In 2008, the nonprofit Turning Point Community Development Corporation opened on the property of a former car dealership in Henderson, North Carolina, to provide a much-needed community center offering preschool and educational programs for children.

However, an application to become a licensed child care center required a septic system inspection. The site’s existing septic system was declared noncompliant by the Vance County Health Department because the original septic tank was installed across property lines.

Turning Point engaged Agri-Waste Technology to design a customized, compliant wastewater system. Following a site evaluation, AWT proposed a wastewater system that would collect, filter and disinfect the facility’s wastewater prior to discharging the treated effluent to a surface water body.

However, the only reasonable destination for effluent discharge was a small existing pond located about a half-mile away on an adjoining property owned by a solar farm. Turning Point addressed this challenge by negotiating an easement with its neighbor to allow placement of the discharge line and use of the pond.

AWT’s design utilized a septic tank and recirculating tank with dual aerobic filter treatment units that work in a parallel arrangement. After passing through the UV system effluent is discharged, in a demand dose arrangement, to the pond.

AWT provided Turning Point with a list of AWT-recommended installers. Turning Point selected Full Circle Environmental in Clayton, North Carolina, to install the system. 

SITE CONDITIONS

The wet soils of the site, a former car lot, were unsuitable for traditional drainage. The soil around the buildings was heavy, expansive clay, making excavation challenging.

SYSTEM COMPONENTS

Serving about 30 children and associated staff members, the hydraulic flow for the site measures under 1,000 gpd so treatment capacity was set at 765 gpd by the county.

Major components of the system are:

• 1,500-gallon dual-compartment precast concrete septic tank (Shoaf Precast) with Orenco Biotube effluent filter and two 24-inch risers (Orenco Ultra-Rib PVC) and fiberglass lids (Orenco)
• 1,775-gallon dual-compartment precast concrete recirculation tank (Shoaf Precast) with two 24-inch risers (Orenco Ultra-Rib PVC) and fiberglass lids (Orenco)
• Two Orenco AdvanTex AX20 Pods
• Orenco UV-125/31-P UV disinfection unit
• Orenco PF500511 4-inch submersible effluent pump
• Model 151 Dose-Mate 1/3 HP pump (Zoeller Pump Co.)
• Orenco VeriComm AXB1 Simplex Control Panel

All Orenco products were supplied by AQWA, located in Wilson, North Carolina.

SYSTEM OPERATION

The system is gravity fed where possible, with slopes achieving a minimum of 1% through a pipe system consisting entirely of Schedule 40 PVC. Wastewater runs approximately 30 feet from the main building through 4-inch drainline to the septic tank for primary treatment. Effluent flows by gravity from the septic tank where it passes through an effluent filter and enters an adjacent recirculating tank.

From the recirculating tank, effluent is pumped approximately 8 feet through a 2-inch supply line to the first of two AdvanTex AX20 aerobic filter treatment pods installed in parallel, with each pod capable of processing 500 gpd. Effluent from the first treatment pod returns to the recirculating tank. Effluent from the second pod flows through an Orenco RSV3Q splitter valve and either returns to the recirculation tank or continues to the UV system.

Sufficiently treated effluent leaves the recirculating tank and enters a single-bulb Orenco UV Disinfection Unit, housed in a vault built from a 24-inch Orenco Ultra-Rib PVC Access Riser. UV-treated effluent is pumped into a 1.25-inch effluent discharge line, which runs 2,000 feet to the outlet pond. The end of the line transitions to 10 feet of 4-inch drainline and a 4-inch TUF-TITE Speed Leveler, before effluent makes a final journey through a screen to an excavated swale in the pond bank.

INSTALLATION

Full Circle Environmental specializes in complex installations and has worked frequently with AWT. President Zach Woody also frequently calls on AWT to design systems his company installs.

“The key to this installation was careful planning,” Woody says. “We made four or five site visits prior to beginning construction to ensure all site limitations were considered and a well-developed construction plan was implemented alongside AWT.”

While the three-acre site offered generous working space, Full Circle had to work within the schedules set for the center, taking extra care to avoid times and areas where children were playing. The contractor brought a crew of six workers to the site.

Woody employed an E85 compact excavator, an E50 compact mini excavator, and a T590 compact track loader, all from Bobcat, to move dirt. A Vermeer RTX 450 ride-on tractor was used to excavate the drainline trench to the pond.

“The heavy clay on the site was unsuitable for backfilling and we performed a lot of dewatering,” says Woody. “During construction we also encountered buried asphalt and concrete and trash pits.”

Soil from the site was replaced with both No. 67 (3/4-inch) and No.78 (3/8-inch) pea gravel topped with imported, screened topsoil. 

The excavation for the septic tank and recirculating tanks was dug to about 13 feet. Tanks were placed on a bed of gravel and buried with a minimum of 12 inches of soil cover. Tank risers extended a minimum of 6 inches above ground. 

The AdvanTex AX20 Pods were bedded on gravel about 6 feet from the septic and recirculating tanks, and then buried to allow for 3- to 6-inch exposure. All discharge and supply lines were buried to approximately 36 inches with allowance for gravity drainage. 

The site’s three-phase power supply was adjusted to single phase at the system control panel to accommodate the range of electrical equipment required by the new septic system. 

Full Circle excavated the trench for the lengthy drainline to about 3 feet. The swale at the effluent pond is constructed from a 2-by-6-foot installation of Class B riprap on No. 57 (1-inch) gravel for final aeration. 

The entire project required about two weeks to complete. AWT is taking on the maintenance contract for the system.

INNOVATIVE APPROACH

“Sometimes people don’t know that there is the potential for a system like this,” says Kevin Davidson, vice president of engineering at AWT. “While it’s expensive, it can bring a lot of value to small commercial or residential property owners faced with a failing wastewater system.”

Chalis Henderson, executive director of Turning Point, agrees.

“AWT and Full Circle provided us with a very innovative system, and we’re able to accomplish our goals and meet the needs of the community because of it,” she says. “People don’t understand all that goes into operating a facility and a community program, but even down to the septic system, those things matter.”