Rapid growth in the Bakken Shale area spurs need for decentralized wastewater treatment solutions
The oil and gas boom in the Bakken Shale is driving an unemployment rate of less than 1 percent in Williston, N.D., and it is fueling rapid growth in the area as the country continues to reduce its dependence on foreign oil.
As good as this is for gas prices, the local economy and the country as a whole, the booming population has put an incredible strain on the otherwise quiet communities of western North Dakota. Major housing shortages and overloaded water and wastewater infrastructure in these communities have forced development in rural areas without access to regional infrastructure.
According to a study completed by North Dakota State University, the workforce population in the Bakken was between 25,000 and 33,000 in 2012. This is expected to increase to 53,000 by 2020, and while the wastewater infrastructure is expanding, it is not currently adequate to meet these new demands. Most small communities either operate with lagoon systems or otherwise overwhelmed wastewater treatment systems that discharge into the Missouri River. In addition, the oil and gas companies prefer their employees to be located close to the production facilities, which are not often close to towns or regional infrastructure. All of these factors have contributed to the rapidly growing number of onsite wastewater treatment systems serving commercial/industrial facilities, large worker housing facilities, single-family homes and RV developments.
Housing needs create wastewater management challenges
New housing facilities are needed in the Bakken to support the workers and their families who are moving here from all over the country. Unless they are within city or town boundaries, a developer’s only options for wastewater servicing are limited to holding tanks or onsite treatment and disposal. The pumping and hauling of holding tank effluent is generally not considered a long-term solution due to rising pumping costs and a sometimes unreasonable distance to state-approved receiving facilities. In addition, the North Dakota Department of Health (the primary regulator of onsite systems) is not currently allowing pumping and hauling at most new developments. As a result, onsite treatment and disposal is the only viable option for most new developments outside the boundaries of regional infrastructure.
The North Dakota Department of Health has established guidance documents that require secondary treatment for all developments with populations of more than 100 residents. These documents also provide guidance for wastewater disposal, construction supervision, and monitoring of all new onsite systems. To meet the area’s needs, there are a number of secondary treatment technologies that have flooded the market in North Dakota, but the continued challenge is what to do with the water following treatment.
Currently, the options are limited to stream discharge, soil discharge, or reuse in the hydraulic fracturing of new wells. A stream discharge is allowed only if the project is adjacent or has an easement to a “blue-line” stream. In that case, discharge is only allowed in non-frozen conditions, so a 180-day storage pond is required for every project.
Reuse is also an option, and many projects are treating wastewater and then giving or selling it to frac water companies. This can be an option, but the frac water companies generally require delivery of more than one million gallons at a time and specify a certain water quality, which cannot always be met. North Dakota requires an agreement to be in place with the frac water company at the time of approval, and a backup option should they not be able to get rid of the water.
Soil disposal systems meet needs
The alternative to stream discharge and reuse, and the most common disposal method, is large soil disposal systems. These systems require engineering design, detailed soil classification, and large areas of land. Although not as difficult as finding a suitable stream discharge, finding suitable soil for disposal can be a challenge in Western North Dakota. The terrain is rolling and soils can be quite variable due to the area’s glacial history. During the last glaciation, the glaciers did not advance past the Little Missouri River due to the area’s elevation and bedrock topography. Instead, the glaciers overlapped onto the area and left ice contact deposits.
The area north of the Little Missouri is generally characterized by fine textured, but consistent silt loam and clay loam soils in line with stagnating glacial deposits. South of the Little Missouri, soil textures ranging from sand to clay loam can be encountered in a single quarter section. Due to this factor, the soils investigation should be the first step in any project in the region that is designed to use soil disposal. Following the field work, lot and building locations can be designed around the disposal area, which should be located in the most permeable soils of the site to reduce size and cost.
There are a number of benefits to large wastewater soil disposal systems. For example, in developments that rely on wells for potable water, the water is used and wastewater is produced, treated and returned to the aquifer close to the point of origin. This completes the hydrologic cycle within the local region and prevents slowly recharging groundwater from being lost into rivers and streams. In addition, the soil can provide further wastewater treatment, reducing treatment system cost and improving overall water quality.
From an aesthetic perspective, very little equipment is installed above ground in the soil disposal system. Following construction, the drainfield area is seeded with native prairie grass and wildflowers that will eventually look like natural grassland. Split-rail fences are generally required to prevent encroachment by snowmobiles and other vehicles, but this can be built into the design of the development and be an amenity to homeowners desiring large tracts of open space.
In these soil disposal systems, the drainfield is constructed using chambered or graveled infiltration trenches installed at a spacing of 9 or 12 feet on edge, depending on the level of treatment required. In addition, area regulations specify that the drainfield must be pressure dosed to ensure equal distribution. An area equal to 100 percent of the primary drainfield must also be provided as a backup or reserve drainfield system. This results in a very large footprint that can be limiting to projects if space is not designated and reserved at the outset of the development design.
Lukenbill Estates Development
As an example, the Lukenbill Estates Development located northwest of Williston may eventually support up to 300 park model homes ranging in size from two to three bedrooms. Lukenbill will be one of the largest subdivisions in the Bakken region serviced by a community wastewater treatment and disposal system, if not the largest. As of spring 2013, 80 of the 300 homes and approximately one-third of the treatment and disposal system has been constructed.
Onsite wastewater treatment starts with collection. The Lukenbill treatment system utilizes an Orenco Septic Tank Effluent Pumping System (STEP) designed by KLJ Engineering that includes septic tanks located on each lot for primary treatment and solids settling. Pumps and filters are incorporated within each tank and liquid wastewater is pumped to 4-inch mainlines in the road and eventually to the treatment site. Secondary treatment is provided via Orenco’s AX-MAX technology.
Following treatment, effluent flows to a number of dosing tanks, where the treated water is pressure dosed with 3 hp pumps to infiltration trenches designed by SD Consulting Group utilizing Infiltrator Quick4 Standard chambers. The first phase, consisting of 100 lots, was constructed in 2012 and is approximately nine acres including the primary and reserve treatment and disposal areas. Soil conditions, analyzed via more than 20 test pits, generally consist of silt loam with an EPA-suggested loading rate of 0.8 gallons per day per square foot for secondary treated effluent. The drainfield is located adjacent to an existing oil well in an area otherwise undevelopable due to setback restrictions. Phase 2 of the project will be constructed north and east of the oil well and will consist of an additional 15 acres of primary and reserve drainfield area with a total of 2,532 chambers used in the Phase I and Phase 2 drainfield system. The maximum design flow of the facility could reach up to 90,000 gallons per day at full build-out.
The challenges in the Bakken region are similar to other oil producing areas. Other oil plays, such as the Marcellus Shale in Pennsylvania, the Eagle Ford Shale in Texas, and the Green River Shale in Colorado, are all located in generally remote locations with limited access to regional infrastructure. If these areas continue to grow as expected, they will need to look at onsite solutions such as large soil disposal fields to solve their wastewater problems. In addition, pipeline companies often need temporary housing for their workers as the pipelines build out. Some secondary treatment systems, like the AX-MAX, are modular and easy to move as the camps and pipelines progress.
Development in the Bakken is not expected to slow down any time soon. Even if communities continually upgrade their regional treatment facilities, there will still be a need for onsite wastewater treatment and soil disposal in rural areas near worker housing facilities and well sites. If the land area is available, large soil disposal systems may be the preferred approach by most developers due to the ease of operation, successful track record, and relatively easy approval pathway. These reasons, combined with the environmental benefits, will ensure the technology will remain a good option throughout the oil boom.