p.1 

r 

5.0 Impingement Effects 

200 

180 

160 H 

?14 0 o 

= 120 

I State Total 

I Monterey Area 

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 

Source: CDFG Landings Summaries 1986-1998. 

Figure 5-5. Commercial market squid landings reported for California and Monterey area. 

Landings of squid can fluctuate drastically from year to year, but, despite intense fishing 

pressure, have not exhibited a steady decline that would indicate overharvest (Starr et al., 1998). 

Squid abundance and harvest is generally low during El Nino years, such as 1983/1984 and 

1998/1999. In recent years, market squid landings at Monterey area ports have ranged from over 

30 million pounds during a peak year in 1994 to around 185,000 pounds during 1998 (CDFG 

Landing Summary). Although subject to these great fluctuations, the market squid fishery is 

frequently among the most profitable fisheries in the Monterey Bay area. 

5.3 Impingement Effects 

Northern anchovy Engraulis mordax was the most abundant fish species collected from both 

intakes and constituted 61 percent of all fishes impinged. Shiner perch Cymatogaster aggregata 

ranked second in abundance at 9 percent, followed by topsmelt Atherinops affinis (9 percent) and 

Pacific herring Clupea pallasi (4 percent). These four species accounted for 83 percent of all 

fishes impinged during the entire study. 

Northern anchovy was the most abundantly impinged fish from both intakes. They were 

impinged in highest numbers during the summer and early fall months and were present in very 

low numbers during the winter. Peak impingement occurred in late August and early September 

at both intakes: 19,077 at Units 1 through 5 and 90,160 at Units 6 and 7. Based on laboratory 

growth rates, it was surmised that the northern anchovy impinged during the summer and fall 

were spawned during the previous spring. 

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5.0 Impingement Effects 

Shiner perch was the second most abundant fish collected at Units 1 through 5 (26,000) and the 

fourth most abundant at Units 6 and 7. They were collected throughout the year but peaked 

during their spawning period in the spring and summer months. Shiner perch are live-bearers 

and the majority of shiners impinged were young-of-the-year. It was thought that gravid females 

may have prematurely released their embryos when the came into contact with the screens. 

Topsmelt was the third most abundantly impinged fish at Units 1 through 5 (13,000) and the 

second most abundant at Units 6 and 7 (16,000); overall this species constituted 8.8 percent of all 

fishes collected. They were impinged throughout the year, with peak abundance from October 

through December. Large schools of topsmelt, which may have been associated with spawning 

activity, were observed in the harbor during the fall and early winter. 

Pacific herring was the fourth most abundantly impinged fish and constituted 4.3 percent of all 

fishes impinged. They were impinged throughout the year with peak densities from June 

through August, with a second, lower peak in January and February. 

Thirteen species of surfperch were collected in impingement samples from the Units 1 through 5 

intake, and 12 species from the Units 6 and 7intake. Shiner perch discussed above was the most 

commonly collected species at both intakes. Other species included white seaperch, and barred, 

black, dwarf, kelp, pile, rainbow, rubberlip, silver, spotfin, striped, and walleye surfperches. 

Walleye surfperch were collected throughout the year, with peak numbers impinged in June and 

July. Most were impinged in the summer and were juveniles. White seaperch were impinged 

also throughout the year with peaks in abundance between May and July and were mainly 

juveniles. 

Rockfishes were represented in impingement collections by a total of 14 species. The most 

abundant were olive, blue, grass and brown rockfish and bocaccio. These five species accounted 

for 89 percent of all rockfishes impinged at Units 1 through 5 and 84 percent at Units 6 and 7. 

The percentage of bocaccio, the single most abundant rockfish impinged, at Units 1 through 5 

(59 percent) was nearly the same at Units 6 and 7 (53 percent). Bocaccio was impinged 

throughout the year, with the greatest abundance in May through September. 

On the basis of the lengths of impinged bocaccio, it was determined that virtually all were 

young-of-the-year. Figure 5-6 shows the mean length of bocaccio collected in impingement 

samples at the Moss Landing Power Plant for Units 1 through 5 and Units 6 and 7 intakes 

(PG&E, 1983). The data show that mean length ofthe bocaccio measured was less than 180 

mm, the maximum length of the young-of-the-year bocaccio (Starr et al., 1998). A part of the 

total number of bocaccio in the sample was measured. The number of bocaccio measured during 

each month is listed above each of the figure bars. Figure 5-7a and 5-7b show the number 

measured vs. total number of bocaccio collected in the impingement samples. 

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p5.0 Impingement Effects 

Olive/yellowtail rockfish constituted 14 percent of the rockfish collected from Units 1 through 5 

intake and 16 percent at Units 6 and 7. They were collected throughout the year with peak 

abundance in June and July. Blue rockfish comprised 6 percent of rockfish collected at Units 1 

through 5 and 4 percent at Units 6 and 7. The average length for the Units 1 through 5 was 70 

mm (2.8 in.) and 67 mm (2.6 in.) at Units 6 and 7. As with the olive/yellowtail virtually all blue 

rockfish impinged were juveniles. 

Impingement surveys were taken at the cooling water intakes for Units 1 through 5 and Units 6 

and 7 from January 1979 to March 1980. 

250 

Number of Measurements 

Shown Above Bars 

Units 1-5/Units6, 7 Maximum Length of 

Young-of-the-Year 

Bocaccio 180 mm 

18/60 9/11 

11/12 

.1/1. J 

Feb-79 Mar-79 Apr-79 May-79 Jun-79 Jul-79 Aug-79 Sep-79 Oct-79 Nov-79 Dec-79 Jan-80 Feb-80 Mar-80 

Figure 5-6. Mean length of bocaccio collected in impingement samples at the Moss Landing Power Plant 

for Units 1 through 5 and Units 6 and 7 intakes (PG&E, 1983). 

Figure 5-8 shows the mean monthly concentrations (#/l,000 m3) for the four most abundantly 

impinged fishes: northern anchovy, shiner perch, topsmelt, and Pacific herring. The mean 

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1000 

100 

o 

E 

Feb-79 Mar-79 Apr-79 May-79 Jun-79 Jul-79 Aug-79 Sep-79 Oct-79 Nov-79 Dec-79 Jan-80 Feb-80 Mar-80 

Figure 5-7a. Number measured vs. total number of bocaccio collected in impingement samples at the 

Moss Landing Power Plant Units 1 through 5 intakes (PG&E, 1983). 

10000 

1000 

1 100 

No Length Data 

for Mar-79 

D Total Number in Sample 

• Number Measured 

Feb-79 Mar-79 Apr-79 May-79 Jun-79 Jul-79 Aug-79 Sep-79 Oct-79 Nov-79 Dec-79 Jan-80 Feb-80 Mar-80 

Figure 5-7b. Number measured vs. total number of bocaccio collected in impingement samples at the 

Moss Landing Power Plant Units 6 and 7 intakes (PG&E, 1983). 

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5.0 Impingement Effects 

10 

o 

o 

o 

4fc 

¥

 5 

a> E 

a> 

E 4 

a 

E 

B Northern Anchovy Units 1-5 

• • -ShinerSurfperch Units 1-5 

•it - -Topsmelt Units 1-5 

• - -Pacific Herring Units 1-5 

- B — Northern Anchovy Units 6, 7 

0 Shiner Surfperch Units 6, 7 

-t_—Topsmelt Units 6, 7 

- 0 — Pacific Herring Units 6, 7 

*•** •m*+ 

Jan- Feb- Mar- Apr- May- Jun- Jul- Aug- Sep- Oct- Nov- Dec- Jan- Feb- Mar79 79 79 79 79 79 79 79 79 79 79 79 80 80 80 

Figure 5-8. Mean monthly concentrations of the most abundantly impinged fishes at the Moss Landing 

Power Plant Units 1 through 5 and Units 6 and 7 intakes (PG&E, 1983). 

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5.0 Impingement Effects 

monthly concentration was determined by calculating the mean concentration for all of the 

surveys taken during that month. The survey data illustrate that the highest impingement for the 

northern anchovy occurred during the late summer and fall. Impingement for shiner perch was 

high during the summer, whereas topsmelt experienced the highest impingement during the late 

fall. 

Figures 5-9a and 5-9b also show the mean monthly concentrations for the abundantly impinged 

fishes. However in these figures, the concentration for each of the four species is presented in 

one record per month. This provides an indication of the total impingement for all abundant 

fishes as well as the contribution to the total by each of the four species. These figures further 

illustrate that the highest concentration occurs during the summer and fall seasons. 

Figures 5-10a and 5-10b show the mean monthly concentrations for three selected cancer crabs; 

Cancer antennarius, Cancer anthonyi, and Cancer productus. These figures show that Cancer 

antennarius experiences the highest impingement. Cancer anthonyi had the next highest 

impingement levels throughout the survey period. 

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5.0 Impingement Effects 

E 

s 

a. 

E 

• Pacific Herring Units 1-5 

• Topsmelt Units 1-5 

• Shiner Surfperch Units 1 -5 

• Northern Anchovy Units 1-5 

Jan-79 Feb-79 Mar-79 Apr-79 May-79 Jun-7

t

9 Jul-7

l 

9 Aug-79 Sep-79 Oct-79 Nov-79 Dec-79 Jan-80 Feb-80 Mar-80 

Figure 5-9a. Mean monthly combined concentrations of the most abundantly impinged fishes at the 

Moss Landing Power Plant Units 1 through 5 intake (PG&E, 1983). 

• Northern Anchovy Units 6, 7 

• Shiner Surfperch Units 6, 7 

• Topsmelt Units 6, 7 

• Pacific Herring Units 6, 7 

,m, H.H, , , 

Jan-79 Feb-79 Mar-79 Apr-79 May-79 Jun-79 Jul-79 Aug-79 Sep-79 Oct-79 Nov-79 Dec-79 Jan-80 Feb-80 Mar-80 

Figure 5-9b. Mean monthly combined concentrations of the most abundantly impinged fishes at the 

Moss Landing Power Plant Units 6 and 7 intake (PG&E, 1983). 

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5.0 Impingement Effects 

0.20 

0.18 

0.16 

.£0.14 

I 0.12 

£ 0.10 

o E 

S> 0.08 

•i 0.06 

0.04 

0.00 

D Cancer antennarius Units 1-5 

• Cancer anthonyi Units 1-5 

- • Cancer productus Units 1-5 

—i 

•— 

_. 

1 l_ 

Jan-79 Feb-79 Mar-79 Apr-79 May-79 Jun-79 Jul-79 Aug-79 Sep-79 Oct-79 Nov-79 Dec-79 Jan-80 Feb-80 Mar-80 

Figure 5-10a. Mean monthly concentrations ofthe most abundantly impinged Cancer spp. crabs at the 

Moss Landing Power Plant Units 1 through 5 intake (PG&E, 1983). 

0.03 

0.02 

E 

1 0.02 

a. 

E 

0.01 -

0.00 

D Cancer antennarius Units 6, 7 

• Cancer anthonyi Units 6, 7 

• Cancer productus Units 6, 7 -

• JLr- u k 

Jan-79 Feb-79 Mar-79 Apr-79 May-79 Jun-79 Jul-79 Aug-79 Sep-79 Oct-79 Nov-79 Dec-79 Jan-80 Feb-80 Mar-80 

Figure 5-10b. Mean monthly concentrations ofthe most abundantly impinged Cancer spp. crabs at the 

Moss Landing Power Plant Units 6 and 7 intake (PG&E, 1983). 

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5.0 Impingement Effects 

Table 5-1 lists the estimated concentrations (#/l,000 m3) based on surveys taken from January 

1979 to March 1980. Impingement surveys were taken at the cooling water intakes for Units 1 

through 5 and Units 6 and 7. The data for the surveys was used to calculate an estimated 

concentration and estimated number impinged per day for selected species of fish and 

macroinvertebrates at each intake. 

Table 5-1. Estimated Concentrations based on Surveys taken from January 1, 1979 through 

March 31, 1980. 

Mean Volume/Day - Survey Dates (1,000 m3) 

Mean Volume/Day - Calendar Year (1.000 m3) 

Northern anchovy 

Shiner perch 

Topsmelt 

Pacific herring 

Pacific staghorn sculpin 

Bocaccio 

Rockfish: Taxon: black rockfish, chilipepper, 

copper rockfish, cowcod, darkblotched 

rockfish, dwarf rockfish, kelp rockfish, 

shortbelly rockfish, vermilion rockfish. 

Abundant Fish; Northem anchovy, shiner 

perch, topsmelt, and Pacific herring. 

Top Macroinvertebrates, Crabs; Cancer 

antennarius. Cancer anthonyi. Cancer gracilis, 

Cancer jordani, Cancer magister, Cancer 

oregonensis, Cancer productus. Cancer spp. 

Units 1 through 5 

1,330 

1,267 

Estimated 

Concentration 

(#/1,000 m3) 

0.7882 

0.3099 

0.1542 

0.1330 

0.0569 

0.0644 

0.0009 

1.3854 

0.1135 

Estimated 

Impinged/Day 

(#) 

1,049 

412 

205 

177 

76 

86 

1 

1,843 

151 

Units 6 and 7 

2,322 

2,335 

Estimated 

Concentration 

(#/l,000m3) 

0.7230 

0.2378 

0.1470 

0.1088 

0.0523 

0.0466 

0.0008 

1.2166 

0.1019 

Estimated 

Impinged/Day 

(#) 

1,678 

552 

341 

253 

121 

108 

2 

2824 

237 

Selected species of fish include abundant fish such as northern anchovy, shiner perch, topsmelt, 

and Pacific herring. The staghom sculpin and bocaccio were of interest and were also included 

in the impingement analysis. Selected rockfish were analyzed as a group including black 

rockfish, chilipepper, copper rockfish, cowcod, darkblotched rockfish, dwarf rockfish, kelp 

rockfish, shortbelly rockfish, and vermilion rockfish. Selected species of cancer crabs were 

analyzed including Cancer antennarius, Cancer anthonyi, Cancer gracilis, Cancer jordani, 

Cancer magister, Cancer oregonensis, Cancer productus, and Cancer spp. 

The estimated concentration was determined by first calculating the actual concentration for each 

survey. The estimated concentration was then calculated by taking the mean of the concentration 

for all of the surveys. The mean cooling water intake volume for all the survey dates was 

utilized to convert the estimated concentration to an estimated number impinged per day. The 

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5.0 Impingement Effects 

estimated number of each species impinged per day was calculated by taking the product of the 

estimated concentration and the mean volume for all of the surveys. 

The northern anchovy had the highest estimated concentration ofthe selected abundant fish for 

Units 1 through 5 and Units 6 and 7 (at 0.7882 and 0.7230 /1,000 m3 respectively). The topsmelt 

had the second highest estimated concentration at 0.3099/1,000 m3 for Units 1 through 5 and 

0.2378 /1,000 m3 for Units 6 and 7. Shiner perch had the third highest estimated concentration at 

0.1542 and 0.1470 /1,000 m3 for Units 1 through 5 and Units 6 and 7 respectively. Pacific 

herring had the fourth highest estimated concentration at 0.1330 and 0.1088 /1,000 m3. 

The remaining species of fish analyzed had relatively low concentrations. Staghorn sculpin had 

an estimated concentration at 0.0569 (#/l,000 m3) for Units 1 through 5 and 0.0523 /1,000 m3 for 

Units 6 and 7. Bocaccio had an estimated concentration at 0.0644 and 0.0466 /1,000 m3 

respectively for Units 1 through 5 and Units 6 and 7. The selected rockfish had an extremely 

low estimated concentration of 0.0009 /1,000 m3 and 0.0008 /1,000 m3) for Units 1 through 5 

and Unit 6 and 7. 

The data for the cancer crabs were evaluated as a group. The estimated concentration for the 

cancer crabs was 0.1135/1,000 m3 for Units 1 through 5 and 0.1019/1,000 m3 for Units 6 and 7. 

5.4 Rate of Impingement and Intake Velocities 

Intake velocities could affect the rate of impingement if there are large amounts of debris present 

in the water. This relationship between heavy debris loading on the screens and increased 

impingement was examined at the Morro Bay Power Plant (PG&E, 1982). 

Information was provided by Farm Pump Irrigation (FPI) on the expected approach velocities of 

a traveling screen designed to replace the existing screens at the Pittsburg Power Plant. 

Following discussions with FPI on various design aspects FPI provided estimates of throughscreen velocities for the replacement screen design at Pittsburg Units 1 through 4 and Units 5 and 

6 intakes for both high and low tide conditions (Table 5-2). The estimated replacement screen 

design velocities were compared to previously reported intake approach and through-screen 

design velocities for Pittsburg Units 1 through 4 and Units 5 and 6. Assuming that the PG&E 

reported approach and through-screen velocities were calculated for high tide conditions, the 

replacement ofthe existing traveling screens with FPI-type screens would reduce both existing 

approach and through-screen velocities at Units 1 through 4 and Units 5 and 6. 

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I 

Table 5-2. Existing and Projected Approach and Through-Screen Velocities for the Pittsburg 

Power Plants Units 1 through 4 and Units 5 and 6 Intakes. 

Approach Velocity (fps) 

Existing 

FPI 

Replacement 

Through-screen Velocity (fps) 1 

Existing FPI Replacement J 

Pittsburg Power Plant 1 

Units 1 through 4 ^J ^ 

Units5and 6

 | (0.24 mps) 

0.65-1.11 

(0.198-0.34 mps) 

0.60-1.05 

(0.183-0.32 mps) 

2.0 

(0.61 mps) 

1.5 

(0.46 mps) 

0.75 J 

(0.23 mps) 

0.69 1 

(0.21 mps) I 

The impacts of power plant intake velocities on fishes have been widely reviewed and published. 

The U.S. Fish and Wildlife Service has provided the general background and understanding to 

assess impacts of intake velocities on fisheries resources. Their publications conclude with a 

recommendation that maximum intake velocities should not exceed 0.5 fps. There are number of 

factors which go into estimating general guidance for approach velocities. However, conditions 

vary from site to site, with age class of fish and species of fish. The basis for the 0.5 fps 

recommendation has been investigated for a number of species and sizes in specific intake 

situations. The effect of screen approach velocity on percent impingement of larval andjuvenile 

striped bass in laboratory swimming trials for periods of 10 and 30 minute duration is shown in 

Table 5-3. 

Table S-3. Impingement of Striped Bass at Various Approach Velocities. 

Percent Stri 

Test time and size range 

19-38 mm length 

10- min 

90-140 mm 

jed Bass Impinged versus Approach Velocity 

0.8 

(0.24 

mps) 

0 

0.5 

(0.15 

mps) 

10-min | 0 

30-min j 0 

0.9 

(0.27 

mps) 

0 

0.75 

(0.23 

mps) 

0 

0 

Velocity (fps) 

1.0 

(0.30 

mps) 

20 

1.0 

(0.30 

mps) 

0 

2 

1.1 

(0.34 

mps) 

40 

1.5 

(0.46 

mps) 

0 

11 

1.2 

(0.37 

mps) 

60 

2.0 

(0.61 

mps) 

8 

32 

1.3 

(0.40 

mps) 

79 

2.5 

(0.76 

mps) 

29 

1.4 

(0.43 

mps) 

97 

Source: EA, 1982 

Intake velocity calculations, based on an inclined screen-type replacement for the Pittsburg 

Power Plant, indicate that during high tide the existing approach velocities would decrease. 

Units 1 through 4 approach velocities would decrease from 0.8 fps (0.24 mps) to 0.65 fps (0.20 

mps) and approach velocities would decrease from 0.8 fps (0.24 mps) to 0.60 fps (0.18 mps) at 

1 

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5.0 impingement Effects 

the Units 5 and 6 intake. Based on the information provided in Table 5-3, this reduction in 

intake velocity would have no measurable effect on the impingement of fishes similar to striped 

bass. The reduced velocities might benefit more fragile fish species. 

5.4.11mpingement Survival and Intake Velocities 

The reduction of intake and screen approach velocities will increase the potential of small fish 

surviving impingement. Replacement ofthe existing Units 1 through 5 traveling screens with 

lower velocity inclined-type screens would increase the potential for survival of impinged fishes, 

assuming that: 

1. fine mesh screen was used to remove small fishes, and 

2. the fishes were returned to the source water within a few minutes. 

The potential to reduce fish losses by reductions in traveling screen approach velocities is 

illustrated in Table 5-4. 

Table 5-4. Survival {%) of Striped Bass Impinged Four Minutes at Various Water Velocities. 

Survival (%) of Striped Bass Impinged Four Minutes at Various Water Velocities 

Size Class (mm) 

5.1-6.9 

7.0-8.9 

9.0-10.9 

11.0-12.9 

13.0-14.9 

15.0-16.0 

Weighted Mean 

Velocity (fps) 

0.5 

(0.15 mps) 

69% 

83% 

91 % 

96% 

89% 

100% 

83% 

1.0 

(0.30 mps) 

62% 

84% 

90% 

88% 

94% 

96% 

80% 

1.5 

(0.46 mps) 

19% 

71 % 

90% 

88% 

87% 

100% 

68% 

Source: Alden Research Laboratory and Stone and Webster Engineering Corporation (1980), as cited in Ecological 

Analysts, Inc., 1982. 

Note: Impingement survival was detennined 96 hours after impingement and has not been corrected for control 

survival. No tests were conducted using fish < 16 mm (0.63 in.) at an approach velocity of 0.5 fps (0.15 mps). 

Since the sizes offish that benefit most from reduced impingement velocities are fish smaller 

than the ones impinged by MLPP's existing 3/8 in. (0.953 cm) mesh screens, the effect of 

inclined-type screen replacement on impingement survival would be minimal, if any, and 

difficult to quantify. The above table shows an example of impingement survival represented by 

a relatively hardy species, striped bass. The impingement survival of larger sizes and adult 

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5.0 Impingement Effects 

forms of more fragile species offish, such as Pacific herring, would potentially increase with 

reduced intake screen approach velocities. 

Impingement survival studies (PG&E, 1983) were designed to provide a quantitative basis for 

estimating the survival of fishes and macroinvertebrates. Impingement survival was determined 

for the following three modes of traveling screen rotation operation: continuous, 1-hour 

intermittent, and 3-hour intermittent. The different rotation modes limited the amount of time 

impinged organisms were held on the screens. Organisms were collected and initial observations 

of alive or dead were recorded. Animals were placed into a flow-through holding system 

containing ambient water. They were observed periodically throughout the 96-hour holding 

period. Control experiments were conducted to determine the mortality associated with the 

sluiceway collection, handling, and the holding systems methods used. Fishes were mainly 

collected from otter trawls conducted in Moss Landing Harbor. These control fishes were held 

for 2 to 4 days before testing to allow them to recover from collection and handling stresses. 

Initial and long-term survival of northern anchovy, Pacific herring and silversides were 

characteristically low at both intakes. Increasing the frequency of screen rotation at Units 6 and 

7 improved the survival of surfperch but did not have much effect at Units 1 through 5. 

