1 

### MEMORANDUM

Tetra Tech, Inc. 400 Red Brook Blvd., Suite 200 Owings Mills, MD 21117 phone 410 - 356 - 8993 fax 410 - 356 - 9005

DATE: August 13 , 2008 TO : Paul Shriner, EPA FROM : Ann Roseberry

L incoln, Henry

L atimer and Blaine Snyder SUBJECT: Imp ingement and Entrainment Sampling Methods We’ve prepared this memorandum in response to your request for information on “ty pical” impingement and entrainment sampling methods. There are no published “standard methods” for impingement and entrainment sampl ing; however, there are some fundamental study elements and parameters that are universall y essential for the completion of imping ement and entrainment survey s. The following method descriptions may serv e as general guidance and assume that the reader has a general understanding of impingement/entrainment definitions and impacts. I MPINGEMENT A BUNDANCE S TUDIES Study Design Impingement studies, whether for assessment of abundance or survival, should be designed to evaluate annual, seasonal, and diel variabi lity exhibited by

potential ly impacted organisms, and hydrographic variability that may influence the numbers or organisms present near the intake. Young and Dey (2003) point out that “Life histories of many of the affected species are complex, involving o nl y temporary occurrence near the power plants and/or long annual migrations, making them extremel y difficult to sample for some parts of the life cycle. Invariabl y, all fish in a cohort do not follow the same life history pattern.” Unless historical data indicate otherwise, this ty pically requires a year round weekl y or bi

- weekly sampling program. Historical data may show that fish and2

shellfish activity

diminishes during part of the ye ar and sampling e ffort may be less intense, or (for example) may show that a particular species of concern is present during a particular time and sampling effort should increase. During sampling events, data collection should cover the entire dail y and (where appro priate) tidal cycles. Ty pically , impingement samples are col lected continuously for 6 or 8 hours, and repeated to cover an entire 24

- hour period. Stratifying collection in this manner allows an anal ys is of the diel variation exhibited by man y aquatic organisms. The specific stratification scheme should be selected to fit the specific objectives of the study and patterns exhibited by all of the species of concern. For example, Spicer et al. (2000) stratified sampling b y “day” (8 AM until 8 PM) and “night” (8 PM until 8 AM) in studies conducted at the Comanche Peak St eam Electric Station in Texas , a facility located on a man - made reservoir with little impingement due to poor habitat quality near the intake . In contrast, Heimbuch et al

. (2007) collected samples for four 6

- hour collection periods for the Charles Poletti Power Project to investigate potential impacts to the New York

- New Jersey estuary and Long Island Sound

. The study design must include an integrated quality assurance/quality

control (QA/QC) management plan that presents sampling design and method specifi cs, and addresses data quality objectives, measurement performance criteria, anal yt ical methods, and field and laboratory

QC requirements. Sampling Location Samples should be collected from the screen wash discharge trough or fis h return s ys tem. If fish return survivability studies also will be conducted, the sampling location should be as close to where fish enter the receiving water body as feasible, to ensure that the survivability

accounts for all impacts that fish would incur if not collected for stu dy . If survivability

studies will not be conducted or fish are ty picall y (b y design) not returned to the water bod y, collection can occur at an y accessible point in the screen wash sy stem. Samples should not be collected from the water body area ahead of the intake screens (unless the intent is to obtain data describing the numbers of dead or moribund fish and shellfish that may

subsequently

be impinged)

. Sampling Apparatus and Collection Samples should be collected in nets or debris baskets fitted with s uitabl y s mall mesh size (at a minimum equal to , and preferabl y slightly smaller than the intake screen mesh size ). The collection device should be of sufficient size to filter the entire wash stream and to contain the volume of debris, detritus, and imping ed organisms likely over the total collection duration. If the collection device cannot contain the entire debris/detritus/organism volume, the collection device must be checked and emptied at sufficient intervals to eliminate the potential for overflow or loss of impinged organisms from the sample. Moreover, if survival studies will be conducted, the impinged organi sms should be transferred to a holding area regularl y to avoid additional damage b y compaction within the collection device. Live fish should b e handled as little as possible3

to minimize stress, and should be held in conditions close to, if not identical to , their source waters. Water should be kept ox ygenated and holding tanks should be large enough to hold the fish with minimal stress ( Kelsch and Shields, 1996 )

