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Home My WebLink AboutSEPA Att B1 Eelgrass 2015 146 N Canal St, Suite 111 • Seattle, WA 98103 • www.confenv.com BDN EELGRASS DELINEATION AND DEPTH OF CULTURE SURVEY, HOOD CANAL, WASHINGTON DRAFT Prepared for: BDN, Inc. October 16, 2015 May 07 2021 1 46 N Canal St, Suite 111 • Seattle, WA 98103 • www.confenv.com BDN EELGRASS DELINEATION AND DEPTH OF CULTURE SURVEY, HOOD CANAL, WASHINGTON DRAFT Prepared for: BDN, LLC 3011 Chandler St. Tacoma, WA 98409 Attn: Brad Nelson, Robert Smith Prepared by: Marlene Meaders, Phil Bloch, Chris Cziesla, and Grant Novak Confluence Environmental Company October 16, 2015 Page i TABLE OF CONTENTS 1.0 INTRODUCTION ........................................................................................................... 1 2.0 METHODS ................................................................................................................... 4 2.1 Eelgrass Delineation ................................................................................................................... 4 2.1.1 Towed Video Surveys ......................................................................................................... 4 2.1.2 Snorkel-Based Surveys ....................................................................................................... 6 2.2 Depth of Culture ......................................................................................................................... 6 3.0 FINDINGS .................................................................................................................... 7 3.1 Native Eelgrass – BDN West Site ................................................................................................ 7 3.2 Native Eelgrass – BDN East/Smersh Site .................................................................................. 10 3.3 Depth of Culture ....................................................................................................................... 10 4.0 SUMMARY .................................................................................................................. 13 5.0 REFERENCES .............................................................................................................. 14 APPENDICES A – Site Photos B – Depth Measurement and Tidal Corrections TABLES Table 1 – Eelgrass Delineation Sites in Hood Canal, Washington ............................................................ 1 FIGURES Figure 1 — Study Area Vicinity ................................................................................................................ 3 Figure 2 — Towed Video Transects at the BDN Sites in Hood Canal, Washington ................................... 5 Figure 3 — Eelgrass at the BDN West Site in Hood Canal, Washington ................................................... 9 Figure 4 — Eelgrass at the BDN East/Smersh Site in Hood Canal, Washington ..................................... 11 Figure 5 — Comparison with DNR SVMP monitoring observations at BDN East/Smersh Site in Hood Canal, Washington ....................................................................................................... 12 Page 1 BDN EELGRASS DELINEATION AND DEPTH OF CULTURE SURVEY, HOOD CANAL, WASHINGTON DRAFT 1.0 INTRODUCTION This document summarizes an eelgrass (Zostera marina) delineation and depth of culture survey conducted on September 4 and September 29, 2015, at an existing and proposed geoduck (Panopea generosa) farm in Hood Canal, Washington (Figure 1). The existing and proposed farm areas are currently owned and/or leased by BDN, LLC (BDN). An eelgrass delineation was performed by Confluence Environmental Company (Confluence) at four sites west of the Hood Canal Bridge (Table 1). Table 1 – Eelgrass Delineation Sites in Hood Canal, Washington Site Tax Lot Parcels Intertidal Elevation Range (ft MLLW) Total Intertidal Area (acre) Proposed Culture Area (acre) BDN West Site 821334078, 821334011, 821334076, 821334075, 821334074 +10.0 to -2.0 ft MLLW 6.351 3.661 Former Washington Shellfish Site 821334073 +10.0 to -2.0 ft MLLW 5.32 2.23 Former Mocean Shellfish Site 821334079 +10.7 to -2.0 ft MLLW 0.74 0.565 BDN East/Smersh Site 721031007 +10.7 to -2.0 