A pilot scale feasibility study was initiated to evaluate the feasibility of landfarming diesel mud residues in southeastern Oklahoma. Results indicated that land application of diesel residues is an environmentally acceptable disposal method. In a plot with an initial oil and grease (O and G) loading rate of 7.6%, the O and G content decreased by 89.5% during the 209-day study interval. Addition of nutrients enhanced degradation rates and reduced O and G levels below the 1% phytotoxic threshold. An O and G loading rate of 5.8% resulted in no measurable hydrocarbon migration in the soil profile. BTEX levels in leachate samples did not exceed drinking water standards. Total metals measured in the zone of incorporation did not exceed guidelines for limiting constituents. Seed germination studies suggested that landfarming operations could be revegetated within 180 days. Introduction The Oklahoma portion of the Arkoma Basin is a very active natural gas exploration and production region. Typical exploration and production wells are drilled to total dept[is of 14,000–17,000 ft. Diesel-based drilling muds are used because of their desirable rheological properties and value in maintenance of wellbore quality. Approximately 12,000 ft of diesel-contaminated drill cuttings are produced while drilling a single well. Disposal of hydrocarbon-based drill cuttings is a major problem for E and P operators. Disposal options for hydrocarbon-based drill cuttings include burial, landfilling, incineration, solidification, mixing with fly ash and road spreading, and land farming. The preferred disposal method in south-eastern Oklahoma is to mix the cuttings with fly ash and spread on lease roads or production sites. This study was initiated to evaluate the feasibility of land farming diesel mud residues. Soil can be considered a large bioreactor which biodegrades hydrocarbons and converts them into environmentally safe forms. The objectives of this study were:To evaluate the potential of native soil bacteria to degrade the hydrocarbon component of the diesel mud residues.To determine biodegradation rates.To determine if biodegradation rates could be enhanced through addition of nutrients.To determine the effect of landfarming on levels of metals and salts in the soils.To evaluate the potential of landfarming to adversely effect groundwater.To determine when soils treated with diesel mud residues could be revegetated.To determine if hydrocarbons, salts or heavy metalsl each from fly ash/diesel cuttings mixtures. Materials and Methods Construction of Test Plots The Oklahoma Corporation Commission (OCC) approved this pilot study with the stipulation that all runoff and leachate from the test plots must be collected and properly discarded. Figure 1 illustrates a plan and cross-section view of a test plot and associated leachate collection system. P. 149^
Condensate liquids have been found to contaminate soil and groundwater at two gas production sites in the Denver Basin operated by Amoco Production Co. These sites have been closely monitored since July 1993 to determine whether intrinsic aerobic or anaerobic bioremediation of hydrocarbons occurs at a sufficient rate and to an adequate end point to support a no-intervention decision. Groundwater monitoring and analysis of soil cores suggest that intrinsic bioremediation is occurring at these sites by multiple pathways, including aerobic oxidation, Fe(III) reduction, and sulfate reduction.
A pilot scale field study was conducted at the Amoco Production Company Kalkaska Gas Processing Plant (KGPP) near Kalkaska, Michigan, to assess the efficacy of utilizing in situ air sparging to remediate subsurface BTEX contamination in the aquifer and vadose zone. In situ air sparging is an innovative soil and groundwater remediation technology where air is injected into the saturated zone below the water table to facilitate the volatilization of volatile organic compounds (VOCs).The goals of this study were to: (1) evaluate the potential for enhancing the removal of dissolved BTEX contaminants in the groundwater by sparging air into the aquifer; (2) determine if vadose zone soils at the site cont.ained an indigenous microbial population capable of degrading BTEX cont.aminants;(3) evaluate the potential for air sparging to enhance microbial numbers and microbial activity in the vadose zone; (4) determine if sparging air into the aquifer enhanced partitioning of BTEX dissolved in groundwater into the advective gas phase with subsequent transport to the vadose zone; (5) evaluate the potential for BTEX in the advective gas phase to be volatilized to the atmosphere; and (6) determine if in situ air sparging causes significant downward or lateral dispersion of BTEX in the aquifer. A significant decrease in dissolved BTEX contaminants in the groundwater was measured during the four-month study interval. Sparging air into the aquifer did enhance partitioning of BTEX dissolved in groundwater into the advective gas phase and transport to the vadose zone. Laboratory microcosm studies, utilizing soil cores from the study site, confirmed the presence of an indigenous soil microbial population in the vadose zone capable of degrading BTEX contaminants. Selective enrichment of benzene/toluene degraders was noted in the vadose zone as a result of air sparging. BTEX References and illustrations at end of paper. 547 was not volatilized to the atmosphere during the study period and no significant downward or lateral dispersion of BTEX in the aquifer was measured. Results showed that soil vapor extraction (SVE) wells and surface treatment of VOCs may not be necessary during in situ air sparging. Consequently, remediation costs could be significantly reduced.This study supports the results obtained in earlier field trials by Amoco Production Company and provides additional evidence for the viability of in situ air sparging as a low-cost remediation technology.
