DeepWater Desal DRAFT MOSS LANDING DESALINATION PLANT INTAKE IMPACT ASSESSMENT: LARVAL ENTRAINMENT May 2014 Submitted to: Dr. Brent Constanz Mr. James Tucker DeepWater Desal, LLC Dynegy Moss Landing, LLC 7532 Sandholdt Rd, Suite 6 Moss Landing Power Plant Moss Landing, CA 95039 Moss Landing, CA 95039 Prepared by: Environmental 141 Suburban Rd., Suite A2, San Luis Obispo, CA 93401 ESLO2013-045 Executive Summary This report presents an assessment of the potential for impacts to fish and invertebrate marine life due to water withdrawals at Moss Landing in Monterey Bay, California associated with the proposed operation of an ocean water desalination facility by DeepWater Desal (DWD) LLC. The Central Coast Regional Water Project (CCRWP) proposed by DWD would have a maximum intake requirement of 63 million gallons of seawater per day (MGD) with an interim phase capacity of 25 MGD. The proposed location of the intake for the desalination facility is unique due to its proximity to a submarine canyon, the Monterey Submarine Canyon (the Canyon), which reaches close to the shore at Moss Landing. DWD has proposed to construct an intake pipe to withdraw seawater from depths significantly deeper than a traditional seawater desalination facility at the head of the Canyon. The objectives of this study were to assess: 1. the potential for impacts to fish and invertebrate marine life due to larval entrainment through the CCRWP’s feedwater intake pipe, and 2. the potential benefits of a deep water intake design in relation to the entrainment of marine fish and invertebrate larvae. The information in this report will be used as part of the compliance assessment with California State Water Code Section 13142(d), which states that “independent baseline studies of the existing marine system should be conducted in the area that could be affected by a new or expanded industrial facility using seawater in advance of the carrying out of the development.” The proposed intake for the CCRWP is not subject to regulation under the Federal Clean Water Act Section 316(b), or the California Statewide Water Quality Control Policy on the Use of Coastal and Estuarine Waters for Power Plant Cooling. However, California regulatory agencies have generally required that 316(b)-type studies be conducted for ocean intakes at coastal power plants and desalination facilities in California. Study Rationale and Methods Withdrawal of ocean water for industrial uses can result in environmental effects due to impingement and entrainment of aquatic life. Impingement of larger organisms occurs when they are trapped against the screening systems commonly used at intake entrances, and entrainment mortality occurs to smaller, generally planktonic, marine organisms when they pass through the screening system into the industrial facility. The planned use of a wedgewire screen on the desalination feedwater intake, coupled with low intake water velocities, would eliminate any significant effects of impingement. Therefore, this study addressed the potential effects of entrainment on larval fishes and certain larval invertebrates with a study design similar to that used for much larger intakes associated with coastal electric generating facilities, and also for other proposed coastal desalination facilities located elsewhere in California. At full phase design, the CCRWP intake will entrain 238,481 m3 per day (63 MGD) of seawater with an intake ESLO2013-045.1 DeepWater Desal Larval Entrainment ES-1 Executive Summary volume of 94,635 m3 per day (25 MGD) for the interim phase of the project. This study assesses the potential impacts from entrainment for both design phases. The location of the project at the head of the Monterey Canyon offers the opportunity to access deep water close to shore. The close proximity of the Canyon to the shore at Moss Landing reduces the length of pipe needed and the subsequent pumping demands in accessing deeper water compared to locations not adjacent to a submarine canyon. This results in a more efficient, low impact (economic and environmental) deep water intake design. The second advantage to this location is the presence of an internal tide at this site. Unlike a surface tide that results in the rise Figure ES-1. Location of Intake and Source Water and fall of the surface of the ocean, the Stations for plankton sampling. internal tide such as the one occurring at the head of the Monterey Canyon results in the rise and fall of a layer of cold, dense seawater trapped below the sea surface. The interface (thermocline) between the deeper, colder water and warmer surface waters rises and falls twice per day at the head of the Canyon, immersing the proposed intake site in cold deep water as it does so. Based on other studies, larval fish are expected to occur predominantly in surface waters, partly because that is where the adults live and spawn, and also because there is more food for larval fish in shallower