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Final Report Introduction - Arden Hills Water Quality Task Force _ June 2000 'Construction projects and other runoff events in Roseville via Judicial Ditch # 4 have the potential to dramatically affect downstream water quality. Little Lake Johanna is suspected to be a phosphorus catch for a large area of Roseville, which drains through the lake and into Johanna. .AH has many pipes which outlet directly into waterbodies of all kinds with little or no pretreatment. There is little or no protection in several areas from potential spill hazards from freeways, state and county roads, which represent a significant drainage area in Arden Hills. The locations of some high impact areas are known generally but will require more study to determine specific locations and degree of impact. .The City of Arden Hills has a formal street sweeping policy and uses salt sparingly but does not train personnel in best management techniques for water quality. There are no ordinances that encourage water quality protection other than offered by Rice Creek Watershed Districts rules. Arden Hills as a fully developed city is not completely protected by RCWD rules structured to accommodate development in rural areas, 4 Lakes Water quality in Arden Hills is well understood by Rice Creek Watershed District (RCWD) and Ramsey County for the lakes Johanna and Josephine; however, there are several areas where the data set is incomplete or inconclusive. Baseline data for the smaller lakes, drainage's, and wetlands is not available. The lakes Johanna and Josephine have shown some improvement in water clarity over the last 20 years. (See Appendix - "Trophic States of RCWD lakes" and attached discussion) All lakes in the RCWD tend to have eutrophic! characteristics and as such are sensitive to water quality impacts. A full-scale appraisal of Lake Johanna by the RCWD is scheduled for Summer of 2000.' Weed growth cycles and exotic species have continued to draw the concerns of residents over water quality and need more study. 4 Volume control of stormwater is a new concept in RCWD rules. The established methods and standards have not developed to a sufficient extent to protect corrununities that already have a high level of impervious surfaces, " Stormwater management in the District has historically focused on controlling peak runoff rates and providing water quality treatment via NURP style ponds. The 1995 Volume Study (Montgomery Watson PEl demonstrated that the Districts current Rules and Regulations targeting peak runoff rates are not sufficient to maintain flood stages in several District lakes. Furthermore, without volwne control measures, as recorrunended in the Volume Study, high water draw down times are longer and available storage volumes are filled thus increasing the risk of flooding from the next rainfall." _ Memo to RCWD Board of Managers from Derek Knapp PE -Montgomery Wa!son _ 2/29/2000, 5 Eutrophic - A description for a body of water where the organic nutrients reduce the dissolved oxygen, producing a more favorable environment for plant than animal life, Other related states are Mesoeutrophic and Hypereutrophic, See Appendix Attachment D for relative comparisons ofIake status and discussion. 6 See Appendix - Exhibit (A) from Lake Assessment Program Cooperative Work Plan _ MPCA. 2 . .. .