Weather, variable soils and freeze-thaw
cycles are just a few
of the conditions that keep work interesting for Alpine Excavating
By Rosalie E. Leposky
Matanuska-Susitna (Mat-Su) Borough, near Anchorage, Alaska, challenges onsite installers to adapt products used in the lower 48 states to extreme conditions. Many standard design and construction methods don’t apply in Alaska because of complex soil conditions and severe weather.
“Ensuring our workers’ personal safety on jobsites requires significant adjustments in work methods and management style,” says Daniel J. (Dan) Tucker, co-owner of Alpine Excavating, LLC. Workers face challenges such as:
• Summers with extra-long daylight and winters with only a few hours of light.
• Below-zero temperatures in which construction sites must be protected against freezing overnight.
• Ground that may stay frozen more than six months down to four feet
• A freeze/thaw environment that cracks and breaks septic tanks.
• Jobsites where groundwater is close to the surface or even above the surface for part of the year.
• Work sites miles from the
nearest material sources, requiring extra planning for equipment and materials.
• Work sites that a building inspector may never see – inspections are based on photographs taken by the property owner or installer.
Beyond the urban fringe
Mat-Su Borough starts 45 miles east of downtown Anchorage and 35 miles from the edge of the city. Its population of 55,747 sprawls across 25,233 square miles, about the size of West Virginia.
This section of Alaska has experienced cycles of boom and bust. The population swelled during construction of the Trans-Alaska Pipeline System, and again in the mid-1980s. During bust periods many construction workers left and abandoned their homes.
|Now, almost three
decades later, these dwellings are again in use, with septic systems that
are near the end of their life and in need of maintenance. New home sites
also are under development.
To service Mat-Su’s growing population, Dan joined Thomas Stoelting II and his wife, Arlene, to form Alpine Excavating in April 2002. The Stoeltings already owned Alpine Septic Pumping Inc., which provides many septic repair and installation leads to the excavating company.
To streamline operations, Alpine Excavating leases most of its equipment and subcontracts labor. The company owns a Link-Belt 2650Q excavator. Specialties include excavating home sites, installing and repairing septic tanks and installing water lines from wells to houses.
|Equipment getsa a real workout in the tough soils and winter conditionas around Matanuska Susitna (Mat-Su) Borough.|
Dan is a long-time Alaska resident with extensive experience in excavating and firefighting. He saw Alaska for the first time in 1969 as an airman-firefighter, flying into Elmendorf Air Force Base in Anchorage. After his military service ended, he worked 29 years for the Anchorage fire department, rising to battalion chief. Although now retired, he remains on call for emergencies, including oil spills.
|On his off-days as
a firefighter, Dan learned excavating. “I worked part time digging ditches,”
he says. For a while, he co-owned TNT Construction, founded in 1973, with
his brother, John, and Mike Nelson, a fire department co-worker. John died
in a 1976 plane crash.
“I taught my brother and Mike excavating,” says Dan. “TNT Construction excavated residential lots, building foundations, septic systems, water lines – anything in the ground. We set our schedule around our fire department work. As our fire department careers took up more time, the company just dissolved. We sold off all of our equipment. From 1978 to 2002, I worked free-lance for other people who needed an operator. One of the companies for which Dan worked was Alpine Septic Pumping.
Making it legal
The Alaska Department of Environmental Conservation (ADEC) regulates the installation of onsite systems. Three groups can legally install and document systems:
• Property owners who have passed ADEC courses.
• Excavators whose work is documented by a registered engineer.
• ADEC-certified installers who have passed ADEC courses and are licensed to perform soil
Homeowners who have bootleg systems are fine until they try to sell their homes and a bank asks to see the onsite system documentation. “Typically, they have to call an excavator to bring their system into compliance, which may mean the installation of a whole new system,” says Dan.
In Alaska, all septic tanks and leachfields must be located at least 100 feet from any waterway or a building’s water well. All components must have at least four feet of ground cover. “In some cases, the four feet may be reduced by the equivalent of one foot of fill replaced by one inch of insulated blue board,” Dan says. “The minimum coverage allowed is two feet of soil and two inches of extruded polystyrene foam type of board, such as high-density foam insulation. There must always be at least two feet of soil coverage over the insulation. Additional insulation is allowed.”
