HS Resources Inc. Landfarm: An Oil and Gas Operator's Success at Reducing Environmental Cost and Liability Using Land Treatment Techniques

Patrick E. Flynn, Director, Environmental Affairs
HS Resources, Inc.
Denver, Colorado

In March 1995, HS Resources, Inc. became one of the first oil and gas companies in Colorado to permit a non-commercial, centralized land treatment facility (landfarm) for treating and recycling nonhazardous oilfield wastes under land treatment rules established by the Colorado Oil and Gas Conservation Commission (COGCC). HSR chose the centralized landfarming option for the following reasons:

  • Landfarm utilizes proven, cost-effective, low tech methods to foster natural biodegradation of hydrocarbon compounds, the primary contaminant found in hydrocarbon-affected soil and many other exploration and production (E&P) wastes;
  • Employing a centralized approach is an efficient means for the Company to manage wastes related to spills and release from multiple centrally-located well sites;
  • Promptly removing affected soil from individual well sites (for treatment at the central site) minimizes conflict between the Company's operations and agriculture, the dominant surface use in our field area;
  • Concentrating our land treatment/recycling activities at a single, Company-controlled site rather than managing multiple remediation projects at remote well sites or disposing the waste at a commercial facility minimizes our long term environmental liability.

Background Information

HS Resources, Inc. is a publicly traded, independent oil and gas exploration, production, gathering, and transportation company that was established in 1978. The Company operates wells in Colorado, Wyoming, Oklahoma, Louisiana, and Texas, approximately 80 percent of which produce primarily natural gas and hydrocarbon condensate. HSR operates over 3,000 gas and oil wells in the DJ Basin of Weld, Adams, Arapahoe, and Elbert Counties, Colorado and is the largest producer of natural gas along Colorado's Front Range.

In 1994, HSR began a program of replacing buried concrete produced water storage tanks and closing over 100 unlined production pits at tank batteries the Company had acquired from other operators. This pit closure and tank replacement program generated significant quantities of hydrocarbon-affected soil associated with past releases of produced water and hydrocarbons from the pits/tanks. To effectively manage remediation costs and limit our long-term liability, HSR evaluated various soil treatment and disposal options, including:

  • In-situ treatment techniques such as bioventing and soil vapor extraction.
  • Excavation and onsite land treatment;
  • Excavation and offsite land treatment; and
  • Excavation and offsite treatment or disposal.

Technology-driven, capital intensive technologies such as bioventing and soil vapor extraction were not selected because of the relatively high capital, operating and maintenance costs associated with multiple sites. Excavation and onsite land treatment is comparatively inexpensive, but requires large work areas at each site and can interfere with surface use for extended periods of time. Offsite treatment/disposal options for hydrocarbon-affected wastes were limited, relatively costly, and transferred the Company's long term liabilities from the well site to the disposal site.

HSR determined that the most cost-effective technique for addressing our soil contamination at multiple remote well sites was excavation and offsite land treatment at a centralized facility.

Site Selection and Permitting

HSR surveyed numerous potential sites for the landfarm before selecting the location we purchased approximately five miles east of Platteville in Weld County. The site was selected based on operational, land use, and environmental considerations, including:

  • The site is centrally located to the core of HSR's producing oil and gas field;
  • The property and surrounding areas are used primarily for grazing and rangeland and no irrigated or cultivated agriculture was effected;
  • The facility would be located just off a paved, county-maintained road;
  • There are no sensitive environmental receptors present such as a shallow water table, surface water, wildlife habitat, or wetlands.

Permitting

HSR permitted its landfarm under then newly adopted rules for landfarm operations established by COGCC. The Company also obtained a land use permit from Weld County. This latter permit, known as the Use by Special Review (USR) process, was essentially a zoning variance that was required since the land was zoned for agriculture and landfarming was considered an industrial use. The County USR process involved three public hearings and gave neighboring landowners an opportunity to express any concerns about the project, which the company addressed through various concessions and agreements.

Limitations on Waste Accepted

HSR's landfarm is a noncommercial facility and only Company-owned nonhazardous E&P wastes are accepted. These include hydrocarbon-affected soil, frac sand, drilling mud, and tank bottoms. COGCC rules require the wastes not exceed prescribed maximum contaminant levels for hydrocarbons, metals, and total dissolved solids. The most significant limitation is for total petroleum hydrocarbons (TPH), which cannot exceed 50,000 parts per million (ppm).

