Before Vermont’s revised waste-water regulations went into effect on July 1, 2007, some North Ferrisburg residents decided to upgrade the systems on their lake homes to avoid dealing with the state.
Richard Hurd, chairman of the Long Point Homeowners Association, led by example. His 100- by 100-foot lot had a sequencing batch reactor installed in the early 1970s as part of a dry well system discharging into Lake Champlain. Hurd called Eli Erwin, environmental scientist at Lincoln Applied Geology Inc. in Lincoln, Vt., who suggested retrofitting the module with ultraviolet light disinfection.
When Brad Fischer of Bundy’s Sewer and Drain Inc. in Jericho inspected the unit, he found insufficient oxidization and broken baffles that allowed the system to pump itself dry. The unit was unsalvageable. “This site was very tough because the only room for a replacement pretreatment unit was on a deck overlooking the lake,” says Fischer. “That really limited our options.”
The solution was a sequencing batch reactor that Vermont had approved for pretreatment in 2007. The integrated, compact unit was the smallest of its kind. It was also transportable — an important feature, since the site was inaccessible to large equipment and all work was done by hand.
Site conditions
The clay/ledge soil has a percolation rate of 120 minutes per inch or more. The water table is four inches below grade. A slope with a 3:1 grade rises at the side of the house, ending in a 6-foot-high stone retaining wall abutting Shore Road. An L-shaped concrete sidewalk comes down the hill and around the side to the back of the house, which faces the lake.
System components
Erwin sized the system to handle 360 gpd. The standard is 375 gpd for a three-bedroom home, but pretreatment allows a 50 percent reduction in size. The system’s major components are:
• 500-gallon Model CA-5 sequencing batch reactor from Cromaglass Corp., Williams-port, Pa.
• 252 feet of 3/4-inch Waste-flow plastic driplines on 1-inch centers with valves, headworks, and control panel from Geoflow, Corte Madera, Calif.
System operation
Wastewater gravity flows thorough a 4-inch, cast-iron lateral that surfaces after passing beneath the sidewalk, slopes gently for three feet, and enters the 6-inch inlet at the top of the three-chamber reactor. (The deck on which the reactor rests is six feet lower than the sidewalk.)
Flow enters the solids retention section, where a non-corrosive screen separates and retains inorganic solids. One submerged 1/3-hp aeration pump in the aeration section forces mixed liquor through the screen. The resulting turbulence, more vigorous than the action of a washing machine, breaks up organic solids.
Liquid and small solids pass through the screen into the aeration section. The pumps, with venturi aspirators, receive atmospheric air through individual intakes. The liquor is mixed continuously with air for aerobic treatment. After two hours, a pump transfers the treated mixed liquor to the clarification-discharge section, overfilling it. The excess spills through overflow weirs back into the aeration section. When the transfer is completed, solids separate under quiescent conditions for 45 minutes.
After the settling period, a 1/2-hp turbine pump with Sim/Tech filter discharges effluent through 1-inch PVC Schedule 40 pipe 35 feet to the drainfield. A submersible pump returns the sludge at the bottom of the clarifier to the aeration section. It takes less than four hours for an 80-gallon batch to reach the drainfield. Fischer programmed the system to cycle four times a day.
Installation
Hurd reinforced his pressure-treated deck with a steel I-beam to accommodate the reactor. Fischer removed the sidewalk guardrails to make it easier to install the unit. “The most challenging part of the installation was the site,” says Fischer. “We stockpiled materials on Shore Road, then dumped them over the 6-foot-high retaining wall directly into the 20- by 15-foot area for the drainfield.”
Before building the absorption bed, Fischer’s four men lowered a vacuum hose over the stone wall and pumped out the old sequencing batch reactor, which was occupying the space for the drainfield. They then put a lifting harness around the module and used a Case backhoe to hoist it onto a waiting truck. The new 7-foot, 11-inch square by 5-foot, 7-inch high fiberglass module was lowered the same way.
“We built a small skid from 6-by-6 timbers, hoisted the 704-pound tank onto it, then pushed and shoved it along the sidewalk to the deck,” Fischer says. Brute strength controlled the rate of descent. The plumbing inside the tank was unaffected by the jerky move. During normal operation, the module is half full of water, bringing its total weight to more than 2 tons. Its weight alone holds it in place. The module is fully exposed to the elements.
Erwin’s plans specified a mound sand absorption barrier beneath the driplines. Because the property sloped toward the lake and to meet regulations, the men first built three 2-foot-high retaining walls from pressure-treated 6-by-6 timbers to prevent the prewashed sand from eroding and to enhance the bed’s appearance. The fourth side was the stone retaining wall. The backhoe dumped and stockpiled sand on one end of the drainfield, while the men leveled it with shovels and rakes to a depth of 18 inches. No native soils were excavated.
On top of the sand went fourteen 18-foot-long laterals on 1-inch centers covered with 12 inches of bark mulch. “The Geoflow package contains valves, headworks, and control panel,” says Fischer. “When the pumps shut off, the valves drain back, so no liquid is left in the driplines. That’s important because Vermont can have frosts and freezing weather through May.”
To activate the system, Fischer pumped mostly liquid from another septic tank and discharged it into the reactor’s solids retention section. “Because this is a seasonal home, we shock-load the system so it starts faster,” he says. “It’s only aerating, not discharging, and runs for about a week before the homeowners arrive.”
Maintenance
The state requires an annual inspection, which Bundy’s Sewer and Drain Inc. does on a service contract. Because the home is seasonal, a technician pulls the pumps every fall and replaces them in spring. Any liquid in the reactor is pumped out in autumn to prevent it from freezing. Should a problem arise during summer, audio and visual alarms in the house alert the owners, and they call Bundy’s. The system is dormant in winter.
