11831 AIRPORT RD WHOLE SITE FILE 2020-01-21

Design Codes and Loadings The Contractor shall prepare and submit a structural design of the detention tanks including drawings and calculations prepared by (or under the direct supervision of) a licensed Professional Engineer registered in the State of Washington in the branch of Civil or Structural Engineering. Each drawing, and the cover page of the calculations, shall carry the Professional Engineer's seal, signature, and date. The structural design and detailing shall be conducted in accordance with the following codes: The requirements of Section 7-08.3 and 7-04.3 shall apply to detention tanks. DETAILING REQUIREMENTS Maintenance access structures and components, including but not limited to risers, hatches, lids, manholes, and their supports shall be included in the tank structural design. Examination Prior to installation of the precast detention tanks, the Contractor shall examine the tanks for compliance with dimensional and size requirements, including installation tolerances, true and level bearing surfaces, and other conditions affecting performance of prefabricated units. Any dimensional sizes and finishes not in accordance with the requirements shall be corrected by the Contactor, prior to installation. Excavation for Tank and installation Excavation and backfill for the detention tanks shall be per Section 2-09 of the Standard Specification. For detention tanks, the structure excavation shall be calculated to the neat line shown in the Plans. Temporary shoring shall be provided by the Contractor in accordance with Section 7- 08.3(1)B of the Standard Specifications. Extra excavation or over break shall not be allowed. The method of shoring shall be submitted at the pre-construction meeting for approval. Backfilling should be done after tank is completely assembled making certain to compact the backfill progressively from the bottom to the top surface. Compaction of backfill shall be in accordance with Section 2-03.3(14)C, Method C, of the Standard Specifications. All joints shall be watertight. Erection The Contractor shall erect and backfill structures in accordance with the erection sequence specified in the shop drawings approved by the Engineer. 7-05.4 Measurement Section 7-05.4 is supplemented with the following: New Solid Locking Lid will be measured per each new solid locking lid installed on an existing catch basin or manhole. "Wetland Treatment Catch Basin" shall be measured per each. "Biofiltration Catch Basin " shall be measured per each. Catch Basin Type 2, 48 In. Diam. with Oil Pollution Control Riser will be measured per each. Swift Green Line—Corridor Stations Special Provisions SP99 May 2017