HomeMy WebLinkAbout05- engineered stormwater reportMinimum Stormwater Management Requirements
Suzanne Carlson’s Property
Port Townsend, WA 98368
Jefferson County Parcel 001061005
8.62 Acres (375,000 ft2)
Prepared by: Everett A. Sorensen, P.E.Evergreen Engineering Services715 Grant St; Port Townsend, WA 98368ev_sorensen@hotmail.com 360-821-9960August 25, 2022
Minimum Stormwater Requirements 1 – 9 as Outlined in the Department of Ecology’s Stormwater Management Manual for Western Washington
Minimum Requirement (MR) #1: Preparation of Stormwater Site Plans (contained herein)
MR #2: Construction Stormwater Pollution Prevention and Temporary Erosion & Sediment Controls:
Element 1 (E1): Preserve Vegetation/Mark Clearing Limits prior to clearing topsoil and vegetation — We propose to clear a driveway and home site totaling less than 10,000 SF of the 8.6-acre parcel (<2.7%).
E2: Establish Construction Access - The existing access point at the SE corner of the subject parcel will become the future driveway and construction access for all stages of construction. Construction vehicles shall be free of excess mud upon leaving site.
E3: Control Flow Rates – There are no existing concentrated surface flows at the site. Stormwater run-off shall remain dispersed throughout the site.
E4: Install Sediment Controls -- When additional surfaces are disturbed during construction, install a surface sod berm silt barrier or silt fence downhill of the area wherever ample vegetated downhill surfaces cannot be preserved.
E5: Stabilize Soils -- Stabilize temporarily exposed soils by hand-watering and establishing living cover with grass and ground-covering vegetation as quickly as possible. Hand-water soil piles as needed during dry season. Divert stormwater discharges away from soil piles during wet season
E6: Protect Slopes -- The existing drainage ravine at the far southwest corner of the parcel shall be preserved.
E7: Protect Drain Inlets -- Not Applicable. There are no nearby stormwater drain inlets or catch basins needing protection.
E8: Stabilize Channels and Outlets -- Not applicable for this site.
E9: Control Pollutants -- Prevent discharge or release of all pollutants, including motor oil and construction debris. Instruct all personnel as to this policy.
E10: Control De-Watering -- Not applicable for this site; no dewatering expected.
E11: Maintain BMPs -- All Temporary Erosion & Sedimentation Control Features must be inspected regularly and maintained & repaired as needed.
E12: Manage the Project -- Assess conditions regularly and adjust construction stormwater management features as needed.
E13: Protect Low Impact Development BMPs -- Avoid unnecessary ground disturbances.
MR #3: Source Control of Pollution -- Prevent discharge or release of all pollutants, including motor oil and construction debris. Instruct all personnel as to this policy. After construction is completed, all unsurfaced ground shall be landscaped with vegetation and/or rockery. Parking areas shall be maintained by immediately cleaning any releases of oil, other hydrocarbons, or chemicals and by collecting debris regularly.
MR #4: Preservation of Natural Drainage Systems and Outfalls — The existing drainage ravine at the southwest corner of the parcel shall be preserved.
MR #5: On-site Stormwater Management — disperse and infiltrate stormwater on-site to the maximum practical extent.
MR #6: Runoff Treatment -- Runoff from the proposed driveway would be treated naturally be vegetated surfaces downhill from the driveway.
MR #7: Flow Control – Control of stormwater flow shall be achieved by routing run-off through existing vegetated surfaces which will dampen sheet flow and encourage on-site infiltration.
MR #8: Wetlands Protection -- Not applicable; no wetlands present.
MR #9: Operations and Maintenance — Restore and maintain native vegetation to provide stormwater flow attenuation and natural treatment.