A flood in 2006 washed out an upstream dike, inundating the 150-home Alpine Woods subdivision on the Lowe River, built in the mid-1970s, 10 miles north of Valdez, Alaska. The development was unsewered. Fearing contaminated wells, city officials sampled them and found coliform bacteria.
The flood helped bring to light improperly sized onsite systems, faulty installations, failed drainfields, ponded sewage within 10 feet of salmon streams, and the occasional homemade 55-gallon-drum septic tank. In 2007, the city of Valdez annexed Alpine Woods.
In 2008, the city received a grant from the state’s Department of Environmental Conservation to solve the septic problems. Residents shot down the suggested cluster system because it sounded like city sewer to them.
The city’s request for qualifications attracted David Lanning, P.E., of Lanning Engineering in Fairbanks, and Sheldon Shaw, P.E., of Northern Soil & Water in Valdez. They faced high groundwater, power consumption and environmental issues, small lots, the need to reuse as many functioning drainfields as possible, and a city that didn’t want responsibility of monitoring 150 individual systems.
The solution was a pre-plumbed, pre-wired, fully assembled treatment package for each lot, with textile media filter and ultraviolet disinfection. Nine of 20 units in Phase I had been installed by late October, and Phases II and III await funding and the spring thaw.
Site conditions
Soils are gravel river bed with head-size rocks and patches of sand and silt. The seasonal high water table is 12 inches below grade. The topography is flat. The area is rich in salmon streams, and the Lowe River flows past the site to Prince William Sound.
System components
All 150 systems are identical for ease of installation and maintenance. Lanning and Shaw sized them to handle 450 gpd. The major components are:
• 1,500-gallon, dual-compartment fiberglass septic tank. Treatment system package from Orenco Systems Inc., Sutherlin, Ore.
• Biotube pump vault with high- head 1/2-hp effluent pump.
• AdvanTex AX20 secondary treatment fiberglass filter pod.
• Recirculating splitter valve in the riser.
• 24-inch-diameter fiberglass discharge pump basin with ultraviolet lamp.
• High-head 1/2-hp demand-dose pump.
• VeriComm Web-based monitoring system and control panels.
System operation
Sewage gravity flows through a 4-inch PVC lateral to the first compartment in the septic tank, then into the second chamber (recirculation tank), where the pump vault filters out solids. The pump runs 20 seconds every 19.5 minutes, sending 15 gallons of effluent to the filter pod. As liquid trickles through sheets of synthetic textile in the unit, microorganisms remove impurities.
Effluent at the bottom of the pod gravity flows back to the recirculation tank and keeps recirculating until the compartment is full. A splitter valve then alternately doses the discharge pump basin and recirculation tank.
Inside the pump basin, effluent gravity flows through a UV lamp before entering the chamber. The liquid, although now safe for surface discharge, is pumped to the drainfield on demand. Where necessary, replacement drainfields are 30 feet by 15 feet wide with a 2-inch PVC distribution pipe. A manifold directs the effluent to one of five 15-foot by 1/2-inch laterals on 6-foot centers. The laterals are not backflushed.
Installation
Valdez runs on hydroelectric power in summer, but relies on diesel generators when the rivers freeze. Power costs average 30 cents per kWh year-round. Lanning and Shaw determined that the AdvanTex was the most energy-efficient aerobic treatment unit.
System components, shipped nested together, arrived in Anchorage on a barge. Orenco representatives instructed Tom Varney, AdvanTex coordinator at Anchorage Tank, and his employees how to assemble the parts. A special saddle enabled them to glue the 7.5- by 3- by 2.5-foot filter pod to the top of the recirculating tank, then glue the pump basin next to the tank. Risers were glued, too. Once plumbed and wired, the unit was ready to drop in a hole and plug in.
Assemblies were shipped three-by-three on flatbed trucks 306 miles to Valdez. The city hired King Bee Equipment Inc. in Fairbanks to install them, as local contractors lacked large enough equipment. King Bee foreman Shawn Zorich’s first challenge was to transport the equipment 350 miles south on the two-lane Richardson Highway.
The most challenging of the first four installations was a three-bedroom home close to the Lowe River. As soon as the 5-foot-wide backhoe bucket scooped out material, water filled the hole. Zorich used a Tsurumi 6-inch, 36-hp Deutz trailer-mounted diesel-powered trash pump to keep the river out of his 7-foot-deep excavation, then bedded it with 6 inches of pea gravel.
Before setting the tanks, workers water-tested them to make sure the trip hadn’t compromised their integrity. The water also held them in position during backfilling with pea gravel up to the joint on the septic tank. “We poured concrete deadmen on top of the seam rim and around the pump basin,” says Zorich. “The filter pod is buried with its green rectangular lid at grade.”
The pods have 1-inch-thick blueboard sheet insulation glued to the undersides of the lids. Besides pumping warm water from the tank three times per hour, the biological action generates heat. “I’ve opened units in winter and steam rolls out,” says Varney. “People don’t believe it until they see it.”
Valdez is famous for its 10-foot snowfalls, creating another challenge — where to install the filter pods’ air vents so the AX20s can breathe during winter. “I ran them up the wall of a house, up a tree, and even planted a pole next to one system,” Zorich says.
Maintenance
Anchorage Tank holds the service contract, which is for the life of the system and is renewed annually. The local service provider is subcontractor Mike Congel of Valdez Construction Co. E-mails from the VeriComm panels come to Varney’s computer.
“The monitoring system alerts me well in advance of small problems becoming emergencies,” he says. “Tweaking the system via computer is often the only required action.” He faxes scheduled or emergency inspections to Congel.
Orenco provides a detailed checklist for the yearly inspections. Tanks with 24 inches of sludge require pumping. Homeowners receive copies of the inspection reports and a list of calls made by the control panel, identifying what was reported and what the service provider did. The complete system history is stored for Realtors and regulators.
