## ARTHUR 

## KILL GENERATING 

## STATION DIAGNOSTIC 

## STUDY 

## AND POST-IMPINGEMENT 

## VIABILITV SUBSTUDY REPORT.

PKtPARED BY CONSOLIDATED EDlSON CGMPANY OF 

### NEW YORK, INC, PURSUANTTO THE DECEMBER 23,1993 ORDER ON CONSENT 

## IN DEC FILE NO, R2-2985-9044

JANUARY 31,1996--

-- 

# --- ---- Post-wiement 

### viability 

### offish collected 

### on the descending sides of

__I___ dual flow machines -_

was
__ evaluated by releasing live 

### fish that had been 

### marked With dye into the 

### intake bays 

### near the face 

### ofthe descending screen baskets. 

### Test fishwere released in quantities 

### of50 to 150 itEdividuais at a pint approximately one foot below the water surface 

### at the

centers of the

- entrance portals to the descending sides ofthe Ristroph-modified dual flow screens. 

### Sincethe ,c,, , 

### ____--__­ screenportal 

### entrances were not screened, test fish were afforded the opporbitfto escape. Consequently, viabiity was computed on the 

### basis ofthe numbers 

### offish recovered, 

### and not on the quantity released. 

### Is is believed, but not demonstrated, that unrecovered 

### fish swam

- ----_ - -I - - -_i­ 

### fiom the intakes and 

### thus avoided impingement.

__ - - Prehinary studies demonstrated that most fish released into intake 

### bays 

### and subsequently recovered were recaptured within 30 minutes 

### following release. Accordingly, samphg durations were approximately 30 minutes in duration. (Since collectionswere continuous during these tests, fish that were collected after the 30 minute interval were added to the 

### samples.) Fish recovered 

### alive were placed in five gallon holding tanks, and were examined 

### _--- -A for latent effects 24 hours las; B. Study Results 

### 1. Post-ImDineemen t Viabilitv Results
__,_^ ‘1 A total of 16,427 fi~”rpresentin~~~~-~ere opportunisticallycollected from one unmodified and 

### two Ristroph-modifieddual 

### flowtatgrgesfor 24 hour post-imGgement 

### ~~%sessme~attheArthur Kill 

### Generating Station 

### fiomFebruary 1994 through July

1.. 1-W-e 4). 

### A total 

### of 50 species were collected 

### on unmodifiedSCTee3 Ro.-2xGs5r 

### and 47 

### species were collected 

### fiom Ristroph-modified Screen

### Nos. 24 and 3 1, respectively. qabiity

### was calculated 

### as the percent 

### of fish alive at the 

### end 

### of the 24 

### hr latent effects 

### i /,assessment 

### period relative to the total 

### number offish collected. The 24 

### hour postimpingementViability 

### of691 8 

### fish collected from 

### unmodified Screen 

### No. 23, which was outfitted 

### with 1/8”x lf8” mesh, averaged 15.2%. In contrast, 24 hour post-impingement 

### viabity of 6,472 fish collected 

### on Ristroph-modified Screen

### No. 24, which was outfitted with 1/8”x1/2” 

### mesh, averaged 78.9%, while that for 3,037fish collected fiom Ristroph-modified Screen

### No. 31, which was outfitted witi-ll;i’;~~mesh, averaged 92.4%. The difference 

### in 

## && b overall post-impkgement viability between the 

### unmodified screen and the tw- 1 

### qNmodified dual flow screens may largely reflect the fish-saving benefits achieved with the modifications. The difference in post-impingement viability

### offish cokcted 

### on modified screen

### No. 24 relative to tnod’fied screen

### No. 3 1 is thought to reflect differences ine n and the relative 

### offish 

### collected 

### on each machine, both ofwhich 

### are di&<ssed

348

35

### i Handline/BoidinPTank 

### Effects Study rdt were initially examined to determine whether handling and holding 

### tank voiume influencsdpost-impingment viability. In order to assess handlingholding tank effects, the 

### following criteria were used for selection of data:
a. 250 or more individuals of a given species, summed across the three test screens, must have been collected, and b. post-impimgement viability of a species must have been less than 80% 

### on either ofthe two Ristroph-modified dual 

### flow screens.

&/ 

### The “minimum value” 

### of250 was selected to provide ample numbers offish for comparison of results across the three 

### tank sizes, The maximum value of 80% post-impingement viability 2­ was selected 

### so that potentially substantial differencesin viability 

### as a fbnction of 

### tank size could be detect@. 

### Data for 

### by anchovy, blueback herring. and Atlantic 

### hedngmet the
- - _-- _­ criri-fhble4). Holding tgnk-speeific post-impingement viability rates for these three species suggested 

