3.0  Chestnut Park Water Quality Improvement Study 

Goals addressed: "The lake and watershed should be managed to restore and enhance habitat abundance and diversity." "Construct and maintain enhanced stormwater treatment facilities in the priority MHUs and individual sub-basins" (PBS&J, 1998). 

Discussion:  In 2001, PBS&J  presented a conceptual design report on the feasibility of treating stormwater run-off from the Group-C sub-basins and improving the ecological functions and overall water quality  of the Chestnut Park recreational pond system.  The recreational pond is located in John Chestnut Sr. Park, a County-owned facility located on the southeastern shore of Lake Tarpon.  The Group-C sub-basins ( sub-basins 45, 46, 47, and 48) are located just north of the park and encompass 337.2 acres (Appendix A).   The report listed three objectives:  provide water quality treatment for non-point source discharges from the Group-C sub-basins; improve water quality conditions in the Chestnut Park recreational pond system; and enhance the diversity and coverage of the native aquatic vegetation, and fish and wildlife habitat, in the Chestnut Park recreational pond (PBS&J, 2001). 

To limit nutrient loading from the Group-C sub-basins, the report recommended the  installation of an alum (aluminum sulfate) system to reduce levels of phosphorus, nitrogen, and bacteria from the run-off entering the pond.  Due to lack of available land, wet detention systems were not considered a viable option.  The proposed system would be installed at a box culvert along the Channel-U ditch system.  Flocculent material, resulting from the injection of alum into the discharge, would settle into the 1500-foot long ditch.  A diversion structure would also be constructed to divert large flow events over an existing wetland, minimizing flow into the alum system. 

Conclusion:  The results of the study indicate the main contributor to poor water quality in the Chestnut Park recreation pond was runoff from the Anchorage subdivision.  The Chestnut Park recreational pond has been degraded by poor water quality, excessively shallow depths, and lack of native vegetation. The report recommended a series of steps to include: 

    ·  Severing the hydrologic connection between two small feeder ponds entering             Chestnut pond 

    ·  Excavating the small ponds to form one large pond to treat runoff from the Anchorage        subdivision 

    ·  Constructing an outfall system to divert flow from the treatment pond across             an existing forested wetland to provide additional retention and attenuation for water         quality treatment 

Three recommendations were made to improve the vegetation and wildlife habitat in the pond.  The report suggested dewatering the pond and removing accumulated  sediment to deepen the ponds.  While the pond was dewatered, grass carp would be netted or electro-fished and removed.  When the pond was refilled, native plants would be placed along the shoreline based on both a forested and herbaceous zone scheme.  Planting options were outlined in the report. 

The Parks Department may pursue the Chestnut Pond project, but it is not yet on the Capital Improvement Project list through 2010.