11831 AIRPORT RD WHOLE SITE FILE 2020-01-21

Infiltration Chamber Gallery Number of chambers (MC3500):13 (approx. 100-feet long) Number of end caps: 2 Non-woven geotextile for Infiltration Gravel Surround: approx. 390 square yards Gravel Backfill for Drywells: approx. 410 tons Structure Excavation Class A: Approx. 270 cubic yards Various couplings, elbows, and manifold items Inspection Ports and cover boxes 7-05.2 Materials Section 7-05.2 is supplemented with the following: Wetland Treatment Catch Basin Wetland treatment catch basin shall consist of a Modular Wetland Systems Linear Systems Vault(s) model MWS-L-4-4 or an approved equal. A substitute material will be considered equal if the material has the same function and meets similar specifications as approved by the Engineer. To be approved as equal, the wetland treatment catch basin shall: • Meet the Ecology General Use Level Designation (GULD) certification. • Shall be sized to meet Ecology Enhanced Water Quality Treatment requirements for a runoff from a contributing area of 6,780 square feet of pollution generating impervious roadway surface. • Exterior dimensions shall not extend beyond the footprint of the facility shown in the plans. • Pretreatment chambers shall use replaceable cartridges that contain non-proprietary filter media. • Pretreatment filter cartridges shall operate at a loading rate not to exceed 1.9 gallons per minute per square foot area. • Treatment chambers shall be open chambers with the ability to support plants. • Treatment chambers shall use media that does not require replacement over the life of the facility. • Treatment chambers shall achieve 80 percent removal of total suspended solids. • The structure shall be constructed of concrete with a minimum 28 day compressive strength of 5,000 psi, reinforcing per ASTM A 615, Grade 60, and supports H2O loading as indicated by AASHTO. • Each chamber shall have access hatches for maintenance in accordance with WISHA standards and sized to allow removal of all internal components without disassembly. • Structure knockouts shall be provided to accept pipes of the size, material, and elevation shown in the plans. • Treatment media shall consist of ceramic material produced by expanding and vitrifying select material in a rotary kiln. • Treatment media shall meet the requirements of ASTM C330, ASTM C331, and AASHTO M195. Aggregates must have a minimum 24-hour water absorption of 10.5 percent mass. Media shall not contain any organic material. Swift Green Line—Corridor Stations Special Provisions SP94 May 2017