08/29/2007 Env Bd Packet - Laserfiche WebLink

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ENVIRONMENTAL BOARD MEETING JULY 25, 2007 Rice Creek Watershed District (RCWD) has proposed a number of changes to the Stormwater Management Plan. The RCWD invites submission of written comments to the proposed changes by August 1, 2007. Connie Taillon and Jim Studenski will be submitting comments on behalf of the City of Lino Lakes. Ms. Taillon was present to review RCWD's proposed changes and City comments. Page 1. Rule C: Stormwater Management Plan. Ms. Taillon went over the first page of her memorandum regarding proposed changes. Current: 2.5 acres. Proposed: Reduce exemption to new development, redevelopment, linear projects or additions from 2.5 acres to at least 1 acre in size. City comment: The City of Lino Lakes comment will be to add language that would define a one acre site. Page 2. Water Quality and Water Control. Current: Impervious surface runoff is currently .34 inches in 72 hours. Proposed: Under the new rules infiltration basins are required to draw down 2.8 inches within 48 hours from end of a storm event. City comment: Is RCWD's requirement of infiltration for the two year storm event for proposed conditions only? Why is RCWD not requiring existing volumes vs. proposed? In types A & B soil areas RCWD is proposing to infiltrate to pre - settlement runoff. Ms. O'Dea asked how Ms. Taillon is comparing runoff. Ms. Taillon stated they are only capturing the excess over and above the existing. She stated basins would more than likely be made smaller and onsite rather than regional and possibly offsite. Ms. O'Dea questioned alternatives to the existing. Ms. Bor stated the developer comes in and if they are using pre - existing conditions what does that mean to them? Ms. Taillon stated RCWD states not to look at existing conditions, they are saying design a system to infiltration 2.8 inches that goes to that basin with no runoff. Ms. Taillon suggested that we take this requirement out in all cases and suggested using a volume requirement. She stated we should try to mimic the existing conditions and not just look at proposed. Ms. Taillon stated the design based on existing conditions is the suggestion from the city. Page 3. Peak Flow Management. Current: Rates not to exceed "pre- project" runoff rates for the critical 1 -year or 2 year and 100 year frequency events. Proposed: In types A & B soils rates not to exceed "pre- settlement" runoff rates for the critical 2 year and 100 year frequency events for sites no covered by impervious surfaces in pre - existing condition. City comment: Would like clarification for rate control. Is it the site as a whole or is the rate to be met at every point that it discharges off the site. Page 4. Flood Protection for Structures. City comment: Define table as to local detention basins and wetlands. Ask why the RCWD lowered the low floor elevation. Infiltration basins are designed to run dry. 2 DRAFT MINUTES • • •