Prepared by the Ohio Environmental Protection Agency

This preliminary summary of water quality in the Darby watershed, based on data collected during the 2001 Total Maximum Daily Load (TMDL) survey, portrays an aquatic system threatened by  urbanization, and excess nutrient load, bacterial contamination from diffuse sources such as failing on-lot waste treatment systems, discharges from waste water treatment facilities, agricultural runoff and chemical spills. This survey covered the main stem of Big Darby Creek and several of its key tributaries. For this summary, we will focus on Big Darby Creek, Little Darby Creek and Spring Fork. This summary is very general in scope, based on a cursory view of tables and figures, and should not be used as a mechanism to draw conclusions about specific causes and sources of pollution in the Darby Creek Basin.

Big Darby Creek

Big Darby Creek originates near the town of Middleburg in the Southeast Corner of Logan County and is heavily influenced by Flat Branch, Buck Run, Sugar Run, Robinson Run and Hellbranch Run from the easterly direction, and Spain Creek, Pleasant Run, Proctor Run, and Little Darby Creek from the West. The landscape of this Eastern Corn Belt Plains (ECBP) watershed is mostly characterized by lowland pastures and crop land with a few small cities and villages along its entirety including North Lewisburg, Milford Center, Unionville Center, Plain City, Darbydale, Harrisburg and Orient. The cities of Columbus and Hilliard influence a portion of Hellbranch Run, a major tributary entering from the east.

Water quality in the Big Darby Creek appears to be "fair" to "good". Chemical results from 5 sampling runs conducted during the summer of 2000 reveal gross contamination in the water column from point sources such as Honda and Plain City. Flat Branch has been seriously impacted by habitat and chemical issues originating near the headwaters on Honda's property. Honda has provided a corrected action plan to remedy the situation. Additionally many exceedences of the Ohio EPA bacterial criteria were found from the headwaters of Big Darby Creek to the mouth along with many nutrient values in excess of median [50th] as well as the 75th, 90th and even 95th percentile values when compared to background ECBP stream nutrient and demand data such as Total Suspended Solids [TSS]. These chemicals and bacteria are likely the combined result of point and non-point sources [NPS] of pollution entering Big Darby Creek and its tributaries. The loads appear to be exponentially higher during rain events. A more detailed breakdown of causes and sources will be discussed in the final TMDL report.

Habitat along most of Big Darby Creek has not changed significantly in the recent past except for disruptions caused by recent bridge work on U.S. Route 33 in Logan County along with residential development in the headwaters and middle section of Hellbranch Run. Historical drainage projects like petitioned ditch maintenance is very common. These activities have resulted in stream channelization, filling of wetlands, denuding of riparian vegetation, and a general trend of increased "hardening" of the watershed such as an increased number and width of roadways, more winter plowing, land and roof drainage. This hardening results in greater and more rapid run-off that leads to more torrential, "flashy" flow following significant rain events. Paradoxically, these same streams tend to lose water at a faster rate during periods of drought. This can affect the abundance and make-up of aquatic communities.

Biology

The biota in Big Darby Creek is in "fair" to "good " shape with "Full Attainment" of aquatic life used in 11 of the 17 sites sampled during the survey. Aquatic communities in the upper and middle sections of Big Darby Creek seem to be impacted the most. Partial or non-attainment persisted from the confluence of Flat Branch to SR 38. Likely causes of partial or non-attainment include agricultural run-off, poor riparian habitat, and disturbances near the headwaters of Flat Branch. Partial attainment was also found downstream of Plain City likely attributable to urban impacts, including the hardening aspect described above, increased nutrient load from the Plain City waste water treatment plant (WWTP) as well as from the unsewered community of Amity. Non-attainment near Milford Center may be due to a large fish kill that occurred during the summer of 2000 as a result of a chemical spill. This section of stream is still recovering from that spill event. Fish and invertebrate communities in the lower section of Big Darby Creek are in full attainment of exceptional warmwater habitat (EWH) aquatic life use. Although some of the tributaries exhibit partial or non-attainment of their assigned aquatic life uses, the lower section of Big Darby Creek appears to maintain good fish and invertebrate communities. Excellent habitat, good recharge of flow and increased stream size help to support such quality biota.

Little Darby and Spring Fork

Little Darby Creek originates in Champaign County northwest of the village of Mechanicsburg whereas the Spring Fork headwaters are south of Mechanicsburg. With the exception of Mechanicsburg and West Jefferson, Little Darby Creek and Spring Fork are largely influenced by agricultural land use. The Mechanicsburg WWTP has experienced numerous overflows and permit violations contributing solids, nutrients and bacteria to Little Darby Creek.  Unsewered homes discharging into the stream in urban and rural areas are also responsible for human induced nutrients and bacteria. Both Little Darby Creek and Spring Fork are impacted by field run-off as well as animal husbandry with unfenced cattle gaining access to the stream. Both streams exhibit inconsistent riparian habitat. For example, it is not uncommon to find excellent habitat on one side of a road, and poor habitat on the other side. Other major tributaries to Little Darby Creek include Lake Run, Treacle Creek and Barron Run; the latter two are heavily influenced by agriculture.

Comparisons of 50th, 75th, 90th and 95th percentile nutrient concentrations to background ECBP streams proved similar to Big Darby Creek with many ammonia and phosphorus values exceeding the 75th percentile values. Over 40 bacterial exceedences were recorded throughout the Little Darby watershed during the 2001 survey. It is difficult to differentiate between human and agricultural sources since fecal coliform and E. coli. are found in all mammals and fowl, but one can assume with a fair amount of certainty that the source of bacteria in the Little Darby Creek watershed is attributable to both.

Biology

Little Darby Creek was in full attainment of aquatic life use at 8 of 11 sampled during summer, 2001. Partial attainment occurs around Mechanicsburg and near Axe Handle Road. Causes include urban run-off, channelization and habitat limitations, and agricultural practices along Little Darby Creek and Treacle Creek. Full Attainment is achieved downstream of Axe Handle Road to the mouth, even though Little Darby Creek experiences nutrient load from Spring Fork and the West Jefferson WWTP as well as other urban impacts from the city of West Jefferson. Good groundwater recharge and dilution combined with excellent habitat is likely responsible for attainment of the assigned EWH aquatic life use in this stretch of stream. Again, a more detailed breakdown of causes and sources will be discussed in the final TMDL report. Spring Fork attainment status had not been completed at the time of this report.