One of the water quality goals for this subwatershed is the achievement of in-lake phosphorus concentration goals.  Reduction of phosphorus loads from the subwatershed to achieve that goal will require the combined efforts of the regulatory program, operational programs, and capital projects.  Tables 15 and 16 below set forth a summary plan for how this could be accomplished.

The tables break down modeled phosphorus loading in the subwatershed by source: atmospheric deposition, external sources, and internal sources.  Atmospheric deposition is a regional issue and is not dealt with here.  The primary means of addressing external loading are through the regulation of new loads generated by development and the reduction of existing loads.  The HHPLS identified upstream load reductions that could be achieved through the general application of BMPs to residential and agricultural land, such as phosphorus-free fertilizer, rain gardens, infiltration basins, agricultural BMPs, shoreline restorations, and retrofit projects.

Application of the current regulatory program to new development would also reduce the expected load from ultimate development conditions.  As Table 10 in Section 3.6 above indicates, more stringent regulation of new development could assist in maintaining good water quality in Lake Minnewashta and in meeting Lake Virginia water quality goals as limited opportunities are available for larger capital projects.

Table 15.  Phosphorus load reduction plan for Lake Minnewashta.

Lake Virginia

A TMDL study including a phosphorus reduction plan is currently being developed for Lake Virginia.  Proposed reductions from the TMDL include: reductions due to the new prohibition on the use of fertilizer with phosphorus; achievement of upstream water quality goals; shoreline restoration; treatment of runoff from Highway 7 and from Smithtown Road; application of more stringent regulations prohibiting new net phosphorus loading from development; and reduction of internal loading through internal load management such as biomanipulation or vegetation management.   Table 16 below sets forth a summary plan for how this could be accomplished in accordance with the TMDL.  The TMDL calculates reductions from the current conditions rather than future conditions.

Table 16.  Phosphorus load reduction plan for Lake Virginia.