### that post-impingement viability was influenced by the handlingholding
e volume (Table 5). 

### For example, bay anchovy collected from the fish 

### sluice and held in the 3 vbit ,I b
I?

, >. Q gallon 

### tanks experienced a 

### 77.8% post-impingement viab@, while those held 

### in 30 and 5 

# B

d -.- e:%%: .A” gallon 

### tanks had a 56.3% and 42.9% viability, respectively (Table 5). Debris sluice-collected bay anchovy held in 5 and 30 gallon tanks experienced post-impingement viabilities approximately 

### 20 percentage points lower than those for fish-sluice 

### collected fish held 

### in the same 

### sized tanks (Table 5). Similar results were observed for blueback herring and Atlantic hening. Accordingly, post-impingement viabilities reported 

### in Table 4, which reflect the summation

### ofviability data across all Sizes of holding tanks, are conservatively low. 

### Had alt fish been held in large-volume collection tanks 

### and not exposed to handling, post-impingement viability most likely would have been higher, particularly for relatively sensitive species. 

### Based on these results, data for other assessments reported herein, were selected, where required, to reflect similarity of handlingholding tank 

### size inorder to alleviate 

### thesebiases.
ii. Collection Sluice-SoecificPost-Imoingement Viabilitv Study 

### results were examined to determine whether post-impingement viabifity was different 

### between fish collected in fish sluices relative to those collected in debris sluices. Collection ---.I__ sluice-specific post-impingement viability was evaluated 

### by examining24 hr viability rates for bay anchovy, blueback herring and Atlantic herring that were held 

### in-. -.-.*---- 

# - Post-impingementviability ofbay anchovy collected in fish sluicesofboth ScreensNos. 24 and 3 1 

### combined, averaged 56.3%, while that for bay anchovy wllected in the debris sluices 

### ofboth screens combined, averaged 39.8% (Table 6). Similarresults were 

### observed for blueback herring. Fish sluice-collectedblueback herring post-impingement viabiity averaged 91 

### .PAacross the two Wroph-modified screens, while that for debris sluice collected blueback herring averaged 65.9% across the two screens. Although post-impingement

364

37

# .

.. F.". ~ -. , ..*viabiililty 

### ofAtlantic herring averaged higher for debris sluice-coUected -fish(1 9.4%) than for fish 

### sluice-sluicecollected 

### fish(1 1.I%), the overall

### viabilitywas relatively low. Examinationof 

### opportu~stically-collected fish, sutnmed 

### across all species and 

### all holding tanks, indicated that post-impingement viability was higher for fish collected in the fish sluices (89.1%) 

### than for 

### those collected in the debris sluices (67.5%). Although it is believed that exposure to the 

### high pressure spray wash may reduce post-impingement viabiity, it 

### is also possible 

### that the reduced viabiity of fish collected in the debris 

### sluices may reflect reduced transfer efficiency 

### ofdead fish 

### fromthe screen baskets. Transfer 

### efficiency tests 

### (discussed below) 

### showed that only 39.1%of

### the dead fish were collected in the 

### fish sluices, while 69.5%of the live fish were collected in those 

### sluices. 

### This difference

### may #e due 

### to the ability of live fish to flop, 

### in contrast to dead 

### fish, which 

### can only slide out of the screenbasket. Overall, the results demonstrated substantial viability 

### for debris sluice-cotlected fish, which suggests 

### that these fish should 

### be returned to the waterway in addition to those collected fiom the fish sluice.
iii Bluecrab Post-ImDineementViability Post-imPingementviabity of 220 bluecrabs collected from unmodified screen 

### No. 23 was 99.1%, while that for 1,029 bluecrabs collected fkom Ristroph-modified screens 

### Nos 24 and 31 

### combined,was 99.6%at the end 

### ofthe 24 hour latent effects assessment period (Table 

### 7). The high viability for bluecrabs on the unmodified screens suggests that Ristrophmodifications to the dual flow screens are not necessary for protection of these organisms 

