2300 KASCH PARK RD 2025-07-28 - Laserfiche WebLink

Project Overview This Stormwater Runoff Control Analysis has been prepared to address stormwater control for reconstruction of an existing asphalt paved driveway entryway and a new on-site driveway connecting two existing paved areas. This work is being performed as a supplement to the work at Kasch Park Base that was permitted in 2009. The entryway reconstruction work consists of removing the existing asphalt pavement and concrete crosswalk at the westerly driveway entrance into the Kasch Park Base and replacing it with concrete pavement. The area that is impacted is 11,465 square feet. To facilitate the repaving at the west entryway,on-site bus circulation must be modified to allow temporary use of the east driveway. This requires that a new vehicle connection be made between two existing on-site paved areas. The internal drive aisle will be constructed over an existing landscape and sidewalk strip. The drive aisle work impacts 705 square feet of area. In addition to the work listed above,a new curb is proposed for a small portion of the west edge of the bus layover area to help contain the buses to the pavement. Tire wear in the adjacent lawn landscape strip shows that bus drivers have a tendency to drive off the pavement in this section. Two new catch basins will be constructed onto existing storm drain lines to collect the drainage that will be restricted by the curb. No changes to the paved area will be made. See the enclosed Vicinity Map of the work areas. Existing Conditions The work discussed here covers three separate areas on the existing Kasch Park Operating Base property located at 2300 Kasch Park Road. All three areas are currently developed and storm drainage controls are installed and were designed under a multi-phase master planning exercise that took place in 1993-1994. This work included development of a storm drainage runoff control system to manage a full operating base build out. The entire parcel consists of 20 acres. The master plan accounted for a full build-out of 13.1 acres of impervious surfaces,5 acres of pervious surfaces,and the remainder consisting of wetlands and wetland buffer. The stormwater system includes catch basins and conveyance pipe that collect site runoff and direct it to a flow splitter leading to an oil/water separator or directly to the detention vault. The detention vault has been sized for 13.1 acres of impervious and 5 acres of pervious. From the outlet of the detention system flow control structure the full two-year release rate is pumped up to a bioswale to provide water quality treatment. The outlet from the bioswale and the greater than two-year detention system flows discharges to a culvert in the far south east corner of the site. The stormwater controls were sized and built for the 13.1 acres of impervious and 5 acres of pervious. Currently the site consists of only 12 acres of impervious surface rather than the full 13.1 acres of impervious that the system is sized for. Community Transit Kasch Park Base �,