PRELIMINARY MODELING OF POTENTIAL ... - DeepWater Desal · DeepWater Desal ESPreliminary Intake...

ESLO2011-040.3

DeepWater Desal

PRELIMINARY MODELING OF POTENTIAL IMPACTS FROM OPERATION OF A DESALINATION FACILITY OCEAN INTAKE

August 22, 2012

Submitted to:

Dr. Brent Constanz DeepWater Desal 7532 Sandholdt Rd, Ste 6 Moss Landing, CA 95039

Prepared by:

141 Suburban Rd., Suite A2, San Luis Obispo, CA 93401 805.541.0310, FAX: 805.541.0421

Environmental

Executive Summary

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling ES-1

Executive Summary

This report presents the results of preliminary modeling to assess the potential for impacts to marine organisms resulting from the intake of seawater by an ocean water desalination plant off Moss Landing, California that is being proposed by DeepWater Desal (DWD) LLC. The objective of this assessment is to develop and test new developments in the analytical approach to the Intake Effects Assessment process and take an early look at the potential entrainment rates based on information about the desalination project which is current at the time of writing. The intake for the proposed DWD facility is expected to have a maximum design capacity of 94,640 m3 (25,000,000 gal) per day, which equals a rate of 17,360 gpm. This assessment only considers the potential effects of the intake from the entrainment of small planktonic organisms including the eggs and larvae of fishes and invertebrates into the system. Assessment of impingement of larger organisms on the screens at the opening to the intake was not included because the intake will be designed to ensure a through screen velocity of less than 0.5 feet per second (fps), which is the standard used for compliance with California state and U. S. federal policy for power plant ocean intakes. The potential for impacts to fishes and invertebrates due to entrainment at the intake location is evaluated using the Empirical Transport Model (ETM), a modeling approach that has been used on similar ocean intake projects and is the standard approach in California for assessing impacts due to power plant and desalination plant ocean intakes.

The modeling approach used for this assessment is the latest refinement in the use of the ETM for assessing the effects of ocean intakes in California. Almost all previous uses of the ETM in California have relied on biological sampling of the entrainment and source waters to estimate the daily proportional entrainment (PE), which is usually calculated for each taxon for each survey as the ratio of the estimated numbers of larvae entrained per day to the larval population estimates within specific volumes of the source water. The PE estimates calculated for many of the previous studies conducted in California showed that the estimates were, in many cases, reasonably close to the volumetric ratio of the intake to the sampled source water used in the PE calculation. This was especially common at intakes located along the open coast in areas with relatively homogeneous habitat such as the nearshore areas off the Huntington Beach Generating Station, an area not dissimilar to many nearshore areas in Monterey Bay. The volumetric approximation of PE is a reasonable approach when the species specific concentrations of larvae at the intake location are approximately equal to the species specific concentrations of larvae in the source water population. This allows the daily mortality to be estimated as the ratio of the volume entrained to the estimated volume of the source water. Although the volumetric approach to PE has not been used in California, this approach was used in the original formulation of the ETM, which was used to estimate impacts due to an intake along a river. Using this approach, the only biological data necessary for the model were the estimates of larval durations for the taxa likely to be subject to entrainment. Due to preliminary nature of this analysis, the availability of existing biological and oceanographic data from the area around the intake location, and the plans for more detailed sampling in the future, the modeling approach used for this assessment was considered appropriate.

Executive Summary

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling ES-2

The data necessary for the ETM volumetric model include the expected daily volume of the intake 94,640 m3 (25,000,000 gal) which was based on an intake flow rate of 65.7 m3 (17,360 gal) per minute and the volumes of the source water, which were estimated separately for each taxon for each month using CODAR data on ocean currents available through Central & Northern California Ocean Observing System (CeNCOOS). Data on surface currents over the entire Monterey Bay and surrounding coastline from CeNCOOS CODAR stations were adjusted to midwater column speeds using data from an ADCP current meter that is also maintained by CeNCOOS and is located just offshore from the intake. The use of CODAR for determining the source water areas potentially affected by entrainment is a substantial improvement over previous assessments in California that relied on point-source data from one or two ADCP current meters.

Using the source water estimates derived from the CODAR back-projections and adjusted by a kernel density analysis to eliminate the 5% least frequently occurring cells, the estimated annual mortalities due to entrainment by the proposed DWD intake of a maximum of 94,640 m3 (25,000,000 gal) per day were very small, approximately 0.20 percent or less, for the four coastal fishes analyzed, reflecting the small intake volume relative to the source water (Table ES-1). The back-projections indicate that the majority of the impacts would be restricted to areas close to shore in the central and northern portions of the bay for northern anchovy and the three other taxa.

Table ES-1. Annual mortality estimates (PM) and average of monthly source water volumes used in ETM modeling for larvae from four fishes found in the nearshore areas of Monterey Bay.

Fish Taxon Average Source

Volume (km3) Annual PM

northern anchovy 3.405 0.00168

white croaker 1.053 0.00154

blue rockfish 0.318 0.00212

KGB rockfish 0.573 0.00201

Acknowledgements

The information in this report relies heavily on data available through CeNCOOS using the network of instruments deployed by the State of California's Coastal Ocean Currents Monitoring Program (COCMP). The CODAR data was obtained and back-projection processing was completed by Mr. Brian Zelenke. The final content of the report benefited from comments on earlier versions from Dr. Peter Raimondi, University of California, Santa Cruz, and Dr. Jeffrey Paduan at the U. S. Naval Postgraduate School, Monterey, California.

Table of Contents

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling i

Table of Contents

Executive Summary ...................................................................................................................1

1.0 INTRODUCTION.......................................................................................................... 1-1

2.0 MODEL AND DATA METHODS ............................................................................... 2-2

2.1 Empirical Transport Model (ETM) ............................................................................ 2-2

2.2 Biological Data Used in Modeling ............................................................................ 2-6

2.2.1 Sampling Methods.............................................................................................. 2-6

2.2.2 Taxa Selected for Analysis ................................................................................. 2-7

2.2.3 Larval Durations ................................................................................................. 2-7

2.3 MLPP Source Water Body Calculations.................................................................... 2-9

2.3.1 Data Sources and Processing.............................................................................. 2-9

2.3.2 CODAR Back-Projections ............................................................................... 2-11

2.3.3 Kernel Density Estimates of Source Area and Volume ................................... 2-17

2.3.3.1 Total Source Water Body .......................................................................... 2-17

2.3.3.2 Source Water Volume ............................................................................... 2-18

3.0 IMPACT ASSESSMENT ANALYSIS RESULTS ..................................................... 3-1

3.1 Larval Durations ........................................................................................................ 3-1

3.2 Larval Seasonality ...................................................................................................... 3-4

3.3 Impact Assessment Mortality Estimates .................................................................... 3-6

4.0 IMPACT ASSESSMENT DISCUSSION AND CONCLUSIONS ............................ 4-1

5.0 FUTURE DIRECTION ................................................................................................. 5-1

6.0 LITERATURE CITED ................................................................................................. 6-1

List of Tables

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling ii

List of Tables

Table 2-1. Collection specifications for source water sampling at MLPP. ............................................... 2-7

Table 2-2. Average concentrations and number collected of fish taxa at three stations (N1, S1 and Harbor Mouth) during daytime high and low tide sampling from September 1999 through May 2000 for Moss Landing Power Plant (Tenera 2000a). ...................................................................................... 2-8

Table 2-3. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 46 days for each corresponding sample month for northern anchovy. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for the taxon (also shown). ................... 2-19

Table 2-4. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 17.23 days for each corresponding sample month for white croaker. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for the taxon (also shown). ........ 2-20

Table 2-5. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 7.95 days for each corresponding sample month for the KGB rockfish complex. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for that taxon (also shown). 2-21

Table 2-6. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 7.95 days for each corresponding sample month for blue rockfish. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for that taxon (also shown). ........................ 2-22

Table 3-1. Statistics of larval fish lengths from samples collected near Moss Landing (white croaker) and near Diablo Canyon Power Plant (rockfish and anchovy). Estimated larval durations are calculations using statistics and literature based growth rates. The estimate for rockfish was used for both blue and KGB rockfish larvae. ................................................................................................................... 3-2

Table 3-2. Mortality estimation (PM) for northern anchovy eggs and larvae at the intake location based on a planktonic duration of 48.3 d. Source water volumes calculated from kernel density estimates for back-projections from March–July 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)48.3 d. Survivals with weights (fi) of zero were not included in the calculation of PM. ................................................................................ 3-7

Table 3-3. Mortality estimation (PM) for white croaker eggs and larvae at the intake location based on a planktonic duration of 17.2 d. Source water volumes calculated from kernel density estimates for back-projections from January–June 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)17.2 d. Survivals with weights (fi) of zero were not included in the calculation of PM. ......................................................... 3-8

List of Tables

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling iii

Table 3-4. Mortality estimation (PM) for KGB rockfish complex larvae at intake location based on a larval duration of 7.95 d. Source water volumes calculated from kernel density estimates for back-projections from February–July 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)7.9 d. Survivals with weights (fi) of zero were not included in the calculation of PM. ................................................................................ 3-9

Table 3-5. Mortality estimation (PM) for blue rockfish complex larvae at the intake location based on a larval duration of 7.95 d. Source water volumes calculated from kernel density estimates for back-projections from January–August 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)7.9 d. Survivals with weights (fi) of zero were not included in the calculation of PM. .............................................................................. 3-10

Table 4-1. Annual mortality estimates (PM) and average of monthly source water volumes used in ETM modeling for the CIQ goby complex larvae which are transported out of the Moss Landing Harbor-Elkhorn Slough and larvae from four fishes found in the nearshore areas of Monterey Bay. ........... 4-3

List of Figures

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling iv

List of Figures

Figure 1-1. Map showing location of terminus of the intake line previously used to supply fuel oil to the Moss Landing Power Plant. ............................................................................................................... 1-1

Figure 2-1. Location of stations sampled during the MLPP 316b study. .................................................. 2-5

Figure 2-2. Locations of a) M0 current meter in relation to plankton sampling locations (N1 and S1) and the intake location, and b) close up of plankton sampling locations and the two proposed DWD intakes in relation to nearshore subtidal bathymetry. A potential location for a deepwater intake is also shown. ......................................................................................................................................... 2-9

