Research Report 

TRIALS OF AN ACOUSTIC 

FISH DETERRENT SYSTEM 

AT HARTLEPOOL POWER STATION 

A W H Tumpenny, J M Fleming, K P Thatcher & R Wood 

Fawley Aquatic Research LaboratoriesLtd 

For the attention of: 

Mr C J L Taylor, Nuclear Electric plc, Barnwood 

July 1995 

FRRl63195 
1 INTRODUCTION 

2 METHODS 3 

2.1 THESTUDYSITE 

2.2 THESOUND SYSTEM 

2.3 POSITIONING OF THE SOUND PROJECTORS 

2.4 INSTALLATION OF TEF, SOUND SYSTEM 

2.5 EXPERIMENTALDESIGN 

2.6 FISH SAMPLXNGAND ANALYSIS 

2.7 OPERATIONALCONDITIONS 

2.8 STATISTICALANALYSIS 

3 RESULTS 6 

3.1 SPECIES COMPOSITION OF THE CATCH 

3.2 COMPARISONOF NUMBERS CAUGHTIN TEST AND CONTROLPERIODS 

3.3 LENGTHDISTRlBaroNOF THE CATCH 

3.4 CATCHWEIGHT 

4 DISCUSSION 

4.1 SPECIJtSDIFFERENCES 

4.2 DAYNIGHT DIFFERENCES 

4.3 SIZE- RELATED DIFFERENCES 

4.4 SCOPEFOR xMPROVEMENTAT HARTLEPOOL 

4.5 IMPACT ON TBELOCALSEALCOLONY 

5 CONCLUSIONS 

REFERENCES 

APPENDIX 1 

8 

9 

10 

10 

10 

11 

12 

1 

FAWFEY aquatic research laboratories Ltd 
SUMMARY 

Trials were carried out at Hartlepool nuclear power station, on the Tees Estuary, to 

determine the efficiency of an acoustic fish deterrent system as a means of reducing the 

impingementrates of fish on the cooling water (Cw) intake screens. The ingress of clupeid 

(herring-family) fish, chiefly sprat (Spraffusspraffus) and herring (Clupea harengus) at 

Hartlepool has in the past reached levels which have proved operationally difficult to 

handle, as well as environmentally undesirable; at other nuclear sites in the UK,they have 

also led to intermittent loss of generation. The principle of using acoustic deterrence for 

marine and estuarine fish was previously tested for Nuclear Electric plc in laboratory trials, 

and field trials were performed in 1993-4 at Hinkley Point nudear station. These previous 

trials, in which an American sound generating system was employed, were considered to 

have been compromised by unsatisfactory performance of the equipment, although some 

reactionof the fish was shown to occur. 

For the Hartlepool trials equipment of UK manufacture, designed specifically for fish 

deterrence purposes, was used. A sound system comprising a programmeable signal 

generator, power amplifiers and an array of underwater sound projectors was installed at 

the CW intake. An acoustic modelling exercise was first undertaken to determine the 

optimum sound projector positions in order to minimise unwanted effects caused by 

reflecting surfaces and sound source interactions. This led initially to an eight-soundprojector design, with six of the units deployed along the intake wall and two further units 

located in the middle of the dredged intake channel. following measurement of the sound 

field around the intake, it was recognised that signals from the sound projectors close to 

the intake were being drowned out by CW pump-generated noise in the critical 50-600 Hz 

range. Consequently, it was decided to add four more units to the mid-channel position to 

increase the signal-to-noise ratio. 

Installation of the initial system took place in late February, 1995 and testing began on 

March lst, based on a comparison of CW screen-catches for alternating sound-on and 

sound-off days. The revised sound projector configuration commenced operation on 25th 

March and was continued until 12 April. 

An estimated total of I 11,630 fish were collected during the trials, comprising 48 species. 

The bulk of these were sprat (43.6%) and herring (41.2%), whiting (7.7%) being the only 

other fish caught in signicant quantities. The remaining species contibuted only 7.5% by 

number. 

The initial performance of the acoustic deterrent system was generally poor, owing to the 

low signal-to-noise ratio achieved, although herring catches were reduced significantly 

(pC0.05) under this configuration, by 56.2%. The addition of further mid-channel sound 

projectors, however, brought an immediate improvement in effect for almost all species. 

The following figures indicate the percentage reductions measured for the main species 

groupings under the final sound projector arrangement, along with the probabilities that 

these were significantly different from zero: 

All species combined - 55.9% (px0.05) 

Sprat - 60.1% (p<0.05) 

Herring - 79.6% (p4I.01)

Whiting - 53.5% (p<0.05) 

Other Ambladder species - 54.7% (p<0.05) 

FAWLEY aquatic research laboratories Ltd 
Non-swimbladderspecies - 15.6% (ns). 

In weight terns, the system reduced the catch of the top three species (sprat, herring and 

whiting) by 69.0%; for sprat and herring only, the reductioninweight was 73.3%. 

A few minor problems of overheatingwere experiencedwith the sound system over the first 

days of the Gal but these were quickly overcome. A more important problem was 

discovered only at the end of the trial when the equipment was withdrawn, when it was 

found that the sound projectors had become depressurised as a result of air loss along the 

signal cables. This led to an estimated reduction in signal source level by 6-8 dB over the 

duration of the trials, and this was correlated with a progressive reduction in deterrence 

efficiency. The results over the earlier phases with each sound projector arrangement 

suggest that the system’s efficiency could be improved by a further IO-20% now that this 

problem has been eliminated. Further scope for improvement by rearrangement of the 

sound projector positions is identified. 

The potential for application of acoustic deterrent systems to marine and estuarine power 

station CW system appears to be equally as promising as for freshwater locations, where 

efficienciesof 60-100%are now being reported, in Britain, similar systems are being used, 

for example by the NationalRiversAuthority (NRA) to protect fish at a river pumping station 

intake, by the power industry, and by fishery scientists for fish trapping and census 

purposes. The NRA is also engaged in more comprehensive testing with a view to new 

applications on hydroelectric and fish farm sites. in the USA, acoustic deterrent systems 

are also being appliedto inland power stations and to exclude fish from irrigation schemes. 

A local issue at Hartlepool was the presence of a seal colony within the adjacent Seal 

Sands nature reserve. English Nature and allied conservationists were concerned that the 

sound signals from the acoustic system might disturb seals which, prior to the trials, had 

bred successfullyfor the first time in many years. An independent survey of the sealswas 

undertaken in parallel with the fish monitoring survey, by a team of seal specialists. The 

seal survey concluded that the seals showed no signs of distress or harm during the trials 

and that, from the point of view of the seals’ welfare, there should be no problem with the 

permanent installation of an acoustic deterrent system at the power station. Since the 

survey was completed, a pup has been born to this, somewhatfragile, colony. 

Date...~J..:..X.?.C 

for FAWLEY aquatic research laboratories Ltd 

Marine and Freshwater Biology Unit 

Fawley, Southampton SO45 lTW, UK. 

FAWLEY aquatic research laboratories ttd 
I INTRODUCTION 

Much research has been devoted to alleviating the problem of fish impingement at the 

cooling water (CW) intakes of power stations, both to avoid the disposal and 

operational problems caused by screen blockage, and to reduce the ecological impact 

(Turnpenny and Coughian, 1992; Langford, 1993). Solutions attempted range from the 

use of behavioural deterrents (based on light or sound), to mechanical handling 

systems whereby the fish are returned to the water, dead or alive. Some of these have 

been partially successful. For example a mechanical fish return system tested at 

Nuclear Electric's Sizewell 'B' nuclear power stationwas capable of returning live to the 

sea a large proportion (-80%) of the more robust shoreline species but not the more 

delicate pelagic species (Seaby, 1994). A bubble curtain placed across the intakes of 

Nuclear Electric's Heysham 2 power station reduced the catch of fish, predominantly 

the delicate clupeid species, sprat (Spmftus spraffus)and herring (Clupeus harengus), 

by nearly 40% (Turnpenny, 1993). The clupeid species form the majority of the fish 

numbers entrained at most British coastal power stations and occasionally are 

entrained in numbers sufficient to force a reductionor shutdown of generation. 

While early work on the use of sound for fish guidance, for example at CEGB power 

stations in the 1970~~produced few good results (Turnpenny, 1988), more recent 

research has led to a better understandingof signal characteristics which are effective 

at repelling fish. This, combined with much improved hardware for delivering the 

undetwater sound signal, has made the use of acoustic fish deterrents a practical 

proposition for reducing fish entrainment at water intakes. Initial trials of a simple 

underwater sound system at Oldbury-upon-Sevem nuclear power station (Nuclear 

Electric plc) yielded a 39% reduction in bass (Dicenfarchus labmx) impingement on the 

CW screens (Thatcher and Irving, 1992) and other trials at a river pumping station in 

York showed that coarse fish catches could be reduced by 80% (Wood ef a/., 1994). 

Researchersin the United States (Loeffelman et al., 1991a, 1991b; Klinect ef ai., 1992) 

have shown that acoustic fish deterrent systems can create diversion efficiencies of up 

to 100% under suitable conditions. 

Following the initial success of acoustic deterrents at Oldbury-upon-Sevem, Nuclear 

Electric plc, in collaborationwith the Energy Technology Support Unit (ETSU, Hatwell), 

decided to support further development of acoustic signals suitable for repelling a 

broad spectrum of marine and estuarinefish, for potential application at tidal power and 

nudear generating sites. The study (Turnpenny et a/., 1993) resulted in the 

development of a number of signals which were shown to be effective under 

laboratory conditions. The most promising signal found was a swept, low frequency 

signal (400Hz), which was shown to be effective against a vari0ty of marine and 

estuarine fish. An important feature was that fish did not become habituated to the 

signal over a trial period of 1-2 days. Highly significant (p<O.OOI) repulsion from the 

sound source was achieved with all species tested, with the exception of eel (Anguilla 

anguillaa). 

