IIssssuuee NNoo.. 4400 EEnnvviirroonnmmeennttaall QQuuaarrtteerrllyy ooff SShheerrkkiinn IIssllaanndd MMaarriinnee SSttaattiioonn 22000055

SHERKINCOMMENT

Providing Clean Waterin Dubin Bay

Birds of Farne Islands

INSIDEINSIDE

Grey Reef Shark (Grey Reef Shark (CarcharhinusCarcharhinusamblyrhynchos) amblyrhynchos) and gorgonian fan.and gorgonian fan.Photographer: Pete Photographer: Pete AtkinsonAtkinson

NigaliPassage tto NNirvana

Page 2 ....................................................................................................................................................................Sherkin Comment 2005 – Issue No. 40

ContentsEDITORIAL: Management of Ireland’s Wild Salmon..2

Drift netting is not the only problem that wildsalmon face, according to Matt Murphy.

The Rise and Rise of the Gannet ................................3Oscar Merne on the good news for the Gannetpopulation.

Problems Facing Copenhagen from Transport Pollution ....4Finn Terp explains how Copenhagen is coping withtheir air pollution problems.

Providing Clean Water for Dublin Bay ..................................5Clean in Dublin Bay means a Blue Flag forDollymount Strand.

Birds of the Farne Islands ........................................................6Anthony Toole visits a paradise for birds off the northeast coast of England.

Backyard Burning ......................................................8A change of behaviour is needed to stop illegalburning.

A Spotlight on World Environmental Matters ..............9Interesting news on the world’s environment fromAlex Kirby.

Sea Turtles ............................................................................10An informative leaflet from ENFO on sea turtles.

On-site Treatment of Waste Water ................................11Gerard O’Leary of the EPA stresses the need for properwaste water systems.

Thresher Shark (Alopias vulpinus) in Irish Waters ....12Declan Quigley talks about a very rare visitor toIrish Waters.

The Wind Ships ..................................................................13Daphne Pochin Mould reminisces on sailing ships.

New Developments and Flooding Risks........................14Paddy Leahy outlines the need for a flood riskassessment for certain new developments.

Nigali – Passage to Nirvana............................15/16/17Life underwater in the South Pacific, with PeteAtkinson.

Thirty-five Years of Pollution Control in America ....18Matt Murphy interviews Walter Mugdan, US EPADirector in New York.

Breeding Birds in Roaringwater Bay, 2005 ..............20A report from Julian Wyllie on populations for2005.

Aquatic Bugs of Sherkin Island ......................................21Christopher Barry highlights some freshwater insects.

Back to Saxon Transylvania ....................................................22John Akeroyd continues to highlight the preciousflora of Romania.

Silicon – From Flint Axe to the Space Age ..................23Anthony Toole continues his look at the elements.

Publications of Interest ............................................24Oileáin – A Guide to the Irish Islands ......................25

A wonderful adventure from David Walsh.Captain Cockle ........................................................26

More exciting facts from John Joyce.East Coast Nature Reserve ........................................27

BirdWatch Ireland’s wonderful new project.Nature’s Web/Taste of the Sea Stir-Fry......................28

A new internet-based environmental newsletter forchildren and a seafood recipe from BIM.

Puzzle Page ..............................................................29Damien Walks for Gold ............................................30

Damien O’Donovan earns a gold award from Gaisce.Sherkin Island Marine Station Environmental

Competition 2005 ....................................31Presentation of prizes at the Carrigaline CourtHotel, Carrigaline, Co. Cork.

Listening for Answers ..............................................32Michael Ludwig is cautious about the results of“echo sounding” to assess fish stocks.

Editorial

Management of Ireland’s Wild SalmonBy Matt Murphy

MUCH is being written about theeffects that drift netting of wild salmon ishaving on stocks. If one is to believe thosethat want this type of fishing banned theneverything would be fine and our riverswill be well-stocked again after manyyears of decline. Of course, stocks willimprove but to what extent? SherkinComment believes much more will beneeded to solve the problems of salmonstocks in Irish rivers.

A management program must be intro-duced, together with much scientificresearch. Major issues need to beaddressed.

Rarely have there been any discussionson the impact of hydro dams on salmonon the rivers Erne, Lee, Liffey and Shan-non. Although these installations aretechnically passable (fish passes) by adultsalmon, they are not considered to haveself-sustaining salmon populations. Theserivers have been defined as non self-sus-taining in the Central Fisheries Board“Freshwater Salmon Habitat Asset” 2003.

The loss of potential salmon producinghabitat for the four Hydrodams is esti-mated at 35.5% of the total riverinehabitat accessible to salmon in Ireland(see Table 1). The Central Fisheries Boardis strongly of the view that serious con-sideration should now be given foradequate and effective free passage ofreturning adult salmon upstream to theirspawning grounds and the unhinderedmigration of smolts downstream, particu-larly during peak runs in these veryimportant wild salmon rivers.

The design of the hydro dams in theserivers should be reviewed to allow forthese fish to travel freely during the peakruns. The board also adds that this newapproach would also benefit other den-dromonus species such as shad, lampreyand eels.

The contribution of the generating sta-tions on the four dams to the ESBsnational grid only amounts to a maximumof 4.9% in a full year (see table 1). Onesolution to the problem would be to turnoff the generators for the peak migratoryperiod. The loss for the short periodwould be negligible ± 1.06% against thetotal capacity being generated by the ESBGeneration Stations (see table 2).

A proper management system needs tobe introduced in the rivers to ensure thereis (a) greater policing of illegal fishing (b)increased spawning areas and improve-ment in the quality of many of thosealready there (c) ownership of many fish-eries on the rivers is unclear and uncertainand must be addressed d) reasonableaccess for locals and visitors/tourists.

Research in the marine environment is

vital. It is recognised by salmon researchscientists that there is a major survivalproblem in the North Atlantic. Ireland isnot alone with declining salmon stocks.The USA and Canada have similar prob-lems. Changing sea temperatures in theNorth Atlantic need to be investigatedmore to see what effects they have on thesalmon. For instance, do they affectmigration speeds, routes and food avail-ability? Another issue is to what extent arepost smolts being caught as a bycatch inmackerel fisheries. Maybe one of theMarine Institute’s two research vesselsshould have as its priority an extensiveperiod each year on salmon research inthe North Atlantic.

Exploitation of salmon should be con-fined to the estuaries or river mouths thusavoiding a mixed salmon stock fishery atsea. This would allow each fishery to beindividually managed and strict quotascould then be enforced for each river basin.

The above issues we raise show thatthere are many problems that needaddressing on the decline of salmonstocks, most as important as drift netting.

Critics of commercial fishermen mustremember that they have a legal right tocarry out drift netting. Most drift nettersare fishing at sea in small boats not largetrawlers - it is one of the most dangerousoccupations. The weather conditions aremostly difficult to say the least. For manythe period (now very short) is a veryimportant income for them. A voluntarybuy out or set aside scheme along the linesof the decommissioning scheme for seafisheries is now essential.

To quote from remarks by NiallGreene, Chair “Stop Salmon Drift NetsNow” at a meeting in Cork City 18thMarch 2005:

“The campaign to end drift netting forsalmon at sea is being maliciously por-trayed by some as a row between anglersand the commercial sector as to whichshould have the right to kill most fish. It isnothing of the kind. It is a campaign for

measures to be taken that will ensure thesurvival of the Irish salmon as an eco-nomic, social and recreational resource.And it is a campaign that will, at the endof the day, require sacrifices by all ofthose who exploit the runs of salmon. Farfrom arguing that there can be no com-mercial net fishery we envisage achievinga situation in which it might very wellcontinue to catch many more salmon thanthe angling sector.” It is hoped that this isthe view of the various groups that opposedrift netting.

Finally, the drift net fishermen aroundthe coast need to organise themselves intoone group so that they can negotiate a fairdeal of compensation and also beinvolved in the management of salmonstocks. There are too many splintergroups, each going off at tangents. Theyneed one spokesperson that can put theircase with clarity. They should take alessen from the “Stop the Salmon DriftNets Now” group who have had one of themost effective and united PR campaignfor many years on an environmental issue.

Matt Murphy, Sherkin Island MarineStation, Sherkin Island, Co. Cork,Ireland.

+++++Subscription details on page 20+++++Subscription details on page 20+++++Subscription details on page 20++++

Table 2: World Catch of Atlantic Salmon 1960–2003

Table 1: ESB Generation Stations listed withcapacity (in Megawatts) and Fuel Type

Source: Wild Salmon and Sea Trout Tagging Scheme Fisheries Statistics Report 2003-2004 (Central Fisheries Board)

Sherkin Comment 2005 – Issue No. 40 ....................................................................................................................................................................Page 3

By Oscar MerneBACK in 1990, one of my

first articles for Sherkin Com-ment was titled GannetsGalore, which outlined thehealthy state of the breedingpopulation of the NorthernGannet Morus bassanus in Ire-land and elsewhere. Fifteenyears later, this article updatesthe situation here and places itin the context of the popula-tion as a whole, based largelyon the results of the interna-tional census of the speciescarried out during the breedingseasons of 2003 and 2004(Wanless, S., Murray, S. andHarris, M.P. 2005. The statusof the Northern Gannet inBritain and Ireland in 2003/04.British Birds 98:280-294).

