Coralville Reservoir IA 02-IOW-630

Assessment Comments

Assessment is based on water quality monitoring.

Basis for Assessment

No viols of Class A or Class B(WW) WQ criteria in the 45 samples collected in 1994 and 1995 from the sample location at the Mahaffey Bridge.   Did, however, have report of violation of Class B(WW) WQC for DO on Feb 18, 1993 at reservoir surface (0.2 mg/l) see Johnson & McDonald 1994: 18) that occurred during heavy ice cover and coincided with a high BOD of 15 mg/l; high BOD values did not occur upriver from the reservoir at this time.   These conditions, coupled with falling pool level, likely led to an "extensive fish kill" at this time (see Johnson & McDonald 1994: 19).   Levels of fecal coliform bacteria generally exceeded the Class A WQC in 93 except at the West Overlook Beach, probably due to extremely high runoff; levels in 1994 were nearly all below the WQC (=FS).   Levels of all organochlorines and mercury in fish fillet well below FDA action levels (=FS).   No info for 1995 bacteria & fish contams.