Agenda - Council - 01/13/2009 - Laserfiche WebLink

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INTRODUCE ORDINANCE ESTABLISHING TOPSOIL REQUIREMENTS; CASE OF CITY OF RAMSEY By: Tim Himmer, Assistant City Engineer Chris Anderson, Environmental Coordinator CASE # 1 Background: Ramsey has been identified as one of the largest users of non - 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. There have been several iterations of a topsoil requirement considered by both the Public Works Committee and the Environmental Policy Board, dating back to January of 2006. At the July 15, 2008 Public Works Committee meeting, Staff was directed to prepare a topsoil ordinance requiring a minimum of four inches of topsoil, meeting MnDOT specification 3877.2C (premium topsoil borrow), in landscaped areas of all new developments (residential and commercial/industrial). After further research, Staff modified the recommended topsoil specification slightly. The modifications will more specifically address the soil conditions found in Ramsey by restricting the allowable sand content and will also be more in line with surrounding communities that have a similar requirement, such as Blaine; St. Francis and Andover. MnDOT's specification includes a range of allowable sand content (25 -65 %); the proposed ordinance will limit the allowable sand content to a maximum of thirty -five percent (35 %). 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. Therefore, establishing a topsoil requirement should increase the soil moisture holding capacity of the soil, due to the higher amounts of clay and organics required. The topsoil requirement would be triggered by the issuance of a building permit for new construction of a principal structure. The benefits realized from requiring topsoil would include: reduced demand for non - consumptive water, improved recharge of aquifers and lower utility bills for residents as a result of less frequent watering. The proposed ordinance requires the installation of a minimum of four (4) inches of topsoil over all exposed areas not improved with buildings and paving, excluding natural areas that are left undisturbed. The topsoil requirement would apply to any lot, in any zoning district, being improved with the construction of a principal building. Topsoil will be defined as: "Black dirt composed of unconsolidated material, with a sufficient amount of organic matter to establish a suitable foundation for vegetative growth. The composition of topsoil shall include a well balanced medium consistent with MnDOT specification 3877.2C (premium topsoil borrow), modified to include no more than thirty -five percent (35 %) sand and silt content, respectively." The mass grading operations of the overall site could be accommodated by re- spreading four (4) inches of on -site topsoil and site stabilization. Areas reserved as open space would be required —279—