Figure 2-3. Ocean surface current vectors measured on October 1, 2010 at 0000 UTC in the Monterey Bay, California region by the CeNCOOS CODAR SeaSonde stations (black triangles). Shown are vectors of both the 6 km (3.7 mile) resolution coverage offshore (left) and the higher 2 km (1.2 mile) resolution coverage closer to the coast, shaded according to their velocity per the color-bar (right).2-10

Figure 2-4. The a) U and b) V components of velocity measured over a representative period (approximately two days) at the surface by CODAR and at depth by the M0 ADCP. .................... 2-11

Figure 2-5. CODAR back-projections scaled to ADCP data from buoy M0 and averaged over the 4-20 m (13–60 ft) depth range for dates ending on a) October 1, b) November 1, c) December 1, 2010, and d) January 1, 2011. The back projections use 30 randomly selected start times on the hour ± 1 day. Each back-projection changes color from blue to green to red to represent the time periods of 0–10 d, 11–20 d, and 21–30 d, respectively, for each projection. ................................................................. 2-14

Figure 2-6. CODAR back-projections scaled to ADCP data from buoy M0 and averaged over the 4-20 m (13-60 ft) depth range for dates ending on a) February 1, b) March 1, c) April 1, and d) May 1, 2011. The back projections use 30 randomly selected start times on the hour ± 1 day. Each back-projection changes color from blue to green to red to represent the time periods of 0–10 d, 11–20 d, and 21–30 d, respectively, for each projection. ................................................................................................. 2-15

Figure 2-7. CODAR back-projections scaled to ADCP data from buoy M0 and averaged over the 4-20 m (13-60 ft) depth range for dates ending on a) June 1, b) July 1, c) August 1, and d) September 1, 2011. The back projections use 30 randomly selected start times on the hour ± 1 day. Each back-projection changes color from blue to green to red to represent the time periods of 0–10 d, 11–20 d, and 21–30 d, respectively, for each projection. ................................................................................ 2-16

Figure 2-8. Total source water body extent for northern anchovy eggs and larvae in Monterey Bay based on kernel density estimation of 46-day back-projections for the five months of February to June 2011. The 300 m depth contour is indicated offshore. ..................................................................... 2-19

Figure 2-9. Total source water body extent for white croaker eggs and larvae in Monterey Bay based on kernel density estimation of 17.23-day back-projections for the six months of January to June 2011. The 300 m depth contour is indicated offshore. ............................................................................... 2-20

Figure 2-10. Total source water body extent for KGB rockfish complex eggs and larvae in Monterey Bay based on kernel density estimation of 7.95-day back-projections for the six months of February to July 2011. The 45 m depth contour is indicated offshore. ............................................................... 2-21

List of Figures

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling v

Figure 2-11. Total source water body extent for blue rockfish eggs and larvae in Monterey Bay based on kernel density estimation of 7.95 day back-projections for the eight months of January to August 2011. The 90 m depth contour is indicated offshore. ....................................................................... 2-22

Figure 3-1. Length frequency analysis for white croaker larvae collected from MLPP studies. Below the percentage frequency is a box plot representing the range of 98 percent of the data values with the mean shown as the small filled circle, and the median, and the 25% and 75% quartiles shown by vertical lines with the width height of the box indicating the percent of the data within the interval.3-3

Figure 3-2. Length frequency analysis for a) northern anchovy and b) rockfish larvae collected from studies off Diablo Canyon Power Plant. The box plots were developed in the same way as those presented in Figure 3-1....................................................................................................................... 3-3

Figure 3-3. Monthly estimated average concentration (#/1,000 m3) of northern anchovy (Engraulis

mordax) larvae collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b). ......................................................................................................................... 3-4

Figure 3-4. Monthly estimated average concentration (#/1,000 m3) of white croaker (Genyonemus

lineatus) larvae collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b). ......................................................................................................................... 3-5

Figure 3-5. Monthly estimated average concentration (#/1,000 m3) of the KGB rockfish larval complex collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b). .............................................................................................................................................. 3-5

Figure 3-6. Monthly estimated average concentration (#/1,000 m3) of blue rockfish larva collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b). ............... 3-6

Figure 4-1 The areal extent of the monthly source water volume (VSi) in April 2011 for a) northern anchovy and b) white croaker. The VSi for each species for April has been superimposed on the total source water body extent to show the remaining area not incorporated into the source water volume for the month of April for these taxa. ................................................................................................. 4-4

1.0: Introduction

ESLO2011-040.3

DeepWater Desal Preliminary Intake Impact Assessment Modeling 1-1

1.0 Introduction

This report presents the results of a preliminary modeling effort to assess the potential for impacts to marine organisms resulting from the intake of seawater by an ocean water desalination plant off Moss Landing, California that is being proposed by DeepWater Desal (DWD) LLC. The potential impacts from the intake will largely be confined to the entrainment of small planktonic organisms including the eggs and larvae of fishes and invertebrates into the system. Impingement of larger organisms on the screens at the opening to the intake is not anticipated to be a problem as the intake will be designed to ensure a velocity of less than 0.5 feet per second (fps), which is the standard used for compliance with state and federal policy for power plant ocean intakes. The potential for impacts to fishes and invertebrates due to entrainment at the proposed intake location will be evaluated using the Empirical Transport Model (ETM) a modeling approach that has been used on similar ocean intake projects and is the standard approach in California for assessing impacts due to power plant and desalination plant ocean intakes (Steinbeck et al 2007).

This preliminary modeling effort evaluates the potential effects of operating a 122 cm (48 in.) diameter intake line at a depth of approximately 18 m (60 ft) offshore to the northwest of Moss Landing Harbor in Monterey Bay, California (Figure 1-1). The location of the intake line currently has a 91 cm (36 in.) diameter pipe that was previously used for offloading fuel oil from tankers at a marine terminal to the Moss Landing Power Plant. This pipe will be removed and replaced with the new 122 cm (48 in.) diameter line. For the purposes of this analysis, a daily intake volume of 94,640 m3 (25,000,000 gal) was used in the modeling, although the final intake volume may be less.

The assessment in this report uses a strictly modeling approach using the ETM to estimate the potential for impacts to fish and invertebrates due to entrainment by the intake. The potential for using a strictly modeling approach for intake assessment has been demonstrated in the results of previous studies at locations where the intake is located along the open coast in an area with relatively homogeneous habitat, such as the study at the Huntington Beach Generating Station (MBC and Tenera 2005). The basis of the ETM is an estimate of the daily mortality resulting from entrainment which is typically calculated as the number of larvae entrained proportional to the estimated number at risk in the sampled source water. If the concentrations of larvae for a specific taxon are relatively uniform across the sampled source water body then the assumption can be made that the estimated proportional daily mortality is the ratio of the volume of water entrained to the volume of the sampled source water. This simplifying assumption was used in the original formulation of the ETM which was used to estimate impacts due to an intake along a river (Boreman et al. 1978, Boreman et al. 1981). Although a river is a much simpler system to model because of the generally unidirectional flow of water, the volumetric assumption that larvae are uniformly distributed throughout the source water does not compromise the empirically derived calculation of the source water population extent. Instead it allows for the

1.0: Introduction

ESLO2011-040.3


calculation of proportional mortality without needing to sample additional source water body sites.

When the volumetric ratio is used in the ETM as the estimate of daily mortality, the only biological data necessary for the model other than the list of taxa present at the entrainment site, are the estimates of larval duration for each taxa likely to be subject to entrainment, and the seasonal variation in larval abundance (presence/absence) for each taxa. These parameters affect the size of the source water body, and the period over which a taxon is subject to entrainment. The selection of taxa for analysis in this report was based on the results from an earlier study at the Moss Landing Power Plant in 2000 (Tenera 2000a) that included sampling in the nearshore areas outside of Moss Landing Harbor, not far from the proposed intake location. The estimates of larval duration for these taxa were derived from data collected from recent studies along the central coast of California including the studies at Moss Landing. The source water for the modeling was estimated using data on ocean currents available through the Central & Northern California Ocean Observing System (CeNCOOS) using the network of instruments deployed by the State of California's Coastal Ocean Currents Monitoring Program (COCMP).

This report presents the methods and data sources used in the assessment in Section 2.0. This includes descriptions of the ETM, summaries of the study and data collected for the Moss Landing Power Plant, and the data used in determining the larval durations used in the modeling. The methods for estimating the source water areas and volumes for the modeling are also presented in Section 2.0. The results of the modeling are presented in Section 3.0 and summarized in Section 4.0.

2.0: Modeling and Data Methods

ESLO2011-040.3


Figure 1-1. Map showing location of terminus of the fuel line previously used to supply fuel oil to the Moss Landing Power Plant.

Fuel Line


ESLO2011-040.3


2.0 Model and Data Methods

This section includes descriptions of the Empirical Transport Model (ETM) used in assessing the effects of the intake and the data used in the modeling. The biological data includes data from studies for the Moss Landing Power Plant (Tenera 2000a) used in selecting the fishes used in the assessment, data on the seasonal abundances used in estimating weights for the ETM calculations, and data on larval length and growth used in estimating larval durations for the fishes which were taken from the Moss Landing studies and a study at the Diablo Canyon Power Plant (DCPP) during 1996–1999 (Tenera 2000b). The data and methods used to estimate the source water for the ETM are also presented.

2.1 Empirical Transport Model (ETM)

The ETM was proposed by the U.S. Fish and Wildlife Service to estimate mortality rates resulting from water withdrawals by power plants (Boreman et al. 1978, and subsequently in Boreman et al. 1981). The ETM provides an estimate of incremental mortality (a conditional estimate of entrainment mortality in absence of other mortality, Ricker 1975) based on estimates of the proportional loss to the source water population represented by entrainment. The conditional mortality is represented as estimates of proportional entrainment (PE) that are calculated for each survey and then expanded to predict regional effects on populations using the ETM, as described below. Variations of this model have been discussed in MacCall et al. (1983) and have been used to assess impacts in the previous studies at California power plants (MacCall et al. 1983, Parker and DeMartini 1989, Tenera 2000a, Tenera 2000b, Steinbeck et al. 2007).

