Assessment Comments
Assessment is based on (1) results of IDNR/UHL TMDL monitoring on the Maquoketa River at Manchester (upstream from dam; near Tirrill Park; STORET station 11280001) from April to September 2005, (2) results of monitoring in 2006 by the Lake Delhi Watershed Association on the Maquoketa River (STORET station 15280004), (3) IDNR/UHL biological (REMAP) monitoring in 2002, (4) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2002, (5) results of fish contaminant monitoring conducted as part of the IDNR/UHL REMAP biological monitoring project in 2006, (6) results of an IDNR investigation of a fish kill in Lake Delhi in August 2004 and (7) IDNR Fisheries bureau fish sampling in 2002, 2004, and 2006.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses remain assessed (monitored) as “not supported” due to levels of indicator bacteria that exceeds state water quality criteria. The Class B(WW1) are assessed (monitored) as “partially supported” based on results of DNR/UHL biological (REMAP) monitoring in 2002 and on results of IDNR Fisheries biological monitoring in 2002, 2004 and 2006. This assessment is independent of the assessment for Lake Delhi in which a fish kill occurred in August 2004. Fish consumption uses are assessed as “fully supported” based on results of fish contaminant monitoring in 2002 and 2006. Sources of data used for this assessment include (1) results of IDNR/UHL TMDL monitoring on the Maquoketa River at Manchester (upstream from dam; near Tirrill Park; STORET station 11280001) from April to September 2005, (2) IDNR/UHL biological (REMAP) monitoring in 2002, (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2002, (4) results of fish contaminant monitoring conducted as part of the IDNR/UHL REMAP biological monitoring project in 2006, (5) results of an IDNR investigation of a fish kill in Lake Delhi in August 2004, (6) IDNR Fisheries bureau fish sampling in 2002, 2004, and 2006, and (7) results of water quality monitoring in 2006 by the Lake Delhi Watershed Association on the Maquoketa River above Backbone Lake (STORET station 15280004).
EXPLANATION: The Class A1 (primary contact recreation) uses were assessed (monitored) as "not supported" due to violations of Iowa’s water quality criteria for indicator bacteria. The geometric mean of E. coli in the 12 samples collected in 2005 at the IDNR/UHL TMDL station at Manchester was 461 orgs/100 ml. Ten of the 12 samples (83%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Data generated as part of the Lake Delhi watershed assessment in 2006 also suggest impairment of the Class A1 uses. The geometric mean for E. coli in the seven samples collected in the Maquoketa River above Lake Delhi near Bailey’s Ford County Park (STORET station 15280004) from April to June, 2006 (1,146 orgs/100 ml) far exceeded the Iowa geometric mean criterion of 126 orgs/100 ml; levels of E. coli in five of the seven samples exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.
Despite the occurrence of a fish kill in Lake Delhi in August 2004, results of water quality monitoring in 2005 suggest that the Class B(WW1) aquatic life uses in the flowing portion of this assessment segment should be assessed (monitored) as "fully supported. Results of water quality monitoring by the IDNR/UHL at the TMDL station at Manchester from April through September 2005 show no violations of state Class B(WW1) water quality criteria in the 12 samples analyzed for dissolved oxygen and pH or in the 11 samples analyzed for ammonia.
The assessment of support of the Class B(WW1) uses, however, is primarily based on biological data collected in 2002 as part of the IDNR/UHL REMAP project and on biological data collected in 2002, 2004 and 2006 by the Manchester Fisheries sampling program. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 REMAP FIBI score was 59 (good) and the BMIBI score was 57 (good). The Fisheries average (n=7) FIBI score was 57 (good). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The non-riffle habitat FIBI BIC for this ecoregion is 44 and the natural substrate BMIBI BIC for this ecoregion is 70.
A fish kill occurred in Lake Delhi in August 2004. This kill occurred on or before August 9, 2004. The kill was reported to occur between Freddy’s Beach and the Lake Delhi Dam. Based on the investigation conducted by the IDNR Fisheries Bureau, the kill was attributed to natural causes. A malfunctioning aeration system may have played a role in the kill. An estimated 330 fish were killed; no estimate of the value of the fish killed was provided. According to the IDNR investigation, fish killed included bluegills and channel catfish. 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 (2002-2005) 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 was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.” Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5). Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.
Fish consumption uses remain assessed (monitored) as “fully supported” based on results of fish contaminant monitoring at (1) the U.S.EPA/IDNR fish contaminant (RAFT) monitoring site at Bailey’s Ford Access southeast of Manchester in Delaware County in 2002 and (2) REMAP site 28 in 2006. The composite samples of fillets from channel catfish and largemouth bass from the 2002 RAFT monitoring and the samples of common carp fillets from the 2006 REMAP monitoring all had low levels of contaminants. In the RAFT samples, levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.056 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.196 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. In the REMAP samples, levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.178 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of all contaminants are below fish consumption advisory trigger levels as specified in Iowa’s fish consumption advisory protocol (http://www.iowadnr.gov/fish/news/consump.html).