ft MLLW 8.33* 3.52* MLLW = mean lower low water +10.70 ft MLLW = mean higher high water (Lofall Datum Station ID 9445088) 1 As identified in MS&A 2013a,b 2 As identified in Washington Shellfish 2012 3 As identified in MS&A 2014 4 As identified in Ma 2012 5 As identified in Corps 2012 BDN previously commissioned an eelgrass delineation of these sites (MS&A 2013a,b, MS&A 2014). At the BDN West Site, native eelgrass was identified predominantly from -1.9 feet (ft) to -2.9 ft mean lower low water (MLLW), although individual native eelgrass shoots were identified as far up the beach as -1.4 ft MLLW. In addition, Japanese eelgrass (Z. japonica) was a major component of the vegetation throughout the intertidal zone. Japanese eelgrass covered intertidal habitat from -1.5 ft to above +2 ft MLLW. At the former Washington Shellfish Site, native eelgrass was observed to extend to approximately -1.8 ft MLLW with “a few blades” observed along multiple transects in areas otherwise dominated by Japanese eelgrass (Z. japonica) between up to approximately +1.0 ft MLLW. Japanese eelgrass was observed above approximately +1.8 feet MLLW, however in many transects there was a gap of 50 or more linear feet between the observed native eelgrass bed and Japanese eelgrass observations (MS&A 2014). At the BDN East/Smersh Site, native eelgrass was identified predominately BDN– Eelgrass Delineation and Culture Depth Page 2 from -1.5 ft to -3.0 ft MLLW. Patchy Japanese eelgrass was observed from -1.5 ft to approximately +2 ft MLLW. During a July 1, 2015 site visit, the U.S. Army Corps of Engineers (Corps) noted a concern that the prior eelgrass delineations performed in 2013 and 2014 did not appear to reflect current eelgrass conditions in July 2015 and that they may have included inaccurate identification of native eelgrass (Z. marina) as compared to Japanese eelgrass (Z. japonica). On July 30, 2015, the Corps requested new eelgrass surveys for the following parcels: NWS-2013-1147 (Tjemsland lease), NWS-2013-1223 (BDN), NWS-2013-1223 (Garten lease), NWS-2013-1268 (Smersh), and NWS-2012-1210 (BDN -formerly Washington Shellfish). In a separate letter dated September 4, 2015, the Corps expressed concern regarding planting on the former Mocean Shellfish Site (NWS-2012-1099) within 10 horizontal feet of eelgrass and waterward of a -1.5 tidal elevation, and requested information regarding prior work conducted on the site. The two objectives of the eelgrass delineation performed on September 4 and September 29, 2015 were to identify the landward extent of the native eelgrass at the four BDN sites associated with the proposed and existing geoduck culture (as identified in Table 1), and identify the depth of culture at the former Mocean Shellfish Site. BDN– Eelgrass Delineation and Culture Depth Page 3 Figure 1 — Study Area Vicinity BDN– Eelgrass Delineation and Culture Depth Page 4 2.0 METHODS The following sections provide a description of the methods used for the eelgrass delineation at the BDN West Site, former Mocean Site, former Washington Shellfish Site, and BDN East/Smersh Site. In addition, the methods used to determine the depth of culture at the former Mocean Shellfish Site is also provided. 2.1 Eelgrass Delineation Towed video and snorkel-based transects were used to identify the extent of native eelgrass in the survey areas. 2.1.1 Towed Video Surveys During the September 4, 2015 survey, a towed video system with integrated Global Positioning System (GPS) was used to collect information about native eelgrass presence/absence. Towed video data were collected in transects running perpendicular to the beach and spaced about every 45 feet (Figure 2). In addition, a transect that ran parallel to the shoreline was collected along the anticipated eelgrass bed edge and landward of the edge. The video system electronically recorded latitude and longitude to aid in the mapping of native eelgrass locations. The boat maintained a consistent speed and the video was constantly monitored to confirm that it was close enough to the seafloor to determine vegetative cover. Actual position of the boat was recorded at all times during the surveys. A differential GPS (dGPS) with sub-meter accuracy was used to collect positions at one second