South Fork Iowa River IA 02-IOW-750

The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). The following table summarized recreation season geometric means of E. coli at station SF400 over the 2010-2012 period:

Geometric means for recreation season of 2010 through 2012 exceeded the Class A1 criterion of 126 orgs/100 ml. Fifteen of the 23 samples (65.2%) collected over the 2010-2012 period exceeded the single-sample maximum criterion of 235 E. coli organisms/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to DNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).

A fish kill occurred in this stream segment west of Alden, IA, sometime before September 29, 2011. As a result of an DNR investigation, the suspected cause of the kill was identified as a spill or runoff of organic waste from a silage pile near 140th Avenue west of Alden. The kill was approximately one week old when discovered. The kill affected approximately 5 miles of stream and killed an undetermined number of fish. As of March 2016, there are no records of DNR seeking restitution for the value of the fish killed and cost of investigating the kill. 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. Thus, due to this pollutant-caused kill, this assessment segment was placed in Category 5b of Iowa’s 2014 Integrated Report (=303(d) list) and remains in IR Category 5b.

Monitoring by the NLAE approximately 2 miles NNE of Buckeye (station SF400) from 2010-2012 included continuous monitoring for dissolved oxygen, pH, and water temperature. Data for daily maximum, mean, and minimum values were provided to Iowa DNR. None of the 530 daily maximum and minimum values for pH exceeded the respective Class B(WW2) pH criteria of 9.0 and 6.5 pH units. The respective maximum and minimum pH values reported for this period were 9.0 and 7 pH units. Eight of the 529 daily maximum values for water temperature (1.5%) exceeded Iowa’s added heat criterion of 32C (maximum value = 33.8 C). Of the 468 daily minimum values for dissolved oxygen generated at monitoring site SF400 over the 2010-2012 monitoring period, only 1 value (0.2%) was below the 5.0 mg/l Class B(WW2) criterion (not < 5.0 mg/l during 16 hours of a 24-hour period), and no values were below Iowa’s Class B(WW2) criterion for a minimum dissolved oxygen of 4.0 mg/l at any time during a 24-hour period (minimum value = 4.95 mg/l). According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if more than 10% of the samples for conventional parameters such as temperature exceed their respective Class B(WW2) criteria, the aquatic life uses should be assessed as “impaired”. According to Iowa’s assessment/listing methodology, however, the percentage of samples exceeding the respective Class B(WW2) criteria for water temperature is not significantly greater than 10%. Thus, the monitoring results for water temperature at station SF400 do not suggest impairment of the Class B(WW2) aquatic life uses. [Note: monitoring for dissolved oxygen and other parameters at NLAE station SF400 ended in early July 2012. July, August, and September of 2012 were very warm dry months in the South Fork Iowa River watershed and in other Iowa watersheds as well, and low levels of dissolved oxygen in summer 2012 resulted in identifications of dissolved oxygen-related impairmentsin inother stream segments in the South Fork Iowa River watershed.]