First, let’s take a look athow Gannets have fared in Ire-land since 1990. Well, no newcolonies have been establishedhere, since the last one startedup on Ireland’s Eye in the late1980s. However, there hasbeen a continuing increase inthe overall numbers, at four ofthe five breeding sites. By farthe largest and longest estab-lished colony at Little Skellig,off the Co. Kerry coast (knownsince at least 1700), now has29,683 breeding pairs andappears to be full to overflow-ing. First-time breeders rearedat that site are now probablyhaving great difficulty findingvacant ledge space on LittleSkellig, and many may havemoved to the nearby BullRock, off Dursey Island inWest Cork. Here numbershave increased at over 7% perannum to 3,694 breeding pairs.While this is a very smallisland there appears to be suit-able nesting space for adoubling of the populationthere over the coming years.The third Irish colony, onGreat Saltee Island, off the Co.Wexford coast, has alsoincreased at about 7% perannum and now stands at

2,446 pairs. There’s ampleroom for further expansion onthis island. The tiny colony ona stack off Clare Island, Co.Mayo, has made no progress atall, probably because of asevere lack of space: it still hasonly three pairs. However, ifyoung birds wanting to breedthere set up on the main islandcliffs close to the stack, thecolony could “take off” infuture. Our newest colony onIreland’s Eye has increased byover 20% per annum and nowstands at 313 pairs, some ofwhich are nesting on the maincliffs opposite the stack, whichis now looking very crowded.I’d like to thank Alyn Walshfor taking the aerial photo-graphs of the colonies on LittleSkellig and Bull Rock, fromwhich Stuart Murray andSarah Wanless laboriouslymade the counts of all the littlewhite dots representing occu-pied nests. Also Sue

Callaghan, who checked thelittle Clare Island colony. Imyself carried out the cen-suses on Great Saltee andIreland’s Eye.

So, adding together the indi-vidual totals given above, wehave an Irish breeding popula-tion of 36,139 pairs ofNorthern Gannets. While thisis an impressive number, it issomewhat dwarfed by the182,511 pairs recorded inScotland. There the largestcolonies are on St. Kilda, westof the Outer Hebrides (59,622pairs), Bass Rock, at themouth of the Firth of Forth(48,065 pairs), Ailsa Craig, inthe Firth of Clyde (27,130pairs) and Hermaness, Shet-land (15,622 pairs). Scotlandhas ten other colonies. In Eng-land there is only one colony,at Bempton cliffs on the north-east coast, with 3,940 pairs. InWales there are 32,094 pairson Grassholm, off the Pem-

brokeshire coast, while a new“colony”, with one pair, wasfound at St. Margaret’s Islandin the Bristol Channel. Thereare two colonies, of 2,500 and3,450 pairs, on the ChannelIslands, bringing the grandtotal of the Northern Gannetpopulation of Britain and Ire-land to 260,635 pairs. So theIrish population is nearly 14%

of this, which is certainly notinsignificant. About one hun-dred years ago it wasestimated that the British andIrish total was about 47,000breeding pairs.

Elsewhere in the NorthAtlantic, Gannets are foundnesting in Canada (sixcolonies, with 103,026 pairs),Iceland (five colonies, with28,536 pairs), the FaeroeIslands (one colony, with 2,340pairs), Norway (five colonies,with 4,500 pairs), France (onecolony, with 17,000 pairs),with small numbers in Russia(35 pairs) and Helgoland, Ger-many (190). In respect of theHelgoland colony, it is interest-ing to note that some of thecolonists there originated fromGreat Saltee, known fromresightings of ringed birds. Sothe world population of North-ern Gannets is currently about417,600 breeding pairs, ofwhich 62.5% are found inBritain and Ireland.

The increase in the Gannetpopulation during the 20thcentury, and the consequentfoundation of new colonies, isthought to be due, initially, tothe cessation of humanexploitation of the species’eggs and chicks for food. This

very adaptable species, with aforaging range of up to severalhundred kilometres, probablybenefited from exploiting fish-ery discards, resulting inhigher adult survival rates andincreased breeding numbers.Paradoxically, the over-exploitation of somecommercial fish stocks by manin recent times may haveimproved the food situationfor Gannets, as the removal ofthe larger fish, which arepredatory and sometimes can-nibalistic, increases thenumbers of small andmedium-sized fish, which arefavoured by the Gannets. Themain concerns for the future ofthe Gannets in the NorthAtlantic are space limitationsat many of the large colonies,and changes in ocean tempera-tures and currents due toclimate change, which arealready affecting the distribu-tion of fish species.

Oscar Merne retired inJanuary 2004 as head of theBird Research Section of theNational Parks & WildlifeService, Department of theEnvironment, Heritage andLocal Government.

The Riseand Rise ofthe Gannet

On Great Saltee Island, off the Co. Wexford coast, the Gannet colony has increased at about 7% per annumand now stands at 2,446 pairs.

Gannet Morus bassanus

Little Skellig, off the Co. Kerry coast, has the largest and longest established colony of Gannets (knownsince at least 1700). It now has 29,683 breeding pairs and appears to be full to overflowing.

The Gannet colony on Ireland’s Eye has increased by over 20% perannum and now stands at 313 pairs.

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Osc

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erne

By Finn Terp

Introduction and main problemsDenmark has 5 million inhabitants and

Copenhagen has approximately 500,000 citi-zens. Copenhagen is the capital of Denmark andthe centre of the Øresund region.

As a local authority, Copenhagen does nothave the most effective instruments for reduc-ing air pollution at our disposal. Such instru-ments include higher taxes on fuel, cars andtransportation in general and other commodi-ties.

However, given the current political climateof the Danish parliament tax increases do notseem a realistic option, and local authority ini-tiatives are necessary if we are to make signifi-cant progress. A change in behaviour on the partof private households, businesses and institu-tions is a key prerequisite for bringing down theemissions. Close contact with citizens and busi-nesses gives local authorities an opportunity toinfluence this behaviour.

Environmental Protection Agency, City ofCopenhagen

The energy, water and environment adminis-tration is responsible for matters relating to theenvironment and utilities. Major responsibilities

include electric power, gas, district heating andwater supply as well as environmental control,sewage and waste handling.

The Environmental Protection Agency super-vises businesses generating pollution and handlestasks relating to polluted soil, water and air as wellas pest control and noise. Waste and recycling isalso a responsibility, which involves daily contactwith waste companies. The Agency is also in-volved in the implementation of Agenda 21 proj-ects and plays an important role in ensuring thatCopenhagen becomes an environmentally healthycorporation.

Main problemsThe main effects of transportation in Den-

mark and Copenhagen are the number of deadand injured people caused by car accidents. Airpollution causes also main health problems.Surveys say that we have 150 too early deathscaused by the emissions of ultra fine particles.In Denmark 150,000 people are exposed bytraffic noise above 65 dB. One third of them areliving in Copenhagen. Finally CO2 emissionsare increasing.

The governmental answers to the problemsare as follows:

• Many good words• The main problems are in the cities, so the

cities have to act and pay• Major investments in new roads• Minor investments in public transport, espe-

cially the new Metro in CopenhagenThe only direct environmental action from

the Government during the last years is fundinginstallation of particles filters on heavy vehi-cles. The funding amounts €4.5 million in 2004and 2005 in total.

Copenhagen, Statistics and TrendsCar traffic is the most significant cause of air

pollution in Copenhagen. In particular, nitrogendioxide (NO2) and small particles from car ex-hausts are a health problem. Between 2005 and2010 Copenhagen must comply with new EUlimit values for air pollution. This is a consider-able challenge. Our goal is to ensure, that the airquality of Copenhagen must be at such a levelthat the environment and health are not a risk.

Another goal is that environmental workmust be a natural part of citizens, organisationsand enterprises everyday lives. Everybody mustparticipate in making Copenhagen a sustainablemetropolis – at work, at home, and wherever we are.

The trends in Copenhagen are as follows• The number of inhabitants is growing• More families with children stay in the city• More jobs are created• The average income is getting higher• The living costs are increasingSince 1995 the commuting out of the city has

increased by 25%, the car ownership has in-creased by 40%, car traffic 15% and cycle traf-fic 40%.

Monitoring air pollutionCopenhagen has been monitoring air pollu-

tion since 1964. During most of the time wehave been monitoring in a joint monitoring pro-gramme with the national monitoring system.

In the 70s and 80s the sources to air pollutionwere industrial activities, individual heating andpower plants. Now, car traffic causes 85% ofthe pollution in the streets.

To get a daily picture of the air qualitieswhere people are living and staying we have amonitoring station on a street with heavy traffic.We measure NO, NO2, NOx, SO2, O3, CO TSP,PM10, PM2.5 and ultra fine particles.

In order to follow the back ground pollutionwe also measure on the roof of a high building.We measure NO2, O3, Toluene, Benzene, o-m-pXylener, formaldehyde, acetaldehyd and lead.The results are published in two news papers, inthe local television and on our home page,www.miljoe.kk.dk

New traffic and environment planIn 2002 Copenhagen started the preparation

of a new traffic and environment plan, espe-cially due to the increased traffic. We have nowbeen through a three year long process with in-tensive public participation – public meetings,opinion polls, interviews with groups of stake-holders, hearings etc. The public priorities are:

• 34 % – less noise and air pollution• 24 % – improved public transport• 20 % – improved facilities for cyclists• 11 % – better conditions for cars.

The plan propose following initiatives• Major improvements for cyclists (new cycle

lanes, better parking etc.)• Better public transport (more metro,

improvements for buses, better facilities)• Noise reduction measures (district plans,

new asphalt, insulation)

• Environmental zone• Funding cleaner technology• Environmental aspects in physical and other

planning• Behaviour change campaigns• (Road pricing)The plan will be adopted by the politicians in

May or June this year. We have no idea if we getthe finances to implement the plan.

Particle filters on municipal vehiclesParticles can be filtered from the exhaust of

diesel vehicles by a particle filter. The effi-ciency is 80% - 99% of all particles – includingthe ultra fine. The price for a filter inclusive in-stallation is between €3,000 – €7,000 depend-ing on the vehicle.

