The survey to detect septic system effluent at near-shore locations of Table Rock Lake has been finalized. The $40,000 survey was funded in part by a $24,000 EPA 319 grant and administered through the Missouri Department of Natural Resource (DNR). Table Rock Lake Water Quality, Inc. supplied the required $16,000 matching funds. The contract to conduct the study was awarded to Midwest Environmental Consultants, Jefferson City, Missouri.
The purpose of the study was to determine if the effluent from septic systems located near the shoreline was entering and polluting Table Rock Lake. To detect the effluent, a fluorometer was used to detect optical brighteners in laundry detergent. It was then hypothesized that if the optical brighteners were present, so was septic effluent. A boat was used to troll along developed areas of the lake as water was continuously pumped through the fluorometer. When brighteners were detected the fluorometer would register a "spike". A grab sample would then be taken for phosphorous and E. coli. A secchi disk reading to determine water clarity was also taken. Sampling events were conducted on July 9th and July 25th.
The results show that the effluent from septic systems is indeed entering the lake and causing water quality problems. The levels of phosphorous and E. coli were higher and the water clarity was less in the developed coves as compared with undeveloped coves and the main channel of the lake. (It is noted that although E. coli levels were higher in developed coves, the levels are by far still in the "safe for body contact" range.)
Table Rock Lake was placed on the EPA’s 303(d) list of impaired water in 2002 due to nutrients (phosphorous) which cause an increase in the growth of algae and the decrease in water quality. Although Table Rock Lake Water Quality, Inc. realizes there are many sources of the phosphorous entering the lake, we have taken on as our main focus the septic tank problem. This study was only the first step in our quest to begin projects that we hope will make a difference in improving the quality of water in Table Rock Lake. If you have any questions on this study, contact us.
Click here for a complete .pdf file of the Septic Effluent Study