A field testing programme was then established at Nuclear Electric plc's Hinkley Point 

power station in Somerset to try out this signal as a means of reducing fish 

impingement(Turnpenny ef a/, 1994). The site was selected chiefly because it was also 

relevant to ETSU's Tidal Power programme, being close to the potential Severn 

FAWLEY aquatic research laboratories Ltd 
Barrage line. A sound system was supplied by a specialist underwater acoustics 

company in the USA (Argotec Inc., Florida), and a series of 42 days of testing 

(approximating to 1day on, Iday off, in succession) was carried out, the fish screencatch being compared for the sound-on and sound-off days. Unfortunately, the 

equipment failed to perform to the required standard, owing mainly to problems caused 

by the extreme tidal range and velocities at HinWey, which overwhelmed the internal 

pressure compensation capabilities of the submerged sound projector units. This 

resulted in the system being operated at sound pressure levels below target values. 

The main finding from the trial was that fish numbers increased rather than decreased 

when the sound system was in operation. This was suggested to be caused by a diving 

reflex which occurs when the fish are exposed to high sound pressure levels: the effect 

of this behaviour being to bring the fish closer to the seabed level of the CW intake. 

Although this response was inappropriate, the important finding was that the fish did 

react to the sound. It was concluded by the authors that, by generating an effective 

level further away from the intake, either by increasing the signal level or by moving the 

sound sources further upstream in the flow, it would be possible to deter the fish. This 

conclusion was based upon the widely reported behavioural reaction of fish to sound, 

whereby the initial reflex dive is followed by horizontaldispersion away from the sound 

source (Turnpenny ef a].,1994). 

Nuclear Electric considered that further testing in 1995 would be worthwhile, and 

selected Hartlepool nuclear power station (Cleveland) as the test site. The site has an 

onshore intake and therefore offers easy access to the intake area; also, ithas suffered 

a history of operational problems with spratlherring ingress, particularly during the 

summer months. Previous monitoring by the National Rivers Authority (Peaty,. 1993) 

indicatedthat, during the late winter period, the fish numbers would be sufficiently high 

for statistically-valid trials but not so high as to make enumeration impracticable. 

A potential impediment to the deployment of an underwater acoustic system at 

Hartlepool was the proximity of the power station CW intakes to the Seal Sands SSSI 

(Site of Special Scientific Interest), an area within which the acoustic equipment was to 

be installed. In order to obtain a permit to deploy and operate the equipment, Nuclear 

Electric engaged in talks with English Nature and the local INCA (Industry Nature 

Conservation Association) group. The primary concern was that a population of grey 

seals (Halichoenrs grypus) had successfully bred within the SSSI for the first time in 

many years and it was feared that the undewater sounds might disturb them. An 

acoustic modelling exercise was commissioned to determine the likely extent of the 

sound field (Petrie, Nedwell and Needham, 1995), from which it was considered 

unlikely by INCA'S adviser, Or Susan Wilson, that seals would be disturbed by the 

proposed sound system. Nevertheless, a number of steps were agreed to minimise the 

risk to seals, viz: 

(i) boat access to the nature reserve would be restrictedto a period eh from high 

water (HW) to minimisethe disturbance during the seals' hauling-out periods; 

(ii) the sound system would be brought up to its operational level gradually over a 

number of days, increasing the level by no more than 10 dB per day from 

ambient noise levels in the Seaton Channel; 

(iii)a seal monitoring programme would be put into effect by INCA throughout the 

trial: itwas agreed that if any adverse effect on the seals was detected, the trial 

would be suspended immediately. 

FAWLEY aquatic research laboratories Ltd 2 
Itwas also recognisedthat the monitoringprogrammewould provide useful information 

on possible reactions of seals to acoustic deterrent sounds. 

2 METHODS 

2-1 The Study Site 

Hartlepool power station is located on the north side of the Tees Estuary in Cleveland, 

on the north-east coast of England (Figure 1). The CW intakes draw water from the 

Seaton Channel, which lies within the Seal Sands SSSI. The intake is of the onshore 

type, opening onto a short, dredged channel, some 70 m in length (Figure 2 ). Four CW 

pumps of nominal discharge 8.5 m3s-’ each have paired openings along a concrete 

sea wall, which forms the boundary of the power station. Normally, no more than three 

CW pumps are operated simultaneously. 

Water entering the CW intakes is filtered by drum screens fitted with 10 mm square 

stainless steel mesh. Very small fish can pass through this (see Turnpenny, 1982 for 

mesh selection curves); for most species of sprat/herring shape, the critical size for 

penetration is between 40 and 50 mm standard length. Any debris, including fish and 

other marine organisms, caught on the screens is backwashed by water jets, conveyed 

along concrete gullies to trash collection pits, whence the amounts collected can be 

quantified. 

2.2 The Sound System 

The sound system comprised three main elements, as shown in the block diagram of 

Figure 3. Ail equipment was supplied by Fish Guidance Systems Ltd, of Southampton,

UK. 

The first element of the system was the signal generator, FGS Model 1-08. This is a 

solid-state device which holds a pre-recorded signal on EPROM (ErasableProgrammable Read-only Memory). The unit has the capability of storing up to eight 

selectable sound signals, although only one signal was installedfor the Hartlepooltrials 

(EmpiricalSeries No. 7 :see Figure 3). 

The second element was the FGS Model 400 power amplifier/ monitor, and the third 

element the Model 30/600 sound projector. The latter is an electromagnetictransducer, 

effectively an underwater loudspeaker. Each amplifier supported and monitored two 

sound projector units. The Model 301600 sound projectors have a nominal sound 

pressure output of 174 dB re 1VPa @ 1ininthe frequencyrange 10- 600 Hz. 

Pressure changes within the sound projector units caused by tidal depth changes had 

to be compensated; the lack of adequate depth compensation was one of the major 

reasons for the equipment difficulties experienced in the 1993-4 Hinkley Point trials 

(Turnpenny et a/., 1994). Compensation within the Model 30/600 units is provided by 

compressible bladders; those fitted were able to accommodate a threefold increase 

over atmosphericpressure, e.g. a depth change from zero to 20 m. 

A fault with the sound system was detected, but not until the end of the triais when the 

sound projectors were withdrawn. The type of signal cable used, which proved not to 

be air-blocked, led to the gradual loss of compensation air via the signal cable cores. 

Although the sound projectors continued to function throughout the trial, the loss of air 

FAWLEY aquatic research laboratories Ltd 3 
caused a gradual deterioration of signal strength; it is estimated that the source levels 

fell by 6-8 dB over the duration of the trials. 

2.3 Positioning of the Sound Projectors 

The basic aim of the acoustic deterrent system was to create a repellant acoustic field 

within the confines of the dredged channel to minimise the number of fish entering the 

CW intake. The criterion for using the Empirical Series No. 7 signal defined by 

Turnpenny et aL(l993) was that the sound pressure level (SPL) should be set at -30 

dB above background ambient levels for effective repulsion. No initial backround SPL 

measurementswere available, and a value of 305 dB, as measured around the Hinkley 

CW intake (Turnpenny et a/, 1994) was assumed: given the more sheltered conditions 

at Hartlepool, this was expected to be an overestimate. An arrangement of sound 

sources was therefore sought which would yield SPLs in the order of 135 dB re IVPa 

in the lower water velocity region 20-30 m ahead of the water intakes; this was to allow 

fish to pass along the shoreline without becoming entrained. Also, since the mud flats 

adjacent to the intake channel can become exposed at low water (LW), forcing all the 

water to enter via the confines of the channel and so creating high velocities, it was 

considered desirable to place additional sound sources further out into channel to 

dissuade fish from entering the channel area at LW. An acoustic modelling study was 

undertaken by Subacoustech Ltd using the PRISM acoustic model to determine the 

optimum placement of the sound projectors. The initial configuration used is shown in 

Figure 2. Direct measurements of the sound field were also made by Subacoustech 

once the system was operating (Petrie, Nedwefl and Needham, 1995). 

From initial measurementsit became apparent that the signal-to-noise ratio close to the 

intakes of the power station was well below that required, owing to high SPLs 

emanating from the CW pumps. These generated an acoustic signature with peak 

levels at around 50 and 250 Hz which masked the deterrent sound signal within the 

critical area in front of the intakes. After further PRISM modelling had been carried out, 

a decision was made to reinforce the mid-channel sound projector group with the 

addition of four more units, positioned in two groups of two, as shown in Figure 2. 

2.4 Installation of the Sound System 

The Model 30/600 sound projectors were mounted in welded steel frames for 

deployment. 

Those fitted along the intake wall were attached to a chain bridle and lowered manually 

into position to abut against the concrete wall between the paired intake openings, so 

as to sit betweenthe coarse screens. 

The mid-channel speakers were mounted two-to-a-frame and lowered by boat to the 

seabed at the required position. A chain and buoy attached to each frame marked the 

position and allowedfor subsequent retrieval. The cables from each were attached to 6 

mm mild steel chain, using plastic cable ties, and brought ashore close to the intake 

structure. The chains were attached to a concrete mountingat that point 

The cables from all units were routed into the CW pumphouse, where the cabinet 

housing the amplifiers and signal generator was located. Power was supplied from a 

240V AC, single-phase, 30A circuit. 

FAWLEY aquatic research laboratories Ltd 4 
2.5 Experimental Design 

The experimental design used a systematic test pattern with alternating control (sound 

system off) and test (sound-on) days. 