In 1999 Copenhagen decided that all our owndiesel cars and cars used by our contractors etc.should have particle filters. It has taken fiveyears to implement this decision, so now thereare particle filters in 90% of our own cars and in96% of our own machines. We also require theuse of particle filters to be included in everymunicipal contract and agreement. But there isstill need for focus in this area.

Environmental zone in half of the cityIn 2003 Copenhagen applied to the Ministry

of Justice for permission to create an environ-mental zone as a three year pilot project. Heavydiesel vehicles over 3½ tonnes need to have in-stalled a particle filter to get permission to driveinside the zone, which is half of the city.

The goal for this project is to see, if an envi-ronmental zone is a proper tool to limit the airpollution, in particular ultra fine particles causedby transport with diesel vehicles. The systemmust be easy to communicate and control withessential effects on air pollution and health.

The expenses for the transport business arecalculated to lie between 0.5 - 1 million DKK.The health benefits due to less early deaths etc.are calculated to lie between 1 and 5 millionDKK. So, overall a good project for society.

Findings

Make plans and strategiesMaybe this don’t provide resources in the first

place, but it can be a tool for allocating new re-sources to actions aimed to bring down pollution

Order in your own houseIt is a hard job to get the environment priori-

tised when in competition with schools, healthcare etc. But necessary, if you have to convincethe public and the industry to do better

Co-operation between politicians, public ad-ministration and other stakeholders. Identifyand showcase visible projects. Use simple argu-ments and reliable data. This can help gettingacross the main message and relevant argu-ments to citizens, businesses and the commu-nity in general.

Finn Terp, Environmental Planner, ArchitectMAA, Environmental Protection Agency, Cityof Copenhagen, Kalvebod Brygge 45, P.O. Box259, DK-1502 Copenhagen V, Denmark.Tel.: +45 3366 5877, E-Mail: fiterp@mff.kk.dk Information about air pollution in Copenhagenand links to air pollution in Denmark can befound on our web side www.miljoe.kk.dk

This paper was presented at Sherkin IslandMarine Station’s 21st Annual EnvironmentalConference in April 2005.

Page 4 ....................................................................................................................................................................Sherkin Comment 2005 – Issue No. 40

The Problems Facing Copenhagenfrom Transport Pollution

Sherkin Comment 2005 – Issue No. 40 ....................................................................................................................................................................Page 5

By Caroline O’ReillyUNTIL the mid 1990’s most of Dublin’s

wastewater was pumped to a primary treatmentfacility at Ringsend. Sludge produced as a by-product of this primary treatment was shippedout to sea in “sludge boats” where it wasdumped in the Irish Sea. Despite being anenviable resource at the heart of the city fornumerous marine activities, Dublin Bay didnot have an enviable reputation. Public pres-sure as well as various legislative instrumentshave changed this situation dramatically.

The EU Urban Wastewater Treatment Direc-tive (1991) was transposed into Irish law on14th December 1994 by S.I. no 419/1994Environment Protection Agency Act, 1992

(Urban waste water treatment) regulations,1994. This piece of legislation is probably themost important tool in improving the waterquality of both sensitive and coastal areas. Thistogether with the EU ban on marine dumpingof sewage sludge meant that wastewater treat-ment standards had to be significantlyimproved, not only in Dublin but across thecountry.

The bathing water Directive (76/160/EEC)also provides for monitoring of the water qual-ity at designated bathing areas in Ireland. Thepurpose of the directive is to ensure that thequality of bathing water is maintained and,where necessary, improved so that it is in com-pliance with specified standards designed toprotect public health and the environment.

In general, the quality of Ireland’s bathing

waters is of a high standard, according to find-ings released by the Environmental ProtectionAgency (EPA) in May 2005. The EPA’sBathing Water Report 2004 also points to thepositive impact of wastewater treatment facili-ties on bathing water quality.

Bathing waters are assessed for compliancewith two sets of EU standards: minimum qual-ity standards (EU Mandatory Values) and morestringent quality targets (EU Guide Values).The EPA also monitor compliance with addi-tional parameters set by Ireland (NationalLimit Values) to examine areas such as watercolour, transparency, faecal streptococci anddissolved oxygen.

The blue flag Scheme is a voluntary schemeadministered in Ireland by An Taisce and atEuropean level by the Foundation for Environ-mental Education in Europe (FEEE).

According to the EPA the bathing areas thatshowed the most notable water qualityimprovement were Malahide, Portmarnock,and Dollymount. Due to tidal movements inthe bay, Dollymount strand is the beach mostdirectly affected by the Ringsend treatmentworks and effluent quality.

Construction on the upgrade to the Ringsendtreatment works commenced in October 1999and the official opening of the plant was heldin June 2003.

The plant provides preliminary treatment inthe form of screening (6 mm fine screens) andfats, oil, grease and grit removal, and primarytreatment in the form of sedimentation, usingLamella plate settlement technology. The set-tled wastewater is pumped to 24 sequencingbatch reactors (SBR’s) for secondary treatmentto achieve Biochemical Oxygen Demand(BOD)/Chemical Oxygen Demand (COD)removal and partial nitrification. The SBRs atRingsend are the largest in the world and,uniquely, are contained in a two storey struc-ture due to site limitations.

During this secondary treatment, settledsewage is exposed to a dense microbiologicalpopulation (activated sludge) under aerobicconditions in an aerated tank. Microorganisms(mainly bacteria) convert soluble and colloidalorganic matter (food) into new cells (biomass),energy and carbon dioxide.

Aeration and mixing of activated sludgetogether with incoming flow of sewage (food)provide excellent condition for a wide varietyof microorganisms (see below). The predomi-nant type of micro-organism depends on (i)The influent wastewater (ii) Plant operationalmode (iii) Process design.

The Ringsend Plant provides tertiary waste-water treatment in the form of a state of the artUltra Violet (UV) Radiation Plant. This UV

plant, through its 1000 lamps and 5 flow con-trolled channels, is responsible for thesterilisation of the final effluent. Whenexposed to UV-C light, microorganisms areinactivated within seconds through a physicalreaction with the organism’s DNA. They losetheir ability to reproduce and are considereddead. Using UV treatment as a disinfectionmethod eliminates the introduction of chemi-cals into the water, thus eliminating the needfor further post-treatment of the water. The UVdosing is linked into the plants main SCADAsystem where dosage rates can be controlledand monitored by the computer system in rela-tion to the wastewater flow through the plant.During the summer months the plant will berun 24 hours a day and daily monitoringupstream and downstream of the plant willdetermine the efficiency of the radiation effect.To ensure the effectiveness of the UV plant itis essential that the other upstream processesi.e secondary biological treatment in sequenc-ing batch reactors, on the plant are workingeffectively and are continuously monitored.

Final effluent quality is monitored rigorouslyonsite with strict compliance standards beingconsistently met. Compliance limits are 25mg/l BOD, 125 mg/l COD, 35 mg/l TSS and18.75 mg/l Ammonia. To achieve these stan-dards the plant must remove >95% of theorganic pollutants present in the wastewater.During the bathing season, a further bacterialstandard is imposed. This standard of 105 faecalcoliforms/100ml is achieved consistently bycareful use of the UV tertiary treatment plant.

Less than 2 years after the official openingof the Ringsend WwTW, operational perform-ance results are promising and the bestaccolade to this is the announcement by theEPA of the Blue Flag award to Dollymountstrand at the beginning of June 2005.

Caroline O’Reilly, Celtic Anglian Water,Ringsend Waste Water Treatment Works,Pigeon House Road, Ringsend, Dublin 4,Ireland.

ProvidingClean Waterfor Dublin Bay

Ringsend Wastewater treatment works

Some of the bugs in activated sludge: A; nitrifiers,B; Rotifers, C; stalked ciliates, D; Free swimmingciliates.

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Page 6 ....................................................................................................................................................................Sherkin Comment 2005 – Issue No. 40

By AnthonyToole

NUMBERING from thelow teens to the high twenties,depending on the tides, theFarne Islands rise from thecold waters of the North Sea,between one-and-a-half andfive miles from the Northum-berland coast. They are themost easterly remnants of thedolerite intrusion known as theGreat Whin Sill, whichappears sporadically acrosseighty miles of northern Eng-

land. Some of the islands areno bigger than rocks, pokingjust above the swell. Othersare cliff-bound, or rise as tallstacks to heights of more thantwenty metres.

In 678 AD, St Cuthbertretreated from the monasteryon Holy Island to live as a her-mit on Inner Farne, where hestayed for most of the last nineyears of his life. For manycenturies afterwards, InnerFarne was a place of pilgrim-age.

The rocks were always adanger to shipping, and light-houses have been built onseveral of the islands at vari-ous times. The most famousincident involved the wreck ofthe SS Forfarshire, in 1838,when Grace Darling, the 22-year-old daughter of thekeeper of the Longstone light-house, twice braved thestormy sea in a rowing boat torescue survivors. Sadly, Graceenjoyed her fame for only ashort time, dying of tuberculo-sis in 1842. Her quiteelaborate tomb stands in StAidan’s churchyard in nearbyBamburgh.

Lighthouses still occupyLongstone and Inner Farne. Infact the Longstone is said tohave the most powerful lightin Europe. Nowadays, how-ever, the lighthouses areunmanned. The only perma-nent inhabitants are the birds.

Much of the Farne islandsconsists of bare rock, withonly a coating of lichens andhardy sprigs of grass or salt-tolerant flowers sheltering incracks. Where Ice Age glaciershave deposited boulder clay onthe larger islands, a thin layerof peat has developed, whichsupports a few small shrubs,but extensive carpets of seacampion, thrift and scurvygrass. In fact, nearly 120species of plant have beenrecorded here.