Although the survival of flatfish increased with increased screen rotation, the numbers of fishes 

available testing were low. Long-term survival of gobies and sculpin was high after the 3-hour 

rotation. Survival of crabs was high from Units 6 and 7, although the number tested was small; 

Units 1 through 5 crab survival was only 47 percent with 3-hour rotation, which increased to 70 

percent and 74 percent for the 1-hour and continuous rotation mode, respectively. It is important 

to note that these studies were done of organisms collected from the sluiceways of the intakes 

and were not perfonned on organisms returned to the Units 6 and 7 discharge. Impinged 

material from Units 1 through 5 was not routed out through the discharge in Elkhorn Slough, 

thus no impinged organisms survived. 

5.5 Conclusions 

The authors ofthe first 316(b) Demonstration (PG&E, 1983) used recent trends in the 

commercial fishery landing statistics for the Monterey Bay region to assess entrainment and 

impingement effects. For example, the trend in commercial landings of northem anchovy, the 

most abundantly impinged and entrained fish was showing a general increase during the 1970s. 

Northern anchovy also was the largest (in terms of biomass) fishery in California during the time 

of the 316(b) work. It was concluded that it was unlikely that the northern anchovy population 

could have supported such an increased commercial harvest trend if entrainment and 

impingement had precluded the maintenance of the existing population. Northern anchovy are a 

pelagic schooling species found from Baja California, north to Alaska. It was also noted that due 

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5.0 Impingement Effects 

to the broad distribution and high reproductive potential of northern anchovy, they appeared to 

be capable of sustaining the incremental mortality associated with a large commercially 

harvested species. 

Gobies are bottom-dwelling or burrow-inhabiting fishes found in the subtidal and intertidal areas 

in the vicinity of the MLPP. Several species of gobies have been collected in larval arid adult 

fish surveys of the area (Nybakken, Cailliet, and Broenkow, 1977). These species include: bay 

goby, arrow goby, blackeye goby, yellowfin goby, and longjaw mudsucker. There is no 

commercial fishery for gobies. Because no information existed on trends in abundance and 

distribution the authors used life history information to assess potential impacts. They reported, 

from the literature, that gobies have a moderately high reproductive potential, a high natural 

mortality rate, are widely distributed, and are not subjected to sport or commercial harvesting. It 

was also noted that extensive habitat exists in the vicinity ofthe plant and that because of their 

bottom-dwelling habits, very few reproductive adults were susceptible to impingement. 

Therefore, it can be predicted that the impingement losses for species considered were negligible 

for the MLPP operating at higher intake volumes than proposed for the modernization. No 

trends were found in the area's commercial and sport fisheries, including those near the plant, to 

indicate an adverse impact due to impingement losses at the power plant. Since impingement 

effects on area-wide fisheries were qualitatively undetectable, it was concluded that existing 

MLPP intake technology represented BTA to minimize impingement effects and potential 

impacts. 

In summary, modifications to the new combined-cycle intake will reduce impingement. The 

cooling water volume pumped through the new combined-cycle intake structure will be reduced 

from 381,000 gpm (1,441 m3/min) to 250,000 gpm (946 m3/min). As a result ofthe lower flows, 

approach velocities will decrease from 0.9 feet per second (fps; 0.27 meters per second [mps]) to 

0.5 fps (0.15 mps). The new traveling screens will be inclined at an approximate angle of 73° 

from horizontal, thus providing more surface screen area that will result in lower though screen 

velocities. These new angled screens will be more effective at removing debris than the 

conventional vertical traveling screens and will reduce the amount of debris in the area ofthe 

intake. The existing intake tunnel will be drastically reduced from approximately 350 ft 

(106.7 m) long to approximately 10 feet (3.1 m) behind the bar racks. The shortening of the 

tunnel may help to reduce impingement of schooling fishes that can become trapped in the tunnel 

and subsequently impinged. 

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6.0 COOLING WATER SYSTEM IMPACT ASSESSMENT 

The entrainment and impingement effects ofthe cooling water system for the proposed MLPP 

combined-cycle (CC) project have been assessed on the basis of both historical and on twelve 

months of recently completed survey information. The assessment considers both the effects of 

entraining larval fishes and megalopal cancer crabs and impinging larger fishes and invertebrates 

in the cooling water intake structure (CWIS). 

The three methods for assessing cooling water system (CWS) effects described in the MLPP 

Modernization Project Study Plan were the fecundity hindcasting {FH) and adult equivalent loss 

{AEL) approaches and empirical transport modeling {ETM). This report contains estimates of 

AEL and FH where data were available to parameterize these demographic approaches. It also 

provides estimates of proportional entrainment {PE) for inclusion in the ETM. The estimates of 

total entrainment mortality (PM) generated from the ETM represent 9 months ofthe data; it is 

unlikely that the remaining three months ofdata will significantly change results presented here. 

Results from the MLPP entrainment studies and previous impingement studies (PG&E, 1983) 

are used to predict the potential entrainment and impingement effects ofthe proposed combinedcycle CWS. Estimates of larval fish and megalopal cancer crab concentrations (#/m3

) sampled at 

the MLPP CWIS and multiplied by the projected combined-cycle daily intake volume (m3) 

provide estimates ofthe total number of larval fishes and megalopal cancer crabs that might be 

withdrawn by the power plant's CWS. Similarly, larval fish and megalopal cancer crab 

concentrations estimated from MLPP's source water bodies (Elkhom Slough, Moss Landing 

Harbor, and Monterey Bay) and multiplied by their daily tidal volumes produce estimates of 

local larval and megalopal abundance. By comparing the number of larvae and megalops 

withdrawn by the power plant to the number available (i.e., at risk to entrainment), an estimate 

of fractional loss {PE) can be generated for each taxon or species. The magnitude ofthese 

fractional losses can serve as a guide to determining unacceptable CWS effects that could cause 

population impacts in the form of long-term declines. The context required to interpret these 

fractional losses comes from fishery management practices and other forms of stock 

assessments. In the case of a harvested species, these fractional losses must be considered as 

additive to harvest losses when assessing impacts and any potential for population decline. 

In the following description and discussion of our preliminary findings, several consistent trends 

are apparent. These include low diversity of entrained species and relatively low magnitude 

proportional losses. In addition to the low diversity of entrained species and small proportional 

losses, the survey results show very little entrainment of important commercial or recreational 

species. 

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6.0 Cooling Water System Impact Assessment 

Historical information and present findings on MLPP CWS effects and projected effects ofthe 

new combined-cycle facility are reviewed and assessed for eight ofthe most abundant larval fish 

taxa and all megalopal cancer crabs. The eight fish taxa comprised over 95 percent by 

abundance ofthe larvae entrained. Following this assessment of MLPP CWS effects, a variety 

of alternative intake technologies to reduce these entrainment and impingement effects are 

reviewed in Section 7—Evaluation of Alternative Intake Technologies. Both the feasibility and 

cost ofthe various technologies are weighed against their effectiveness to reduce any identified 

CWS effects or potential impacts. The economic cost of reducing CWS impacts through 

implementing alternative technologies must not be wholly disproportionate to the benefit gained 

in terms of minimizing any adverse environmental impacts. 

6.1 Entrainment Effects Assessment 

For this report, we have focused our assessment of entrainment effects on the eight most 

abundant larval fish taxa and all cancer crab megalops. These selected species are carried 

forward in our analysis as target species because of their high relative abundance or 

commercial/recreational importance. The larval fish species or taxa groups chosen for this 

preliminary assessment are the most abundant found in our entrainment sampling to date. They 

are the unidentified gobies, bay goby, blackeye goby, Pacific staghorn sculpin, white croaker, 

blennies, longjaw mudsucker, and Pacific herring. Two species that occurred in relative low 

abundance, Pacific herring and white croaker, were included in the assessment because they 

represented the only fish species of commercial or recreational value for human consumption 

collected in our entrainment samples. However, as discussed in the following assessment ofthe 

two species, their low abundance makes it nearly impossible to quantitatively assess any MLPP 

entrainment effects or potential population-level impacts. The Cancer spp. megalops assessed 

are hairy rock crab, yellow rock crab, brown rock crab, dungeness crab, red rock crab, and 

slender rock crab. The yellow rock crab, brown rock crab, dungeness crab, and red rock crab all 

have some commercial importance. 

The assessment evaluates first the effects of MLPP CWS entrainment on larval forms of fishes 

and cancer crab megalops followed by a narrative assessment of impingement effects and the 

potential reduction ofthese effects by the modernization ofthe combined-cycle intake structure 

and flows. 

Source Water Volume 

The calculation of ETM, illustrated in Equations 9 to 14, requires estimates ofthe number of 

larvae and megalops entrained, the number of larvae and megalops in the source water 

population at risk to entrainment, and an estimate of larval age at entrainment. The number of 

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larvae and megalops entrained is estimated from representative samples of entrained organism 

concentrations multiplied by the total volume ofthe power plant's intake water. The number of 

source water larvae and megalops at risk is estimated by multiplying representative samples of 

their source water population concentrations by source water volumes. Larval ages are 

estimated from literature-based growth rates and reported lengths at the early life stages of 

hatching, yolk-sac stage completion, flexion, and transformation (Wang, 1986; Moser, 1996). 

Megalopal duration, megalopal survival, and age at maturation were estimated from the 

literature for cancer crabs. 

The MLPP source water area was divided into three sub-areas for the purposes of study and 

analysis. Information on MLPP area's marine geography, hydrography, and ecology was 

employed in analysis and discussion with the TWG to define a priori three sub-elements of 

source water population at risk to entrainment. The defined elements of source water population 

are Monterey Bay, Moss Landing Harbor, and Elkhom Slough. The shallow tidal channels and 

tributaries ofthe Elkhorn Slough, which flood and drain extensive Salicornia marsh, eelgrass 

beds, and mudflats, provide habitat for assemblages of invertebrates and fishes characteristically 

different from those found in the Moss Landing Harbor's habitats of deep channels surrounded 

by wharves and pilings. The enormous depths ofthe Monterey Canyon lie just beyond the 

harbor's entrance into the Monterey Bay. Less than a mile offshore canyon depths can exceed 

one mile. North and south ofthe harbor entrance, the steep, often rocky walls of this canyon rise, 

becoming the broad, shallow depths of sand beach and mud that characterize the majority ofthe 

bay's nearshore area from Santa Cruz to Monterey. The two distinctly different bottom substrata 

in combination with open-ocean beach and submarine canyon oceanographic conditions provide 

habitat for a third assemblage of invertebrates and fishes. 

The methods used to calculate the volumes ofeach ofthe three source water elements and their 

estimated source water volumes are given in Section 3.4.2.1. The geographical location and 

extent ofthe three source water sub-areas are illustrated in Figure 3-2. 

Source Water Sub-area Volume (m3) 

Monterey Bay 275,000,000 

Elkhom Slough 21,100,000 

Moss Landing Harbor 2,200,000 

Combined-Cycle Units 1,360,000 

(maximum volume) 

Empirical Transport Model {ETM) outputs are presented along with PE estimates for the June 

1999 through February 2000 source water surveys. Proportional entrainment {PE) values were 

calculated prior to ETM values. The two values differ by the method used to estimate the extent 

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of source water population at risk in time and space. For example, PE values calculated for the 

Monterey Bay source water element approximated its volume as that contained in an area 2 km 

south and north ofthe harbor entrance, extending from the shoreline out to a depth of 50 m. 

Given the presence of strong longshore currents and upwelling in this area, it was assumed that 

source water populations of larval and megalopal species in this element extend by current 

transport well beyond our first order approximation of source water extent and volume. 

However at this time, we have not employed current speed and larval duration to enlarge our 

initial estimate of Monterey source water volume. Our ETM calculations are based on our initial 

approximation of bay volume. As described in Section 3, the TWG requested that we calculate a 

second set of ETM values substituting the harbor and slough source water volume for the 

Monterey Bay source water volume. ETM values based on this order of magnitude volume 

difference are presented together with values computed using Monterey Bay's source water 

volume..In computing ETM values, PE's are also weighted by the monthly survey fraction (f~) of 

source water population at risk. This factor can significantly affect the outcome of combining a 

series of PE values. An ETM value could not be computed for dungeness crab due to a lack of 

co-occurrence of megalops in entrainment and source water samples. The majority of ETM 

values for the other crab species were based on a single PE value. 

Demographic Approaches for Estimating Entrainment Effects 

Entrainment losses were estimated from total larval and megalopal entrainment at MLPP using 

fecundity hindcast {FH) and adult equivalent loss {AEL) models. These models require speciesspecific estimates ofage, growth, fecundity, and survivorship. These data were available for 

four ofthe eight target fish taxa: bay goby, blackeye goby, combtooth blenny, and Pacific 

herring. For bay goby, no species-specific estimates of survival were available in the literature. 

Therefore, we were unable to estimate FH for this species, but were able to estimate AEL by 

substituting juvenile and adult survivorship data on three sympatric gobiids from Brothers 

(1975). For the other taxa, either species-specific fecundity or mortality rates were available to 

parameterize one or both ofthe demographic approaches for estimating entrainment effects. 

These taxa included white croaker, Pacific herring, hairy rock crab, yellow rock crab, brown 

rock crab, dungeness crab, red rock crab, and slender rock crab. AEL and FH loss estimates 

could not be computed for Pacific staghorn sculpin due to a lack of demographic information. 

The derivations ofthese approaches are detailed in Section 3 and the available life history data 

are summarized for each taxon in Section 4 of this document. 

6.2 Unidentified Gobies 

The unidentified goby category comprised the largest number and highest density of all 

entrained taxa. Evidence from our recent analysis of this taxon, discussed in Section 4, suggests 

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that there may be at least two species of gobies in this unidentified category. Because of their 

common abundance in habitat found in the Moss Landing area, arrow goby probably make up 

the majority ofthe larvae in this category. Previous investigators have presumed so in earlier 

studies ofthe Elkhom Slough and Moss Landing Harbor (Nybakken et al., 1977). A closer 

taxonomic examination of our samples has revealed that many unidentified gobiidae larvae are 

very similar meristically and morphometrically to the description of arrow goby larvae in Wang 

(1986) and Moser (1996). However, two prominent peaks in unidentified goby concentration 

(Figure 4-8), one in upper Elkhom Slough and another in the ocean at the far extreme of our 

study area, suggests the possibility of two different species in the unidentified goby category. 

This finding brings out a very important point in the application of impact assessment methods. 

Although we can analyze the proportional loss ofa grouped taxon such as unidentified gobies, as 

we have done in this section, it is not possible to assign the significance ofthese losses to a 

particular species' population. However, if we find that the entrainment losses ofan unidentified 

taxon are proportionally low compared to our estimates of source supplies, it provides a measure 

of assurance that the population ofthe unknown species we have collected will not be adversely 

affected by entrainment. Even though the samples may contain more than a single species, if the 

proportion of species in the unidentified category remains the same among entrainment and 

source water samples, our estimate of CWS effects and impacts is unaffected. We simply will 

not know to what species they apply. 

Empirical Transport Model (ETM) 

The proportional entrainment values for unidentified gobies are far below any value that could 

represent consequential intake effects or potential for long-term population declines. The range 

of PE values and standard errors are summarized in Table 6-la and b for the nine surveys from 

June 1999 through February 2000. The ETM value, based on the combined Monterey Bay 

source water volume is 0.03 and the ETM value substituting harbor/slough source water volume 

for bay volume is 0.11. 

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Table 6-la. Final ETM Output Unidentified Gobies Gobiidae spp. ETM calculations based on 

Monterey Bay volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss 

Landing Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.02638 

Std. Err. 

0.00423 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate. 

0.00624 

0.00131 

0.00444 

0.01133 

0.00048 

0.00481 

0.00478 

0.00325 

0.00504 

PE 

Std. Err. 

0.00131 

0.00058 

0.00116 

0.00485 

0.00036 

0.00051 

0.00113 

0.00046 

0.00024 

+2SE 

0.02638 

-2SE 

0.02638 

F; 

0.14475 

0.09099 

0.02686 

0.04359 

0.05047 

0.19441 

0.15840 

0.06911 

0.22143 

F, 

Std. Err. 

0.00278 

0.00065 

0.00012 . 

0.00020 

0.00046 

0.00094 

0.00097 

0.00138 

0.00161 

Larval 

Duration 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

Note: Data are preliminary. 

Table 6-lb. Final ETM Output for Unidentified Gobies Gobiidae spp. ETM calculations based on 

Monterey Bay volume = 21,100,000 m\ Elkhom Slough volume = 21,100,000 m3, Moss Landing 

Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.10690 

Std. Err. 

0.00668 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00978 

0.00448 

0.02455 

0.01329 

0.00132 

0.02961 

0.01799 

0.01719 

0.03156 

PE 

Std. Err. 

0.00221 

0.00109 

0.00486 

0.00596 

0.00093 

0.00307 

0.00431 

0.00221 

0.00195 

+2SE 

0.10690 

2SE 

0.10690 

F( 

0.14475 

0.09099 

0.02686 

0.04359 

0.05047 

0.19441 

0.15840 

0.06911 

0.22143 

Std. Err. 

0.00278 

0.00065 

0.00012 

0.00020 

0.00046 

0.00094 

0.00097 

0.00138 

0.00161 

Larval 

Duration 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

5.69 

Note: Data are preliminary. 

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Fecundity Hindcast Model (FH) 

The total annual larval entrainment for unidentified gobies was used to estimate the number of 

breeding females needed to produce the number of larvae entrained shown in Table 6-2. The 

estimated number of breeding females (FH) whose fecundity equals the estimated total loss of 

entrained larvae is calculated assuming an age at maturation of 1.0 year and an average lifespan 

of 2.5 years. The number of adult females hindcast from the larvae entrained at MLPP 

combined-cycle intake was 300,006 (90 percent C.L. = 97,113 to 926,792). 

Table 6-2. Annual Entrainment Estimates for Unidentified Gobies Gobiidae spp.: March 1, 1999 

through February 29, 2000. 

Annual 

Entrainment 

268,968,000 

Annual 

Std. Error 

3,206,740 

CV 

1% 

FH Estimates Unidentified Gobies Gobiidae spp. 

FH 

Estimate 

300,006 

FH 

Std. Error 

205,705 

Upper FH 

90% C.L. 

926,792 

Egg 

Survival 

1.0 

Yolk Sac 

Survival 

1.0 

Lower FH 

90% C.L. 

97,113 

Larval 

Survival 

0.683078 

1 

Eggs 

per Year 

1,750 

Average 

lifespan (yrs) 

2.5 

Age at 

Maturation 

1.0 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

Adult Equivalent Loss (AEL) 

No independent estimate of survival of unidentified gobies between age of entrainment and adult 

stage was available in the literature. 

The species of gobies that may comprise this taxon have neither commercial nor recreational 

fishery value, and there is little information on their ecological role in the community. There are 

no catch data that can be used to compare harvest mortality rates to entrainment mortality rates 

because ofthe absence of fishery data for this species. No estimates of stock size or density are 

available to convert entrainment mortality rates into an estimate of adult equivalent loss, 

assuming no compensatory mortality. 

Results of ETM analyses using the two different source water volumes show that the power plant 

may annually entrain approximately 3 percent (Table 6-la) or 11 percent (Table 6-lb) ofthe 

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6.0 Cooling Water System Impact Assessment 

unidentified Gobiidae taxon larvae from the MLPP source water. An independent estimate of 

FH yields a predicted theoretical loss of 97,113 to 926,792 adults (females only). 

6.3 Bay Goby 

The proportional entrainment values for the bay goby have remained quite low throughout the 

nine months of source water and entrainment studies as shown in Table 6-3. The range of values 

from a PE of zero to 0.03 (Table 6-3a) and zero to 0.17 (Table 6-3b) have remained at these low 

levels in spite of large fluctuations in the estimated number of entrained gobies. In 8 ofthe 9 

entrainment surveys that coincided with source water surveys, the numbers of bay goby 

increased in the late evening entrainment cycles after the daytime source water sampling (Figure 

4-10). 

Empirical Transport Model (ETM) 

The ETM values for bay goby found in Table 6-3 are far below values that would represent 

consequential intake effects or any potential for long-term population declines. The ETM value 

based on Monterey Bay source water volume is 0.04 and 0.21 when harbor/slough source water 

volume is substituted for Monterey Bay source water volume. The MLPP entrainment impact 

evaluation gives no indication of any potential impacts ofthe new combined-cycle project's 

CWS on the area's populations of bay goby. 

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Table 6-3a. Final ETM Output Bay Goby Lepidogobius lepidus. ETM calculations based on 

Monterey Bay volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m\ Moss 

Landing Harbor volume = 2,200,000 m\ 

ETM Estimate (PM) 

0.03862 

Std. Err0 

0.00878 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00181 

0.00214 

0.02912 

0.00126 

0.00595 

0.00945 

0.01792 

0.02671 

PE 

Std. Err. 

0.00000 

0.00048 

0.00298 

0.01805 

0.00054 

0.00114 

0.00640 

0.00720 

0.00873' 

+2SE 

0.03862 

2SE 

0.03862 

F, 

0.02279 

0.02787 

0.03156 

0.05694 

0.05964 

0.28503 

0.25217 

0.11026 

0.15374 

Std. Err. 

0.00087 

0.00053 

0.00015 

0.00032 

0.00040 

0.00126 

0.00152 

0.00250 

0.00245 

Larval 

Duration 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

Table 6-3b. Final ETM Output for Bay Goby Lepidogobius lepidus. ETM calculations based on 

Monterey Bay volume = 21,100,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing 

Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.21442 

Std. Err. 

0.04058 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.01654 

0.02055 

0.04901 

0.00589 

0.03972 

0.06821 

0.13367 

0.17434 

PE 

Std. Err. 

0.00000 

0.00441 

0.02575 

0.03268 

0.00207 

0.00683 

0.04845 

0.03869 

0.05308 

+2SE 

0.21442 

-2SE 

0.21442 

F, 

0.02279 

0.02787 

0.03156 

0.05694 

0.05964 

0.28503 

0.25217 

0.11026 

0.15374 

F, 

Std. Err. 

0.00087 

0.00053 

0.00015 

0.00032 

0.00040 

0.00126 

0.00152 

0.00250 

0.00245 

Larval 

Duration 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

3.29 

Note: Data are preliminary. 

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Fecundity Hindcast Model (FH) 

No independent estimate of survival of bay goby between age of entrainment and the egg stage 

was available in the literature. 

Adult Equivalent Loss (AEL) 

The total annual MLPP combined cycle entrainment of bay goby (March 1999 to March 2000) 

was used to estimate the number of equivalent adults theoretically lost to the population shown 

in Table 6-4. The estimated number of equivalent adults corresponding to the number of larvae 

that would have been entrained by the proposed MLPP combined-cycle intake was 1,045,588 

(90 percent C.L. = 520,290 to 2,101,241). 

Table 6-4. Annual Entrainment and AEL Estimates for Bay Goby Lepidigobius lepidus: 

March 1, 1999 through February 29, 2000. 