intervals during the towed video surveys. The clocks in the video GPS and dGPS were synchronized and the time of each point was recorded to the nearest second. To aid mapping, a proprietary program created by Confluence was used when reviewing the video to characterize presence/absence of native eelgrass. The entirety of the field-collected video data was reviewed in the office on a high definition monitor to ensure that habitat variables were accurately characterized. The video mapping program was synched with the video data through the video’s time stamp. The program allowed the reviewer to create tabular records defining the habitat characterization at one second intervals as the video was being viewed. These tabular data describing the vegetative cover, substrate material, relief, and complexity were then joined, using the time stamp, to the dGPS positions thereby allowing the high quality characterization of video that occurred in the office to be linked to the highly accurate dGPS positions and video data collected in the field. This provided an accurate and efficient way to create eelgrass delineation maps of the study areas. BDN– Eelgrass Delineation and Culture Depth Page 5 Figure 2 — Towed Video Transects at the BDN Sites in Hood Canal, Washington BDN– Eelgrass Delineation and Culture Depth Page 6 2.1.2 Snorkel-Based Surveys During the September 29, 2015 survey, the edge of native eelgrass was confirmed using snorkel-based surveys and a dGPS unit at the BDN East/Smersh Site. Because video interpolation has limitations in terms of accurately depicting information between transects, two biologists snorkeled the landward native eelgrass boundary using a floating dGPS unit to precisely collect location data. The biologists divided the area into two eelgrass zones: patchy vs. continuous. These zones were mapped according to the following criteria: Patchy = individual shoots or small patches of native eelgrass (typical of shoots migrating from the main eelgrass bed). Continuous = the main native eelgrass bed with few locations where eelgrass was absent (typical of a fringe eelgrass bed). The landward edge of the patchy eelgrass zone was considered to be the upper (or landward) extent of native eelgrass habitat identified below. Underwater video, using a GoPro® HERO4 camera, was collected during the snorkel-based surveys. 2.2 Depth of Culture Depth of culture was evaluated at the former Mocean Shellfish Site during the September 29, 2015 survey using the location of existing PVC tubes as a reference. Depth and time were collected at five locations. These depth measurements were then corrected for tidal height using the predicted tide levels at Lofall, WA (Station ID 9445088) and the difference between predicted and preliminary1 tide levels at Port Townsend, WA (Station ID 9444900). There was no attempt to account for barometric pressure, and the depth readings were collected from the side of the research vessel. 1 Note that verified data was not available as of October 12, 2015. BDN– Eelgrass Delineation and Culture Depth Page 7 3.0 FINDINGS The following information is a summary of findings at the four sites in Hood Canal where an eelgrass delineation and depth of culture survey was conducted. Approximately 17 transects were on or adjacent to the BDN west site, 10 transects were on or adjacent to the former Washington Shellfish site and 5 transects are on or adjacent to the former Mocean site. A combined total of 26 video transects were collected at the BDN West, former Mocean and former Washington Shellfish sites and 18 video transects collected at the BDN East/Smersh Site (see Figure 2). The findings are divided by site and type of survey. Screen captures from the towed video camera are provided in Appendix A. 3.1 Native Eelgrass – BDN West Site, former Mocean Site and former Washington Shellfish Site Eelgrass at the BDN West Site was a mix of the native and Japanese eelgrass species (Figure 3). Eelgrass zonation at this site was less distinct on visual inspection than typical Puget Sound or West Coast sites (e.g., Shafer et al. 2008, Britton-Simmons et al. 2010, Ruesink et al. 2010). In addition, morphology was not a dependable characteristic for identification. For example, length and width