There is little in the way ofsand, the largest of only threebeaches being on Inner Farne.This, however, is where mostof the terns are found. Morethan 2000 pairs of Sandwichterns nest here, and often aneven larger number of Arcticterns. In contrast, and despitetheir name, there are only afew hundred common terns,while roseate terns can becounted in single figures.

These are aggressive birdsand readily dive-bomb anyone

who approaches their nests.This is sometimes a problem,as Inner Farne is one of thefew islands on which peopleare allowed to land. Visitorsneed to wear some form ofheadgear to avoid pecks fromthe rapier-sharp beaks.

The terns all fly south forthe winter, most to Africa,though one ringed bird isknown to have travelled as faras Australia. Some individualArctic terns have bred success-fully on the Farne Islands forover twenty years.

More than 270 species ofbird visit the Farnes, most ofthem during migration.Around fifteen species nesthere regularly, including gulls,shags, cormorants and auks. Inaddition, among occasionaland unexpected nesters arelapwings, moorhens, wagtails,blackbirds, wheatears andmeadow pipits.

Around 250 pairs of cor-

morant breed across several ofthe islands, with more thantwice that number of shags onStaple Island alone. The popu-lation of kittiwakes is now inthe thousands. Their nestsoccupy tiny, precarious ledges,

and often appear to be juststuck onto the bare, verticalrock.

The most abundant birds arethe auks. Though there are rel-atively few razorbills, thenumber of guillemots is now

Birds of the

Nesting shag.

Tern colony, St Cuthbert's Cove, Inner Farne.

Nesting kittiwakes.

The Longstone lighthouse.

Guillemot with sand eel.

Puffins, Staple Island.

Crowded nesting on The Pinnacles, Staple Island.

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Too

le

approaching 20,000 pairs.Huge colonies crowd with lit-tle space to spare along flatledges on Staple Island and thenearby rock stacks known asThe Pinnacles. Almost twiceas numerous are everyone’sfavourites, the puffins, whichnest wherever there is suffi-cient depth of soil to dig aburrow.

Though these populationsappear healthy at present, con-cern has been expressed attheir fluctuations in recentyears, not just on the FarneIslands, but elsewhere alongthe whole of the North Seacoast. Over the past fortyyears, possibly as a result ofglobal warming, cold-waterplankton species in the easternAtlantic have migrated northby ten degrees of latitude(1000 kilometres). Thisappears to have affected thesandeels on which many of thebirds depend for food. 2004saw a near catastrophic fall inbird numbers around someparts of the North Sea. Manydead fulmars washed up on theNorth-east coasts of Britainwere found to have died ofstarvation. Scientists of theDove Marine Laboratory at theUniversity of Newcastle uponTyne continually monitor thebird populations around theFarne Islands.

The grey seal colony is oneof the most important in theBritish Isles. The seals tend to

congregate on the smallerrocks of the archipelago, butcan be readily approached in aboat. In fact they will oftenswim close to boats and poptheir heads out of the water inapparent curiosity.

Until the end of the nine-teenth century, seals werehunted on the Farnes for theirskins and oil, and numbers fellto about a hundred. Todaythere are around 3500 individ-uals. About a thousand pupsare born each year, though thefierce North Sea storms canoften lead to only a 50% sur-vival rate.

Small boat trips to andaround the Farne Islands leavethe nearby fishing village ofSeahouses most days fromApril to September. The out-ward journey reveals some ofthe spectacle of this historiccoastline. To the north is HolyIsland, while the west is domi-nated by the impressivestructure of Bamburgh Castleand the Cheviot Hills in thedistance.

Landings on Inner Farneand Staple Island depend onthe weather, and restrictionsare imposed to keep visitornumbers down during thebreeding season, from May toJuly. Whether one lands or not,these trips are magic for theproximity to which one canapproach huge numbers of seabirds and seals. And there isalways the possibility of an

extra touch of magic in thatone of the many dolphins thatfrequent the Northumbriancoast might accompany theboat back into Seahouses har-bour.

M.A. Toole, 65, CheswickDrive, Gosforth, Newcastleupon Tyne, NE3 5DW, U.K.

Sherkin Comment 2005 – Issue No. 40 ....................................................................................................................................................................Page 7

Guillemots, Staple Island.

Sea Campion.

Grey seals.

Farne Islands

Page 8 ....................................................................................................................................................................Sherkin Comment 2005 – Issue No. 40

If you are burning your waste athome, you need to STOP!

Many people in Ireland burn waste on theirown property.

The materials burned are varied and includepaper, cardboard, textiles, timber, food, gardenclippings, synthetics such as plastic and evenglass, metal and household chemicals.

This ‘backyard burning’, as it is known, ismistakenly seen as a cheap method of keepingwaste out of already overflowing landfills andmany presume that it is not harmful to theenvironment. Nothing could be further fromthe truth. Practically all uncontrolled low tem-perature burning of waste releases toxicpollutants directly into the air without treat-ment or filtering. This is one of the majorsources of some pollutants impacting on airquality in Ireland today.

Almost 73% of the dioxins emitted to air inIreland came from the uncontrolled, low tem-perature burning of waste. This makes backyardburning of waste the single biggest source ofdioxins released into the Irish environment.

Surely it doesn’t do any harm?...

If this is what you believe then you needto read on.

Uncontrolled, low temperature burning ofmunicipal waste can impact on human health,food safety and the environment. In fact thisuncontrolled “backyard burning” of municipalwaste is far more damaging than previouslythought. Current research indicates that whenmunicipal waste is burned, in piles in the open,in barrels or open pits, or in commercially avail-able home incinerators, toxic pollutants arereleased into the air.

How bad can it really be?…..The amount of toxins released from uncon-

trolled low temperature burning in backyardsdepends on the composition of the waste beingburned, the temperature of the fire and the sup-ply of oxygen. The major problem withbackyard burning is that it is rarely carried outat high enough temperatures to destroy toxicsubstances. Under calm weather conditions tox-ins released from this type of uncontrolled lowtemperature burning can remain at dangerouslevels near the ground for a long time, causinghigh amounts of contamination at source.Below is a list of pollutants that can potentiallybe generated by uncontrolled low temperatureburning:

• Dioxins and furans, some of which are clas-sified as carcinogenic (i.e. they can causecancer).

• Volatile organic compounds (VOCs), which

can aggravate respiratory and heart illnessesand lead to kidney and liver damage. Theyalso contribute to the formation of ground-level ozone (photochemical smog).

• Polycyclic aromatic hydrocarbons (PAHs),which are generated when elements ofmunicipal waste are not completely com-busted. PAHs are known carcinogens.

• Carbon monoxide (CO), small amounts ofwhich can cause nausea and headaches wheninhaled. CO contributes to the formation ofharmful low level ozone.

• Hexachlorobenzene (HCB), which has simi-lar properties to dioxins as it is persistentand builds up in humans and the environ-ment. At certain levels of exposure it maycause serious health problems such as can-cer, kidney and liver damage.

• Nitrogen oxides (NOx), which contribute toacid rain and the formation of ground levelozone. Short term exposure to very highconcentrations of Nitrogen Dioxide (NO2)can result in adverse effects on the respira-tory system.

• Microscopic particles, which can be smallenough to get deep into our lungs. They areassociated with health problems includingbronchitis, asthma and heart attacks. Peoplewho already have respiratory or heart prob-lems, the elderly and infants are most at riskwhen exposed to these particles. These par-ticles are known to transport dioxins in theenvironment.

• Ash, which may contain mercury, lead andarsenic. These are toxic to humans and ani-mals when consumed, causing heartproblems, kidney and brain damage. Ifdeposited in the garden, vegetables canaccumulate them and they can then bepassed onto humans when eaten.

But I Thought Dioxins only comefrom Incinerators?

Wrong!Dioxins and Furans are chemical compounds

released during the combustion of most sub-stances when chlorine is present, especiallyplastic and rubber but even ordinary paper andnewspaper. When dioxins are released theydecompose so slowly that they become persist-ent pollutants in the environment for manyyears. Once dioxins enter the environment orbody, they persist due to their chemical stabilityand can accumulate in fat in animals andhumans. Some dioxin compounds are toxic andexposure to high levels has been linked withchloracne (skin lesions). Also, a particulardioxin, TCDD, is recognised as being the mosttoxic and has been classified as a known humancarcinogen (cancer causing).

Where exactly are dioxins comingfrom in Ireland?

Dioxins in the Irish environment primarilyresult from incomplete combustion of wastes,and the main source of dioxins according to theEnvironmental Protection Agency (EPA) isfrom uncontrolled burning of domestic waste.The EPA estimated that 93g of dioxins weregenerated in Ireland in 2000. Of this, 73% ofemissions were generated by uncontrolled com-bustion activities. The principal such activitiesare the domestic burning of waste (accountingfor 58% of emissions) and accidental buildingfires (accounting for 11% of emissions).

Dioxin emissions are projected to increasefrom 93g in 2000 to 110g in 2010. Uncontrolledcombustion activities will continue to be thelargest contributor of dioxins to the Irish envi-ronment – even if all of the planned municipalwaste incinerators are constructed and operat-ing. The construction and operation ofincinerators for municipal and hazardous waste,as proposed in regional and national plans, areforecast to contribute 1.8% of projected dioxinemissions to air in 2010. Uncontrolled burningis projected to account for 84% of such emis-sions. The dioxins identified as being emittedfrom waste incineration and ending up in landare those dioxins contained in the ash arisingfrom the burning of the waste. This ash can betreated and isolated from the general environ-ment by deposit in secure landfill facilities.

