Adding Four Bedrooms, Doubling the Square Footage

An engineered supplemental treatment system enables major remodeling of home in northeastern California.

Adding Four Bedrooms, Doubling the Square Footage

PEI technical representative Mark Vander-Heyden and Gene Graves from Sustainable Solutions watch Jim Malm of Malm Plumbing scarify the drainfield area with a Kubota L35 backhoe. 

A mandatory onsite system upgrade came with a homeowner’s plans to add four bedrooms to his three-bedroom home in Granite Bay, California, and to expand the footprint from 3,640 to 8,500 square feet. The original 1979 trench-and-stone system also was in failure.

The homeowner hired his neighbor and general contractor, Gene Graves, for the remodel. Graves owns Excellent Construction and sister company, Sustainable Solutions, in Granite Bay. “I was in a quandary with this property,” he says. “Meeting setbacks for a creek, a large pond, a meandering swale, public utilities, and multipurpose easements ruled out a conventional onsite system.” The state also requires a reserve area.

Shell MacPherson, vice president of Sustainable Solutions, stated that septic plans for aerobic pretreatment with low-pressure drip and building plans had been submitted to the county. “It was a stopgap measure that enabled me to begin construction while researching alternative treatments that were more affordable and less maintenance-intensive,” Graves says.

Bob Crandall, then assistant executive officer for the Central Valley Regional Water Quality Control Board, introduced Graves to Advanced Enviro-Septic treatment-dispersal pipes from Presby Environmental Inc. (PEI). He also educated Placer County health officials about the technology. They approved it almost a year later in June 2017. By September, Graves installed the first Advanced Enviro-Septic system in the county.

Site conditions

Soils are sandy loam with a percolation rate of 14 minutes per inch. The 2.3-acre lot has a 9 percent slope.

System components

MacPherson designed the system to handle 1,050 gpd. Major components are:

2,000-gallon two-compartment septic tank, no effluent filter (Georgetown Precast)

1,500-gallon dose tank with model PF100512 1/2 hp effluent pump in Biotube pump vault (Orenco Systems)

Concrete distribution box with velocity reduction

360 feet of Advanced Enviro-Septic treatment-dispersal pipes, vented (PEI)

781 square feet of ASTM C33 washed concrete sand with no more than 2 percent fines passing a No. 200 sieve

Simplex control panel with alarm (Orenco Systems).

System operation

Wastewater flows by gravity 46 feet through a 4-inch ABS house lateral to the septic tank, then to the dose tank. (Graves will adjust the pump cycles and volume once the homeowners take occupancy.) Doses travel 55.5 feet through a 1.25-inch PVC pipe that rises 15 feet and ends in a 90-degree velocity reduction tee in the distribution box. Flow equalizers in the box distribute effluent equally to two serial 180-foot-long sections in an elevated bed. The first section has six 30-foot laterals, and the second has two rows of 30-foot laterals and three rows of 40-foot laterals. Spacing is 1.5 feet on center.

Each 12-inch Advanced Enviro-Septic tube has a corrugated, perforated plastic pipe where treatment begins. Ridges on the pipes increase surface area and circulate effluent uninterrupted, cooling it to ground temperature. Skimmers at each perforation help retain grease and suspended solids, protecting the three outer textile layers from clogging.

The inner first layer of white Bio-Accelerator develops the biomat, screens more solids, and evenly distributes effluent along the length of the laterals. The second layer, a mat of coarse green plastic fibers, traps more solids and creates a massive suspended growth area for aerobic bacteria. The third and outer layer of black geotextile fabric protects the inner layers and provides more surface area for nutrient uptake. As the sand bed wicks liquid from the fabric, it transfers air to the microorganisms. Third-party testing showed the system treats effluent to less than 2 mg/L TSS and CBOD and to 218 CFU/100 mL fecal coliform.

Preparation

Graves, MacPherson, and chief executive officers Lance Bates and Jim Rentschler from NexGen Septics, organized the installation into a Field Day. Graves purchased all the onsite components, including the Advanced Enviro-Septic system from PEI distributor NexGen Septics.

In preparation for the event, Jim Malm of Malm Plumbing used a Kubota L35 backhoe to excavate the 15- by 20- by 10-foot-deep hole for the two tanks. The driver from Georgetown Precast set them on a 6-inch bed of decomposed granite. “This native material resembles coarse sand and is beautiful to work with,” Graves says.

His crew then plumbed the tanks, decommissioned the original septic tank, and prepared to install 80 percent of the drainfield between clusters of mature oaks and the home, side property access drive, and swale.

Drivers stockpiled 24 tons of concrete sand on an area Graves had graded below the drainfield. “It’s important to keep the sand clean,” he says. “I didn’t want it too near the dusty drive.”

The location for the 40-by-18-foot-wide drainfield had a 7.5 percent slope. Malm scarified the area, then workers staked it out with 2-by-6-inch form boards. After the crew brought in 6 inches of concrete sand, they dragged a screed board over the material to scrape and smooth the top layer, leaving a level profile.

“We set it up so people could see the concrete sand below and above the pipes, and we exposed some end caps,” Graves says. “This event was more about giving people a chance to see the system in cross section and understanding how it works rather than installing pipes.”

To that end, Graves also exposed connections to the septic tank, pump tank, and bypass vent line. “The system depends on passive air transport to support aerobic bacteria,” Graves says. “Convection draws air from the 4-inch screened low-vent PVC pipe in the drainfield, through the system, and out the roof vent on the house. However, the pump acts like a gate valve and interrupts the flow.”

To restore the flow, the system requires a 4-inch ABS bypass vent from the dose tank to the distribution box. The bypass also mitigates hydrogen sulfide corrosion by allowing heavy gases to escape.

Field Day

The event attracted 25 attendees including installers, engineers, contractors, officials from the Registered Environmental Health Specialist program, an architect, and community homeowners. PEI technical representative Mark Vander-Heyden from New Hampshire explained the details of the system. Graves, Bates, and Rentschler assisted during the Q&A session.

For the hands-on portion, Vander-Heyden encouraged participants to snap fittings and couplers together and lay geotextile fabric. Assembling the 10-foot-long pipes went quickly. Corrugations on them matched those on 8-inch-wide couplings that locked around the pipes like zip ties.

Graves made some plywood fixtures with a 4-inch spine to space the pipes on center and hold them in position during backfilling. “The spine enables us to screed off an even layer of concrete sand over the pipes before adding 6 to 9 inches of topsoil,” he says.

One neighbor hired Graves to replace his failing trench-and-pipe drainfield with the Advanced Enviro-Septic system.

Maintenance

No maintenance contract is required. Sustainable Solutions will respond to alarms and recommend when to pump the septic tank.



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