1505 112TH ST SW 2018-01-02 MF Import

NgIrr,ative The project site is located on a parcel of land 62,623 square feet (1.44 acres) In size. Approximately N086 square feet (0.73 acres Including landscaping) of the overall parcel Is to be developed for a vehicle Inspection station. The project site Is located on the north side of 112th St. S.W. west of its Intersection with Highway 99In Everett. Washington. The project site is bounded by vacant lots on the north and cost. 112th St. S.W. on the south, and a single family residence on the west. The location of the project site Is shown on the attached sheet C1.2 of the civil plans. The project site Is occupied Vy two single family residences, with basements, one close to 112th St. 5A and one In the north portion of the site. Both structure: will be removed from the site as a part of development /. gravel drlvew.ry rune along the west property line to the northern single famly residence. The gravel driveway will be removed as a part of development and replaced with a berm to prevent drainage from crossing to the adjacent property on the west. The rest of the site Its covered with several trees and brush. The site Is underlain by about three to four feet of loose to medium dense silty sand with gravel. Beneath this layer, a medium dense grading to very dense silty sand with gravel (glacial till) was encountered to a depth of twelve feet (limits of exploration). The site has a topographic relief of 20 feet. 51te Oradea are generally flat except for the north facing slopes along the southern perimeter of the Otte. These north elopes are Inclined at about 2H:1V to 3H:1V. The site drains r.outhwestery to a wetland area. The wetland drains to an existing 12" storm pipe located at the southwest comer of the project site. The existing I.E. of the 12" cone. culvert at the wetland outlet Is 508.2. The existing 12" cone. culvert drains to the west under an adjacent driveway at 0.88%. �� , „ k, ,. Culiff ne �('90 1 This site is the proposed location for vehicle emission Inspection station. This will be a 'drive - through" type facility. The Inspection building will be of woad frame with a slab on grade floor. Remaining portions of the site will be surfaced with asphaltic concrete parking and drive areas with some Interior landscaping, The station and site Improvements will be built In one phase. The project site is located In the Swamp Creek drainage basin. Storm drainage will be collected onsits and detained In an underground vault. Department of Fisheries criteria was ueed to design the amount of storage In the vault. The rate of discharge Is restricted to one-half the 2 yr. predeveloped rate of discharge (with a 1" orifice) during a 2 year storm and, to the 10 yr. predeveloped rate of discharge (with a notched weir) during a 25 yr. storm. The combined discharge during a 25 yr. event will not exceed As 10 yr. predeveloped event. A baffle -type oil/water separator has been placed between the detention vault and the bloswale. It has been designed according to current City of Everett requirements. A 168.5bloswale will be provided with a 1.5' bottom width. Offsite drainage from the east will be able to continue draining unrestricted to the west via a 12" Otorm pipe and therefore its effect nos been Ignored In the calculations. Off6U drainage from the north is considered relatively minimal and will be allowed to cycle through the detention system. Its effect on detention volumes has been ignored In the calculations. 8y allowing this to happen the vault may fill slightly faster however, the effect to