Assessment Comments

: Assessment is based on: (1) the results of U.S. Geological Survey ambient chemical/physical water quality monitoring at Keosauqua from January 2010 through December 2012, (2) results of IDNR ambient chemical/physical water quality monitoring at Keosauqua from October 2010 to June 2012, (3) results of U.S. EPA/IDNR fish contaminant monitoring in 2006, 2008, and 2012 at Keosauqua, and (4) results of a fish kill investigations in July 2006 and July 2012.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” (IR 5a) due to levels of indicator bacteria (E.  coli) that very slightly exceed state criteria.   The Class B(WW1) aquatic life uses remain assessed (monitored) as “partially supporting” (IR 5b) based on results of fish kill investigations in July 2006 and July 2012 and a history of fish kills in, and upstream from, this assessment segment.   Results of USGS and IDNR chemical/physical monitoring from 2010-2012, however, suggest "full support" of the Class B(WW1) uses.   Fish consumption/human-health uses remain assessed (monitored) as "fully supported" (IR 2a) based on fish contaminant monitoring in 2006 and 2008.   The sources of data for this assessment are (1) the results of U.S.  Geological Survey chemical/physical water quality monitoring from station 05490500 at Keosauqua from January 2010 through December 2012, (2) results of IDNR ambient chemical/physical water quality monitoring at Keosauqua from October 2010 to June 2012, (3) results of U.S.  EPA/IDNR fish contaminant monitoring in 2006, 2008, and 2012 at Keosauqua, and (4) results of fish kill investigations in July 2002, July 2006, and July 2012.   This is the same assessment as that developed for the adjacent upriver segment of the Des Moines River (IA 04-LDM-0010_4).

EXPLANATION:  The Class A1 uses are assessed (monitored) as “not supported” due to violations of Iowa’s water quality criteria for indicator bacteria (E.  coli).   The geometric means of indicator bacteria (E.  coli) in the 29 samples collected during the recreational seasons of 2010 through 2012 at USGS station 05490500 at Keosauqua were as follows:  the 2010 geometric mean was 226 orgs/100 ml, the 2011 geometric mean was 19 orgs/100 ml and the 2012 geometric mean was 30 orgs/100 ml.   Only the 2008 geometric mean exceeded the Class A1 criterion of 126 orgs/100 ml; the 2011 and 2012 geometric means were far below the water quality criterion.   Five of the 29 samples (17%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.   The geometric means of indicator bacteria (E.  coli) in the 13 samples collected during the recreational seasons of 2010 through 2012 at IDNR station 10890001 at Keosauqua were as follows:  the 2010 geometric mean was 44 org/100 ml; the 2011 geometric mean was 27 orgs/100 ml, and the 2012 geometric mean was 91 orgs/100.   All three geometric means are well-below (meet) the Class A1 criterion of 126 orgs/100 ml although too few data points exist for the recreation seasons of 2010 (two samples) and 2012 (three samples) to calculate a meaningful geometric mean.   None of the 13 samples collected by IDNR (0%) exceeded the Class A1 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 a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).   Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”  Despite this impairment, levels of indicator bacteria in this segment of the Des Moines River are extremely low relative to other Iowa rivers.   The only cause of impairment for the current (2014) IR cycle is the 2010 geometric mean at USGS station 05490500 that slightly exceeded Iowa’s geometric mean criterion.  

The Class B(WW1) aquatic life uses remain assessed (monitored) as “partially supported” due to fish kills on July 31, 2002, July 10, 2006, and on July 7, 2012 on the reach of river between Eldon (Wapello Co.) and Douds (Van Buren Co.).   These kills are three in a series of kills that have occurred over the last 15 years or so that appear to involve primarily shovelnose sturgeon (Scaphirhynchus platorynchus).   Although the cause of the three recent kills and the previous kills remains unknown, the leading hypotheses are (1) that very high water temperatures, very low river flows, and elevated pH levels combine to make ambient levels of ammonia in the river toxic to the ammonia-intolerant shovelnose sturgeon and (2) that the kills are caused by a virus specific to shovelnose sturgeon.   The most recent kill in July 2012 was especially severe.   According to the local IDNR Fisheries biologist, the kill was reported on the lower Des Moines River on July 7, 2012, from approximately Eldon (downriver from Ottumwa) to Farmington in Van Buren County.   An estimated 57,000 fish were killed including at least 35,000 shovelnose sturgeon.   No specific cause of the kill was identified, but low flow conditions, flow alterations, and very high water temperatures (95+F) are believed to have contributed to the kill.  