. Prior to sampling, the intake screens and screen wash discharge trough or fish return sluiceway should be carefully

washed to remove any

previously

impinged and trapped organisms. The collection device should be inspected for holes or o ther damage that would allow impinged organisms to escape, and then secured in place in the discharge stream. The time that sampling begins should be noted, along with initial conditions. I f the volume of impinged organisms (and/or detritus) is very large, it may

be necessary

to empty the collection device during the sampling event to prevent overtopping of the device and loss of organisms. At the conclusion of the sampling event, the intake screens should again be carefull y washed to ensure that all organi sms impinged during the sampling time frame are collected. The end time and conditions for the sampling event should be recorded. The sample should be carefully transferred to an appropriate holding area for immediate taxonomic identification. Impinged o rganisms can then be identified (species

- level identification is preferred ; or the lowest feasible taxon for damaged organisms) , measured, weighed, and their condition (live, dead, injured, etc.) recorded before being returned to the receiving water body. In rare cases, sample sizes may be too large to measure and weigh each individual. Only in those cases, it may

be acceptable to subsample ; subsampling should be avoided under most circumstances. If subsampling may be required, a statistician should be cons ulted to ensure that the subs ampling design provides statistically

useful results. Data collected may

vary depending upon the specific facility and stud y requirements, but should include some description of environmental conditions, hydrologic conditions, intake sy stem operational conditions, and organism

- spec ific information. Example primary data elements or parameters include the following:

 Environmental data: water temperature, dis solved oxygen, pH, conductivity or salinity (if applicable) , and turbidi ty  Hydrologic conditions: river flow or tide stage
 Intake system o

perational conditions: intake pump flow rate , screen spray wash pressure and schedule , traveling screen change rate
 Organism data: species, lifestage, length, weight , and condition (live or dead) Additional data might include: air temperature, cloud cover, wind speed, wind direction, current direction, precipitation levels or recent precipitation events, degree of icing, and general observations such as debris loading, debris ty pe, and wheth er or not confounding conditions occur (such as unrelated local fish kills observed in the vicinit y). Representatives of each species and lifestage should be preserved (or photographed) as vouchers for QA evaluation purposes

.4

Measuring Collection Efficien cy and Re

- impingement Rates Measurements of impingement abundance may be underestimated if the study ’s collection efficiency

is less than 100 percent, or overestimated if re

- impingement occurs. Fortunat el y, both can be measured relativel y easily with some forethought. If collection efficiency is to be measured, it is important to obtain a suitable sample prior to the start of the study . The collection efficiency sample should represent the variet y of species and organism lifestages anticipated in the impi ngement study. Ideally this control sample will be collected about the same time as the impingement study , in proximity to the intake structure. The sample should be col lected using collection gear ty pes suitable for the capture of species likely to be imp inged (e.g., trawl, seine, or electr ofishing unit). Organisms should be identified, measured, counted, and marked with fin clips, dy e, or another method that allow s for rapidl y identifying the organism as a collection efficiency organism. The marked indivi duals are then released immediately ahead of the intake screens under operating conditions identical to those anticipated during the impingement study . The sample is collected using the same apparatus and methods as for the impingement study , and the marke d individuals identified to species, counted, and measured. The collection or recovery results are compared to the released records to determine the collection efficiency

. Reimpingement may

occur if tidal or other currents transport fish from the dischar ge or fish return s ys tem back to the intake. Reimpingement rates can be determined by marking impinged individuals, releasing them into the discharge or fish return s ys tem, and determining the number that are collected a second time. E NTRAINMENT A BUNDANC E S TUDIES Study Design Like impingement studies, entrainment studies for abundance or survival should be designed to evaluate annual, seasonal, and diel variability exhibited by

potentially entrained organisms, and hydrographic variability that may influe nce the numbers or organisms present near the intake. A ccording to Snyder (1983), “Most larval fish investigations require sampling from twice a week to twice a month depending on objectives. Except for exploratory purposes, monthly

or less

- frequent sampli ng is of very limited value

— entire species or cohorts may be missed, even when sampling is somewhat more frequent.” On the other hand, regional fish spawning information suggests that entrainment may be very low during cold months in northern and inland ar eas in the United States (see attached figures). Therefore, unless historical data indicate otherwise, a well

- designed entrainment abundance study requires a ye ar - round weekl y or bi

- weekl y sampling program, with increased sampling frequency when egg and la rval entrainment increases. During sampling events, data collection should cover the entire dail y and (where appropriate) tidal cycles. Entrainment samples are collected over an entire 24

