Agenda - Public Works Committee - 01/15/2008

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CASE # Jj CONSIDER ESTABLISHING TOPSOIL REQUIREMENTS IN NEW SUBDIVISIONS By: Steven Jankowski, City Engineer 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 is considering various conservation measures. Some, such as watering restrictions and requiring rain sensors on irrigation systems in multi-family and commercial developments, have been in place and utilized for several years now. However, more needs to be done to ensure adequate quantities ()f water are available now and in the future. Observations: The sandy soils found throughout the City do not have much capacity for retaining moisture. Thus, large quantities of water are used each year as irrigation, both for new and existing lawns. One way to increase soil moisture holding capacity (not to mention nutrient retention and reduced soil compaction) would be to require a quality topsoil over all landscaped areas in new developments. At a Public Works Committee meeting on January 17, 2006, this topic was discussed. It was the recommendation of the Public Works Committee, which was subsequently ratified by City Council, that Chapter 9 of City Code be amended to require six (6) inches of topsoil (topsoil would be defined as a sandy loam with at least forty percent [40%] organic matter) in all landscaped areas of new developments. The Council direction also specified that this proposed requirement be sent to the Environmental Policy Board (EPB) for review and comment. The EPB addressed this issue at their July 23, 2007 meeting and the minutes of that meetingrelatiIig to the discussion on this matter are attached to the case. One significant comment to come from the EPB was to question whether the requirement for 40% organic material in the specification for topsoil was reasonable. Subsequent . correspondence between staff and MN Pollution Control Agency suggest that 40% does appear to be quite high. The MnDot specification for topsoil lists an organic content range between 3% and 20%. One additional point made by the EPB was that compacted topsoil maybe less pervious than the native sand since organic particle are smaller and more easily compacted than sands. The EPB recommended that incorporation of organic matter into the soil should be further encouraged. Staffwill attempt to have soil samples having various organic contents available at the meeting for observation. Except for wetlands it is rare to find topsoil in Anoka County which has an organic content greater than 6%. If the City were to require that topsoil used in new subdivisions have an organic content somewhere in the middle of the MnDOT specification range, say 10%, it would likely require that a soil amendment be 17