Agenda - Public Works Committee - 07/15/2008

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CASE #'1 CONSIDER ESTABLISHING TOPSOIL REQUIREMENTS IN NEW SUBDIVISIONS By: Tim Himmel', Assistant City Engineer Background: Ramsey has been identified as one of the largest users oinon-consumptive water in the metro area. In .an attempt to reduce the quantity of water used annually, the City has considered and implemented various conservation measures over the years. One item that has been discussed numerous times is a topsoil requirement for new subdivisions. This topic was most recently discussed at the January 15,2008 Public Works Committee meeting. Staff left that meeting with some direction for further investigation, specifically: L Cost breakdown of differing soil types/additives (organics and clay) 2. Enforcement 3. Review the potential for a City compost site Observations: The sandy soils found throughout the City have low water retention capacity, thus large quantities of water are used each year for irrigation. Generally speaking, the topsoil in the City consists of silty sand, with minimal organics and clay content. One way to increase soil moisture holding capacity would be to require a topsoil specification, which includes clay and organics, over all landscaped areas in new developments. Based upon conversations with some suppliers the following costs are associated with varying blends of topsoil: . Unscreened black dirt (existing virgin material) $6 - $12/CY . Screened black dirt $9 - $20/CY . Screened & blended black dirt (adding clay and organics) $12 - $26/CY . As you can see there is great variability in cost across the spectrum of options, and this is for the material only (trucking would be an additional expense). There are also factors associated with the quantity of material to be purchased, with discounts for larger orders. The higher end of this price range was quoted from suppliers which typically deal in smaller quantities for individual property owners doing spot lawn repairs or creating gardens. Using a higher grade topsoil on an average quarter acre lot would cost approximately $350 - $500 more. The thought is to require the installation of this new topsoil specification at the time of final grading; following construction. The mass grading operations of the overall site could be accommodated with the respread of 4" of on~site topsoil and site stabilization. Areas reserved as open space should be required to include the higher grade topsoil as they would potentially be in the final state. All other areas would be allowed to utilize the on-site topsoil as a temporary means until construction is completed and the final grade is established: Handling it this way improves the overall final product in that this new topsoil would not be compacted by hea:vy equipment and material storage, erosion control concerns could be reduced (stockpiling and 43