Impingement rates of fish at coastal power stations tend to be highly variable both 

within and between days. Short-term variations occur diurnally and with tidal changes; 

longer term changes are related to spring-neap cycles, water temperature, wind 

conditions and the seasonality of different species (Tumpenny, 1983). An effective test 

sampling programme must accommodate these sources of fluctuation. Past experience 

(e.g. Thatcher and Irving, 1992; Tumpenny et a/., 1994) has shown that a 24hour 

sampling unit is the minimum practicable, owing to tidal and diel influences. In some 

cases, where the potential residence time of fish between the point of deflection and 

the point of sampling is high, longer periods are required. At Hartlepool, this was not 

the case, as the CW inlets open directly into the screenwells; also, chlorine, which is 

toxic to fish, was being applied continuously at the CW intakes to effect biofouling 

control. This ensured that any fish entering the system were quickly disabled by the 

chlorine and removed from the screenwell by the drum screens, limiting the possibility 

of carry-over of fish from control and test periods. 

The length of the trial was initially planned to be 30 days (15 control, 15 experimental). 

This was based on an indication of the variability of daily catches provided by the 

reported NRA sampling programme. In practice, the trial had to be extended to 44 

days, to give sufficient data after the sound projector configuration had been altered 

part way through the programme (see Section 3.2). 

2.6 Fish Sampling and Analysis 

Fish from all the working screens were collected using a net ( 10 mm stretched mesh) 

placed in the trash pit, over the end of the trash backwash gulley. This was emptied 

twice daily: once at 0900 h (night-time sample) and again at 1700 h (daytime sample). 

When the samples obtainedwere too large to handle, subsamplingwas carried out; the 

smallest subsamplewas one-fourteenth. The fish were sorted, identified to species and 

counted. Individuals were measured in length (standard length, to the nearest 5 mm). 

Separate records were kept of daytime and night-time catches. 

Samples of fish were weighed by electronic balance to 0.1 g to allow catch biomass 

estimates to be made. 

2.7 Operational Conditions 

Some deviation from the alternate control-experimentalpattern occurred during the first 

week of the experiment, owing to initial commissioning difficulties. The sound system 

was started up on 25* February, 1995 and brought to full operationallevel b ldMarch. The regular day-on, day-off pattern ran consistently from dhMarch to 12ti! April. Any 

deviation from the sound system's complete operation was noted (for example there 

were occasional overheating problems on the amplifiers during the initial period, until 

improved ventilation and thermal overload protection were provided). 

A record was kept of the number of CW pumps operating on each day of the survey. 

Normally, three pumps were operating. On days when only two pumps were working, 

fish catch values were multiplied by 312 to standardisethe data. 

~ 

FAWLEY aquatic research laboratories Ltd 5 
2.8 Statistical Analysis 

To compare the sound-on versus sound-off screen catches, the population geometric 

mean (PGm) catch per night or day period was calculated, following the convention for 

screen catch analysis establishedby Turnpenny et al. (1983): 

PGm= geometric mean(evatfancd(2dn-lJ1 

Significance testing was carried out using a Student‘s t-procedure to calculate the 

least significant difference (LSD) between sound-on and sound-off conditions for 

p<0.05,as described by Turnpenny and Henderson (1992): 

LSD = to.os[n]4((l/n)(var1+ vat2)), 

where varl is the variance of the catch with sound-on, vat2 is the variance with soundoff, these values being determined separately for each species and for each of the two 

sound projector arrangements. LSDvalues were computed as percentage reductions 

as follows: 

LSD% =loo* LSD/meanZ, 

where mean2 is the mean catch for the trial period with sound-off. A measured 

percentage reduction was then considered to be significant if it was greater than the 

computed LSD% for that species and trial period. 

Plots of the cumulative percentagereduction in catch were calculated as: 

Comparisons of catch species composition and size composition for the experimental 

and control periodswere made using the x2 statistic (Campbell, 1974). Size distributions 

were compared using a modified t-test designed to cope with large sample sizes (the Ztest). 

3 RESULTS 

3.1 Species Composition of the Catch 

During the 42 days of the survey, an estimated total of 111,630 fish was captured in 

the screen samples, comprising 48 recorded species. These are listed in Table I,along 

with total numbers captured. Sprat and herring formed the dominant elements of the 

catch, being 43.6% and 41.2% by number respectively. Whiting was the next most 

numerous species (7.7%), whilst the combined numbers of all other species amounted 

to only 7.5%. 

A comparisonof the species composition of the catch with respect to the sound-on and 

sound-off periods is shown in Figure 4. Composition varied significantly (x2= 14.1, p 

0.01), caused chiefly by a disproportionately large reduction in herring catch during 

‘sound-on’ periods. 

In the remaining analysis, the data have been grouped into six categories: ‘Total Fish’ 

consisting of all the species combined; ‘Sprat‘, ‘Herring’, ‘Whiting’, ‘Other Fish with 

Swimbladders’ (excluding lesser sandeel) and finally, ‘Other Fish without 

Swimbladders’. lesser sandeels were excluded from the’ ‘Other Fish with 

FAWLEY aquatic research laboratories Ltd 6 
Swimbladders’ category as the numbers were due entirely to a large ingress of 0-group 

individualson a single day during the trials (March 17*), which would have distorted the 

statistics. The distinction between fish with and without swimbladders was made in the 

‘Other Fish’ categories, as those species possessing a swimbladder are generally more 

sensitive to sound pressure (see Blaxter, 1981; Hawkins, 1986). A daily breakdown of 

the catch in each of these groups is given in Appendix 1. 

3.2 Comparison of Numbers Caught in Test and Control Periods 

The data set was split into two sections. The first was based on the initial sound 

projector configuration (‘Arrangement 1’), when eight units were deployed, and goes up 

to March 24fi. The second relates to the final siting which was designed to overcome 

the high background noise levels found close to the intakes, and used twelve sound 

projectors (‘Arrangement 2’); this arrangement was in place for the period March 25* 

until April 12*. 

Table 2 gives the number of fish caught in each of the six categories for both testing 

periods, and compares hourly PGm ‘sound-on’ versus ‘sound-off’ counts. The data 

derived from the final sound projector arrangement demonstrate the best system 

performance and showed an overall 55.9% decrease in fish catch. Decreases were 

seen in all of the remaining six categories: sprat (60.1%), herring (79.6%), whiting 

(53.5%), ‘Other Fish with Swimbladders (excluding lesser sandeel)’ (54.7%) and ‘Other 

Fish without Swimbladders’ (15.6%). Figures are also given in Table 2 for percentage 

reductions in day and night periods separately, along with the t-test probability levels 

that the values were significantly different from zero. 

The detailed variations in catch reduction for day versus night are seen most clearly in 

plots of cumulative proportionate reduction in fish catch for sound projector 

Arrangements 1& 2 in Figure 5. The statistical significance of these values is indicated 

by the shaded areas of the graphs: where the plottedfigures overlap the shaded areas, 

it indicates that the percentage reduction is significantly different from zero at the 

p4.05 probability level. It is seen that for most specieslgroupings, owing to high dayto-day catch variability at Hartlepool, a statistically-significant result was reached only 

towards the end of the period of testing. The following more detailed observations may 

be made: 

(i)All Species Combined: The data for Arrangement 1 indicate that there was a 

modest reduction in catch in both the night and day sampling periods when the 

sound projectorswere in operation (29.6%, 9.5% respectively, p>0.05for both). 

for Arrangement 2, both night and daytime reductions combined to give a 

cumulative percentage decrease of 55.9% (p<0.05)by the end of the trial 

period. The degree of reduction is seen to diminish with time; for Arrangement 

2, the reduction started at around 80%. 

(ii) Sprat: During the first part of the trial (Arrangement l),the reduction effect on 

sprat was highly variable and not significantly different from zero (I1.2%’ 

p0.05). Arrangement 2 showed an immediate improvement in system 

performancefor this species, the cumulative mean beginning at around an 80% 

reduction (pgO.05) and declining to 60.1% (peO.05) by the end of the trial. 

Overall, both night and day sampling periods displayed a reduction in catch 

during periods in which the sound projectors were in operation, although the 

effect was marginally stronger during the night than the day. 

FAWLEY aquatic research laboratories Ltd 7 
(iii)Herring: The system was effective against herring with both sound projector 

arrangements, with a mean 56.2% (p<0.05) reduction for Arrangement 1 and 

79.3 % (p<0.05) for Arrangement 2. There was little discenible difference 

between day and night performance. The reduction in effectiveness with time 

was less marked in herringthan in the other species. 

(iv) Whiting: For Arrangement 1, a reductionwas seen only in the night-time catch 

(58.2%,p<0.05 ). The latter was the dominant element and was highly variable, 

so that there was no significant effect on the overall catch caused by the 

acoustic system (-31.9%, ~70.05).With Arrangement 2, the day-night difference 

disappeared, and a mean reduction for the period of 53.5% was found 

(p<0.05), again with a declining trend over the test period. 

(v) Other species with swimbladders (excluding lesser sandeel): Both the nighttime and daytime catches showed reductions when the acoustic deterrent 

system was in operation, averaging 40.8% (~~0.05) for Arrangement 1 and 

54.7% (peO.05) for Arrangement 2. Effectivenessdeclinedwith time. 

(vi) Other species without swimbladders: Small but non-significant (p>0.05) 

reductions were seen in species not possessing a swimbladder. The pattern 

was essentiallythe same for day and night-time periods. 

3.3 Length Distribution of the Catch 

Analysis of the length/frequency data was performed on the three most abundant 

species (sprat, herring and whiting), along with other species for which sufficient data 

were available (flounder, plaice, 5-bearded rockling, pollack, dab and viviparous blenny. 

The data are graphically representedin Figure 6 (a - i). It is shown that: 

(i) significantly smaller whiting (- 4.05 mm; p 0.01) and plaice (- 3.11 mm; p < 

0.01) were caught during sound-on periods; 

(ii)significantly larger 5-bearded rockling (+ 6.23 mm; p < 0.05) were caught during 

sound-on periods. 