- hour period, although collection of each individual sample may last as little as 5 to 10 minutes5

in the case of towed plankton nets or plankton trawls, or from 1 to 3 hours for pumped samples. For example, Heimbuch et al. (2007) collected at least 100 m 3 of water using a gasoline

- powered trash pump during 1 hour of pumpin g, and repeated that effort for a total of four samples over 24 hours at the Charles Poletti Power Project in New York

. On the other hand, Melton and Serviss (2000) conducted paired

- net plankton tows lasting 30 minutes each in the discharge canal of the Fl orida Anclote Power Plant, which exhibits low flow co nditions and required lengthy tows to ensure adequate sample collection. The study design must include an integrated quality assurance/quality

control (QA/QC) management plan that presents sampling desi gn and method specifics, and addresses data quality objectives, measurement performance criteria, anal yt ical methods, and field and laboratory

QC requirements. Sampling Location Samples should be collected from the cooling water intake s ys tem, downstream of the intake screens, if possible. Sampling directly after the intake screens ensures that the sample contains organisms actually entrained and that the organisms have suffered the least possible phy sical damage, thereb y facilitating proper identificatio n. However, i f entrainment survivability studies also will be conducted, the sampling location should be as close to where the cooling water discharges as is feasible, to ensure that the survivability

accounts for all impacts that entrained organisms would incur if not collected for study

. Samples should not be collected from the water body ar ea ahead of the intake screens (unless the intent is to obtain data describi ng the numbers of dead fish/ shellfish eggs and lar vae that may subsequently be entrained )

. For all entrainment sampling i t is important to collect samples from all depths (e.g., b y oblique net tows or pumping from multiple depth intervals) , as ichth yoplankton frequentl y exhibit patchy distribution vertically

( as well as horizontally

and temporal ly)

. Sampling Apparatus and Collection Samples may

be collected directly

from the intake screen discharge stream, or water (taken downstream from the intake screens) may be diverted and pumped to the sampling location. Ineither case, s amples should be c ollected in plankton nets with suitably small mesh size and sufficient length to adequatel y filter the water and to collect the entire sample. Care should be taken to minimize damage to the sample due to extrusion or overloading, resulting in compaction of the collected organisms. Kelso and Rutherford (1996) recommend a minimum net area to mouth area ratio of at least 3:1 and preferabl y 5:1 to minimize net clogging and extrusion. Ty pical mesh sizes range from 333 to 505 μm. If the sample is collected direct ly from the discharge stream, the net should be fitted with a flow meter in its mouth so that the volume of water filtered can be calculated

. The net may be towed within the stream or it may be fixed to a suitable phy sical structure, if available

. If a pump is used instead, the piping leading from the pump to the net should be fitted with an in

- line flow meter, and the pump should be selected to minimize damage to entrained organisms ( Kelso and Rutherford 1996 ). Bowles and Merriner (1978) present a thorough review of entrainment sampling gear

.6

Prior to sampling, the collection nets should be carefully washed to remove any

attached organisms , inspected for holes or other damage , and a removable collection cup should be attached to the terminal end of the ne t . F low meters should to be set to zero or their initial readings recorded . If a pump is used, the pump should be flushed thoroughl y with clean water prior to sampling , to ensure that no ichthyoplankton remain within the chamber. The pump is then fitted into place with the inlet withdrawing from the intake screen discharge stream

. If the pump cannot be flushed with clean water, then it should be run for several minutes prior to starting collection to ensure that the sample collected represents the current c onditions . The net is then positioned to collect the pumped water sample . To minimize any additional damage to the entrained organisms, the net is placed verticall y into a container of water with an overflow outlet. The sample flow is directed into the center of the net. During the sampling period, the pump inlet should be raised/lowered periodically to obtain a depth

- integrated sample. The time and operating conditions are recorded when sample collection begins and ends. If a towed plankton net is used, the clean net (with flow meter attached) is deploy ed in the intake screen discharge stream and towed again st the current for a known time (e.g., from 5 to 10 minutes at 1 to 2 meters per second) . Towing speed should be fast enough to minimize larval avoidance, but slow enough to ensure adequate filtering. Multiple depths should be sampled, either by deplo yi ng multiple nets at s pecified depths or by employing stepped oblique tows. At the completion of the pump or net tow sampling event, the time and flow me ter readings are recorded (to allow calculation of sampling duration and sample volume) and the collection net washed so that the entire sample flows into the removable collection cup at the end of the net. The collection cup is removed and all contents ar e placed into a sample jar (or the sample transfe rred). Samples are fixed or preserved by adding 5