Annual 

Entrainment 

152,755,000 

Annual 

Std. Error 

643,860 

CV 

0% 

AEL Estimates for Bay Goby Lepidogobius lepidus 

AEL 

Estimate 

1,045,588 

AEL 

Std. Error 

443,627 

Survival 

Early Larvae 

0.012775 

Survival 

Late Larvae 

1.0 

-. "•'-"••."-.. ; ;"','..'"; - - t . •, '.-• ' .-.- - .•<':'.—.?•• -'"•' ' 

Upper 90% 

C.L. 

2,101,241 

Survival 

Early Juv. 

1.0 

Survival 

Juv. I 

1.0 

Survival 

Juv. II 

1.0 

Lower 90% 

C.L. 

520,290 

Survival 

Juv. Ill 

I.O 

Survival 

Juv. IV 

1.0 

Survival 

Pre-Recruit 

0.535797 

The uncertainty of our^£X estimate is most affected by the model parameters of early larval and 

early juvenile survivorship. Uncertainty in our entrainment estimates had relatively little effect 

on the confidence in the estimated AEL. 

The bay goby has neither commercial nor recreational fishery value and there is little 

information on their ecological role in the community. There are no catch data that can be used 

to compare harvest mortality rates to entrainment mortality rates because ofthe absence of 

fishery data for this species. No estimates of stock size or density are available to convert FH or 

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AEL entrainment effects into estimates of fractional loss, even assuming no compensatory 

mortality. 

Results of ETM analyses using the two different source water volumes show that the power plant 

may annually entrain approximately 4 percent (Table 6-3a) or 21 percent (Table 6-3b) ofthe bay 

goby larvae from the MLPP source water. An independent estimate of AEL yields a predicted 

theoretical loss of 520,290 to 2,101,241 adults (males and females combined). The ETM 

estimate is not large enough to be of any important consequence to the local population of adult 

bay goby. The large estimate of AEL losses reflects a number of uncertainties in model input for 

life history parameters of this species and large source water concentrations in the vicinity ofthe 

power plant intake. 

6.4 Blackeye Goby 

The proportional entrainment values for the blackeye goby have varied an order of magnitude 

throughout the nine months of source water and entrainment studies as shown in Table 6-5. 

Changes in PE values ranging from zero to 0.04 (Table 6-5a) and from zero to 0.05 (Table 6-5b) 

correspond to fluctuations in the estimated of number of entrained blackeye goby. On several 

occasions the numbers ofthe blackeye gobies increased in the late evening entrainment cycles 

following the daytime source water sampling. 

Empirical Transport Model (ETM) 

The ETM values for blackeye goby as shown in Figure 6-5 are far below values that would 

represent consequential intake effects or any potential for long-term population declines. The 

ETM value, based on the Monterey Bay source water volume is 0.04 and 0.07 based a 

substitution of harbor/slough volume for Monterey Bay volume. The MLPP entrainment impact 

evaluation gives no indication of any potential impacts ofthe new combined-cycle project's 

CWS on the area's blackeye goby. 

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Table 6-5a. Final ETM Output for Blackeye Goby Coryphopterus nicholsi. ETM calculations 

based on Monterey Bay volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m\ 

Moss Landing Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.04318 

Std. Err. 

0.03675 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.01042 

0.00403 

0.00000 

0.03964 

0.01304 

0.00000 

0.00000 

0.00000 

0.00868 

PE 

Std. Err. 

0.00183 

0.00293 

0.00000 

0.05493 

0.01682 

0.00000 

0.00000 

0.00000 

0.00834 

+2SE 

0.04318 

-2SE 

0.04318 

F; 

0.18997 

0.08754 

0.04002 

0.17607 

0.14578 • 

0.29972 

0.02504 

0.02382 

0.01203 

F, 

Std. Err. 

0.00493 

0.00252 

0.00112 

0.00179 

0.00186 

0.00306 

0.00051 

0.00694 

0.00132 

Larval 

Duration 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

Table 6-5b. Final ETM Output for Blackeye Goby Coryphopterus nicholsi. ETM calculations 

based on Monterey Bay volume = 21,100,000 m3, Elkhom Slough volume = 21,100,000 m3, 

Moss Landing Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.07488 

Std. Err. 

0.04756 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.01042 

0.03812 

0.00000 

0.03964 

0.04842 

0.00000 

0.00000 

0.00000 

0.05040 

PE 

Std. Err. 

0.00183 

0.02762 

0.00000 

0.05493 

0.06081 

0.00000 

0.00000 

0.00000 

0.04763 

+2SE 

0.07488 

-2SE 

0.07488 

Fi 

0.18997 

0.08754 

0.04002 

0.17607 

0.14578 

0.29972 

0.02504 

0.02382 

0.01203 

Fi 

Std. Err. 

0.00493 

0.00252 

0.00112 

0.00179 

0.00186 

0.00306 

0.00051 

0.00694 

0.00132 

Larval 

Duration 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

3.98 

Note: Data are preliminary. 

E9-053.9 6-12 MLPP 316(b) Resource Assessment 

4-28-2000 
6.0 Cooling Water System Impact Assessment 

Fecundity Hindcast Model (FH) 

The total annual larval entrainment for blackeye goby was used to estimate the number of 

breeding females needed to produce the number of larvae entrained shown in Table 6-6. The 

estimated number of breeding females (FH) whose fecundity equals the estimated total loss of 

entrained larvae is calculated assuming an age at maturation of 0.5 years and an average lifespan 

of 3.6 years. The number of adult females hindcast from the larvae entrained at MLPP 

combined-cycle intake was 1,825 (90 percent C.L. = 737 to 4,524). 

Table 6-6. Annual Entrainment and FH Estimates for Blackeye Goby Coryphopterus nicholsi: 

March 1, 1999 through Feb 29, 2000. 

Annual Entrainment 

16,795,300 

Annual Std. Error 

443,885 

CV 

3% 

Fecundity Hindcast (FH) Estimates for Blackeye Goby Coryphopterus nicholsi. 

FH 

Estimate 

1,825 

FH 

Std. Error 

1,007 

Upper FH 

90% C.L. 

4,524 

Egg Survival 

1.0 

Yolk-Sac 

Survival 

1.0 

Lower FH 

90% C.L. 

737 

Larval 

Survival 

0.736313 

Eggs 

per Year 

8,062 

Average 

Lifespan (yrs) 

3.6 

Age at 

Maturation 

0.5 

The uncertainty of our FT/estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

Adult Equivalent Loss (AEL) 

No independent estimate of survival of blackeye goby between age of entrainment adults was 

available in the literature. The methods used to estimate survival based on two goby species 

(cheekspot and shadow goby) are discussed in Section 4. 

The total annual MLPP combined-cycle entrainment of blackeye goby (March 1999 to March 

2000) was used to estimate the number of equivalent adults theoretically lost to the population 

shown in Table 6-7. The estimated number of equivalent adults corresponding to the number of 

larvae that would have been entrained by the proposed MLPP combined-cycle intake was 16,636 

(90 percent C. L. = 8,277 to 33,436). We cannot assume that AEL is related to FH by a factor of 

two since blackeye goby are protogynous hermaphrodites. 

E9-053.9. 6-13 MLPP 316(b) Resource Assessment 

4-28-2000 
6.0 Cooling Water System Impact Assessment 

Fecundity Hindcast Model (FH) 

The total annual larval entrainment for combtooth blenny was used to estimate the number of 

breeding females needed to produce the number of larvae entrained shown in Table 6-11. The 

estimated number of breeding females (FH) whose fecundity equals the estimated total loss of 

entrained larvae is calculated assuming an age at maturation of 2.0 years and an average lifespan 

of 7.0 years. The number of adult females hindcast from the larvae entrained at MLPP 

combined-cycle intake was 9,086 (90 percent C L. = 3,335 to 24,752). 

Table 6-11. Annual Entrainment and FH Estimates for Unidentified Blennies Hypsoblennius spp.: 

March 1, 1999 through February 29, 2000. 

Annual Entrainment 

16,701,400 

Annual Std. Error 

326,818 

CV 

2% 

FH Estimates for Unidentified Blennies Hypsoblennius spp. 

FH 

Estimate 

9,086 

FH 

Std. Error 

5,535 

Egg 

Survival 

1.0 

Upper FH 

90% C.L. 

24,752 

Yolk-Sac 

Survival 

1.0 

Lower FH 

90% C.L. 

3,335 

Larval 

Survival 

0.548721 

Eggs 

per Year 

1,340 

Average 

Lifespan (yrs) 

7.0 

Age at 

Maturation 

2.0 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

Adult Equivalent Loss (AEL) 

No independent estimate of survival of combtooth blenny between age of entrainment adults was 

available in the literature. The methods used to estimate survival are discussed in Section 4. 

The total annual MLPP combined cycle entrainment of combtooth blenny (March 1999 to March 

2000) was used to estimate the number of equivalent adults theoretically lost to the population as 

shown in Table 6-12. The estimated number of equivalent adults corresponding to the number of 

larvae that would have been entrained by the proposed MLPP combined-cycle intake was 10,247 

(90 percent C.L. = 5,099 to 20,593). The uncertainty of our AEL estimate is most affected by the 

model parameters of early larval and early juvenile survivorship. 

E9-053.9 6-20 MLPP 316(b) Resource Assessment 

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6.0 Cooling Water System Impact Assessment 

Table 6-12. Annual Entrainment and AEL Estimates for Unidentified Blennies Hypsoblennius 

spp.: March 1, 1999 through February 29, 2000. 

Annual 

Entrainment 

16,701,400 

Annual 

Std. Error 

85,044 

cv 

1% 

AEL Estimates for Unidentified Blennies Hypsoblennius spp. 

AEL 

Estimate 

10,247 

AEL 

Std. Error 

4,348 

Survival 

Early Larvae 

0.005708 

Survival 

Late Larvae 

I.O 

- • • .. • -•>;•.• - -.,.- • 

Upper 90% 

C.L. 

20,593 

Survival 

Early Juv. 

1.0 

.;. - ' •;.....- ., v 

Survival 

Juv. I 

1.0 

Survival 

Juv. II 

1.0 

Lower 90% 

C.L. 

5,099 

Survival 

Juv. Ill 

1.0 

Survival 

Juv. IV 

1.0 

Survival 

Pre-Recruit 

0.107493 

Uncertainty in our entrainment estimates had relatively little effect on the confidence ofthe 

estimated AEL. 

The species of combtooth blenny in our study area and entrainment samples has not been 

positively identified (Section 4.5). Ofthe three species that it could possibly be, none support 

either a commercial or recreational fishery value and there is little information on their 

ecological role in the community. Even if we were certain ofthe species identification, there are 

no catch data that can be used to compare harvest mortality rates to entrainment mortality rates 

because ofthe absence of fishery data for any ofthe three possible species. No estimates of 

stock size or density are available for any ofthe three species to convert entrainment mortality 

effects estimated as FH and AEL values into an estimate fractional population losses. 

Results of ETM analyses using the two different source water volumes show that the power plant 

may annually entrain approximately 11 percent (Table 6-10a) or 18 percent (Table 6-10b) ofthe 

combtooth blenny larvae from the MLPP source water. Fecundity hindcast estimates indicate 

that these values of FH may be equal to predicted losses ofthe reproductive output of about 

3,335 to 24,752 adult females. An independent estimate of AEL yields a predicted loss of 5,099 

to 20,593 adults (males and females combined). The significance ofthese losses to the local 

population of adult combtooth blenny is not known. The combtooth blenny, which is normally 

found further south, has recently invaded the harbor/slough area, possibly encouraged by El 

E9-053.9 6-21 MLPP 316(b) Resource Assessment 

4-28-2000 
P.30 

r 

6.0 Cooling Water System Impact Assessment 

Nino currents or temperatures. If these effects were vital to the population success, it would 

seem reasonable that they would not have been able to colonize and grow to their present 

abundance. 

6.7 Pacific Herring 

Pacific herring are one ofthe only two species collected in entrainment surveys of commercial or 

recreational food value. The other species is white croaker which were only recently collected in 

the paired entrainment-source water surveys. The estimated number of entrained Pacific herring 

larvae was nearly twice the estimated source water number of Pacific herring larvae when they 

occurred on the single paired source water and entrainment sampling survey analyzed in the 

previous report. The resulting PE value of 0.52 (Table 6-13a and b) based on only two 

specimens probably reflects a mismatch between the source water location of hatching Pacific 

herring roe and source water sampling locations or depths. Pacific herring were again collected 

in the February 2000 surveys. 

Empirical Transport Model (ETM) 

The ETM value shown in Table 6-13 for Pacific herring based on the Monterey Bay source water 

volume is 0.13 and 0.13 when the harbor/slough volume is used in place of Monterey Bay source 

water volume. 

E9-053.9 6-22 MLPP 316(b) Resource Assessment 

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6.0 Cooling Water System Impact Assessment 

Table 6-13a. Final ETM Output for Pacific Herring Clupea pallasi. ETM calculations based on 

Monterey Bay volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m3, 

Moss Landing Harbor volume = 2,200,000 m3. 

P.31 

ETM Estimate (PM) 

0.12932 

Std. Err. 

0.01608 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Stan 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.52349 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00190 

PE 

Std. Err. 

0.26787 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00088 

+2SE 

0.12932 

-2SE 

0.12932 

Fi 

0.12003 

0.05489 

0.00000 

0.02889 

0.00000 

0.04556 

0.04593 

0.02317 

0.68153 

Fi 

Std. Err. 

0.00700 

0.00141 

0.00000 

0.00074 

0.00000 

0.00117 

0.00841 

0.00604 

0.01129 

Larval 

Duration 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

Table 6-13b. Final ETM Output for Pacific Herring Clupea pallasi. ETM calculations based on 

Monterey Bay volume = 21,100,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing 

Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.13371 

Std. En. 

0.01677 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.52349 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00277 

PE 

Std. Err. 

0.26787 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00132 

+2SE 

0.13371 

-2SE 

0.13371 

Fi 

0.12003 

0.05489 

0.00000 

0.02889 

0.00000 

0.04556 

0.04593 

0.02317 

0.68153 

F, 

Std. Err. 

0.00700 

0.00141 

0.00000 

0.00074 

0.00000 

0.00117 

0.00841 

0.00604 

0.01129 

Larval 

Duration 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

7.55 

Note: Data are preliminary. 

E9-053.9 6-23 MLPP 316(b) Resource Assessment 

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6.0 Cooling Water System Impact Assessment 

Fecundity Hindcast Model (FH) 

The total annual larval entrainment for Pacific herring (March 1999 to March 2000) was used to 

estimate the number of breeding females needed to produce the number of larvae entrained 

shown in Table 6-14. The estimated number of breeding females (FH) whose fecundity equals 

the estimated total loss of entrained larvae is calculated assuming an age at maturation of 2.5 

years and an average lifespan of 11 years. The number of adult females hindcast from the larvae 

entrained at MLPP combined-cycle intake was 235 (90 percent C.L. = 80 to 692). 

Table 6-14. Annual Entrainment and FH Estimates for Pacific Herring Clupea pallasi: 

March 1, 1999 through February 29, 2000. 

Annual 

Entrainment 

4,436,280 

Annual 

Std. Error 

236,671 

CV 

5% 

FH Estimates for Pacific Herring Clupea pallasi 

FH 

Estimate 

235 

FH 

Std. Error 

154 

Upper FH 

692 

Egg 

Survival 

0.3 

Yolk Sac 

Survival 

1.0 

Lower FH 

80 

Larval 

Survival 

0.221000 

Eggs 

per Year 

67,000 

Average 

Lifespan (yrs) 

11.0 

Age at 

Maturation 

2.5 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

Adult Equivalent Loss (AEL) 

The methods used to estimate Pacific herring survival are discussed in Section 4. 

The total annual MLPP combined cycle entrainment of Pacific herring (March 1999 to 

March 2000) was used to estimate the number of equivalent adults theoretically lost to the 

population as shown in Table 6-15. The estimated number of equivalent adults corresponding to 

the number of larvae that would have been entrained by the proposed MLPP combined-cycle 

intake was 243 (90 percent C.L. = 121 to 488). The uncertainty of OUT AEL estimate is most 

affected by the model parameters of early larval and early juvenile survivorship. Uncertainty in 

our estimates of entrainment had relatively little effect on the uncertainty ofthe estimated AEL. 

E9-053.9 6-24 MLPP 316(b) Resource Assessment 

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6.0 Cooling Water System Impact Assessment 

Table 6-15. Annual Entrainment and AEL Estimates for Pacific Herring Clupea pallasi: 

March, 1, 1999 through February 29, 2000. 

Annual 

Entrainment 

4,436,280 

Annual 

Std. Enor 

88,934 

CV 

2% 

AEL Estimates for Pacific Herring Clupea pallasi 

AEL 

Estimate 

243 

..-. • •••. -.-. . .- . '•:••• • :? : '-iv -

AEL 

Std. Error 

103 

Survival 

Early Larvae 

0.000405 

Survival 

Late Larvae 

1.0 

Upper 90% 

C.L. 

488 

Survival 

Early Juv. 

1.0 

Lower 90% 

C.L. 

121 

Survival 

Juv. I 

1.0 

Survival 

Juv. II 

1.0 

Survival 

Juv. Ill 

1.0 

Survival 

Juv. IV 

1.0 

Survival 

Pre-Recruit 

0.135000 

Results of ETM analyses using the two different source water volumes show that the power plant 

may annually entrain approximately 13 percent (Table 6-13a and b) ofthe Pacific herring larvae 

from the MLPP source water. Fecundity hindcast estimates indicate that these values of FH may 

be equal to predicted losses ofthe reproductive output of about 80 to 692 adult females. An 

independent estimate of AEL yields a predicted loss of 121 to 488 adults (males and females 

combined). 

6.8 White Croaker 

White croaker larvae have been collected only recently in the nine pairs of entrainment and 

source water surveys. White croaker, as discussed in Section 4, are one of only two fish species 

that have been collected in entrainment surveys that have commercial or recreational human 

food value. The other species is Pacific herring as previously discussed. 

Empirical Transport Model (ETM) 

The ETM value shown in Table 6-16 for white croaker based on the Monterey Bay source water 

volume is 0.016 and 0.13 when the harbor/slough volume is used in place of Monterey Bay 

source water volume. Results ofthe ETM analyses using the two different source water volumes 

E9-053.9 6-25 MLPP 316(b) Resource Assessment 

4-28-2000 
6.0 Cooling Water System Impact Assessment 

show that the power plant may annually entrain approximately 2 percent (Table 6-16a) and 13 

percent (Table 6-16b) ofthe white croaker larvae from the MLPP source water. 

Table 6-16a. Final ETM Output for White Croaker Genyonemus lineatus. ETM calculations based 

on Monterey Bay volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m\ 

Moss Landing Harbor volume = 2,200,000 m3 

ETM Estimate (PM) 

0.01611 

Std. Err. 

0.01546 

+2SE 

0.01611 

-2SE 

0.01611 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00449 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00084 

F, 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00730 

0.55402 

0.02142 

0.41725 

F; 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00016 

0.01071 

0.00315 

0.01068 

Larval 

Duration 

8.75 

8.75 

8.75 

8.75 

8.75 

8.75 

8.75 

8.75 

8.75 

Table 6-16b. Final ETM Output White Croaker Genyonemus lineatus. ETM calculations based on 

Monterey Bay volume = 21,100,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing 

Harbor volume = 2,200,000 m3 

ETM Estimate (PM) 

0.12912 

Std. Err. 

0.02416 

+2SE 

0.12912 

-2SE 

0.12912 

Survey 

Date 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.04144 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00765 

Fi 

0.00000 

0.00000 

0.00000 

0.00000 

0.00730 

0.55402 

0.02142 

0.41725 

F, 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00016 

0.01071 

0.00315 

0.01068 

Larval 

Duration 

8.75 

8.75 

8.75 

8.75 

8.75 

8.75 

8.75 

8.75 

Note: Data are preliminary. 

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6.0 Cooling Water System Impact Assessment 

Fecundity Hindcast Model (FH) 

The total annual larval entrainment for white croaker (March 1999 to March 2000) was used to 

estimate the number of breeding females needed to produce the number of larvae entrained 

shown in Table 6-17. The estimated number of breeding females (FH) whose fecundity equals 

the estimated total loss of entrained larvae is calculated assuming an age at maturation of 2.0 

years and an average lifespan of 12 years. The number of adult females hindcast from the larvae 

entrained at MLPP combined-cycle intake was 107 (90 percent C.L. = 43 to 270). 

E9-053.9 6-27 MLPP 316(b) Resource Assessment 

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6.0 Cooling Water System Impact Assessment 

Table 6-17. Annual Entrainment and FH Estimates for White Croaker Genyonemus lineatus: 

March 1, 1999 through February 29, 2000. 

Annual 

Entrainment 

8,627,070 

Annual 

Std. Error 

404,930 

cv 

5% 

FH Estimates for White Croaker Genyonemus lineatus 

FH 

Estimate 

107 

FH 

Std. Error 

60 

Upper FH 

270 

Egg 

Survival 

1.0 

Yolk Sac 

Survival 

1.0 

Lower FH 

43 

Larval 

Survival 

0.153478 

Eggs 

per Year 

105,000 

Average 

Lifespan (yrs) 

12.0 

Age at 

Maturation 

2.0 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity and larval survivorship in that order. 

Adult Equivalent Loss (AEL) 

No independent estimate of survival of white croaker between age of entrainment and adult stage 

was available in the literature. 

6.9 Pacific Staghorn Sculpin 

The proportional entrainment values for Pacific staghom sculpin have varied only a few tenths 

ofa percent throughout the nine months of source water and entrainment studies as shown in 

Table 6-18. The range of values from a PE of zero to 0.009 in January and February 2000 

(Table 6-18a) and from zero to 0.09 (Table 6-18b), however did not correspond consistently to 

the estimated number of entrained Pacific staghom sculpin larvae. 

Empirical Transport Model (ETM) 

The ETM values for Pacific staghom sculpin as shown in Table 6-18 are far below values that 

would represent consequential intake effects or any potential for long-term population declines. 

The ETM value based on Monterey Bay source water volume is 0.04 and 0.12 when the 

harbor/slough source water volume is used instead of Monterey Bay source water volume. The 

MLPP entrainment impact evaluation gives no indication of any potential impacts ofthe new 

combined-cycle project's CWS on the area's Pacific staghom sculpin. 

E9-053.9 6-28 MLPP 316(b) Resource Assessment 

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6.0 Cooling Water System Impact Assessment 

Table 6-18a. Final ETM Output for Pacific Staghom Sculpin Leptocottus armatus. ETM 

calculations based on Monterey Bay volume = 275,000,000 m3, Elkhom Slough volume = 

21,100,000 m3, Moss Landing Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.03640 

Std. ErT. 

0.01982 

+2SE 

0.03640 

-2SE 

0.03640 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE ' 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00738 

0.00765 

0.00176 

0.00926 

0.00945 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00775 

0.00540 

0.00097 

0.00455 

0.00280 

Fj 

0.00128 

0.00000 

0.00000 

0.02418 

0.00930 

0.05360 

0.40993 

0.18391 

0.31779 

F: 

Std. Err. 

