily identified by plotting the flow along with the rainfall signal. Baseline shifting due to Inflow & Infiltration (I&I) visually correlates very well with rainfall. A slow steady increase in the baseline with no identifiable rainfall pattern will usually indicate debris build-up. It is very important that this problem be addressed quickly, as it is very difficult to reconstruct data that has been impacted by a changing debris level.

Figure 5: Gradual Baseline Increase Caused by Debris Build-Up



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MAGNITUDE OF BASELINE FLOW

The minimum flows that occur in the middle of the night are usually assumed to be about 85% groundwater, with only about 15% being sewage when the main land use upstream of the flow monitoring station is residential. Even with commercial and institutional uses, these are often focussed on serving people who are asleep at night. As a result, looking at the magnitude of the minimum base flow each night is often a good indicator of whether or not the flow data is correct. Specifically, a large base flow relative to the magnitude of the daily flow variation can indicate a problem.

One exception is sites that serve industrial uses, which can operate during night shifts and hence the baseline magnitude is not necessarily a good indicator of issues where industrial is the primary use. The latter half of the previous Figure 5 is a good example of where the baseflow is too high relative to the magnitude of the daily fluctuations.

MAGNITUDE OF DIURNAL VARIATION

Similarly, there is a “normal” range of daily fluctuations in typical land-use applications. When the magnitude of these diurnal variations is too large or too small, or when it suddenly changes, it may be indicative of problems with the data.

Figure 6: Issue with Different Diurnal Pattern Magnitude after Meter Repair

YEAR-LONG GROUNDWATER TREND

On sites where longer data collection is being conducted, a year’s worth of data is worth reviewing to see how the minimum baseline flow (which is mostly groundwater) has varied over the course of the year. The minimum should occur in August and September. After the first rains in October and November, it is typical to see that the baseline has



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risen to what could be called the “winter” value. This will often be noticeably elevated above the “summer” value. From generally April onwards the value will often decrease back down to the minimum “summer” value as groundwater levels decrease. Some sites may not show a noticeable change throughout the year, which depends on the ground conditions within the catchment. What is important to look for is a trend in the wrong direction (i.e. summer baseflows higher than winter). See the following figure for an example of a properly working station (the spurious zero readings in August were caused by a temporary meter failure).

Figure 7: Typical Summer and Winter Baseflows

RAINFALL: VISUAL COMPARISON OF MULTIPLE GAUGES

By far the most common type of rain gauge failure is debris plugging. This is usually easily identified by comparing a given time period against other rain gauges, as shown in the following figure. When preparing such a figure, make sure that the axis scaling is set to the same value for each station, and stack the stations on top of each other for easiest visualization. Figure 8 shows an example.

Another common indication of a plugged rain gauge is a slow, continual single rain tip repeated at fairly regular intervals, when other gauges clearly show a more dramatic response. This is caused by a very slow leakage of the plugged funnel, as shown in Figure 9.



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Figure 8: Rainfall Signals from Multiple Stations Showing Missing Storm

Figure 9: Rainfall Signals from Multiple Stations Showing Plugged Gauge

Appendix D

I&I Envelope Methodology



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3. APPENDIX D - I&I ENVELOPE METHODOLOGY This section explains the procedures to apply the I&I Envelope Methodology. It assumes that the dataset is quality controlled and corrected. In order to use the methodology, flow and rainfall data should both be at 5-minute intervals. The rainfall gauge should be the closest gauge that represents the rainfall for the sewer flow monitoring catchment.

PURPOSE

The purpose of the I&I Envelope Method is to use a collection of recorded storm events to create a correlation between the amount of rain that falls in a catchment and the amount of I&I that shows up at the flow monitoring site. Knowing the return period of the rainfall, combined with the assumption that rainfall return period correlates to I&I return, allows the correlation to be used to produce estimates for return period based I&I. This allows catchments that were monitored in different seasons with different storm events to be compared on an “apples to apples” basis.

STEP 1: PREPARE DATA FOR STORM SELECTION

To begin, prepare monthly graphs of flow with rainfall for the site to be analyzed. Keep the same y-axis scale for each graph, and lay them out end to end to see the entire season. In addition, if monthly rainfall summary tables exist lay these out as well. See the following figures for a monthly example of a graph and rainfall table.

Figure 10: Typical Monthly Data Plot showing Flow and Rainfall



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Figure 11: Monthly Rainfall Summary Table

For sites in Metro-Vancouver, ideally you should have 6 months of data covering the span October to March. In any case work with the data that you have.

STEP 2: CHOOSE STORM EVENTS

Using the graphs (and rainfall tables if available), begin to make a list of storm events. Here are some guidelines for selecting storm events:

• Start with the largest events, identifying them by both their visual response on the

graphs as well as by rainfall totals on your rainfall tables. Identifying storms that stand out using their 6, 12, and 24 hour totals is a good starting point.

• Give first priority to storms that have one clearly defined peak, and which clearly return to pre-storm baseflow conditions after the rain event. Storms with multiple peaks or that do not return to baseflow conditions before the next storm are more difficult to analyze.



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Figure 12: Example of Two Rainfall Events, not Separated Sufficiently

Figure 13: Example of Storm Event with only One Major Peak

• Starting from the largest storm in the record, work towards the smaller events until

you have at least 10 events, or have run out of useful storms in your record.



APPENDIX D

I&IMP TEMPLATE

STEP 3: DEVELOP DRY WEATHER PATTERNS

A dry weather pattern is required for each storm. A good dry weather pattern will have the following characteristics: • Distinguishes between Saturday, Sunday, and weekdays, as each of these can have

distinctly different patterns; • Will have a consistent minimum nightly flow that shows good agreement with the

flow signal in the days leading up to the actual storm event. This ensures that the pattern is adequately estimating both the sanitary and groundwater components;

• The subtraction of the dry weather pattern from the total flow signal prior to the storm will thus generally yield zero.

Figure 14: Typical Dry Weather Flow (DWF) Pattern

Often, it is not possible to obtain suitable DWF patterns for each storm, due to a variety of reasons: • There may not be a suitable dry weather period that matches the minimum nightly

flows leading into the storm event (i.e. the groundwater conditions do not match). In this case, it is acceptable to take an otherwise matching pattern and shift it by the required amount of GWI either up or down. However, this can only be done if the baseflow conditions prior to the storm event are constant. For example, if the DWF



APPENDIX D

I&IMP TEMPLATE

pattern does not match because the effects of a previous storm event are still present, this is not a suitable approach.

• An otherwise suitable pattern may have one or two damaged days of data. In this case, replacement with another day of data is acceptable, as long as the minimum nightly flows match and days are replaced with equivalent days (Saturday replaced with another Saturday, Sunday with Sunday, etc.)

STEP 4: PREPARE AN ESTIMATE OF GROUNDWATER INFILTRATION (GWI)

Groundwater can be extracted as a constant value from the DWF patterns prepared in Step 3. The easiest way to do this is to assume that a constant percentage of the minimum flow that occurs each night is GWI. Many flow monitoring exercises in Metro-Vancouver and the Capital Regional District have been done over the previous 15 years. Comparisons of measured flow during dry periods with a standard sewage design parameter of 250 L/capita/day often yields a remainder for GWI that can be estimated as 85% of the minimum nightly flow. Smaller catchments tend towards 85%, while larger catchments and regional points tend towards 70%. This is an approximation which works well enough for catchments that are predominantly residential in nature. Catchments with large industrial, commercial, and institutional loadings can contain processes which run even at night. In this case, there are several potential actions that can be taken: • Observe the flow on weekends and over holiday periods. Often, the processes will

shut down during these times which can be identified in the flow monitoring data. Use the flows during these times to estimate GWI using the percent minimum nightly flow approach.

• Compare estimated GWI from neighbouring catchments (on an area-weighted basis) that share similar pipe age and condition characteristics. If there is no reason to expect that GWI in the target catchment should be higher than neighbouring catchments, then ICI processes may be to blame.

• If neither of these options work, state in your analysis that the catchment in question contains ICI processes which may be affecting the accuracy of the GWI estimate.

To estimate groundwater using this method:

• Read the 7 minimum nightly flows from each night in your DWF pattern (you may need to apply an hourly boxcar average to your data first if it is excessively noisy);

• Average them, then multiply the result by 85% (or as low as 70% for large catchments with significant travel times or storage from upstream pump stations).