### at water intakes.
2. Effects of Food Availability on Post Impingement Viabilitv _I
J. Ai\\ ,P 

### Bay anchovy collcted fiom Screen

### No. 24 during September effects of availability 

### on post-impingement Viability.

fish sluice that were 

### fd post-impingement viability at the end ofthe 24 hour latent effects period was 84.9%, while that for the 1,574 bay anchovy that were not fed 

### was 83.5%. 

### For bay anchovy collected 

### from the debris sluice, the post-impingement viability of 558 fish that were fed during the 24 hour interval was 74.4%, while that for 439 fish that were not 

### fed was 64.2%(Table 8). Examination disclosedthat fish that had been fed, induding both fish that were alive and 

### as well 

### as thosethat died during testing, did have food in the gut. 

### These results suggest 

### that the availability 

### of

### food was not aprinciple facror in post-impingement viabitity.

3940 x41-- 

## ----- --- ----

------- e

3. Effects of Screen Mesh Size on lmpineernent and PostImoineement Viabilitv 

### i Minimum Size of Fish FmDineed as a Function of Screen


### As a means 

### to assess size-selective impingement 

### as a Ibnction ofmesh 

### size, the minimum length ofeach ofthe fivemost abundant species offish collected during the September 1991 

# - September 1992Impingement Study 

### as well during the 

### February 1994

# - July 1995 postimpingementviabiity substudy were listed (Table 9)- 

### The minimumlengths of fish collected 

### on the 1/41‘_x1/2” 

### to 62 mewchile the 

### fi%-l&-&-soffish mesh 

### ranpd-fhm 34 

### mm zII__*_-Ic­ mesh ranned_fiamB,~5&m. The minimum lengths of 

### collected on the 1/8”x1/2”

----_e I ­ -_ - - 

### xn~h these five specieobserved on the 1/8”x1/8” 

### raged fi~m-2&mm..to-6l-mm. The smallest 

### fish collected 

### on the 

### 1/4”x1/2” mesh was 

### 11 

### mm larger 

### thanthe smallest fish collected fromthe other two meshes. 

### This difference may reflect the approximatedifference 

### in size of

### fish 

### that would 

### be subjected 

### to entrainment with 

### 1/4”x1/2” mesh 

### and 1/8”x1/2” mesh 

### on 

### Arthur kill dual flow 

### scrwns.

- - - Among the five most abundant species of fish impnged, two species, blueback herring and __-- Athxitic 

### h&@, may be subject to little or no entrainmentimpacts, regardless ofthe size me that &ght be used on the 

### screens. Blueback herring collected during 

### this studywere 

### all greater 

### than 58 

### mm in length, while the minimum size ofthe individuals observedthe 1991­ 1992 studywas 

### 55 mm (L,MS 1993). Since these sizes are substantially largerthan the 

### 9­ smallest 

### fish collected on the 

### 1/4”x1/2” mesh, and none were recorded in entrainment ,,a 

# - - samples, it is unlikely that blueback herring would be subject to entrainment regardless

### ofthi size mesh applied. Minimum 

### lengths of Atlantic herring impinged on the three mesh sizes were also quite similar, ranging from 33 

### mm to 34 mm. The size distriiution 

### ofAtlantic herring collected during the September 1991 

# - September 1992 impingementstudy indicated that morethan 98% 

### ofthe individuals collected were greaterthan 34 mm in total length (LMS 1993). Examination 

### ofthe entrainment data collected during October 1991-September 1992 studyindicated that Atlantic herring constituted only about 0.5% 

### ofthe post-yolk 

### sac larvae 

# -

I *- collected. QuantitiesofAtlantic herring collected on Screen

### Nos 23 and 24 duringthis study 4 were substantially greater than those on Screen 3 

### 1. Ifthe Atlanticherring were relatively un‘rformly distributed across the intakes during these studies, the relatively fewerfish collected Il on Screen 3 

### 1 suggests

### that they were entrainedthrough its 1/4”x1/2” mesh, but were 

### impmged on 

### the smaller mesh on the other 

### two screens. The relative abundanceofAtlantic herring 

### in the post-impingement viability collections 

### &om ScreenNo. 3 

### 1 were substantially lower than those fromthe other 

### two screens. If Atlantic herring were relatively uniformly exposed to 

### the three intakes, the reduced abundancein Screen

### No. 3 1 collections suggests

I_ ----I----­ that 

### theywere entrained. Accordingly, it appearsthat in order to minimize e-of 

# ‘ ,/ Atlantic herring 

### to t, the smallest-sized mesh practical might be r-qqi-:.

- The minimum lenghbay anchovy collected on the 1/4”x1/2” mesh was 46 mm, while that on 1/8”x1/2”was 23 mm, and that on 1/8”x1/8 mesh was 26 mm. Although the size distribution ofbay anchovyimpinged during the 1991-1992 study indicated lW/o ofthe fish were greater