The estimate of proportional entrainment (PE) is the central feature of the ETM and is usually calculated for each taxon1 for each survey (i) as the ratio of the estimated numbers of larvae entrained per day to the larval population estimates for the source water (usually referred to as the sampled source water) as follows:

,ii i

i ii

EE E

i

S SS

VNPE

N V

(1)

where for each taxon,iEN and

iSN are the estimated numbers of larvae entrained (E) and in the

sampled source water (S) on any given day during survey period i, iE and

iS are the average

concentrations of larvae of a taxon from the intake location and the sampled source water population, respectively, for which the ratio will remain constant on any given day during survey period i, and

iEV and iSV are the estimated volumes of the entrained intake water per day (subject

to the operational flow rate of the intake) and the predicted source water extent respectively in 1 Taxon is used to refer to single species or group of closely related species. Taxa is the plural of taxon.


ESLO2011-040.3


survey period i. The latter is empirically derived from back-projections of adjusted CODAR water currents and is explained in a later section of this report. As is clear from Equation 1, if the concentrations of larvae of taxa are approximately equal in the intake and source water volumes then those two terms cancel each other out and the PE is reduced to the ratio of the two volumes for each survey period i as follows:

.i

i

E

i

S

VPE

V (2)

The daily volume of the intake used in the modeling was 94,640 m3 (25,000,000 gal) which was based on an intake flow rate of 65.72 m3 (~17,360 gal) per minute. While a reasonably accurate estimate of the volume of the intake flow can be obtained, estimating the extent of the entire source water for the taxon being evaluated (called the source water body) is more difficult and will vary depending upon oceanographic conditions (mainly water currents) and the period of time that the taxon being analyzed is in the plankton and exposed to entrainment. The volume of the source water was estimated separately for each taxon for each month or survey period i using data on ocean currents available through the Central & Northern California Ocean Observing System (CeNCOOS) consortium of the Coastal Ocean Currents Monitoring Program (COCMP). Data on surface currents over the entire Monterey Bay and surrounding coastline from CeNCOOS CODAR stations were adjusted to midwater column speeds using data from a current meter located just offshore from the intake that is also maintained by CeNCOOS. The methodology used in calculating the source water is provided in more detail in Section 2.3.

The taxa of fishes used in the modeling were selected based on data collected from studies for the Moss Landing Power Plant in 2000 (Tenera 2000a). The sampling included collections of fish and invertebrate larvae at two stations outside of Moss Landing Harbor in Monterey Bay and at a location between the breakwaters at the harbor entrance (Figure 2-1). Data were only collected from these three stations for nine of the months during the one year study. The larval durations used in the source water estimates were calculated from data collected during the Moss Landing study and from studies conducted at the Diablo Canyon Power Plant (Tenera 2000b).

In order to derive an estimate of the proportion of the source water population at risk from entrainment by the intake for a given taxon the estimate of daily mortality rate (PE) is compounded over the number of days the larvae are potentially exposed to entrainment (d). This duration is determined by the maximum sampled age range2 of all the larvae for that taxon. While a separate PE estimate was calculated for each survey period (i), the larval duration was derived for each taxon for all sampling periods. Although this averages any potential variation in age demographic that may occur in source water population from period to period, it generally provides a more accurate estimate of the duration of potential entrainment for the larva in the

2 Duration is calculated using published growth rate estimates applied to sampled larval length. The durations is the age range in the sampled population (oldest minus youngest). Further details are provided in Section 3.1 of this report.


ESLO2011-040.3


source water population, particularly for the less abundant taxa sampled. Although the estimated larval duration remains consistent throughout the year, the changes in ocean currents results in different source water estimates for each month. Different taxa of fishes are present during different months of the year and to differing degrees within those months (some months demonstrate consistently higher abundances than others), so the total annual estimate of proportional mortality (PM) due to entrainment would only include the data from the months when those taxa are present and are weighted by the expected abundance of the taxa during those months. These weights were calculated using data from independent studies where sampling was done over at least a period of one year. The annual estimate of PM for a given taxa is calculated as follows:

12

1

1 (1 ) ,d

M i i

i

P f PE

(3)

where fi = the fraction of the source water population from the year present during month or survey period i, and d = period of exposure in days that the larvae are exposed to entrainment mortality represented by the PEi, the period of exposure in days that the larvae are exposed to entrainment mortality (d) is taxon specific and is calculated based on the difference between the youngest and oldest larvae sampled at the entrainment location.

Assumptions associated with the estimation of PM include the following:

Each survey period represents a new and independent cohort of larvae;

The estimates of larval abundance used for weighting the monthly estimates (fi) are representative of long-term conditions within Monterey Bay;

The conditional probability of entrainment, PEi, is constant within each monthly survey period (i);

The conditional probability of entrainment, PEi, is constant within each of the size classes of larvae present during each monthly period (i);

Lengths and applied growth rates of larvae accurately estimate taxon specific period of larval duration subject to entrainment (d).


ESLO2011-040.3


Figure 2-1. Location of stations sampled during the MLPP 316b study.

Source Water Sampling Entrainment Sampling

Sandholdt Pier

Units 6-7 Discharge

Elkhorn Slough

0 0.5 km

1 2 3 4 5

6

7

Moss Landing Power Plant

Units 6-7 Intake

Hwy 1 Bridge

Moss Landing Harbor

Moss Landing Harbor and Area of Detail

Monterey Bay

Kirby Park

Dairies

1 km

RetiredUnits 1-5

Discharge

Combined-Cycle Units Intake(formerly Units 1-5 Intake)

Ocean

South

Ocean

North

Harbor

Mouth

Harbor

Bridge


ESLO2011-040.3


2.2 Biological Data Used in Modeling

The following section describes the biological data used in the ETM modeling assessment.

2.2.1 Sampling Methods

Plankton sampling for the MLPP 316(b) study was conducted at a station in front of each intake and at six additional stations (two locations in Elkhorn Slough, one near the harbor bridge, one at the harbor mouth, and two outside of the harbor complex in the offshore area) (Figure 2-1). Of these six stations three have been used in this assessment due to their proximity to the proposed intake location. The stations used are the harbor mouth (HM), and stations north (N1) and south (S1) of the harbor (Figure 2-2). The sampling at theses stations was only done monthly from September 1999 through May 2000. The sampling was done using a bongo frame with two 0.71 m (2.3 ft) diameter openings that were each equipped with 335 µm mesh plankton nets and codends, and a calibrated flowmeter. The bongo nets were lowered as close to the bottom as possible, and once at the correct depth, the boat was moved forward and the nets retrieved at an oblique angle (winch cable at about a 45°angle). The winch retrieval speed was constant at approximately 1 ft/sec. Samples were collected at these stations once per month during daylight hours with one sample being collected near low tide and one near high tide. Table 2-1 presents a description, depth, and location of these three stations. The target volume for each sample was 40 m3.

Upon successful completion of a tow, the nets were retrieved from the water and all of the collected material was rinsed into the cod-end. The contents of both nets were combined into a single, labeled jar (constituting one sample) immediately after collection and were preserved in 70 percent ethanol. Each sample was tagged with an internal and external label containing the location, date, time, and station depth. In addition, that information was logged onto a sequentially numbered data sheet. The sample’s unique identifier was used to track it through laboratory processing, data analyses, and reporting.

In the laboratory all larval fishes were removed from each sample and placed in labeled vials containing 70 percent ethanol. Fish eggs were not removed from the samples. Although there are descriptions of many marine eggs, the taxonomy remains difficult and time consuming, with many of the eggs not being able to be identified to the species level and being placed in lump categories which could be made up of many different species from possibly different genera. The identity and life stage of each larval fish was recorded on a data sheet for each sample. A laboratory quality control (QC) program for all levels of laboratory sorting and taxonomic identification was applied to all samples.


ESLO2011-040.3


Table 2-1. Collection specifications for source water sampling at MLPP.

Station Name Description Location

(Lat. / Long.)

Station Depth at MLLW (m / ft)

Ocean North One mile north of ML harbor mouth, at the 20-meter depth contour.

36o 48.84' N / 121o 48.40' W

20 m / 66 ft

Ocean South One mile south of ML harbor mouth, at the 20-meter depth contour.

36o 47.44' N / 121o 48.52' W

20 m / 66 ft

Harbor Mouth Entrance to Moss Landing Harbor from Monterey Bay; between the north and south breakwaters.

36o 48.38' N / 121o 47.40' W

7 m / 23 ft

2.2.2 Taxa Selected for Analysis

The taxa that are analyzed in this assessment include white croaker, rockfishes, and northern anchovy which all occurred in the nearshore sampling conducted at MLPP and were all abundant in the samples collected at the three stations in the vicinity of the proposed intake location. Although CIQ goby complex3 larvae were the most abundant larvae collected at the three stations (Table 2-2), the primary adult habitat for CIQ gobies is inside the Moss Landing harbor and Elkhorn Slough. Any impacts to the population of CIQ gobies would only occur to larvae transported out of these areas during low tides, which have a low likelihood of being returned to their native habitat inside the harbor/slough complex. Similarly, lanternfishes, which were the second most abundant larvae collected primarily occur as adults in deeper water and their larvae were potentially only collected due to transport into shallow, nearshore areas. On the assumption that these larvae have been advected outside of their natal habitat and therefore will not survive to recruit to the adult population these two groups of taxa were not included in this preliminary assessment.

2.2.3 Larval Durations

The previous analysis of data for Moss Landing (Tenera 2000a) was focused on fishes associated with the harbor/slough complex so there were no data available on the lengths of the larvae for rockfishes, northern anchovy, and white croaker. The larval durations for these three taxa were derived from data collected off Diablo Canyon Power Plant (DCPP) during 1996–1999 when high number of larvae of these two taxa were collected and measured (Tenera 2000b). The DCPP data was collected using similar methods to that used for the sample collections at the three stations used in the MLPP analysis.

3 CIQ goby complex refers to a taxonomic grouping of gobies that are extremely difficult to differentiate into separate species when the larvae are at a very young age. The acronym CIQ refers to the three species, Clevelandia

ios, Ilypnus gilberti, and Quietula y-cauda.


