3.1 Water Quality

  1. The water quality in Langdon Lake since 1998 has consistently been scored in the D-F grade range on the District's annual lake report cards.  The mean summer 2004 total phosphorus concentration was 138 ?g/L, well in excess of the District's 55-70 ?g/L interim goal.  Based on this monitoring history, Langdon Lake's water quality is not supportive of swimming.
  2. During development of the HHPLS the subwatershed was under the review of two Regional Teams, which recommended different goals for the lake: 55 ?g/L and 70 ?g/L.  The state standard, and thus the long-term goal for Langdon Lake is 40 ?g/L.   Phosphorus loading reductions would be necessary to achieve any of these desired in-lake phosphorus concentrations.  The HHPLS and modeling performed for this plan also noted that internal loading and possibly phosphorus export from wetlands in the subwatershed were likely significant sources of excess phosphorus in the lake.
  3. Runoff from developed areas in the eastern subwatershed receives little if any treatment prior to discharge to receiving waters.
  4. No monitoring data are available for Saunders Lake or Black Lake. 
  5. Development, redevelopment, and reconstruction in the subwatershed are predicted to increase nutrient and TSS loads from the watershed as well as increasing the volume of stormwater runoff, potentially further degrading water quality in Langdon Lake and streams and wetlands in the subwatershed.