Iowa DNR

Water Quality Assessments

Impaired Waters List

Rock River IA 06-BSR-1534

mouth (S1, T95N, R48W, Sioux Co.) to confluence with Little Rock R. in S35, T98N, R46W, Lyon Co.

Assessment Cycle
Release Status
Result Period
1994 - 1996
Assessment Type
Integrated Report
Category 0
Legacy ADBCode
IA 06-BSR-0030_0
Overall Use Support
Aquatic Life Use Support
Fish Consumption
Not assessed
Assessment Comments

Assessment is based on results of IDNR quarterly ambient water quality monitoring near the mouth of the Rock River from 1995-1997 and on DNR stream use assessments conducted in Sioux county.

Basis for Assessment

Used assessment of support of the Class B(WW) aquatic life uses developed for the 1994 report, in combination with results of DNR quarterly WQ monitoring from Oct 95 to Jul 97 near the mouth of the Rock River, to assess support of the Class B(WW) uses as FST.   Results from the DNR WQ monitoring station show no violations of Class B(WW) WQ criteria for either toxic or conventional contaminants in the 8 samples collected over the Oct 95 to Jul 97 period.   In addition, this station was monitored for common agricultural pesticides.   Levels of pesticides were relatively low, and none of the samples contained levels of pesticides that exceeded respective MCLs.   The following are ranges of pesticide levels in the eight samples collected:  atrazine (MCL=3.0 ug/l):  0.10- 0.33 ug/l; alachlor (MCL=2.0 ug/l): all samples < 0.1 ug/l; cyanzine (MCLG=1.0 ug/l):  0.1-0.11 ug/l.   The atrazine metabolites deethylatrazine and deisopropylatrazine were analyzed for but were not detected (detection level=0.1 ug/l).  This river reach is not designated for Class C drinking water uses.

Monitoring and Methods
Assessment Key Dates
330 Fish surveys
375 Visual observation-- may not quantify some parameters-- single season-- by prof.
150 Monitoring data more than 5 years old
230 Fixed station physical/chemical (conventional plus toxic pollutants)
Monitoring Levels
Biological 0
Habitat 0
Physical Chemistry 0
Toxic 0
Pathogen Indicators 0
Other Health Indicators 0
Other Aquatic Life Indicators 0
# of Bio Sites 0
BioIntegrity N/A
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude