Rock River near Iowa Border - Ammonia, Fecal Coliform & Turbidity: TMDL Project

The Rock River watershed is impaired for turbidity, ammonia nitrogen, fecal coliform, and mercury. In 2006, EPA contracted with Minnesota State University-Mankato Water Resources Center to develop a TMDL assessment for fecal coliform, turbidity, and ammonia nitrogen. Upon data review, the ammonia nitrogen impairment was delisted. In April 2008, a TMDL assessment addressing four impaired reaches (one bacteria reach, three turbidity reaches) was approved by EPA.

The Rock County Land Management Office worked with local stakeholders and technical entities to develop an implementation plan that addresses the fecal coliform bacteria and turbidity impairments. The implementation plan was approved on September 29, 2008.

The Rock County Land Management Office on behalf of the Rock River Watershed TMDL group has applied for funding to address the impairments in the watershed. Beginning in October 2009, an EPA Section 319 grant will be implemented where incentives for best management practices for manure management, education and monitoring will be conducted. A low interest loan program through MPCA’s Clean Water Partnership for replacing subsurface treatment septic systems will be available to homeowners in the Rock River watershed in early 2010.

Map and location

The Rock River is located in southwestern Minnesota, originating from the Buffalo Ridge. The river flows south into Iowa where it converges with the Big Sioux River. The Rock River watershed is located in parts of Pipestone, Rock, Murray, and Nobles counties. Rock River is in the Missouri and Des Moines River basins.


TMDL report and implementation plan

Other documents


Information contact

Mark T. Hanson, Project Manager
Minnesota Pollution Control Agency
504 Fairgrounds Rd. Suite 200
Marshall, MN 56258