Land Treatment Process

HSR's landfarming operation relies on enhancing natural bacteria to biodegrade hydrocarbons in the wastes being treated. Such bioaugmentation involves promoting growth of naturally occurring bacteria in the affected soil through addition of oxygen and moisture. The hydrocarbons provide the nutrients, although in some cases other nutrients are added to promote microbial activity. An outline of the land treatment process employed includes:

  • Hydrocarbon-affected soil is excavated from remote well sites, pipelines, or other facilities and transported to the landfarm;
  • The soil, frac sand, or other waste is thin spread on the ground to a thickness of one foot or less;
  • The thin spread material is disked approximately monthly to add oxygen;
  • Water is applied to the thin spread material to maintain the moisture content at approximately 10 to 15 percent;
  • Nutrients in the form of commercial fertilizer (potassium, nitrogen, phosphorous, and trace minerals) may be added to promote more rapid bacterial activity and increase biodegradation rates. When nutrients are added, they are typically applied at a rate of about one pound of fertilizer per cubic yard of waste;
  • Field measurement of volatile organic compounds in the waste is made periodically with a hand held photoionization detector (PID). When PID measurements reach approximately 1,000 ppm, representative confirmation lab samples are submitted for TPH analysis. Land treatment is considered complete when TPH levels are reduced to less than 1,000 ppm; and
  • The treated material is stockpiled onsite for eventual recycling as backfill at other spill sites and for use as construction material at HSR locations.

Note that the Company utilizes naturally-occurring bacteria for its land treatment operations. In addition to being the most cost-effective approach, we have reviewed numerous studies suggesting an estimated 90 percent of naturally-occurring bacteria are hydrocarbon degraders and are typically more effective at biodegrading hydrocarbons in a given environment than imported microbes.

Environmental Monitoring

A key provision of both our COGCC and Weld County landfarm permits is soil and ground water monitoring requirements. HSR has installed eight ground water monitoring wells at the facility, located along the downgradient boundary, upgradient of the land treatment cells, and within the active land treatment area. Water levels in the wells are measured quarterly and ground water samples are collected for analysis of benzene, toluene, ethylbenzene, and xylenes (BTEX) and TPH compounds.

Shallow soil beneath the land treatment areas is sampled semi-annually for BTEX and TPH. Results of the soil and ground water analysis are summarized in quarterly monitoring reports made to COGCC and Weld County.

Finally, the Company also agreed to sample an adjoining landowner's water supply well annually to ensure that there are no impacts related to landfarming. To date, there has been no indication of adverse soil or ground water impacts related to the Company's landfarm operation. If evidence of an impact was detected, landfarming would be suspended while the Company worked with state and county agencies to assess the impacts and prepare a remediation plan.

Record Keeping

In addition to the quarterly monitoring reports mentioned above, HSR maintains records of the volume, type, and source of all waste treated at the landfarm, as well as the final disposition of recycled material. We also document all performance monitoring data and the date of tilling, water, and nutrient amendments.

Costs Benefits

HSR estimates the average cost to land treat its hydrocarbon-bearing wastes at our centralized facility is approximately $4.00 to $5.00 per cubic yard. This includes costs related to transportation, thin spreading, amendments, performance monitoring, and environmental monitoring. It excludes the initial capital costs associated with acquisition and improvements to the property. The permitting costs were minimal. When the treated material is recycled as backfill, our net costs are reduced to about $1.00 per cubic yard.

Since the facility began operations in March 1995, HSR has land treated over 35,000 cubic yards of hydrocarbon-affected E&P waste. The return on our capital expense investment was realized within the first eight month of operation. Since the project began, the Company has realized waste management savings ranging from $300,000 to over $750,000 compared to the cost that would have been incurred had we treated/disposed on the wastes either onsite or at a commercial landfill.

Conclusions

HSR's decision to permit and operate a centralized land treatment facility for managing our nonhazardous E&P wastes has proven to be a successful, cost effective method for managing wastes, reducing environmental liability, and improving landowner relations. The use of a centralized approach fits very well with the scope of the Company's operations along the Colorado Front Range. However, we have also considered using the same approach in other geographic areas and field locations where the Company operates fewer wells and believe it may represent the most effective waste management option in these cases as well.