Evidence of leach field seepage determined by microbial and water quality analysis

Managers at Humboldt Redwoods State Park, California, were concerned about sewage leach field seepage into Albee and Cuneo Creeks which are tributaries to Bull Creek. Human fecal wastes in Humboldt Redwood State Park are treated by on-site septic systems. The park leach fields are in close proximity to the two tributaries. Therefore, this study investigated the presence of possible human fecal pollution due to leaching septic systems. Four sampling locations were selected for assessment. The Albee and Cuneo sites are associated with leach fields two other sites were not associated with leach fields and were considered reference sites. Leach field sites were sampled in the upper, middle, and lower reaches of each tributary. A water sample was collected every other week during the summer of 2006 (n=14), with increased sampling effort during peak holiday use. Physiochemical and biological analyses included biochemical oxygen demand (BOD), dissolved oxygen (DO), temperature, pH, turbidity, human sorbitol-fermenting bifidobacteria (HSBB), fecal coliforms (FC) and total coliforms (TC) tests. Membrane filtration was used to isolate human sorbitol-fermenting bifidobacteria (HSBB), fecal coliforms (FC) and total coliforms (TC). Most probable number was also used to enumerate fecal coliforms (FC) and ensure quality control. Isolated fecal coliforms (FC) were confirmed and identified to species using Micro-Id testing kits. Results of the physiochemical parameters measured were consistent with unpolluted water. None of the sites exceeded United States Environmental Protection Agency's fecal coliform level for full body contact in recreational waters (200 CFU's/ 100ml). A two sample t-test (P0.05) indicated no statistically significant difference between the fecal coliform (FC) concentrations in the lower reaches and the upper reaches of the sampling sites associated with leach fields. A statistically significant difference was found between sites associated with leach fields and reference sites. Bacteriological analyses strongly indicate that septic system leaching into nearby creeks, in Humboldt Redwoods State Park, California, is not occurring.