So why are we building Incinerators?There is no comparison between uncon-

trolled, low temperature burning of wasteand the controlled and regulated high-tem-perature conditions under which incineratorsoperate. In fact, the dioxins emitted from theuncontrolled burning of one tonne of house-hold waste (the average level of annual wasteper household in Ireland) are 55 times greaterthan the dioxins emitted if the same tonne ofwaste was treated in a modern municipalwaste incinerator.

The temperature at which incinerators oper-ate is a key factor distinguishing such facilitiesfrom uncontrolled backyard burning. Modernmunicipal incinerators are designed to burnwaste at temperatures in excess of 850°C and atthese temperatures dioxins are destroyed. Inaddition, modern incinerators have very effi-

cient flue gas cleaning technology which meansthat most of the pollutants produced when wasteis burned are not released to the atmosphere.

In contrast, uncontrolled low temperatureburning of waste occurs at a temperature ofabout 200 - 400°C, the temperature at whichdioxins are formed. All pollutants produced arethen released directly into the environment withno treatment or filtering.

Incineration is not the full answer to ourwaste challenge. However, as part of an overallwaste management strategy, as reflected in theEU Waste Hierarchy, incineration coupled withwaste prevention, reduction, recycling andother treatment methods, has an important roleto play.

In a report published in 2003, the Food SafetyAuthority of Ireland indicated that properlymanaged incineration facilities will not con-tribute to dioxin levels in the food supply to anysignificant extent and will not affect food qual-ity or safety, human health or the environment.

What can we do?Ireland is moving towards more sophisticated

management of waste with a high emphasis onreducing the amount of waste we produce,recycling as much as possible, thermally treat-ing waste that cannot be recycled andminimising landfill. While all waste manage-ment options impact on the environment, thisintegrated approach means that impact is kept toa minimum. Uncontrolled, low temperatureburning of waste impacts on the environmentmore than any other waste management option.

We must stop this practice NOW.A modern municipal incinerator treating 1

million tonnes of waste in controlled condi-tions, releases just 0.54 grams of dioxins to theatmosphere. A recent EPA report (2001) esti-mates that 60,000 tonnes of waste burned in theback yard produced 18 grams of dioxins.

Printed with permission from the Departmentof the Environment, Heritage and LocalGovernment in the Race Against Waste.Produced by RPS Group, West Pier BusinessCampus, Dun Laoghaire, Co. Dublin.www.raceagainstwaste.ie

Backyard Burning– but it is what we have always done!

Over 2.7 million tonnes of municipal (household and commercial) wastewas generated in 2001, an increase of 31.5% since 1998. This was theequivalent of almost 700kg of municipal waste for every person in Ireland.Some of this ends up being burned in backyards.

Sherkin Comment 2005 – Issue No. 40 ....................................................................................................................................................................Page 9

A Spotlight on World Environmental Mattersby Alex Kirby

No Progress on Climate ChangeThe G8 set-to at Gleneagles in July did

make some progress on Africa, if lessthan many had hoped and a few had pro-claimed. But on climate change it wasdisappointing. True, it set a date for aformal meeting between developed coun-tries which have ratified the KyotoProtocol and developing giants like Chinaand India, which haven’t ratified it andare not yet within its ambit. That’s worth-while, but it’s not world-changing. For allthe diplomacy, no new targets, timetablesor money emerged from Gleneagles, norany hint of urgency. And the problem isnow so urgent it demands action withoutdelay, most scientists agree.

Flying Fish off British CoastIt could be coincidence, of course, but

a species found normally in warmersouthern seas has been reported twicefrom British coasts recently. Flying fishare familiar to visitors to places like theCanaries. But an adult was spotted offDevon, and a schoolboy netted (and thenreleased) four infant fish which he andhis mother are convinced were also fly-ing fish. That was at Colwyn Bay, inNorth Wales, a long way north for thespecies.

Importing Gray WhalesThe Irish Sea could in a decade or so

be a livelier (and more crowded) placethan today, if two scientists from theUniversity of Central Lancashire havetheir way. They propose importingaround 50 gray whales from the popula-tion which breeds off California andMexico, to be the nucleus of a whale-watching industry in north-west England.There used to be gray whales in Euro-pean seas till they were exterminated bythe hunters several centuries ago. Thescientists think the imports could sur-vive and thrive, and even spreadelsewhere in Europe. The West Coastgrays were reduced by the whalers toabout 160 animals in the nineteenth cen-tury, but are estimated now at morethan 20,000. They’re docile and friendly,and even at 40 tonnes and up to 50 feetcould (the scientists say) be safely flownfrom California to the UK. Their 12,000-mile annual round trip from theirbreeding grounds to feed in the Arcticcould leave some disappointed would-bewhale-watchers, though.

Test-tube Sharks in AustraliaAustralia is trying a different way of

conserving marine life — test-tubesharks. The young of the endangered

gray nurse shark eat each other in thewomb, so Australian scientists plan toartificially inseminate females to savethe species, which faces local extinc-tion in 20 years. It is called the“labrador of the sea” from its docility.The sharks have two wombs, in which adominant pup will consume its siblings,leaving only two surviving pups everytwo years when the shark breeds. Arti-ficial insemination won’t stopintra-uterine cannibalism, so marinescientists plan to breed the embryos inindividual test tubes, until they haveoutgrown their cannibal phase and cansurvive safely in artificial wombs.

African Elephants on the IncreaseFor some African elephants, the news

is good. IUCN-The World ConservationUnion says that between the late 1990sand 2002 savannah elephants in thesouth and east of the continentincreased by about 4.5% a year, fromaround 283,000 to nearly 355,000. Insouthern Africa densities have been ris-ing for a century, so much so that somecountries now want an elephant cull,arguing that their success threatensother species and whole habitats. Thesmaller population increase in easternAfrica suggests that poachers anddrought may now be less of a threat thanthey were, though the elephants’ recov-ery is still fragile. But there are no hardfacts for west and central Africa, wheremost of the continent’s forest elephantslive, and where there is no let-up in thedemand for bush meat and ivory.

Bears make a comebackin Switzerland

Just over a century after the lastbear was killed in Switzerland, it looks asif the species could be preparing for acomeback. Three people have said theysaw a brown bear high in the Alps ofeastern Switzerland, near the borderwith Italy, where the animals are alreadyestablished. The Swiss are keen to seethem return, and earlier this year theystarted setting aside land which theyhoped might provide a corridor for bearsto migrate from Italy. The three saidthey had watched the bear for 20 min-utes through binoculars from a distanceof 600m. But the light was too poor forphotography. Reintroduced lynx areviewed with suspicion by Swiss farmers,and a wolf which wandered in fromFrance was found dead not long after-wards.

Sheep Dip ConcernsConventional organophosphate sheep-

dips, which are derived from Nazi nervegases, are known to damage the nervoussystems of susceptible people. Now a UKcharity, Buglife, the Invertebrate Con-servation Trust, says some supposedlybenign replacements for OPs are them-selves unacceptable, because they killwildlife. It says synthetic pyrethroidsare poisoning rivers and damaging terres-trial ecosystems. Buglife sayspyrethroids are a thousand times moretoxic to wildlife than OPs, with a tinyamount dripping from the fleece of adipped sheep capable of killing all inver-tebrates up to six miles downstream.Over 400 million litres of used dip aresprayed annually on British fields. Buglifesays this will reduce the availability offood for breeding birds and kill off theinsects needed to pollinate flowers.

“Superweed” at GM Trial PlotThere was dismay in the UK over

reports that a study had found a so-called “superweed” growing at a site

where a trial plot of genetically-modi-fied crops had been sown. A charlockplant, a relative of oilseed rape, failed toshrivel up when treated with the herbi-cide used to manage a GM crop grown inthe same field. Groups opposed to theuse of GM technology have feared forsome time that wild plants which developthe characteristics of biotech cropscould emerge. But researchers say theirwork shows there is only a slim chance ofsuch transfers happening. And they saythe study reinforces the belief that theenvironmental impact of GM crops isnegligible. Dr Les Firbank, who headedthe consortium of scientists on therecent UK Farm-Scale Evaluations(FSEs) of GM plants, said: “Herbicide-tolerant weeds tend to under-performcompared with wild type, so unless all itscompetitors have been sprayed out withthe same herbicide, [the charlock] won’tthrive.”

Alex Kirby is a former BBCenvironment correspondent, nowwriting and broadcasting onenvironment and development.

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Introduction There are seven species

of sea turtle but only oneof these, the LeatherbackTurtle, occurs regularly inIrish waters. As reptiles,sea turtles are ‘coldblooded' and are unableto control their body tem-perature. They are foundmainly in tropical, sub-tropical and warmtemperate waters. TheLeatherback is an excep-tion and studies haveshown that it can main-tain its body temperatureas much as 18oC abovethat of the surroundingwater. Sea turtles areadapted for a life in theopen ocean and mostspecies travel long dis-tances during their annualcycle, moving betweennesting areas and feedingzones. All except theLeatherback have a hardshell for protection andall species have long frontflippers for swimming.Whilst sea turtles breathe

by means of lungs andneed to come to the sur-face for air they canremain submerged forlong periods and are evenknown to hibernate inmud on the sea bottom.Over the last few decadesthe numbers of sea turtleshave diminished greatlythroughout the world’soceans and most speciesare now considered to beendangered and underthreat of extinction.

