HODDER WATER TREATMENT WORKS STOCKS RESERVOIR.
HODDER WATER TREATMENT WORKSSTOCKS RESERVOIR.FISHERIES SECTIONRIVERS DIVISIONNOVEMBER 1984
AN INVESTIGATION INTO THE POTENTIAL LOSSES OF FISH ON THE FILTER PLATESAT THE HODDER WATER TREATMENT WORKS, STOCKS RESERVOIR.Stocks Reservoir is situated amidst the Forest of Bowland in the upperreaches of the old river valley of the Hodder.Located about 10 miles dueNorth of Clitheroe its altitude is only 100 metres higher than that of thisLancashire market town.The water levels altitude of 180 metres is notunduly high compared with other Pennine Reservoirs but the upland catchmentof moorland, reaching to over 500 m gives the reservoir truly oligotrophiccharacteristics.1.
CONTENTSPageIntroduction1Investigative Procedures5Fish Stocking5Anglers Returns6Treatment Plant Fish Plates6Plant Operational Alternatives8Valve Tower Specifications911Investigative FindingsFish Stocking11Anglers Returns12Treatment Plant Fish Plates14Physical and Environmental factorsaffecting fish ingress15Plant Operations Analysis17Fish Stocking2222Anglers Returns22Treatment Plant Fish Plates24Physical and Environmental factorsaffecting fish ingress26Plant Operations endicesReferences1,1 V VJ .bou w19 73 - 1 X1 .2Stocks A.C. circular3Fish return form5Wind speed and direction6Anglers Returns 1983 and 19847Population estimate8Fish densities9Stocks A.C. fish stocking record10Raw and compensation water quality11Fish stomach analysis
The reservoir was built in 1927 for the Fylde Water Board who primarilysupplied water to Blackpool.The catchment of 9283 acres was initiallycontrolled by the board, and more recently by the Water Authority, thepractices of which will not have unduly altered the water chemistry of thereservoir.Moorland sheep grazing predominates, the peaty land producing apH of around neutral whilst the peaty colour of the water shows the humicacid presence, readily seen in the fairly high hazen readings.The uplandcatchment is characteristically nutrient poor giving the reservoir it'soligotrophic status with fish food organisms in the static waters of thereservoir ratherlimited.However, prior to the construction of theearthen dam the River Hodder's upper reaches were annually populated withsalmon and sea trout spawning on the riffles. The quality of the riverinesalmonid production, upstream of the reservoir, was of such value that whenthe dam was proposed, compensation for loss of fish spawning was made byway of constructingDunsopFish Farmfor the Boardof Conservators.Natural trout spawning still exists in the Hodder headwaters and the extentof this will be seen in this report, reflecting the quality of wild browntrout in the reservoir.Additionally, the innate migration of trout still possibly exists in thenative stock because a number of sea trout must have been land locked bythe construction of the dam.There is believed to be a smolt migrationdownstream from the reservoir in the spring of each year and a behaviouralcharacteristic of brown trout, as opposed to rainbow trout, causes thetreatment plant to catch fish on their intake screens throughout the year.The water treatment plant situated below Stocks Dam can filter and treat115 Ml of water per day.Water is taken from the reservoir by way of adraw off tower (Diagram 1) situated 200 feet out from the top level on thedam wall.The draw off tower has three 24" draw off ports each controlledby 2 X 21" valves.At any one time one or more, usually two, of theseports are open, allowing water and whatever is carried in suspension,through the 24" apertures into a 33" collecting main that delivers thewater to the filter house.The supply is then divided into 3, flowingunder pressure to three groups of batteries of filters, but prior to thewater entering the rapid sand filters each supply goes through a screencalled a fish plate.These fish plates are an original design structure(to be described later) athat the treatment plantdesign correctly allowed for the ingress of fish into the works.Asopposed to other water intake structures that have screens to preventinitial ingress of any foreign body, or off line low pressure lledfishplates.