ESLO2011-040.3


Table 2-2. Average concentrations and number collected of fish taxa at three stations (N1, S1 and Harbor Mouth) during daytime high and low tide sampling from September 1999 through May 2000 for Moss Landing Power Plant (Tenera 2000a).

Taxon Common Name

Average

Concentration

(# per m3)

Sample

Count

CIQ goby complex gobies 0.23867 1,405

Myctophidae lanternfishes 0.05494 607

Genyonemus lineatus white croaker 0.03578 329

Lepidogobius lepidus bay goby 0.01445 98

Sebastes spp. rockfishes 0.01316 151

Engraulis mordax northern anchovy 0.01022 100

Leptocottus armatus Pacific staghorn sculpin 0.00878 66

Sebastolobus spp. thornyheads 0.00609 62

Pleuronectidae unid. flounders 0.00428 33

Gillichthys mirabilis longjaw mudsucker 0.00321 20

Osmeridae unid. smelts 0.00283 16

Clupea pallasii Pacific herring 0.00279 16

Ammodytes hexapterus Pacific sand lance 0.00218 24

Hypsoblennius spp. blennies 0.00195 17

Atherinidae unid. silversides 0.00192 13

Coryphopterus nicholsi blackeye goby 0.00156 9

Cottidae unid. sculpins 0.00151 11

Pleuronectiformes unid. flatfishes 0.00142 14

Citharichthys spp. sanddab 0.00102 11

larval/post-larval fish, unid. unidentified larval fishes 0.00075 6

Parophrys vetulus English sole 0.00070 6

Cottus asper prickly sculpin 0.00064 5

Sardinops sagax Pacific sardine 0.00058 6

Artedius spp. sculpins 0.00039 2

Platichthys stellatus starry flounder 0.00036 2

Bathylagus ochotensis popeye blacksmelt 0.00024 2

Cebidichthys violaceus monkeyface eel 0.00022 3

Psettichthys melanostictus sand sole 0.00020 2

Paralichthyidae unid. lefteye flounders & sanddabs 0.00018 2

Clupeiformes herrings and anchovies 0.00016 2

Brosmophycis marginata red brotula 0.00009 1

Pleuronichthys verticalis honeyhead turbot 0.00009 1

Typhlogobius californiensis blind goby 0.00009 1

Zaniolepis spp. combfishes 0.00009 1

Bathymasteridae unid. ronquils 0.00008 1

Agonidae unid. poachers 0.00007 1

Cololabis saira Pacific saury 0.00006 1

Totals 0.41175 3,047


ESLO2011-040.3


2.3 MLPP Source Water Body Calculations

The following section describes the data used, and assumptions applied, in determining the source water used in this preliminary impact assessment for an intake line which is at a depth of approximately 18 m (60 ft) about 1 km (0.6 mi) to the north of the Moss Landing Harbor mouth (Figure 2-2).

2.3.1 Data Sources and Processing

Data on currents in the vicinity of the intake location were collected from two sources: nearshore sub-surface currents were obtained from an acoustic Doppler current profiler (ADCP) deployed at the Monterey Bay Aquarium Research Institute (MBARI) M0 mooring (Figure 2-2) and surface currents were obtained from a network of CODAR Ocean Sensors, Ltd. SeaSonde® high-frequency (HF) radars deployed by COCMP (Figure 2-3). All of the data were provided by CeNCOOS. A combination of these velocity measurements was used to project the extent of water that could be transported to the intake location over selected planktonic larval duration periods.

a)

b)

Figure 2-2. Locations of a) M0 current meter in relation to plankton sampling locations (N1, S1 and HM) and the intake location, and b) close up of plankton sampling locations and the two proposed DWD intakes in relation to nearshore subtidal bathymetry. A potential location for a deepwater intake is also shown.


ESLO2011-040.3


Figure 2-3. Ocean surface current vectors measured on October 1, 2010 at 0000 UTC in the Monterey Bay, California region by the CeNCOOS CODAR SeaSonde stations (black triangles). Shown are vectors of both the 6 km (3.7 mile) resolution coverage offshore (left) and the higher 2 km (1.2 mile) resolution coverage closer to the coast, shaded according to their velocity per the color-bar (right).

The M0 ADCP data were collected for 140 seconds every 10 minutes from June 14, 2010 to September 30, 2011 in 4 m (13 ft) bins, with the center of the first bin located at the 6 m (20 ft) depth. These ADCP data were averaged across the hour to compliment the hourly frequency of the CODAR measurements. Means were then calculated from the 4–20 m (13–66 ft) ADCP bins to derive averages that approximated the depth of the water at the proposed intake location. The progressive current vectors from the M0 ADCP for the 6 and 18 m (20 and 59 ft) depth bins both show similar seasonal changes with predominantly upcoast flow from late spring through fall and downcoast and onshore flow during winter and early spring. As would be expected, the greater current speeds at the shallower depth result in greater onshore flow during the winter and spring months.


ESLO2011-040.3


The velocity of ocean currents measured at the water’s surface typically decays with increasing depth and this relationship was seen in the velocities measured. Due to their offshore and surface origin, CODAR speeds interpolated to the location of the M0 mooring were about twice the magnitude of the averages measured there at mid-depths by the ADCP. To better model the extent of waters potentially entrained at the intake location, respective of larvae living sub-surface, the CODAR-derived surface currents were scaled to approximate sub-surface magnitudes.

The proximity of the M0 mooring to the CODAR measurement field allowed the surface current values measured over the aforementioned time period to be linearly interpolated to the M0 location. The U (east-west) and V (north-south) components of the CODAR and ADCP velocities were considered separately in their relationship with depth. Further, as there are seasonal variations in the currents, each calendar month was assessed independently.

The difference between the CODAR and ADCP, as a percentage of the magnitude of the CODAR measurement, was calculated. Absolute values of each component measured hourly in the same calendar month by CODAR were subtracted from the absolute values of the corresponding average ADCP component for the 4–20 m (13–66 ft) depth range. The mean of these differences for the month was then divided by the mean of the absolute value of the CODAR component measured that month. This produced a percentage by which to scale the CODAR data to the magnitudes of the sub-surface currents. Application of these scaling factors to adjust the CODAR data did not affect the directional component of velocity (Figure 2-4).

Figure 2-4. The a) U and b) V components of velocity measured over a representative period (approximately two days) at the surface by CODAR and at depth by the M0 ADCP.

2.3.2 CODAR Back-Projections

A computer model was developed in MATLAB® with forcing from the combined CODAR and M0 ADCP measurements to reverse-track (back-projections) source water flowing to the intake location (36.81203° N, 121.80011° W) for durations of up through 46 days (maximum estimated d). There were 30 back projections calculated for each month from October 2010 to September 2011 using randomly selected hours within ± 1 day of the first day of each month as the starting

a) b)


ESLO2011-040.3


time. The 46 day time period allowed assessment for a range of larval planktonic durations exhibited by the most prevalent larval fish taxa found during sampling conducted at the three stations sampled in 1999-2000 (see Section 2.2). The data used in the back projections were the 6 km (offshore) and 2 km (nearshore) resolution surface currents from CODAR averaged using the method described above over the 4–20 m depth range and scaled to the hourly 12 m (39 ft) averages measured at M0. The arial extent of this adjusted CODAR data extended approximately 150+ km (93 mi) offshore and alongshore from the intake location. This arbitrary extent ensured the modeled area encompassed the maximal extent a particle was expected to be back-tracked to according to an estimation of current velocity and duration.

The velocity components of the currents (U, positive to east and V, positive to north) were calculated for each of the 9,217 hours from August 15, 2010 [(October 1, 2010 -1 day) – 46 days] through September 2, 2011 [(September 1, 2011) + 1 day] and collated into files each representing an hour of measurements. For each survey date, the scaled U and V components of the ocean current velocity measured that hour were first linearly interpolated to the location of the given intake. The sign of the U and V components were then reversed to calculate the location a particle (or presumably planktonic individual) would have originated from the hour before and been carried by the ocean currents toward the intake. This process was repeated for each prior hour from the survey date, through 46 previous days, interpolating the U and V components of velocity at each hour to the location calculated in the prior time-step and reversing sign to back-project the location the particle would have been the hour before.

If the back-projection of a particle caused its track to cross a land boundary, the distance the particle was projected to travel was applied first to the direction in U. If land was still encountered the distance was then applied to the V direction. If both attempts to move the particle alongshore failed, it was held in position for that time-step and the process repeated the next hour, until the current moved the particle past or away from the land mass. The result of the combined analysis of CODAR and the M0 ADCP, for 10, 20, and 30 days’ duration back-projections, are shown in Figures 2-5 to 2-7 based on each survey beginning on the first day of each of the months. Although the back-projections in Figures 2-5 to 2-7 are shown for periods of 10, 20, and 30 days the coastal distance corresponding to the maximum upcoast and downcoast extent of the 30 projections for the larval duration for each taxon will be used as the source water in the impact assessment based on that taxa’s calculated larval duration.

These figures show that the 30 day monthly back-projections from the intake location generally stay within Monterey Bay. But, each month is unique with wide variation in the distance that could be traveled in a 30 day period. Based on these back-projections, some months had little water movement (e.g., March 1, 2011 [Figure 2-6b]) while others had water traveling over longer distance (e.g., August 1, 2011 [Figure 2-7c]). For instance, for March, the excursion over the prior 30 days all stay very close to the proposed intake location, yet for April (Figure 2-6c), many of the projections for the previous 10 days (blue in Figure 2-6) show that water at the intake came either from near the City of Monterey or just close to the intake, and during an additional 10 previous days the water had come from either central Monterey Bay or just upcoast


ESLO2011-040.3


of the intake. The water from prior days 21-30 had moved from either central Monterey Bay or along the coast line from north of the intake to about Santa Cruz.


ESLO2011-040.3


a)

b)

c)

d)

Figure 2-5. CODAR back-projections scaled to ADCP data from buoy M0 and averaged over the 4-20 m (13–60 ft) depth range for dates ending on a) October 1, b) November 1, c) December 1, 2010, and d) January 1, 2011. The back projections use 30 randomly selected start times on the hour ± 1 day. Each back-projection changes color from blue to green to red to represent the time periods of 0–10 d, 11–20 d, and 21–30 d, respectively, for each projection.