Leatherback Turtle The Leatherback Turtle

is unique among sea tur-tles in having a rubberycarapace with seven lon-gitudinal ridges instead ofa hard shell and is by farthe biggest living sea tur-tle. The largest specimenever recorded was a malefound entangled in a buoyrope at Harlech, NorthWales, in 1988. It meas-ured 2.91m in length andweighed 916 kg. Adultfemales normally weigh

up to 500 kg.Leatherbacks have a thickoily layer under their skinand a unique physiologyto protect them from thecold and this allows themto penetrate even Arcticwaters in search of theirpreferred food – jellyfish.

There are 682 recordsof Leatherbacks occur-ring in Irish and UKwaters during the period1960–2004,161 of thesefrom Irish waters.Leatherbacks are mostabundant along the south

and west coasts. It isundoubtedly the abun-dance of jellyfish in ourwaters that attractsLeatherbacks. Recentstudies in the Irish Seahave linked the occur-rence of Leatherbacks incertain Welsh bays(Tremadoc Bay, Car-marthen Bay) to theabundance of the BarrelJellyfish (Rhizostomaoctopus). Most sightingsare made in summer (July– October) with a peak inAugust.

Leatherbacks, likeother turtles, come ashoreon sandy beaches –mainly in tropical coun-tries – to lay their eggs,with important nestingareas found in Surinam,French Guiana, theCaribbean, Gabon andIndonesia. The eggs hatchafter about 60 days andthe juvenile turtles scurrydown to the sea in a‘frenzy ’to avoid preda-tors. The Leatherback is avery ancient specieswhich has been in exis-tence for 100 millionyears, but sadly it is nowthreatened with extinc-tion and only 25,000breeding females arethought to remain, downfrom 115,000 in 1980.Heavy mortality occursas a result of commercialling-line and gill net fish-eries. It also suffers frompersecution on the nest-ing beaches and marinepollution such as plasticbags, which it swallowsin mistake for jellyfish.

Loggerhead Turtle The Loggerhead is a

medium to large sea turtleweighing up to 277 kg(normally 80-180 kg). Ithas a large head withheavy jaws adapted tocrushing shellfish andcrabs, its main diet. Since

1960 it has been recorded31 times in Irish waters.Specimens stranded orcaptured alive in a weakcondition have been reha-bilitated at the NIAquarium or at Ocean-world, Dingle, and laterreleased off Madeira orthe Azores. Loggerheadsoccur throughout thetropics, subtropics andwarm temperate watersand have the widest geo-graphic range of any seaturtle. They nest in greatnumbers in Florida(21,000 females) and arethe commonest turtlefound in the Mediter-ranean, with about 2,500females nesting inGreece, Turkey andCyprus.

Kemps RidleyTurtle

This is a small sea tur-tle weighing about 50 kgand one which is mostlylimited to the Gulf ofMexico. Juveniles rangebetween tropical and tem-perate coastal areas of thenorth-west Atlantic andsix individuals have beenrecorded as strandings inIrish waters (one since1960). The Kemps Ridleyis the rarest and mostendangered of all sea tur-tles with a nestingpopulation of only 3,000females. It nests twiceevery season, en masse,with hundreds of turtlesarriving on the beach atthe same time (arribadas).

Hawksbill Turtle The Hawksbill is so

called on account of itshawk-like bill. It pos-sesses a beautifulpatterned shell and hasbeen persecuted for cen-turies for the trade intortoiseshell. This is the

most tropical of all seaturtles and is typicallyfound around coral reefs.The Hawksbill’s narrowhead and jaws allows it toobtain food from crevicesin coral reefs. It feeds onsponges, anemones, softcorals, squid and shrimp.The Hawksbill isextremely rare in Euro-pean waters and the onlyrecord for Britain and Ire-land is an individualwhich was caught in her-ring nets off CorkHarbour in 1983. Themost important nestingpopulations are foundalong the Great BarrierReef (Australia), inIndonesia, in the IndianOcean and the Caribbean.

Other Turtles The Green Turtle is

unique amongst sea tur-tles in having aherbivorous diet: it feedsmainly on sea grasses. Itis a large turtle that iswidely distributedthroughout the tropicsand subtropics. It hasbeen recorded seventimes from Britain but hasnever been found in Irishwaters. The Olive Ridley,similarly, occurs widelythroughout tropical andsubtropical seas but hasnever been recorded here.Despite its relativelylarge population (about 2million nesting females)it is vulnerable as it nestsin dense concentrationson a small number ofbeaches (e.g. in CentralAmerica and India). Theremaining species, theFlatback Turtle, is foundonly along the northerncoast of Australia andunlike other turtles doesnot venture into the openocean. The Flatback laysfewer eggs than other tur-tles but they are large inrelation to its body size.

Threats to SeaTurtles

The number of sea tur-tles has declinedworldwide due, prima-rily, to human activity.Many nesting sites havebeen lost to developmentas sandy beaches areturned into tourist desti-nations. Artificial lightfrom coastal develop-ment disorientates

nesting turtles and they –and their hatchlings – getlost as they make theirway to the sea. Deliberatepersecution of turtles onnesting beaches and har-vesting of their eggs hasled to a decline of turtlepopulations in manyareas and their extinctionat a regional level (e.g.Malaysian leatherbacks).Commercial fishingactivities are a majorthreat to turtles. It is esti-mated that 250,000loggerheads and 60,000leatherback turtles areinadvertently snared eachyear by long lines, withtens of thousands dying.Entanglement in coastalfishing gear is also aproblem. About 23%ofturtles found in Britishand Irish waters (n =104)were reported entangledin buoy ropes of shellfishpots, caught in fishingnets or on hook and line.Plastic bags, styrofoamfragments, balloons, tarand other marine debrisis often swallowed byturtles in mistake forfood, blocking theirdigestive tracts and caus-ing death.

Where to ReportTurtle Sightings Any sightings, strand-

ings or accidentalcaptures of sea turtlesshould be reported to thefollowing: Republic ofIreland: Prof John Daven-port (UCC) 021-4904140(work) 021-4897392(home) Northern Ireland:Ulster Museum 02890-3831144 (all records)Portrush CountrysideCentre 02870-823600(live records/entangle-ments)

It’s easy to makea difference

This is part of an Enfoleaflet. The full leafletand many others relatedto different aspects of theenvironment areavailable fordownloading on ENFO’swebsite. Contact details:ENFO – TheEnvironmentalInformation Service, 17St.Andrew Street, Dublin2, Ireland.Tel:1890 200191 Fax:(01) 888 2946 e-mail: info@enfo.iewww.enfo.ieENFO is a service of theDepartment of theEnvironment and LocalGovernment.

Sea TurtlesPage 10 ..................................................................................................................................................................Sherkin Comment 2005 – Issue No. 40

Leatherback Turtle

Sherkin Comment 2005 – Issue No. 40 ..................................................................................................................................................................Page 11

By Gerard O’LearyDOMESTIC wastewater con-

tains many substances that areundesirable and potentially harm-ful to human health and theenvironment. Local authorities,through the planning system, canensure that housing developmentsin suitable areas have minimalimpacts on water quality. In ourmost recent water quality report,published in May of this year, wewarned local authorities that the

risk presented by a proliferation ofon-site sewage treatment systemsneeds to be kept under surveillanceif increased groundwater contami-nation is to be avoided.

A variety of on-site systems areavailable in Ireland, the most com-mon system being theconventional septic tank system.There are over 350,000 of thesesystems currently installed in Ire-land. They consist of a septic tankand below surface soil disposalfield or percolation area. Othersystem types, collectively called

packaged secondary treatment sys-tems, take the form of mechanicalaeration systems, filter systemsand constructed wetlands.

The EPA has repeatedly statedthat in many cases a lack of under-standing of the treatment anddisposal processes involved insmall scale domestic wastewatertreatment has led to poor design,siting and installation of on-sitetreatment systems. To redress thissituation the EPA has publishedtwo guidance documents on theproper selection, design, operationand maintenance of these systemsto enable sustainable developmentto take place in Ireland. The guid-ance is not intended to suggest thatall housing development shouldconsist of one-off housing as engi-neering cannot be used assubstitute for poor planning.

A search on google.com usingthe words septic tank reveals oversix hundred and fifty thousandworldwide hits, a staggering num-ber. When you restrict the search toIreland there are over seventeenthousand hits alone. With the highnumber of websites it is not sur-prising that a number of mythshave crept in over the years. Thefirst hit on the Irish search is theShannon Regional Fisheries Boardwebsite (http://www.shannon-fishery-board.ie/aboutus/septic-tanks.htm). The EPA agrees withBoard that the main threats to theriver Shannon come from anincrease in the amount of nutrients,including phosphates beingreleased into the water. An excessof phosphates in the water leads toincreased algal growth which oftenresults in algal blooms in summer-time. The algae in turn uses upoxygen in the water reducing itscapacity to support fish life. Thephosphates come from a number ofsources including agricultural,industrial and domestic (includingon-site treatment systems such asseptic tanks).

Perhaps to counteract the num-ber of myths that have grown upwith these systems the website setsout the “do’s” and “don'ts “ of aseptic tank as follows:• DO consult the EPA Manual,

Treatment Systems for SingleHouses before constructing aseptic tank

• DO construct a tank and perco-lation area in accordance withregulations

• DO desludge when necessary

• DON’T site a septic tank or per-colation area within 10 metresof a watercourse or stream, or50 meters from a lake.

• DON’T allow pesticides, paints,thinners, solvents, disinfectants,or household hazardous sub-stances to discharge into the tank

• DON’T allow rainwater to enterthe tank.

With the large number of exist-ing on-site treatment systems inIreland, the EPA felt it necessity tocommission research on small-scale wastewater treatmentsystems in order to improve thefunctioning of wastewater treat-ment systems widely used across

the country and so protect waterquality. A number of research proj-ects have been awarded since themid 90’s.