of blades gradually become narrower and shorter with depth, rather than a distinct difference between the two species. Even root structure (e.g., two roots at each node for Japanese eelgrass vs. clusters of roots at each node for native eelgrass) was not straight-forward at this site. Almost the entire intertidal area of the BDN West Site was covered in eelgrass (both Z. marina and Z. japonica). The main native eelgrass bed was a fringe bed between -10 ft to -2 ft MLLW. Above this elevation, native eelgrass and Japanese eelgrass were intermixed within a transition area between -2 ft and -1.5 ft MLLW where there was a gradual shift in the dominance to Japanese eelgrass as the depth became shallower. Native eelgrass remained present in small patches and individual shoots throughout the lower intertidal up to the highest elevations surveyed by video (in excess of +1 ft MLLW). In addition, above approximately -2 ft MLLW, eelgrass blades were extensively covered in epiphytes such that many individual blades had a brownish appearance, making visual identification difficult. The gradual transition of morphological characteristics made clear delineation of native and Japanese eelgrass populations challenging from visual evidence alone. Therefore, we could not definitively identify a landward boundary (using towed video methods) of where the native eelgrass ended and the Japanese eelgrass began. At the former Washington Shellfish Site, existing geoduck culture areas appear to be placed at higher elevations than the primary native eelgrass (Z. marina) bed, however individual Zostera marina shoots intermixed with Zostera japonica do occur in areas where culture operations are present. Culture operations do not appear to influence the location of native eelgrass when tubes were present. These observations are consistent with the August 11, 2014 survey of the site which reported “a few blades” of native eelgrass present in some areas between -2.0 ft MLLW and +1.0 ft MLLW (MS&A 2014). BDN– Eelgrass Delineation and Culture Depth Page 8 At the former Mocean Site existing geoduck culture areas were found in areas where native eelgrass shoots were present However, culture operations did not appear to influence the location of native eelgrass when tubes were present. Information related to baseline conditions was not available, and so it was not possible to determine whether these areas were colonized by eelgrass after tubes were added or whether it existed prior to the installation of tubes. The only conclusion that can be made in terms of the interaction between eelgrass and existing culture is that both eelgrass and geoduck aquaculture coexist under current operations. BDN– Eelgrass Delineation and Culture Depth Page 9 Figure 3 — Eelgrass at the BDN West Site, Former Mocean Site, and Former Washington Shellfish Site in Hood Canal, Washington BDN– Eelgrass Delineation and Culture Depth Page 10 3.2 Native Eelgrass – BDN East/Smersh Site Eelgrass at the BDN East/Smersh Site followed typical zonation patterns identified throughout Puget Sound and along the West Coast (e.g., Shafer et al. 2008, Britton-Simmons et al. 2010, Ruesink et al. 2010), where the native eelgrass occurred lower in the intertidal/subtidal (typically below -2 ft MLLW), the Japanese eelgrass occurred higher (above -1.5 ft MLLW), and a relatively unvegetated zone occurred between -2 ft and +2 ft MLLW (Figure 4). Additionally, the morphology of the two eelgrass species was distinct, with smaller, shorter blades identifying the Japanese eelgrass and wider, longer blades identifying the native eelgrass. This distinction between species was also confirmed by evaluating eelgrass root structure, as described above. The native eelgrass occurred in two basic zones: patchy and continuous. The patchy zone extended up to -1.5 ft MLLW and the continuous zone occurred from -2 ft to -16 ft MLLW. This is in accordance with the prior surveys performed by Marine Surveys and Assessments on the parcel. Washington Department of Natural Resources (DNR) maintains an eelgrass monitoring location adjacent to the BDN East/Smersh Site. The DNR site, HDC2518, is characterized as having a mix of native and Japanese eelgrass. Washington DNR’s monitoring efforts were compared to the underwater video monitoring described above for the BDN East/Smersh Site (Figure 5). There was good agreement between the two surveys. Therefore, eelgrass bed depths described above are, in part, taken from eelgrass observations made by Washington DNR in transects immediately adjacent to transects observed in this study (DNR 2015). 