ESLO2011-040.3


a)

b)

c)

d)

Figure 2-6. CODAR back-projections scaled to ADCP data from buoy M0 and averaged over the 4-20 m (13-60 ft) depth range for dates ending on a) February 1, b) March 1, c) April 1, and d) May 1, 2011. The back projections use 30 randomly selected start times on the hour ± 1 day. Each back-projection changes color from blue to green to red to represent the time periods of 0–10 d, 11–20 d, and 21–30 d, respectively, for each projection.


ESLO2011-040.3


a)

b)

c)

d)

Figure 2-7. CODAR back-projections scaled to ADCP data from buoy M0 and averaged over the 4-20 m (13-60 ft) depth range for dates ending on a) June 1, b) July 1, c) August 1, and d) September 1, 2011. The back projections use 30 randomly selected start times on the hour ± 1 day. Each back-projection changes color from blue to green to red to represent the time periods of 0–10 d, 11–20 d, and 21–30 d, respectively, for each projection.


ESLO2011-040.3


2.3.3 Kernel Density Estimates of Source Area and Volume

In order to determine the extent of the source water body for each taxon, a two-dimensional kernel density estimation method was used. The final stage in the data analysis was done using the R statistics software function ‘kde2d’ in the Mass package. Initially a total source water body extent (source water extent) was plotted on a spatial grid for each taxon. From this, a source water volume (VSi in equation (1) in Section 2.1) based on area and depth, corresponding to each sampling date for each taxon was calculated. The final surface area for the source water was based on the ‘kde2d’ function removing the lower 5% density estimates. The following section describes the method and assumptions used in calculating VSi for this study.

2.3.3.1 Total Source Water Body

A 260 by 200 cell grid was established based on selected ranges of latitude and longitude for Monterey Bay: 36.5 to 37.0N and 122.1 to 121.7W. For each taxon, monthly CODAR back projections (consisting of 30 CODAR back projections each month as described in Section

2.3.3) were overlaid on this grid. The period of months over which back projections are compiled varies according to the seasonal abundance patterns of the larval fish. Back-projections for five months from February-June, 2011 were used for northern anchovy (i.e. 5 months of 30 back projections per month is a total of 150 CODAR back projections). Back-projections from six months from February-July 2011 were used for the kelp-gopher-black and yellow (KGB) species complex, while the back-projections from eight months from January-August 2011 were used for blue rockfish. Back-projections from six months from January-June 2011 were used for white croaker.

Once compiled for all of the months or survey periods, the total number of discrete hours a back projection point occurred within each cell was derived and an estimated proportional frequency of occurrence (‘proportional occurrence’) for each cell in the grid was produced. This figure is the frequency of occurrence in a given cell as a proportion of the total possible occurrences across the grid. For example for northern anchovies, 150 CODAR back projections at 46 days per back projection is equivalent to 165,600 hours or total possible occurrences across the grid.

The total source water body extent was limited by two additional assumptions. Although most planktonic fish eggs and larvae occur in the upper 50 m (164 ft) of the water column (Moser and Watson 2006), the source water body extent was also restricted based on known potential depth limits for egg and larvae by taxa. KGB rockfish are found to approximately 45 m (148 ft) and blue rockfish to 90 m (295 ft) bottom depths. For white croaker a bathymetric depth limit of 330 m (1083 ft) was used, while northern anchovy extent was not restricted by bathymetry. Secondly, cells with a proportional occurrence less than 0.05 were removed from the potential source water body extent. The source water body extent for each taxon is show in Figures 2-8 to 2-11. As shown in the source water estimate for northern anchovy (Figure 2-8), white croaker (Figure 2-

9), and blue rockfish (Figure 2-11), the source water areas may not always be contiguous with the area around the intake. This can occur if several back projections follow different tracks to the same source water area.


ESLO2011-040.3


2.3.3.2 Source Water Volume

The source water volume (VSi) for each sample date (i) for each taxon was determined by summing the volumes of all of the cells within the total source water body extent from the kernel density analysis within the northern and southern extents of the corresponding CODAR back projections for each individual sample date for each taxon. The depth of each cell was determined from the 5 m contour closest to the cell’s center. For northern anchovy, cell depths greater than 300 m (984 ft) were restricted to 300 m.

Therefore, the source water volume (VSi) varies by taxa due to;

Differing larval durations (d); and

The variation in the back projections over those durations..

Source water bodies vary by date as a result of;

Changes in the CODAR back-projections for each sample period.

The VSi for each taxon by sample date is shown in Table 2-3 to 2-6.


ESLO2011-040.3


Figure 2-8. Total source water body extent for northern anchovy eggs and larvae in Monterey Bay based on kernel density estimation of 46-day back-projections for the five months of February to June 2011. The 300 m depth contour is indicated offshore.

End of Period

Oct 1 2010

Nov 1 2010

Dec 1 2010

Jan 1 2011

Feb 1 2011

Mar 1 2011

Apr 1 2011

May 1 2011

Jun 1 2011

Jul 1 2011

Aug 1 2011

Sep 1 2011

Upcoast (km) 36.412 7.053 23.964 9.819 35.27 3.035 26.309 34.816 27.138 39.389 36.424 0.329

Downcoast (km)

34.778 36.268 44.363 15.246 70.079 7.9 26.881 34.985 8.633 34.837 43.179 32.301

Source Water Area (km2)

90.043 60.197 110.670 54.510 98.018 28.332 108.684 92.399 77.055 89.202 98.018 44.079

VSi (km3) 3.879 3.5647 4.1835 2.9925 4.0735 1.0794 4.1736 3.9251 1.7216 3.8862 4.0735 3.307

Table 2-3. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 46 days for each corresponding sample month for northern anchovy. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for the taxon (also shown).

Total Source Water Body Extent

Coastal Land

Offshore

300 m Bathymetry


ESLO2011-040.3


Figure 2-9. Total source water body extent for white croaker eggs and larvae in Monterey Bay based on kernel density estimation of 17.23-day back-projections for the six months of January to June 2011. The 300 m depth contour is indicated offshore.

End of Period Oct 1 2010

Nov 1 2010

Dec 1 2010

Jan 1 2011

Feb 1 2011

Mar 1 2011

Apr 1 2011

May 1 2011

Jun 1 2011

Jul 1 2011

Aug 1 2011

Sep 1 2011

Upcoast (km) 10.111 0.796 8.627 9.819 2.603 1.754 2.412 19.371 18.179 39.389 0.564 0.329

Downcoast (km) 4.959 25.796 0.718 15.217 6.661 7.9 26.533 1.84 6.582 34.54 39.523 17.765


32.370 41.354 17.834 54.746 23.588 24.160 43.676 37.720 51.381 70.998 40.782 38.191

VSi (km3) 0.7938 1.387 0.2441 1.4008 0.7221 0.733 1.4195 0.5619 1.0234 1.7188 1.3787 1.2484

Table 2-4. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 17.23 days for each corresponding sample month for white croaker. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for the taxon (also shown).


Coastal Land

Offshore

300 m Bathymetry


ESLO2011-040.3


Figure 2-10. Total source water body extent for KGB rockfish complex eggs and larvae in Monterey Bay based on kernel density estimation of 7.95-day back-projections for the six months of February to July 2011. The 45 m depth contour is indicated offshore.

End of Period

Oct 1 2010

Nov 1 2010

Dec 1 2010

Jan 1 2011

Feb 1 2011

Mar 1 2011

Apr 1 2011

May 1 2011

Jun 1 2011

Jul 1 2011

Aug 1 2011

Sep 1 2011

Upcoast (km)

4.012 0.796 4.75 9.819 0.822 1.638 1.32 18.733 10.785 8.361 0.564 0.329

Downcoast (km)

3.708 7.783 0.089 11.637 6.661 2.238 11.505 1.703 4.829 8.041 13.446 4.736

Source Water Area

(km2) 13.661 19.146 7.672 32.067 16.824 6.393 20.088 26.818 25.068 29.510 18.944 10.128

VSi (km3) 0.227 0.376 0.0944 0.5212 0.3292 0.1226 0.3964 0.3077 0.3703 0.4882 0.3799 0.2086

Table 2-5. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 7.95 days for each corresponding sample month for the KGB rockfish complex. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for that taxon (also shown).


Coastal Land

Offshore

300 m Bathymetry


ESLO2011-040.3


Figure 2-11. Total source water body extent for blue rockfish eggs and larvae in Monterey Bay based on kernel density estimation of 7.95 day back-projections for the eight months of January to August 2011. The 90 m depth contour is indicated offshore.

End of Period Oct 1 2010

Nov 1 2010

Dec 1 2010

Jan 1 2011

Feb 1 2011

Mar 1 2011

Apr 1 2011

May 1 2011

Jun 1 2011

Jul 1 2011

Aug 1 2011

Sep 1 2011

Upcoast (km) 4.012 0.796 4.75 9.819 0.822 1.638 1.349 18.733 11.777 8.361 0.564 0.329

Downcoast (km) 3.789 7.783 0.446 11.637 6.661 3.128 21.966 1.79 4.847 8.041 19.246 4.736


16.858 22.544 10.902 44.214 19.516 9.758 34.490 28.870 30.654 35.903 33.379 12.214

VSi (km3) 0.3774 0.5495 0.1575 0.9119 0.4903 0.2524 1.055 0.407 0.5663 0.7184 1.0394 0.3464

Table 2-6. The distance in km upcoast and downcoast from the intake location of the maximum northerly and southerly extent of CODAR back-projections to 7.95 days for each corresponding sample month for blue rockfish. These extents are used to delimit the total source water body extent and derive the volume of the source water body (VSi) for that month for that taxon (also shown).


Coastal Land

Offshore

300 m Bathymetry

3.0: Impact Assessment

ESLO2011-040.3


3.0 Impact Assessment Analysis Results

This section presents the result of the impact assessment modeling using the Empirical Transport Model (ETM) and a daily entrainment mortality estimate (proportional entrainment [PE]) based on the volumetric ratio of the desalination plant to the estimated source water.

3.1 Larval Durations

The period of time that the larvae were exposed to entrainment was calculated by dividing the difference between the size at hatching and the size at the 99th percentile by a larval growth rate obtained from the literature. The duration of the planktonic egg stage was added to this value for white croaker and northern anchovy which both have a plankton egg stage.