Accurate delineation of the extent of subsurface hydrocarbon contamination in soils and ground water is important when initiating a monitoring plan or considering remediation options at E&P sites. Traditional site-assessment techniques used to delineate subsurface hydrocarbon contaminants (e.g., soil boreholes, excavation, monitor well installation, etc.) can be expensive, time-consuming, and disruptive to local land use or production operations. Soil gas surveys can provide a rapid, cost-effective, nonobtrusive alternative to traditional site-assessment techniques. Introduction Accurate delineation of the extent of subsurface hydrocarbon contamination in soils and ground water is important when initiating a monitoring plan or installing a remediation system. Traditional site-assessment techniques utilized (soil boreholes, excavation with backhoe, monitor well installation, etc.) can be time-consuming, expensive, and/or disruptive to local land use. Soil gas surveys can provide a rapid, cost-effective, unobtrusive alternative to traditional site-assessment techniques. Soil gas surveys are based on the following principles:Most subsurface hydrocarbon contaminants have a volatile component (VOCs) which is present in soil gases; andAerobic (oxygen-consuming) bacteria associated with subsurface hydrocarbon contaminants consume oxygen and produce carbon dioxide more rapidly than bacteria present in uncontaminated, background soils. Consequently, soil gases associated with subsurface hydrocarbon contamination will typically have elevated VOCs carbon dioxide (CO2) levels and decreased oxygen (O2) levels when compared to background, uncontaminated soil. These soil gas constituents can be inexpensively and rapidly sampled and measured in the field. If the hydrocarbon contaminants have a significant volatile constituent, measurement of soil gas O2 and CO2 levels may not be necessary. However, soil gas O2 and CO2 measurements provide independent data which increase the confidence level of the soil gas survey. This paper describes how soil gas surveys can be used as a site-assessment technique and the application of this technique at two production sites. Site characteristics which make soil gas surveys either practical or impractical as a site-assessment technique are also discussed. Site Descriptions Soil gas surveys were used to delineate the extent of subsurface hydrocarbon contamination at two production sites in the Ft. Lupton, Colorado, area. The contamination at both sites was the result of the chronic leakage of gas condensate from a concrete sump over a period of years. The concrete sumps at both sites have been removed and replaced with fiberglass tanks. Contaminated soil immediately adjacent to the concrete sumps was removed to a depth of approximately 8 to 10 ft. The Brewer Pooling Unit No. 2 site is characterized by a sandy clay loam top soil which is approximately 1 to 1.5 ft thick. Beneath the top soil is a homogenous gravelly sand alluvium to a depth of at least 16 ft. Depth to ground water at the site varies from approximately 4 to 5 ft. At the Kuipers Pooling Unit No. 2 site, topsoil is a sandy loam, although a sandy gravel road fill has been spread over a significant area of the site. Beneath the topsoil/road fill sediment type varies from a gravelly sand to silt-rich sand horizons. Depth to ground water varies from approximately 2 to 4 ft in the area where the soil gas survey was performed. Soil Gas Samples At the Brewer Pooling site, soil gases were sampled and measured from a subsurface depth of 2.5 ft at 15 locations on the site. At the Kuipers Pooling site, soil gases were sampled and measured from subsurface depths of 1 to 2.5 ft at 22 locations. Soil vapors were sampled with the AMS Soil Gas Vapor Probe (SGVP; Forestry Suppliers, Jackson Mississippi). P. 749
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