3.3 Depth of Culture The location of existing culture operations at the former Mocean Shellfish Site was identified by the lower extent of culture tubes. The depth collected at these locations ranged from -1.2 ft to -1.9 ft MLLW (or an average of -1.5±0.3 ft MLLW). While this estimate is more accurate than a visual survey during a low tide event, it does not represent the level of accuracy that a land-based survey tied to the nearest monument can obtain. For example, tidal corrections between observed and predicted tides at the reference site (Port Townsend) suggest that predicted tides may be under or over estimated by 0.3 feet. The calculations associated with the depth of culture is provided in Appendix B. BDN– Eelgrass Delineation and Culture Depth Page 11 Figure 4 — Eelgrass at the BDN East/Smersh Site in Hood Canal, Washington BDN– Eelgrass Delineation and Culture Depth Page 12 Figure 5 — Comparison with DNR SVMP monitoring observations at BDN East/Smersh Site in Hood Canal, Washington BDN– Eelgrass Delineation and Culture Depth Page 13 4.0 SUMMARY This report addresses the potential concerns raised by the Corps raised during its July 1, 2015 visit and July 30, 2015 and September 4, 2015 letters. A distinct native eelgrass bed was identified at the BDN East/Smersh Site with only minor overlap of Japanese eelgrass within the native eelgrass zone. There was a clear transition between the two species at this site, and the majority of intertidal habitat beyond the native eelgrass boundary was unvegetated habitat. The upper extent of native eelgrass was between -2 and -1.5 ft MLLW. Conversely, at the BDN West Site, the transition between native eelgrass and Japanese eelgrass was gradual with a number of locations where mixing occurred between the two species. There was no clear break where native eelgrass ended and non-native Japanese eelgrass started at this site. At the Former Washington Shellfish Site, there was evidence that geoduck clams are located in areas that currently have native eelgrass. The presence of tubes does not appear to restrict native eelgrass presence. While there is no way to determine, based on the information collected, whether geoduck clams were originally planted in native eelgrass, both native eelgrass and geoduck culture appear to be able to coexist. The elevations at which culture tubes were present in the former Mocean Shellfish Site was estimated to be -1.5±0.3 ft MLLW, which is approximately where the culture was proposed based on the hand- drawn map provided by Mocean Shellfish, Inc. in their application materials and Corps permit. Although, no clear indication of where planting would occur was provided in the permit, other than newly positioned shellfish2 would be 10 ft from native eelgrass and higher than a -2 ft MLLW tidal elevation. While the method used to determine depth of planting is more accurate than a visual survey, the only way to determine the exact elevation of this culture area is to conduct a land survey of the area. 2 “Newly positioned shellfish” is defined as shellfish being placed within a portion of the project area where aquaculture was not located and had not previously occurred as of the date the permit was issued. BDN– Eelgrass Delineation and Culture Depth Page 14 5.0 REFERENCES Britton-Simmons, K.H., S. Wyllie-Echeverria, E.K. Day, K.P. Booth, K. Cartwright, S. Flores, C.C. Garcia, T.L. Higgins, C. Montanez, A. Rames, K.M. Welch, and V. Wyllie-Echeverria. 2010. Distribution and performance of the nonnative seagrass Zostera japonica across a tidal height gradient on Shaw Island, Washington. Pacific Science 64(2):187-198. Corps (U.S. Army Corps of Engineers). 