Agenda - Environmental Policy Board - 10/05/2009

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CASE # 2 Topsoil Ordinance Amendment(s) By: Chris Anderson, Environmental Coordinator Background: As the Board knows, the City recently implemented a new topsoil requirement applicable any time that a new principal building is constructed. The definition of topsoil that City Council ultimately adopted was: Black dirt composed of unconsolidated material, largely undecomposed organic matter this is a suitable foundation for vegetative growth. The composition of the topsoil shall include a well balanced medium consisting of the following: . A maximum sand/silt content of 20% . A minimum organic content of35% . A pH between 6 & 7 . Removal of all rocks in excess 00/4" The ordinance was developed on a volume basis. However, this has created some confusion and difficulty in administering the ordinance because all soil testing is based on weight. Thus, all of the soil samples submitted to date (for the purposes of pre-certifying soil suppliers), excluding one that was received last year and is no longer available, do not meet the specification currently in City Code based on current testing practices. Staff has revisited this topic with City Council and, based on their direction, brought forth a proposed amendment that would lessen the minimum organic content to 25% and the increase the maximum allowable sand content to 30%. City Council did introduce that ordinance amendment at their last meeting, but, after additional discussion, directed Staff to continue gathering info and research options with various entities. Due to the complexities of soil and the fact that many different soil compositions can be used to conserve water, Staff is leaning toward proposing to revise the topsoil specification similar to the EPB's recommendation last year. In October of2008, the EPB recommended requiring four (4) inches of topsoil meeting MN DOT Specification 3877C (premium topsoil borrow) but with a maximum sand content of 35%. Utilizing a this specification rather than identifying specific maximum allowable quantities provides more flexibility while not losing focus on the intent, which is to reduce the demand on the water supply. When reviewing all of the soil samples that various suppliers submitted, almost all of them met the MN DOT 3877C specification, without the need for any blending or additives. Moreover, all of the samples that did meet that spec would accomplish the intent of the ordinance, water conservation, while also providing a very suitable foundation for vegetative growth. Therefore, Staff likely will recommend that the definition of topsoil be revised to reflect the MN DOT premium topsoil borrow specification with the exception of organic matter. Staff believes that there is no benefit to limiting the organic matter content with a range and should just reflect the minimum required organic matter content.