These differences are small relative to the mean sizes of the fish. 

3.4 Catch Weight 

Total weights of fish caught during the survey were not measured directly but may be 

estimated from sample figures. The mean fish weights for sprat, herring and whiting are 

given in Table 3. Other species represent a negligable contribution to the overall catch 

weight and are not therefore shown. An estimate may be made of the expected 

reduction in overall catch weight for these three species during sound-on periods on 

the basis of operation of the final configuration of the acoustic system in that period. 

From this, it is calculated that the observed catch of these three species of 503.11 kg 

would decrease to 155.9 kg, a reduction of 69%. For the clupeids (sprat and herring), a 

73.3% reduction is indicated. 

4 ISC CUSS ION 

The acoustic deterrence trials at Hartlepool Power Station have confirmed initial 

indications from earlier experiments carried out for Nuclear Electric plc, at Otdbury 

Power Station (Thatcher and Irving, 1992) that acoustic methods can be used 

effectively to reduce the impingement of fish at coastal power stations. The overall 

FAWLEY aquatic research laboratories Ltd 8 
reduction in fish numbers achieved was 51%, while for sprat and herring, the chief 

problem species for UK coastal power stations, numbers caught were reduced by 

60.1% and 79.3% respectively. In weight terms, this amounted to a 73.3% reduction in 

the combined sprat and herring catch. With improvements in the sound projector 

configuration and hardware design, considerably better performance than this should 

be achievable. 

It is clear from these data that coastal power station sites can benefit from acoustic 

deterrent systems with performance figures comparable to those found in successful 

freshwater applications of the technique. For example, in trials of a similar system 

carried out for the National Rivers Authority on a river pumping station in York, England 

(30 m3s *'maximum discharge), entrainment rates of coarse fish (mainly cyprinids) 

were reduced by 80%, even when fish swimming would have been severely impeded 

by low water temperatures, of 4OC(Wood et a/.,1994); this has led the NRA to install 

a permanent system, and to fund further trials to extend the range of possible 

freshwater applications. In the most recent trial undertaken for the NRA, the Institute 

of Freshwater Ecology have reported a 92% diversion efficiency for salmon (Salmo 

salar) and sea trout (S. frutfa) smolts (Dr S.Welton, pers.comm.). In other countries, 

researchers have also reported high success rates with acoustic deterrent systems in 

freshwaters (Norway: 98% with S. salar: Knudsen et a/., 1994; USA: 60-loo%, various 

spp.: Loeffelman et a/,1991a,b;Klinect efa/.,1992). 

4.1 Species Differences 

Considerable variation in response was found amongst the species observed. These 

may be related partly to anatomicaland partly to behaviouraldifferences. 

Anatomical differences which infhence the hearing capabilities of different species, 

and hence their capacity to respond to acoustic signals, are welt documented (see e.g.* 

review by Hawkins, 1986). An obvious fundamental difference exists between those 

species which have a swimbladder and those not possessing one. This organ acts as 

a sound-pressure-to-particle-motiontransducer, and possessing one has been shown 

to confer an increase of around + 20dB in hearing sensitivity in some species. It is 

therefore logical to expect the difference in results shown for example in Fig 5 (e) and 

(9 between the species with and without swimbladders. Any effect found with the nonswimbladder species (bottom-living types: chiefly flatfish) may have been due to 

vibrations propagated along the seabed (on which the outer sound projectors were 

located), rather than sound pressure fields propagated via the water: the flatfish 

auditory system is receptive principally to particle motion and not to sound pressure 

(Hawkins 1986). 

Within swimbladder-possessing species, variations arise from differences in the fine 

structure of the inner ear and the swimbladder, and the mechanical efficiency of the 

coupling between the two. Both the gadid (cod, whiting) and clupeid (herring, sprat) 

families have been found previously to be sensitive to sounds in the 50-600 Hz 

frequency range employed at Hartlepool (Schwartz and Greer, 1984; Hawkins, 1986) 

and to show avoidance reactions when exposed to a similar deterrent signal when 

applied in the laboratory (Tumpenny et al., 1993, and additional unpublished data). 

However, the variation in degree of responsiveness has not before been evident: the 

Hartlepool results show herring to have reacted more strongly than sprat or whiting 

(79.6% reduction, versus 60.1% and 53.5% respectively). This is most clearly shown by 

the fact that herring were also strongly affected by the initial, weaker sound field 

associated with the sound projector Arrangement I.While no satisfactory explanation 

FAWLEY aquatic research taboratories Ltd 9 
can be provided at present for this substantial difference between two closely related 

species (sprat and herring), auditory anatomy may differ; also, differences in swimming 

capability associatedwith the larger size of the herring (mean 97 mm versus 81 mm for 

sprat, which would yield a 20% increase in speed of the herring over that of the sprat) 

may have contributed, although, size-for-size, sprat and herring have very similar 

swimming performance(Turnpenny, 1983). 

4.2 Day/Night Differences 

Although for the overall combination of species the effectiveness of the sound system 

was similar by day and night (Figure 5 a), marked differences are seen for some 

individual species. The most notable case is that of the whiting for the initial sound 

projector arrangement (Figure 5 d). This day /night difference disappeared with the 

revised sound projector arrangement. 

At present, no satisfactory explanationcan be advanced for these findings. 

4.3 Size - Related Differences 

The significant (p<0.05) differences in mean size of fish caught during sound-on versus 

sound-off periods in some species were small and of no practical significance within the 

present study. The size of the differences may however have been constrained by the 

limited range of fish sizes and age groups present and possible size-related effects 

should be consideredin any future study where a greater range of sizes is represented. 

In a paratle'l situation, it has been shown that the larger gadoid fish showed a greater 

tendency to be repelled by underwater sounds emitted by seismic airguns during oil 

and gas exploration (Engss ef a/., 1993). 

4.4 Scope for Improvementat Hartlepool 

A number of partial sound system failures occurred during the first few days of the trial. 

These were due mainly to amplifiers overheating owing to inadequate ventilation. The 

problem was quickly corrected by increasing ventilation within the amplifier rack; as a 

further precaution, self-resetting thermal overload cut-out switches were fitted to 

prevent amplifier damage. No further problems were found. System availability (as 

sound-projector-days) over the whole period was 86%.; during the final sound 

projector arrangement (Arrangement 2), Le. after the initial problems had been solved, 

availability rose to 100%. The problem of air loss (Section 2.2) from the sound 

projectors via the cables should be addressed in future applications. 

It was quickly recognisedthat the initial sound projector arrangement was not optimal. 

This aspect underlines the importance of undertaking on-site measurements of 

background noise, to establish a baseline for the acoustic modelling: Subacoustech 

concluded that the PRISM modelling could have yielded an appropriate initial sound 

projector configuration, had the background noise information been available (Petrie, 

Nedwell and Needham). 

Although a revised sound projector configuration was implemented, the arrangement 

chosen was a compromisewith the equipment available. A more effective arrangement 

proposed for future application would be to deploy all 12 sound projectors in midchannel positions to create a complete defensive arc so as to prevent fish entry via the 

sides of the channel (Figure 7). The sound projectors located on the intake are 

FAWLEY aquatic research laboratories Ltd 10 
believed to have been largely ineffective as a result of the very low signal-to-noise ratio 

in the key frequency range. 

The problem of air loss from the sound projectors mentioned in Section 2.2,and the 

consequent reduction in the sound pressure levels generated, is considered to have 

been responsible for the declining effectiveness of the acoustic deterrent system over 

the course of the trials. It is thought unlikely that physiological adaptation (‘habituation’) 

by the fish played a part, as the large tidal excursions (several kilometres per tide) 

make it unlikely that fish would remain in the area for long enough to adapt; the 

laboratory experiments showed that habituation was not apparent over 2-3 days of 

repeated exposure (Turnpenny et a/., 1993). It can be surmised that better results 

could be achieved, even with Arrangement 2 of the sound projectors, as used in the 

latter part of the survey, provided that full performance of the sound projector units 

were maintained. The performance figures given in Table 2 are the means for the 

whole of the latter period (25March - 12April), and cover a declining trend in source 

level (see Section 2.3). The average efficiency at the start of this period was around 

8O%, and declined to 50% by the end of the survey The problem of air loss via the 

sound projector cables has been addressedin later versions of the FGS30/600unit 

4.5 Impact on the Local Seat Colony 

The study undertaken by INCA (Wilson ef a]., 1995) monitored the behaviour of the 

Seal Sands colony of grey seals during the trials, and compared their patterns of 

behaviourwith that recordedin previousyears. The report concluded that: 

i) there was no detectable effect of the sound system on seal numbers or 

behaviour on sound-on comparedwith sound-off days; 

ii) during sound-on days, the seals rarely approached the sound sources, but 

showed no signs of alarm caused by the sound when in the water either; 

iii) any effects due to the sound system ‘paled into insignificance’ compared with 

more overt disturbances, e.g. from bait-diggerson Seal Sands. 

In final conclusion, Dr Wilson states that the seal monitoring programme “succeeded in 

allaying fears of any obvious major effect on the seals” and that ”there would appear to 

be no objection from the seals’ point of view ... to this device being permanently 

installed”. 

5 CONCLUSIONS 

1. The acoustic deterrence system proved effective as a means of reducing fish 

catch, as trials elsewhere at freshwater locations have shown. The highest 

effectiveness (6040% reduction, p<0.05) was against the clupeid species, sprat and 

herring, which are most numerous in the CW screen-catches of most British coastal 

power stations. Other species possessing a swimbladder were also strongly repelled 

(-54% reduction, p<0.05), whiie non-swimbladder species showed only a modest 

response (16% reduction: p>0.05). The swimbladder in fish is known to play an 

important role in hearing. 

