Ralston Creek IA 02-IOW-1899

Assessment Comments

This assessment is based on (1) photo documentation from May 17, 2001, (2) a 1996 assessment report from CDM Federal, (3) a 1998 report from Ecology and Environment, and (4) site characterization report for the Iowa City, Iowa, former manufactured gas plant site prepared by MWH for MidAmerican Energy in November 2001 (revised February 2003).

Basis for Assessment

SUMMARY:  The general aquatic life uses are assessed (monitored) as “partially supported.”  The sources of data for this assessment include the following:  (1) photo documentation from a May 17, 2001 visit by Dr.  Allen W.  Hatheway, Ph.D, P.  Geol., P.E.  (retired professor of geological engineering); (2) a 1996 assessment report from CDM Federal that summarizes their August 1995 on-site investigations of Ralston Creek at the Iowa City former manufactured gas plant site, (3) a 1998 report from Ecology and Environment summarizing their on-site investigations of the Iowa City FMGP site, and (4) site characterization report for the Iowa City, Iowa, former manufactured gas plant site prepared by MWH for MidAmerican Energy in November 2001 (revised February 2003).

EXPLANATION:  Several lines of evidence suggest that aquatic life uses of this reach of Ralston Creek are impaired due to movement of coal tar-related compounds from the Iowa City former gas manufacturing plant (FMGP) site to Ralston Creek.   This site is located along Ralston Creek immediately downstream from Burlington Street in Iowa City.   Photo documentation from the May 17, 2001 visit by Dr.  Allen W.  Hatheway, Ph.D, P.  Geol., P.E.  (retired professor of geological engineering); show the following:  (1) a sheen on Ralston Creek along the west side of Van Buren Street (south of Burlington Street) and directly opposite the commercial University of Iowa student housing; (2) two dead fish along the stream bank at this location [one fish is a creek chub approximately 3 inches in length; the other fish is slightly smaller and also may be a creek chub]:  Dr.  Hatheway attributes the sheen on the surface of Ralston Creek to light oils from the FMGP site that are seeping into and floating on the surface of Ralston Creek.   He feels that the fish mortality resulted from the ingested effects of tar-residual-polluted subsurface waters breaking out at, and below the ground surface at the stream-water stage

CDM Federal Programs Corporation collected sediment samples on August 17, 1995 and included the findings of the sampling in the Final Screening Site Inspection Report for the Iowa City FMGP Site, dated July 30, 1996.   EPA reviewed and approved the report on August 7, 1996.  During sample collection a "sheen on water and sediment" was recorded on the sample collection forms by the sample collector.   Also, the Final Screening Site Inspection Report states that "there was an oily sheen on the water and sediment" and "there was also an odor of coal tar in the area where these samples were collected".   Table 2 in the SSI Report states that additional sediment samples were collected along Ralston Creek due to the "obvious coal tar contamination of stream sediment from the other two samples taken adjacent to the site south of the Burlington Street bridge and north of the access bridge".  

Ecology and Environment, serving as EPA’s contractor for the Ralston Creek site, submitted to EPA on May 27, 1998 a draft Expanded Site Inspection Report.   In this report, they state (page 3-2) that the decision to conduct additional sampling at this site “was made based on visual and olfactory observance of coal tar contamination of stream sediment from the other two samples taken adjacent to the site south of the Burlington Street bridge and north of the parking lot access road bridge."  The sampler noted the following on the sample field sheet for sediment sample #106:  "surface water sediment-grossly contaminated coal tar in sample".   Similarly, for the sediment sample #109 location, the sampler noted that "stream sediment contains coal tar waste."  

The site characterization report prepared by MWH for MidAmerican Energy in 2001 (and revised in 2003) involved analysis of sediment, water, and biota from sites upstream, adjacent to, and downstream from the Iowa City / Ralston Creek FMGP site.   A summary of the data generated from this study shows that the FMGP site is likely a source of the PAHs and other coal tar-related compounds seen in the sediments adjacent to, and downstream from, the site.   The results of analysis of water samples from Ralston Creek suggest that the lighter fraction BTEX compounds (benzene, toluene, ethylbenzene, and xylene) tend to occur adjacent to, and downstream from, the FMGP site.  

IDNR staff reviewed the results of biological monitoring conducted as part of this assessment and agreed that although the biological integrity of the aquatic communities of Ralston Creek is below expectations, the potential causes of the lowered biotic integrity likely include several factors in addition to presence of the toxics attributed to the FMGP site (e.g., lining of the stream channel with tiles, discharges of stormwater to the stream, and impacts of low-flow or no-flow episodes).

Based on a review of the above information, IDNR staff have concluded that the Iowa City FMGP is causing conditions in Ralston Creek that violate the following narrative criteria as defined in the Iowa Water Quality Standards (Chapter 567-61.3(1)455B)):

--Such waters shall be free from floating debris, oil, grease, scum and other floating materials attributable to wastewater discharges or agricultural practices in amounts sufficient to create a nuisance.   [The presence of the oil sheen on Ralston Creek adjacent to the Iowa City FMGP site, and documented in the May 2001 photographs from Dr.  Allen Hatheway and as documented in the CDM Federal Corporation report of 1996, violates this narrative criterion.]

--Such waters shall be free from substances attributable to wastewater discharges or agricultural practices producing objectionable color, odor, or other aesthetically objectionable conditions.   [The presence of coal tar odor at Ralston Creek adjacent to the Iowa City FMGP site, as documented in the CDM Federal report of July 1996, violates this criterion.]

--Such waters shall be free from substances attributable to wastewater discharges or agricultural practices in concentrations or combinations which are acutely toxic to human, animal, or plant life.   [The presence of relatively high levels of toxic coal tar-related substances in the water and sediments of Ralston Creek adjacent to, and downstream from, the Iowa City FMGP site, suggest a violation of this narrative criterion.   ]

Based on the documentation of coal tar-related oil sheens, odor, and the potential for acutely toxic conditions in Ralston Creek, the general aquatic life uses of this segment of Ralston Creek are assessed as impaired.   Thus, this waterbody will be added to Iowa’s 2004 list of impaired waters are required by Section 303(d) of the federal Clean Water Act.