Appropriately'; named, these plates have collected fish regularly, the worstoccasion in recent memory being back in 1959. Records did not exist for thenumbersoffishlost to the plates priorto1977 when the presentsuperintendent thought it relevant to keep an unofficial record.This wasno doubt, initiated due to the drought of 1976 and the records have beenregularly entered up since, and form the basis for this study.Stocks Reservoir has been fished by Stocks Angling Club since the 1960's,the unproductive nature of the water only providing a marginal fishery.Sincethe 1970's diagnostic fishing has been carried out by the clubmembers with the intention of monitoring the quality and type of fishingthat the reservoir can produce.The more recent intentionhas been tomake the reservoir available to the public to fish on a day ticket basisand plans to utilise the whole catchment have been in hand since the late70's.In September of 1983 the Water Management Committee approved a planfor a public fishery on Stocks Reservoir and this was subsequently passedby the board in January 1984.The proposal was to put the fishery out to tender with a closing date inApril, 1984 for the start of fishing in March of 1985.The Authorityproposed to provide necessary basic facilities for access and fishing suchas car parks, tracks, sewerage, cabin accommodation and electricity.This degree of development and provision of facilities required a lease of7 years and an option available for two further 7 year periods. In additionto providing this infrastructure the Authority proposed to help initiallystock the reservoir with a reasonable head of fish to provide a good "putand take" fishery.A heavy stocking of 100 lbs. per acre was stated withthe reservoir at a standing summer level of 210 acres. Therefore, 21,000lbs. of fish is to be introduced, half of which will be provided by theAuthorityon a long lease basis, the tenant replacing this stock ontermination of the lease.The lease also stipulated that at least 30 daytickets will be available to the public and that the tenant will alsoprovide boats for fishing.With a development of this nature the intention to make it succeed isclearly stated in the ample stocking density of 100 lbs./acre. Althoughthis density decreases to about 601bs/acre when the reservoir is full thereis a possibility that there could be substantial fish losses onto thefish plates at such densities.aloss to theExcessive fish loss would not only meanfishery but also an operational problem for the watertreatment works in maintaining supply.3.
The objective of this study is to assess the degree and likelihood of teat the presenttheoperationaland proposedimplications,necessary suggest methods of alleviating the problem.stockingandifThree spheres ofstudy have been undertaken to achieve these objectives, these being:-1. To selectivelystockthe reservoirand monitorthe angling clubcatches in order to assess the total population, relating it to fishplate losses and proposed stocking densities.2.To monitor the fish taken from the fish plates and assess the reasonsfor their ingress.3.Tostudy the draw off tower and fish plates, and suggest ways ofameliorating or halting the loss of fish and consequent operationalproblems.4.
INVESTIGATIVE PROCEDURESFish StockingStocks Reservoir, being a water supply impoundment is prone to severeseasonal fluctuations in water level, (see graph 1 and appendix 1). At topwater level of 30.328 metres and 343 acres the density of fish will be atits normal winter biomass and as the area decreases in the dryer summerweather the density of fish will increase.An area of 210 acres wascalculated to be a good average summer level for the reservoir.metres draw down thisOctober.At 5existed for half of the time between April andConsequently it was decided to stock fish, under the tenancyagreement, at this average water level with 100 lbs./acre.Subsequentlyas the reservoir level increased or decreased so would the density offish, approximately in inverse proportion to the area.In order to simulate the anticipated heavy density of fish stocking it wasproposedto stock the reservoir in 1984, for this study, twice. Theinitial stocking took place in March, when the reservoir was 2.5 metresdown and covered 280 acres.The stocking of 1,000 rainbow trout tookplace in the neck of the reservoir near the dam, see map 1, therebyconcentrating the fish to a partially confined area of the reservoir, nearthe draw off tower for the first few days.The relatively early date forthis stocking was to enable a complete season for the study of anglercatch populationanalysis.10"-12"TroutRainbowconsiderably lower.tookThe secondplaceinstockingJulywhenconsistingtheof 2,000reservoirwasThese fish were stocked in the same location to tryand simulate the heavy density of fish and the water level was down 8.5metres and the reservoir covered about 130 acres.All 3,000 fish stocked were marked for ease of recognition by adipose finclipping.This was carried out at the fish farm prior to transporta-tion and stocking, 24 hours before release.Any loss of fish due tomarking trauma could be accounted for of which where was none.The marking of fish could enable the experiment to detect any of thesealien fish that subsequently end up on the fish plates, the draw off towerbeing so close to the place of stocking.Additionally the marked fishcould be recognised to see where and how quickly they spread throughoutthe reservoir.But ultimately the proportion of angler caught marked fishto unmarked fish would give the study an indication of what the fishpopulation was in the reservoir. Withthis5.quantity,orbiomassof