2. The positioning of the sound projectors was found to be critical. High 

background noise levels generated by the pumps, within the 0-600 Hz range of the 

deterrent signal, were found to interferewith the signa! when the majority of the sound 

projectors were placed near to the intakes. The use of acoustic modelling enabled new 

FAWLEY aquatic research laboratories Ltd 11 
configurations to be assessed quickly and efficiently and led to a successful final 

outcome of the trials. 

3. The reliabitity of the sound generating system was found to be far superior to 

that experienced in previous trials at Hinkley. The overheating problems found during 

the first few days of the trials were quickly overcome by improving ventilation. A 

problem of air loss from the sound projectors caused by leakage via the cables did lead 

to a progressive reduction in sound output and would need to be eliminated in any 

permanent system. 

4. No adverse effects of the system on aquatic wildlife were evident. An 

independent study of the local seal colony arranged by English Nature revealed no 

disturbance as a result of operating the sound system. The implementation of any 

permanent acoustic deterrent system would be expected to have an overall benefit to 

local wildlife and fisheries through the reductionin fish mortalities at the power station. 

REFERENCES 

Blader, J H S, 1981. The swimbladder and hearing. 1n:Hearing and Sound 

Communication in Fishes. Springer-Vedag, New Yo&, pp 109-133. 

Campbell, R C, 1974. Sfatisfics for Biologists. University Press, Cambridge. 

EngAs, Lerkkeborg, S and Soldal, A V, 1993. Effects of seismic shooting on catch 

availabilityof cod and haddock. Instituteof Marine Research, Noway, Fisken og Havet, 

9, 117pp. 

Hawkins A D, 1986. Underwater sound and fish behaviour. In: The Behaviour of 

Teleost Fishes, (Ed. Pitcher, T J), London Croom Helm, pp 114-151. 

Klinect D A, Loeffelman P H & Van Hassel J H, 1992. A new signal development 

process and sound system for diverting fish from water intakes. Proc. Amer. Power 

Conference, Illinois Institute of Technology, April 13-15, 1992, Chicago, Illinois. 

Knudsen, F R,Enger, P S and Sand, 0, 1994. Awareness reactions and avoidance 

responses to sound injuvenile Atlantic salmon. J. Fish Biol., 45 (2), 227-233. 

Langford, T E, 1993. Elecfticity Generation and the �co/ogy of Natural Wafers. 

University Press, Liverpool, 342 pp. 

Loeffelman P H,Van Hassel J H & Klinect D A, 1991(a). Using sound to divert fish 

from turbine intakes. Hydm Review, October 1991, pp 30-43. 

Loeffelman P H, Klined D A & Van Hassel J H, 1991(b). Fish protection at water 

intakes using a new signal development process and sound system. In 'Waterpower 

'91', Amer. SOC.Civ. Engrs, pp 355-365. 

Petrie JE,NedwellJ & Needham K, 1995. Acoustic surveys of a fish deterrent system 

at Harttepool Nuclear Power Station. Subacoustec report no. CNAI84ROI02 

Schwarz, A L and Greer, GL, 1984. Responses of Pacific hemng (Clupea harengus 

Pallasi) to some undewater sounds. Can. J. Fish. Aquaf. Sci., 41, 1183-1192. 

FAWLEY aquatic research laboratories Ltd 12 
Seaby, R M H, 1994. Survivorship trial of the fish return system at Sizewell B power 

station . Fawley Aquatic Research Laboratories Ltd, Report to Nuclear Electric plc, No. 

FCR 102/94. 

Thatcher K P & Irving P, 1992. Fish deterrent trials at Oldbury Power Station, 

November I991to January 1992. Fawley Aquatic Research Laboratories Ltd, Report to 

NationalPower plc and Nuclear Electric PIC,No. FCR 009/92. 

Tumpenny, A W H, 1981. An analysis of mesh sizes required for screening fishes at 

water intakes. Estuaries 4 (4), pp 365-368. 

Turnpenny, A W H, 1983. Swimming performanceof juvenile sprat, Spmttus 

spmaffusL., at different salinities. J. fish Biol., 23,pp 321-325. 

Tumpenny, A W H, 1988. The behavioural basis of fish exclusion from coastal power 

station cooling water intakes. CEGB InternalPublication No. TPRD/L/2657/N84. 

Tumpenny, A W H, 1993. Bubble curtain fish exclusion trials at Heysham 2 power 

station, February 1993. Fawley Aquatic Research laboratories Ltd, Report No. FCR 

037193. 

Turnpenny, A W H,Utting, N J, Millner, R S and RiJey, J 0, 1983. The effect of fish 

impingement at Sizewell A power station on North Sea fish stocks. CEGB Sizewell B 

Public Inquiry Supporting Document No. S380. 

Turnpenny, A W H and Coughlan, 1992. Power generation on the British coast: thirty 

years of marine biologicalresearch. Hydrecol. Appl., 4, pp. 1-11. 

Tumpenny, A W H and Henderson, P A, 1992. Design and testing specification for a 

fish deterrent bubble barrier for Heysham Power Stations 1 & 2. Fawley Aquatic 

Research LaboratoriesLtd, Report to Nuclear Electric plc, No. FCR 006/92. 

Turnpenny, A W H, Thatcher, K P, Wood, R and Loeffelman, P H, 1993. 

Experiments on the use of sound as a fish deterrent. Fawley Aquatic Research 

Laboratories Ltd., Contractors Report to the Energy Technology Support Unit (ETSU), 

Harwell, Didcot, Oxfordshire OX11ORA, Rept. No.ETSU T/04/00171/REP. 

Tumpenny, A W H, Thatcher, K P, Wood, R and Nedwell, J, 1994. Fish deterrent 

field trials at Hinkley point power station, Somerset, 1993-4. Fawley Aquatic Research 

laboratories Ltd , Report to Nudear Electric plc, No. FRR 132/94. 

Wilson, S, Cook, M, Grellier, K, Leakey, M, Mathwin, S, Muir, D and Parfane, S, 

1995. Monitoring of seals at Seal Sands during the Acoustic Fish Deterrent Trials (27th 

February to 13thApril, 1995). Report to Nuclear Electric plc, May 1995. 

Wood R, Thatcher K P,Woodcock A & Turnpenny A W H. 1994. Fish deterrent 

trials at the River Foss pumping station, York, 1993-1994. Fawley Aquatic Research 

LaboratoriesLtd, Report No. FIR 087/94. 

~~ 

FAWLEY aquatic research laboratories Ltd 13 
f 

. ­ j 

f 

i *\ 

1' 

f Hartlepool f 

Tees Estuary j 

___ 

..--.----.-.---

.-_..I___.___..___ 

Figure 1 Location Map Showing Hartlepooi Power Station and Environs 
......................................... ......................................... ......................................... ......................................... 

......................................... ......................................... 

......................................... ......................................... ......................................... ......................................... 

.................................... .................................... 

.................................... 

................................. ................................. 

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.............................. .............................. 

.............................. ........................ 

.................... 

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..................................... ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... .................................... ..................................... 

..................................... 

......................................... 

....................................

.................................... .................................... 

................................. 

.............................. ........................ 

.................... 

............................... 

....................................

..................................... 

--kN 

Drum Screens 

Trash Basket 

@ Sound Projector Arrangement 1 

Scale 

1 50 m i Additional Sound Projectors,Arrangement2 

Notes: Mid-channel sound projector positions were each occupied by twounits mounted on a single frame 

Depths shown as Chart Datum. 

Figure 2 Map of Hartlepool Cooling Water intake Channel showing Bathymetry and the Two 

Arrangements of Sound Projectors 
Total Numbers of Individuals for Key Species Recorded for Test and 

Control Periods Cornbined, and Minor Species Recorded. 

ALL DATA ADJUSTED FOR 3 RUNMNG CW PUMPS - IGNORES IST MARCH SAMPLE 

Species 

Sprat 

Herring 

Whiting 

Sand eel 

Flounder 

Plaice 

Stickleback, 3-sp. 

Rockling, 5-B 

Goby, SP 

Lesser weever 

Dab 

Vivaparous blenny 

Pollack 

OTHERS 

TOTAL 

Scientific Name 

Sprattus sprattus 

Ciupea harengus 

MerJangius merlangus 

Ammodytes tobianus 

Platichtbys fiesus 

Pieuronectes platessa 

Gastervsteus aculeatus 

Ciliafa mustela 

Gobidae 

Echiichthys vipera 

Limanda limanda 

Zoarces viviparus 

Pollachius pollachius 

ADDITIONAL MINOR SPECIES (uncorrected1 

Saithe 

Cod 

Hooknose 

Sea scorpion 

Northern rockling 

Bull-mut 

Sea trout 

Common eel 

Pollachius virens 

Gadus morhua 

Agonus cataphractus 

Taumlusbubalis 

Ciliata septenfrionalis 

Myoxocephaius Scorpius 

Saimo trutta 

Anguilla anguilla 

Total YOof Total 

48613 43.55 

4603I 41.23 

8624 7.73 

2210 I.98 

1942 1.74 

1198 1.07 

868 0.77 

431 0.39 

408 0.36 

256 0.23 

214 0.19 

164 0.15 

4 07 0.09 

564 0.52 

1'I1630 

95 

73 

64 

49 

37 

34 

33 

24 
Table I 

lumpsucker Gyclopfernslumpus 24 

Dover sole Solea solea 23 

Greater pipefish Syngnafhusacus 20 

Witch Glypfucephaluscynogiossus 13 

Greater sandeef Hyperoplus lanceolatus 12 

Butterfish Pholis gunnellus 8 

Pearlsides Maurolicus muellen 7 

Dragonet Callionymus lyra 7 

Stickleback, 15 sp. Spinaehia spinachia 6 

Sand smelt Atberina boyeti 5 

Dogfish Scyliorhinus caniculus 4 

Grey gurnard Euttigla gumardus 4 

Common sea snail Liparis lipatis 3 

Cucumber smelt Osmerus epedanus 3 

Atlantic salmon Salmo saiar 2 

Tadpole fish Raniceps raninus 2 

Nilsson's pipefish Syngnathus rostellatcrs 2 

Brill Scophthalmus rhombus 1 

Lemon sole Microstomus kitt 1 

Turbot Psetta maximus I 

Ballan wrasse Labrus bergylta 1 

Golden grey mullet Liza aurata 1 

Thick-lipped mullet Cheion Iabrosus 1 

Noway pout Trisopterus norvegicus 1 

Lamprey Lampetra f-luviatilis I 

Worm pipefish Nerophis hmbriciformis I 

Angler fish Lophius piscatorius 1 
Table 2 Mean Reductions in Fish Catch with the Acoustic Deterrent System 

Operating, for Each of the Two Sound ProjectorArrangements (see 

Figure 2). 