APPENDIX D

I&IMP TEMPLATE

STEP 5: SUBTRACT THE DWF PATTERN FROM THE FLOW SIGNAL

The DWF patterns that were previously developed contain both the sanitary component as well as the groundwater infiltration. When the DWF pattern is subtracted from the total flow signal, what remains is the rainfall dependent I&I (RDI&I). For each storm event, the ideal scenario is to have the RDI&I at effectively zero prior to the rainfall.

Figure 15: Example of Storm and DWF Pattern with Good Pre-Storm Agreement



APPENDIX D

I&IMP TEMPLATE

Figure 16: Example of Storm and DWF Pattern Offset by Constant Value

If the DWF pattern is visibly offset by a constant value, this is an indication that the groundwater conditions were not the same for the DWF pattern and the storm event. A simple subtraction of the DWF pattern from the total flow signal for each event will yield the instantaneous RDI&I for each storm event. When working with fine resolution data (5 minute timestamps), the RDI&I signal will often be quite noisy. Typically, a rolling 15 minute or hourly boxcar average can be applied to the raw RDI&I signal to remove spikes and make the true RDI&I signal easier to see. RDI&I, when averaged over 15 minutes or hourly, is most often used for facilities design where an estimate of the true peak RDI&I is desired. For reporting between catchments and also between Municipalities, the use of a 24 hour boxcar average is preferred. This averaging period removes practically all effects of system operation and catchment size, allowing for more consistent assessment of I&I values between catchments.



APPENDIX D

I&IMP TEMPLATE

Figure 17: Examples of Raw, 1-Hour, 24-Hour Average RDI&I Signals

STEP 6: DETERMINE PEAK AND 24-HOUR RDI&I VALUES FOR EACH STORM

For each storm event, read off the maximum 1-hour (or 15-minute) and 24-hour RDI&I values for each storm event and note these for use in the next steps. Pay close to attention to ensure that:

• The peak that you are reading correlates with the rainfall event, and is not unrelated to

the storm of interest (this can be an issue when attempting to use very small storms with small RDI&I response);

• The peak of the RDI&I event is over and is declining. This can be an issue when using 24-hour averaging if your graph does not extend far enough to see the 24-hour average RDI&I clearly reducing.

STEP 7: CALCULATE MAXIMUM RAINFALL TOTALS AT VARIOUS DURATIONS

For each storm event, calculate the maximum amount of rainfall that occurred over the following durations: 1 hour, 2 hour, 6 hour, 12 hour, and 24 hour. These are common durations that rainfall intensity-duration-frequency (IDF) data is available for. Always work with a boxcar total on fine resolution (5 minutes), when locating each maximum total.



APPENDIX D

I&IMP TEMPLATE

Figure 18: Calculating Maximum Rainfall over Various Durations

STEP 8: PLOT EACH STORM RDI&I VALUE WITH RAINFALL

In this part of the analysis, each storm peak RDI&I value (derived from Step 6) is plotted as a point on the Y-axis of a graph, with the X-axis value being maximum total rainfall for that storm event (derived from Step 7). Work only with either the 24-hour RDI&I values or peak RDI&I values at any one time. Overlay the return period lines for the rainfall gauge you wish to use in the analysis. Use 2, 5, 10, 25, and 100 year return periods and these are normally available for any given rain gauge. Assume for this example that we are working with the peak RDI&I values. The question arises: which rainfall duration to use for the X-axis of the graph? To answer this, a sensitivity analysis is performed to determine which rainfall duration produces the best correlation with RDI&I. To do this, plot the peak RDI&I values in turn against the 1, 2, 6, 12, and 24 hour rainfall totals. Fit a linear trend line through the data and note the coefficient of determination (R2). Keep in mind the following:

• Smaller catchments, or catchments with larger inflow components will tend to

correlate better with shorter rainfall durations; • Larger catchments, or catchments with less inflow and more infiltration will correlate

better with longer rainfall durations.



APPENDIX D

I&IMP TEMPLATE

Figure 19: I&I Envelope with Poor Correlation (1 Hour Rainfall Duration)

Figure 20: I&I Envelope with Poor Correlation (6 Hour Rainfall Duration)



APPENDIX D

I&IMP TEMPLATE

Figure 21: I&I Envelope with Good Correlation (24 Hour Rainfall Duration)

Select the graph that produces the best correlation with the highest R2 value.

STEP 9: CRITICALLY REVIEW ANY OUTLYING STORM POINTS

Attempt to increase the overall R2 value by critically looking at each storm that does not appear to be a good fit with the other points. There are numerous reasons why this could occur, here are some examples:

LOW RESPONSE FROM FIRST STORM EVENT

This is most often caused by the first significant storm event of the season. If the groundwater table is still at summer lows, the storm will not yield the same amount of RDI&I as if it had occurred in the winter when the groundwater table is elevated.



APPENDIX D

I&IMP TEMPLATE

Figure 22: Storm with Low RDI&I Response due to Low Groundwater Table

HIGH RESPONSE FROM A STORM EVENT CAUSED BY LOW DWF PATTERN

If a storm seems abnormally high relative to the other events, it may be caused by a low DWF pattern which is not correctly estimating the amount of GWI. The result is that the RDI&I for that event will be overestimated.

Figure 23: Storm with High RDI&I Response due to Low DWF Pattern



APPENDIX D

I&IMP TEMPLATE

Figure 24: Low DWF Pattern Resulting in Overestimate of RDI&I

HIGH RESPONSE FROM A STORM PRECEDED BY ANOTHER STORM

Another common source of a “high” storm point on the I&I Envelope is when the storm of interest is preceded by another event, and the flow has not returned to baseflow conditions before the storm of interest occurs. The result is that the RDI&I for the second event will be estimated as being too high. In this case, it is recommended that only the first event be used.



APPENDIX D

I&IMP TEMPLATE

Figure 25: Two Storms that are Too Close to Each Other, Only Use the First

POOR OR NO CORRELATION POSSIBLE

If it proves impossible to produce a useful correlation regardless of which rainfall duration is chosen, then the cause is typically either:

• The catchment is too small, or the RDI&I rates too small, to standout above the

background noise of the flow monitoring data; • If there is a consistently measurable response in RDI&I but it does not appear to trend

upward noticeably with rainfall, the catchment may have a hydrologic or hydraulic restriction that prevents the RDI&I from leaving the catchment beyond a limiting rate.



APPENDIX D

I&IMP TEMPLATE

Figure 25: No Correlation Possible, Regardless of Rainfall Duration Chosen

STEP 10: INTERSECT THE TREND LINE WITH RAINFALL RETURN PERIODS

After critical review and adjustments as necessary, the trend line may then be intersected with the various rainfall return periods, and values for the RDI&I read off the Y-axis.



APPENDIX D

I&IMP TEMPLATE

Figure 26: Reading the 5-Year, Peak 1-Hour RDI&I (Based on 24-Hour Rainfall)

In the above example, the intersection of the best fit curve with the 5-year rainfall return period yields a 5-Year, peak 1-hour (based on 24-Hour rainfall) RDI&I value of 65 L/s.

STEP 11: REPEAT STEPS 8-10 FOR 24-HOUR RDI&I

The procedure is the same when looking for a correlation between rainfall and the 24-Hour average RDI&I. By convention, the 24-hour rainfall duration is chosen by default, rather than searching different durations for the best correlation.



APPENDIX D

I&IMP TEMPLATE

Figure 27: Reading the 5-Year, 24-Hour Average RDI&I (Based on 24-Hour Rainfall)

In the above example, the intersection of the best fit curve with the 5-year rainfall return period yields a 5-Year, 24-hour average (based on 24-Hour rainfall) RDI&I value of 45 L/s.

STEP 12: ADD GWI TO RDI&I TO CALCULATE TOTAL I&I

Total I&I = GWI + RDI&I Add the GWI calculated from Step 4 to the RDI&I value obtained from Step 11 (for Peak I&I) or Step 12 (for 24-Hour Average I&I) to yield the total I&I.

STEP 13: NORMALIZE BY CATCHMENT AREA

Expressing I&I in flow units (such as L/s) is useful for tasks such as sizing facilities. However, to compare the relative severity of I&I between catchments, and also to gauge how severe the I&I is relative to defined measures, it is useful to normalize I&I using one of two systems: • Area based: dividing the flow by the size of the catchment in hectares thus converting

flow from L/s into L/ha/day; • Pipe based: dividing the flow by the total sum of (length x diameter) of the pipes in

the catchment, converting flow L/s to L/km-mm/day.



