7000 HARDESON RD 2020-06-05 - Laserfiche WebLink

Minimum Requirement #2: Construction Stormwater Pollution Prevention A Construction Stormwater Pollution Prevention Plan has been prepared for the project. The project will be obtaining coverage under the Construction Stormwater General Permit. Minimum Requirement#3: Source Control of Pollution Applicable source control measures have been included on the TESC plans. The site is covered under an Industrial Discharge Permit with the DOE which has specific requirements for source control measures and monitoring requirements. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls There will be no changes to the existing flow path, outfall locations, pollutant loading or runoff characteristics. Minimum Requirement #5: On-Site Stormwater Projects only triggering minimum requirements one through five are required to use List#1 or comply with the performance standard. The following discusses the feasibility of List#1 compliance. LAWN AND LANDSCAPED AREAS The project will comply with all requirements of BMP T5.13: Post-Construction Soil Quality and Depth. • Soil Retention:Topsoil from the areas of tree removal and planting will be removed and stockpiled and reapplied within the areas of landscape restoration. • Landscape areas which will be disturbed as part of this project will be restored with 8-inches of topsoil which has been amended to meet soil quality requirements. • 2-inches of organic mulch will be added to the top of the disturbed planting areas. ROOFS The List#1 BMPs for roofs do not apply this project as there are no roofs involved in the work. OTHER HARD SURFACES: • Full Dispersion in accordance with BMP T5.30: Full Dispersion The site is currently more than 45% impervious. There is no onsite forested/native planting area downstream of the project site. There is no portion of the site which could be made to meet meet the Full Dispersion criteria. • Permeable pavement in accordance with BMP T5.15: Permeable Pavements, or Rain Gardens in accordance with BMP T5.14A: Rain Gardens, or Bioretention in accordance with BMP T7.30: Bioretention Cells, Swales, and Planter Boxes. o Permeable Pavement- The project consists of narrow strips of pavement repair adjacent to existing trench drains. The pavement has settled in relation to the top of the trench drain and is being reconstructed to direct surface water into the existing trench drains. Permeable pavement is infeasible in areas like this where there is sheet flow from up-gradient impervious area which is greater than the pervious pavement area. The areas of concrete panel replacement are also not good candidates for permeable concrete as this is an industrial maintenance facility and spill and source control measures would become ineffective on permeable pavement. Merrill Creek Stormwater Code Compliance—Community Transit 4