1 Period 

Reduction 

Significance 

Reduction 

significance 

Reduction 

Significance 

Reduction 

Significance 

1 Arrangement I 

Smcies 

All Species 

sprat 

Herring 

Whiting 

1 Arrangement2 

* 

1-24 Marc 

Night 

0.1% 

ns 

-36% 

ns 

34.1% 

* 

-39.1% 

ns 

32.4% 

ns 

24.5% 

ns 

ns 

52.3% 39.5% 53.0% 62.1% 54.7% 

ns nS 

31.2% 25.9% 17.0% 2.2% 15.6% 

ns ns ns ns ns 

Other Species Reduction 

with Swimbladder Significance 

Other Species Reduction 

without 

Swimbladder Significance 

Note:negative vaiues indcafeinceased cafch 

Significancelevels: ns = p>0.05 

= p<0.05 

! 

FAWLEY aquatic research laboratories itd 

I I 

Control Unit 

I FGS400 FGS 400 

A Amplifier Amplifier 

FGS 

30/600 30/600 

Sound Sound 

Projector Jrojector 

FGS 400 FGS 400 

Amplifier Amplifier 

Note: Only two sound projectors are shown; 

each amplifier was connected to two sound 

projectors. Thenumber of units shown relates to 

Arrangement 7; two more amplifiers and four 

additional sound projectors were used in 

Arrangement 2. 

(a) Block Diagram of Sound Generating System Components. 

I--.-.---

Y 

\ 

E 

t

2

D -".__-_.I_ -....-_.­ 2

L 

oL 1 I I I I I 

0 0.2 0.4 0.6 . 0.8 1 1.2. 

Time / seconds 

(b) Graphical Representation of the 'Empirical Series No 7' Deterrent Signal 

Figure 3 The Sound Generating System and Acoustic Deterrent Signal 
a, 

a, 

v) 

v) U

0 

'C a= a,

0 a 

U 

c 8 

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0 S 

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c 

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0 

*

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v) + 

# 

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ii 
Figure 5 Cumulative Mean Percentage Reduction in 

Fish Catch for Sound Projector Arrangements 1 812 

Species: All Combined 

Arrangement 1 i- Arrangement 2 

Species:Sprat 

1 

0.5 

0 

-0.5 

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Date: March - April 1995 

-Night +Day -24-hour 
Figure 5 (continued) 

Species: Herring 

Arrangement 1 i- Arrangement 2 

Species:Whiting 

-Night -+-Day -24-hour 
U 

Date: 

Figure 5 (Continued) 

Speciw: otherSpecies,with swimbladders 

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* Scale 

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Figure7 Proposed PermanentArrangements of Sound Projectors 
Appendix 1 

Day, Night and 24-h Numbersof Fishlmpingedfor Sound-on and Sound-offdays 

FAWLEY aquatic research laboratories Ltd 1 
Appendix 1 

Day, Night and 24-hNumbersof Fish ImpingedforSound-on and Sound-off days 

FAWLEY aquatic research laboratories Ltd 1 
All SDecies Combined 
Swat 
Herring 
Whiting 
Other suecies: with swimbladder 
Other species, without swimbladder 
Acoustic Surveys of a Fish Deterrent 

System at Hartlepool Nuclear Power 

Station 

Report no. CNA184R0102 

anproved for release 

J E Petrie 

J Nedwel 

and 

K Needharn 

J Nedweii, principal Consultant 

July 1995 
Acoustic Surveys of a Fish Deterrent Systeiti nf fiartlepool Nuclear Power Station 

Contents 

1. 

2. 

2.1 

2.2 

3. 

3.1 

3.2 

4. 

5. 

List of Figures 

introduction 

Environmental Survey 

Measurements 

Results 

Locai Sound Field Survey 

Measurements 

Resu1ts 

Discussion 

Conclusions 

List of Figures 

2 

4 

5 

5 

6 

9 

9 

9 

12 

13 

14 

15 

16 

17 

18 

Figure 1 Map of Seaton Channel and environmental survey 

measurement positions 

Figure 2 Table of environmental survey overall broadband sound 

pressure levels 

Figure 3 Graph of fiequency spectra of time histories for 

positions Ib and 2 

Figure 4 Graph of frequency spectra of time histories for 

positions 3 and 4 

Figure 5 Graph of frequency spectra of the source levels along 

the inlet channel centreline 

2 

Document CN'i81ROiO2 
Acoustic Surveysofa Fish Deterrent System at IinrrtEpool Nuclear Power Station 

Figure 6 Graph of the broadband sound pressure levels dong 

the inlet channel centreline 

Figure 7 Graph of frequencyspectra of time histories for 

positions E and F 

Figure 8 Graph of source level frequency spectra along 400m 

of Seaton Channel 

Figure 9 Graph of the broadband sound levels along 4001x1of 

Seaton Channel 

Figure 10 Graph of frequency spectra of time histories for 

positions D and G 

Figure 11 Graph of frequencyspectra of time histories for 

positions la and lb 

Figure 12 Map of the water inlet channel 

Figure 13 Table of the broadband sound pressure levels in the 

water inlet channel 

Figure 14 Graph of the broadband sound pressure levels in the 

water inlet channel 

Figure 15 Graph of frequency spectra of time histories recorded 

inpositions 1-1 to 1-5 

Figure 16 Graph of frequency spectra of time histories recorded 

in positions 1-1 to 1-5 

Figure 17 Graph of eequency spectra of time histories recorded 

in positions 2-1 to 2-5 

Figure 18 Graph of fkequency spectra of time histories recorded 

in positions 2-1 to 2-5 

Figure 19 Graph of frequency spectra of time histories recorded 

in positions 3-1 to 3-5 

Figure 20 Graph of frequency spectra of time histories recorded 

in positions 3-1 to 3-5 

Figure 21 Graph of broadband sound pressure levels along 

the centre of the inlet channel 

~~ ~ 

3 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

Subucoustech Ltd 1995 Document CNAI84ROf02 
Acoustic Siirveys of a Fish Deterrent Svsrettl ut IfartlepooliVucleur Power Station 

1. Introduction 

Subacoustech Ltd were tasked by Nuclear Electric PLC to study the sound field produced 

by an acoustic fish deterrent system . The system was installed in Seaton Channel, a part 

of the River Tees Estuary, by Fish Guidance Systems Ltd in February 1995 for a trial 

period to reduce the numbers of fish entering the intake for the condenser cooling water 

system of Hartlepool Nuclear Power Station. A map of the site may be seen in figure 1. 

Prior to the installation of the deterrent system, acoustic modelling had been carried out 

using the Subacoustech Ltd PrISM model. This led to a configuration of eight model 30­

600 sound projectors. Six of these were placed along the water intake wall and a further 

pair of projectors was installed at the mid-point of the entrance to the water inlet channel. 

These projectors emitted a series of acoustic signals which research had shown to deter 

fish &om swimming toward the signal source [Turnpenny et uZ 19941. An acoustic survey 

was required to ensure that sound pressure levels were contained within the inlet channel 

and that significant sound levels did not extend to the local seal population on the opposite 

side of Seaton Channel. This survey was performed on 12th March 1995 after some initial 

measurements had been performed on 8th March 1995. At the time of measurement, 

projectors 110.3and no.5 had been displaced by water flow to positions directly in front of 

two of the water inlets, the high water inflow subsequently altering their radiation 

characteristics. These two sound projectors were therefore deliberately disconnected from 

the system to avoid the behaviour of the system being compromised. The survey 

demonstrated high background levels close to the power station water pumps. 

Following Grther acoustical modelling, a revised projector arrangement was devised 

involving the addition of four more projectors, 40m along the inlet channel from the water 

intake. A second survey was then undertaken after the system had been renovated at the 

end of the trial on 17th May 1995 to record the acoustic field generated by the revised 

sound projector configuration. 

4 

Subacousrech Ltd 1995 Llonmmenr CNA184R0102 
Acoustic Siirveys of n Fish Deterrent ,!+stem at Ifortiepoolit'uclear Power Station 

2. Environmental Survey 

2.1 Measurements 

Recordings of the sound field on the bed of the channel and also at the wall on which the 

water intake is located were made using a Bruel and Kjaer type 8103 hydrophone (serial 

no. 1013189). The hydrophone output was fed into a Subacoustech low noise voltage 

amplifier type SAVOlO (serial no. 040), the output of which in turn was fed to a Sony 

portable DAT recorder type TCD-D7 (serial no. 73734). With the exception of the 

hydrophone, which was mounted externally, the equipment was housed in a Subacoustech 

portable hyperbaric pressure vessel. In the case of the recordings made at the water intake 

side wall, the equipment was simply lowered into the water fiom the top of the wall. For 

the measurements taken at the edge of the water inlet channel and in Seaton Channel, the 

equipment was lowered onto the bed of the channel at each position from the Boy 

Andrew, a workboat that had been used also for the installation of a number of the 

projectors. The workboat was fitted with Furuno radar instrumentation type FR-603D 

(serial no. ADB9ZWFR6031) which enabled accurate positional data. The recordings 

made from the Boy Andrew were made within 2.5 hours either side of high tide as 

required by English Nature to prevent any disturbance to the seal population which tended 

to use the channel at times of low water. 