APPENDIX D

I&IMP TEMPLATE

Both methods have the effect of allowing relative comparisons. The catchment area method has been used mostly in Metro Vancouver and the Capital Regional District, due to the relative ease of calculating catchment area. Due to the length of pipes on private property, the pipe based method is harder to calculate accurately without good knowledge of the amount of private laterals in the catchment.

Appendix E

I&I – Age Relationship WEF Paper

APPENDIX E – I&I–AGE RELATIONSHIP WEF PAPER

I&I Rates and Sewer Infrastructure Age: Is There a Strong Correlation?

Chris Johnston, P.Eng.

Peter Fell, P.Eng. Kerr Wood Leidal Associates Ltd.

200 – 4185A Still Creek Drive Burnaby, B.C. V5C 6G9 Canada [email protected], [email protected]

Malcolm Cowley, P.Eng. Capital Regional District

625 Fisgard Street, P.O. Box 1000 Victoria, B.C. V8W 2S6 Canada

[email protected] 1. ABSTRACT

Introduction and Background

The Capital Regional District (CRD) is a partnership of 13 municipalities (including Victoria, the capital city of British Columbia) and 3 electoral areas with a total land area of about 2,400 square kilometres, located at the southern tip of Vancouver Island. The CRD provides services that are regional in nature including the sewerage system that serves some 350,000 people. Within the Core Area of the region, municipal sewers feed into the major CRD trunk sewers, which collect and convey sewage to two discharge points. The outskirts of Greater Victoria is experiencing significant growth, (particularly in its Western Communities), and that along with high inflow and infiltration in the older downstream infrastructure overloads the systems capacity during rainstorms, often resulting in sewage overflows. The CRD’s first sewers were installed in the early 1900s, and most are 70 to 100+ years old. The older sewers were primarily constructed using vitrified clay (VC) pipe. In the 1950s, 60s, and early 70s asbestos cement (AC) pipe was predominately used. Since the late 1970’s, almost all sewers have been constructed using polyvinyl chloride (PVC) pipe. The Western Communities were serviced and connected to the CRD trunk sewers in 1996 using PVC pipe. The Western Communities were originally characterized as having free-draining soils. As a result, a relatively low inflow and infiltration (I&I) rate of 7,500 litres/ha/day (800 U.S. gallons/acre/day) was selected for design. For less permeable soils, a rate of 11,200 litres/ha/day (1,200 U.S. gallons/acre/day) is typically used throughout the region. Capacity upgrades to the Western Communities Trunk system, due to growth, were scheduled for 2015. In 2002, during a major storm event, the six-year-old infrastructure reached 80% of its design capacity eleven years ahead of the planned upgrades. A subsequent analysis of the flows made it clear that population growth and I&I rates were far greater than

originally anticipated. More specifically, I&I rates in the newer areas were more than twice the design rate, and appeared to be similar to those of less porous soils. I&I rates in the older areas appeared to have increased as well. Fearing a continuing trend, the CRD commissioned a study to investigate the relationship between I&I rates and sewer infrastructure age, using sewer flow monitoring databases in Greater Victoria and Vancouver. This relationship could then be used to more accurately determine future I&I rates and evaluate various funding levels by municipalities on the rehabilitation of the sewage collection systems. The relationship can also be used for benchmarking by comparing an individual basin to others of similar age. 2. KEY WORDS

Infiltration and Inflow (I&I) or (I/I), Sewer Age, Design Rate, I&I Relationships 3. METHODOLOGY

To establish the relationship between I&I and sewer age, the following approach was adopted: � Select 54 sewerage areas varying in infrastructure age; � Determine the average age of sanitary sewers in each catchment; � Select an analysis method to determine I&I return periods from monitoring data; � Derive the 100-year, peak-hour I&I flow rate for each catchment; � Derive a relationship between age of sewer and 100-year I&I rate;

Once a relationship has been derived, the CRD can use it to predict future sewer flows provided only basic rehabilitation programs are employed. They can also use the relationship to assess the benefits of more aggressive I&I reduction programs on the scheduling of capital programs. 4. 100-YEAR RETURN PERIOD CRITERIA

The 100-year storm was the selected by the CRD as the design return period for facility sizing based on commitments made to Provincial authorities under the CRD’s Liquid Waste Management Plan (LWMP). The LWMP stipulates that flows from this storm must be conveyed to approved discharge locations without causing a sanitary sewer overflow (SSO) to occur. 5. DEFINITIONS

Terminology for defining extraneous flows in sanitary sewers varies significantly from one jurisdiction to another. The definitions and acronyms utilized in this paper are defined in Table 1.

Table 1 Extraneous Flow Parameters

Component Acronym Calculated

As Definition / Explanation

Groundwater Infiltration GWI Extraneous flow from the ambient long-term water table, not influenced by individual rainfall events.

Rainfall-Induced Infiltration RII

Rainfall that follows a path to the sewer through the soil and/or from short-term, rainfall-based increases in water table elevation.

Stormwater Inflow SWI Rainwater that enters the sewer through direct (non-soil) connections to the runoff surface.

Rainfall-Dependant Inflow & Infiltration

RDI&I SWI + RII

Total peak rainfall-sourced extraneous flow, averaged over intervals ranging from 5 minutes to 24 hours depending on catchment characteristics.

Inflow & Infiltration I&I RDI&I + GWI

Total Inflow and Infiltration.

6. SELECTING THE CATCHMENT AREAS

Since the early 1990s, the CRD have maintained and operated a Supervisory Control and Data Acquisition (SCADA) network that monitors over 75 stations. Many major storm events have occurred in the region over that period including two 100-year return period storms (measured over the 2 to 24 hour durations) that occurred on November 10 and 23, 1990. However, since flow monitoring data from the larger catchment areas will be significantly attenuated giving the appearance of lower I&I unit rates, it is critical that only the smaller catchments are used in the analysis. For this reason, it was decided that an average catchment size of 100 hectares (240 acres) was preferable with a maximum catchment size of 400 hectares. Based on the above, 27 of the CRD’s stations were used in the analysis. Although not as comprehensive as the CRD’s dataset, municipalities in the Greater Vancouver Regional District (GVRD), located in the lower mainland of British Columbia, also have considerable flow data that could be analyzed. The data could be used to assist in deriving the age-of-sewer versus I&I rate relationship provided the underlying soil structure and rainfall amounts are comparable. Comparison of Underlaying Soils

The cities of Surrey and White Rock (in the GVRD) were deemed to have soil conditions comparable to Greater Victoria/CRD conditions. The (South) Surrey and White Rock datasets reflect sewer response to rainfall for areas underlain by glacial tills or clays. Due to comparable low permeabilities, similar responses can also be expected for areas underlain by bedrock. Typically in these types of conditions, infiltrated rainwater collects and is channeled in the much freer-draining utility trenches, resulting in the generation of a hydraulic head on the pipes and consequently the pipe defects. This

mechanism is active in both the mainline sewer system and the sewer laterals, serving individual parcels. The opposite is true for sandy, boulder or cobble soils with deep groundwater tables. Utility trenches in these areas typically don’t build up hydraulic head. As a result, deteriorated sanitary sewers in these areas may have lower I&I rates. For this reason, datasets from collection systems with porous soils were not included.

Comparison of Rainfall Totals

Table 2 compares the 100-year rainfall amounts from the Greater Victoria area to the two selected GVRD areas. Table 2

Comparison of 100-year Rainfall Totals

Area

100-year, 24-hour,

Rainfall Amount

(mm)

South Surrey/White Rock, GVRD 97

Gonzales Point (Victoria), CRD 106

Based on the similar rainfall totals listed above, it can be concluded that no additional factoring is required as the totals are within 5% of the average. The selected GVRD data therefore can be plotted directly on the CRD data. 7. ESTABLISHING AGE-OF-SEWERS DATABASE

The next step involved assembling information about the approximate age of the sewer collection system. To do this, GIS databases from each municipality were assembled to determine the average catchment age. The age of each pipe was linearly weighted by its length. The following equation describes the age calculation process: 8. SELECTION OF AN I&I ANALYSIS METHOD

Due mainly to budget constraints, flow monitoring programs are rarely undertaken on a comprehensive, municipal-wide basis. Generally, such programs are completed over a period of years. To complicate matters, no two rainfall events are the same, and it is unlikely that a ‘perfect’ storm event, which matches the desired return period, will occur during most flow monitoring programs. Therefore, the analysis method used must allow direct comparison of the I&I response in any two basins, regardless of the year or

Catchment Age = ΣΣΣΣ (length x age)

Total length

magnitude of the storms recorded. This enables a consistent I&I reporting process with ‘apples-apples’ comparisons. This section reviews the I&I analysis methods currently available, and provides a preferred method for use in this paper. It should be noted that the review focuses on RDI&I (Rainfall-Dependent Inflow and Infiltration) determination methods and not snowmelt or groundwater based determination methods. Determining Comparable I&I Rates and Design Values

I&I rates between catchments can be directly compared only when exactly the same rainfall intensities are experienced across both basins. Comparing flows measured for different events does not account for the difference in rainfall pattern, total depth, intensity, duration, and antecedent soil moisture conditions, and can lead to erroneous conclusions. Where same storm comparisons are not possible, several methods can be used to determine I&I return periods: 1. Computer Models (I&I Characterization Methods): A physically-based

hydrologic computer model can be used to simulate the response of sewer catchments to rainfall. Each catchment is calibrated using flow monitoring data to establish the individual components of the extraneous system flow (SWI, RII and GWI). Once completed, the models can simulate antecedent soil and rainfall patterns and then may be run under identical rainfall conditions. A ‘design rainfall event’ is usually selected to simulate the typical response of each of the basins.