According to IDNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period indicates that the aquatic life uses of a waterbody are only "partially supported.”  Thus, the Class B(WW1) aquatic life uses of this river reach were assessed as "partially supported” (303(d) impaired).   Also, according to IDNR’s assessment methodology, if a cause of a fishkill was not identified during the IDNR investigation (cause = "unknown"), 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, typically lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (Category 5 of the Integrated Report).   Waterbodies affected by such fish kills at usually placed in IR subcategories 2b or 3b and are added to the state’s list of “waters in need of further investigation”.   Due however to (1) the repeated occurrence of these kills over the last 15 years in Wapello and Van Buren counties, (2) the often large numbers of sturgeon killed (thousands), (3) the likelihood that these kills are caused by a pollutant and (4) the possibility that the kills have extended further downstream (possibly to Bonaparte), this impairment was added to Iowa’s Section 303(d) list (Category 5 of the Integrated Report).   This assessment is also applied to upriver segments (e.g., IA 04-LDM-0010_4).    

Despite the repeated occurrence of sometimes severe fish kills, results of water quality monitoring by the U.S.  Geological Survey and Iowa DNR near Keosauqua from 2010 through 2012 suggest "full support" of the Class B(WW1) uses.   No violations of Class B(WW1) water quality criteria for dissolved oxygen, ammonia, temperature, chloride, or sulfate occurred in the approximately 70 samples analyzed by these two agencies during the 2010-12 period.   Three of the 53 samples collected by USGS (6%), and two of the 21 samples collected by IDNR (10%) exceeded the Class A, B(WW1) criterion for pH.   According to U.S.  EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed state criteria for conventional parameters such as pH, the aquatic life uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).   According to IDNR’s assessment/listing methodology, however, the results from USGS station 05490500 and IDNR station 10890001 do not indicate that significantly greater than 10% of the samples exceed either the Class B(WW1) criteria for pH.   Thus, these results do not suggest impairment of the Class B(WW1) aquatic life uses.   In addition, none of the 51 samples analyzed by USGS for arsenic, chlorpyrifos, or dieldrin exceeded their respective Class B(WW1) aquatic life criteria, and none of the 33 samples analyzed for selenium exceeded its Class B(WW1) criteria.   Taken together, these results suggest “full support” of the Class B(WW1) aquatic life uses.   Due, however, to the repeated occurrence of fish kills in this river segment, the Class B(WW1) aquatic life uses are assessed as “not supporting.”  

Fish consumption/human-health uses are assessed (monitored) as "fully supported" based on the (1) 2006, 2008, and 2012 EPA/IDNR fish tissue (RAFT) sampling on the Des Moines River NNW of Keosauqua and (2) results of analysis for pesticides and metals in water.   This site has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of RAFT trend monitoring.   The 2006, 2008, and 2012 whole-fish samples of common carp had generally low levels of the primary contaminants.   The 2006 sample contained the following: mercury: 0.133 ppm; total PCBs: 0.164 ppm; and technical chlordane: 0.058 ppm.   The 2008 sample contained the following: mercury: 0.102 ppm; total PCBs: 0.187 ppm; and technical chlordane: 0.0833 ppm.   And the 2012 sample contained the following:  mercury: 0.111 ppm; total PCBs: 0.24 ppm; and technical chlordane: 0.11 ppm.   With the exception of the level of PCBs in the 2012 sample of whole-fish common carp, all levels of these contaminants are below Iowa’s consumption advisory thresholds.   The level of total PCBs in the 2012 sample of whole-fish common carp (0.24 ppm), however, exceeded the 1 meal/week consumption advisory trigger level (0.2 ppm) as defined in Iowa’s fish consumption advisory protocol.   According to the IDNR/IDPH advisory protocol, two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.   Also, according to the IDNR/IDPH advisory protocol, the previous results for levels of PCBs in whole-fish samples from the Des Moines River do not warrant issuance of an advisory but do indicate the need to conduct additional monitoring to better define contaminant levels in fillet samples from this river segment.   Thus, follow-up (fillet) monitoring will be conducted in 2014 to better determine (1) levels of PCBs in the edible portions (fillets) of fish in this river segment and (2) whether a consumption advisory for PCBs needs to be issued.   None of the 51 samples analyzed from 2010 to 2012 by USGS for arsenic and dieldrin, and none of the 33 samples analyzed for selenium, exceeded their respective HH (human health) criteria.