A total of fifteen sets of measurements were taken at fourteen different positions in or 

around the power station intake, a map of which may be seen in figure 1. Since 

measurements could only be taken in the channel at times of high water to prevent 

disturbing the seals, recordings were made on 8th March 1995 of sound pressure levels off 

the water inlet channel side wall at positions la and lb during different tidal conditions. 

Further recordings were made on 12th March at various positions in Seaton Channel. 

These are shown in figure 1 as positions 2 to 4 which were situated along the axis of the 

water inlet channel and positions A to J which formed a line of measurements across the 

axis of the inlet channel along a 11OOm stretch of Seaton Channel. 

The recordings made were calibrated using a 1V, 1OOOHz signal from a Hewlett Packard 

type HP3301A signal generator and a Goldstar 20MHz type OS-9020A oscilloscope 

(serial no. 4010355) which was also used for initial sound pressure level analysis. 

The DAT recordings were subsequently analysed using computer software and were 

auditorily examined by means of an Audio Technica full range speaker system. 

In addition to these recordings, a chain of four Subacoustech type Hp02 hydrophones 

were laid along the length of the inlet channel and into the main water channel to enable 

sound level monitoring during the run up period of the installation. Unfortunately due to 

the presence of high level electrical return current to the power station in the water, 

intederence was present to such an extent that no useful results could be obtained from 

5 

Subacoustech Ltci 1995 Document ChA184RO102 
Acoustic Sus'unwysof a Fish Deterrent Xvstetn crt Hartlepool Nuclear Power Station 

these hydrophones and reliance was instead placed on the submersible measurement 

equipment. 

2.2 Results 

Two lines of measurements were taken for the environmental survey. Positions 2 to 4 

were situated along the axis of the water inlet channel. Measurements were made at 

positions A to J across the axis of the water inlet channel, dong a 1lOOm stretch of Seaton 

channel. Figure 2 is a table of the results of the measurements of the overall broadband 

sound pressure levels made for the environmental survey. Along the axis of the water inlet 

channel it can be seen that the signal strength was only 8dB above background at 100m. 

Since the signal to noise ratios at positions E and G are OdE3 (Le. the signal has decayed to 

the normally occurring level of sound) the attenuation experienced by the propagating 

deterrent signal was sufficient to reduce the sound pressure level from the system to that 

of background within lOOm to the east and 200m to the west of the water inlet channel. It 

is clear that the acoustic field was extremely weil confined within the inlet channel. 

The background noise in and around the water inlet channel was high and audibly 

extremely simiiar to the airborne noise in and around the power station pump house. The 

pumps were situated directly behind the water inlet channel and were clearly the main 

source of the waterborne background noise. Figures 3 and 4are frequency spectra of time 

histories recorded in the measurement positions lb, 2, 3 and 4 which represent the 

positions closest to the power station. Strong peaks at 25Hz, 50Hz and 300Hz are 

evident in the plots, characteristic of the noise from the power station. It is also clear from 

these two graphs that the background noise at the water intake, the edge ofthe water inlet 

channel and lOOm fiom the water intake along the inlet channel centreline were of sbir6lar 

levels. However 150m away from the intake, along the inlet channel centreline, the 

background noise level drops considerabfy. This is to be expected since the geometry of 

the water inlet channel is such that sound energy is likely to be codined within it by the 

mud banks on either side, whereas in Seaton channel the sound would be able to spread 

with consequent reduction in level. . 

This confinement to the water inlet channel is supported by figure 5 which presents 

ftquency spectra of the source levels along the inlet channel centreline and figure 6 which 

is a graph of the broadband sound pressure levels at the same positions. The Ievels at 

positions 1 and 3 are similar. The frequency spectra of position 2 indicated that the source 

levels were higher . Since position 2 was close to a pair of sound projectors this is to be 

expected. The broadband sound pressure levels suggest that position 1 is higher but this is 

because of high background peaks at 25&, 50Hz and in particular 300Hz. However, the 

main observation that can be drawn is that the levels for position 4 are considerably lower 

than the levels at the other three positions nearer the power station water intake. 

Evidently the propagation of both background noise and the deterrent signal was well 

confined along the line of the water inlet channel up to 100111, 

6 

Subacoustech Ltd 1995 Document CNA184ROIO2 
Acoustic Simeys of n Fish Deterrent $yStelil ut ffartkpooiNudear Power station 

Figure 7 presents spectra for positions E and F which were in Seaton channel, 1OOm either 

side of the inlet channel centreline. The results obtained at these points indicate broadband 

signal to noise ratios of OdB and 2dI3 respectively. These can be compared to the 8dB 

signal to noise ratio obtained for position 4 which was along the inlet centre line. Position 

4 was actually hrther away from the water intake. This is best illustrated by figure 8, a 

graph of source level frequency spectra along 400m of Seaton Channel and figure 9, a 

graph of the broadband source levels of the same area. Both plots indicate that the sound 

levels along the axis of the water inlet channel are well above those for the positions 

elsewhere along Seaton Channel. 

Figure 10 is a graph of frequency spectra of measurements taken at positions D and G, 

with the system on and also with the system OK The levels with the source on at position 

G appear higher than background and would suggest a signal to noise ratio greater than 

OdB. This however is not the case since the auditory examination of the recordings 

indicate that no deterrent signal is present and the spectra of the recording with the system 

on is characteristic of background noise rather than resembling spectra of the deterrent 

signal obtained in other positions. An increase in background noise level is therefore 

responsible for this anomaly. Although the reason for this increase is unknown, changes in 

background noise are common as a result of changes in wind speed or improved 

propagation in patches of homogeneous water. 

Figure 1I presents fkequency spectrum analysis of the recordings made at the water inlet 

channel side wall. It is interesting to note the difference between the two sets of data. 

Although taken at the same point the measurements were taken four hours apart and 

therefore at different tidal conditions. For a fluid medium to propagate sound effectively it 

is necessary for the fluid to be of a depth of at least a quarter ofthe wavelength of the 

required signal. Position la presents measurements taken in water of a relatively shallow 

depth of approximately 1.5m.This depth represents a quarter wavelength in water of a 

frequency of 250Hz and it can clearly be seen that with the exception of frequencies below 

50Hz relatively little propagation of background noise or deterrent signal occurs below 

250Hz. This can be compared to the data of position lb which represents data acquired at 

the same point but only an hour before high tide, the water depth being approximately 4m. 

This corresponds to a cut offfrequency of 1OOHz, which again is evident in figure 11. The 

propagation of sound therefore is to some degree affected by the tidal conditions, lower 

water levels attenuating radiation at the lower end of the frequency spectrum. This effect 

was predicted by the PrISM model. 

To summarise, from the results of the environmental acoustic survey, a number of points 

can be noted. 

1) The ievel of the deterrent signal drops to that of the background noise within 225m of 

the water intake. 

7 

Subaeoustech Ltd 1995 Document CNA184ROl02 
2) The background noise level is high and mainly due to the noise emission from the 

cooling water pumps. 

3) Both the background noise and signal propagation is extremely confined dong the axis 

of the water inlet channel up to 100m. 

4)The sound propagation from the water intake is to a certain extent affected by the tidal 

conditions, the lower frequencies being attenuated at low water. 

8 

Subacoustech Ltd 1995 Document CNA184RO102 
Acoustic Sirr?}eysoju Fish Deterrent Svsteni ut HurIlepool It’uclear Power Stution 

3. Locd Sound Field Survey 

3.1 Measurements 

The acoustic measurements for investigation of the local sound field were made on 17th 

May 1995 using a Bruel and Kjaer type 8105 hydrophone (serial no. 1417794) suspended 

in the water from a dinghy at a depth of 5m from the surface. The hydrophonewas linked 

to a Bruel and Kjaer charge amplifier type 2635 (serial no. 1006781) and recordings were 

made using a Sony DAT recorder type TCD-D7 (serial no. 73734). The recordings made 

were calibrated using a 400mV, lOOOHz signal from signal generator and a Goldstar 

20MHz type OS-9020A oscilloscope (serial no. 4010355). As with the environmental 

survey, the DAT recordings were examined audibly and were analysed using computer 

software. 

Measurements were made at a series of fifteen positions in the region of the water inlet 

channel with the improved deterrent system klly operational. These consisted of three 

lines of measurement points. Figure 22 is a map of the area indicating the positions at 

which measurements were taken. Line 1 comprised of measurement points along a line 

parallel to the axis of the inlet channel 15mto the west of the centreline. Line 2 comprised 

of measurement points along the centreline of the inlet channel. Line 3 comprised of 

measurement points along a line parallel to the axis of the inlet channel 15m to the west of 

the centreline. Along each line, five measurements were made at distances of 12, 20, 30, 

40and 50m fiom the intake. These positions are referred to in this report as measurement 

points 1-1 to 1-5, 2-1 to 2-5 and 3-1 to 3-5. For example position 1-4 represents a 

measurement point 40m along the inlet channel from the water intake, 15m west from the 

inlet channel centreline. Positional information was acquired by means of an optical range 

finder. 

3.2 Results 

Figure 13 is a table of the broadband sound pressure levels measured in the water inlet 

channel, in the positions indicated in figure 12. 