For the purposes of this study, we are concerned only with the total RDI&I component of the flow hydrograph. Given this fact and the cost and time involved with building 54 separate hydrological models, computer modeling was ruled out as an analysis methodology.

2. Statistical Methods (I&I Quantification): These methods vary greatly but are all

generally based on predicting flow response from a short or medium-term history of sanitary sewer flow monitoring data and historical rainfall records.

Overview of Statistical Methods

A literature review was conducted to identify and assess different Rainfall-Dependant Inflow and Infiltration (RDI&I) quantification methodologies. The objective of the search was to determine a suitable method that could be applied in a cost-effective manner given the number of stations to be analyzed. RDI&I statistical methods can be grouped into the following categories: � constant unit rate methods; � percentage of rainfall volume (R-value) methods; � percentage of streamflow model methods;

� probabilistic methods; � predictive equations based on rainfall/flow regression; and � predictive equations based on synthetic streamflow and basin character. To compare the various methods, an evaluation matrix was developed. A simple rating system was developed to accurately predict a basin’s flow response. One point was given for each of the following criteria: � resource intensive (data requirements); � technical complexity (easy or difficult method to use); � ability of method to account for antecedent moisture conditions; � ability of method to account for spatial and temporal differences in rainfall; and � ability of method to predict a peak hour design flow for the basin. Consequently, each method was assigned a rating from 0 to 5 for each of the above requirements and placed into a matrix for evaluation. Key References Consulted

The following references were consulted during the literature review: � Bennet et. al (1999), Using Flow Prediction Technologies to Control Sanitary Sewer

Overflow, Water Environment Research Foundation (WERF) Project 97-CTS-8. � Greater Vancouver Sewerage and Drainage District (1993), I/I Quantification

Methodologies: A Summary of North American Studies, G.V.S.D.D. � Greater Vancouver Sewerage and Drainage District (1995), Inflow and Infiltration

Reduction Program – Fraser Sewerage Area: 1994-1995 I/I Analysis Results, G.V.S.D.D.

� United States Environmental Protection Agency (1995), National Conference on

Sanitary Overflow (SSOs), Office of Research and Development, EPA/625/R-96/007 � Wright et. al (2001), Comparing Rainfall Dependent Inflow and Infiltration Methods,

Models and Applications to Urban Water System, Vol. 9, W. James, Ed. Recommended I&I Quantification Method

Based on the results of the evaluation matrix, the preferred method chosen is the RDI&I

Envelope method. 9. RDI&I Envelope

The RDI&I Envelope method was developed by the East Bay Municipal Utilities District (San Francisco). It is a graphical method that summarizes rainfall and sewer flow events

gleaned from examining historical monitoring records. By plotting these results, the relationship between rainfall volume and RDI&I volume can be developed. It is even possible to develop ‘return-period’ design flow values for RDI&I if necessary, based on the rainfall analysis. This approach can be used to develop overall RDI&I design values, or can be used to rank different catchment areas based on their overall wet-weather response. Because the RDI&I Envelope method is statistical, it lends itself well to the situation within the CRD, where the SCADA system provides up to 15-years of flow data. Flow records therefore exist for a wide range of storm magnitudes. Figure 1 shows an example of an RDI&I envelope developed using many years of flow monitoring information. This particular plot uses instantaneous 1-hour flows instead of volumes to illustrate the flexibility of the method despite varying rainfall distributions. However, the method was developed based on rainfall and RDI&I volumes rather than flows, and experience has shown the volumetric approach to be more reproducible. It was proposed that the method be adapted to use for peak-hour flows provided limits were placed on catchment size and rainfall distribution. Figure 1 Example of RDI&I Envelope Method

0

50

100

150

200

250

300

Insta

nta

neous I&

I F

low

(L/s

)

0 20 40 60 80 100 120

11/08/90

11/22/90

12/02/90

02/03/91

11/16/91

01/26/92

12/14/9412/25/9402/18/95

11/06/95

12/09/95

11/18/94

06/06/94

08/16/94

11/08/94

RDI&I AnalysisI&I Design Value Derivation

71mm 80mm 91mm 98mm59mm

2 Yr 5 Yr 10 Yr 25 Yr 50 Yr24-Hr Rain Totals (mm)

270

Diagonal Band Indicates Estimated

"Upper Bound" to RDI&I

(RII + SWI)

Increasing

Soil Moisture

ContentRegion of

Estimated RII

Contribution

Region of Estimated

SWI Contribution

25-Year Return Period I&I Estimate

Graphical RDI&I Characterization (I&I Envelope)

Upper and lower boundaries are drawn on the graph to illustrate the effect of antecedent soil moisture on the RDI&I response. The upper bound represents the maximum expected RDI&I for a particular rainfall event following a prolonged wet period. The lower bound represents storms that occur following dryer periods; this boundary provides an estimate of the SWI component. Rainfall depths for various return periods are calculated from the nearest rainfall gauging station using statistically derived Intensity-Duration-Frequency (IDF) curves. The point of intersection of the diagonal RDI&I line and the vertical line corresponding to the rainfall depth of a specific storm return period represents an expected upper bound to the RDI&I caused by that storm event with saturated soil conditions. Total I&I is calculated by adding the maximum seasonal groundwater infiltration (GWI) to the RDI&I value selected. 10. DETERMINING THE 100-YEAR I&I RATES FOR EACH CATCHMENT

The I&I Envelope method uses flow and rainfall monitoring data sets collected over periods ranging from 6-months to many years to establish a rainfall to I&I rate relationship. Since the severity of rainfall events can be established from IDF curves, the corresponding severity of I&I rates can be estimated for all return periods when matched to the most sensitive rainfall duration for a particular catchment. To determine the most sensitive rainfall duration for a given catchment, peak 1-hour RDI&I values are plotted against rainfall totals at various durations, and a linear line is fit through each set of data points. The best R-squared value from the fitted lines is chosen to identify the most sensitive duration for that catchment. For newer sewers less than 40-years old, the 24-hour duration tends to dominate as the fast responding SWI components are smaller. In older areas, durations as low as 4 to 6 hours dominated. Once the most sensitive duration is established for a catchment, the results may be utilized to establish I&I rates for a specific return period. Figure 2 illustrates the process of determining the 100-year return period RDI&I. Note in this example, the data is presented for the most sensitive duration for the catchment in question (24-hours). As previously mentioned, the 100-year storm was the selected by the CRD as the design return period for facility sizing based on commitments made to Provincial authorities under the CRD’s Liquid Waste Management Plan (LWMP). The flow monitoring datasets varied from 6 months of data to 15 years of data. The minimum data requirements for each catchment were four storm events with at least one of the storms having a return period of 2 to 5 years. At least three of the storms must

have occurred during saturated soil conditions. To ensure that the resulting RDI&I rate for the desired return period fully accounts for variance in conditions such as degree of soil saturation, the resulting best-fit curve is shifted upwards to pass through the maximum recorded RDI&I value. Figure 2 Determination of RDI/I Return Periods

RDII Envelope Evaluation

Determination of Rainfall-Dependent I&I Return Period Rates

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

0 10 20 30 40 50 60 70 80 90 100 110 120

24-hour Rain Totals (mm)

Best Fit Curve

using MS Excel

Estimated 100-Year RDII:

17,500 L/Ha/d

Moved to reflect

saturated ground

conditions

Figure 1

Return

Periods

(years):2 5 10 25 50 100

Peak 1

-Ho

ur

RD

I&I

Vo

lum

e (

L/h

a/d

ay)

cccccc

11. AGE OF SEWER AND 100-YEAR I&I RATE

Figure 3 plots the average age of each of the 54 independent sewer catchments with the corresponding 100-year peak instantaneous I&I rate (i.e. peak hour). The trend is consistent, accurate, and highly correlated as indicated by the R2 fit for the dataset of 0.90. Impact of Historical Design and Construction Methods

It could be argued that care and attention to separate sanitary sewers and properly design storm sewer collection systems did not formally begin until 1960; therefore, the trend for recently constructed sewers may not experience such a dramatic rise after the next 50 years. Further, it could be argued the shift to PVC pipe in the seventies may also dampen the rise in I&I rates from historical levels. However, even for the collection systems younger than 50 years, the early trend is still evident (see Figure 4), and fits roughly the same curve.

