Preparing the site for a new school
Fenced in sewage lagoon was removed and the site remediated for one wing of the Kipnuk school addition.
Photo by Nichelle Seely
When I visited the village of Kipnuk in the spring of 2010 to inspect the recently completed teacher housing, I noticed a pervasive odor near the main entrance of the school. The adjacent sewage lagoon had overflowed and some of the runoff had accumulated, along with snowmelt, in a broad pond at the base of the entry ramp. Two girls in rubber boots splashed through the water, laughing as they kicked through chunks of ice.
The shortcomings of the sewage treatment pond were well-known by the villagers, and I learned that they dealt with it in practical rural style. During the winter, a man with a chainsaw would carve out chunks of frozen effluent and drag them out of the lagoon and onto the river ice, to be carried out to sea during spring breakup. Not a great solution, but surely healthier than allowing liquid sewage to flood the schoolyard.
When the Lower Kuskokwim School District awarded Bezek Durst Seiser Architects and our team of consulting engineers the opportunity to renovate the old school and design a new addition, we discovered the site was also contaminated in other ways. Spillage from the district fuel tank farm and individual residential tanks on the property was going to require remediation of the surrounding soils. Several small structures slated to be demolished contained asbestos and other hazardous materials. In addition, when the geotech team extracted core samples for analysis, a spark from the machinery ignited a spurt of flame from the newly drilled hole. The ground was permeated with methane gas.
BDS has a lot of experience designing for rural Alaska, and—with the exception of the methane—we knew we would encounter these kinds of environmental issues. Problems like these are common in these roadless areas so isolated from urban infrastructure. Even the presence of methane gas is not unheard of—it bubbles up in tundra lakes and emanates from landfills. Anywhere significant amounts of organics are decaying, it will be found.
We engaged R&M Consultants Inc. of Anchorage to perform civil engineering tasks, Oasis Environmental to help us deal with the sewage lagoon as well as assist with the contaminated soil, and EHS-Alaska for their expertise in hazardous building materials. Together with our consultants, BDS developed a plan to address the various problems.
Kipnuk cemetery with backhoe in distant background.
photo by Nichelle Seely
Removing the Sewage Lagoon
First on the list was the lagoon. Not only was its proximity to the school unhealthy, it was right where we needed to build one wing of the addition. Fortunately, the village had just completed a new centralized treatment pond. Now it was a matter of transferring the effluent, treating and capping the sludge, and turning the area into a buildable site.
The design team developed a process plan to take place in 2011. There was plenty of time—the new school wasn’t slated to begin construction until the summer of 2012. LKSD successfully transferred the liquid from the old lagoon to the new one via pumps and hoses. Only the sludge remained. The plan called for treatment with quicklime, which would dry it out, raise the pH and deactivate the bacteria and viruses. Afterwards, sandy soil from the surrounding berm would be mixed in, the treated sludge would be covered with geotextile, and the remaining swale would be capped with gravel to make a suitable building site.
However, nature does not consider the plans of humanity. Before the sludge could be treated, on Nov. 9 a hurricane-force storm of unprecedented proportions swept across the Bering Sea. The storm surge backed up the river, flooded the village and refilled the sewage lagoon with brackish water. Residents took shelter in the school, high and dry on its pilings. Winter had arrived with a vengeance, and if the water were not removed within the next few days, it would be impossible to empty the lagoon before freeze-up. In addition, the bags of quicklime had gotten wet in the flood. Although the material was still useful, it had lost its potency, and more would be needed to successfully treat the sludge.
When Plan A doesn’t work, it’s time for Plan B. The school district applied to the Alaska Department of Environmental Conservation for emergency authorization to pump the contaminated brackish water away from the community. LKSD personnel again emptied the lagoon using a specially designed system to minimize entrainment of solids. The district and BDS design team agreed that the treatment of sewage solids could be added to the overall school project and become part of the task of the winning contractor. As this article goes to press, the plan is for LKSD to once again empty the lagoon, mobilize additional quicklime to the site, and turn the site over to Dokoozian Construction to finish the treatment and earthwork. If all goes well, the lagoon will be gone by the end of the summer, and ready to accept the new building foundation.
Boardwalk bridge over utilidor and water line.
photo by Nichelle Seely
Contaminated Soil Mitigation
Although the problem of open sewage is the issue that grabs the most attention, no less important is the problem of contaminated surface soils. As with most rural Alaska communities, Kipnuk runs on imported fuel. Individual houses have day tanks for diesel and propane; the village has a large tank farm where tens of thousands of gallons of fuel are stored, including aviation fuel. As a separate entity, LKSD maintains its own massive storage tanks and an intermediate tank to run the school.