The most recent researchinvolved a series of rigorous trialsof various wastewater treatmentsystems to assess the performanceof septic tanks and other small-scale secondary treatmentapplications. Researchers fromthe Environmental EngineeringGroup in Trinity College under-took the project, on behalf of theEPA.

The main findings from fourseparate field trials covering arange of different soil types over atwelve month period are:• The systems studied were all

capable of treating wastewaterfrom a domestic house.

• The conventional septic tankand percolation area provided acomparable performance to thepackaged secondary waste-water treatment system andpercolation area.

An interesting aspect of thestudy was the exposure of theResearchers to the existing prac-tice of on-site system installationamongst some practitioners in Ire-land. It seemed that commonpractice for builders is to divert atleast some storm water drains intothe septic tank, presumablybecause this saves on the expenseand time involved in laying extrapipework. This is disastrous assuch practices will impact signifi-cantly on the environment as thetreatment system will be incapableof handling the increased volumeof wastewater. This is akin to ask-ing a garden lawn mower to cutfields of silage. This observationprompts the need for closer super-vision of builders during theinstallation of such treatment sys-tems.

To conclude the EPA supportsthe view of Geological Survey ofIreland that groundwater is animportant resource in Irelandwhich is under increasing riskfrom human activities with con-tamination arising from both‘diffuse’ (generally agricultural)and ‘point sources’ again generallyfarmyards (manure and silage stor-age) and septic tank systems.Those who are responsible fortreating waste water on-site mustensure that the system is properlydesigned, installed and main-tained.

Gerard O’Leary, ProgrammeManager, Office of EnvironmentalAssessment, EnvironmentalProtection Agency, PO Box 3000,Johnstown Castle Estate, CoWexford, Ireland. www.epa.ie

On-site Treatmentof Waste Water

In Ireland there are currently over 350,000 on-site wastewater treatment systemsinstalled.

“Those who areresponsible for treatingwaste water on-sitemust ensure that thesystem is properlydesigned, installed andmaintained.”

Page 12 ..................................................................................................................................................................Sherkin Comment 2005 – Issue No. 40

By Declan T. Quigley & Gary Hannon

Threshers belong to a small familyof sharks (Alopiidae) which is repre-sented by a single genus (Alopias)and only three species. Although theyare a wide-ranging family, occurringworldwide in tropical, subtropical,warm and cool temperate seas, onlytwo species have been recorded fromEuropean seas: the moderately com-mon Thintail Thresher Shark or FoxShark (Alopias vulpinus) and themuch rarer Bigeye Thresher Shark (A.superciliosus). The Pelagic Thresher(A. pelagicus) appears to be absentfrom the North and South AtlanticOceans, but wide ranging throughoutthe Pacific and Indian Oceans.

Threshers are easily distinguish-able from other sharks by theirextremely long curving asymmetricalcaudal (tail) fin which is nearly aslong as the rest of the shark as well astheir large eyes. They are large,active, strong-swimming predators,ranging from coastal to offshorewaters, from the surface down todepths of at least 500m. Threshersappear to be specialised for feedingon small to moderately large school-ing fishes and squids. They have beenobserved, sometimes in pairs, swim-ming in circles around a school ofprey, narrowing the radius andbunching the school with their long,strap-like caudal fins which are thenused like a whip to stun and kill prey.

Thintailed Thresher(A. vulpinus)

The Thintailed Thresher Shark is awidespread species found virtuallycircum-global in oceanic and coastalwaters from the surface down to366m from tropical to cold-temperateseas but commonest in temperatewaters. In the eastern Atlantic it isfound from Norway southwards viathe British Isles to Madeira and theAzores, including the Mediterraneanand Black Seas.

In UK waters, the species occursfrequently during the summer andautumn off the south Cornish coast,as far east as the Isle of Wight, andoccasionally from the Pembrokecoast, but less frequently from the

North Sea and only very rarely inScottish waters. Considering the sig-nificant number of very small(91-152cm long) threshers caught byanglers during late summer in south-ern British waters, it is thought thatfollowing an inshore migration bysexually mature adults, the pups areborn during this time.

Mature threshers (females measur-ing 315-400cm; and males measuring314-420cm,) are ovoviviparous andproduce litters of only 3-7 fully-formed pups (measuring 114-160cm)after a gestation period of 9 months ininshore waters in the eastern Atlantic;the developing embryos are appar-ently inter-uterine cannibals(oophagous). Threshers reach maturityat an age of 3-8 years and are esti-mated to live up to 45-50 years.Although the largest authenticatedthintailed thresher recorded measured5.73m, there are unconfirmed reportsof specimens measuring up to 7.60m.The current UK rod & line caughtrecord weighing 146.5kg (captured offPortsmouth in 1982) is small in com-parison with the present IGFA World(Rod & Line) Record of 348kg (Bayof Islands, New Zealand, 1983). TheIrish specimen (rod & line) qualifyingweight is still unclaimed at 54.4kg.

Despite its apparent widespreaddistribution in the north easternAtlantic, there are surprisingly fewunequivocal records of A. vulpinusfrom Irish waters (Table 1). Apartfrom a few anecdotal references dur-ing the 1800s*, there are only ahandful of authenticated recordssince 1905, primarily from the westand southwest coast.

Although William Thompson (ANatural History of Ireland, Vol. 4 pos-tumately published in 1856),acknowledged McSkimmin’s andTempleton’s records, he cautiouslyremarked that the thresher “Can beannounced only on circumstantial evi-dence as frequenting the Irish coast.”He then went on to recount that“Major Walker, of The Lodge, CountyWexford, noticed this species in a let-ter written to me in July, 1846, fromthe statement of fishermen who hadseen a large fish beating a grampus orsmall whale in the Sound, between thetwo Saltee Islands, and who reportedthat every blow sounded like the dis-tant report of a canon.”

At a meeting of the Dublin NaturalHistory Society on the 9th February1854, Mr William Andrews “pre-sented the tail-fin of a fox shark, orthresher (Carcharias vulpes), takenfrom a fish captured in Dingle Bay. MrStopford informed Mr Andrews that heand the crew of his yacht had noticedthe thresher shark in Dingle Bay. MrR. Callwell mentioned that in one ofthe tours of inspection in the BelfastOffice steam vessel, he had visitedCarlingford Lough in the month ofAugust. Herrings at the time wereplentiful in the Lough, and he hadnoticed a species of shark frequentlyspringing several feet out of the water,which the crew pointed out to him asthe thresher shark, from the peculiar-ity of the action of its tail-fin.”

In his Glances into the Ichthyologyof the County of Dublin (1866), HarryBlake-Knox remarked that thethresher “Is often very common in thisBay” and went on to state that “lastwinter I saw one rise and kill awounded diver with a slap of its tail,and then swallow it. When rising inthe water the thresher is known fromthe porpoise by its long dorsal fin(sic). I have frequently given athresher a charge of shot, and causedhim to jump clean out of the water.When up for sport they make a greatnoise by striking the water with theirtail. Have seen them of enormoussizes.” Ogilby (1885) was sceptical ofBlake-Knox’s report and noted “Thatno specimen has ever been capturedthere, and no competent ichthyologistever recorded it from so thoroughlywell-known a locality”. It is possiblethat Blake-Knox may have confusedthe thresher with the basking sharkwhich may have been relatively com-mon in the Irish Sea at this time. Thelatter species is frequently observedon the surface, has a large dorsal fin(the thresher’s is relatively small) andgrows to an enormous size.

Bigeye Thresher Shark(A. superciliosus)

The Bigeye Thresher Shark is awidespread but infrequently caughtspecies typically inhabiting oceanicand coastal waters from the surface todepths of 500m. Its distribution isconsidered to be virtually circum-tropical with a preference for warm

temperate to tropical waters. In theeastern Atlantic, it has been recorded,albeit rarely, southwards from theBay of Biscay. Only one specimenhas been recorded from Irish watersto date: during August 1995 a largefemale measuring 4.84m and weigh-ing 318kg (gutted) was captured in atuna drift-net set at a depth of 5m inwaters more than 2000m deep in thePorcupine Sea Bight area (51oN,13oW). This is the largest and mostnortherly authenticated specimen ofthis species to date.

It is possible that the BigeyeThresher Shark occurs more fre-quently in offshore waters off theEuropean coast than is currentlyknown, particularly during warmeryears. However, the subsequent EUban on tuna drift-netting will proba-bly preclude verification of this

hypothesis for the foreseeable future.Indeed, a number of other (primarilyepipelagic) species, previouslyregarded as extremely rare in north-ern European waters, were capturedin tuna drift-nets prior to the currentban on this politically and biologi-cally controversial method of fishing.

Since at least two species ofThresher Shark are currently knownto occur in Irish waters it is clear thatall specimens should be criticallyexamined in order to verify them tospecies level.

Declan T. Quigley & Gary Hannon,Dingle Oceanworld (Mara Beo Teo),The Wood, Dingle, Co Kerry,Ireland. Mobile: 087-9080521; Email: declanquigley@eircom.net

Thresher Shark(Alopias vulpinus)in Irish Waters

*In his History of Carrickfergus (1829), McSkimmin (1829) remarked that the thresher is “sometimes seen off the Copeland Isles; and heard afternight making a noise with its tail against the water.” Robert Templeton (List of Irish Vertebrates 1836-37) also mentioned that the species was“occasionally seen about the Copeland Islands” but concluded that it was “rare on the (Irish) coast.”

Thintailed Thresher Shark (Alopias vulpinus): female weighing c350-400kg andmeasuring 4.23m T.L. captured by MFV "Northern Celt" out of Dunmore East, CoWaterford during July 2005 (Photo: courtesy of Sean Doran, Howth).