Figure 3 Determination between RDI/I Age and Sewer Age Figure 4 Determination between RDI/I Age and Sewer Age

SANITARY SEWER AGE VERSUS RAINFALL-DEPENDENT I&I RATE


Relationship Using Only Data up to 40 Years

y = 542x + 12,418

R2 = 0.4177

Relationship Using All Data

y = 12355e0.0325x

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

0 10 20 30 40 50 60 70 80 90 100

Age (years)

Peak 1

-ho

ur,

100-y

ear

RD

I&I

(L/H

a/d

)

Areas Less than 40-Years Areas Greater Than 40-Years

Figure 4

DETERMINATION OF RELATIONSHIP BETWEEN RDII RATE AND SANITARY SEWER AGE


y = 12,355e0.0325x

R2 = 0.9013

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

0 10 20 30 40 50 60 70 80 90 100

Age (years)

Peak 1

-ho

ur

100-y

ear

RD

I&I R

ate

(L

/Ha/d

)

Catchment Value Expon. (Catchment Value) Figure 3

AC

Pipe

PVC Pipe VC Pipe

54 Independent Basins in CRD and GVRD

Deriving the Relationship

The equation to the right describes the relationship in Figure 3 that can be used to calculate the 100-year I&I rates based on sewer collection system age. Fitting the equation to 54 independent basins from the CRD and GVRD, based on their own unique flow monitoring programs, indicates that I&I, contrary to established opinion, can be predicted with remarkable accuracy with fairly simple controls for climate, soil conditions, and construction standards. Further, it proves that I&I rates increase significantly over the design life of the pipes. Establishing I&I Design Rates

Based on the above findings, the following table can be development, assuming no basin rehabilitation is undertaken: Table 3 Design RDI&I Rates for Different Sewer System Ages

Statement Design I&I Rates

(L/ha/d)

Estimated 100-year I&I Rate at Sewer System Age - Year 0 12,500

Estimated 100-year I&I Rate at Sewer System Age - Year 50 40,000-63,000

It should be noted that these I&I rates include contributions from private service laterals. Private service laterals include the entire main from the sewer connection at the property line to the house. It has been documented in many studies that lateral contributions can be as high as 70%, but on average is 50 to 60% of total I&I response. It is also noteworthy that it may be extremely difficult to ever rehabilitate a basin to a sufficient level to achieve RDI&I rates lower than 12,500 L/ha/d. This may be a reasonable target for construction of new sewers, but may be too optimistic for rehabilitated sewers. In the case of CRD and GVRD sewer systems, the historical trend by the municipalities has been towards rehabilitation programs maintaining the structural integrity of the system. Very few “full-basin rehabilitation” programs have been undertaken within the study areas. Based on Table 3, then, it may be possible to maintain a collection system closer to the lower range provided rehabilitation programs go beyond structural repair.

I&I Rate100 = 12,355 e (0.0325*(sewer age))

where I&I Rate100 is in L/ha/d and sewer age is in years.

12. DISCUSSION

Implications

The relationship established between age of sewer and I&I rates indicates that the design rate for new sewers in the CRD should be 12,500 L/ha/d (i.e. Year 0) not 7,500. Even if new sewers were rehabilitated every 50 years, resulting in an average basin age of 25 years, the corresponding I&I rate would still be estimated at 27,800 L/ha/d. This is almost four times the design rate of 7,500 L/ha/d used in the Western Communities. The implications of these finding are significant, and have an impact on the methods used to determine design I&I rates for future sanitary infrastructure. As a result of the findings of this study, the CRD evaluated the impact of various levels of sewer rehabilitation / replacement funding that could be potentially adopted by the member municipalities within the Core Area. Negotiations with these municipalities resulted in agreement to base trunk sewer design criteria on an I&I rehabilitation strategy that involved a municipal commitment on sewer rehabilitation funding levels. This approach will ensure that trunk sewer facilities are sized appropriately to convey future design flows incorporating allowances related to growth in both people and I&I. Further, although the construction and inspection methods used in the CRD for new sewer pipe installation are well regulated, recommendations have been made to the municipalities to review existing practices to reduce the I&I to sewer age relationship.

Appendix F

Description of Rehabilitation Technologies


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APPENDIX F

I&IMP TEMPLATE

1. APPENDIX F – DESCRIPTION OF REHABILITATION TECHNIQUES

1.1 REHABILITATION TECHNOLOGIES – PIPES (SEWER MAINS)

CURED-IN-PLACE PIPE

Cured-in-place pipe (CIPP) is a rehabilitation technology where a fabric liner saturated with a liquid resin is placed inside the existing sewer main, inflated, and then cured. The technology is used to provide a lining inside a host pipe to prevent infiltration through defects in the pipe, or it may be used to form a structurally sound new pipe. The process may be used on an entire segment of sewer main between manholes, or in specific locations of a sewer main as a spot repair. The resin type, fabric type, installation method, cure method, and design conditions vary. Resin types are typically epoxy, vinylester, or polyurethane. Fabric types are typically polyester felt or fibreglass. The liner is pulled (usually with a cable) or inverted in the host pipe. Cure method is usually by steam, hot water, ultraviolet light, or ambient air. CIPP can be used for spot repairs or manhole to manhole runs.

PIPE BURSTING

Pipe bursting is used to replace an entire segment of sewer main between manholes. The process involves replacing an existing pipe by pulling in a new high-density polyethylene (HDPE) pipe and simultaneously bursting the old pipe into fragments with a steel- bursting head. The broken pipe fragments remain in place in the surrounding soil. Pipe bursting installation techniques are static, pneumatic, or hydraulic. In static pipe bursting, the bursting head is attached to a pulling device (usually a chain, cable, or threaded rods) and is pulled by force of the pulling device. In pneumatic pipe bursting, the bursting head may be attached to a pulling device or not, but receives most of the force from a pneumatic device in the bursting head. In hydraulic pipe bursting, the bursting head has an expansion device that compresses surrounding soil by means of hydraulic jacking prior to the pull.

PIPE REAMING

Pipe reaming is used to replace an entire segment of sewer main between manholes. The process involves a directional drill used with a rotating head to grind the existing pipe into small pieces while pulling in a new pipe of the same or larger diameter.


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CHEMICAL GROUTING

Chemical grouting of sewer mains is a process where acrylamide grout is pressure-injected into a crack, joint, or lateral connection in a sewer main. A remotely operated grout packer delivers the grout to the selected location. The grout packer is similar to a pipe plug that uses air to inflate bladders at each end of the plug. The grout is then injected under pressure into the annular space between the plug and the sewer main, and then migrates into the cracks and open joints. The flexible and non-cohesive grout remaining on the pipe wall when the grout packer is removed is pulled out, leaving grout in the joint spaces of the pipe.

SLIPLINING

Sliplining is typically used to line an entire length of sewer main between manholes, although it can be used in shorter portions of the sewer main. Sliplining involves pulling or pushing a smaller diameter pipe or liner into place inside an existing pipe. The sliplined pipe material is typically HDPE or fibreglass, although some other materials may be used. The pipe is typically grouted at the ends or over the length of the pipe.

SPIRAL WOUND PIPE

Spiral wound pipe is a type of pipe used to slipline an existing pipe. This pipe is formed by spirally winding a continuous strip of some material into a pipe by means of a machine placed in the excavation or manhole. Strips can be made of polyvinyl chloride (PVC), HDPE, or steel. The strips are typically 2 to 6 inches wide and have a locking mechanism such that the strips “lock” into adjacent portions of the strip. Spiral wound pipe comes in two types: (1) those which are “wound” to the diameter required for sliplining, and (2) those which are “wound” in a smaller diameter, then twisted to expand the pipe to the host pipe diameter after the wound pipe is in place. There may also be steel wire or rebar placed in the strips to add structural support.