0.00052 

0.00000 

0.00000 

0.00053 

0.00155 

0.00198 

0.00986 

0.01118 

0.01150 

Larval 

Duration 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

Table 6-18b. Final ETM Output for Pacific Staghom Sculpin Leptocottus armatus. ETM 

Calculations based on Monterey Bay volume = 21,100,000 m3, Elkhom Slough volume = 

21,100,000 m3, Moss Landing Harbor volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.11789 

Std. Err. 

0.02993 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.08797 

0.09091 

0.00490 

0.02791 

0.02512 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.09206 

0.06256 

0.00298 

0.01263 

0.00867 

+2SE 

0.11789 

-2SE 

0.11789 

F, 

0.00128 

0.00000 

0.00000 

0.02418 

0.00930 

0.05360 

0.40993 

0.18391 

0.31779 

Std. Err. 

0.00052 

0.00000 

0.00000 

0.00053 

0.00155 

0.00198 

0.00986 

0.01118 

0.01150 

Larval 

Duration 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

6.30 

Note: Data are preliminary. 

E9-053.9 6-29 MLPP 316(b) Resource Assessment 

4-28-2000 
6.0 Cooling Water System Impact Assessment 

Fecundity Hindcast Model (FH) 

No independent estimate of survival of Pacific staghom sculpin between egg to entrainment age 

was available in the literature. 

Adult Equivalent Loss (AEL) 

No independent estimate of survival of Pacific staghom sculpin between age of entrainment and 

the adult stage was available in the literature. 

The Pacific staghom sculpin sustains a minor commercial bait fishery in the Monterey area. The 

species has no recreational fishery value. Little information exists on their ecological role. No 

estimates of stock size or density are available to convert entrainment effects estimated as FH 

and AEL losses into estimates of fractional loss to adult populations. 

Results of ETM analyses using the two different source water volumes show that the power plant 

may annually entrain approximately 4 percent (Table 6-18a) and 12 percent (Table 6-18b) ofthe 

Pacific staghom sculpin larvae from the MLPP source water. 

6.10 Hairy Rock Crab 

The proportional entrainment values for hairy rock crab Cancer jordani have varied only a few 

tenths ofa percent throughout the nine months of source water and entrainment studies as shown 

in Table 6-19. The PE values ranged from, zero to 0.00097 in September 1999 (Table 6 -19a) 

and from zero to 0.01 (Table 6-19b). Based on computed F; values also shown in Table 6-19, the 

largest fractions of hairy rock crab megalops at risk occurred in September and October. 

Empirical Transport Model (ETM) 

The ETM values for hairy rock crab as shown in Table 6-19 are far below values that would 

represent consequential intake effects or any potential for long-term population declines. The 

ETM value based on Monterey Bay source water volume is 0.018 and 0.177 when the 

harbor/slough source water volume is used instead of Monterey Bay source water volume. The 

MLPP entrainment impact evaluation gives no indication of any potential impacts ofthe new 

combined-cycle project's CWS on the area's hairy rock crab. 

E9-053.9 6-30 MLPP 316(b) Resource Assessment 

4-28-2000 
P.39 

6.0 Cooling Water System Impact Assessment 

Table 6-19a. Final ETM Output Hairy Rock Crab. ETM calculations based on Monterey Bay 

volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor 

volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.01842 

Std. En-. 

0.06389 

+2SE 

0.14621 

-2SE 

-0.10936 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00097 

0.00000 

0.00046 

0.00000 

0.00000 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00098 

0.00000 

0.00047 

0.00000 

0.00000 

Fi 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

F; 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

Table 6-19b. Final ETM Output for Hairy Rock Crab. ETM calculations based on Monterey Bay 

volume = 21,100,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor volume 

= 2,200,000 m3. 

ETM Estimate (PM) 

0.16722 

Std. Err. 

0.13037 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 . 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.01052 

0.00000 

0.00600 

0.00000 

0.00000 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.01057 

0.00000 

0.00613 

0.00000 

0.00000 

+2SE 

0.42797 

-2SE 

-0.09352 

F, 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

F, 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

Note: Data are preliminary. 

E9-053.9 6-31 MLPP 316(b) Resource Assessment 

4-28-2000 
3

.40 

6.0 Cooling Water System Impact Assessment 

Fecundity Hindcasting 

The total annual larval entrainment for hairy rock crab was used to estimate the number of 

breeding females needed to produce the number of megalops entrained shown in Table 6-20. The 

estimated number of breeding females (FH) whose fecundity equals the estimated total loss of 

entrained megalops is calculated assuming an age at maturation of 1.5 years and an average 

lifespan of 4.8 years. The number of adult females hindcast from the megalops entrained at 

MLPP combined-cycle intake was 1,039 (90 percent C.L. = 361 to 2,987). 

Table 6-20. Annual Entrainment and FH Estimates for Hairy Rock Crab: March 1, 1999 through 

February 29, 2000. 

Annual 

Entrainment 

1,740,210 

Annual 

Std. Error 

275,839 

cv 

16% 

FH Estimates Hairy Rock Crab. 

FH 

Estimate 

1,039 

FH 

Std. Error 

667 

Egg 

Survival 

1.0 

Megalopal 

Survival 

0.000657 

Eggs 

per Year 

1,530,907 

Average 

Lifespan (yrs) 

4.8 

Age at 

Maturation 

1.5 

Upper FH 

90% C.L. 

2,987 

Lower FH 

90% C.L. 

361 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

6.11 Yellow Rock Crab 

Proportional entrainment values for yellow rock crab Cancer anthonyi could not be calculated 

because they were not collected in the paired source water survey and entrainment surveys. 

Based on computed Fj values listed in Table 6-21, the yellow rock crab megalops were most at 

risk to entrainment in October, more than twice the exposure of any other month. 

Empirical Transport Model (ETM) 

The lack of co-occurrence of entrainment and source water samples containing yellow crab 

megalops precludes the calculation of an ETM value. The MLPP entrainment impact evaluation 

E9-053.9 6-32 MLPP 316(b) Resource Assessment 

4-28-2000 
P.41 

6.0 Cooling Water System Impact Assessment 

gives no indication of any potential impacts ofthe new combined-cycle project's CWS on the 

area's yellow rock crab. 

Table 6-21a. Final ETM Output Yellow Rock Crab. ETM calculations based on Monterey Bay 

volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor 

volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.00000 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

Std. Err. 

0.06263 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

+2SE 

0.12526 

-2SE 

-0.12526 

Fi 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

Fi 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

Table 6-21 b. Final ETM Output for Yellow Rock Crab. ETM calculations based on Monterey 

Bay volume = 21,100,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor 

volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.00000 

Std. Err. 

0.06263 

+2SE 

0.12526 

-2SE 

-0.12526 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

Fi 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

Fi 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

45.00 

Note: Data are preliminary. 

E9-053.9 6-33 MLPP 316(b) Resource Assessment 

4-28-2000 
P.42 

r 

6.0 Cooling Water System Impact Assessment 

Fecundity Hindcasting 

The total annual larval entrainment for yellow rock crab was used to estimate the number of 

breeding females needed to produce the number of megalops entrained shown in Table 6-22. 

The estimated number of breeding females (FH) whose fecundity equals the estimated total loss 

of entrained megalops is calculated assuming an age at maturation of 1.5 years and an average 

lifespan of 4.8 years. The number pf adult females hindcast from the megalops entrained at 

MLPP combined-cycle intake was 131 (90 percent C.L. = 46 to 374). 

Table 6-22. Annual Entrainment and FH Estimates for Yellow Rock Crab: March 1, 1999 through 

February 29, 2000. 

Annual 

Entrainment 

462,446 

Annual 

Std. Error 

68,006 

cv 

15% 

FH Estimates. 

FH 

Estimate 

131 

FH 

Std. Error 

84 

Egg 

Survival 

1.0 

Megalopal 

Survival 

0.000817 

Eggs 

per Year 

2,600,000 

Average 

Lifespan (yrs) 

4.8 

Age at 

Maturation 

1.5 

Upper FH 

90% C.L: 

374 

Lower FH 

90% C.L. 

46 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

6.12 Brown Rock Crab 

Proportional entrainment values for brown rock crab Cancer antennarius could not be calculated 

because they were not collected in the paired source water and daytime entrainment surveys. 

Based on computed Fi values listed in Table 6-23, brown rock crab megalops were most at risk 

to entrainment in October. 

Empirical Transport Model (ETM) 

The lack of co-occurrence of entrainment and source samples containing brown rock crab 

megalops precludes the calculation ofan ETM value. The MLPP entrainment impact evaluation 

E9-053.9 6-34 MLPP 316(b) Resource Assessment 

4-28-2000 
P.43 

6.0 Cooling Water System Impact Assessment 

gives no indication of any potential impacts ofthe new combined-cycle project's CWS on the 

area's brown rock crab. 

Table 6-23a. Final ETM Output for Brown Rock Crab. ETM calculations based on Monterey Bay 

volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m\ Moss Landing Harbor 

volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.00000 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

Std. Err. 

0.06263 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

+2SE 

0.12526 

-2SE 

-0.12526 

F; 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

Fi 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

Table 6-23b. Final ETM Output for Brown Rock Crab. ETM calculations based on Monterey Bay 

volume = 21,100,000 m3, Elkhorn Slough volume = 21,100,000 m3, Moss Landing Harbor volume 

= 2,200,000 m3. 

ETM Estimate (PM) 

0.00000 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

Std. Err. 

0.06263 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

+2SE 

0.12526 

-2SE 

-0.12526 

F; 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

Fi 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

43.30 

Note: Data are preliminary. 

E9-053.9 6-35 MLPP 316(b) Resource Assessment 

4-28-2000 
6.0 Cooling Water System Impact Assessment 

Fecundity Hindcasting 

The total annual larval entrainment for brown rock crab was used to estimate the number of 

breeding females needed to produce the number of megalops entrained shown in Table 6-24. 

The estimated number of breeding females (FH) whose fecundity equals the estimated total loss 

of entrained megalops is calculated assuming an age at maturation of 1.5 years and an average 

lifespan of 5.5 years. The number of adult females hindcast from the megalops entrained at 

MLPP combined-cycle intake was 209 (90 percent C.L. = 71 to 612). 

Table 6-24. Annual Entrainment and FH Estimates for Brown Rock Crab: March 1, 1999 through 

February 29, 2000. 

Annual 

Entrainment 

784,554 

Annual 

Std. Error 

198,934 

cv 

25% 

FH Estimates. 

FH 

Estimate 

209 

FH 

Std. Error 

137 

Egg 

Survival 

1.0 

Megalopal 

Survival 

0.001069 

Eggs 

per Year 

1,756,450 

Average 

Lifespan (yrs) 

5.5 

Age at 

Maturation 

1.5 

' - • > • . •-•-*'•-. . ' : ' • ' 

Upper FH 

90% C.L. 

612 

Lower FH 

90% C.L. 

71 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

6.13 Dungeness Crab 

ETM calculations were not done for dungeness crab Cancer magister. There were no dungeness 

crab megalops collected in the source water surveys from June 1999 through February 2000. 

They were collected in entrainment samples from the new combined-cycle units intake before 

the source water survey began. We may collect dungeness crab megalops in the March and 

April 2000 surveys. 

E9-053.9 6-36 MLPP 316(b) Resource Assessment 

4-28-2000 
P.45 

6.0 Cooling Water System Impact Assessment 

Fecundity Hindcasting 

The total annual larval entrainment for dungeness crab was used to estimate the number of 

breeding females needed to produce the number of megalops entrained shown in Table 6-25. 

The estimated number of breeding females (FH) whose fecundity equals the estimated total loss 

of entrained megalops is calculated assuming an age at maturation of 2.0 years and an average 

lifespan of 6.0 years. The number of adult females hindcast from the megalops entrained at 

MLPP combined-cycle intake was 167 (90 percent C.L. = 56 to 496). 

Table 6-25. Annual Entrainment and FH Estimates for Dungeness Crab: March 1, 1999 through 

February 29, 2000. 

Annual 

Entrainment 

335,180 

Annual 

Std. Error 

59,594 

cv 

18% 

FH Estimates. 

FH 

Estimate 

167 

FH 

Std. Error 

110 

Egg 

Survival 

1.0 

Megalopal 

Survival 

0.000802 

Eggs 

per Year 

1,250,000 

Average 

Lifespan (yrs) 

6.0 

Age at 

Maturation 

2.0 

Upper FH 

90% C.L. 

496 

Lower FH 

90% C.L. 

56 

6.14 Red Rock Crab 

The proportional entrainment value of 0.95 (Table 6-26a and b) for red rock crab Cancer 

productus was computed from the single occasion when its megalops were collected in both 

entrainment and source water samples. The computed F; values listed in Table 6-26 indicate that 

red rock crab are at risk of entrainment from August to February, with peak exposure in October. 

Empirical Transport Model (ETM) 

The ETM values for red rock crab as shown in Table 6-26 are far below values that would 

represent consequential intake effects or any potential for long-term population declines. The 

ETM value based on Monterey Bay source water volume is 0.04 and also 0.04 when the 

harbor/slough source water volume is used instead of Monterey Bay source water volume. The 

MLPP entrainment impact evaluation gives no indication of any potential impacts ofthe new 

combined-cycle project's CWS on the area's red rock crab. 

E9-053.9 6-37 MLPP 316(b) Resource Assessment 

4-28-2000 
6.0 Cooling Water System Impact Assessment 

P.46 

Table 6-26a-. Final ETM Output for Red Rock Crab. ETM calculations based on Monterey Bay 

volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor 

volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.04414 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

Std. Err. 

0.06144 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.95023 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

1.34383 

+2SE 

0.16702 

-2SE 

-0.07875 

F, 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

F, 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

Table 6-26b. Final ETM Output for Red Rock Crab. ETM calculations based on Monterey Bay 

volume = 21,100,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor volume 

= 2,200,000 m3. 

ETM Estimate (PM) 

0.04414 

Std. Err. 

0.06144 

+2SE 

0.16702 

-2SE 

-0.07875 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.95023 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

1.34383 

Fi 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0^13819 

0.07976 

0.16548 

0.04414 

F, 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

97.00 

Note: Data are preliminary. 

E9-053.9 6-38 MLPP 316(b) Resource Assessment 

4-28-2000 
P.47 

6.0 Cooling Water System Impact Assessment 

Fecundity Hindcasting 

The total annual megalopal entrainment for red rock crab was used to estimate the number of 

breeding females needed to produce the number of megalops entrained shown in Table 6-27. The 

estimated number of breeding females (FH) whose fecundity equals the estimated total loss of 

entrained megalops is calculated assuming an age at maturation of 1.5 years and an average 

lifespan of 4.8 years. The number of adult females hindcast from the megalops entrained at 

MLPP combined-cycle intake was 60 (90 percent C.L. = 20 to 181). 

Table 6-27. Annual Entrainment and FH Estimates for Red Rock Crab: March 1, 1999 through 

Febmary 29, 2000. 

Annual 

Entrainment 

246,363 

Annual 

Std. Error 

64,237 

cv 

26% 

FH Estimates. 

FH 

Estimate 

60 

FH 

Std. Error 

40 

Egg 

Survival 

1.0 

Megalopal 

Survival 

0.001658 

Eggs 

per Year 

1,492,500 

Average 

Lifespan (yrs) 

4.8 ' 

Age at 

Maturation 

1.5 

Upper FH 

90% C.L. 

181 

Lower FH 

90% C.L. 

20 

6.15 Slender Rock Crab 

The proportional entrainment values for slender rock crab Cancer gracilis is from a single 

survey in December, when they were collected in both entrainment and source samples. The PE 

values of 0.009 (Table 6-28a) and 0.11 (Table 6-28 b) were used to calculate the ETM values in 

Table 6-28. However, a single estimated proportional entrainment value does provide a robust 

ETM estimate. 

Empirical Transport Model (ETM) 

The ETM values for slender rock crab as shown in Table 6-28 are far below values that would 

represent consequential intake effects or any potential for long-term population declines. The 

ETM value based on Monterey Bay source water volume is 0.03 and 0.08 when the 

harbor/slough source water volume is used instead of Monterey Bay source water volume. The 

MLPP entrainment impact evaluation gives no indication of any potential impacts ofthe new 

combined-cycle project's CWS on the area's slender rock crab. 

E9-053.9 6-39 MLPP 316(b) Resource Assessment 

4-28-2000 
6.0 Cooling Water System Impact Assessment 

Table 6-28a. Final ETM Output Slender Rock Crab. ETM calculations based on Monterey Bay 

volume = 275,000,000 m3, Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor 

volume = 2,200,000 m3. 

P.48 

ETM Estimate (PM) 

0.02531 

Survey 

Date 

17Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

Std. Err. 

0.06662 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00914 

0.00000 

0.00000 

PE . 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.01132 

0.00000 

0.00000 

+2SE 

0.15855 

•2SE 

-0.10792 

F, 

0.00000 

0.00000 . 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

F, 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

Table 6-28b. Final ETM Output for Slender Rock Crab. ETM calculations based on Monterey 

Bay volume = 21,100,000 m\ Elkhom Slough volume = 21,100,000 m3, Moss Landing Harbor 

volume = 2,200,000 m3. 

ETM Estimate (PM) 

0.07903 

Std. Err. 

0.06044 

Survey 

Date 

17 Jun 1999 

12 Jul 1999 

12 Aug 1999 

16 Sep 1999 

14 Oct 1999 

18 Nov 1999 

29 Dec 1999 

20 Jan 2000 

24 Feb 2000 

PE Period 

Start 

18 May 1999 

18 Jun 1999 

13 Jul 1999 

13 Aug 1999 

17 Sep 1999 

15 Oct 1999 

19 Nov 1999 

30 Dec 1999 

21 Jan 2000 

PE 

Estimate 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.10672 

0.00000 

0.00000 

PE 

Std. Err. 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.00000 

0.12820 

0.00000 

0.00000 

+2SE 

0.19990 

-2SE 

-0.04184 

^ 

0.00000 

0.00000 

0.01544 

0.16551 

0.39149 

0.13819 

0.07976 

0.16548 

0.04414 

F( 

Std. Err. 

0.00000 

0.00000 

0.00549 

0.03712 

0.03525 

0.01741 

0.01700 

0.02310 

0.01213 

Larval 

Duration 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

41.60 

Note: Data are preliminary. 

E9-053.9 6-40 MLPP 316(b) Resource Assessment 

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P.49 

6.0 Cooling Water System Impact Assessment 

Fecundity Hindcasting 

The total annual larval entrainment for slender rock crab was used to estimate the number of 

breeding females needed to produce the number of larvae entrained shown in Table 6-29. The 

estimated number of breeding females (FH) whose fecundity equals the estimated total loss of 

entrained megalops is calculated assuming an age at maturation of 1.0 year and an average 

lifespan of 3.0 years. The number of adult females hindcast from the megalops entrained at 

MLPP combined-cycle intake was 239 (90 percent C.L. = 77 to 740). 

Table 6-29 Annual Entrainment and FH Estimates for Slender Rock Crab: March 1, 1999 through 

February 29, 2000. 

Annual 

Entrainment 

185,757 

Annual 

Std. Error 

47,909 

cv 

26% 

/"//Estimates Slender Rock Crab. 

FH 

Estimate 

239 

FH 

Std. Error 

164 

Egg 

Survival 

1.0 

Megalopal 

Survival 

0.001398 

Eggs 

per Year 

555,583 

Average 

Lifespan (yrs) 

3.0 

Age at 

Maturation 

1.0 

Upper FH 

90% C.L. 

740 

Lower FH 

90% C.L. 

77 

The uncertainty of our FH estimate was attributed by sensitivity analysis to the uncertainty ofthe 

model parameters of average lifespan, fecundity, and larval survivorship, in that order. 

6.16 Summary of Entrainment Effects 

The concentrations offish and crab larvae collected at the new combined-cycle intake were used 

to estimate entrainment losses by extrapolating to both a representative numbers of adults and by 

the fractional larval entrainment loss to the adult population. Three independent models, 

fecundity hindcast (FH), adult equivalent loss (AEL) and empirical transport model (ETM), were 

employed in calculating entrainment losses. Results from the three models are summarized 

where applicable by species of fishes and crabs in Table 6-30a and b, respectively. Estimated 

losses of adult bay goby and combtooth blennies, the highest losses identified in our assessment 

of entrainment effects, indicate a potential for local population level impacts. However these 

estimated theoretical losses are based on AEL and FH modeling results using generalized larval 

mortality information that may or may not accurately represent the specific species' larval 

E9-053.9 6-41 MLPP 316(b) Resource Assessment 

4-28-2000 
P.50 

6.0 Cooling Water System Impact Assessment 

survival rates. In the case ofthe blenny, we are uncertain which of possibly three combtooth 

blenny species we have collected. Our study's modeling results, as summarized in Table 6-30, 

generally demonstrate both low levels of entrainment effects and in theory commensurately low 

potentials for adverse population level impacts. 

Information about the size ofthe species' adult fish populations is required to convert the FH, 

AEL, and ETM estimates into comparable units of fishes depends on data describing. However, 

the majority of taxa found in our study are not commercially or recreationally harvested. The 

absence of a population assessment or any fishery data for this species we could not provide any 

context for the estimates. For example, egg and larval mortality data for blackeye goby allowed 

the application of multiple assessment approaches, but because the species is not harvested or 

monitored at the population level the losses cannot be compared to any standing stock of 

blackeye goby. 

For those species with both FH and AEL estimated losses, the model results can be compared 

directly using the relationship AEL = 2FH. This conversion requires that ages of AEL and FH 

individuals are equal in a 50:50 sex ratio. Results for abundant taxa that were in close agreement 

with the relationship 2FH = AEL provide some assurance that the parameters used in the models 

were representative for the study area populations. They also increase confidence that the 

assessments of effects on these populations are reasonably accurate. Two examples were white 

croaker and the Pacific herring. 

For the abundant taxa without available life history information, length measurements of larvae 

from the entrainment samples provided some insight into their larval life history and ecology. 

The length ranges for most ofthe entrained abundant larval fish taxa indicate that their exposure 

to entrainment occurs over a relatively short time period during their development. Average 

lengths were small demonstrating that they were exposed to entrainment for a brief period during 

their larval development. The lack ofthese later developmental stages indicates larval behavior 

that removes them from risk of entrainment as they develop (e.g., settlement to benthic habitats 

or migration into deeper areas away from the intake). 

Abundant larval taxa that are not commercially or recreationally harvested are primarily small 

bay and slough fishes. As might be expected due to the shallow water, shoreline intake location, 

several ofthese taxa are entrained in relatively high numbers, resulting in large AEL and FH 

estimates (Table 6-30). For example, losses of approximately 300, 000 unidentified gobies and 

1,450,000 bay goby were estimated using the FH and AEL models, respectively. However ETM 

values for the two species were relatively small (unidentified gobies = 0.026 [Table 6-la] and 

0.214 [Table 6-lb] and bay goby = 0.039 [Table 6-3a] and 0.106 [Table 6-3b]). 