Figure 14 is a graph of the broadband sound pressure levels at the points of measurement 

in the water inlet channel. It is evident that the levels recorded along line 3 with the 

system switched on are lower than those for lines 1 and 2. Since the background levels 

follow a similar pattern, this is evidently a characteristic of the propagation of sound from 

the power station intake along the water inlet channel. 

The highest recorded sound levels along lines 1 and 2with the system switched on occur 

at positions 1-4 and 2-4 which were both 40m from the intake. This is logical since both 

these measurement points coincide with the positions of projectors. However since the 

9 

Document CNA184ROI02 
measurements were taken at a depth of 5m, the projectors were below the point of 

measurernent. The highest recorded sound level for line 3 with the system switched on 

occurs at position 3-1 which represents a distance from the intake of 12m.There is a 

second, much smaller peak, however, the same level occurring at both positions 3-3 and 3­

4, distances 30m and 40m respectively measurement points. This is in agreement with the 

previous observation of less effective propagation on this side of the water inlet channel. 

However, the greatest signal to noise ratios occur at positions 1-4, 2-4 and 3-4. The 

maximum effectiveness of the system would therefore appear to be 40m away fiom the 

intake on all three lines of measurement, a distance which coincides with the position of 

the mid-channel group of projectors 

The range of the sound pressure levels measured in the inlet channel is relatively small. 

The difference between the lowest and highest values of the background measurements is 

8.4 dE3 and difference between the lowest and highest values with the system on is 9.5 dE3. 

This indicates that the sound field within the inlet channel is fairly uniform when compared 

to the typical sound field decay which would be experienced in open water. 

Position 2-5 of the local sound field survey coincides with position 2 of the environmental 

survey. The broadband sound pressure levels of the two surveys agree well in this 

position despite the fact that the two surveys were conducted approximately two months 

apart. The background noise levels are within 1dB of each other and the measurements 

taken with the system on present a difference of 3dB, the local sound field survey 

indicating the higher level at this point. This can be accounted for by the fact that the 

additional projectors were in place at the time of the local sound field survey. 

Figures 15 and 16 are graphs of fiequency spectra of time histones recorded in positions 

1-1 to 1-5. These are in agreement with the broadband sound pressure levels given in 

figure 13. Figure 15 shows the levels with the system on in positions 1-1 and 1-2 to be 

similar to the background noise spectra. It is evident that the high levels of noise close to 

the water intake were sufficient to substantially reduce the signal to noise ratios in this 

area. It is interesting to note the source level characteristics in the region of 400% to 

500Hr; in figure 16. The similar contours but different levels in this frequency range 

suggest that position 1-4 experienced the highest degree of direct contribution from the 

mid-channel group of speakers and position 1-3 the least. 

Figures 17 and 18 are graphs of frequency spectra of time histories recorded in positions 

2-1 to 2-5. The most noticeable characteristic with the system on is the higher levels 

below lOOHz and large peak in the range 400Hz to 500Hz in position 2-4. This indicates 

a higher degree of direct contribution fiom the projectors than the other positions which is 

as expected since this position corresponds to the mid-point of the mid-channel speaker 

group. 

10 

. . Docunient CNA184R0102 
Acoustic Surveysafo Fish Deterrent $stein at Hartiepool Nuclear Pawer Station 

Figures 19 and 20 are graphs of frequency spectra of time histories recorded in positions 

3-1 to 3-5. As the broadband sound pressure levels indicate, the levels with the source on 

are extremely similar despite their distance apart. 

In summary: 

1) Propagation along the east side of the inlet channel was not as efficient as that along the 

centre of the channel or along the west side. 

2) The largest signal to noise ratio and therefore the highest efficiency of the system 

occurred 40m along the inlet channel from the water intake. 

3) The sound field was relatively uniform throughout the inlet channel. 

4) The measurement point common to both the environmental measurements and the local 

sound field measurements indicated significant agreement between the two surveys. 

11 

SubacoustechLtd I995 Document CNAi84RO102 
4. Discussion 

The biological investigation of the fish catch showed the deterrent system to be effective 

during the period of the trial installation at Hartlepool. The measurements of the sound 

field within the inlet channel indicate that the signal to noise ratio of up to 15.5dB was 

sufficient for the system to act as a fish deterrent, the point of maximum effectiveness 

coinciding with the position of the mid-channel group of projectors. The measurements 

made in Seaton channel indicate that the signd had decayed to that of background within a 

maximum of 225m fiom the water intake in all directions. 

Figure 21 is a graph of the broadband sound pressure levels along the centre of the inlet 

channel for system both switched on and switched off Both these plots have been 

extrapolated linearly to indicate the distance along the axis of the water inlet channel at 

which the background noise fiom the power station and the signal level fi-om the deterrent 

system might be expected to decay to the average background level recorded in Seaton 

channel which was 11SdB re 1pPa. The level with the system switched on decays along 

the axis of the inlet channel to the average background level within 200m. Ideally, the 

signal to noise ratio within the inlet channel should be as high as possible to maximise 

effectiveness but with the signal decaying to background rapidly with increasing distance. 

The system could therefore be enhanced by increasing the source level and therefore the 

signal to noise ratio, within the inlet channel, without risk of adverse effects on the seal 

colony. As illustrated in figure 21 it is estimated that the acoustic field created by an 

increase in source level of as much as 20&, which represents a tenfold increase in sound 

pressure, would still decay to background level at a distance of 270m. 

12 

SubucoustechLtd 1995 Document CNA184R0102 
5. Conclusions 

A number of conclusions can be drawn from the two acoustic surveys undertaken. 

Generally: 

1) Both surveys measurements indicated that the sound field was extremely well confined 

within the water inlet channel. Both the background noise and the deterrent signal 

levels within the inlet channel were significantly higher than the surrounding area of 

Seaton Channel and the sound decayed to the background level within a maximum of 

225m . It is suggested that this was due to the geometry of the water inlet channel. 

2) The propagation of sound was to some degree affected by the tidal conditions, lower 

water levels attenuating radiation at the lower end of the frequency spectrum. This 

effect was predicted by the PrISM model. 

3) Background noise was high and mainly due to the cooling water pumps. 

4) The effectiveness of the system could possibly be further enhanced by increasing the 

source level and therefore the signal to noise ratio in the inlet channel. An increase of 

as much as 20dB would probably stili not disturb the seals since it is estimated that the 

signal level would have decayed to that of background within 270m from the water 

intake. 

In the environmental context: 

5) It is suggested that the sound pressure levels outside the water inlet channel are not 

suficient to cause concern with respect to the local seal population since the sound 

field of the deterrent system decays to the existing level of background noise Within 

225m of the water intake to the east and west of the inlet channel and to 8dB re 1pPa 

above background level at a distance of lOOm from the intake along the line of the 

water iniet channel. This is well within the limits set by English Nature with respect to 

acceptable sound pressure levels. It is estimated that the sound field decays to that of 

background along the axis of tile water inlet channel within 200m. 

With respect to the local sound field: 

6) The measurements taken of the local sound field indicated that sound pressure levels 

varied by a relatively small amount throughout the water inlet channel. This is due to 

the confined geometry of the channel. The sound field in this region is relatively 

uniform with high signd to noise ratio although propagation along the east side of the 

channel was consistently lower. In other words the level of sound with the system 

operating is well above the naturally occurring levels of sound in this region. 

Subncoiistech Ltd 199s 
Acoustic Suwqs of a fish Deterreni StJsteeniat Hartlepool Nuclear Power Station 

Figure 1 Map of the site and the environmental survey measurement positions 

14 

Suhacoustech Ltd I995 Document CNAI84ROI 02 
-- 

A cousiic Surveys of a Fish Delewent Svstertr ni Iiarilepool it‘uclear Power Station 

Figure 2. Environmental Survey Broadband Sound Pressure Levels 

Position 

la 

lb 

2 

3 

4 

A 

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C 

D 

E 

F 

3ackground Level with Signal/Noise Description of 

level source an ratio position 

{a> re lpPa re (d33)re IpPa

luPa 

1 40 148 8 side wall of the water 

intake 

147 152 5 side wall of the water 

intake 

1 44 149 5 outer edge of water 

inlet channel (50m 

from wall) 

134 142 8 1 OOm fi-om water 

intake wall, dead 

centre of inlet 

channel 

120 128 8 150m from water 

intake wall, dead 

centre of inlet 

I channel 

110 110 0 

110 110 0 

122 122 0 

0 

118 118 0 

124 126 2 

0 

0 

0 

0 

15 

500m east of centre 

of water inlet channel 

400m east of centre 

of water inlet channel 

300m east of centre 

of water inlet channel 

200m east of centre 

of water inlet channel 

1OOm east of centre 

of water inlet channel 

1OOm west of centre 

of water inlet channel 

200m west of centre 

of water inlet channel 

300111west of centre 

of water inlet channel 

400m west of centre 

of water inlet channel 

600m west of centre 

of water inlet channel 

Subacoustech Lid I995 Document CNA184R0102 
Acoustic Surveysof a Fish Deterrent System at Hartlepool Nuclear Power Station 

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Subucoustech Ltd I995 Document CNA184RO102 
Acoustic Sun7e51sof a Fish DeterrenfSystem at Hartiepooi Nuciear Power Station 

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Subacoustech Ltd 1995 Document CNA184ROI02 
Figure 13. Environmental Survey Broadband Sound Pressure Levels 

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centreline (m) 

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1-2 20 15m West 146.3 1 151.7 I 5.4 

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26 

SubacoustecliLtci 1995 

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Acoustic Surveysof a Fish Deterrent System at Hmtlepooi Nudeor Power Staiion 

27 

Subacoustech Ltd I995 Document CNA184ROlO2 
Acoustic Surveys of a Fish Deterrent System at Hartlepool Nuclear Power Station 

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Suhacoustech Ltd I995 Document ChA184ROlO2