DEFORMED/REFORMED HDPE

Deformed/reformed HDPE is a method for installing a new HDPE pipe or liner inside an existing sewer main. The HDPE pipe is pulled through a die to fold the pipe into a smaller diameter. The pipe is secured with breakaway plastic straps in the deformed position. The pipe is pulled into the sewer main and reformed either by plugging and pressurizing the main or by running a rounding device through the line to break the straps and allow it to form within the existing pipe.

SWAGE LINING

Swage lining is a method for installing a new HDPE pipe inside an existing sewer main. The HDPE pipe is pulled through a die or set of rollers to neck-down the pipe to a smaller diameter. This method relies on the property of polymeric materials to retain a memory


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I&IMP TEMPLATE

of their original shape. The smaller diameter pipe is then pulled into the host pipe and pressurized to allow it to revert to the original diameter.

FOLD AND FORMED PVC

Fold and formed PVC is a method for installing a new PVC pipe inside the entire segment of sewer main between manholes. The PVC pipe is heated and then folded into a smaller diameter at the factory. Then, after it is pulled into the sewer main, the PVC pipe is heated and pressurized to unfold and form to the shape of the host pipe. The PVC pipe is then cooled to form a rigid pipe inside the host pipe. This process relies on the property of PVC that allows it to be rigid at normal temperatures and flexible at higher temperatures.

1.2 REHABILITATION TECHNOLOGIES – MANHOLES

RESET FRAME AND RAISE TO GRADE

Resetting the frame is a method intended to adjust a frame that has moved horizontally and/or to raise the cover above grade to prevent inflow, mostly in non-paved areas (for example, when a cover is located in a slight depression where ponding of water occurs). The installation involves minimal excavation – only enough to allow replacement of damaged concrete levelling rings and addition of new rings to bring the top of the frame above grade. New concrete levelling rings are used to repair the chimney section where existing brick or concrete chimneys have worn out. The levelling rings may be sealed with non-shrink cement grout, a rubber gasket, or butyl rubber mastic. Likewise, the frame may be sealed to the chimney by the use of a rubber gasket or butyl rubber mastic. HDPE plastic levelling rings are also available that are meant to replace concrete levelling rings with a more watertight seal. The levelling rings are not solid HDPE; rather, they are hollow with support ribs.

INTERIOR COATINGS

Cementitious coatings are applied with a trowel, sprayed on, or poured, and are used to seal cracks on all or portions of the interior of the entire manhole. These coatings typically contain a mix of cement and chopped fibres. The coatings may be sprayed directly on the wall, over a wire mesh, or poured into an HDPE form with rebar. The coatings often contain calcium aluminate as an additive, which provides additional corrosion resistance for the concrete. Epoxy coatings are applied as a spray and are used to coat the interior of the entire manhole to form a water/vapor barrier. These coatings are two-part epoxy, typically 100-


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I&IMP TEMPLATE

percent solids by volume. They require abrasive blasting or high-pressure water cleaning for surface preparation. Polyurethane coatings are also applied as a spray and are used to coat all or portions of the interior of the entire manhole to form a water/vapor barrier. These coatings are made of urethane resin. They require abrasive blasting or high-pressure water cleaning for surface preparation.

EXTERIOR COATINGS

Exterior coatings are used on all or portions of the barrel, cone, and chimney sections of manholes. These coatings are unique in that they require less bonding than interior coatings, due to the fact that the backfilled soil holds them in place and any groundwater presses the coating onto the manhole. These coatings come in different types: spray-on cementitious, epoxy, or polyurethane; shrink-wrap plastic; and/or adhesive rubber tapes. These coatings require excavation around the manhole.

MANHOLE LINERS

PVC manhole liners are used to line all or portions of the interior surface of the manhole. They are made of sheets of PVC and are mechanically or adhesively connected to the manhole. Mechanical connection is either by: (1) locking protruding shapes of PVC that are embedded into grout applied to the interior of the manhole, or (2) attachment to the manhole by stainless steel anchors with a PVC cap welded over the top of the anchor. Adhesive connection is by a polymer applied to the concrete manhole, which is then bonded to the PVC with an activator. Pre-formed fibreglass or HDPE manhole liners are rigid shapes fabricated at a plant to match the interior size of the manhole. They are used to line the interior surface of the manhole in the base, barrel, cone, and sometimes in the chimney sections. The liner is installed by excavating and removing the manhole cone section. Then the liner is inserted and the cone section replaced. For installations in portions of the manhole, the edges of the liners are grouted to form a seal with the manhole surface. Fibreglass manhole liners are used to line all or portions of the interior surface of the manhole. The liners consist of a fabric liner saturated with a liquid resin. The liner is placed inside the manhole, inflated, and then cured. The fabric typically consists of layers of woven fibreglass bonded to a non-porous membrane, the resin is epoxy, and the curing method is steam.

CHIMNEY BARRIERS

Chimney barriers are made of a rigid medium-density polyethylene riser with a thick base that sits on top of the cone section of the manhole. The concrete manhole rings are then


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I&IMP TEMPLATE

stacked on the thick base on the outside of the riser. The riser becomes a barrier to I&I entering the chimney section.

Another chimney barrier is a levelling ring boot. They are made of a circular heavy-ribbed rubber that is held in place with expanding interior stainless steel rings. The boots are installed by simply opening the cover, so no excavation is required. The boots need to be fitted around any ladder rungs located in the chimney or the ladder rungs may be removed.

MANHOLE COVERS

Gasketed manhole covers are steel covers with an inset gasket either in the frame or placed between the frame and cover. They are intended to prevent inflow from around the manhole cover. Solid covers without holes are available, as are plugs for the lifting holes. Manhole pans are available that fit under the manhole cover and are intended to prevent inflow through holes in the manhole cover. The pans are either HDPE or stainless steel.

MANHOLE REPLACEMENT

New manholes are typically installed with rubber gaskets between barrel sections. Cement patching grout is typically used on all joints between base, barrel, cone, chimney, and frame sections. Fibreglass manholes are used to replace the base, barrel, cone, and in some cases the chimney portions of existing manholes. The manholes are typically pre-fabricated to ship to the site in one unit. The fibreglass manholes require excavation and full installation, as is required for new concrete manholes. HDPE manholes are used to replace the base, barrel, cone, and in some cases the chimney portions of existing manholes. The manholes are typically pre-fabricated to ship to the site in one unit. The HDPE manholes require excavation and full installation, as is required for new concrete manholes.

1.3 REHABILITATION TECHNOLOGIES – FROM SEWER MAIN TO PRIVATE

PROPERTY LINE

CURED-IN-PLACE PIPE

CIPP installation and products for laterals and side sewers are similar to and in some cases the same as for sewer mains. A fabric liner saturated with a liquid resin is placed inside the existing pipe, inflated, and then cured. CIPP may be used to form a structurally


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I&IMP TEMPLATE

sound new pipe or reduce infiltration. The method may be used on all or portions of the lateral or side sewer. A cleanout or excavation is required at some location on the lateral or side sewer to allow access for insertion of the liner.

PIPE BURSTING

Pipe bursting is used to replace all or a portion of the lateral and side sewer between the house and sewer main. The process involves replacing an existing pipe by pulling in a new HDPE pipe and simultaneously bursting the old pipe into fragments with a steel bursting head. The broken pipe fragments remain in place in the surrounding soil. A cleanout is usually placed where the pipe-burst lateral connects to existing pipe, either at the house or at the property line. Pipe bursting of laterals is usually done using the static method because of the lower force required to burst smaller diameter laterals.

CHEMICAL GROUTING

Chemical grouting of laterals and side sewers is a process where acrylamide grout is pressure-injected into a joint or lateral connection point of a lateral or side sewer. The grout is delivered remotely to the location by a mechanism that has two sealing devices; the grout is injected into the entire space between the two. The flexible and non-cohesive grout is pulled out of the pipe in the area between the sealing devices, leaving grout in the joint spaces of the pipe. Where used to seal the connection between the sewer main and lateral, three devices are used, two in the main and one in the lateral.

