ADBNet

The Class B(WW2) aquatic life uses are assessed as “partially supported” due to a fish kill in early November 2014. This fish kill occurred on or before November 3, 2014, near Big Hollow Lake approximately 5 miles SW of Mediapolis in Des Moines County. Investigators suspected a human-related cause of the kill. The following are notes from the fish kill investigation:

The DNR investigated white material in Flint Creek north of Burlington Tuesday [November 4th] through Thursday [November 6th] this week. A DNR investigator found a white material flowing from Big Hollow Creek into Flint Creek, and several locations with dead and dying fish, but was unable to find the source of the pollutant before nightfall Tuesday. Investigators returned Wednesday to trace the white material to a pool below the Des Moines County Conservation Board’s Big Hollow Lake. Field tests showed extremely low dissolved oxygen levels in the pool, along with dead fish. DNR determined a discharge from the lake caused the fish kill after a county conservation board employee opened an overflow gate on the lake about 3 p.m. Monday [November 3rd]. Lake water discharged for about 10.5 hours, lowering the 178-acre lake by approximately one foot and releasing low oxygen sediment into Big Hollow Creek. The white color is likely gypsum clay from the bottom sediments in Big Hollow Lake. White sediment traveled about 19 miles downstream, but the fish kill was limited to the first two miles in Big Hollow Creek directly below the lake. DNR fisheries staff counted 252 dead fish Thursday, mostly minnows and Johnny darters, followed by green sunfish and a few sport fish. The DNR will continue to monitor the situation and consider appropriate enforcement action, including fish restitution and investigation costs totaling $459.94.

An estimated 252 fish were killed. The kill affected approximately 2 miles of stream. The value of the fish killed was estimated at $459.94; no cost of the Iowa DNR investigation of the kill was provided.

According to DNR’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). As of August 2019, however, there is no evidence that Iowa DNR sought restitution for the value of the fish killed. Based on this information, the Class B(WW2) aquatic life uses are assessed as “partially supporting”, and this segment is placed on Iowa’s Section 303(d) list of impaired waters.