Detailed plans shall be submitted for the district’s review, which provide the location, size, type and direction of flow of the proposed sewers and the connection with existing sewers. These plans shall be separate from water plans and shall conform to district drafting standards.
All sewer system design submittals with drainage basins serving to Alderwood Water and Wastewater District for conveyance to King County facilities requires King County design review and acceptance prior to acceptance by Silver Lake Water and Sewer District.
Project plans should have a horizontal scale of one inch equals 50 feet and a vertical scale of one inch equals five feet. Plan and profile views for any given section of gravity sewer or force main shall be drawn on the same sheet. Plans and profiles shall show:
(1) Locations of streets, rights-of-way, existing utilities, and sewers.
(2) Ground surface, pipe type, class and size, manhole stationing, invert and surface elevation at each manhole, and grade of sewer between adjacent manholes. Elevations shall be based on the NAVD 88 datum, with a conversion factor to the NGVD 29 datum noted on the plans, as further described in the general drafting standards. All manholes shall be numbered on the plans and correspondingly numbered on the profile. Where there is any question of the sewer being sufficiently deep to serve any residence, the elevation and location of the basement floor, if basements are served, shall be plotted on the profile of the sewer that is to serve the house in question. The developer shall state that all sewers are sufficiently deep to serve adjacent basements, except where otherwise noted on the plans.
(3) All known existing structures, both above and below ground, which might interfere with the proposed construction, particularly water mains, gas mains, storm drains, overhead and underground power lines, telephones lines, and television cables.
(4) All utility easements.
(5) District approval block.
(6) Details in scale drawings, which clearly show special sewer joints and cross sections, and sewer appurtenances such as manholes and related items.
Construction of new sewer systems or extensions of existing systems will be allowed only if the existing receiving system is capable of supporting the added hydraulic load.
Collection and interceptor sewers shall be designed for the ultimate development of the tributary areas.
Sewer systems shall be designed and constructed to achieve total containment of sanitary wastes and maximum exclusion of infiltration and inflow.
Computations and other data used for design of the sewer system shall be submitted to the district for approval.
The sewage facilities shall be constructed in conformance with the current WSDOT Standard Specifications for Road, Bridge, and Municipal Construction, and current amendments thereto, revised as to form to make reference to local governments, and as modified by the district’s requirements and standards.
Material and installation specifications shall contain appropriate requirements that have been established by the industry in its technical publications, such as ASTM, AWWA, WEF, and APWA standards. Requirements shall be set forth in the specifications for the pipe and methods of bedding and backfilling so as not to damage the pipe or its joints, impede cleaning operations and future tapping, nor create excessive side fill pressure or deformation of the pipe, nor seriously impair flow capacity.
All sewers shall be designed to prevent damage from superimposed loads. Proper allowance for loads on the sewer because of the width and depth of trench should be made. When standard-strength sewer pipe is not sufficient, extra-strength pipe shall be used.
After all other work is completed and before final acceptance, the entire roadway, including the roadbed, planting, sidewalk areas, shoulders, driveways, alley and side street approaches, slopes, ditches, utility trenches, and construction areas shall be neatly finished to the lines, grades and cross sections for a new roadway consistent with the original section. [Res. 735 § 1, 2017.]