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Lake McCarrons Subwatershed Analysis Report 2013

Mar 29, 2016

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  • Capitol Region Watershed District

    Lake McCarrons Subwatershed BMP CWP Project

    Subwatershed Analysis Report

    Prepared by

    January 9, 2013

  • i

    TABLE OF CONTENTS A. Introduction ......................................................................................................................................... 1

    B. Project Objective and Overview ...................................................................................................... 1

    C. Previous Work .................................................................................................................................... 2

    D. Investigations ...................................................................................................................................... 2

    E. Field Walk and Further Investigation Recommendations ............................................................ 5

    F. P8 Water Quality Modeling .............................................................................................................. 8

    G. Estimate of Probable Construction Costs ...................................................................................... 10

    H. Recommendations ............................................................................................................................ 11

    I. Next Steps ......................................................................................................................................... 11

  • Lake McCarrons Villa Park Subwatershed BMP CWP Project Page 1 Subwatershed Analysis Report

    A. INTRODUCTION Lake McCarrons is an 81-acre lake that is located in the southeastern corner of the City of Roseville within the Capitol Region Watershed District (CRWD) (see Figure 1 for location). A series of wetlands and open waters known as the Villa Park Wetland System (VPWS) is located to the northwest of the Lake and accounts for up to 72 percent of the total 1044-acre Lake McCarrons watershed. A popular 15-acre county park is situated along the eastern side of the lake. Lake McCarrons is a high quality recreational water body, and CRWD is committed to maintaining its integrity by managing pollutant loading from its subwatersheds, including the VPWS. Extensive monitoring and modeling has led the CRWD to develop a summer average TP concentration goal in Lake McCarrons of 33 parts per billion (ppb) or less. Recent water quality studies have noted that despite previous phosphorus reduction efforts, the VPWS continues to be a major source of nutrients to Lake McCarrons. In order to meet the in-lake goal of 33 ppb, a significant reduction in phosphorus loading to the Villa Park wetland complex is necessary. In 2010, the Villa Park Wetland Management Plan (VPWMP) was published. This plan included a goal to reduce Total Phosphorus (TP) loading from the contributing watersheds to the VPWS by 45 lbs per year on an average annual basis a 28 percent reduction from current loading. A number of specific recommendations to reduce runoff volume and pollutant loading to the wetland system from its watershed were included in the plan. In order to reduce TP loading, it is anticipated that volume control will also be required. The VPWS watershed is the subject of this analysis and report. The land use within the watershed is primarily residential, with commercial, industrial, and park areas mixed in throughout. There are also a number of wetlands and several constructed water quality ponds located within the watershed. A portion of the Trunk Highway (T.H.) 36 and Dale Street interchange is also located within the watershed. B. PROJECT OBJECTIVE AND OVERVIEW The objective of this project is to reduce the TP load to Lake McCarrons by 45 pounds per year through the implementation of volume reduction Best Management Practices (BMPs) upstream of Villa Park. This project is funded through a matching grant from the MN Clean Water Partnership (CWP) by the MN Pollution Control Agency. CRWD retained SRF Consulting Group, Inc. to review previous subwatershed analyses, plans, and monitoring reports, and to conduct additional analysis in order to identify locations for BMPs that can provide the desired reduction of total phosphorus loading. Existing utility information, contours, land use, soils data and as-built plans were compiled through a detailed information collection effort. Types of data and their sources included the following:

    CRWD drainage boundaries, various reports and monitoring information, wetland delineation;

    City of Roseville as-built plans, land use, utilities, contour, and other GIS data;

  • Lake McCarrons Villa Park Subwatershed BMP CWP Project Page 2 Subwatershed Analysis Report

    Ramsey County land use; Minnesota Department of Transportation T.H. 36 and Dale Street interchange construction

    plans; and

    Online tools such as the NRCS Web Soil Survey and the Fish and Wildlife Service National Wetlands Inventory.

    Wetland boundaries were also field identified and surveyed, and field reconnaissance was completed. Based on this information, drainage areas were revised and phosphorus loading sources throughout the watershed were located. Finally, potential BMP locations and possible conveyance and routing issues were identified. Once the analysis was complete, recommendations for the most appropriate BMP locations were developed. This report provides a summary of this detailed subwatershed analysis and provides recommendations for specific BMP types and locations that will effectively reduce TP within the VPWS watershed. C. PREVIOUS WORK

    Several water quality studies have already been completed for the Lake McCarrons watershed. These are summarized in the VPWMP, which was completed by Wenck Associates, Inc. in 2009, and revised in 2010. Wenck also performed their own analysis of the watershed and evaluated numerous BMP options. The details of this analysis are located in the VPWMP. In addition to the VPWMP, two University of Minnesota senior engineering capstone projects were completed in 2010 and 2011. The capstone design projects identified a total of 11 different locations for BMPs, and eight of these were selected for detailed P8 modeling by the students. The results of this analysis were published in the 2010 and 2011 Water Quality Management in Lake McCarrons capstone design reports. All of these locations were considered for this subwatershed analysis. D. INVESTIGATIONS

    After a preliminary analysis of the project area, it was determined that in order to remove 45 lbs TP on an average annual basis, which is a relatively large amount, BMPs would need to be constructed in either multiple small drainage areas or one or two larger drainage areas. According to the Simple Method, which is a simplified TP loading and removal worksheet developed for the Minnesota Stormwater Manual, runoff from over 140 acres of drainage area would need to be treated assuming a 50 percent TP removal via a structural BMP. Most work to date has concentrated on smaller drainage areas (less than 100 acres) that provide small amounts of TP removal. For example, of the eight locations studied by the University of Minnesota capstone design students in 2011, only two larger areas of 331 acres and 134 acres provided potential for significant TP removal at 31.7 and 20.6 lbs using infiltration BMPs. Neither of these locations meet the goal of removing 45 lbs TP. The others were smaller areas that removed less than 4 lbs TP on an average annual basis. These are also relatively costly to develop on a per-lb removal basis.

  • Lake McCarrons Villa Park Subwatershed BMP CWP Project Page 3 Subwatershed Analysis Report

    Land use also plays an important role in determining which drainage areas have higher pollutant loads and where stormwater treatment BMPs might be placed. Higher loading rates will result in greater TP removal when passed through an appropriate treatment BMP. This, coupled with drainage area size, helps to define which drainage areas would be the best candidates for BMP consideration. Figure 2 illustrates the annual TP loading estimated by the Simple Method. Impervious areas produce greater runoff and thus greater TP loading. The drainage area to Site 1, for example, though smaller in area, produces a relatively high loading because of its higher impervious surface area ratio. Therefore, based on the current subwatershed analysis and work completed for the VPWMP, it appears that the most cost effective approach is to concentrate on one or two larger drainage areas, preferably with a high percentage of impervious land use. Besides drainage area and land use, we developed additional criteria for selecting potential BMP locations within the Villa Park watershed. These criteria are based on previous studies and on practical and regulatory considerations. A complete list of these criteria is as follows:

    Total drainage area that drains to each location, Land use and percent impervious, Topography, Publically owned land available for BMP construction, Potential wetland impacts, Constructability and extent to which utilities, particularly storm sewer, must be modified or

    relocated,

    Volume reduction potential (soils, proximity to groundwater), Ability to discharge the BMP to receiving storm sewer or other conveyance system.

    As mentioned previously, 11 different locations were analyzed as potential BMP locations in the 2010 and 2011 capstone design projects, and 8 of these were modeled in P8. After SRF completed an in-depth review of these locations, it was determined that the majority did not meet the above criteria. Contour data alone ruled out several potential BMP locations because of