10/30/2002 Env Bd Packet - Laserfiche WebLink

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Agenda Item 5B Environmental Board Meeting Date: October 30, 2002 Topic: Lake Drive Carwash /CUP /Site Plan Review Background: The Environmental Board reviewed this site plan at the August 28, 2002 Environmental Board Meeting. The following are the comments and recommendations from that meeting concerning the proposed car wash: The Environmental Board made the following recommendations concerning the Car Wash Proposal on Lake Drive: The high water elevation of the large basin on the west is indicated at 897.2. The West infiltration basin on the site is proposed to have a base elevation of 897.0. There needs to be at least a 3 -foot separation between the bottom of the basin and the seasonally high ground water level. The applicant should demonstrate that adequate separation exists or redesign the improvements to achieve this separation. This 3 -foot separation is consistent with MPCA's guidelines for septic systems. In addition, given this is a light industrial site, the applicant should submit a soil sensitivity test for designed systems to evaluate potential effects on groundwater. If runoff water could contain a significant concentration of soluble pollutants, infiltration basins should not be used. Proximity to drinking wells must be evaluated. Basins should be at least 150 feet from any wells and be situated at least 10 feet down - gradient and 100 feet up- gradient from building foundations . Basins should be designed with pretreatment features such as grit chambers, swales with check dams, filter strips, or sediment fore bays. Traps should be a component of any infiltration system. Desirable side slope dimensions of the basin should be no greater than 3H: 1V. Flatter slopes are preferred. The basin water depths should be no more than 2 feet to eliminate compaction to the basin, and the ponding time no more than 72 hours. A desirable length to width ratio for an infiltration basin should be 3:1 or greater. Overflow should include check dams, level bars or other structures to ensure sheet washing. Access to the site for maintenance should be addressed. . Swale areas should be kept to a 1% to a 2% slope. Recommend that the design of these swales be modeled after Met Council/Barr engineering design standards. . Sequencing Suggested (Attachment and Construction Sequencing Plans (BMP's) should be submitted. guidelines are in the Minnesota Urban Small Sites BMP Manual. 10).