Screening Level Causal Analysis and Assessment of an Impaired Reach of the Groundhouse River, Minnesota

Three fish sampling sites on the Groundhouse River, in the St. Croix River basin in central Minnesota did not meet Minnesota's minimum criteria for aquatic life and beneficial uses under Clean Water Act (CWA) Section 303(d), and were listed as impaired under CWA 305(b). A screening-level causal assessment was completed in lieu of a complete assessment as fish and parameter data were collected synoptically over a seven year interval, thus the data were temporally compromised. The main goals of the screening level assessment were (1) to organize and assess the available data to eliminate possible causes and to identify gaps in the data to be filled by additional sampling, (2) to provide an example of a causal analysis that Minnesota could build on for additional impaired waterbodies, and (3) to examine and explore additional methodologies for associating measured biotic response to quantified environmental variables.