6101 23RD DR W NORPRO 2025-07-29

Minimum Requirement#1: Stormwater Site Plan Preparation ' A stormwater Site Plan (SSP) shall be prepared for City review and approval. Response:A stormwater site plan has been prepared for the development. The stormwater site plan includes the design drawings and this report. Minimum Requirement#2: Construction Stormwater Pollution Prevention I All new development and redevelopment are responsible for preventing erosion and discharge of sediment and other pollutants into receiving waters during construction. Response: The 12 elements of a SWPP are addressed in the Construction SWPP section of this ' report. A full Construction SWPPP will be prepared for the site before construction begins. Minimum Requirement#3: Source Control of Pollution , All known,available and reasonable source control BMPs shall be applied to all projects. Source control BMPs shall be selected, designed, and maintained according to Volume IV of the 2010 Manual. ' Response: Roof runoff will be kept separate from runoff from pollution-generating surfaces to the maximum extent possible. ' Minimum Requirement#4: Preservation of Natural Drainage Systems and Outfalls Natural drainage patterns shall be maintained, and discharges from the project site shall occur at the natural location, to the maximum extent practicable. The manner by which runoff is discharged from the project site must not cause a significant adverse impact to downstream receiving waters and down-gradient properties. I Response: The property drains to two separate basins. The proposed basin sizes will match the existing basin sizes. The Powdermill Gulch Creek basin will connect to the city drainage system within 23'd Drive W. This drainage system discharges to an existing detention pond with an existing outfall into Powdermill Gulch Creek. The Narbeck Creek detention tank outlet will connect to an existing conveyance system which will route stormwater to an existing storm outfall at the natural location in Narbeck Creek. Minimum Requirement#5: On-site Stormwater Management On-site Stormwater Management BMPs shall be provided to infiltrate, retain, and disperse stormwater runoff onsite to the maximum extent feasible without causing flooding or erosion impacts. Response: On-site stormwater management with regards to infiltration and stormwater retention is very limited on-site due to steep slopes surrounding the property. In the developed condition, soil quality and depth requirement shall be met per BMP 12.20. ' Minimum Requirement#6: Runoff Treatment The following projects require design and construction of stormwater treatment facilities (see Table 2.1): • Projects in which the total of effective, pollution-generating impervious surface (PGIS) is 5,000 square feet or more in a threshold discharge area of the project. , 6/16/2011 Stormwater Site Plan Page 8