SERVICE CONNECTION LINERS (SCLS)

An SCL is a cured-in-place liner used to seal the service connection where the service lateral meets the sewer main. The SCL, installed by remote device, typically consists of a fibreglass fabric and polyester resin. A portion of the liner seals around the opening of the lateral in the sewer main, and a portion (usually 2 to 6 inches in length) is located in the lateral. The SCL is held in place either by an epoxy that forms a bond at the interface between sewer main and lateral, or by mechanical friction between the SCL and the lateral.

SERVICE CONNECTION AND LATERAL LINERS (SCLLS)

An SCLL is a cured-in-place liner used to seal the service connection between the sewer main and lateral and some portion of the lateral and/or side sewer. The SCLL, installed by remote device, typically consists of a felt fabric and polyester resin. A short portion of liner is placed in the sewer main around the full diameter, and a second portion is located a defined distance up the lateral and/or side sewer. The two pieces are attached. Some products can be used for lining more than 80 feet up the lateral. Tees and fittings can sometimes be lined through; however, they are usually excavated to allow for reconnection.


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1.4 REHABILITATION TECHNOLOGIES – PRIVATE LATERAL1

OPEN CUT REPLACEMENT

The open cut method is most suitable for much damaged pipes that are shallow and in open areas with obstacles. Open-cut allows installation of a new pipe of any diameter and material, and furthermore, the layout or depth of the lateral can be changed. Mature landscaping and driveways, retaining walls, etc., reduce the suitability of this method. The method causes disturbance to the homeowner’s property causing public relations difficulties and restoration of landscaping and road payment can be expensive.

SLIPLINING

Sliplining is a method in which a slipliner pipe (typically an HDPE pipe for laterals) is pushed into the existing lateral pipe. The advantage of this method is that no special equipment or chemicals are needed, however, the disadvantages generally outweigh the advantages: the pipe diameter is unacceptably reduced, the method is time-consuming and it is not cost competitive with other rehab methods.

CURED-IN-PLACE (CIP) RELINING

CIP relining method is a method in which a resin-saturated tube is inserted into the pipe and the resin subsequently cured creating a “pipe within pipe”. The main components of a CIP relining system area a fabric tube and a resin, and often a plastic protective coating. Main advantages are: the method stops infiltration through defects in the lateral pipe (cracks, offset joints, etc.); restores or enhances the structure integrity; not limited by soil conditions, groundwater level and active leaks; suitable for repair of deeper laterals; long-term repair (50 years design life), etc. Limitations are: The method does not allow upsizing of the pipe; not suitable for laterals with severe offset pipe joints; not suitable for severely corroded laterals with a mineral buildup; cannot remove sags or any protrusions in the pipe; roots could be a future problem; chemicals used are hazardous.

PIPE BURSTING

Pipe bursting is a method in which a cone-shaped tool (bursting head) is forced through an existing pipe fracturing the pipe into small pieces. The replacement pipe is usually an HDPE pipe. Advantages are: new lateral pipe is installed and can be upsized by one pipe size; excavation is much less than with open-cut replacement; applicable in all pipe types; works in most different soil conditions; roots should not be a future issue; short disruption of service to homeowners; no chemicals are used, etc. Limitations are: excavation and associated surface restoration; difficult in hard clays; difficult in pipes repaired with metal clamps in the past; not suitable for pipes with many sharp bends. With more than three sharp bends in the pipe, CIP relining is usually better suited;

1 WERF 02-CTS-5, Methods for Cost-effective Rehabilitation of Private Lateral Sewers, 2006


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I&IMP TEMPLATE

significant sags cannot be removed; risk of damaging nearby objects and surface objects when bursting at shallow depths.

CHEMICAL GROUTING

Chemical grouting creates a sealing collar of material around the pipe by injecting a self-setting grout into an opening in a pipe wall, which is followed by the grout passing through the pipe wall into the surrounding soil and bonding of the grout with the soil. Advantages are: No excavation is generally required; performs pipe testing and repairs only where the repair is needed; eliminates infiltration; fast so disturbance to homeowners is minimal; inexpensive, etc. Limitations: no structural repair is possible; no pipe diameter upsizing; sometimes can’t be completed (the section can’t be pressurized); the grout may dry out and crack under some groundwater conditions; chemicals used are hazardous if spilled or splashed on the skin or in the eyes (no hazard remains once the material cures), etc.

FLOOD GROUTING

Flood grouting seals manholes, mainlines and laterals simultaneously in one setup utilizing an exfiltration sealing process. Two proprietary chemical solutions are consecutively applied to “flood” an isolated section of sewer, where they exfiltrate through defects in pipes and manholes into the soil and chemically react with each other. The cured grout in the soil is a watertight sandstone-like silicate. Advantages are: no excavation is generally required; eliminates infiltration in an entire section, i.e. both in mainlines and all connecting laterals at the same time; no limit in applicability with respect to the pipe material, shape or size, or depth; applicable in pipes with many sharp bends; disturbance to homeowners is minimal; the chemicals used are environmentally friendly. Limitations are: no structural repair is possible; no pipe diameter upsizing; sometimes cannot be completed; chemicals used are hazardous if spilled or splashed on the skin or in the eyes (no hazard remains once the material cures), etc.

SLUG GROUTING

Slug grouting seals a mainline and the laterals connected to it in one setup utilizing an exfiltration sealing process. However, the grout does not flood the entire section but only a limited volume, which travels from the downstream manhole towards the upstream manhole and through each connecting lateral along the way. Advantages: the only time excavation is required is if a cleanout needs to be installed; eliminates infiltration both in mainlines and all connecting laterals at the same time; no limit in applicability with respect to pipe material or depth; little limit in applicability with respect to cavernous soils; disturbance to homeowners is minimal; no chemical are used; cost competitive. Limitations are: No structural repair provided and no pipe diameter upsizing; this is a new method that needs to be tested and proved in practice.


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I&IMP TEMPLATE

ROBOTIC REPAIR

Robotic repairs renovate lateral-to-mainline connections by applying a resin (or mortar) to the damaged piece of pipe, which cures into a material compatible with the host pipe and which becomes an integral part of the pipe. Advantages are: no excavation is required; provides structural repair; eliminates infiltration; very suitable for repair of break-in protruding laterals; eliminates root problems; relatively easy to use in field applications; cost is reasonable; fast and disturbance to homeowners is minimal. Limitations are: repairs only the lateral-to-mainline connection and a relatively short distance into the lateral; chemicals used are hazardous if spilled or splashed on the skin or in the eyes (no hazard remains once the material cures).

Schedule A

METRO VANCOUVER

INFLOW AND INFILTRATION MANAGEMENT PLAN TEMPLATE

SCHEDULE A – I&IMP

Municipality: City of Anywhere

Checklist - Circle Applicable Components: (G = Goal-Based, P=Prescriptive)

Participants & Roles Application

Metro Muni. Private Approach G P

3. I&I Quantification 5-year 24-hour X Metro Vancouver provides overall I&I rate from

billing meters

X X

5-year peak hour X City provides through flow monitoring program X X

25-year peak hour X City provides through flow monitoring program X X

I&I Envelopes X Develop 5-year return design flow X X

I&I-Age

Relationship

X Benchmark I&I rates by catchment considering the

average pipe age (normalized by length)

X X

4. Sources of I&I Mains X CCTV inspection in flow monitoring areas X X

Manholes X Visual assessment of manholes for signs of I&I X X

Public Laterals X Abandoned service identification program X X

Public Stormwater X Smoke & dye testing X X

Private Laterals X X Lateral inspection program X X

Private Stormwater X X Smoke & dye testing X X

5. Actions & Implementation 20-year Evaluation

Program

X X System-wide condition assessment and flow

monitoring to establish:

- Condition assessment database

- Baseline I&I level

X X

Ongoing Evaluation X X Repeat over a 20 year time cycle X X

Inflow Reduction X X

X

X

X

X

X

- Manhole cover repair / replacement

- Correction of storm-sanitary cross-connection

- Public lateral repair / replacement

- Private Lateral repair / replacement

X

X

X

X

X

X

X

X

Infiltration (fast)

Reduction

X X

X

X - Private lateral repair

- Manhole repair / replacement

X X

Infiltration (slow)

Reduction

X X

X

X

- Elimination of abandoned service connections

- Sewer mainline repair / replacement

- Manhole repair / replacement

X

X

X

X

X

X

Tier 1 Program X Mainline and lateral interface rehabilitation X X

Tier 2 Program X Public lateral rehabilitation X X

Tier 3 Program X X Targeted Private lateral rehabilitation X X

Private Lateral

Program

X X Incentives, Regulations, Municipal Initiatives X X

Preventative

Measures

X X Sound engineering specifications for design of

sewers and laterals, with inspection/enforcement

X X

Public Education X X Public education for dealing with I&I issues through

various communication channels

X X

Municipal Bylaws X Development of municipal bylaws addressing I&I and

stormwater control

X X

6. Monitoring & Verification Review I&I

Reduction Progress

X Review I&I progress every 4 years X X

Benchmark I&I

rates

X X - Municipalities update I&I-Age Relationship

- Optionally, Metro Vancouver may host municipal

data for comparison and mutual benefit

X X

Perform Post-

Rehabilitation Flow

Balance

X Estimate total I&I removed from system upon

completion of I&I reduction work (catchment by

catchment)

X

I&IMP Update X X Update I&IMP every 4 years X X

METRO VANCOUVER


1. INTRODUCTION AND BACKGROUND

Overview

Summary of key elements of I&IMP.