E9-053.9 6-42 MLPP 316(b) Resource Assessment 

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6.0 Cooling Water System Impact Assessment 

Results from the present study indicate effects on commercially and redreationally harvested 

species with pelagic distributions such as Pacific herring and white croaker are minimal. For 

cases where we were able to apply all three assessment approaches, the effects detected were 

relatively small, appeared to be localized, and thus could not affect the overall adult populations. 

There was very little available information on the demography of our most abundant taxa that 

were not commercially or recreationally important. This lack of life history infonnation limited 

the application of assessment models to the ETM. 

In summary, it is unlikely that populations of fishes and crabs will to be adversely affected by 

the new combined-cycle cooling water intake. Some are commercially important taxa with 

pelagic eggs and widespread populations (e.g., white croaker). Their assessments resulted in 

either low estimated larval mortalities or small numbers of adult losses to their populations. 

Other widespread species also had low numbers of estimated adult equivalent losses to their 

populations and low estimated larval mortality, with populations that are distributed well beyond 

the zone of influence of MLPP, such as Pacific herring and Pacific staghom sculpin. 

The models used for entrainment assessment considered functions critical to the life history of 

the abundant taxa of fishes and crabs. These models were applied both at the point of 

entrainment for estimating the numbers of individuals entrained and also in the adjacent Elkhom 

Slough, Moss Landing Harbor, and Monterey Bay areas for estimating the population of 

inference. The area around MLPP includes nursery and feeding areas for many species of our 

abundant taxa, particularly goby species. These areas also extend away from MLPP zone of 

influence. In the case of Pacific herring the center of spawning biomass is located well north of 

Monterey Bay. Length measurements of larvae indicate that most of the abundant taxa were 

produced locally and thus are exposed to entrainment for a relatively short period oftime during 

their larval development. These results indicate that entrainment effects appear to be limited to 

localized effects on bay and slough species. Therefore, the potential for entrainment damage to 

commercially or recreationally source water body species is low. 

E9-053.9 6-43 MLPP 316(b) Resource Assessment 

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P.52 

6.0 Cooling Water System Impact Assessment 

Table 6-30. Summary of Estimated MLPP New Combined-cycle Entrainment Effects for 

Abundant Fishes and Cancer Crabs Based on ETM, FH, and AEL Models Using Entrainment and 

Source Water Larval Concentrations and Monterey Bay, Moss Landing Harbor, and Elkhom 

Slough Volumes (March 1999-February 2000). 

(a) Fishes 

Unidentified gobies 

Bay goby 

Blackeye goby 

Longjaw mudsucker 

Hypsoblennius spp. 

Pacific herring 

White croaker 

Pacific staghorn sculpin 

Total 

Entraininent 

2.7 x 10s 

1.5 x 108 

1.7 x 10' 

8.0 x IO6 

1.7 x 107 

4.4 x IO6 

8.6 x 10" 

* 

FH 

300,006 

* 

1,825 

497 

9,086 

235 

107 

* 

AEL 

* 

1,045,588 

16,636 

* 

10,247 

243 

* 

* 

£7W> 

0.026 

0.039 

0.043 

0.052 

0.111 

0.129 

0.016 

0.036 

ETM*) 

0.107 

0.214 

0.075 

0.089 

0.182 

0.134 

0.129 

0.118 

Unidentified gobies 

Bay goby 

Blackeye goby 

Longjaw mudsucker 

Hypsoblennius spp. 

Pacific herring 

White croaker 

Pacific staghorn sculpin 

FH 

300,006 

* 

1,825 

497 

9,086 

235 

107 

* 

Total 

Entrainment 

2.7 x 108 

1.5 x 108 

1.7 x IO7 

8.0 x 106 

1.7 x IO7 

4.4 x IO6 

8.6 x IO6 

1.0 x IO7 

Egg Survival 

• 

* 

* 

* 

* 

0.3 

* 

* 

Yolk-sac 

Survival 

Larvae 

Survival 

0.68 

* 

0.74 

0.45 

0.55 

0.22 

0.15 

* 

Eggs/year 

1,750 

* 

8,062 

38,750 

1,340 

67,000 

105,000 

* 

Unidentified gobies 

Bay goby 

Blackeye goby 

Longjaw mudsucker 

Hypsoblennius spp. 

Pacific herring 

White croaker 

Pacific staghom sculpin 

AEL 

* 

1,045,588 

16,636 

* 

10,247 

243 

* 

* 

Total 

Entrainment 

2.7 x 108 

1.5 x 108 

1.7 x IO7 

8.0 x IO6 

1.7 xlO7 

4.4 x 106 

8.6 xlO6 

1.0 xlO7 

Average 

Lifespan 

(years) 

2.5 

* . 

3.6 

2.5 

7 

11 

12 

* 

Age at 

Maturation 

(years) 

1 

* 

0.5 

0.7 

2 

2.5 

2 

* 

Early Larvae 

* 

0.013 

0.004 

* 

0.006 

0.0004 

* 

* 

Late Larvae 

through 

Juvenile FV 

Pre-Recruit 

* < 

0.536 

0.233 

* 

0.107 

0.135 

* 

* 

'Unavailable information or value that could not be computed. 

(a) ETM values calculated using source water volumes 275, 21, and 2.2 m3 x IO6. 

(b) ETM values calculated using source water volumes 22, 21, and 2.2 m3 x 106. 

E9-053.9 6-44 MLPP 316(b) Resource Assessment 
P.53 

6.0 Cooling Water System Impact Assessment 

Table 6-30 (continued). Summary of Estimated MLPP New Combined-cycle Entrainment Effects 

for Abundant Fishes and Cancer Crabs Based on ETM, FH, and AEL Models Using Entrainment 

and Source Water Larval Concentrations and Monterey Bay, Moss Landing Harbor, and Elkhom 

Slough Volumes (March 1999-February 2000). 

(b) Cancer Crabs 

Hairy rock crab 

Yellow rock crab 

Brown rock crab 

Dungeness crab 

Red rock crab 

Slender crab 

Total 

Entrainment 

1.7 x 106 

0.5 x 10s 

0.8 xlO6 

0.3 x 106 

0.2 x 10s 

0.2 x 10" 

FH 

1,039 

131 

209 

167 

60 

239 

ETM,] 

0.018 

* 

* 

* 

0.044 

0.025 

ETM<» 

0.167 

• 

* 

* 

0.044 

0.079 

Hairy rock crab 

Yellow rock crab 

Brown rock crab 

Dungeness crab 

Red rock crab 

Slender crab 

Total 

Entrainment 

1.7 x 10" 

0.5 x 106 

0.8 x 10* 

0.3 x IO6 

0.2 x 106 

0.2 x 106 

FH 

1,039 

131 

209 

167 

60 

239 

Egg 

Survival 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

Megalopal 

Survival 

0.000657 

0.000817 

0.001069 

0.000802 

0.001658 

0.001398 

Eggs/year 

1,530,907 

2,600,000 

1,756,450 

1,250,000 

1,492,500 

555,583 

Average 

Lifespan 

(years) 

4.8 

4.8 

5.5 

6.0 

4.8 

3 

Age at 

Maturation 

(years) 

1.5 

1.5 

1.5 

2.0 

1.5 

1 

'Unavailable information or value that could not be computed. 

(a) ETM values calculated using source water volumes 275, 21, and 2.2 m3 x IO6. 

(b) ETM values calculated using source water volumes 22, 21, and 2.2 m3 x IO6. 

E9-053.9 6-45 MLPP 316(b) Resource Assessment 
P.54 

6.0 Cooling Water System Impact Assessment 

6.17 Impingement Effects Assessment 

The combined-cycle intake modernization project is expected to significantly reduce historic 

impingement rates by modernization of the existing Units 1 through 5 intake. The existing 

intake structure will be modified to eliminate its 350-foot forebay tunnel. Based on intake 

structure design guidance (EPA, 1976) long tunnels or channels in front ofa facility's intake 

screens entrap fishes and invertebrates and should be avoided whenever possible. The previous 

(1979 - 1980) MLPP impingement rates reviewed in Section 5 showed that impingement rates 

measured at Units 1 through 5 intake were significantly higher that at Units 6 and 7 intake, 

particularly in the rate of crab impingement. This higher impingement rate is attributable in a 

large part to the entrapment effect ofthe Units 1 through 5 intake's extraordinarily long forebay. 

It is therefore reasonable to forecast that with the elimination ofthe existing intake forebay 

(making the intake flush to the shoreline) that the modernized intake's impingement rate would 

be equivalent to the impingement rate observed at Units 6 and 7's shoreline intake. 

The benefit, reduction of impingement losses, can be estimated by using the historical 

impingement rates described in Section 5. On this basis, the effect of moving the intake forebay 

and screens to the shoreline would have reduced the total annual impingement of fishes at Units 

1 through 5 from 2,875/day to 1,657/day and the total annual impingement of crabs from 

236/day to 139/day. In addition to this level of reduction of impingement losses achieved by 

moving the combined-cycle intake to the shoreline location, the modernized combined-cycle 

units will withdraw 44 percent less water than the existing Units 1 through 5 pumps. Lower 

volumes of cooling water withdrawal are expected to further reduce the potential for 

impingement by further lowering the combined-cycle's impingement effects. The relationship 

between rates of intake water withdrawal and rates of impingement is not strictly a direct 

relationship, due to the presence or absence of debris effects on impingement rates. A general 

relationship holds that if less water is withdrawn the potential for the impingement of organisms 

and debris will be lower. We have not attempted to quantify the expected benefits of reduced 

combined-cycle intake flows on impingement rates ofthe existing facility, but believe they 

represent a potential for significant reductions in impingement rates with the new combinedcycle units. 

New traveling screens that are planned for the combined-cycle modernized intake facility may 

also contribute to lower impingement rates. The installation of continuous-belt, incline screens 

is being investigated as a means to reduce intake screen maintenance and improve reliability. 

A biological benefit ofthe new screen designs, is that with fewer structural members, the 

effective screen area is increased and through-screen velocities reduced accordingly. The 

screens are installed at an angle, compared to the more common vertically installed screens. The 

angle ofthe screen allows gravity to keep debris on the screen surface as it clears the water and 

E9-053.9 6-46 MLPP 316(b) Resource Assessment 

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P.55 

6.0 Cooling Water System Impact Assessment 

is lifted to the spray nozzles and sluiceways. The angle of screen inclination also serves to 

increase the effective screen surface area and lower through-screen velocities from 

approximately 2.0 fps to 0.8 fps (see Table 2-1). At intake facilities where fish return systems 

are employed, lower through-screen velocities improve the survival ofthe impinged organisms 

that are returned. Though this factor does not apply to the MLPP combined-cycle intake, lower 

through screen velocities should in theory make it easier for small fishes to navigate in and out 

ofthe shoreline intake structure. However, the projected combined-cycle intake approach 

velocity of 0.5 fps is well below the swimming burst speeds of most ofthe study area's fishes. 

Lower through-screen velocities represent a small, but positive potential for lower impingement 

rates with the new combined-cycle units. 

E9-053.9 6-47 MLPP 316(b) Resource Assessment 

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P.56 

7.0 EVALUATION OF ALTERNATIVE INTAKE TECHNOLOGIES 

The purpose of this section is to evaluate alternative intake technologies for the combined-cycle 

(formerly Units 1 through 5) cooling water intake structure, which will be modified to serve the 

proposed combined-cycle (CC) units at the Moss Landing Power Plant. Though the entrainment 

and impingement effects are negligible at this point ofthe current study, altemative intake 

technologies were evaluated for their potential to further reduce biological losses. The feasibility 

and cost-effectiveness for each alternative intake technology was evaluated for the Moss Landing 

Power Plant combined-cycle units on a site-specific basis. A hierarchical evaluation system is 

used to assess which alternative intake technologies would reduce biological losses and could be 

feasible for application to the cooling water system ofthe plant. Alternative intake technologies 

were evaluated on the basis ofthe following four criteria: 

1. the alternative technology is available and proven (i.e., it has demonstrated operability 

and reliability at a cooling water intake having a similar size and environmental setting to 

that at the MLPP), 

2. implementation ofthe alternative technology will result in a reduction in the loss of 

aquatic organisms from the present operating conditions described in Section 2, 

3. implementation ofthe alternative technology is feasible at the MLPP site, based on sitespecific considerations of engineering, operations, and reliability, and 

4. the total economic cost ofthe alternative technology is proportionate to the 

environmental benefits anticipated. 

These criteria were applied to all alternative intake technologies that were considered to be 

available and proven for application at the plant (Criterion 1) and were, therefore, subjected to a 

biological evaluation (Criterion 2). Feasibility analyses (Criteria 3 and 4) were carried out for 

alternatives that would reduce biological losses. The section ends with a discussion of, and 

judgment as to, the best intake technology available for the new combined-cycle units. 

Evaluation of whether an intake technology is available and will minimize impacts requires sitespecific analyses, which are presented in this section. The design and operation of the cooling 

water systems for the new combined-cycle units are described in Section 2, along with a 

discussion ofthe physical and biological characteristics ofthe source waterbody. Sf ctions 3 

through 5 present information characterizing entrainment and impingement at the plant. This 

background information provides the site-specific framework necessary for evaluating the 

potential biological effectiveness and engineering feasibility ofeach intake technology 

considered. 

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7.0 Evaluation of Alternative Intake Technologies 

7.1 First-level Evaluation — Are the Technologies Proven 

and Available? 

Certain intake technologies and alternate intake locations were determined to be proven and 

available for consideration for the new CC units (Table 7-1). These include offshore and 

onshore intake locations and configurations, a once-through cooling water system, and 

behavioral barriers such as light, sound, bubble screens, and velocity caps. Fish diversion 

systems, such as louvers and angled screens, have been used at cooling water intake structures 

(CWIS) and can be considered for use by the CC units. Physical barriers, such as drum screens, 

center-flow screens, and vertical traveling screens, are also appropriate for further consideration. 

Fish collection and return systems, including modified traveling screens and fish pump systems 

are available considerations. 

Although not commonly used as intake technology, closed-cycle cooling systems, such as salt 

water cooling towers and air cooled condensers, have been demonstrated in power plant 

applications. 

E9-053.9 7-2 MLPP 316(b) Resource Assessment 

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7.0 Evaluation of Alternative Intake Technologies 

Table 7-1. Operational Feasibility of Intake Technologies and Operational Alternatives 

Considered for the Proposed MLPP Combined-cycle Units. 

Intake Technologies 

Intake Location 

Intake Configuration 

Behavioral Barrier 

Diversion Systems 

Physical Barrier 

Fish Collection, Removal, and 

Conveyance Systems 

Demonstrated Proven and Available 

Offshore 

Onshore 

Shoreline 

Recessed 

Light 

Sound 

Air bubble curtain 

Velocity cap (applicable to offshore 

intake location only) 

Louvers 

Angled Screens 

Centerflow screen 

Vertical Traveling screen 

Barrier net 

Gunderboom 

Modified traveling water screens 

Gravity sluiceway 

Fish pump 

Not Demonstrated Proven and 

Available 

Velocity gradient 

Electrical barrier 

Chemicals 

Magnetic field 

Chains and cables 

Media filter 

Porous dike 

Radial Well 

Stationary screen 

Horizontal traveling screen 

Caisson 

Drum screens 

Cylindrical, wedge-wire screens 

Operational and Flow-reduction Alternatives 

Maintenance and Operational 

Modifications 

Closed-cycle cooling 

Cooling water pump flow reduction 

Dredging 

Seasonal Flow Reduction 

Alternate biofouling control 

E9-053.9 7-3 MLPP 316(b) Resource Assessment 

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P.59 

I 

ffi 

I 

i 

i 

7.0 Evaluation of Alternative Intake Technologies 

1 

I 

I 

I 

1 

1 

1 

1 

I 

1 

1 

Operational and flow-reduction alternatives, such as closed-cycle cooling, seasonal energy 

curtailment resulting in flow reductions, cooling system structural modifications, temperature 

regulation, maintenance dredging ofthe intake area, and cooling water pump flow reduction are 

also regarded as proven and available technologies. Other alternative technologies failed to 

satisfy the first evaluation criterion, and hence are not considered further in the analysis. Those 

technologies and operational alternatives are discussed briefly in the following discussion. 

7.1.1 Behavioral Barriers 

Devices such as velocity gradients, electric barriers, magnetic fields, water jet curtains, hanging 

chains, visual cues and chemicals have been suggested, and in some cases evaluated, as fish 

protection measures. However, no practical applications ofthese devices have been developed 

and they are not considered available technologies for application at CWIS (Taft, 1999). Ofthe 

remaining behavioral barriers, lights, sound and air bubble curtains are carried forward to the 

next level of evaluation. 

7.1.2 Diversion Systems 

Louvers have been used effectively at several large agricultural water diversions and 

hydroelectric installations. Only one power plant cooling water intake incorporates louvers. 

However, no biological evaluations of this installation have been performed. Most of the louver 

applications to date have been with migratory species in riverine environments. Therefore, the 

ability of this alternative to protect species commonly impinged at CWIS is largely unknown. 

Further, due to the large spacings between louver slats, louver systems do not provide a positive 

barrier either to early life stages of fishes or to debris that could block the condenser tube system 

and lead to reduced operating reliability and increased maintenance. Therefore, traveling water 

screens are required downstream of louvers for CWIS applications. Future consideration of 

louver systems for protecting fishes at cooling water intakes may be warranted but would require 

extensive large-scale engineering feasibility and biological evaluations. 

Media filters, such as rapid sand filters, porous dikes, and radial well intakes, have never been 

used to provide power plant cooling water from a marine source. Prototype tests have been 

conducted that have identified debris accumulation, biofouling, and sedimentation as major 

constraints in the application of media filters in the marine environment. Results of laboratory 

and small-scale pilot studies have indicated that porous dikes might be effective in preventing 

passage ofjuvenile and adult fishes. However, entrainable organisms will generally be trapped 

in the porous medium or entrained into the pump flow. 

E9-053.9 7-4 MLPP 316(b) Resource Assessment 

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P.60 

ffi 

ffi 

m 

ffi 

1 

ffi 

i 

7.0 Evaluation of Alternative Intake Technologies 

1 

1 

1 

1 

ffi 

1 

1 

1 

1 

1 

1 

1 

1 

In the absence of demonstrated performance capabilities and operational reliability in a oncethrough power plant cooling water system, media filters are not considered to be an available 

technology for the new combined-cycle units. 

To date, large-scale CWIS applications of wedge-wire screens have been limited to two power 

plants. These screens have been biologically effective in preventing entrainment and 

impingement of larger fishes and have not caused unusual maintenance problems. This 

technology can be considered for application at CWIS. However, there are major concerns with 

clogging potential and biogrowth. Since the only two large CWIS to employ wedge-wire screens 

to date use 6.4 and 10 mm slot openings, the potential for clogging and fouling that would exist 

with slot sizes as small as 0.5 mm, as would be required for protection of entrainable life stages, 

is unknown. In general, consideration of wedge-wire screens with small slot dimensions for 

CWIS application should include in situ prototype scale studies to determine potential biological 

effectiveness and identify the ability to control clogging and fouling in a way that does not 

impact plant operation. Assuming that biofouling can be controlled, the only environment in 

which use of cylindrical wedge-wire screens may not be practicable is one without an ambient 

cross-current to carry passive organisms and backflushed debris away. 

Stationary screens have had little application at CWIS. No information is available on recent 

advances or installations of flat-panel screens for use as a fish barrier. Except on small volume 

intakes, it is expected that maintaining fixed screens in a clean condition, and thereby 

minimizing head loss, will preclude use ofthese screens. 

The traveling water screen is a standard feature at most CWIS. The ability of traveling screens 

to act as a barrier to fishes while not resulting in impingement is dependent on many site-specific 

factors, such as the size offish, location ofthe screens, and presence of escape routes. It is 

considered advantageous to locate screens close to the shoreline at the point of water withdrawal, 

as proposed for the new CC units CWIS. Traveling screens, as barrier devices, cannot be 

considered for protection of early life stages or aquatic organisms that have little or no motility. 

The horizontal traveling screen concept combines elements of diversion and collection devices 

and might have been an effective fish protection system if engineering problems could have been 

overcome. Unfortunately, years of design, research, and development efforts at two sites did not 

result in a screen that could operate reliably, even for relatively short periods oftime. There has 

been no additional work on this technology and it is not considered available for application at 

CWIS. 

Similarly, while rotary dmm screens are often mentioned as technologies for protecting fishes at 

CWIS, no evidence of applications exists. Dmm screens have been used at irrigation and 

hydroelectric facilities but, even in these applications, the screens are limited by the requirement 

E9-053.9 7-5 MLPP 316(b) Resource Assessment 

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P.61 

0 

0 

ii 

0 

n 

fi 

ll 

8 

8 

8 

7.0 Evaluation of Alternative Intake Technologies 

for maintaining constant water elevations. Dmms screens are not considered to be biologically 

effective, based on the limited data available (Eicher, 1974), and are not expected to reduce the 

numbers of organisms entrained or impinged at the plant's cooling water intake stmctures. There 

is no information available to suggest that survival of organisms impinged on dmm screens 

would be significantly different from impingement survival on conventional vertical traveling 

screens. In the absence of any predicted biological advantages, dmm screens are not considered 

to be an acceptable alternative intake technology applicable to the new combined-cycle units. 

7=2 S©c©odl=L@v@[l EvsiDyattBoo — WBiD The T®c[ftm)©l!©gy Rosuilt 

Dm BoctogieaO Bernefe? 

Each technology and operational alternative that satisfied the proven and available criterion in 

the first-level evaluation (Table 7-1) was further investigated to determine whether it would 

reduce the entrainment and impingement losses reported in Sections 4 and 5. Relevant results of 

the evaluation are integrated in this section. 

7.2.1 Closed-Cycle Cooling Water System 

A closed-cycle cooling water system at MLPP could reduce intake effects by reducing the use of 

seawater for cooling. This alternative would replace the once-through ocean cooling water 

system proposed for the new CC units with either a recirculating cooling water system and 

cooling tower(s) or air cooled condensers. 

With the cooling tower scheme, warm water from the steam turbine condensers and other 

cooling water users in the plant would flow to a new cooling tower(s) consisting of air-water 

contact surfaces (slats) and electric motor-driven fans, in the case of a mechanical draft tower, or 

contact surfaces contained in what is essentially a very large chimney in the case ofa natural 

draft tower. The recirculating water to be cooled falls from the top through the tower where it 

contacts a high air flow drawn through the tower by the fans or the draft ofthe chimney. 

Cooling occurs through partial evaporation ofthe falling water (similar to the operation ofa 

"swamp" cooler) and contact cooling of the water by the cooler air. Cooled water collects in a 

large basin beneath the tower where cooling water circulation pumps return the water to the 

condensers and other equipment uses to repeat the cycle. 

