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kts pie t,Qcer4-d <br />w ,th 3 -1;,5o Aev;sAe" <br />10. DESIGN CALCULATIONS - Appendix A includes the hydrographs for the 2, 10 and <br />100 year storms as routed through the drainage system. Other appropriate calculations <br />are also provided in the appendix. <br />11. PROPOSED DRAINAGE SYSTEM - The proposed drainage system is composed of <br />the two collection systems, two wet cells , one water quality pond and two underground <br />detention storage's for 10 and 100 year storms. The collection systems involves standard <br />catch basins to two vaults which compose the wet cells of the wet pond. The wetpond <br />volume for each development exceeds the City standard requirement . The wet pond <br />outlets are restricted to a I'minimum orifice size. Drainage volumes above the outlet <br />value storm will be diverted to the piped storage systems by separate overflow systems. <br />This system meets the Ecology design standard for the 10 and 100 year release rate and <br />150% of the detention volume. Flows from the wctpond and detention systems arc joined <br />together before discharge to the system to the east. <br />12. CONSTRUCTION SEQUENCING - The two developments are not being <br />constructed by the same developer nor on the same schedule. The Burger King project <br />will probably be constructed first in that this project has completed the SEPA process and <br />will submit plans for construction permits before the Les Schwab project. To address the <br />issue of scheduling concoction the plan will be to construct the entire wetpond for both <br />projects in the first construction permit (Burger King). The underground storage and <br />release rate controls for each project will be constructed when that development is built. <br />This construction sequencing will allow the wetpond to be functioning during <br />construction of the second project and allow establishment of treatment vegetation in the <br />initial construction. Erosion control during the second construction project will be <br />separate from the wetland treatment system in order not to damage that system. <br />13.OPERATION AND MAINTENANCE - Operation and maintenance of the drainage <br />system is separated into two areas. Each lessee shall be responsible for their separate wet <br />cells, inlets and outlets, control structures and underground storage. Maintenance of the <br />wetpond will be separated by the physical location of where the work needs to be done. <br />This system will allow clear determination of responsibility if enforcement of <br />maintenance is required. <br />14. LES SCHWAB CONSTRUCTION REQUIREMENTS - The entire sites drainage <br />system will not be complete until the northern portion of the site, Les Schwab, is <br />constr acted. The total system elements with the construction phase is shown below along <br />with the responsible developer. <br />.,_ _u 11:._L...... il...:nnnn Cvarem Flements <br />Table <br />ur er Itin <br />Les Sc wa <br />Item <br />Open Cell <br />1283 c <br />1058 c <br />2250cfR 'd. <br />81x27'x6' <br />81x22'x6' <br />Wet nd <br />X <br />Wet rid Release S stem <br />X <br />Piped Storage Release <br />X <br />Control <br />Underground Piped Storage <br />2701f. <br />2101f <br />4801f R 'd. <br />From the table it is clear that all elements of the system except for the 1058 cf of open <br />cell and 210 If of 48" diameter pipe shall be constructed in the first phase of this property <br />90-016 5 Two Rivers Fmgineeaing <br />