42---- 

### than 33 mm, given that abay anchovy as small as 23 

### mm was collected during this study suggests that substantial entrainment through 1/4”x1/2” mesh would 

### be likely. Examination of entrainment data collected during the September 1991-1992 study indicated that bay anchovy contributed nearly 74% 

### of all larval life stages of organisms collected. 

### These results reflected entrainment through the 1/8”x1/8” mesh. Accordingly, in order to minimizethe entrainment ofbay anchovy, the smallest 

### mesh practical would appear toberequired. The minimumlengths ofAtlantic menhaden and Atlantic silverside observed dwing the 1994 

# ­ 1995 study, 

### as well as during the 1991-1992 impiigement 

### and entrainment study (the minimum hgthspecimen ofAtlantic menhaden impinged was18 

### mm; that for Adantic silverside was 35 mm; 

### post-yolksac larvae of both specieswere present 

### in entrainment samples) suggest that the 

### -_ smallest practical mesh size would also

- --

### appearto be required inorder to entreenteffects 

### on these species.

- ii 

### &’ Post-ImoineementViability 

### as 

### a Function of Fish ’36, Post-impingementviability of bay anc ion 

### oflength was evaluated using data collectedfiom Screen No. 24 duri for this analysis was limited to that obtained from only Screen

### No. ers ofbay anchovy were collected !?om 

### Screen

### No. 3 1, and collections fio -23were not used because that machine was not equipped with the Ristroph-type modifications. The 668 bay anchovy collected alive fiom Screen 

### No. 24 on August 23, 1995 were held in 300 gallon 

### tanksfor 24 hour latent effects assessments. A total of486 ofthe fish were collected fiom the 

### fish sluice; 182 were obtained 

### from the debris sluice. Collections fiom each sluice were held separately. At the end of the 24 

### hr latent effects assessment period, all fish were measured to the nearest 

### nm and recorded 

### as to condition (alive, dead). Data were then tabulated into 10 mm length increments for computation ofpost-impingementviability 

### as a fbnction of length category. (Insuficient numbers of fish were available for evaluating viability 

### as a fiinction of smaller length categories (e.g. 5 

### mm)). Post-impingementviability of fish sluice-collected bay 

### anchovy was relatively uniform across the 5 length categories eyduated, and;with

### no clear tendencies (Table 10). Viability 

### offish in the 

### 30-40

### mm length category, which was the shortest length category, was 20.3% while that in th 1 0 

### mm Category, which was the 

## -~

”--%------ Post-impingem viability ofdebris sluice-collected fish largest length ~ategory~..was273~h- 

# --4? -hi@iG.- *G-mgedfrom 50% for 

### fish in the 30-40 

### mm category to 75% for fish in 

### mm category. Although tenuous, these results suggest that somewhat higher

I probably occurs among larger fish. Bay anchovy collected during the 

### February

# - May periodsinasnaaDd 1995had Dost-impingement viabilities above _-­ -~- Wh. Fish durinrin*s S 1993). 

### HoweGer, viability of period o f j & M
5_---__-_ basovy collected during summer months were lower when collections contained ’ substantial numbers of smaller young-of-the-year fish.

443

## tl I 

### vs

45fish (Table 4). Weakfishpost-impingement 

### viabiity following release on

### the descending sides ofthemichines ranged fiom 2%

### to 73%, while 

### that for bay anchovyranged fiom 13% to 18%. Althoughthe lowViability during the tests with these species may reflect stresses lLssocilifed with collection on the descending sides 

### ofthe machines, they might also reflect the added stresses asLssociatedwith the handling, including marking and releasing through a 2” pipe that the test fish incurred.



