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

ASPECT CONSULTING PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 21 1,500 and 2,200 ft3/year (3,700 ft3/year combined). For the entire Upland Area shoreline, the estimated total groundwater flux to the East Waterway is 624,000 ft3/year (Table 2-4). The estimated groundwater discharges from the Log Pond area fill and sawdust layer represent approximately 0.2 and 0.4 percent, respectively, of this total flux. 2.4.5 Storm Water Management As discussed in Section 2.2.3.1, the CM generated during mill demolition was graded to infiltrate storm water across the 32 acres on which it was placed. While some localized ponding was observed within the CM area during unusually heavy rain events, no runoff from the CM area was observed while the CM was in place. Likewise, precipitation falling on the unpaved areas where CM was not placed (e.g., along shoreline) also infiltrates. A small, paved area associated with the covered loading docks on the west side of the remaining warehouse building is serviced by three catch basins which combine to discharge to the nearby embayment 10; however, this paved area is largely covered by overhanging building structure and, therefore, receives very little rainfall and produces negligible runoff. Three additional catch basins 11 exist west of the warehouse building and combine to discharge to the nearby embayment. They were originally retained during demolition for emergency storm water management. However, their elevation was previously established by asphalt that has now been removed. As a result, while the CM was in place, that surrounding area is now lower in elevation than the catch basin grates, and it generally infiltrates rather than running off into the catch basins. Following the CM removal action in 2020, K-C imported and placed highly permeable, non-silty sand (“Parcel O sand”) across the 32 acres from where CM was removed. The imported sand was graded with gentle slopes including a broad north-south-aligned depression approximately 200 feet inland from the shoreline to ensure that any runoff from the sand surface did not flow overland into the East Waterway. As part of the third IA, a new storm drainage system was installed to convey stormwater to new treatment infrastructure. In addition, historical stormwater outfalls A and M were reconstructed as part of the third IA for discharge from the new stormwater system (Landau, 2024). Additional information regarding these activities is provided in Section 4.8. Most of the ground surfaces within the City’s Utility Property at the northern end of the Upland Area remain paved and serviced by a series of on-property storm water catch basins. Runoff entering those catch basins is conveyed via underground pipes to and infiltrated through a pair of drainage swales located along the northern and southern edges of the property. The northern swale also serves portions of Naval Station Everett’s paved parking areas. The City filled the southern swale in December 2020 and will eventually pave it, as discussed in Section 4.4. 10 Identified as Pipe A for purposes of the Second IA (Aspect, 2021). 11 Catch basins B1, B2, and B3 as identified for purposes of the Second IA (Aspect, 2021).