3800 RIVERFRONT BLVD 2025-07-23 - Laserfiche WebLink

Consent Decree Exhibit C 1 To prevent atmospheric intrusion into the extraction pipes, a low permeable barrier is required in open space areas. This is assumed to be the same as the hydraulic barrier required for groundwater protection. In some areas of thick fill placement above collection pipes, the fill thickness may provide the barrier to atmospheric intrusion. Pavement that meets specified low -permeability (less than or equal to 10- 5 cm/sec) criteria will operate effectively as a low permeable barrier for gas system purposes. Utilities, manholes, and catch basins in the pavement, open space and undeveloped areas will be coated, sealed or booted to reduce the likelihood of landfill gas intrusion. The general public will be restricted from accessing undeveloped areas. There may be enclosures such as utility manholes in undeveloped areas. They will have the same coating and sealing requirements as manholes in the pavement or open space areas. All utility vaults or manholes in undeveloped or developed areas will be accessible only to trained, qualified personnel using confined space entry procedures that include monitoring immediately prior to entering the enclosed space, and will be labeled accordingly. Light fixtures, fence posts and similar structures would either be finished above the underlying gas barrier or, if penetrating the gas barrier, be internally sealed and booted to the barrier layer to preclude intrusion of LFG. Piling or foundations that would penetrate the barrier layer would be booted or sealed to the barrier layer. Temporary trailers, tents or similar enclosures that might be set up over pavement or open space areas would include continuous methane monitors set to sound an alarm if the concentration of methane exceeded 1,000 ppm. No overnight camping would be allowed at the site. • Special consideration will be given to boundary conditions between developed and undeveloped areas to preclude excessive air intrusion into the refuse from the active collection system along this boundary. • Phased active landfill gas controls will be designed and constructed such that, in the future when landfill gas generation rates have dropped to a level that renders the active system unnecessary, the landfill gas controls may be operated as a passive venting system, without vacuum extraction. • The Owner/Developer(s) will contract with a single, licensed professional to perform operations, reporting, maintenance and repairs on all landfill gas control system components installed in the developed areas of the Site. Groundwater Pathway: • Continued operation and maintenance of the Leachate Collection System will be required until such time that the shallow aquifer may be proven in compliance with chemical cleanup criteria. • To minimize infiltration of rain and irrigation water to the shallow aquifer, a hydraulic barrier is required to be constructed in developed areas. This hydraulic barrier requirement can be met through the installation of pavement and building structures. In landscaped areas, this hydraulic barrier requirement can be met through installation of a membrane, low permeability soil layer or other material with a permeability similar to asphalt pavement. FINAL - March 2001 6-2 Everett Landfill Tire Fire Site Cleanup Action Plan I 1 1 1 1 7 L n F 1 [C] 1 1 1 1 1 I