Recirculating water is lost from the process principally in two ways: evaporation from the tower 

and a "blowdown" (purge) stream. The blowdown stream is intentionally removed to prevent 

the buildup of dissolved solids in the recirculating water since the solids do not evaporate in the 

tower. A third minor loss consists of liquid water droplets (drift) entrained with the air and water 

B

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vapor leaving the top ofthe cooling tower. The evaporation, blowdown, and drift losses must be 

replenished by adding replacement ("makeup") water to the system. For a seawater recirculating 

cooling system serving the new CC units, the estimated ocean water required for makeup is about 

4.8 percent ofthe proposed once-through cooling water intake rate and consequently the 

entrainment of organisms could be reduced up to 95.2 percent. 

In an air-cooled condenser system, exhaust steam from the steam turbine generator is cooled and 

condensed in a large external heat exchanger using atmospheric air as the cooling medium. 

Large, electric motor-driven fans move large quantities ofair across finned tubes (similar in 

principle to an automobile radiator) through which the exhaust steam is flowing. Heat transfer 

from the hot steam to the air cools the steam causing it to condense. The heated air is exhausted 

to the atmosphere. In this case, there would be no seawater required for condenser cooling. 

Air-cooled condensers for power plants are very large stmctures and consume significant 

amounts of power for operation ofthe fans. They also significantly reduce steam turbine output 

due to higher condensing temperatures as compared to once-through or recirculating water 

condensers. 

The most important impacts of cooling towers are air quality, ambient noise, and aesthetics. Due to 

the height and length of cooling tower structures and their visible vapor, cooling towers have a 

visual and aesthetic impact on the surrounding area. Noise emissions during operation must be 

considered, particularly with mechanical draft towers. Extra fossil fuel is required to be burned to 

compensate for the average loss in generation at power plants where mechanical or natural draft 

towers are retrofitted. This would have a direct effect on air quality. 

7.2.2 Intake Location 

Alternative intake locations for the new combined-cycle units at the MLPP include submerged 

offshore and shoreline intake locations. The proposed shoreline intake location and configuration 

for the new CC units is the base case against which each alternative is compared. 

7.2.2.1 Offshore Intake Location 

The efficacy ofan offshore intake in reducing entrainment depends, to a large degree, on the 

vertical stratification of entrainable organisms in the water column at the point of water 

withdrawal. In such a system, a reduction in entrainment is achieved by locating the submerged 

intake at a depth where the concentration of entrainable organisms is less than at other depths. 

Although the available data are limited, entrainable organisms are expected to be distributed in 

approximately equal concentrations throughout the water column as a result of strong tidal and 

wind.mixing and the shallow depths in the immediate area ofthe MLPP (Subsection 2.2.2). 

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Water depths are typically less than 30 ft (9 m) within 2,000 ft (600 m) ofthe existing intake 

locations. Many species that have planktonic larvae which are susceptible to entrainment, such as 

flatfishes, rockfishes, white croaker, smelts, and northern anchovy, spawn in the nearshore 

waters of Monterey Bay and potentially could be more susceptible to entrainment at an offshore 

intake than under the present configuration. Because of the large tidal exchange between Moss 

Landing Harbor-Elkhorn Slough and Monterey Bay, planktonic organisms spawned in the 

harbor-slough, such as gobies and Pacific herring, would be susceptible to entrainment at an 

offshore cooling water intake sited in the area adjacent to the Moss Landing Harbor entrance 

channel. Furthermore, very little if any vertical stratification in the concentrations of planktonic 

eggs and fish larvae is expected to occur in these shallow areas, which are subject to mixing and 

turbulence from tidal currents, waves, and wind. Because the waters near the plant are wellmixed from surface to bottom by virtue ofthe large tidal prism and the turbulence at the entrance 

to Moss Landing Harbor at both flood and ebb tide stages, an offshore intake stmcture would not 

be expected to reduce the numbers of organisms entrained. 

For reducing the number of impinged organisms, the effectiveness ofa submerged offshore 

intake depends on locating the intake in an area where such impingeable organisms are not 

abundant. Many ofthe dominant groups of fishes and invertebrates (e.g., flounder and sole, 

rockfishes, white croaker, surfperches, crabs, shrimp) are typically found in association with the 

offshore bottom habitat in the vicinity ofthe site, and many ofthe typically pelagic fish species, 

such as smelts, northern anchovy, and Pacific herring, are commonly found in large schools 

which move through the water column, often concentrating near the bottom substrates during the 

daytime (EA, unpublished). In addition, submerged offshore intakes generally have higher 

approach velocities than onshore systems and use conduits within which fishes can become 

entrapped, resulting in an increase in the number of organisms impinged. Furthermore, there is a 

distinct possibility that the physical presence and nature of an offshore intake would attract many 

ofthe fishes and invertebrates inhabiting Monterey Bay (particularly surfperch, rockfishes, and 

crabs) to the intake location, and so increase the probability of entrapment and subsequent 

impingement. Thus, use of a submerged offshore intake system would probably result in rates of 

impingement higher than those observed at the existing intakes. 

In summary, an offshore intake appears to offer little or no potential for reducing the losses of 

fishes and invertebrates entrained or impinged at the new combined-cycle units intake. The 

susceptibility of planktonic organisms to entrainment would not be reduced by relocating the 

intake offshore, where tidal currents and turbulence are expected to contribute to a homogeneous 

vertical distribution of planktonic organisms. The offshore intake would also contribute to the 

entrapment of fishes and invertebrates, many of which may be behaviorally attracted to the 

offshore intake. In addition, relocation ofthe intake offshore would create a navigational hazard 

at the entrance channel to Moss Landing Harbor, and as such, might not be permitted by the 

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responsible regulatory agencies. In the absence of any evidence ofa clear potential for reducing 

entrainment and impingement losses, an offshore intake location is not considered to be an 

acceptable alternative for the new CC units. 

7.2.2.2 Alternative Onshore Location 

The general similarity ofthe shore-zone habitat along the shoreline of Moss Landing Harbor or 

Elkhom Slough suggests that the potential for entrainment and impingement would not be 

substantially different at any other available shoreline locations. The pattern of tidal currents and 

mixing in the area resulting from the large volume ofthe tidal prism relative to the volume ofthe 

harbor-slough (Subsection 2.2.0 supports the conclusion that the concentrations of organisms are 

similar throughout the local shore zone). 

During 1971 and 1972, PG&E (1973) conducted a fishery survey at four sampling stations in 

Moss Landing Harbor and Elkhom Slough. Sampling was done quarterly with otter trawls and 

both sinking and floating gill nets. A total of 713 fishes was collected from the harbor-slough 

system during three sampling periods. Statistical analyses were performed to determine whether 

differences in catches of fishes among the various sampling stations in the harbor and slough 

were statistically significant. There were no statistically significant differences in the numbers of 

fishes collected, the numbers of species, the average weights, or the average lengths of fishes 

collected at the various sampling stations throughout Moss Landing Harbor and Elkhom Slough. 

The results of this series of fishery collections provide no evidence that alternative shoreline 

intake locations are available in Moss Landing Harbor or Elkhom Slough that would result in 

reduced rates of impingement. 

Studies by Nybakken, Cailliet, and Broenkow (1977) offish populations in the Moss Landing 

area suggest that fish abundance is generally higher near the Highway I Bridge than in the area 

adjacent to the harbor entrance in Monterey Bay. Fish abundance was intermediate at sampling 

stations in Elkhom Slough. However, since no samples were collected in Moss Landing Harbor 

near the existing cooling water intake locations, the results ofthese studies cannot be used for 

comparisons useful in evaluating potential alternative intake locations that might contribute to a 

reduction in impingement losses. 

Data collected on the concentrations offish eggs and larvae and macroinvertebrates during 

plankton surveys at six stations located throughout Moss Landing Harbor and Elkhom Slough 

(EA, 1982) provide no evidence that alternative shoreline intake locations are available in the 

harbor-slough system that would reduce entrainment losses. Average daily concentrations of 

fish eggs were not significantly different among stations sampled in Moss Landing Harbor, 

although concentrations there were consistently higher than those from the upper slough stations 

at the Dairies and Kirby Park. Although the concentrations of fish larvae were lowest at the 

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sampling station directly adjacent to the existing cooling water intakes, differences in 

concentrations were not significant among stations in the harbor and lower slough. Highest 

larval fish concentrations occurred at stations in the upper slough at the Dairies and Kirby Park. 

No significant differences in the numbers of larval fish taxa were detected among all stations 

surveyed in the harbor and slough. There were no significant differences between the average 

daily concentrations of macroinvertebrates collected at the Dairies in upper Elkhom Slough, at 

the station near the Highway I Bridge, at the Moss Landing Harbor entrance channel, or adjacent 

to the existing cooling water intake locations. Macroinvertebrate concentrations were lowest at 

Kirby Park in the upper slough and at the station adjacent to the existing intake locations in Moss 

Landing Harbor. The results ofthese surveys indicate that planktonic organisms susceptible to 

entrainment are distributed by tidal currents and by habitat preference throughout Moss Landing 

Harbor and Elkhom Slough. No alternative shoreline intake location has been identified that 

would result in a reduction in entrainment losses. 

7.2.3 Behavioral Barriers 

Strobe lights have effectively repelled several different fish species in laboratory and field 

experiments. Recent studies have demonstrated that various lacustrine, riverine, and anadromous 

species will avoid strobe light. Conversely, some studies have indicated that certain species from 

similar environments or with similar life history strategies or phylogeny will not respond to 

strobe lights in a laboratory setting or under field conditions (Brown, 1999). 

Air bubble curtains generally have been ineffective in blocking or diverting fishes in a variety of 

field applications. Air bubble curtains have been evaluated at number of sites on the Great Lakes 

with a variety of species. All air bubble curtains at these sites have been removed from service. 

The focus of recent fish protection studies involving underwater sound technologies has been on 

the use of new types of low- and high-frequency acoustic systems that have not previously been 

available for commercial use. High-frequency (120kHz) sound has shown to effectively and 

repeated repel members ofthe genus Alosa (American shad, alewife, and blueback herring at 

sites throughout the U. S. (Ploskey et al., 1995; Dunning, 1995; Con Ed., 1994). Other studies 

have not shown sound to be consistently effective in repelling species such as largemouth bass, 

smallmouth bass, yellow perch, walleye, rainbow trout (EPRI, 1998), gizzard shad, Atlantic 

herring, and bay anchovy (Con Ed., 1994). Given the species-specific responses to different 

frequencies that have been evaluated, and the variable results that often have been produced, 

additional research is warranted at sites where there is no or limited data to indicate that the 

species of concern may respond to sound. 

In the near field, fish response to "sound" is probably more related to particle motion than 

acoustic pressure. Particle motion is very pronounced in the near field ofa sound source and is 

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major component of what fishes most likely sense from infrasound (frequencies less than 50 Hz). 

In the first practical application of infrasound for repelling fishes, Knudsen et al. (1992, 1994), 

found a piston-type particle motion generator operating at 10 Hz to be effective in repelling 

Atlantic salmon smolts in a tank and in a small diversion channel. Following the success of 

Knudsen et al. (1992, 1994), there was a general belief in the scientific community that 

infrasound could represent an effective fish repellent since there was a physiological basis for 

understanding the response of fishes to particle motion. The potential for currently available 

infrasound sources to effectively repel fishes has been brought into question by the results of 

more recent studies. Given these results, it appears that infrasound sources need to be further 

developed and evaluated before they can be considered an available technology for application at 

CWIS. 

Response to mercury light has been shown to be species specific; some fish species are attracted, 

others repelled, and others have demonstrated no obvious response. Therefore, careful 

consideration must be given for any application of mercury lights to avoid increasing 

impingement of some species. 

Electric barriers have been shown to effectively prevent the upstream passage of fishes. 

However, a number of attempts to divert or deter the downstream movement of fishes have met 

with limited success (Bengeyfield, 1990; Kynard and O'Leary, 1990). Consequently, past 

evaluations have not lead to permanent applications. Electric barriers have been used with 

limited success in freshwater, but because of low electrical resistance, no application of electric 

fish barriers has been made in salt or brackish waters. Given their past ineffectiveness and 

hazard potential, electric screens are not considered a viable technology for application at CWIS. 

A velocity cap was not considered, since its applicability is restricted to offshore intakes, which 

were rejected for possible use at the plant (Subsection 7.2.2.1). 

In general, behavioral barriers have not proven consistently effective in reducing the numbers of 

fishes impinged at CWIS. In addition, such barriers are not expected to reduce the numbers of 

entrained organisms or the impingement rates of macroinvertebrates. Behavioral barriers are not 

considered to represent an effective alternative for reducing entrainment or impingement at the 

plant. 

7.2.4 Physical Barriers 

The applicability of physical barrier screens, such as vertical traveling screens, centerflow 

screens, barrier nets, and the relatively new Gunderboom for reducing biological losses 

associated with entrainment and impingement at the new combined-cycle units is evaluated in 

the following discussion. 

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Traveling screens of various types (e.g., through-flow, dual-flow, and center-flow with coarse 

and fine mesh) are standard features at CWIS. Without the addition of various fish handling 

design (e.g., fish lifting buckets) and operating features (e.g., continuous screen operation), 

traveling screens generally result in high mortality to all but the hardiest species that become 

impinged on them. They have no capacity for protecting entrainable sized organisms. If these 

screens are placed relatively flush with the face ofthe CWIS, as proposed for the CC units, 

traveling screens can be considered to offer protection to juvenile and adult fishes that have the 

swimming capability to avoid impingement. 

Under the proper hydraulic conditions (primarily low velocity) and without heavy debris loading, 

barrier nets have been effective in blocking fish passage into water intakes. Several recent 

applications in the midwest United States have been presented (Michaud and Taft, 1999). At the 

Ludington Pumped Storage Plant on Lake Michigan, a 2.5-mile long barrier net, set in open 

water around the intake jetties, has been successful in reducing entrainment of all fish species 

that occur in the vicinity ofthe intake (Reider et al., 1997). The net was first deployed in 1989. 

Modifications to the design in subsequent years led to a net effectiveness for target species (five 

salmonid species, yellow perch, rainbow smelt, alewife, and chub) of over 80 percent since 1991, 

with an effectiveness of 96 percent in 1995 and 1996. 

In 1993 and 1994, Orange and Rockland Utilities, Inc. sponsored a study ofa 3.0-mm, fine mesh 

net at its Bowline Point Generating Station on the Hudson River (LMS, 1996). In 1993, fine 

suspended silt caused the net to clog and sink. In 1994, spraying was not effective in cleaning the 

net when it became fouled by the algae Ectocarpus spp. Excessive fouling caused two ofthe 

support piles to snap, ending the evaluation (LMS, 1996). In both years, abundance ofthe target 

ichthyoplankton species, bay anchovy, was too low to determine the biological effectiveness of 

the net. On the basis of studies to date, the researchers conclude that a fine mesh net may be a 

potentially effective method for preventing entrainment at Bowline Point. However, pending 

further evaluation, this concept is considered to be experimental. 

In conclusion, barrier nets can be considered a viable option for protecting fishes provided that 

relatively low velocities (generally less than 1 ft/sec) can be achieved and debris loading is light. 

A thorough evaluation of site-specific environmental and operational conditions is generally 

recommended. The application of barrier nets at MLPP is not considered practicable given the 

potential debris loading that exists. 

The Gunderboom consists of polyester fiber strands which are pressed into a water-permeable 

fabric mat. Beginning in 1995, Orange & Rockland Utilities, Inc. has sponsored an evaluation of 

the Gunderboom to determine its ability to minimize ichthyoplankton entrainment at the Lovett 

Generating Station on the Hudson River (LMS 1996b, 1997, and 1998; ASA, 1999). Despite 

difficulties in keeping the boom deployed and providing adequate cleaning in 1995-1997 studies, 

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results of studies in 1998 show a large reduction in entrainment and it appears that deployment 

and cleaning problems may have been resolved for this site. At this time, the Gunderboom 

system is still considered to be experimental but its successful use at Lovett may change that 

status within several years. 

7.2.5 Fish Collection, Removal, and Conveyance Systems 

Several modifications to conventional vertical traveling screens have been considered in recent 

years in an attempt to increase their biological effectiveness. Some information is available on 

the effectiveness of various screen rotation frequencies from studies conducted at the MLPP (see 

PG&E, 1983; Section 4.2). Information is also available for impingement survival of chinook 

salmon from the Columbia River (Page et al., 1976, 1978) and of striped bass from the Hudson 

River (EA, 1979; Texas Instruments, Inc., 1977). Data from these and other studies are used in a 

general way to provide additional information useful in examining the potential effectiveness of 

modified vertical screens at the new combined-cycle units. The effectiveness of screen 

modifications for reducing impingement losses is discussed in Subsections 7.2.5.1 through 

7.2.5.4. 

In addition, consideration has recently been given to the potential effectiveness ofa screen mesh 

smaller than the standard 3/8 in. (9.5 mm) but larger than 0.04-in. (1.0-mm) fine-mesh screen 

material for reducing the combined losses of entrainment and impingement. 

Modifications to the design and operation of vertical traveling screens, such as the use of 

continuous screen rotation, low-pressure spray washes, and fish lifting buckets, are alternatives 

that have been used to increase the biological effectiveness of conventional vertical traveling 

screens. In many cases, continuous screen rotation has resulted in substantial increases in fish 

and invertebrate survival. Increasing screen rotation frequency at the MLPP Units 6 ahd 7 intake 

contributed to a substantial increase in impingement survival for both surfperch and rockfishes 

(see PG&E, 1983; Table 4-7). However together these species constituted only 15 percent ofthe 

fishes impinged at the Moss Landing Power Plant. The use ofthese modifications would have 

no benefit without a fish return system. However, these studies also suggest that impingement 

survival of species such as northern anchovy, Pacific herring, smelt, and silversides, which 

together constituted approximately 75 percent ofthe impinged fishes, will probably not be 

improved substantially by increased screen rotation frequency. 

Limited information is available to assess the potential of this modification for improving 

impingement survival for the species offish impinged in greatest abundance at the Moss Landing 

Power Plant (Section 5). Among these, species such as plainfin midshipman, gobies, and crabs 

appeared to have high survival, but fragile species such as northern anchovy, Pacific herring, 

smelt, and silversides had low survival on the existing intake screens. Although available data 

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are incomplete, it is expected that survival of fragile species would be increased by the addition 

offish buckets, low-pressure spraywashes, and continuous rotation of screening surfaces. In 

particular, impingement survival of surfperch and rockfishes is expected to increase. 

7.2.5.1 Fine-Mesh Screens 

In addition to the fish handling provisions noted above, traveling screens have been further 

modified to incorporate screen mesh with openings as small as 0.5 mm to collect fish eggs and 

larvae and return them to the source water body. For many species and early life stages, mesh 

sizes of 0.5 to 1.0 mm are required for effective screening. Various types of traveling screens, 

such as through-flow, dual-flow, and center-flow screens, can be fitted with fine mesh screen 

material. 

The absence ofdata on the impingement survival ofthe fish eggs and larvae present in the 

vicinity ofthe MLPP and the uncertainties regarding operational reliability of fine-mesh screens 

in a marine environment similar to that of Moss Landing Harbor-Elkhorn Slough preclude the 

conclusion that fine-mesh would be a biologically effective and operationally acceptable 

alternative intake technology for use at the new CC units. 

7.2.5.2 Fish Return Conveyance Systems 

There are two basic types of conveyance for the return of impinged organisms and debris to the 

waterbody, one using a trash pump to transport material away from the intake and one using 

gravity flow. The pump-augmented return has the advantage of minimizing recirculation and reimpingement of debris and organisms on intake screens due to relatively large transport distance 

capability, but often results in mechanical abrasion and high mortality of organisms. The gravity 

sluiceway return system reduces mechanical abrasion, but may cause significant reimpingement 

because of relatively limited transport distances. It is concluded that no further consideration 

should be given to a fish pump return system for diverting fishes from new CC units intake 

because ofthe uncertainties associated with the effectiveness of such a system in successfully 

diverting the fish species found at the site and returning them alive to Moss Landing Harbor. 

Fishes that were returned alive to the Harbor would be susceptible to disease and predation at the 

fish return discharge point due the stress of passage through the pumped fish return system. 

Previous studies have concluded that the potential magnitude of reduction in impingement losses 

attributable to a gravity fish conveyance system is uncertain (PGandE, 1983). However, the 

combination of a modification to the screens and their operation and the installation of a 

modified screenwash gravity sluiceway return system for the proposed CC units may have 

potential for improving impingement survival and will be considered in the in the next step ofthe 

analysis. Because ofthe uncertainties associated with determining the biological effectiveness 

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and various engineering design and operational considerations, a testing program would be 

required prior to implementing a modified screen system at the new CC units intake. 

7.2.5.3 Summary 

Modifications of vertical traveling screens that include fish buckets, a low-pressure wash system, 

provisions for continuous rotation, and a fish retum system represent an alternative technology 

with the potential for reducing impingement losses of several ofthe species offish and 

invertebrates impinged at the proposed new CC units intake stmcture. In the absence ofa 

demonstrated potential for long-term survival for impinged ichthyoplankton, such as northern 

anchovy, Pacific herring, surfperch, rockfishes, white croaker and flatfishes, fine-mesh screens 

are not considered to represent an acceptable alternative intake technology for use in reducing 

the combined losses resulting from entrainment and impingement at the modified intake. 

Insufficient data preclude a detailed comparison ofthe potential survival offish eggs and larval 

fishes impinged on modified vertical traveling screens (fine-mesh screen material, fish buckets, 

low-pressure spraywash, continuous rotation) and centerflow screens (fine-mesh screen material, 

continuous rotation). To date, no studies have been conducted of long-term survival of fishes 

impinged on centerflow screens operated in a power plant cooling water intake, and it is unlikely 

that survival would be any higher than for vertical traveling screens. Preliminary test ofthe 

Gunderboom barrier net (Section 7.2.4) indicate that this technology is both reliable and 

effective at eliminating impingement and dramatically reducing entrainment effects. Installation 

and operation ofa barrier screen is feasible for the MLPP CC units. 

7.2.6 Intake Maintenance And Operational Modifications 

Maintenance activities and operational modifications which may reduce entrainment and 

impingement losses include maintenance dredging in front of the cooling water intake, 

reductions in circulating water pump volume, seasonal curtailment of cooling system operation, 

use of alternative biofouling schemes, stmctural modifications ofthe cooling system, and 

through-plant temperature regulation. 