2012. NWS-2012-1099: Mocean Shellfish, Inc. Department of the Army, Seattle District, Corps of Engineers, Seattle, Washington. November 2, 2012. DNR (Washington Department of Natural Resources) 2015. Eelgrass Monitoring GIS Database accessed at http://www.dnr.wa.gov/programs-and-services/aquatics/aquatic-science/nearshore-habitat- eelgrass-monitoring on October 12, 2015. Ma, C. 2012. Nationwide Permit 48 Pre-Construction Notification Form for Existing Commercial Shellfish Activities, Renton, Washington. September 15, 2012. MS&A (Marine Surveys & Assessments). 2013a. BDN LLC Geoduck Aquaculture Project: Biological Evaluation. Marine Surveys & Assessments, Port Townsend, Washington. October 23, 2013. MS&A. 2013b. BDN LLC/Smersh Geoduck Aquaculture Project: Biological Evaluation. Marine Surveys & Assessments, Port Townsend, Washington. October 28, 2013. MS&A. 2014. Technical Memorandum: Methodology for Eelgrass and Macroalgae Surveys for BDN LLC’s formerly McRae Parcel. Marine Surveys & Assessments, Port Townsend, Washington, October 31, 2014. Ruesink, J.L., J. Hong, L. Wisehart, S.D. Hacker, B.R. Dumbauld, M. Hessing-Lewis, and A.C. Trimble. 2010. Congener comparison of native (Zostera marina) and introduced (Z. japonica) eelgrass at multiple scales within a Pacific Northwest estuary. Biol Invasions 12:1773-1789. Shafer, D.J., S. Wyllie-Echeverria, and T.D. Sherman. 2008. The potential role of climate in the distribution and zonation of the introduced seagrass Zostera japonica in North America. Aquatic Botany 89:297-302. Washington Shellfish Inc. 2012. Nationwide Permit 48 Pre-Construction Notification Form for Existing Commercial Shellfish Activities, Gig Harbor, Washington. November 5, 2012. Appendix A Site Photos BDN Eelgrass: Appendix A Page A-1 Photo 1 – Continuous native eelgrass (Zostera marina) at the BDN West Site (Transect 6). Photo 2 – Continuous native eelgrass (Zostera marina) at the BDN West Site (Transect 24). BDN Eelgrass: Appendix A Page A-2 Photo 3 – Possible mixed populations of native eelgrass (Zostera marina) and Japanese eelgrass (Z. japonica) at the BDN West Site (Transect 16). Photo 4 –Possible mixed populations of native eelgrass (Zostera marina) and Japanese eelgrass (Z. japonica) at the BDN West Site (Transect 18). BDN Eelgrass: Appendix A Page A-3 Photo 5 –Upper elevation edge within the patchy native eelgrass (Zostera marina) zone at the BDN East/Smersh Site (Transect 28). BDN Eelgrass: Appendix A Page A-4 Photo 6 –Patchy Japanese eelgrass (Zostera japonica) at the BDN East/Smersh Site (Transect 28). Photo 7 –Unvegetated habitat at the BDN East/Smersh Site above -2 ft MLLW (Transect 44). BDN Eelgrass: Appendix A Page A-5 Photo 8 –Continuous native eelgrass (Zostera marina) bed at the BDN East/Smersh Site with clear unvegetated break landward of the bed (Transect 38). Photo 9 –Japanese eelgrass bed (Zostera japonica) at the BDN East/Smersh Site (Transect 39). Photo 10 –Example of geoduck culture tubes in Japanese eelgrass bed (Zostera japonica) at the former Washington Shellfish (Transect 26). Appendix B Depth Measurements and Tidal Corrections BDN Eelgrass: Appendix B Page B-1 Station ID# 9445088 (Lofall, WA) Tide Predictions: Date Day Time Hgt 9/29/2015 Tue 6:10 AM 10.88 H 9/29/2015 Tue 12:12 PM 2.13 L 9/29/2015 Tue 6:07 PM 11.35 H Station ID# 9444900 Port Townsend, WA Predicted vs. Preliminary Date Time (LST/LDT) Predicted (ft) Preliminary (ft) Difference (ft) Tide at Lofall (ft) Depth at Site (ft) Notes 9/29/2015 10:36 2.6 2.6 0.1 3.0 9/29/2015 10:42 2.5 2.6 0.1 3.0 Low for Port Townsend, WA 9/29/2015 10:48 2.5 2.6 0.2 2.9 9/29/2015 10:54 2.4 2.6 0.2 2.9 9/29/2015 11:00 2.4 2.6 0.3 2.9 9/29/2015 11:06 2.4 2.7 0.3 2.9 9/29/2015 11:12 2.4 2.7 0.3 2.8 9/29/2015 11:18 2.4 2.7 0.3 2.8 9/29/2015 11:24 2.4 2.7 0.4 2.8 9/29/2015 11:30 2.4 2.7 0.3 2.8 9/29/2015 11:36 2.4 2.8 0.3 2.8 9/29/2015 11:42 2.5 2.8 0.3 2.8 9/29/2015 11:48 2.5 2.8 0.3 2.7 9/29/2015 11:54 2.6 2.9 0.3 2.7 9/29/2015 12:00 2.6 2.9 0.3 2.7 9/29/2015 12:06 2.7 3.0 0.3 2.6 9/29/2015 12:12 2.8 3.1 0.3 2.4 2.13 ft = Low for Lofall, WA 9/29/2015 12:18 2.9 3.2 0.3 2.5 9/29/2015 12:24 3.0 3.3 0.3 2.6 9/29/2015 12:30 3.0 3.4 0.3 2.7 1.9 Depth = 56" 9/29/2015 12:36 3.1 3.5 0.3 2.8 9/29/2015 12:42 3.2 3.6 0.3 2.9 1.7 Depth = 57" 9/29/2015 12:48 3.4 3.7 0.3 3.0 9/29/2015 12:54 3.5 3.8 0.3 3.1 1.5 Depth = 53" 9/29/2015 13:00 3.6 3.9 0.3 3.3 9/29/2015 13:06 3.7 4.0 0.3 3.4 1.3 Depth = 53" 9/29/2015 13:12 3.8 4.1 0.3 3.5 1.2 Depth = 54" 9/29/2015 13:18 3.9 4.2 0.3 3.6