5.6.1 Local Government Unit Subwatershed Phosphorus Load Reductions

The HHPLS and the Lake Hiawatha TMDL have identified a need to reduce phosphorus loading to Minnehaha Creek to achieve a goal of an in-creek total phosphorus concentration of 80 ug/L.  An approximate 8 percent load reduction was identified to be achieved through small-scale infiltration BMPs.   The distribution of that load reduction is shown in Table 18 below.  An additional 8 percent load reduction is identified to be achieved through near- and in-creek improvements.   At this time, insufficient information is available regarding in-stream processes that might also be contributing to phosphorus concentrations, including streambank erosion, internal loading in the impoundment areas, and contributions from riparian wetlands.  This plan recommends completion of a Minnehaha Creek Diagnostic Study to identify those internal sources and potential reductions from internal and streambank improvements prior to allocating that additional 8 percent load reduction to potentially collaborative construction projects as well as an additional allocation of phosphorus load reduction to upstream cities.

This plan promotes the general application of BMPs such as increased street sweeping, local water quality ponds, rain gardens and infiltration swales.  The LGUs must annually report to the District their progress toward accomplishing this requirement.

Table 18.  Allocation of Minnehaha Creek subwatershed general small-scale infiltration practices load from lakes TMDL as LGU Phosphorus Load Reductions (lbs/yr).

LGU

Lake Hiawatha 

Lake Nokomis 

Diamond Lake 

Wayzata

3

 

 

Minnetonka

121

 

 

Plymouth

10

 

 

Hopkins

34

 

 

St. Louis Park

172

 

 

Edina

67

 

 

Golden Valley

2

 

 

Minneapolis

217*

24

62

Richfield

0

36

 

Ft. Snelling

0

6

 

TOTAL

626

66

62

*Includes 28 pound reduction in Lake Harriet lakeshed (see Table 19) and 22 pound reduction in Diamond  Lake lakeshed, see Table 22.