3815_PGSF WMVD Pkg 2_Vol 4-2_03.03.2026_BXWA_Certified

ASPECT CONSULTING 48 FINAL PROJECT NO. AS190583A-08  MAY 21, 2025 of K-C and Ecology conducted an initial reconnaissance of the shoreline intertidal area during lower low tide stage. The initial reconnaissance included visual observation and documentation of pipe conditions, pipes discharging water, bulkhead conditions, and diffuse seepage emanating from the intertidal beach. Measurements of water quality field parameters (EC, pH, and temperature) were collected for most of the observed water discharges, and multiple field parameter measurements were collected from select discharge locations during outgoing (ebb) and incoming (flood) tidal stages. Using that information, an Addendum to the RI/FS Work Plan (Aspect, 2016a) was prepared and approved by Ecology to conduct a supplemental round of intertidal seep sampling and analysis. Because the intent was to characterize the quality of upland groundwater discharge, not tidal water, the Addendum required sampling of water discharges with EC less than 25 millisiemens per centimeter (mS/cm). The supplemental seep sampling program was conducted during lower low tide stages on two nights: October 18 and 20, 2016. On the first night, field parameter measurements were conducted at visible seepage locations across the entire accessible intertidal shoreline. Any seep locations with measured EC below 25 mS/cm were designated for subsequent sampling on the second night. Also at those locations, passive in situ diffusive gradient in thin film (DGT) samplers were deployed at a depth of approximately 6 inches below mudline to measure free sulfide concentrations within the sediment bioactive zone, in accordance with the Work Plan Addendum. In total during August and October 2016, field parameters were measured at 16 intertidal locations: 14 beach seeps, an uncapped pipe on the beach under the north end of the (labeled Discharge 4A), and a hole in the timber bulkhead in the timber bulkhead several feet above mudline near the north end of the shoreline (former Naval Reserve parcel), labeled Discharge 1A. Based on the first night’s field measurements, seep samples were collected during the second night at five locations with EC measured below 25.0 mS/cm: Seep-3 located next to the former barge unloading dock near the south end of the former Log Pond, and Seeps-10, -11, -12, and -13 located at the base of the former Naval Reserve parcel timber bulkhead. The field parameter data from saline seeps not sampled for chemical analysis are also presented in this RI/FS. The seep samples were collected using a PushPoint™ stainless steel sampler inserted generally horizontally into the beach to submerge its 4-cm stainless steel mesh screen within the upper 10 cm of sediment. Sampling of the last location (Seep-10) was conducted as the tide water was encroaching on the location, but the sampler remained submerged in sediment 17. The DGT samplers were also retrieved during the second night, after approximately 48 hours immersion. Ecology participated in both night’s activities, and collected split samples for chemical analysis at the Manchester Environmental Laboratory. Each of the seep water samples were submitted for analysis of total ammonia and dissolved metals (arsenic, copper, lead, mercury, nickel, and zinc) using analytical methods specified in the QAPP (Aspect, 2013c), and for salinity using Standard Method SM 2520B. In addition, the Seep-3 sample was analyzed for low-level PAHs. 17 Sample Seep-10 was inundated by the tide at the time of sampling.