3800 RIVERFRONT BLVD 2025-07-23 - Laserfiche WebLink

1 rI 1 1 1 1 1 1 1 1 i Consent Decree Exhibit C • Stormwater will be collected for conveyance off -site for discharge. Where conveyance of subdrainage from landscaped areas to the stormwater system is impracticable, release of subdrainage to the subsurface will be accepted, as long as the gas collection system is not compromised by such drainage. • Stormwater conveyance piping located on the Site is required to have leak -tight joints in order to minimize infiltration of stormwater into subsurface soils and reduce leachate generation. • Restrictions against infiltration of collected stormwater into Site subsurface soils are included to minimize leachate generation. Condensate drained from landfill gas collection piping will be discharged to the leachate collection system. Where impracticable to pipe this liquid directly to the leachate collection system, condensate will be allowed to drain into subsurface soils for eventual collection in the leachate collection system. • A one-time sampling of the shallow aquifer will be performed to determine if there are zones where shallow aquifer quality has the potential to cause an exceedance of cleanup levels at the point of compliance in the deep aquifer if migration from the shallow to deep aquifer were to occur. Based on the results of this study, zones of the Site may have restrictions on the type of piling (deep foundations) that future development may use. Augercast piling will be required where it is shown that penetration of the aquitard could potentially result in deep aquifer cleanup level exceedances. • Institutional controls are required preventing groundwater withdrawal other than for leachate collection or monitoring. • Compliance monitoring and contingency plan commitments are required. Initiation of compliance monitoring is required before pile installation can commence. Direct Contact Pathway: • Development areas are required to provide cover of subsurface soils. Covers will include a minimum of 2 feet of clean soil, pavements, building slabs or a combination of these. • Clean backfill, meeting current WSDOT/APWA Specification #9-03.12(3) or equivalent, in utility corridors with geotextile separation from existing materials is required to prevent contact with landfilled materials during maintenance activities. • Security fencing (locked gates, adequate height, etc.) and signage is required to prevent public access to undeveloped portions of the Site. • Institutional controls are required to govern maintenance of developed area covers, and compliance with health and safety requirements for penetrations of that cover. • Institutional controls prohibiting private residential ground -level ownership of landfill property are required. • Construction methods to contain risk of direct contact to landfilled materials and site groundwater within construction zones are required. They include: * Dust and odor controls * Erosion and surface water controls FINAL - March 2001 6-3 Everett Landfill Tire Fire Site Cleanup Action Plan 1