Raccoon River IA 04-RAC-1117

from the Polk/Dallas county line to confluence of North Raccoon and South Raccoon rivers in Dallas Co.

This is a Legacy Assessment. Prior to 2004, assessments were developed under a methodology that pre-dated the Integrated Report guidelines.

Assessment Cycle

1996

Result Period

1992 - 1994

Designations

Assessment Type

Monitored

Integrated Report

Category 0

Legacy ADBCode

IA 04-RAC-0010_2

Overall Use Support

Not supporting

Aquatic Life Use Support

Threatened

Fish Consumption

Not assessed

Primary Contact Recreation

Not supporting

Drinking Water

Partial

Documentation

Assessment Comments

Assessment is based on ambient monitoring by Des Moines Water Works and IDNR city monitoring. Same comments as prepared for Raccoon River waterbody segment 04-RAC-0010-1 (mouth to Polk/Dallas county line).

Basis for Assessment

Had 14 of 18 non runoff-affected samples in violation of Class A WQ criterion (=78% viol =NS). Only violations of Class B WQ criteria was mercury: 6 of 9 samples collected over 3 years exceeded the Class B WQ criterion (= 67% viol). Due to problems with mercury analysis, and due to recommend in 305(b) guidelines (1996: 5-18) regarding reliability of toxics data < 1 ppb., these violations are not considered in the assessment. Thus, Class B uses assessed as FST due to presumed impacts from NPS. For Class C use, 14 of 68 samples had NO3 > 10 mg/l (= 20% viol). Although both mean (7.45 mg/l) and median (7.5 mg/l) levels of NO3 were < 10 mg/l, assess as PS due to installation of nitrate removal system by DM W.Works.