Biological and Water Quality Study of the Little Miami River and Tributaries 2012: Hamilton County, Ohio
The 2012 bioassessment of the Little Miami River and tributaries is the second of four years of sampling and analysis that is being conducted following the design of a comprehensive assessment of the Metropolitan Sewer District of Greater Cincinnati (MSDGC) service area. The principal objectives of the assessment are to verify existing aquatic life and recreational use designations, assign uses to unlisted streams and stream segments, make recommendations for any changes to existing use designations, report attainment status following the Ohio WQS and Ohio EPA practices, and determine associated causes and sources of impairment. The sampling and analysis is performed by Level 3 Qualified Data Collectors and under a biological Project Study Plan approved by Ohio EPA under the specifications of the Ohio Credible Data Law. The 2012 study area included the Little Miami River mainstem from U.S. Rt. 22 (RM 27.9) to downstream from Kellogg Ave. immediately upstream from the mouth of the Ohio River. The East Fork of the Little Miami River was included from immediately downstream from the Harsha Reservoir outlet (RM 19.5) to the confluence with the Little Miami River (RM 11.5). All service area tributaries and their watersheds were included in the 2012 survey with sampling sites located in the upper reaches at drainage areas of <1.0 mi2. All potential pollution sources were bracketed with sampling sites and also to reveal the extent and severity of impairments in proximity to individual and aggregated sources of impact on water quality, habitat, and biological condition. Of the 111 sites assessed in 2012, 93 were evaluated under the Warmwater suite of uses (2 additional sites were dry) and the remaining 16 under the Primary Headwater assessment methodology. In all, only 19 of 93 sites fully attained their applicable aquatic life use. A total of 43 sites were in partial attainment and 31 were in non-attainment. Of the 16 Primary Headwater sites, 7 were PHWH Class 2 and 9 were PHWH Class 3A. Eleven (11) different causal categories and 10 different source categories were identified for the 2012 study area (Table 2). Of these causes, flow alteration, chlorides, and organic enrichment were the most frequently listed with urban runoff the most frequently listed source. Classic pollutants such as ammonia, oxygen demanding substances, and toxic substances were listed only infrequently and then in localized reaches. Change in fish and macroinvertebrate indicators between the series of Ohio EPA surveys in 1983, 1993, 1998, and 2007 and the 2012 MSDGC survey indicates an overall decline in biological condition compared to 2007. The fish IBI in particular exhibited the most significant decline when compared to the 2007 values. As a result the aquatic life attainment status showed a marked decline in 2012 due primarily to IBI scores failing to meet the EWH biocriteria resulting in partial attainment for much of the mainstem in 2012. Impairment of recreation uses in the lower Little Miami River study area was not uncommon. The Primary Contact 30-day geometric mean criterion was exceeded at 38 of 92 sites sampled. High minimum E. coli values were highlighted as an indicator of chronic bacterial impairment and at some sites minimum values greater than the geometric mean PC criterion underscored the magnitude of these exceedances. Identifying the sources of fecal bacteria in urban areas can be a complex process, but in the lower Little Miami River it is likely related to combined sewer overflows (CSOs), sanitary sewer overflows (SSOs), urban runoff, and unsewered areas.