fish it was intended to compare the existing density and fish loss on thefish plates with the proposed stocking density and potential fish loss.Anglers ReturnsIn order to obtain the recapture of the stocked marked fish Stocks AnglingClub kindly agreed to help the sampling programme by reporting all fishcaught this season.Each member was circulated, (appendix 2) explainingwhat an adipose fin clipped fish looked like in order to reduce the errorin unrecognised sampling.Additionally they were all given pre-paid catchreturn forms (appendix 3) which required them to note the fish caught, oneach and every day fished, whether it was marked or not, its size andweight plus the location caught. The last detail not only enabled a studyon how the fish spread out after stocking but additionally on identifyingthe preferred areas for fish and assess if there was any additional threatto the treatment plant.Treatment Plant Fish PlatesWater from the reservoir is drawn by gravity into the 24" draw off portsin the valve tower over which there is no screen or barrier. Any one ofthe three draw off levels can be utilised, excepting when it is within sixfeet of the surface, or of course out of the water. Air entrainment, withvortices developing, reduces the flow down the main, consequently when thereservoir level drops a combination of port openings is used to maintainsupply.The usual practice is to use the port nearest the surface but ifthe water level drops within the six foot criteria then the lower port isopened 6" to 9" at a time.Ultimately, in times of drought the lowest ofthe 3 ports is fully open with the top and middle out of the water, butthis occurrence is about a 1 in 10 year event,. Selective useof the draw off level is utilised in the event of poor water quality at aparticular level but when the reservoir level is low this facility isobviously not ent plant.valvetowerinto the verticalto a 33" main whichruns undercollecting pipethe dam to theThis direct supply main branches off into two 27" mains,below the floor of the works (see diagram).One branch supplies water to7 batteries of filter shells, the other to 11 batteries of filter shells.Another 4 batteries of filter shells are supplied separately from6.a 33"
pipefrom theincoming main.In total there are 22 vertical pipessupplying water to the batteries.branchesFor batteries 1-18 each vertical pipeinto two, and into each branch a filter chamber is incorp-orated (approx. 12' above floor level) with appropriate values, allowingthe removal and cleaning of one chamber without disrupting the flow to thebattery.The supply pipes to batteries 19-22 are unbranched and each onecontains a single filter chamber situated below ground level under thesteel floor plates.The total number of filter plates in the watertreatment is therefore 40Access to each metal filter plate within the chambers is via a relativelysmall 8" opening over which a steel plate is bolted onto studs by eighthexagonal nuts.Each filter plate can be slid out of the filter chamberfor cleaning and removal of debris and fish. Operational cleaning of theplates is carried out routinely at least once a week, but also whenever asignificant pressure drop is indicated between the inlet and outlet to anyfilter chamber.It is this routine cleaning that has provided the annual totals of fishentrained onto the plates, records for which exist since 1977. The purposeof this years study was to assess the number of fish lost to the plates soas to be able to relate these losses to the exact numbers of known stockfish and estimated wild fish.Accurate records had to be kept by thetreatment plant operatives as to the species of the fish, brown or rainbowtrout, as well as their approximate size.All fish taken from the plateswere kept in a freezer so that fisheries staff could confirm the speciesand size and condition of the fish.Some fishes stomach contents wereanalysed to assess the diet of those fish sucked into whichever draw offport.This was intended to assist in determining the pattern of behaviourcommon to those fish that were lost to the plant.The fish plates that were occluded by fish produced the tell tale loss inpressure across the battery of filter shells. At times of severe ingressof fish nearly all batteries are affected but at other times and duringthe isolated pressure drop incident any battery may be affected.Recordsof the cleared batteries were kept to assess any possible pattern orpreference of occlusion.Other factors that may affect the ingress of fish could be the velocity ofthe inflow through the draw off valves and so records have been extracted7.