All this fuel storage and use results in leaks and spills. This is where the expertise of Oasis Environmental comes in. Their methodology is straightforward and effective. First, a conceptual site model is developed, identifying everything on the site that might be a source of contamination. Second, a field screening technique is identified to establish the clean and contaminated areas. Third, soil samples are collected and sent to a lab to determine the type and concentration of the contamination, if any.
In the field, the process works like this: a representative from Oasis would approach a potential source of contamination—for example, a day tank. Guided by fuel odors and staining and field screening using a photoionization detector (PID), the field team assesses the site. Samples are heated and the PID utilizes the air given off to determine the order of magnitude of the contamination, informing the field team whether the amount merits additional investigation. Oasis Environmental then correlates the field screening with the laboratory analytical results to establish the extent of required clean-up.
Once the extent of contamination is determined, the design team has to figure out what to do with it. Soil with low concentrations of contaminants (below state cleanup levels) can be left in place. Higher concentrations of non-leaching substances can be removed and placed in the local landfill, without posing a danger to surrounding soils and water sources. Severely contaminated soil or that which contains leachable substances or hazardous chemicals must be removed and shipped to a special landfill designed to handle toxic materials. The nearest ones to Alaska are in Oregon.
On a messy jobsite surrounded by rumbling machines churning up the muck, quality control is a necessity. Oasis Environmental will send a representative out with the building crew to identify which soils can go to the landfill and which must be backhauled. It’s all part of the intricate dance of compliance, self-enforced by the BDS design team and law-abiding construction contractors.
Hazardous Material Mitigation
The third source of toxics is hazardous materials in existing buildings. The area slated to host the new school addition is cluttered with fuel tanks, water tanks, boardwalks and buildings, all of which must be demolished to make way for new construction. Some of the buildings will be dragged away for reuse; some of the material is salvageable and will be given to the community. Some of the material is recyclable—and to spare the small village landfill which will be strained by coming construction waste, BDS specified that jobsite metals are to be collected and backhauled for recycling. However, hazardous materials cannot be reused or recycled or simply thrown away. To deal with this, BDS hired EHS-Alaska, a hazmat investigation firm based in Eagle River.
As hazmat experts, EHS-Alaska looked for multiple things which experience has shown are likely to be present: mercury in poured gymnasium floors and light bulbs, lead in paints and coatings, polychlorinated biphenyls (PCBs) in light ballasts, and radioactive elements in exit signs. By far the most pervasive material is asbestos, which can show up in sheet vinyl, wall finishes, insulation, mastics, sealants and window gaskets to name just a few of the possible sources. Any of these items that contain asbestos are considered to be hazardous materials.
EHS-Alaska began by studying available background material and blueprints of the buildings, looking to find possible sources. Source list in hand, investigators performed a physical inspection, sampling materials in the existing school and the buildings slated for relocation or demolition. The school building is fairly clean, having been built in the 1980s after use of lead and asbestos was reduced. Not so the old teacher housing, which is found to be full of asbestos.
Asbestos is a naturally occurring mineral, and it isn’t a health hazard until it becomes airborne as dust, when the fibers can find their way into the human body with lethal consequences. Construction activity by its nature creates a lot of dust: all asbestos-containing materials that may be disturbed must be removed by specially trained workers. Since Kipnuk does not have a landfill that is permitted to receive asbestos, it all gets removed from the village, and, like the contaminated soil, taken to a specialized disposal site.
Fire in the Hole
And what of the unexpected methane gas? Without a specialized investigation, the design team couldn’t identify a source with certainty. It might be a result of leakage from the sewage lagoon; it might be coming from an old buried landfill; it might be the result of melting permafrost and subsequent decay of organic material. In a perfect world, the gas could be harvested and used as an on-site energy source. However, developing such a source without an investigation of its magnitude and locality is years and years away, and would need far more infrastructure than currently exists in Kipnuk. For now, the methane remains an unmitigated anomaly, a nuisance to be wary of, but not a big enough problem to prevent construction. The contractor has been alerted, and now has another good reason to ban smoking on the jobsite. R
Nichelle Seely is an architect for Bezek Durst Seiser Architects and Planners in Anchorage.
Methane flame ignited by an equipment spark in the geotech core sample hole at Kipnuk school site.
Photo courtesy of Nichelle Seely
Posted: August 1, 2012