Sherkin Comment 2005 – Issue No. 40 ..................................................................................................................................................................Page 13

By DaphnePochin Mould

I SAW it once – so long ago.I was eight or ten and it was theend of the twenties – hardly1930. From the blue sea, withthe horizon sharp against thesky, came a towering pyramidof white sails. It was headingwest down the English Chan-nel for the Atlantic. I was

wildly excited – would shecome close to land? The placewas Bournemouth and nobodyelse was bothered. I wonderedif she would shore at Poole?But she was a wind ship head-ing across the oceans longdistance, powered only by hersails and the wind on them. Noengine to get her out of trouble,too huge to make use of oars.She was the biggest wind shipI’ve ever seen.

Around the same time, in

Torbay in Devon, I saw theBrixham fishing fleet settingout with their red sails power-ing them along.

Much later, in the 1950s,some hookers still worked outof the Claddagh in Galway,and I went out in one with theDominicans for the blessing ofthe bay and the ships. I wenton the pilgrimage to St. Mac-Dara’s island, riding in one ofthe fleet of hookers, whichhaving landed their devoutcargo, set about the traditionalrace – and a Galway hookerracing under sail is some sight.

The glamour of the tradi-tional sailing ship is still withus and the interest is growing.One just had to witness thecrowds who came to Water-ford to see the Tall Ships, andthe start of the Tall Ships raceoff Hook Head – delayed fordays by lack of wind. If youcan, get yourself aboard a sail-ing ship, and feel hermovement through the seas. Itis so different from the enginedriven vessel forcing its routeagainst wind and wave. Themodern Tall Ships are beauti-ful replicas but not real windships, for they have engines tofall back on or make up time,or enter a tricky port. They arewarm and snug below, havetoilet facilities, good food,radio, GPS, a multitude ofnavigational aids, includingradar. And if things go reallywrong, help can come bothfrom the air and from ships inthe same area.

But none of these aids wereavailable to any of the world’sshipping for almost all ofhuman history. Only in theearly 19th century did crude,fuel-hungry steam enginescome aboard and laboriouslyturn paddle wheels. It wasanother hundred years beforeships began to carry radio anduse Mr. Sam Morse’s newcode. Had the “Titanic” saileda few years earlier, we wouldnever have known what hap-pened to her. Those faint dots

and dashes of the code broughtrescue ships to pick up sur-vivors. In the old days, in theopen ocean, you sank alone.Once a ship passed out of sightof land, there was no news ofher until she came to someport. In Brittany, there is across called the Widows’Cross, for here the wiveswould gather when the top sailschooner fleet came back fromthe summer fishing off Ice-land, and count the vesselsreturning and know how manywould not return.

Wind powered ships sailedand explored the world,mapped and discovered, car-ried armies to war and builtempires, carrying all the goodsand luxuries people wanted.From Cork, the “Ring MahonCastle” (whose log book sur-vives) was fast and she ranquickly to the West Indies forcoffee and sugar. Another littlebrig made its way to China toload up with tea. The Corkpapers would give notice ofher expected return, and thenof the date and place of the TeaAuction and of the many vari-

eties of China tea broughtback.

The wind ships are beauti-ful, from the fast, streamlinedViking ship to the chunky,colourful Spanish galleon, tothe crowded warships ofnavies, including the “woodenwalls” of England – Nelson’snavy, “heart of oak are ourships, jolly tars are our men”.“Beautiful ships but badlyfound” wrote one man whohad worked on them. Thosegreat sailing ships of the 19thcentury and early 20th – thekind I saw so long ago – mighthave been run by mean own-ers, with badly paid, badly fedcrews. Many were under-manned and clawed their wayround Cape Horn against con-trary gales, snow, ice,struggling with frozen sails.There were no safety harnessesin those days – if you fell, youfell. Comforts were none exis-tent, only the cook’s fire below,which was put out in really badweather (fire was the great haz-ard of wooden ships). Therewere no washing/toilet facili-ties and the food was bad.

A wind ship can stay at seaindefinitely while a power onemust stop for fuel. They carriedsalted and dry provisionsincluding salted “horse”, whichwas actually beef, pig in casks(Cork produced vast amountsof salt meat), “Liverpool pan-tiles” for bread, hard biscuitsmade of flour and water with-out fat so they could keepindefinitely (the modern “waterbiscuit” of our canapes is thesame mix), dried peas and oat-meal. Scourvy, due to lack ofvitamins was the scourge of

long distance voyages until itwas found that lime or lemonjuice would provide the essen-tial vitamin C.

The wind ships could mendthemselves to some extent. Bat-tle or storm damage to mastsand rigging could be repairedby handy men who could makesome sort of a “jury rig” andget the ship to a port.

Now with fossil fuels run-ning out, will the windpowered bulk carriers comeback, saving on the engine’sscarce fuel? Not the old tallship pattern, but using newmaterials for sails, with theircontrols linked to the weatherforecasts and GPS, and con-trolled by computer on a snugbridge. The wind still blows asstrong as ever it did: why notride along with it again?

Suggested further reading:Derek Lundy. “The Way of a

Ship” Jonathan Cape, London,2002. 445pp. An importantaccount of life on a wind shipin the last days of sail. Roundthe Horn in the worst ofweather, including fire at sea,disease and a history of longhaul sailing.

Sheila Mulcahy. “A GallantBarque” The story of the “PortYarrock”. The Kerryman,Tralee 1999. “Port Yarrock”was lost with all hands andstranded in Brandon in 1894.

Patrick O’Brien’s longseries of novels of the Britishnavy in Napoleonic times, area lively but genuine account ofwhat life was like then on afighting wind ship and how shewas sailed.

The Wind Ships

“Kathleen and May”restored in England returns to visit her old homeportof Youghal. She, and many other schooners like her, traded back and forthto England, and carried goods all around Ireland right into the 20thcentury.Till very recently, it was easier to go by sea than by land. Now thecoastal schooners’ work is done by big trucks on the roads.

The German “Gorch Fock” in Cork, a shot taken back in the 1960s.Square rigged on all three masts, she is, in the scale of names ofsailing vessels, a Ship.

The French Navy’s sail trainers are “Etoile” and “Belle Poule” and are topsail schooners, replicas of the greatBrittany fleet that each year sailed to Iceland to fish there all summer. Seen here leaving Kinsale harbour.

Deck,“Kathleen & May”

Phot

os: ©

Dap

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Poch

in M

ould

Page 14 ..................................................................................................................................................................Sherkin Comment 2005 – Issue No. 40

By Paddy LeahyTHE first settlers in Ire-

land established themselveson the coast, at the mouths ofrivers where there was shel-ter for their boats.Penetration inland wouldhave been initially by boaton the larger rivers, and allold towns and cities were onthe banks of rivers. The big-ger rivers were a transportsystem, a source of water,and a useful waste disposalsystem. As time went on andpopulations grew, bridgeswere built across rivers andthe towns expanded to caterfor the increasing industrialand commercial activities.

Approaching the modernera, buildings became moresubstantial and longer last-ing. Sometimes marshesalongside the rivers werefilled in and canalisation ofthe rivers was achieved bybuilding embankments alongthe river banks.

Historically, developmentshave contributed to riverflooding in a number ofways. Many of our oldbridges, built of stone in thenineteenth century or evenearlier, have substantial riverpiers which restrict the flow.Often too, such bridges haveapproach embankments onthe flood plain that restrictthe river flow or reduce stor-age capacity. It was onlynatural that large bridgeswould be built in or adjacentto towns, and as the townsexpanded, flooding upstreamof the bridge became a majorproblem. Before the 1964Planning Act, and even in theinitial decades after its intro-duction, developments alsotook place on river banks andincreased the flood risk inthe immediate vicinity.

Following calls from localauthority engineers and oth-ers, a more enlightenedattitude to flooding risks isnow taken, and proposals fordevelopment that wouldincrease flooding are eitherrefused permission or onlyallowed proceed if appropri-ate flood mitigationmeasures are put in place.New developments can

worsen flooding in a numberof ways. The flood plain canbe obstructed, either by thedevelopment itself, or evenby embankments built tokeep flood waters out of theproposed development. Alldevelopments increase theamount of impermeable sur-

faces, such as roads, pavedareas and roofs. This resultsin much faster run-off of rainwater, thus increasing therisk of floods.

Many rivers in Ireland, par-ticularly the larger ones, flowalongside substantial floodplains on their lower reaches.Such flood plains are formedover thousands of years bythe filling of the original rivervalley with gravel and siltwashed down from the uppersections of the river, wheresteep gradients cause rapidrun-off and contribute to theerosion of rocks and overbur-den. Thus flat areas canextend for considerable dis-tances on either side of thenormal river channel. Usuallyabove the normal water level,the flood plain is inundatedwhen particularly high floodlevels are reached.

Flood plains themselvescan carry a proportion of theflood flows. While the mainriver channel will take thevast bulk of a flood, the floodplain can have a significantadditional flow capacity,depending on the depth ofwater over the plain, andwhether or not there are anyobstructions. Obstructionscan consist of ordinary fieldboundaries constructed ofsod and stone or other mate-rials that will impede theflow of water. Even tall cropsor dense woodlands can sub-stantially lower the flowcapacity of a flood. Anyobstruction of the flow ofwater on a flood plain canreduce the capacity of theriver to deal with a substan-tial flood, and sometimes to aconsiderable extent.

In the development of theIrish road network in thenineteenth century, manybridges, sometimes withraised roads approachingthem, imposed considerablerestrictions on the floodplain. Quite often one canobserve in aerial photographs

of serious river flooding thebottleneck effect that a bridgecan have on floods. Althougha small nu