7.2.6.1 Maintenance Dredging 

Sediment accumulation within a cooling water intake stmcture may reduce the open area ofthe 

intake, resulting in increased water velocities. Increased velocities approaching the intake 

stmcture will, in many cases, result in increased rates of impingement. Depth measurements 

made in the intake stmcture ofthe Moss Landing Power Plant (PG&E, unpublished) indicated 

that sediment had accumulated that would reduce the available cross-sectional area ofthe intake 

(Subsection 2.1.3.2). Sediment accumulation in retired Units 1 through 5 intake stmcture had 

reduced the cross-sections ofthe forebays by an average of 30 percent, ranging from 10 percent 

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of Bay 3 to 52 percent of Bay 1. Bays 1 and 6 had the lowest mean intake velocity, and the 

velocity at Bay I was lower than expected from the degree of blockage. These anomalies were 

attributed to the previous hydraulic characteristics ofthe Units 1 through 5 intake stmcture and 

the considerable distance to the circulating water pumps. Sediment accumulation in the Units 6 

and 7 intake was considerably less than that in the Units 1 through 5 intake. Accumulated 

sediment had reduced the cross-sections ofthe Units 6 and 7 forebays by an average of 13 

percent, ranging from 10 percent at Bay 7-3 to 18 percent at Bay 6-1. The reduction in the 

number of organisms impinged that would result from removing accumulated sediment and 

reducing intake velocities cannot be estimated on the basis of available data. There is little 

doubt, however, that maintenance dredging ofthe plant intakes would reduce approach velocities 

and potentially reduce the number of impinged organisms. A disadvantage of dredging is that 

the re-suspension of sediments has a potential negative impact on nearby benthic invertebrates, 

particularly filter feeders. Consequently, while dredging the intake might reduce impingement 

losses, a reduction in population concentrations of some benthic invertebrates would be expected 

during and shortly after the dredging. 

7.2.6.2 Circulating Water Pump Volume Reduction 

A reduction in the number of circulating water pumps in operation and/or installation of variablespeed circulating water pumps represents an alternative operational strategies for reducing 

cooling water volumes and intake approach velocities, and hence reducing the number of 

organisms entrained and possibly those impinged. Changes in condenser back-pressure resulting 

in reduced turbine cycle thermal efficiency, along with increased temperature differentials 

through the condenser system (delta-T), are to be expected when cooling water flow rates are 

reduced during generation. Although a reduction in cooling water volume is expected to result in 

a decrease in the number of entrained organisms, the associated increase in delta-T would 

increase the discharge temperature and thermal plume size. 

Reducing the operation ofthe circulating water pumps during periods when generation is low or 

is not occurring would reduce the numbers of organisms entrained and possibly those impinged. 

Because ofthe entrainment mortality resulting from predation by biofouling organisms that 

colonize the cooling water system conduits at the plant, entrainment losses are expected to be 

reduced in approximately the same proportion as the reduction in cooling water flow rates. 

Examination of monthly capacity factors (see PG&E, 1983; Tables 2-2 and 2-5) and monthly 

cooling water volumes (see PG&E, 1983, Tables 2-3 and 2-6) indicates that circulating water 

pump operation typically exceeds generation. Although the reduction in entrainment losses that 

could be achieved through a reduction in circulating water pump operation has not been precisely 

quantified, it is concluded that this alternative operational mode offers the potential for reducing 

entrainment losses. 

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7.0 Evaluation of Altemative Intake Technologies 

The number of fishes impinged is expected to be reduced by reducing circulating water pump 

operation. However, no data are available from the 1979-1980 impingement study (Section 5) to 

quantify the magnitude of reduction in fish impingement that would result from various 

circulating water pump operational modes. Additional studies would be required to quantify the 

effect on impingement of short-term reductions in pump operation. 

Despite the lack of quantitative data, it is concluded that short-term (hourly or daily) reductions 

in the volume of cooling water that coincide with reduced generation have a high probability of 

reducing entrainment and impingement losses. 

7.2.6.3 Seasonal Curtailment of Energy Production 

Seasonal curtailment of cooling system operation could reduce the numbers of organisms lost by 

entrainment and impingement. The amount ofthe reduction depends on the length oftime the 

cooling system is out of operation and the concentration of organisms during the period of 

curtailment. Based on the seasonal distribution of entrainment and impingement (PG&E, 1983), 

two peak periods of abundance, Febmary through March (the peak period of northern anchovy, 

goby, and silverside entrainment in 1978-1980) and August through September (the peak period 

of impingement in 1978-1980), were selected as possible periods for curtailment. Seasonal 

curtailment of cooling system operation would result in a reduction in the numbers of organisms 

entrained and impinged, and is therefore considered to be an alternative technology for further 

consideration for the new CC units. 

7.2.6.4 Alternative Biofouling Schemes 

The biofouling control procedure currently used at the Moss Landing Power Plant consists of 

intermittent chlorination (Subsection 2.1.2) for slime control and heat treatment for biofouling 

control. These control schemes have been adequate to control marine growth and are planned for 

application to the new CC units as well. 

Alternative biofouling control schemes which can be considered for application at the new 

combined cycle units include the following: 

1; relocation of the proposed chlorine injection point for new cc units to the modified Units 

1 through 5 intake head works, 

2. increased chlorine dosage, 

3. increased frequency of chlorination from intermittent dosage to continuous application, 

4. use of alternative chemical toxins, including bromine, chlorine dioxide, chlorine bromide, 

and ozone, 

5. application of toxic coatings on cooling system conduit walls, 

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7.0 Evaluation of Altemative Intake Technologies 

6. oxygen depletion (stagnation), 

7. mechanical cleaning, 

8. increased heat treatment, and 

9. increased water velocities within cooling system conduits. 

All ofthese alternatives, with the exception of increasing chlorination frequency to continuous 

application and increased water velocities within the cooling water conduits, are expected to 

have the potential of reducing entrainment cropping by controlling the colonization of cooling 

water system conduits by marine fouling organisms. Because ofthe toxicity of chlorine to non 

target organisms (entrained fish eggs, larvae, and juveniles and invertebrates), continuous 

chlorination would potentially result in 100 percent entrainment mortality. Increasing the 

velocity of cooling water through the conduits to levels above 10 fps (300 cm/sec) has the 

potential of reducing colonization by marine organisms. Increasing cooling water velocities 

would, however, substantially increase mechanical damage to entrained ichthyoplankton and 

macroinvertebrates and increase impingement losses. Increasing velocities within the cooling 

water conduits is therefore not considered to be an effective method of reducing the combined 

losses resulting from entrainment and impingement at the new combined cycle .units. 

As described earlier, the proposed project includes modifications to the existing Units 1 through 

5 intake system to allow periodic heat treatment for removal of biofouling organisms after the 

new CC units are installed. This new heat treatment capability should reduce the level of 

predation on entrained organisms experienced with the historic Units 1 through 5 operation and 

no further changes to the proposed system should be necessary. 

Further discussion is given in Subsection 7.3.6 regarding the current anti-fouling program for 

Units 6 and 7 as well as the proposed program for the new CC units. 

7.2.6.5 Discharge Temperature Regulation 

Discharge temperatures are relatively low at the MLPP throughout the year. In 1999, the annual 

average discharge temperature was 69° F, with a peak 24-hr discharge temperature of 810F.' 

Exposure to discharge temperatures above 86° F (30° C) during cooling system transit are lethal 

to entrained striped bass larvae. Therefore, thermal stresses are not expected to be a significant 

cause of mortality to entrained fishes or invertebrates. Discharge temperature regulation is not 

expected to result in a significant reduction in entrainment losses since nearly 100 percent ofthe 

organisms are lost to biofouling predation in the cooling system (PG&E, 1983). 

i 1998 NPDES Discharger Self-Monitoring Report for MLPP 

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7.0 Evaluation of Alternative Intake Technologies 

7.2.6.6 Cooling System Modifications 

Stmctural modification of cooling system components (pumps, conduits, condensers) is not 

considered to be an effective alternative to reduce the mortality of entrained organisms. Too 

little quantitative information is available to isolate specific sources of mortality within a cooling 

water system. Design parameters for specifying pressure regimes, circulating water pump design 

and operation, tolerable shear stresses, and cooling system designs for minimizing mechanical 

abrasion have not been developed. 

7.2.7 Conclusion: Biological Evaluation 

Based on results ofthe biological evaluation (Section 7.2), the following was concluded: 

1. There are no reasonable alternative intake locations that would reduce entrainment and 

impingement losses, 

2. Behavioral barriers would not be expected to reduce numbers of organisms exposed to 

either entrainment or impingement, 

3. Entrainment and impingement losses would not be substantially reduced by use of 

traveling screens, barrier nets, a Gunderboom, or a fish pump system, 

4. A screen mesh size of 5/16 in. (0.8 cm) is acceptable; there is insufficient data available 

to determine whether the survival of fish eggs and larvae impinged on fine-mesh screens 

would exceed the survival of organisms entrained through the MLPP cooling systems, 

and 

5. Cooling system stmctural modifications and discharge temperature regulation are not 

expected to reduce the mortality of entrained organisms substantially. 

The following alternative intake technologies may reduce entrainment and/or impingement 

losses for the new CC units and were therefore selected for feasibility analysis: 

1. seasonal curtailment of cooling system operation, 

2. replacement ofthe proposed once-through cooling system with a closed-cycle system 

(either salt water cooling tower(s) or air cooled condensers), 

3. modified vertical traveling intake screens and gravity screenwash fish return system for 

the revamped Units 1 through 5 shoreline intake stmcture to be used for the new 

combined-cycle units, 

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7.0 Evaluation of Alternative Intake Technologies 

4. short-term reductions in circulating water pump operation when the units are operating at 

low loads or are out of service, 

5. periodic dredging ofthe intake area to reduce intake velocities, and 

6. alternative biofouling control schemes. 

7.3 Third-Level Evaluation — Feasibility And Cost Analysis 

Each alternative technology that satisfied the biological reduction criterion (Section 7.2) and 

differed in design or operation from that presently proposed for the new CC units cooling water 

system was evaluated with regard to engineering feasibility, operation, and reliability. In 

addition, the total economic cost in 1999 dollars associated with each feasible alternative was 

estimated. Cost estimates reflect direct capital costs and indirect costs (e.g., the loss of 

generating capacity) where applicable. 

7.3.1 Seasonal Curtailment 

Section 7.2.6.3 identifies seasonal curtailment of cooling system operations to reduce 

entrainment and impingement losses. The economic consequences of seasonal curtailment are 

such that Duke Energy would not constmct a CC plant that could not operate for four months of 

the year. In this scenario, existing Units 6 and 7 would continue to operate at high capacity 

levels in the absence of new, more efficient generation at MLPP. Continued use of Units 6 and 

7 in the absence of new generation would result in greater impingement/entrainment since the 

impacts of Units 6 and 7 are greater than the proposed CC plant. 

Once the CC plant is constmcted, seasonal curtailment ofthe new CC units will likely be 

infeasible because of increasing demand for electrical energy in the central and northern 

California load centers and the uncertain availability of surplus energy from other sources to 

replace it. Setting aside the question of alternative energy sources to reliably serve customers 

and the demand for electricity, the estimated costs of replacement energy alone that would result 

from curtailment of operation ofthe new CC units from Febmary through March (the peak 

period of northern anchovy, goby, and silverside entrainment from the 1979 -1980 MLPP 316(b) 

study) and from August through September (the peak period of impingement determined from 

the same study) are summarized in Table 7-2, based on expected operation ofthe new CC units 

and recent system power price projections. The estimated net loss of future power sales revenue 

corresponding to the curtailment of new CC units operation during Febmary through March plus 

August through September is about $59 million per year. Fluctuating fuel costs, which are a 

major factor in the cost of replacement energy, make accurate projections of net future energy 

E9-053.9 7-20 MLPP 316(b) Resource Assessment 

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revenue difficult. If curtailment could be implemented during these two periods, it could reduce 

biological losses resulting from both entrainment and impingement. This curtailment strategy, 

however, is particularly inappropriate since it would severely reduce electrical generating 

capacity during the critical summer period when electrical demand is highest. 

An altemative approach to using curtailment to reduce biological losses is to schedule 

maintenance outages to coincide with periods of greatest biological loss. However, it is 

inappropriate to schedule maintenance during the critical summer period. It may be possible to 

schedule maintenance during Febmary and March when electrical loads are not as high and when 

other resources such as hydropower are more readily available. However, scheduled 

maintenance outages for fossil-fueled plants are generally of much shorter duration than at 

nuclear-fueled plants, where this option has sometimes been considered. 

It is not expected that frequent significant scheduled outages for the new CC units will occur. 

Minor maintenance outages for cleaning ofthe new units will be scheduled for short periods, 

about four hours of downtime, approximately once per combustion turbine generator (CTG) unit 

per month. Annual inspections will also be scheduled for each unit that will require about one 

day offline per CTG. More thorough inspections, requiring about two days, will take place 

every three to five years. Major overhauls, requiring an outage of about two weeks, typically 

occur about every eight years. Therefore, no significant biological benefits could be achieved by 

attempting to schedule maintenance outages during predicted sensitive periods. 

Daily curtailment of cooling system operation (e.g., at night or when load is low) is another 

alternative approach for reducing biological loss. It is likely that that the new CC units will be 

turned down or some CTG units taken offline during periods of decreased demand, such as late 

evening and early morning. However, these units will be among the most efficient fossil fuel 

units available in the state system and are expected to be used frequently to meet base load 

demand day and night. Therefore, although it is expected that the new units will sometimes 

operate at reduced load with corresponding benefits to marine organisms, a commitment to 

regular curtailment of cooling system operation is considered to be impractical for the new CC 

units, based on the projected need for highly efficient sources of base load generation and the 

additional need for rapid response to electrical demands within the system. 

The various strategies for curtailment of cooling system operation would result in a reduction of 

both entrainment and impingement losses in an amount that would depend on the abundance of 

organisms present during the period of curtailment and the duration ofthe outage. However, 

curtailment of operation ofthe CC units beyond what would occur from normal scheduling is not 

acceptable, because it removes the generating capacity ofthe plant from reliable service when it 

is needed to serve system loads. The availability of replacement power is uncertain. However, if 

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Units 6 and 7 would continue to operate in lieu ofthe new generating facilities the impacts on 

impingement/entrainment would be greater for a given level of power generation. 

For the cost, operational reliability, and flexibility reasons discussed above relative to the 

potential improvements in biological impacts, curtailment of power generation as a method of 

reducing entrainment and impingement losses for the new CC units is not considered to be a 

feasible alternative. 

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Table 7-2. Estimated Cost of Replacement Energy during two Periods of Operation Curtailment 

for the Moss Landing Combined-cycle Units. 

Period of 

Curtailment 

February 

March 

Energy 

Payment 

($MW-hr)* 

27.45 

34.60 

Fuel Cost (S/106 

Btu)** 

2.52 

2.48 

Operating Time 

(hrs/month)*** 

605 

670 

Output When 

Operating 

(MW)  

1060 

1060 

Lost Revenue 

($)** *** 

6,614,000 

4,713,000 

August 

September 

55.35 

45.75 

2.46 

2.48 

670 

650 

1060 

1060 

27,429,000 

19,902,000 

Total 58,658,000 

•Projected energy prices for NYMEX California-Oregon border for year 2000, from Megawatt Daily, Dec. 22, 1999. 

••Projected fuel costs at NYMEX Henry Hub from Gas Daily, Dec. 22, 1999. 

•••Estimated operating time assuming about 90 percent capacity factor. 

••••Lost energy payments less avoided costs of fuel (based on nominal heat rate for new CC units of 6,800 Btu/kW-hr. 

•••••Revenue contributions must cover all operating costs and a return on capital. 

7.3.2 Closed-Cycle Cooling Systems 

Potentially applicable systems at the MLPP include mechanical or natural draft recirculating 

cooling towers and air cooled condensers. The operation ofthese systems is described in 

Section 7.2. The following sections evaluate the cost and feasibility at MLPP. (The use ofthese 

systems would be preferred, from the standpoint of power plant operating economics, to the 

seasonal curtailment alternative discussed in the previous section). 

7.3.2.1 Mechanical Draft Cooling Tower 

Two possibilities for a source of recirculating cooling water exist at the Moss Landing site, fresh 

ground water or seawater. Although freshwater systems have the advantage of smaller makeup 

water requirements due to less dissolved solids, a continuous freshwater makeup supply of about 

5,400 gpm would be required for a freshwater cooling tower system serving the new CC units at 

MLPP. Due to the current and expected future limitations of freshwater supply in the area, it 

was decided that a freshwater system was not realistic and the evaluation would consider 

seawater cooling towers. 

Seawater mechanical draft cooling towers for the MLPP CC units would consist of two 

stmctures, one for each unit, each approximately 410ftx53ftx55ft high. Ocean water 

makeup for this system would be supplied from the existing Units 6 and 7 cooling water pumps 

or new pumps at the existing Units 1 through 5 pumpwell. The circulating water and blowdown 

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stream would contain salinity (dissolved solids) approximately 50 percent greater than local 

seawater. The estimated combined full capacity flow rates for both towers are: 

Recirculating water 250,000 gpm 

Blowdown (returned to 7,800 gpm 

ocean) 

Makeup (withdrawn from 12,000 gpm 

ocean) 

The blowdown stream will contain residual concentrations of biocides, dispersants, and other 

conditioning chemicals, in higher concentrations than the existing once-through cooling water 

discharge. Blowdown will be disposed by discharge to the ocean at approximately 84 °F. 

The estimated total installed capital costs associated with the two forced draft mechanical 

cooling towers for the new CC units including towers, basins, chemical additive systems, and 

supporting systems are about S12 million more than the proposed once-through cooling water 

system.2 Figure 7-1 shows a possible location where the new cooling towers could be installed 

at MLPP. 

Mechanical draft cooling towers would significantly diminish the net power output and operating 

efficiency ofthe modernized plant. The combination ofthe higher steam turbine condenser 

temperatures caused by the recirculating cooling system and the higher plant electrical load 

compared to the once-through cooling water case would decrease the net power output available 

from the new CC units by about 25 MW (for the same fuel consumption). This reduction in 

capacity will have to be made up by other, probably less efficient and more polluting power 

sources. The estimated annual revenue losses from this decrease in capacity is approximately 

$2 million per year.3 Over the life ofthe project the use of cooling towers will cost 

approximately $60 million. 

Visible fog plumes could be expected (probably frequent during the winter) due to condensation 

in the atmosphere ofthe considerable amount of water vapor emitted from the top of towers. 

2

 Amount shown is the additional capital investment required to substitute cooling towers for the proposed oncethrough cooling water system. 

3

 Based on a net margin approximately $ 10/MW-hr and a 90 percent capacity factor. 

E9-053.9 7-24 MLPP 316(b) Resource Assessment 

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Figure 3-2. Conceptual Location 

for Mechanical Draft CoolIng Towers 

a m •*» *«i 

DUKE/FLUQR DANIEL' 

nor n v 

cic 

crxamco CICLI 

<*n\ i*t.oi"c 

cc*«cc*iu»i. ot.tic« 

JL o»trr Crxxif-C tc * 

^ r -.•r-h.-^.— 

Figure 7-1. Moss Landing Power Plant alternative closed-cycle cooling mechanical draft cooling tower location. 

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Cooling tower drift "raining" out ofthe plume could cause a nuisance salt water deposition on 

the surrounding area which could result in increased equipment maintenance requirements in the 

plant and adverse effects on nearby agriculture, and at times on local businesses and residences. 

Drift would also lead to increased fine particulate salt emissions from the facility in the form of 

dissolved solids emitted with the drift droplets. For the salt water tower considered, the 

estimated additional particulate emissions to the atmosphere associated with drift would be about 

750 lb/day. This quantity would represent a substantial increase in PM10 emissions from the 

project and could cause adverse air quality impacts. 

Mechanical cooling towers are a significant potential source of overall power plant noise impacts 

on surrounding areas due to the significant quantity of elevated equipment such as fans, motors, 

and gears. 

For all the above reasons, the proposed once-through cooling water system is preferred to a 

mechanical draft tower. 

7.3.2.2 Natural Draft Cooling Tower 

A natural draft cooling tower system is very similar in principal to the mechanical draft system. 

The primary difference is that the mechanical fans to move the cooling air are replaced by what 

is essentially a very large chimney. Air is drawn in at the base ofthe tower due to the less dense 

(more buoyant), warmer air exiting the top ofthe tower. This natural air circulation contacts the 

returned cooling water inside the tower and cools the water by evaporation and direct contact 

with the cooler air. Thus the cooling water recirculation, blowdown, and makeup rates and 

quality are about the same as for the mechanical (forced draft) system. 

A natural draft cooling tower to serve the Moss Landing combined-cycle units would be 

approximately 250 feet in diameter at the base and about 370 feet in height. Figure 7-2 shows a 

conceptual location for the new natural draft cooling tower. 

The estimated total installed cost for natural draft tower is about $13 million more than the 

proposed once through cooling water system5 

4

 Assuming drift is 0.0005% of recirculating water. 

5

 Incremental capital investment for natural draft cooling tower in lieu of proposed once-through cooling water 

system. 

E9-053.9 7-26 MLPP 316(b) Resource Assessment 

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Figure 7-2. Moss Landing Power Plant alternative closed-cycle cooling natural draft cooling tower location. 

E9-053.9 7-27 MLPP 316(b) Resource Assessment 

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7.0 Evaluation of Alternative Intake Technologies 

Most of the potential negative impacts described for the mechanical draft towers would also be 

associated with a new natural draft tower for the MLPP. The blowdown discharge to the ocean 

would be the same. Drift losses and the resulting PM10 emissions would also occur, although at 

somewhat reduced rates. Noise impacts would be less. The auxiliary power requirement would 

be reduced, due to the lack of mechanical fans, but the steam turbines output would still be 

decreased by about 22 MW. The estimated annual revenue losses from this decrease in capacity 

are approximately $1.7 million per year.6 Over the 30-year life ofthe project the use ofa natural 

draft cooling tower will increase power costs by approximately $51 million. 

Visible condensate plumes would also periodically occur at the top ofthe tower and, obviously, 

the overall visual impact due to the size ofthe tower is much more significant. 

This alternative was eliminated, primarily because ofthe very adverse visual impacts of such a 

massive stmcture and the high capital investment required. 

7.3.2.3 Air-cooled Condensers 

Air-cooled condensers for power plants are very large stmctures and consume significant 

amounts of power for operation ofthe fans. Noise impacts are substantial and, without extensive 

abatement, are generally greater than for mechanical towers. Air cooled condensers also 

significantly reduce steam turbine output due to higher condensing temperatures as compared to 

once-through or recirculating water condensers. 

It is estimated that an air-cooled condensers for the new CC units, one for each unit, would each 

occupy about 0.75 acre of plot space, extend to a height of 80 to 90 feet. Overall, the net output 

for the two new CC units would be reduced by a total of more than 60 MW7 (the size ofa small 

power plant). Figure 7-3 shows the plot space that would be consumed. 

6

 Based on a net margin of $ 10/M W-hr and a 90 percent capacity factor. 

7

 For summertime operation; the corresponding reduction for wintertime operation is about 37 MW. 

E9-053.9 7-28 MLPP 316(b) Resource Assessment 

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Figure 3-4. Conceptual Location 

for Air Cooled Condensers 

fS DUKE^FLUQR DANIEL' 

cowi'urj cictC 

COXCIuAL OISICH 

* l » COO,(a CC*OOrtI« Or I I 

mjj?t i 

Figure 7-3. Moss Landing Power Plant alternative closed-cycle cooling air-cooled condensers location. 

