E. coli data from Four MIle Run including Lower Long Branch at Troy park

These graphs contain volunteer-collected E.coli data from January 2010 until April 2012 in several  tributaries of Four Mile Run in Arlington, VA.
The blue line indicates bacteria levels; the red line represents the primary contact recreation water quality standard, and the green line represents the secondary contact recreation water quality standard.

The state of Virginia has set a numeric water quality standard of 235 E. coli CFU.100 ml to safely do swimming, canoeing, and kayaking.  The state has set a numeric water quality standard of 1173 E. coli CFU/100 ml to safely do wading, boating, and fishing.

Here is the link to the graphs, which are not considered laboratory-quality but are useful in identifying potential areas of concern and of further research.

http://www.arlingtonva.us/departments/EnvironmentalServices/sustainability/page83733.aspx

Noticeable are the very high level of bacteria in February of 2012 and then the very low level of bacteria of lower Long Branch on 4/1/12.  It makes me wonder what happened to cause that sudden spike in bacteria level?