Revision history of I&IMP document

Ongoing record of changes made to

I&IMP, including author and date.

Municipal Guidelines, Design Criteria

Municipal and Regional Targets

• Municipal I&I goals (perhaps

unrelated to ILWRM). e.g. 25-

year, peak hour design rate; and

• Location of regional monitors

and associated ILWRM target I&I

rate(s).

METRO VANCOUVER


2. CONTEXT FOR I&I

MANAGEMENT

Historical I&I Management Efforts

Description of previous work.

Effectiveness of Previous Programs

Knowledge summary for program legacy

and sharing with other municipalities.

Known I&I Issues

Specific issues that the plan will address.

METRO VANCOUVER


3. I&I QUANTIFICATION

Flow Monitoring

The I&IMP records a municipality’s

intended monitoring program and

progress to date, and as such identifies:

• All discrete flow monitoring

catchments in the

municipality/region;

• History and results of previous

monitoring; and

• Time frame for monitoring all

catchments, with known

monitoring priorities stated.

Quantification

Intended methodology for quantifying

I&I can be identified in this section. The

I&I Envelope is recommended –

alternatives include the USEPA’s free

SSOAP toolbox, or hydrologic modelling.

The I&IMP may also contain an I&I vs.

catchment age graph to present the

current conditions of the catchments

and identify potential candidates for

rehabilitation or repair.

METRO VANCOUVER


4. SOURCES OF I&I

Determination of I&I Sources

I&I sources will be determined in

catchments where rehabilitation is

envisioned. For example, the following

methods could be used to identify I&I

sources:

• Mainlines – CCTV inspection

• Manholes – Visual assessment

• Public Laterals – Targeted lateral

CCTV inspection

• Public Stormwater – Smoke &

dye testing

• Private Laterals – Targeted

lateral CCTV inspection

• Private Stormwater – Smoke &

dye testing

General techniques such as using an I&I

Age Curve, or reviewing RDII

hydrographs and envelopes may assist

in identifying specific methods for

determining I&I sources.

Prescriptive Approach

A Prescriptive Approach to identifying

I&I sources would be to make use of

data that is being collected through flow

monitoring and other asset

management activities. Specifically,

municipalities may be collecting the

following information through

scheduled inspection programs:

• Mainline CCTV

• Manholes

• Smoke Testing

Good practice is to centralize this

information in a database and link to

GIS assets. This will allow for ready use

in the I&IMP.

Targeted Approach

Good practice includes targeted

assessments of I&I sources in specific

catchments where rehabilitation will

occur. Examples of application of

targeted investigations include:

• Lateral CCTV inspections to

identify abandoned laterals in

areas with high lateral-to-

building ratios;

• Follow-up dye testing to confirm

potential stormwater cross-

connections identified from

smoke testing;

• Hydrologic modelling in

catchments with complex I&I

issues; and

• Air testing or exfiltration testing

in areas with suspected

infiltration issues.

The intent of the information collected

in the Targeted Approach is to inform

the selection of rehabilitation

techniques and quantify the required

scope of rehabilitation.

METRO VANCOUVER


5. ACTION-IMPLEMENTATION

Goal-Based vs. Prescriptive Program

Identify the type of program required

and note the reasons for selection.

If a municipality is not achieving the

Metro Vancouver target for I&I city-

wide, a Goal-Based approach is

recommended. If the city-wide target is

being met, a Prescriptive approach is

appropriate, however, special

conditions may dictate a Goal-Based

program at the catchment level. These

conditions could include:

• Sanitary sewer overflows in a

catchment;

• Reduced conveyance capacity

limiting development;

• Excessive pumping/energy costs;

or,

• An I&I response that greatly

exceeds the measured rates in

other catchments with similar

characteristics (i.e. above the

municipality’s Age-I&I rate

relationship).

A Goal-Based approach seeks to

achieve a specified I&I target (e.g.

11,200 L/ha/d city-wide, or 20,000

L/ha/d in a particular catchment). Flow

monitoring is used to measure the

effectiveness of the work performed,

and incremental (e.g. Tier 1, Tier 2, Tier

3) work programs may be applied

successively until the target is achieved.

Where targets are below 20,000 L/ha/d,

it is likely that the plan will require a

private lateral rehabilitation

component.

A Prescriptive approach applies best

practices based on available assessment

data to reduce or maintain I&I rates, but

differs from the Goal-Based approach in

that the work plan is not iterative, and

no specific I&I rate is targeted at the

outcome of the work. Measurement of

the success of the work (through post-

rehabilitation flow monitoring) is still

recommended to determine program

effectiveness and refine cost-benefit

analyses.

Infrastructure Rehabilitation

Select program components. Using

information derived in Sections 3&4,

identify appropriate rehabilitation

works. These works may address:

• Stormwater Inflow (cross

connections, manholes)

• Fast Infiltration (manholes,

service connections)

• Slow Infiltration (sewer

mainlines, manholes, service

lateral interfaces)

METRO VANCOUVER



(continued)

Prioritize Rehabilitation Program

Refer to I&I rates, I&I-Age Relationship,

and asset condition to prioritize

catchments for rehabilitation.

Private Lateral Rehabilitation Program

Where private lateral programs are

considered, identify any requirements

of the program, and outline the

proposed approach. Refer to the 2006

Sheltair Private Sewer Lateral Programs

report for approaches and legal

authority strategies.

Public Education Program

Targets of an education program are to

raise awareness of the the causes and

consequences of I&I, identify regulatory

provisions, convince citizens that the

benefits outweigh the costs, and

possibly to prepare residents for a

private lateral program.

Identify the following action and

implementation items:

• Extent of education program

(timeframe, region)

• Target audience

• Messages to be conveyed

• Media to be used to convey

message

Municipal Bylaws

The ILWRM requires Metro Vancouver

and municipalities “Enhance

enforcement of sewer use bylaw

prohibition against the unauthorized

discharge of rainwater and groundwater

to sanitary sewers.”

Action and Implementation Items

include:

• review of existing bylaw to

determine property access rights

for inspection and/or repair of

sanitary sewer laterals

• intent to draft (and adopt) a

bylaw restricting owners from

permitting stormwater or

groundwater from entering

sanitary sewer laterals.

Preventative Measures

Where appropriate, introduce:

• the use of sound engineering

specifications in the design and

inspection,

• enforcement of specifications

and design standards during

construction,

• plumbing inspections and

certifications

METRO VANCOUVER



(continued)

Funding Plan for Rehabilitation Work

It is recommended that funding for the

I&IMP be identified. Approaches for

determining the level of funding may

differ depending on whether the work is

Goal-Based or Prescriptive. At a

minimum, a funding level could be

derived based on the ILWRM

commitment to target a 100-year cycle

of replacement or rehabilitation of

sewerage infrastructure.

METRO VANCOUVER


6. MONITORING AND

VERIFICATION

Review I&I Reduction Progress

Outline intended process to track I&I

reduction. May include:

• Individual catchment flow

monitoring cycles.

• Review regional I&I rates every 4

years.

• Calculation of flow balance to

estimate total I&I reduced.

Consider extraneous factors such

as climate change, ageing

infrastructure, change in

materials, etc.

• Use “Sewer Condition Reporting

Template Standard Report,

November 2002” as a guide to

ensure a consistent approach to

sewer system evaluation and

reporting.

Benchmark I&I rates

Identify repository of I&IMP data,

consider regional benchmarking of I&I

rates.

I&IMP Update Schedule

Identify schedule to update I&IMP.

Consider flow monitoring program

length, asset evaluation timelines,

ILWRM/Metro Vancouver

commitments.

inflow and infiltration management plan template · 2014-08-08 · inflow and infiltration...

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