waters that have more sunlight and subsequently richer planktonic ecosystems within which these larvae feed. This potentially offers a unique opportunity to reduce the entrainment effect of an intake by accessing deeper water in this way. In order to determine the potential effects of the proposed intake on larval fish and target larval invertebrate taxa, biological and oceanographic data were collected from June 2012–June 2013 at representative intake locations (I2 and I3) and at nearby source water stations (SN and SS) (Figure ES-1). These plankton samples provided a baseline characterization of the potentially entrainable larvae. These data were used to estimate the number of larvae that may be entrained by the proposed intake annually, and also to calculate the proportional mortality (PM), which is the proportion of a defined population that would theoretically be lost due to entrainment mortality. ESLO2013-045.1 DeepWater Desal Larval Entrainment ES-2 Executive Summary The premise of the potential benefit of a deep water intake design in reducing entrainment is that the larval fish concentrations at the depths proposed for the CCRWP are less than the concentrations at shallower depths proposed for other desalination plants in California. In order to test the hypothesis that a deeper intake may entrain less fish, a statistical comparison was made between the larval fish concentration at two depths. Plankton samples were taken in continuous tows from the surface to a maximum depth of 40 m (131 ft), and from the surface to a maximum depth of 25 m (82 ft), at the four stations offshore from Moss Landing. Samples were collected at each station and for each depth once during the day and once at night. Flow meters mounted in the center of the opening of each net frame measured the actual volume of water filtered through each net and allowed for calculations of larval concentrations in each sample (Figure ES-2). Preserved samples from the field were returned to the laboratory, where they were examined under a dissecting microscope and all fish Figure ES-2. Bongo frame and plankton nets used to larvae and target invertebrate larvae were collect fish and shellfish larvae at the intake and in removed, counted, and identified to the the source water. lowest possible taxonomic level. Notochord length (NL) was determined for a representative number of larval fish for each taxon. These measurements were determined and recorded for up to 50 specimens from each taxon during each survey using a video capture system and image analysis software. These data were used to determine the age of the larval fish captured. Individuals longer than 30 mm (1.18 in) were considered non-entrainable because they would not normally be susceptible to entrainment due to their size. A detailed QA/QC program was applied to all laboratory processing.The method of assessment applied in this study is called the Empirical Transport Model (ETM) and is the primary method used in assessing the entrainment effects of ocean water intake systems in California (Steinbeck et al. 2007). The goal of the ETM is to produce an estimate of proportional mortality (PM), which is the proportion of larvae lost from a source water population due to entrainment. This is calculated for individual target taxon that are selected based on those fishes that were found to be most abundant in the samples. These taxa provide the most accurate estimate of PM because they are in greater number. They also provide a more conservative estimate of the impact as the scale of entrainment is greater than other species that are less abundant at the intake site. In this study, the most abundant fish from the 40 m deep tows at the two intake stations where selected, as these samples best represented the larval fishes likely to be entrained based on the proposed depth of the intake. The six taxonomic groups (taxa) of fishes that met these criteria were: northern anchovies (Engraulis mordax), white croaker (Genyonemus lineatus), the CIQ goby complex, sanddabs (Citharichthys spp.), the blue rockfish complex (Sebastes spp. V) and ESLO2013-045.1 DeepWater Desal Larval Entrainment ES-3 Executive Summary the KGB rockfish complex (Sebastes spp. V_) in order of total abundance. Together these six taxa comprised approximately 83% of the total estimated fish larvae sampled in the 40 m deep tows at the intake stations during the June 2012–June 2013 study period. Also included in the assessment were Cancer crab megalops, which includes the edible species of rock crabs. Market squid (Doryteuthis opalescens) paralarvae were also observed in lesser numbers than the combined crab larva, however these are not selected for taxa specific analysis in this study. The calculation of PM (the output of the ETM) for each larval taxon required an estimate of the number of larvae entrained and the size of the source water population from which they were potentially entrained.