GEOCHEMICAL INVESTIGATION OF LOWER HEMLOCK CREEK, COLUMBIA COUNTY, PA

The Hemlock Creek watershed covers approximately 40 km² just northwest of the town of Bloomsburg, PA, and has been designated a cold water fishery, though it is currently listed as impaired due to siltation. Hemlock Creek is a tributary to Fishing Creek, and a previous study that sampled water from the confluence of the two creeks measured alkalinity and conductivity values more than three times higher in Hemlock Creek than in Fishing Creek. To investigate potential sources of elevated conductivity and alkalinity, samples were collected at 5 sites along lower Hemlock Creek downstream of a major retail development, an auto auction, some agricultural property, and a waste water treatment plant, and in Fishing Creek both upstream and downstream of Hemlock Creek’s point of confluence. Dissolved oxygen, conductivity, pH, and temperature were measured in-situ. Turbidity, acidity, and alkalinity were measured in the lab immediately upon return from the field. Concentrations of selected metals and common anions were measured via ICP-OES and ion chromotography, respectively. The pH (7.36-7.79), dissolved oxygen (10.05 to 10.675 mg/L), and alkalinity (14.67 to 45.67 as mg/L CaCO₃ – less than half the value detected in the previous study) were consistent across the sampling locations, showing no influence from a point source. These values also met criteria for Hemlock Creek’s designated use for cold water and migratory fish. Turbidity, on the other hand, ranged from 1.36 to 21.82 NTU, well above the TMDL of 1 NTU. The high values of conductivity (approximately 220 to 240 μS/cm) in Hemlock Creek paired with the large shift from 85 μS/cm to 165 μS/cm in Fishing Creek suggest that Hemlock Creek is increasing the conductivity of Fishing Creek. Several metals (Al, Ba, Cu, Fe, Mn, Ni) were detected in both filtered and non-filtered samples at concentrations well below levels of concern for aquatic life. Metals in Hemlock Creek do not appear to influence concentrations in Fishing Creek, with the exception of anomalous elevated concentrations of Al and Cu in filtered samples. These data should provide a good baseline against which to compare future water quality analyses.