### VL Screen Face Velocitv Profile Studiesand AssessmentofBenefits ofFlowmDrovine Fairineson Post-ImDinPementViability A. Introduction Velocity profiles were measured at unmodified Screen

### No. 23 and the two Ristroph-modified dual flow screens(Nos. 24 and 3 1) at the

### Arthur Kill Generating Station. 

### The purpose ofthe profile measurementswas to determinethe distribution 

### ofthe velocity and direction offlow along the ascending and descending sides ofthe machines, and to apply the results in evaluationsofpost-impingement 

### viabiity offish. 

### In addition, the profile studieswere performedto help evaluatethe benefits of flow-improving fairings on post-impingement 

### viabiity of fi&-.


### B. Velocitv Study Methods and Materials Measurementswere made at fiveuniformly distributeddepths along 

### six vertical transects 

### on both sides of Screens

### Nos. 23 and 24. Although measurementswere made along six vertical transects on 

### Screen

### No. 31, because its submergedportion 

### is only 14.5 

### ft in length at mean sea level (versus 25.5 

### ft for Screens

### Nos.23 and 24), measurementswere taken at only three depths. 

### Three ofthe 

### six Vertical transectswere uniformly spaced in the “upstream” one-third 

### ofthe width 

### ofthe screenbasket. The other three wereuniformly distributed 

### across the “d0~n~trea.m’~ two-thirds ofthebasket (Figure 15). 

### This vertical transect distributionwas designed to detect principle flow characteristicspreviously noted at the face ofdual flow screens during flume studies (Figure 5). Measurementswere made with a Marsh-McBknq Model 5 11 electromagnetic2-axis water current meter, identicalto that used by Fletcher (1994). The instrument was attached 

### to the lower rail 

### of a screen basket 

### so that the meter probe was positioned midwaybetween the top and bottom rails. The basket was then rotated 

### into 

### the water intake to the specified depth for determination of

### X,Yflow velocity components. Three readings ofthe 

### X,Y componentsofflow were made at 20 second intervals at each transect and depth position. These were then rduced 

### to velocity and 

### angular components ofthe flow. Resultant values were averagedverticallyto generateflow vel~dy and anglevectors acrossthe ascending and descending sides 

### ofthe screens. &esults 

### fiom unmd@edScreenNo. 23 and Ristroph-modified Screen

~

### No.
_x ---__XL_-_I-~-~v*--=--­ --. ___m-__l -=---- 

### - --A-n_ 

# __ ~ ~ 

### - 24 were comparedto evaluate

~ the effectiveness ofthe fairing deviceinstalled on the modified screenin enhancingthe

491

Flume-measured velocity profile

the face of a

. simulated dual

flowwater intake screen without a flow-improving fairing.

Intake Forebay

Figure 15. Horizontal placement of velocity profde measurementpoints (A through

### F) at the ascendingand descending sides ofdual flow screen baskets at the Arthur Kill Generating Station.

Source: afterFletcher 1994 50addition, comparisons of results were made between Screens

### Nos. 24 and 3 1 to evaluate differences in intake flow velocity on the angular components of 

### the flow at the face 

### ofthe screens. [The calculated velocity 

### at the face of the mesh at Screen 

### No. 3 1 is approximately 1.3 fps, while that at Screen No. 24 is 0.9 fj>s (Table l)] Velocity profile measurements were taken during flood and ebb tides between one hour either side ofhigh or low slack tide stage. Before velocity profile measurementswere made, tests were performed to determine whether stray electrical currents or the metallic mass ofthe screen would interfere with the electromagnetic flow meter. Electrical current intderence

### was evaluated 

### by adjustment of the Marsh-McBirney meter circuitry. Metallic 

### mass interference was evaluated by substituting a mechanical meter for the Marsh-McBirney electromagnetic meter.


### C. Study Results Tests performed to determine the presence 

### of stray electrical currents that might intdere with the electromagnetic water current meter demonstrated that no interference was present. However, tests revealed that the meter's electrical supply cable could interfere with readings. Adjustments were made to the placement ofthe cable and interferencewas eliminated. Tests performed to determine whether the metaIlic mass ofthe dual flow screen and associated materials might interfere with the electromagnetic water current meter suggested that interference, if any, was minimal. Mechanical meter readings were within 2%, 8.5%, and 16.2%ofthe electromagnetic meter readings for Screens 

### Nos 23,24, and 3 1 , respectively (Table 13). Flow prof3e measurementsdemonstrated that velocities were generally uniform over the depth at each vertical transect, but with slightly lower velocities near the bottom at some locations 

### (LMS 1996, Appendix A). Velocities generally decreased with increasing distance fiom the upstream end ofthe screen baskets, while approach angle generally increased with increasing distance fiom the upstream end ofthe machines (Table 14; Figures 16, 17, 18). Flow velocities and approach angles across the of Screen 