E9-053.9 7-29 MLPP 316(b) Resource Assessment 

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7.0 Evaluation of Alternative Intake Technologies 

The estimated additional total installed cost for the two air cooled condensers, as compared to the 

proposed once through cooling system is about $30 million combined total costs for both the CC 

units. The estimated annual revenue losses from the associated decrease in capacity is about 

Q 

$3.8 million per year. Over the 30-year expected life ofthe project the use ofair cooled 

condensers would cost about $114 million. 

Because ofthe substantial loss in net power output, the significant adverse visual impacts of 

these systems, and the very large associated costs, the air-cooled condenser option is eliminated 

from additional consideration. 

7.3.3 Modified Vertical Traveling Screen and Fish Return System for 

the New CC Units Intake 

As described in Section 2, the existing (retired) Units 1 through 5 intake stmcture will be 

modified to serve as a shoreline intake stmcture (inclined screens in the shoreline stmcture) for 

the new CC units. This shoreline intake stmcture will eliminate the large length of intake 

conduit upstream ofthe screens and the lower cooling water withdrawal rates will result in 

decreased intake velocities, both of which should substantially reduce entrapment of organisms 

within the intake conduit, as compared to the previously used intake configuration. The intake 

stmcture and screen configuration will be designed for a screen approach velocity of 0.5 fps (15 

cm/sec) at mean lower low water, which is consistent with U.S. EPA guidelines for the design of 

new cooling water intake stmctures. At higher tide levels, which will be most ofthe time, the 

screen approach velocity will be less. 

This alternative evaluates the use ofa vertical traveling screen with fish handling features instead 

ofthe proposed inclined screen. For some species of fishes, impingement mortality can be 

reduced through stmctural modifications to conventional vertical traveling screens and a change 

in intake screen operation from intermittent to continuous rotation (Subsection 7.2). The 

stmctural differences to the currently proposed modifications for the new CC units for this 

alternative would include replacement of the proposed inclined screen with a conventional 

vertical screen, installation of watertight fish collection baskets along the screen, both lowpressure and high-pressure wash systems, and a fish return sluiceway. A differential control and 

two-speed motor are also included, so that when the screen is operated continuously it rotates at 

slow speed, and as the of number fishes and/or debris loads increase, the screen rotation rate can 

be automatically increased. In general, 3/8-in. (0.9-cm) screen mesh would be used on modified 

vertical traveling screens. 

8

 Based on a net margin of $10/MW-hr and a 90 percent capacity factor and assuming an annual average capacity 

reduction of 48.5 MW. 

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Screens modified to reduce impingement mortality need to be accompanied by a sluiceway 

(Subsection 7.2) designed to return impinged organisms to the receiving waterbody. Most 

installations of modified traveling screens use a dual sluiceway return system, a gravity 

sluiceway return system for impinged organisms removed from the screens by the low-pressure 

spraywash and another sluiceway for debris removed by the high-pressure spraywash. 

The alternative modified screen system evaluated for the CC units intake stmcture is shown in 

Figures 7-4 and 7-5. This system would consist of new vertical screens installed in the existing 

Units 1 through 5 intake stmcture behind the existing bar racks. The screens would be smooth 

top mesh and furnished with fiberglass fish baskets and differential speed controls. Low and 

high-pressure spray wash systems are provided to wash recovered fish and other organisms into a 

fish trough on the top ofthe intake stmcture. Impinged debris will be washed into a separate 

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P.87 

.,— NEW TRAVELING SCREEN 

STOP LOGS 

Figure 7-4. Traveling water screen proposal number 1. 

,- riSM RETURN TROUGH <COVERED> 

. CKTCNO& fROU MTAKE STRUCTURE 

TO HARIJOR AT COAST MCMWAT 

BRVCC 

DC8PJS COLLECTION 

CONTAtNCR 

Figure 7-5. Traveling water screen proposal number 1 (overhead view). 

debris trough, also on top ofthe stmcture. A new water filled fish sluiceway would extend from 

the fish trough to Moss Landing Harbor to return recovered organisms to the Harbor at the 

shoreline approximately 800 feet north ofthe intake stmcture. 

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For the new CC units, the incremental capital costs ofa modified screen are those associated 

with the difference in cost for a vertical screen plus the fish handling modifications and fish 

conveyance system as compared to the proposed inclined screen system. Modification ofthe 

proposed inclined screens to vertical intake screens with the additional features described for fish 

handling (fish baskets, deflectors, dual spraywash system, differential controls, fish return 

system, etc.) would have an incremental capital cost of approximately $2.6 million more than the 

proposed inclined screen system. 

7.3.4 Reductions in Circulating Water Pump Operation 

A reduction in the number of circulating water pumps in operation is an operational strategy for 

reducing cooling water volume use and intake approach velocities, and hence the rates of 

entrainment and impingement. 

The currently proposed configuration ofthe new combined-cycle units will allow reduced 

cooling water pump operation during certain reduced load operating scenarios. As described in 

Section 2, the presently proposed new facilities consist of two essentially independent 530 MW 

units. Each unit is provided with two CTG/HRSG trains, which supply steam to one steam 

turbine generator (STG)/condenser set. Only the STG condensers require the use of significant 

amounts of cooling water. The STGs are provided for the sole purpose of recovering (in essence 

recycling) excess heat from the combustion turbines to create additional energy, and thereby are 

a significant reason for the very high thermal efficiency ofthe combined cycle process. 

Three cooling water pumps per 530 MW unit will supply cooling water to the condenser in the 

unit they serve (a total of six new cooling water pumps for the entire 1,060 MW addition). If 

only one ofthe two new units is operating, only three ofthe six new cooling water pumps would 

mn to serve it. In certain other operating conditions it may be possible to also reduce cooling 

water flow rates. For example, if one unit is operating at significantly reduced capacity such as 

only one ofthe two CTG/HRSG trains on line, it may possible to satisfactorily operate that unit 

with only two of its three cooling water pumps operating. 

Another approach to reduce cooling water flows to the minimum level necessary to maintain 

efficient operation ofthe unit at a specific generating load would be to install variable-flow 

pumps or modify the existing pumps to incorporate variable features. Since the combined-cycle 

units are expected to mn near,full capacity for most ofthe year, which dramatically reduces the 

potential benefits of variable flow devices, this alternative will not be evaluated for the new 

units. As discussed above, it will be possible to reduce the number of CC unit cooling water 

pumps in operation from six to as few as two during part load conditions which, in effect is a 

variable flow capability. Units 6 and 7 are expected to operate at reduced loads more frequently 

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in the future especially during lower demand periods. Therefore, the use of variable flow was 

analyzed for the existing units. 

The pumps currently in use for Units 6 and 7 are limited to no-flow or full-flow operation. Since 

each pump serves only one-half of its unit's split condenser and the steam from the steam turbine 

flows to both halves ofthe condenser, both pumps must mn when the unit is operating, even at 

reduced loads. However, with variable-frequency controls or variable flow vanes the Unit 6 and 

7 pumps could be operated at cooling water flow rates that match reduced unit loads, reducing 

the numbers of organisms entrained and impinged. The magnitude ofthe reductions in 

entrainment and impingement losses would depend on the reduction in cooling water flows and 

the abundance of organisms at the times when system demand allowed operation ofthe 

circulating water pumps at reduced flow rates. 

Three types of variable flow technologies were considered for retrofit application on the Units 6 

and 7 pumps, variable frequency drive (VFD), variable vanes, and multiple speed drive. VFD 

was selected as the preferred choice, based on experience of application, complexity of 

operation, and availability of suppliers. A VFD modification would consist of replacement of 

the existing pumps and motors with new pumps and heavy duty motors with an upgraded motor 

cooling system as well as a new VFD unit for each pump. The VFD unit varies the frequency of 

electrical current to the pump motor, and therefore its rotational speed, based on the flowrate 

required. 

The estimated total installed additional9 capital cost ofthe VFD modifications for the four 

cooling water pumps at Units 6 and 7, including new pumps, new motors and four new VFD 

units is approximately $3.6 million. 

Reduction of cooling water flow during reduced load operation will decrease the thermodynamic 

efficiency ofthe steam cycle due to higher condenser outlet temperatures, which will result in 

less power generation for a fixed fuel firing rate. Reduction of cooling water flow is also limited 

to the extent that the condenser tubes need to be flooded with cooling water for proper operation 

of the steam turbine generators. 

Based on the likely marginal entrainment/impingement benefits due to the limitations for 

reducing cooling water flow at reduced loads for Units 6 and 7, the significant capital investment 

required, and generation efficiency penalty, the variable flow alternative is not considered 

further. 

9

 As described in the project AFC, the existing Units 6 and 7 cooling water pumps have deteriorated due to age and 

will be replaced as part ofthe proposed project. It is presently planned to replace the existing pumps with new 

conventional constant flow pumps. The cost indicated here is the incremental cost to install new VFD pumps 

instead ofthe new constant flow pumps. 

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7.3.5 Dredging the Intake Area 

Sediment deposition during normal operation of the cooling water systems ofthe Moss Landing 

Power Plant gradually occurs in Moss Landing Harbor in front ofthe plant and adjacent to the 

area ofthe intake bar rocks. Past sediment deposition has caused a decrease in the crosssectional area ofthe intake forebays and a corresponding increase in intake approach velocities. 

Periodic dredging ofthe intake area as needed is expected to reduce intake velocities and thus the 

potential number of fishes impinged, and to increase the operational efficiency ofthe pumps. 

The MLPP has instituted a regular program of intake velocity measurement to determine when 

dredging is needed in front ofthe cooling water intakes to decrease approach velocities; Intake 

velocity measurements are taken at least annually and corrective dredging scheduled as needed. 

Since this program is ongoing and will be expanded to include the new CC units intake in the 

future, no further consideration of dredging is warranted. 

7.3.6 Alternative Biofouling Treatment Schemes 

Chlorination and heat treatment are currently used at the MLPP in an effort to control slime 

accumulation on condenser surfaces and colonization ofthe cooling water systems by 

macroinvertebrates such as barnacles, mussels, and hydroids. 

Data from the 1979 intra-cooling-system mass balance study at Units 1 through 5 (Table 3-5 of 

PG&E, 1983) suggest that substantial losses of entrained larval fishes by macroinvertebrates may 

have occurred in this cooling water intake conduit prior to the retirement of those units. This 

predation probably occurred because, historically, it was only possible to remove 

macroinvertebrates through heat treating in the portion ofthe intake system from the pumpwell 

to the condensers. Colonizing organisms were not regularly removed in approximately 350 feet 

of intake conduit between the pumpwell and the shoreline. 

Heat treatment ofthe Units 6 and 7 cooling water system, accomplished by recirculation of warm 

condenser outlet water, is used to control macroinvertebrates between the condenser outlet gates 

and the intake inlet gates. Equipment included in the heat treatment involves the inlet tunnel 

from the inlet gates to the condenser outlet gates, circulating water pumps and traveling screens. 

The current NPDES Permit requires the following biofouling controls: "For Units 6 and 7 

(discharge 002), heat treatments will be conducted approximately once every one to four months 

in each ofthe four conduits." In addition, "the maximum temperature ofthe discharge shall not 

exceed the natural temperature ofthe intake water by more that 40° F (22.2° C)." At a 

minimum, twelve heat treatments are conducted a year with the maximum being 48 a year. At 

the minimum of 12 heat treatments per year, at a maximum temperature of 40° F above the 

natural temperature ofthe intake for two hours, the discharge will be impacted with 24 hours a 

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year of 40° F above the natural temperature ofthe intake and at 48 heat treatments the impact 

will be 96 hours. 

In addition to heat treatment, 14 -16 wt percent sodium hypochlorite (bleach) solution is injected 

periodically into the circulating water tunnels just after the traveling screens for control of microfouling (microscopic algae and bacteria growth) on condenser surfaces. The current dosage at 

Units 6 and 7 is approximately 20 minutes per tunnel three times per day for a total of 

approximately 60 minutes per day per tunnel. Residual chlorine levels at the discharge are less 

than 0.2 mg/l as required by the NPDES permit. 

Treatment periods and frequencies for the new combined-cycle units will be similar to those used 

for Units 6 and 7 with the possibility of some dosage adjustments as necessary when the units 

come on line. It is currently planned to inject hypochlorite solution at the inlet to the new CC 

condensers rather than at the suction ofthe cooling water pumps as currently practiced for Units 

6 and 7. 

As described in Section 2, the proposed modifications to the existing Units 1 through 5 intake 

system to accommodate the new CC units include internal stmctural changes to allow heat 

treatment of the entire cooling water supply conduit system from the shoreline intake to the 

condenser inlet. It is expected that the heat treatment procedures and schedules for the new CC 

units cooling water system will be similar to those currently used for Units 6 and 7. This new 

heat treatment capability for the entire length of inlet conduit should correct the observed 

entrainment losses during the historic operation of Units 1 through 5 and further consideration of 

alternate biofouling controls is not warranted at this time. 

7.4 Summary and Conclusions 

The preliminary biological benefits, costs, and engineering constraints ofthe alternative intake 

technologies considered in Section 7.3 are summarized below. On the basis of this information, 

a recommendation is made as to the best intake technology available for the new combined-cycle 

units. 

An examination was made ofthe relative effect of operation ofthe plant's cooling water system 

on fish and macroinvertebrate populations. As the field studies of intake effects near completion, 

no evidence has been found to indicate that cooling water system operations ofthe new 

combined-cycle and existing MLPP generating units will result in an adverse impact on the 

populations offish and invertebrates inhabiting Moss Landing Harbor, Elkhom Slough, and 

Monterey Bay. Most ofthe organisms entrained and impinged were species that are distributed 

widely by both ocean currents in Monterey Bay and along the Pacific coast, and by the large tidal 

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exchange in Moss Landing Harbor-Elkhorn Slough. The broad extent and movement ofthese 

species along the coast reduces the risk of localized population effects. In addition, the species 

whose larvae are entrained typically have very high natural mortality rates. The overwhelming 

majority ofthe numbers offish larvae entrained to date is represented by species of no 

commercial or recreational value. None ofthe entrained or impinged species are protected or of 

special concern. 

For these reasons, it was concluded at this time that the impact ofthe existing and proposed 

modernized Moss Landing Power Plant's operation on marine life has been and will continue to 

be undetectable, and that there is no certainty that implementation of alternative intake 

technologies designed to further reduce entrainment or impingement mortality would result in a 

detectable increase in population abundance for fish and invertebrate species inhabiting the 

Monterey Bay region and the adjacent coastal waters. The recommendations and discussion of 

alternative intake technologies presented here are based in part on this conclusion. 

7.4.1 Discussion 

Alternative intake technologies considered for the new CC units include: 

1. seasonal curtailment of cooling system operation, 

2. closed-cycle cooling systems, 

3. fish collection modifications ofthe proposed intake screens, and screenwash sluiceway 

return system, 

4. reductions in circulating water flow rates, 

5. periodic dredging ofthe intake area; and 

6. alternative biofouling control schemes. 

Each ofthese alternatives is expected to offer some potential for reducing the losses of 

organisms by entrainment and/or impingement. 

Curtailment of cooling system operation would result in reductions of both entrainment and 

impingement losses. The level of reduction would depend on the abundance of organisms 

present during the period of curtailment and the duration ofthe curtailment. The economic 

consequences of this alternative are so severe that Duke Energy would probably abandon the CC 

units project. This scenario would result in the associated impacts of higher cost and less reliable 

electricity for California consumers and increased operation of Units 6 and 7, which require 

significantly more cooling water per MW-hr generated, and have greater marine impacts, than 

the proposed CC units. Therefore, curtailment of power plant operation as a method of reducing 

entrainment and impingement is not a feasible alternative. 

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I 

1 

1 

1 

I 

I 

7.0 Evaluation of Alternative Intake Technologies 

1 

1 

1 

1 

I 

1 

Closed-cycle cooling options (mechanical draft cooling towers, natural draft cooling tower, and 

air cooled condensers) were eliminated on the basis of unacceptable environmental impacts and 

constmction and operating costs. Drift droplets and solids "raining" out ofthe cooling tower 

plumes could cause a nuisance liquid deposition on the surrounding area and significant 

additional particulate emissions. Potential impacts to local agriculture and equipment would 

occur from deposition ofthese drift salts. Mechanical draft cooling towers and air cooled 

condensers are a significant potential source of overall power plant noise impacts on surrounding 

areas. All three closed-cycle alternatives significantly reduce plant output due, primarily, to 

reduced steam turbine generator efficiency, and, secondarily, to increased internal plant loads. 

Likewise, all three options would result in significant visual impacts, particularly the natural 

draft tower. For all the above reasons, the proposed once-through cooling water system is 

preferred to a closed-cycled cooling systems. 

Modifications ofthe proposed inclined traveling screens for the refurbished shoreline intake 

stmcture to include vertical traveling screens, fish buckets, a low-pressure spraywash system and 

gravity screenwash sluiceway, with provisions for continuous rotation have the potential for 

increasing impingement survival of surfperch and rockfish. Impingement survival of species 

such as northern anchovy and topsmelt probably would not be improved by use of modified 

intake screens. Incorporation of screen modifications and a fish return system in the new CC 

units intake could reduce impingement mortality up to 10 percent based on the percent 

composition of recoverable, impinged species. Additional mortality resulting from passage 

through the fish return system, including increased susceptibility to disease and predation at the 

sluiceway discharge, would reduce the expected biological benefits of this alternative. The 

estimated incremental capital cost of modifying the intake screens to include fish-handling 

facilities wbuld be approximately $2.6 million (1999 dollars) more than the proposed inclined 

traveling screen system. Neither the additional indirect O&M costs nor the costs of engineering 

studies that would be needed to ensure reliable intake screen performance under periodic high 

detrital loading were quantified, because ofa lack of industry-wide experience with modified 

intake screens under such conditions. Consideration would also need to be given to the potential 

aesthetic problem, both visual and of odor, created by return of organisms that did not survive 

impingement to the confines of Moss Landing Harbor. Because ofthe low impact of 

impingement losses and the relatively high costs involved, installation ofthese modified intake 

screens and fish return for the new CC units is not recommended. 

Reduction in circulating water pump operation to coincide with periods of reduced electrical 

generation or when a unit is out of service has also been identified as a biologically effective 

method of reducing the losses of organisms through entrainment and impingement. The Moss 

Landing Power Plant can be operated at reduced loads with less than full circulating water flow, 

either through removing pumps from service or through installation of variable-speed motor 

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7.0 Evaluation of Alternative Intake Technologies 

controls. Reducing cooling water flow during extended unit outages is standard operation at the 

plant and will be practiced for the new CC units. The estimated incremental installed capital cost 

of variable speed motors and controls for Units 6 and 7, in addition to the upgrades already 

proposed in the project, is about $4 million. This cost is considered to be disproportionate to the 

potential benefits resulting from a reduction in entrainment cropping and impingement losses 

because ofthe low impact ofthe present mode of cooling system operation. 

Periodic dredging ofthe intake area to reduce approach velocity is believed to indirectly reduce 

the impingement rate for fishes. No reduction in entrainment or impingement of 

macroinvertebrates is expected. Because sediment accumulates in the vicinity ofthe intakes, the 

area is periodically dredged as part ofthe standard operation ofthe plant and will be continued 

after installation ofthe new CC units. 

The modifications ofthe Units 1 through 5 intake system to serve the new CC units will include 

a design improvement to enable heat treating the entire length ofthe intake conduit, rather than 

just a fraction as was the case during previous operation of Units 1 through 5. This improvement 

will reduce the numbers of biofouling organisms lining the conduits and therefore reduce the 

number of entrained fish and crab larvae preyed upon by these fouling organisms under the 

previous operating conditions. 

Alternative chemical biocides, application of toxic coatings, and routine mechanical cleaning are 

not considered to be effective alternative biofouling control techniques. 

7.4.2 Conclusions 

The proposed new combined-cycle units CWIS design represents the best technology available. 

This conclusion is based on the preliminary finding of relatively insignificant entrainment and 

impingement effects and consideration of various demonstrated alternative technologies, 

including potential biological effectiveness for further reducing entrainment and impingement 

losses, engineering feasibility, and cost-effectiveness, as outlined in the guidance manual (EPA, 

1977). 

Intake modifications associated with the combined-cycle modernization will improve the 

previously experienced environmental impacts ofthe existing intake stmcture. New shoreline 

traveling screens will be installed to significantly reduce the entrapment (and subsequent 

impingement/entrainment) which formerly occurred in the 350-foot intake tunnel between the 

intake stmcture and previous screen location. Additional modifications will allow the heat 

treatment for biofouling/predator organism removal in the entire cooling water supply conduit. 

Based on impingement rates reported at the neighboring Units 6 and 7 CWIS, these 

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7.0 Evaluation of Alternative Intake Technologies 

controls. Reducing cooling water flow during extended unit outages is standard operation at the 

plant and will be practiced for the new CC units. The estimated incremental installed capital cost 

of variable speed motors and controls for Units 6 and 7, in addition to the upgrades already 

proposed in the project, is about $4 million. This cost is considered to be disproportionate to the 

potential benefits resulting from a reduction in entrainment cropping and impingement losses 

because ofthe low impact ofthe present mode of cooling system operation. 

Periodic dredging ofthe intake area to reduce approach velocity is believed to indirectly reduce 

the impingement rate for fishes. No reduction in entrainment or impingement of 

macroinvertebrates is expected. Because sediment accumulates in the vicinity ofthe intakes, the 

area is periodically dredged as part ofthe standard operation ofthe plant and will be continued 

after installation ofthe new CC units. 

The modifications ofthe Units 1 through 5 intake system to serve the new CC units will include 

a design improvement to enable heat treating the entire length ofthe intake conduit, rather than 

just a fraction as was the case during previous operation of Units 1 through 5. This improvement 

will reduce the numbers of biofouling organisms lining the conduits ahd therefore reduce the 

number of entrained fish and crab larvae preyed upon by these fouling organisms under the 

previous operating conditions. 

Alternative chemical biocides, application of toxic coatings, and routine mechanical cleaning are 

not considered to be effective alternative biofouling control techniques. 

7.4.2 Conclusions 

The proposed new combined-cycle units CWIS design represents the best technology available. 

This conclusion is based on the preliminary finding of relatively insignificant entrainment and 

impingement effects and consideration of various demonstrated alternative technologies, 

including potential biological effectiveness for further reducing entrainment and impingement 

losses, engineering feasibility, and cost-effectiveness, as outlined in the guidance manual (EPA, 

1977). 

Intake modifications associated with the combined-cycle modernization will improve the 

previously experienced environmental impacts ofthe existing intake stmcture. New shoreline 

traveling screens will be installed to significantly reduce the entrapment (and subsequent 

impingement/entrainment) which formerly occurred in the 350-foot intake tunnel between the 

intake stmcture and previous screen location. Additional modifications will allow the heat 

treatment for biofouling/predator organism removal in the entire cooling water supply conduit. 

Based on impingement rates reported at the neighboring Units 6 and 7 CWIS, these 

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E9-053.9 8-7 MLPP 316(b) Resource Assessment 

4-28-2000