areas. Meanwhile, health officials 

 began to call the risk of contaminated 

 drinking water in some areas "acute." 



Agencies began to crack down. New 

 "teeth" in the Ground Absorption Act 

 made permits harder to come by, and 

 applications for new construction were 

 turned down by the hundreds. But 

 there was no hard evidence about 

 either the flow of wastewater from sep- 

 tic tanks into estuaries, or about the 

 contamination of groundwater. 



In response, Sea Grant funded 

 another Carlile project, this time 

 geared to the islands. Craig Cogger of 

 NCSU is conducting most of the 

 studies while Carlile is on loan to 

 Texas A & M University. Cogger 

 recently completed research on a pro- 

 ject conducted for the N.C. Division of 

 Health Services and funded by the 

 Coastal Plains Regional Commission. 

 The study surveyed 17 sites in coastal 

 North Carolina and found that 16 of 

 the septic systems did not have a 

 minimum 12-inch vertical separation 

 from the seasonal high-water table. 



Bobby Carlile with mound system 



Many of the systems, he found, were 

 saturated almost all year, with the ef- 

 fect of releasing raw sewage into 

 groundwater and estuaries. But the 

 study did find that low-pressure 

 systems in the group performed much 

 better than conventional ones in 

 marginal soils, although they also per- 

 formed poorly on sites saturated most 

 of the year. 



For his Sea Grant project, Cogger is 

 setting up test sites at West Onslow 

 Beach. There, he will operate model 

 septic systems, including conventional 

 septic tanks and the low-pressure 

 alternatives. Using various loading 

 rates, dosings and separation dis- 

 tances, Cogger will study each com- 

 bination for the movement of effluent 

 through the soil. 



Cogger will also use "tracer" com- 

 pounds to monitor the flow of 

 wastewater horizontally through 

 water-saturated ground. The studies 

 are designed, he says, to show just how 

 far contaminants travel in each direc- 

 tion, and how complete is the treat- 



Sticking up for the lowly septic tank 



The very words have a malodorous, subterranean tone: 

 septic tanks. But are they really so villainous as their 

 reputations? 



Dennis Osborne, a Sea Grant researcher and member of 

 the NCSU Soil Science Department, says no, they aren't. 



"The ones that work, work beautifully," Osborne says. 

 "It's the best, low-cost, natural treatment system there 

 is." 



Osborne says that in conventional septic systems, work- 

 ing properly, things happen this way: Waste collects in the 

 septic tank, where it decomposes through the anaerobic 

 action of bacteria. From there, liquids containing nitrogen 

 and phosphorous are released into perforated drain lines, 

 laid in gravel-lined trenches about three feet under 

 ground. The lines are laid so that gravity disperses the li- 

 quids through the absorption field, which is usually plant- 

 ed with grass. As liquid passes through the soil, some of 

 its suspended substances are digested by microbes, and 

 others attach themselves to particles of soil, until the 

 wastewater is thoroughly filtered and treatment is com- 

 plete. The only maintenance normally required is to pump 

 solids from the tank every three or four years. 



But things can go wrong. If lines are laid in wet soils, 

 there is little or no treatment, and raw sewage seeps out of 

 the system. Or, if lines are laid in impervious clay, very lit- 

 tle of the wastewater will be absorbed. Instead it rises to 

 the surface. 



Osborne says the new alternative systams he's been 

 working with overcome some of these limitations by dos- 



ing the soil under pressure. The controlled dosing means 

 that drain pipes can be installed in trenches as shallow as 

 12 inches, well within the "dry" range of many coastal 

 soils. Also, the shallow lines can be snaked into wooded 

 areas, avoiding the need to clear-cut trees. 



But Osborne cautions that these new systems require 

 maintenance, and that they can be misused. "We require a 

 back-up pump on the systems we in- 

 stall, and an alarm to warn you of a 

 breakdown," he says. Distribution of 

 the effluent must be checked in 

 standpipes attached to the lines. And, 

 the system must be protected from 

 grease. 



"Fast-food restaurants produce a lot 

 of grease," Osborne says. "They use 

 water at a hundred-and-eighty 

 degrees, and at that temperature, the 

 grease is emulsified. It just bypasses 

 the grease trap and winds up in the 

 lines, where it sort of coagulates and 

 seals everything up." 



Osborne nevertheless prefers, for many sites, a well- 

 designed septic system to the "package" treatment plants 

 that chemically treat wastes and serve multiple buildings. 



"The cluster systems, I've seen work fine, when they're 

 designed adequately," he says. "But they can also impose 

 an unnecessary cost. You pay a lot to simulate what hap- 

 pens naturally in the soil." 



Osborne 