### No. 23, which was not outfitted with a fiont-wall fairing, differed from those at Screen No. 24, which was outfitted with a



### upstream end 

### ofthe wc

-.-e­ f downstream direction, while that on Screen No. 24 was generally more uniform across the 

# -*5 +-~~ No. 3 1 ,because

cx 

### - *- A central part ofthe mesh. At

## 5%~

____ of
- its shorter velocities were tb P­ ,I ;22{ \ mo-er

# --_ __ -~ZT-==--k-= 

# d. than thejiG&acGg&$u& App ;"fi 

## ­ betwe%%E two 

### Gens. Overall, velocity and approach angle data (Figures 16, 17, and 181, suggest that the fairings did make the horizontal distribution of flow across the screen 

### baskets

515253PUMP BAY

FOREBAY

7 fps 2fps 

# .s SCALE

Figurt 16. Veiocity Vector Distribution atArthur Kill Dual 

### Flow 

### Screen No. 23.



## source: LMsi996
54 0PUMP BAY

0 1 fps 2fps I * 

# s SCALE

Figure 17. Velocity Vector Distribution at Arthur

### Kill Dual How Screen No. 24 when outfitted with a Front-Wall Fairing.

55

# - 0 I fps 2fps

SCALE

Figure 18. PUMP BAY

Velocity Vector Distribution at Arthur KiIl Dual Row Screen

### No. 31 

### when outfitted with a Front-Wall Fairing.’

--- more 

### dorm,which may have reduced, somewhat, the velocities at which fish might be impinged 

### on the mesh.

D. Effects ofFlow-Imoroving FairinPs on Post-Imoineement Viability

/- Flume

### testing demonstratedthat semi-elliptical fairings at the headwall 

### of dual flow 

### screens could 

### cause intake flowto 

### be more uniformly distributed horizontally across the face of screen 

### baskets (Fletcher 1994) 

### and presumably enhancepost-impingement viabiiity offish by reducing the velocity of

### flow at which they were impinged. Accordingly, plans were made to evaluate

### whether 

### fairings installed 

### on the Arthur Kill Ristroph-modified dual flow screens would improvepost-impingement viabiiity. The procedure for evaluating thebenefitsof

-* - fairings included collectingviability data before the fairings were instailed for comparison with /\

~ 

### data collected after installation. The effects of fiirings on post-impingement viability was ,x’ ‘

## /6 J “i expected to be most rdiy detected on speciesexperiencinglow to moderatepost- \ pi- ”: impingementviability 

### on screens without fairings, for which ample margin for improvement

\ i\ w ’ was available. Examination ofpost-impingement viability data obtainedprior to installation of the fairings in May and June 1994 (Table 

### 15) disclosed that Atlantic herring would be the most appropriate

### speciesfor assessment. (e.g. Post-impingementviability 

### of 395 Atlantic herring collected fiom Screen

### No. 24 was 22.3%). All other species collected in abundance (e-g. > 50 fish) demonstratedpost-impingement viabilities near 

### lW/O. Accordingly, plans were made to comparepost-impingement viability levels for Atlantic herring collected during

# i Spring 

### 1995 (fairings in place) with Atlanticherring data collected during 1994 before the fbirings were installed. During 1995 intensive sampliigbeginning @ March and continuing into June produced only 18 Atlantic herring 

### on the fairing-outfitted screens. Viability of 16 Atlantic herring collected 

### on Screen

### No. 24 

### was 12.5%, while that for the two 

### fish caught 

### on Screen

### No. 3 

### 1 was 

### SO?!. 

### In contrast, a total of 576 Atlantic herring were collected on unmodified ScreenNo. 23 during 

### the sametime interval (Table 16). Because 0-aucity ofAtlantic herring in collections



### __ -+ 

### fiom the two Ristroph-modified screens3Gssments oft&-k-n&ts ofthe fiont-wal-fhg? ~~c~gpas~-im~n~ement~~~d not

- -

~ - planned. CGip&&%<f

- _-- be performed 

### as post-impingement viability-of other species collected during the same time intervals in each of 

### the two years did not provide any insite into the benefit ofthe the fairings in enhancing postimpingement viability generally becaup their pre-fairing viability was relatively 

### high. iL;

57.... ,:

j I f

58

# t I I I 1 I 1 i I

I 1 I I ,mi-w.& I I 1 I 

# I

i 1 1 I I I I i i I 1 I I I I I 1 I I 1 

# I c.bpt23-3 1 .uI.

59