Iowa DNR

Water Quality Assessments

Impaired Waters List

Ioway Creek IA 03-SSK-6459

from unnamed tributary (T85N R25W Sec9 NW Boone Co.) to headwaters (T87N R26W Sec34 Hamilton Co.)

Assessment Cycle
Result Period
2010 - 2012
Class A1 Class B(WW-1)
Assessment Methodology
Assessment Type
Integrated Report
Category 4d
Legacy ADBCode
IA 03-SSK-0061_0
Overall Use Support
Aquatic Life Use Support
Primary Contact Recreation
Not assessed
Assessment Comments

Assessment is based on results of a fish kill investigation in August 2011.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008 (see, this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses.   According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters.   Thus, for the current assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]

SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain "not assessed" (IR 3a) due to lack of information upon which to base an assessment.   The presumptive Class B(WW-1) (aquatic life) uses are assessed (monitored) as "partially supported" (IR 4d) due to the occurrence of a fish kill in August 2011.  

EXPLANATION:  The presumptive Class B(WW-1) (aquatic life) uses are assessed (monitored) as "partially supported" due to the occurrence of a fish kill in August 2011.   The kill occurred on or before August 20, 2011.   Approximately 30,300 fish were killed over 2.75 miles of stream.  The value of the fish was reported as $13,750.22; the cost of the IDNR investigation was $641.56.   The cause of the kill was identified as land-applied animal (swine) manure.  

According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing.  Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b.  The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources.  If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody will be placed in IR Category 4d (impaired but TMDL not required).   IDNR records show that the party responsible for the kill was identified, and IDNR sought and received restitution for the value of the fish killed and the costs incurred by IDNR during investigation of the kill.   Thus, this assessment segment was placed in Category 4d of Iowa’s 2014 Integrated Report.

Monitoring and Methods
Assessment Key Dates
8/20/2011 Fishkill
140 Incidence of spills and/or fish kills
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
Organic enrichment/Low DO Aquatic Life Support High
  • Confined Animal Feeding Operations (NPS)
  • High
Unionized Ammonia Aquatic Life Support High
  • Confined Animal Feeding Operations (NPS)
  • High