of the flows through the plant at times of ingress.neededto be relatedto the densityAdditionally thisof the fish in the reservoir,especially in close proximity to the draw off tower.Consequently thereservoir capacity was analysed in relation to total fish ingress into theplant and all other environmental factors that would produce an ingress offish were examined, such as rainfall and consequent turbidity and hazenfigures.A further 2 sources of fish loss from the reservoir, other than by thedraw-off to supply exist.the compensation/scour.They are either by way of the overspill or viaThe scour draw off from the resrvoir is the samepipe as that of the compensation and positioned 10 metres lower than thebottom draw off pipe in the tower and 20 metres further out into thereservoir.(See tower uously, via the treatment plantsintotheRiverHodderelectricity generation turbine.The statutory compensation is 4 m.g.d. during the summer months of AprilOctober and 3 m.g.d. for the remaining winter months.There are no fishplates or screens for this discharge, however, it is possible to monitorthe outfall by either netting the outlet mushroom or surveying the pondedup area of water before it flows over weir boards into the river. Scourwaterpasses out of the plant through the same outletcompensation flowthe waterbank.as theThe waterbank is a compensation flowthat has been designed to assist the passage of migratory fish up theHodder in times of low flows when fish are congregatedreaches of the river during autumn.in the lowerExtensive analysis has shown thatsalmon will migrate up the Hodder when at least 100 m.g.d. is flowing.Thus, the waterbank reserve of 200 m.g.d. enables 4 releases of 50 m.g.d.to be released on the tail end of an existing spate to simulate a spate ofat least the 100 m.g.d. criteria.benormallyTherefore, flows into the scour will50 m.g.d. down the 36" compensation pipe.The scour as suchis very rarely used because the waterbank compensation serves the samepurpose.However, discharges of 130 m.g.d. at maximum could be released.Plant Operational AlternativesIn order to be able to make recommendations on ways of stopping, or atleast ameliorating the ingress of fish into the treatment plant it was necessaryto look at operational structures and methods.If it provednecessary to prevent fish entering "the pipe" the first line of defenceis the valve tower inlets, the 3, 24" ports.isthe present first line, the fish plates.8.The second line of defence
The fish plates on 18 of the 22 batteries were designed in parallel pairsfor each battery which allowed for the maintainance of supply whilst theplates were being cleared.However, the 4 most recent batteries 19 to 22only have one single in line plate which requires the battery to beswitched off during the complete clearing period. The inconvenience ofthis needed assessing along with the time taken to clear a fish plate andthe subsequent total operational cost.Routine maintenance stipulates that the 22 fish plates are checked once aweek, normally on the night shifts.This entails little inconvenience butwhen the ingress of fish is severe enough to require continual clearing ofthe plates, for a number of days, operational problems could arise. Lossof pressure to supply is the only damage that can arise from this "fishoverload" situation and only by permanent fish plate manning can thesituation be eased and supply pressure regained. In addition to routinetime commitment analysis, the overload manning time had to be studied notonly from a total cost angle but also for a cost benefit analysis.Thetotal cost was studied in relation to reducing the manning time to clearthe filters by makingthe operationmuchfaster.The cost benefitanalysis was studied in relation to any extensive works done to the valvetower to effectively make the fish plates redundant and do away with theneed to clear them at all.Valve Tower SpecificationsThe valve tower as seen in the photograph and in diagram x. is a hexagonalstructure of concrete and stone sets.Itstands about 100 feet off thetoe of the dam embankment and is 17 feet across from wall to wall.Thedraw off ports consist of a 24" pipe bellmouthed to 29" where it is set into the facia stone.The 24" pipe reduces through 2, 21" valves, 6 feet9.
and 8 feet inside the draw off aperture and 3 feet before the draw offconnects with the 24" vertical collecting main.The vertical pipereceives the three draw off inlets from three different angles each oneset 45 off the other.These angles correspond to each upstream faciawall of the hexagonal tower.The lowest draw off level, no. 1 facesdirectly upstream into the reservoir and sits 1 foot off the stone pitcheddam wall.Draw off no. 2 faces to the left (N by W) of the reservoir withits invert level exactly 30 feet above no. 1.No. 3, the top draw offport faces to the right (E by N) of the reservoir (seen in photograph)with its invert level exactly 24 feet above no. 2, the middle one and 14.5feet from the revised top water level. This top water level was lowered by4 feet when the overspill was lowered for safety reasons in 1972.The exclusion of fish from the treatment plant requires there to be abarrier in front of the draw off ports on the valve tower.For thepurpose of this sphere of investigation it was con
AT THE HODDER WATER TREATMENT WORKS, STOCKS RESERVOIR. Stocks Reservoir is situated amidst the Forest of Bowland in the upper reaches of the old river valley of the Hodder. Located about 10 miles due North of Clitheroe its altitude is only 100 metres higher than that of this Lancashire ma
risk assessment (FRA) on behalf of United Utilities at Hodder Water Treatment Works (WTW) (the site), located to the north east of Slaidburn in the Forest of Bowland. The site is bounded to the north by Stocks Reservoir, which supplies water for treatment at Hodder WTW. The River Hodder
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