Larval Duration = Egg Stage Duration + (99th Percentile Length-Hatch Length)/Growth Rate.

The larval growth rates of these four taxa were estimated as follows. Following the methodology used in past studies, a larval growth rate for white croaker was derived from available data on five species of Sciaenidae (croakers) that were raised in the laboratory by Southwest Fisheries Science Center staff (Moser 1996). These were the black croaker (Cheilotrema saturnum), corbina (Menticirrhus undulatus), spotfin croaker (Roncador stearnsii), queenfish (Seriphus

politus), and yellowfin croaker (Umbrina roncador), which all have larvae that are morphologically similar at small sizes (Moser 1996). Hatch and larval lengths at various number of days after birth presented in Moser (1996) were used to calculate an average daily growth rate from hatching through the flexion stage for Sciaenidae. The growth rate calculated from these data was 0.2480 mm/day (0.0098 in/d). This calculation corresponds well to a recent estimation by Miller et al. (2011) based on formalin-fixed white croaker larvae possibly subject to shrinkage of 0.242 mm/day (0.00953 in/d). The rockfish larval growth rate of 0.22 mm/d (0.01 in/d) was estimated from data for blue rockfish (Sebastes mystinus) presented in Yoklavich et al. (1996). This estimate was used for both blue and KGB rockfish larvae. The northern anchovy (Engraulis

mordax) egg hatches in two to four days, has a larval phase lasting approximately 70 days, and undergoes transformation into a juvenile at about 35–40 mm (1.4–1.6 in.) (Hart 1973, MBC 1987, Moser 1996). Data from Butler et al. (1993, Figure 4) was used to estimate an overall larval anchovy growth rate of 0.485 mm/day (0.019 in./day) by estimating the time spent in each 1 mm size bin from hatch size to the 99th percentile length using the reciprocal of the bins’ growth rates.

The 99th percentile value was used to eliminate outliers from the calculations. For all the taxa the size at hatching was estimated as follows using the data from the length distributions from the samples at Moss Landing for white croaker, and Diablo Canyon for rockfish and northern anchovy shown in Figures 3-1 and 3-2:

Hatch Length = (Median Length + 1st Percentile Length)/2.


ESLO2011-040.3


This calculated value of hatch length was used because of the large variation in smaller size larvae. The lack of highly skewed or knife edge distributions shows that hatch lengths are most likely quite variable.

Values underlying the estimation of hatch size and larval duration for both the MLPP and Diablo Canyon data appear in Table 3-1.

Table 3-1. Statistics of larval fish lengths from samples collected near Moss Landing (white croaker) and near Diablo Canyon Power Plant (rockfish and anchovy). Estimated larval durations are calculations using statistics and literature based growth rates. The estimate for rockfish was used for both blue and KGB rockfish larvae.

Taxa Group Number

Measured

Lower 1% Percentile

(mm)

Median Length (mm)

Estimated Hatch

Length (mm)

Upper 99% Percentile

(mm) Growth (mm/d)

Larval Duration (d)

white croaker 280 1.60 3.23 2.41 6.14 0.25 17.23

rockfish 13,180 3.00 4.10 3.55 5.30 0.22 7.95

northern anchovy 2,548 2.00 3.70 2.85 24.80 0.49 48.25


ESLO2011-040.3


Figure 3-1. Length frequency analysis for white croaker larvae collected from MLPP studies. Below the percentage frequency is a box plot representing the range of 98 percent of the data values with the mean shown as the small filled circle, and the median, and the 25% and 75% quartiles shown by vertical lines with the width height of the box indicating the percent of the data within the interval.

Figure 3-2. Length frequency analysis for a) northern anchovy and b) rockfish larvae collected from studies off Diablo Canyon Power Plant. The box plots were developed in the same way as those presented in Figure 3-1.

a) b)


ESLO2011-040.3


3.2 Larval Seasonality

The weights used in the ETM calculations were based on monthly concentration of northern anchovy, white croaker, and KGB and blue rockfish larvae collected at either MLPP or at DCPP, respectively (Figures 3-3 through 3-5). Northern anchovy larvae were present in at least low concentrations during most months of 1997 and 1998 during the studies at Diablo Canyon (Tenera 2000b) with the highest concentrations during the spring of 1998 (Figure 3-3). They were then almost totally absent during the spring of 1999. The concentration of larval white croaker varied both between months and years with the highest abundances occurring during March 1998 during the studies at DCPP (Tenera 2000b) (Figure 3-4). The larvae from each of the two larval rockfish complexes were generally collected during the same period of time but the maximum concentrations for KGB larvae (Figure 3-5) occurred slightly later in the year than blue complex larvae (Figure 3-6) (Tenera 2000b).

Figure 3-3. Monthly estimated average concentration (#/1,000 m3) of northern anchovy (Engraulis mordax) larvae collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b).

0

50

100

150

200

250

300

350

400

450

500

Jul

Au

g Se

p

Oct

N

ov

Dec

Ja

n

Feb

M

ar

Ap

r M

ay

Jun

Ju

l A

ug

Sep

O

ct

No

v D

ec

Jan

Fe

b

Mar

A

pr

May

Ju

n

Co

nce

ntr

atio

n (

#/1

,00

0 m

3)

Months (1997-1999)


ESLO2011-040.3


Figure 3-4. Monthly estimated average concentration (#/1,000 m3) of white croaker (Genyonemus lineatus) larvae collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b).

Figure 3-5. Monthly estimated average concentration (#/1,000 m3) of the KGB rockfish larval complex collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b).

0

50

100

150

200

250

Jul

Au

g Se

p

Oct

N

ov

Dec

Ja

n

Feb

M

ar

Ap

r M

ay

Jun

Ju

l A

ug

Sep

O

ct

No

v D

ec

Jan

Fe

b

Mar

A

pr

May

Ju

n

Co

nce

ntr

atio

n (

#/1

,00

0 m

3)

Months (1997-1999)

0

50

100

150

200

250

300

350

Jul

Au

g Se

p

Oct

N

ov

Dec

Ja

n

Feb

M

ar

Ap

r M

ay

Jun

Ju

l A

ug

Sep

O

ct

No

v D

ec

Jan

Fe

b

Mar

A

pr

May

Ju

n

Co

nce

ntr

atio

n (

#/1

,00

0 m

3)

Months (1997-1999)


ESLO2011-040.3


Figure 3-6. Monthly estimated average concentration (#/1,000 m3) of blue rockfish larva collected at the DCPP source water stations during the 1997-1999 sampling. Data from Tenera (2000b).

3.3 Impact Assessment Mortality Estimates

For all four fish taxa, larval mortality estimates were based on a weighted survival estimates using monthly larval densities from previous surveys as monthly weights. The daily intake volume at the proposed DWD facility used in the calculations was 94,640 m3 (25,000,000 gal or 17,361 GPM).

The results of the ETM modeling for northern anchovy eggs and larvae reflected the seasonal abundance of the larvae which were highest in late spring (Table 3-2). The weights (fi) for those months accounted for greater than 70 percent of the larvae estimated to be present during the year. During the June survey, which had a weight of almost 30%, the currents were reduced resulting in a lower source volume than most other months and a higher PE estimate than April when the larvae were also very abundant. This resulted in reduced survival for that month. The lowest survival was estimated for March, but only 2.8 percent of the larvae were estimated to be present during that month. The overall annual mortality resulting from the intake at the proposed DWD facility was estimated at 0.00168 or 0.168 percent.

0

20

40

60

80

100

120

140

160

180

Jul

Au

g Se

p

Oct

N

ov

Dec

Ja

n

Feb

M

ar

Ap

r M

ay

Jun

Ju

l A

ug

Sep

O

ct

No

v D

ec

Jan

Fe

b

Mar

A

pr

May

Ju

n

Co

nce

ntr

atio

n (

#/1

,00

0 m

3)

Months (1997-1999)


ESLO2011-040.3


Table 3-2. Mortality estimation (PM) for northern anchovy eggs and larvae at the intake location based on a planktonic duration of 48.3 d. Source water volumes calculated from kernel density estimates for back-projections from March–July 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)48.3 d. Survivals with weights (fi) of zero were not included in the calculation of PM.

Period

(2010 - 2011)

Upcoast (km)

Downcoast (km)

Source Volume (km3)

PEi Density

(#/1000 m3) Weight (fi) Survival

Sept 36.412 34.778 3.8790 2.440E-05 25.79 0.041876 0.99882

Oct 7.053 36.268 3.5647 2.655E-05 9.38 0.015231 0.99872

Nov 23.964 44.363 4.1835 2.262E-05 11.71 0.019011 0.99891

Dec 9.819 15.246 2.9925 3.163E-05 26.91 0.043690 0.99848

Jan 35.270 70.079 4.0735 2.323E-05 8.11 0.013167 0.99888

Feb 3.035 7.900 1.0794 8.768E-05 17.24 0.028001 0.99578

Mar 26.309 26.881 4.1736 2.268E-05 221.75 0.360088 0.99891

Apr 34.816 34.985 3.9251 2.411E-05 47.94 0.077853 0.99884

May 27.138 8.633 1.7216 5.497E-05 180.32 0.292819 0.99735

June 39.389 34.837 3.8862 2.435E-05 25.66 0.041664 0.99883

July 36.424 43.179 4.0735 2.323E-05 15.62 0.025357 0.99888

Aug 0.329 32.301 3.3070 2.862E-05 25.40 0.041242 0.99862

Weighted Mean Survival (S) 0.99823

PM = 1-S 0.00168


ESLO2011-040.3


The results of the ETM modeling for white croaker eggs and larvae reflected the seasonal abundance of the larvae which were highest in late spring (Table 3-3). The weights (fi) for those months accounted for greater than 70 percent of the larvae estimated to be present during the year. During the April survey, which had a weight of over 60%, the strong currents resulted in a larger source volume than most other months, a lower PE estimate, and increased survival relative to most other months. The overall annual mortality resulting from the intake at the proposed DWD facility was estimated at 0.00154 or 0.154 percent.

Table 3-3. Mortality estimation (PM) for white croaker eggs and larvae at the intake location based on a planktonic duration of 17.2 d. Source water volumes calculated from kernel density estimates for back-projections from January–June 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)17.2 d. Survivals with weights (fi) of zero were not included in the calculation of PM.

