Goose Creek IA 01-NEM-6371

[Note: A TMDL for the bacterial impairment for streams in the Duck Creek basin, including Goose Creek, was prepared by Iowa DNR in March 2010. This TMDL was approved by U.S. EPA in 2011. Due to completion of the TMDL, the Integrated Report category for the Class A1 recreational uses is changed from 5a (impaired; TMDL needed) to 4a (impaired; TMDL approved).]

Results of monitoring for indicator bacteria conducted weekly from April through October 2008 at Station GC4 suggest that the presumptive Class A1 uses of this segment of Stafford Creek should be assessed as "not supported." A total of 29 samples were collected at station GC4 during this period; these data allowed calculation of twenty-five, 30-day/five-sample geometric means. All of the 30-day geometric means exceeded Iowa’s Class A1 criterion of 126 organisms / 100 ml. The minimum and maximum geometric means were 765 and 5,944 orgs/100 ml, with 28 of 29 samples (97%) exceeding Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines and DNR’s assessment/listing methodology, these results suggest non-support of the presumptive Class A1 (primary contact recreation) uses due to geometric means of E. coli that exceed Iowa’s water quality criterion of 126 E. coli organisms/100.

The presumptive Class B(WW1) aquatic life uses are assessed as "partially supporting" based on a fish kill in August 2011. A fish kill occurred on Goose Creek on August 29, 2011. The kill occurred inside the Davenport city limits near the intersection of Hwy 6 and Eastern Avenue (911 address 3060 Eastern Avenue). Approximately 200 fish were killed over 0.65 miles of stream. The value of the fish was reported as $353.66; the cost of the DNR investigation was $269.84. The cause of the kill was reported as "unknown" with a human source suspected. This suspicion was based, in part, on water quality sampling that showed extremes in pH of approximately 5 pH units during the kill and a pH of 9 units following the kill. No other evidence of a human source of the kill was provided in the report. A review of flow data from the USGS gaging station on Duck Creek at Davenport shows that flows in the Duck Creek watershed were low during late August 2011 with flows in Duck Creek at USGS gaging station 05422600 at Duck Creek Golf Course between 3 and 4 cfs which was well-below the long-term median flows of from 7 to 10 cfs for this time period. The USGS data show an increase in flow on or about August 29th from about 3 cfs to about 6 cfs. Based on the low flow in the Duck Creek watershed prior to the kill, the rainfall event on or about August 29th, and the predominantly urban watershed of Goose Creek, is likely the explanation for the fish kill. Such kills are likely related to natural (weather-related) causes and the harsh environment of streams with urban watersheds. Thus, this stream kill is considered (with reservations) as a "natural kill" and thus will be considered a potential impairment that is appropriate for Iowa's list of waters in need of further investigation.

As part of TMDL monitoring, levels of dissolved oxygen were measured during sampling in 2008 at station GC4. None of the 29 samples violated the Class B(WW1) criterion of 5 mg/l. The minimum level of dissolved oxygen was 5.8 mg/l. Although these results suggest “full support” of the presumptive aquatic life uses, the lack of additional data for ammonia, toxic metals, and/or pesticides prevents development of a more complete assessment of the aquatic life uses.