- 10% formalin. P reserved entrainment samples are sent for laboratory identification by

an ichthyoplankton taxonomy specialist. Entrained organisms are picked from detritus in the laboratory

using side lighting and a high

- contrast background for better visibility , and are stored in 5% buffered formalin. Ichth yoplankton are identified with the aid of a dissecting or low

- power microscope. All fish and shellfish e ggs and larvae are identified to the lowest feasible taxon (species preferred). Data collected may

vary depending upon the specific facility and stud y requirements, but should include some description of environmental conditions, hydrologic conditions, i ntake sy stem operational conditions, and org anism

- specific information. Example primary data elements or parameters include the following:

 Environmental data: water temperature, dissolved oxygen, pH, conductivity , and turbidity
 Hydrologic conditions: rive r flow or tide stage
 Intake system o

perational conditions: intake pump flow rate7

 Organism data: species, life stage, length Additional data might include: air temperature, cloud cover, wind speed, wind direction, current direction, precipitation levels or recent precipitation events, degree of icing, and general observations including an y confounding conditions. Measuring Collection Efficiency and Re

- entrainment Entrainment rates can be underestimated if collection efficiency is less than 100%, and over estimated if re

- entrainment occurs. It is possible to measure both collection efficiency and re

- entrainment if suitable fish eggs and larvae are available for the study

. The ichthyoplankton sample used to measure these potential sources of error can be col lected from source waters and should be stained with a suitable biological stain (e.g., rose Bengal) prior to the study

. If collection efficiency is to be measured , a stained and counted ichthyoplankton sample is released immediatel y i n advance of the int ake screens, such that 100% entrainment will o ccur. Entrainment sample c ollection proceeds as described above and the number of collected organisms compared to the number released to determine collection efficiency

. T o measure re - entrainment, stained and c ounted ichthyoplankton are released into the discharge stream near its terminus so that the sample discharge s to the receiving waterbod y. Entrainment sample collection proceeds as described above and the number collected subsequently

is the number re

- entra ined. R EFERENCES Bowles, R .R. and J.V. Merriner. 1978. Evaluation of Ichthyoplankton Sampling Gear Used in Po wer Plant Entrainment Studies. Pages 33

–43 in L

. D. Jensen, editor. Fourth National Workshop on Entrainment and Impingement, 5 December 1977, Chic ago, Illinois. Sponsored b y Ecological Anal ys ts, Inc., Melville, NY. Published by EA Communications, Melville, NY. Heimbuch, D.G., D.J. Dunning, Q. E. R oss, and A.F. Blumberg. 2007. Assessing Potential Effects of the New York

– New Jersey

Harbor Estuary

and Long Island Sound. Transactions of the American Fisheries Society 136: 492

– 508. Kelsch, S.W. and B. Shields. 1996. Care and Handling of Sampled Organisms. Pages 121

– 144 in B.R. Murphy and D. W. Willis, editors. Fisheries Techniques, 2 nd Edition. American Fisheries Society , Bethesda, MD. Kelso, W. E. and D .A. Rutherford. 1996. Collection, Preservation, and Identific ation of Fish Eggs and Larvae. Pages 255

– 302 in B.R. Murphy and D. W. Willis, editors. Fisheries Techniques, 2 nd Edition. American Fisheries Soc iety , Bethesda, MD. Melton, B. R. and G.M. Serviss. 2000. Florida Power Corporation

- Anclote Power Plant Entra inment Survival of Zooplankton. Environmental Science and Policy 3: S233

– S248.8

Snyder, D.E. 1983. Fish Eggs and Larvae. Pages 165

– 197 in L .A. Niel sen and D.L. Johnson, editors. Fisheries Techniques. American Fisheries Society, Bethesda, MD. Spicer G., T. O’Shea, and G. Piehler. 2000. Entrainment, impingement and BTA evaluation for an intake located on a cooling water reservoir in the southwest. Env ironmental Science and Policy 3: S323

– S331. Young, J.R. and W.P. Dey . 2003. Uncertainty and Conservatism in Assessing Environmental Impact under §316(b): Lessons from the Hudson River Case. Pages 30

– 39 in D.A. Dixon, J.A. Veil, and J. Wisniewski, editors . Defining and Assessing Adverse Environmental Impact from Power Plant Impingement and Entrainment of Aquatic Organisms. Swets & Zeitlinger B.V., Lisse, The Netherlands.