Period

(2010 - 2011)

Upcoast (km)

Downcoast (km)

Source Volume (km3)

PEi Density


Sept 10.111 4.959 0.7938 1.192E-04 0.39 0.002331 0.99795

Oct 0.796 25.796 1.3870 6.823E-05 0.00 0.000000 0.99882

Nov 8.627 0.718 0.2441 3.877E-04 0.05 0.000269 0.99334

Dec 9.819 15.217 1.4008 6.756E-05 5.27 0.031111 0.99884

Jan 2.603 6.661 0.7221 1.311E-04 33.41 0.197343 0.99774

Feb 1.754 7.900 0.7330 1.291E-04 10.95 0.064647 0.99778

Mar 2.412 26.533 1.4195 6.667E-05 102.65 0.606280 0.99885

Apr 19.371 1.840 0.5619 1.684E-04 7.22 0.042666 0.99710

May 18.179 6.582 1.0234 9.248E-05 9.15 0.054044 0.99841

June 39.389 34.540 1.7188 5.506E-05 0.13 0.000771 0.99905

July 0.564 39.523 1.3787 6.864E-05 0.09 0.000538 0.99882

Aug 0.329 17.765 1.2484 7.581E-05 0.00 0.000000 0.99869


PM = 1-S 0.00154


ESLO2011-040.3


The results of the ETM modeling for KGB rockfish larvae reflected the seasonal abundance of the larvae which were highest in late spring and early summer (Table 3-4). The weights (fi) for the months of May–July accounted for greater than 90 percent of the larvae estimated to be present during the year. The overall annual mortality resulting from the intake at the proposed DWD facility was estimated at 0.00212 or 0.212 percent.

Table 3-4. Mortality estimation (PM) for KGB rockfish complex larvae at intake location based on a larval duration of 7.95 d. Source water volumes calculated from kernel density estimates for back-projections from February–July 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)7.9 d. Survivals with weights (fi) of zero were not included in the calculation of PM.

Period

(2010 - 2011)

Upcoast (km)

Downcoast (km)

Source Volume (km3)

PEi Density


Sept 4.012 3.708 0.2270 4.169E-04 0.00 0.000000 0.99669

Oct 0.796 7.783 0.3760 2.517E-04 0.00 0.000000 0.99800

Nov 4.750 0.089 0.0944 1.003E-03 0.00 0.000000 0.99206

Dec 9.819 11.637 0.5212 1.816E-04 0.05 0.000100 0.99856

Jan 0.822 6.661 0.3292 2.875E-04 5.30 0.011443 0.99772

Feb 1.638 2.238 0.1226 7.719E-04 8.14 0.017592 0.99388

Mar 1.320 11.505 0.3964 2.387E-04 22.10 0.047748 0.99810

Apr 18.733 1.703 0.3077 3.076E-04 81.40 0.175885 0.99756

May 10.785 4.829 0.3703 2.556E-04 292.33 0.631662 0.99797

June 8.361 8.041 0.4882 1.939E-04 52.72 0.113919 0.99846

July 0.564 13.446 0.3799 2.491E-04 0.71 0.001528 0.99802

Aug 0.329 4.736 0.2086 4.537E-04 0.06 0.000124 0.99640


PM = 1-S 0.00212


ESLO2011-040.3


The results of the ETM modeling for blue rockfish larvae were affected by the seasonal abundance of the larvae which were highest in late winter (Table 3-5). The weights (fi) for the months of February and March accounted for 57 percent of the larvae estimated to be present during the year, but blue rockfish larvae occurred during all months of the year. The overall annual mortality resulting from the intake at the proposed DWD facility was estimated at 0.00201 or 0.201 percent.

Table 3-5. Mortality estimation (PM) for blue rockfish complex larvae at the intake location based on a larval duration of 7.95 d. Source water volumes calculated from kernel density estimates for back-projections from January–August 2011 and the average monthly upcoast and downcoast excursions of the back-projections. Densities used for weighting mean survival were measured during a study at DCPP (Tenera 2000b). The survivals were calculated as (1-PE)7.9 d. Survivals with weights (fi) of zero were not included in the calculation of PM.

Period

(2010 - 2011)

Upcoast (km)

Downcoast (km)

Source Volume (km3)

PEi Density


Sept 4.012 3.789 0.3774 2.508E-04 6.51 0.029895 0.99801

Oct 0.796 7.783 0.5495 1.722E-04 3.40 0.015592 0.99863

Nov 4.750 0.446 0.1575 6.009E-04 3.18 0.014598 0.99523

Dec 9.819 11.637 0.9119 1.038E-04 2.95 0.013559 0.99918

Jan 0.822 6.661 0.4903 1.930E-04 43.44 0.199337 0.99847

Feb 1.638 3.128 0.2524 3.750E-04 81.45 0.373794 0.99702

Mar 1.349 21.966 1.0550 8.971E-05 14.16 0.064984 0.99929

Apr 18.733 1.790 0.4070 2.325E-04 14.68 0.067349 0.99815

May 11.777 4.847 0.5663 1.671E-04 22.31 0.102393 0.99867

June 8.361 8.041 0.7184 1.317E-04 17.21 0.078976 0.99895

July 0.564 19.246 1.0394 9.105E-05 6.37 0.029213 0.99928

Aug 0.329 4.736 0.3464 2.732E-04 2.25 0.010311 0.99783


PM = 1-S 0.00201

4.0: Discussion and Conclusions

ESLO2011-040.3


4.0 Impact Assessment Discussion and Conclusions

This impact assessment for the DeepWater Desal (DWD) desalination plant intake in the nearshore area off of Moss Landing Harbor in Monterey Bay, California represents the latest refinement in the use of the Empirical Transport Model (ETM) for assessing the effects of ocean intakes in California. The intake for the DWD facility is expected to have a maximum volume of 94,642 m3 (25,000,000 gal or ~17,360 GPM) per day. The final intake location for the plant may be moved into deeper water that may result in reduced entrainment due to the lower concentrations of fish and invertebrate larvae at deeper depths (Ahlstrom 1959). The assessment of the deepwater intake will require biological sampling to verify any changes in larval fish concentrations with increasing depths and site-specific data on ocean currents at the depth of the intake. Due to the relatively small volume of the intake relative to coastal power plants, the availability of existing biological and oceanographic data from the area around the proposed intake location, and the plans for more detailed sampling in the future, the modeling approach used for this assessment was appropriate.

Almost all previous uses of the ETM in California have relied on biological sampling of the entrainment and source waters to estimate the daily proportional entrainment (PE), which is usually calculated for each taxon for each survey as the ratio of the estimated numbers of larvae entrained per day to the larval population estimates within specific volumes of the source water (Steinbeck et al. 2007). The PE estimates calculated for some of the studies conducted in California showed that in many cases the estimates were, on average, reasonably close to the volumetric ratio of the intake to the sampled source water used in the PE calculation. For example, the volumetric PE for the study at the Huntington Beach Generating Station was 0.0021, and the average PE across the nine fishes analyzed was 0.0023 (MBC and Tenera 2005). This was especially common at intakes located along the open coast in areas with relatively homogeneous habitat, such as the nearshore areas off the Huntington Beach Generating Station, a nearshore area not dissimilar to many areas in Monterey Bay. The volumetric approximation of PE is a reasonable approach when the concentrations of larvae are approximately equal in the intake and source water volumes. This allows the daily mortality to be estimated as the ratio of the volume entrained to the volume in the source water. Although the volumetric approach to PE has been used infrequently in California, this approach was used in the original formulation of the ETM which was used to estimate impacts due to an intake along a river (Boreman et al. 1978, 1981). Using this approach, the only biological data necessary for the model was the estimates of larval duration for the taxa likely to be subject to entrainment. The durations determined for this study were based in part on previous sampling done for the Moss Landing Power Plant in the nearshore areas at the intake location (white croaker) and from studies done near a central coast power plant intake (rockfish and northern anchovy).

One of the assumptions used in this approach is the seasonal abundance patterns used in selecting the months used in the kernel density estimates and the weights used in the ETM calculations are reflective of average conditions in the Monterey Bay area. This assumption was


ESLO2011-040.3


necessary because the data used for the major part of these estimates were taken from studies at the Diablo Canyon Power Plant in San Luis Obispo County approximately 200 km (124 mi) south of Monterey Bay (Tenera 2000b). The validity of this assumption can be tested when the results from the ichthyoplankton sampling for the complete intake assessment are available.

The other data necessary for the ETM volumetric model was the daily volume of the intake 94,640 m3 (25,000,000 gal) which was based on an intake flow rate of 65.7 m3 (~17,360 gal) per minute and the volumes of the source water which were estimated separately for each taxon for each month using data on ocean currents available through CeNCOOS. Data on surface currents over the entire Monterey Bay and surrounding coastline from CeNCOOS CODAR stations were adjusted to midwater column speeds using data from an ADCP current meter located just offshore from the intake from which the data were also made available through CeNCOOS. The use of CODAR for determining the source water areas potentially affected by entrainment is a large improvement over previous assessments that relied on data from one or two ADCP current meters (Tenera 2000b, MBC and Tenera 2005, Steinbeck et al. 2007). These past studies assumed that the current speeds and directions measured at the ADCPs were constant over the large extent of coastline estimated from the current displacement models. The nearshore current results from the CODAR data presented in this report and from studies of larval dispersal related to marine reserves (Bjorkstedt et al. 2002) shows that coastal current patterns are much more complex than the simple models used in previous intake assessments.

Error estimation for the trajectory products based on HF radar observations is an ongoing research area (e.g., Frolov et al., 2012). Given measurement error, which is on the order of 8 cm/sec (Paduan et al., 2006), error in the Lagrangian path estimates will propagate with time and will be larger for conditions with larger horizontal current variations. Fortunately for the present applications, species with the longest larval durations also tend to have the largest source water body volumes. Since the intake volume is fixed, the percent error caused by uncertainty in the source water body volume is likely to be relatively low.