Alaska law requires four photographs to be taken during installation and submitted to ADEC. One photo must show the perspective of the project, usually with the house in the background, the septic tank in the hole, the inlet or outlet end clearly identified, and the manufacturer’s name and the capacity in gallons clearly visible.
The second photo must show the leach area – a deep trench or field – completely excavated and ready for backfilling to begin.
The third photo must show the leach area with rock and pipe topped with filtration fabric. The fabric prevents the backfill from filtering down to contaminate the media. There are six inches of rock below the pipe, four inches around the pipe and two inches above the pipe, covered by a layer of filtration fabric.
The fourth photo must show the project’s finished grade, level except for a slight mound over the tank so that a hole doesn’t develop when anticipated settling occurs.
Stone arrives for a drainfield installation.
Because of travel distances and the remoteness of some work sites, trucking gravel for systems can be costly. “Sometimes we have to move septic rock one bucket at a time from our truck,” says Dan. Alpine sometimes creates leachfields using chambers made by Infiltrator Systems Inc.
A typical installation takes two men one or two days. A certified installer must be present to sign off for installations. “When I arrive on an installation site, my typical procedure is to walk around and inspect the site,” says Dan. “I locate the existing septic tank and leach system, the freshwater well, and the wells and septic tanks or leach systems for any neighboring properties.”
Test holes tell
Then he must dig a test hole to determine the soil type for sizing the system. Every leach system, new or old, must have a test hole.
|“Test holes tell me everything,” says Dan. “Typically I do them very early in
the job. They provide water level, and seasonal high-water level, impermeable
level, if there is one, and the soil type. Typical sandy or gravel soil through
which water flows freely doesn’t need a perc test, but less permeable soils
Only a registered engineer can perform a perc test. Doing test holes early in Alaska’s long summer days allows Dan to call an engineer to arrange for his visit later the same morning. After the test hole is dug, if an engineer isn’t required, Dan can start at the house to excavate for a septic tank.
Mat–Su soils encompass the full spectrum of Alaskan soil types. “We have installed septic tanks and leachfields in them all,” Dan says, “including alpine tundra, dry clay or hard pan, gravel, sand and glacial till with high concentrations of silt that turn to dust when disturbed. Silt mixed with water creates a quagmire.”
Ditch design and depth must account for loose side materials falling into the ditch, Dan says. “We dig the ditch, spread a layer of rock over the bottom of the ditch, then put in PVC piping. We lay filter fabric over the rock and around the pipe, backfill the ditch, and level it.”
Repairs to older systems make up a substantial share of Alpine’s business. Dan says many repairs become necessary when frost forces the foundation cleanout pipe to the surface, creating a void between the pipe and the sewer line. Then dirt and rocks fall into the sewer line and block the pipe.
This frequently occurs when cast-iron sewer pipes are connected with a no-hub connector. Newer systems use ABS (acrylonitrile-butadiene-styrene) pipes between the buildings and septic tanks, and PVC pipes connecting the septic tank to the leachfield. The PVC pipes are solvent-welded or glued.
“Just outside the foundation, ABS pipes have been attached to the old cast-iron pipe with a four-inch no-hub or rubber connector,” says Dan. “The new pipe and connection can settle to a lower level and restrict flow. Our job is to repair and replace these pipes and connections with ABS pipe fittings and connections that cover the cast-iron pipes. We make sure the repairs are leak-free.”
Locating utility lines is important when working below grade. In winter, “It’s an extreme challenge to avoid hurting utility lines,” Dan says.
Freeze and thaw
Cold weather is also hard on septic tanks. “Fiberglass and plastic septic tanks fracture and collapse in our cold climate from installation depth and the pressure of our freeze-thaw cycles,” says Dan. “Most of the septic tanks used here are steel, which rusts. Steel tanks have a life expectancy of 15 to 25 years.
“When working at a location with a high water table, sometimes we can’t pump out enough groundwater to install the septic tank, so we have to sink them into place. Typically, we dig a foot or two below the water level to install tanks.
“We dig underwater completely blind, then fill the tanks with enough water to sink them to the bottom of the hole. To keep the septic tanks in the ground, we sometimes add several tons of concrete block, similar to highway median barriers across the top of the septic tank, except where the pump-out connector tubes are located. If we don’t use the blocks, the rising water table may force our tanks out of the ground.”
Meeting such challenges is all in a day’s work for Alpine Excavating in its efforts to install quality onsite systems.
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