The volumes of the source water areas used in this assessment were based on the depth of the water below the cell used in the kernel density estimations. These included all depths out to the reported depth range of the fishes used in the assessment. Ahlstrom (1959), Boehlert et al. (1985), and Moser and Boehlert (1991) all report that many fish larvae occur at depths shallower than 30–40 m (98–131 ft). Rather than calculating the source volumes based strictly on the depth limit for the adults it may be more reasonable to restrict the source water volumes to depths of 30–40 m (98–131 ft). This was done here for northern anchovy by limiting the depth of the source water estimates to 300 m (984 ft) even though northern anchovy range over areas with much deeper water depths. It seems more reasonable to limit the source water for northern anchovy to even shallower depth as Ahlstrom (1959) found that 93 percent of the larvae occurred in depths shallower than 42 m (138 ft).

Using the source water estimates from the kernel density analysis of the CODAR back-projections, the estimated annual mortalities due to entrainment by the DWD intake of a


ESLO2011-040.3


maximum of 94,640 m3 (25,000,000 gal) per day were very small (<0.3 percent) for all four of the coastal taxa reflecting the small intake volume relative to the source water (Table 4-1).

Fish Taxon Average Source

Volume (km3) Annual PM

northern anchovy 3.405 0.00168

white croaker 1.053 0.00154

blue rockfish 0.318 0.00212

KGB rockfish 0.573 0.00201

Table 4-1. Annual mortality estimates (PM) and average of monthly source water volumes used in ETM modeling for the CIQ goby complex larvae which are transported out of the Moss Landing Harbor-Elkhorn Slough and larvae from four fishes found in the nearshore areas of Monterey Bay.

Due to the extended larval duration (48 d) estimated for northern anchovy, the estimated source water potentially affected by entrainment extended over large portions of Monterey Bay during several of the surveys, including the April 2011 survey period when the larvae were estimated to be in highest abundance. The back-projections even extended outside the bay for the February 2011 survey period.

A comparison of the estimated source water volume for the April survey period for northern anchovy (4.1736 km3) and white croaker (1.4195 km3) when the larvae for both fishes were in highest abundance is shown in Figure 4-1. Despite the large difference in larval duration between these species (northern anchovy = 48.2 d; white croaker = 17.2 d), the downcoast extent of the source water for the April survey is almost identical for the two taxa (northern anchovy = 26.881 km; white croaker = 26.533 km. Table 2-3 and Table 2-4 respectively). In addition the source water areas included in the south portion of the bay are different due to the different months used in the kernel density estimation (see also Figures 2-9 and 2-10). The effects of the months used in the kernel density estimates are even more apparent in a comparison of the total source water body extent for KGB and blue rockfish larvae which both have a larval duration of 7.9 d (Figures 2-11 and 2-12). The source water area for blue rockfish includes a larger portion of the bay south of Moss Landing in comparison with the area for KGB which is mostly to the north. The larger area for blue rockfish is due to the larger number of monthly back-projections used in the estimation (January–August).


ESLO2011-040.3


Figure 4-1 The areal extent of the monthly source water volume (VSi) in April 2011 for a) northern anchovy and b) white croaker. The VSi for each species for April has been superimposed on the total source water body extent to show the remaining area not incorporated into the source water volume for the month of April for these taxa.

Coastal Land

Offshore

300 m Bathymetry

Areal Extent of Source Water Volume (VSi)

Remainder of Total Source Water Body Extent

a)

b)

5.0: Future Direction

ESLO2011-040.3


5.0 Future Direction

This preliminary assessment has highlighted a number of issues which will be considered as part of the final assessment.

The assumption of uniform larval distribution could be tested for sampled source water populations by examining for differences between sites.

It is not clear whether larval myctophids should be excluded from the analysis as the larvae for these fishes may live in shallower waters and therefore should be considered as a viable population potentially subject to entrainment mortality. The gobiidae advected from the slough may also be considered as viable, or at least a proportion of these individuals as they may be returned to the slough by current patterns. Both taxa, and other anomalous taxa as they arise, will be considered for assessment in the ETM based on the best available information on their life history and the use of valid assumptions relating to their transportation to and from natal habitats.

The CODAR data is not consistent across all the grid squares over time. The full assessment will include an assessment of the resolution in the CODAR data. Consideration shall be given to the use of historical CODAR data, married with ADCP data to assess consistencies in larval transportation between years. The ETM inherently assumes that between year variation in the source water population is consistent and this hypothesis can be tested with historical CODAR data. If the assumption holds, CODAR data for multiple years could be combined to assess source water extent.

The back-projections in this preliminary study do not show any vertical mixing component, however historical data and data collected by Tenera indicates some large vertical dynamics at the canyon head. The full ETM will require consideration of the relevance of these processes to the estimation of source water extent and larval entrainment rates at the canyon head.

Back-projections can be calculated for each hour within each period to give a period specific source water extent. This would constitute a source water area that represented all possible points of origin for larvae that spawned within the age range of the sampled entrainable larvae and the spatial locations these larvae are believed to live within which presumably includes areas of high and low food source for example. In addition to the source water extent, a proportion of occurrence within this area can be calculated. This proportional occurrence can then be applied to weight an APF assessment.

If the source water population is to be defined as the spawning sites of potentially entrained larvae, it would be possible to limit the source water area to locations that represent the origins of the larval age bins sampled at the entrainment site. For example, for a given period d larval ages sampled at the entrainment site may include the age ranges between 16 days and 22 days. On this basis, the back-projected locations between 16 and 22 days represent the predicted sites of origin.

6.0 Literature Cited

ESLO2011-040.3


6.0 Literature Cited

Ahlstrom, E. H. 1959. Vertical distribution of pelagic fish eggs and larvae off California and Baja California. U. S. Fish Bull. 60: 107146.

Bjorkstedt, E. P., L. K. Rosenfeld, B. A. Grantham, Y. Shkedy, J. Roughgarden. 2002. Distributions of larval rockfishes Sebastes spp. across nearshore fronts in a coastal upwelling region. Mar. Ecol. Prog. Ser. 242: 215–228.

Boehlert, G. W., D. M. Gadmoski, and B. C. Mundy. 1985. Vertical distribution of ichthyoplankton off the Oregon coast in spring and summer months. U. S. Fish. Bull. 83:611-621.

Boreman, J., C. P. Goodyear, and S. W. Christensen. 1978. An empirical transport model for evaluating entrainment of aquatic organism by power plants. United States Fish and Wildlife Service. FWS/OBS-78/90, Ann Arbor, MI.

Boreman, J., C. P. Goodyear, and S. W. Christensen. 1981. An empirical methodology for estimating entrainment losses at power plants sited on estuaries. Transactions of the American Fishery Society 110: 253260.

Butler, J. L., P. E. Smith, and N. C. H. Lo. 1993. The effect of natural variability of life-history parameters on anchovy and sardine population growth. CalCOFI Rep. 34: 104–111.

Frolov, S., J.D. Paduan, M.S. Cook, and J. Bellingham, 2012: Improved statistical prediction of surface currents based on historic HF-radar observations. Ocean Dynamics, Provisionally Accepted.

Hart, J. L. 1973. Pacific fishes of Canada. Fisheries Research Board of Canada, Bulletin 180. 740 pp.

MacCall, A. D., K. R. Parker, R. Leithiser, and B. Jessee. 1983. Power plant impact assessment: A simple fishery production model approach. Fishery Bulletin 81(3): 613619.

MBC Applied Environmental Sciences (MBC). 1987. Ecology of important fisheries species offshore California. OCS Study 86-0093. Prepared for Minerals Management Service, Pacific OCS Region. 251 p.

MBC and Tenera Environmental (Tenera). 2005. AES Huntington Beach Generating Station entrainment and impingement study final report. Prepared for AES Huntington Beach L.L.C. and California Energy Commission, Sacramento, CA.

6.0: Literature Cited

ESLO2011-040.3


Miller, E. F., J. P Williams and D. J. Pondella II. 2011. Queenfish (Seriphus politus) and white croaker (Genyonemus lineatus) larval growth parameters. CalCOFI Reports 52: 7579.

Moser, H. G. amd G. W. Boehlert. 1991. Ecology of pelagic larvae and juveniles of the genus Sebastes. Environ. Biol. Fishes. 30:203-224.

Moser, H. G. (ed.). 1996. The Early Stages of Fishes in the California Current Region. California Cooperative Oceanic Fisheries Investigations, Atlas No. 33, National Marine Fisheries Service, La Jolla, California. 1505 p.

Moser, H. G. and W. Watson. 2006. Ichthyoplankton. Pages 269–319 In Allen, L. G., D. J. Pondella and M. H. Horn (eds.), Ecology of marine fishes: California and adjacent waters University of California Press.

Paduan, J.D., K.C. Kim, M.S. Cook, and F.P. Chavez, 2006: Calibration and validation of direction-finding high frequency radar ocean surface current observations. IEEE J. Oceanic Engin., 10.1109/JOE.2006.886195, 862-875.

Parker, K. R. and E. E. DeMartini. 1989. Chapter D: Adult-equivalent loss. Technical Report to the California Coastal Commission. Prepared by Marine Review Committee, Inc. 56 p.

Ricker, W.E. 1975. Computation and interpretation of biological statistics of fish populations. Fish. Res. Board of Canada. Bull. 91. 382 p.

Steinbeck, J. R., J. Hedgepeth, P. Raimondi, G. Cailliet, and D. L. Mayer. 2007. Assessing power plant cooling water intake system entrainment impacts. Report to California Energy Commission. CEC-700-2007-010. 105 p.

Tenera. 2000a. Moss Landing Power Plant Modernization Project 316(b) Resource Assessment. Prepared for Duke Energy Moss Landing, LLC. Oakland, CA.

Tenera. 2000b. Diablo Canyon Power Plant 316(b) Demonstration Report. Report No. E9-055.0. Prepared for Pacific Gas and Electric Company. March 2000. 596 p.

Yoklavich, M. M., V. J. Loeb, M. Nishimoto, and B. Daly. 1996. Nearshore assemblages of larval rockfishes and their physical environment off central California during an extended El Niño event, 19911993. Fishery Bulletin 94: 766782.

PRELIMINARY MODELING OF POTENTIAL ... - DeepWater Desal · DeepWater Desal ESPreliminary Intake...

Documents

Transcript of PRELIMINARY MODELING OF POTENTIAL ... - DeepWater Desal · DeepWater Desal ESPreliminary Intake...