Grantee Research Project Results
Final Report: Demonstration of a Subsurface Drainage System for the Remediation of Brine-Impacted Soil
EPA Grant Number: R827015C003Subproject: this is subproject number 003 , established and managed by the Center Director under grant R827015
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for the Study of Metals in the Environment
Center Director: Allen, Herbert E.
Title: Demonstration of a Subsurface Drainage System for the Remediation of Brine-Impacted Soil
Investigators: Harris, Thomas M. , Veenstra, John N.
Institution: University of Tulsa , Oklahoma State University
EPA Project Officer: Aja, Hayley
Project Period: February 1, 2000 through December 21, 2000 (Extended to April 22, 2001)
Project Amount: Refer to main center abstract for funding details.
RFA: Integrated Petroleum Environmental Consortium (IPEC) (1999) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research
Objective:
This project involved a field demonstration of technology for the remediation of soil contaminated with oilfield brine. It was conducted on the Keefer lease, which is located approximately 3 miles east of Bartlesville, OK. Currently operated by the Mueller Family Trust, this site has seen petroleum production since the 1910's. Historical aerial photographs indicate numerous brine releases occurred during waterflood operations conducted in the 1960's.
Two different technologies were evaluated in this project. The first was subsurface drainage. This technology was applied to two different areas on the Keefer lease, featuring somewhat different problems. Area I was gently sloped and had retained much of its topsoil, despite locally high brine component concentrations. This area was used to explore less expensive subsurface drainage designs. Area II was in a drainage that had experienced significant erosion, such that no topsoil remained. Subsurface drainage was used here as a means of protecting clean topsoil applied to this area from contamination by upward migrating brine components.
The second technology that was evaluated in this project relates to the disposal of the leachate produced a the subsurface drainage system. The leachate from Area II flows into a solar evaporation pond capable of concentrating the brine components for inexpensive disposal. The pond was constructed according to Oklahoma Corporation Commission specifications for the containment of oilfield brine.
Summary/Accomplishments (Outputs/Outcomes):
Phase I: Site Characterization
During initial site visits surveying was performed to help develop the design and layout of the facility. The data from this surveying was put into topographic maps of the test area. During this survey an area of hydrocarbon contaminated soil was identified within the study area. This area was avoided in the construction of the remediation system because the hydrocarbons made the soil unsuitable for a subsurface drainage system.
During Phase I the site was thoroughly characterized to ensure that the proposed subsurface drainage systems and evaporation pond were appropriately sized. Soil geotechnical property tests and soil type identification were performed on samples from the site. Intact profiles were tested for permeability in a constant head permeameter using ASTM method D-2434 (1). The permeability of the soil varied from 1.4 x l0-5 to 1 x 10-7 cm/sec with the vast majority of the samples in the 10-6 range. Known depth sections of the tube samples were used for measuring moisture content by ASTM method D-2216 (1), density by ASTM method D-2937 (1) and salt content using a saturated paste extract. The moisture content of the soil in Area I ranged from 15-18%, whereas the moisture content in Area II ranged from 19-44%. The soil pH was close to neutral and varied from 6.9 to 7.6 in Area I and 6.9 to 7.2 in Area II. A representative sieve analysis of the remaining topsoil is shown in Table 1. Based on this information this material is classified as a silty clay soil.
Table 1. Sieve analysis of a representative sample.
Sieve Number | % Passing |
200 | 46.08 |
100 | 62.36 |
50 | 71.09 |
40 | 75.66 |
30 | 80.43 |
16 | 92.42 |
8 | 98.59 |
4 | 99.68 |
The soil microbial biomass was estimated using soil samples collected with a
pre-sterilized tube sampler (2). Only material isolated, using sterile techniques,
from the inner core of the sample collected in the tube sampler was utilized
in this analysis. The average heterogeneous microbial population in the soil
around the site was 8.3 x 104 CFU/gm.
Based on the results of this preliminary survey the locations of the two subsurface drainage systems and the evaporation pond were chosen. Area II had to be located adjacent to and down-gradient from the remains of a pond that was constructed during the waterflooding operations on this lease. The area of the pond itself was excluded from the demonstration because of the significant amount of petroleum hydrocarbons just beneath the surface (see above).
Phase II: Remediation System Installation
In Phase II of the project, both subsurface drainage systems and the evaporation pond were installed.
Area I
Area I is on relatively flat terrain, and thus has not suffered gross erosion
except in a few spots. As a result, no clean topsoil was employed in this area,
and the subsurface drainage lines were buried in ditches. The area was divided
into 11 sections of approximately 1200 sq. ft. each, defined with 8 inch high
berms. The treatment to be received by each test section was assigned randomly
(by drawing the section numbers out of a hat). The design variations that were
employed in each section are indicated in Table 2 and Figure 1. Sections 1,
2 and 11 were assigned to be controls; no type of drainage was installed within
their boundaries.
In the other eight sections some form of subsurface drainage was utilized. In each test section a 12 inch wide trench was dug through the middle of the section. This trench was excavated with a backhoe; an attempt to use a trencher for this purpose was thwarted by the uneven terrain in some of the test sections. The use of a wider ditch necessitated the use of more gravel, which will increase to the cost of installing a subsurface drainage system.
Sections 3 and 4 were constructed with drainage pipe (4" diameter, corrugated, slotted polyethylene) covered with a "sock" to exclude soil particles from entering the pipe. The pipe was placed at a depth of 2.5 ft. (approximately 6" into the subsoil).
In sections 5 through 10 the trench was filled with limestone gravel, with an average particle diameter of 0.75 inches. These sections were designed to test the hypothesis that limestone can enhance the permeability of the surrounding soil. Sections 5 and 6 utilized drainage pipe (at a depth of 2.5 ft) as well as the gravel. In sections 7 through 10 no pipe was placed in the ditch; drainage in the trench was anticipated as a result of the gravel alone.
Sulfur was mixed with the gravel in sections 9 and 10. The purpose of this amendment was to test the hypothesis that the sulfur will be oxidized to sulfate ion by aerobic bacteria, and that the sulfate will convert the calcium carbonate of the gravel into a more soluble source of calcium, calcium sulfate. The calcium is then available to combat the sodicity of the contaminated soil.
Section # | Pipe | Sock | Gravel | Sulfur |
1 (control) | ||||
2 (control) | ||||
3 | X | X | ||
4 | X | X | ||
5 | X | X | ||
6 | X | X | ||
7 | X | |||
8 | X | |||
9 | X | X | ||
10 | X | X | ||
11 (control) |
Collections lines were placed in trenches at the base of each row of test sections
in Area I. These lines consisted of 4" diameter unslotted polyethylene
pipe. The trenches for these lines were dug to a depth necessary to allow the
leachate to flow from the test sections to the sump. A 250-gallon fiberglass
tank served as the sump for the system.
A sampling station was installed in each section with drainage, at the point where the drainage line or trench connected with a collection line. Constructed from PVC pipe, this device was designed to allow the leachate flowing from each section to be collected in a plastic sample bottle held onto the end of a pole.
Area II
Area II is located in a significant saltwater scar on the Keefer lease. The
entire area was first leveled with a bulldozer. Four test sections of approximately
2500 sq. ft. were then delineated in this area by berms. A breach in the dam
of the waterflooding pond adjacent and up-gradient to Area II was also repaired
at this time. At a later date a diversion ditch was dug around one side of the
pond in order that a significant volume of water might not collect behind the
dam.
The design parameters for each of the test sections in Area II are presented in Table 3. Test section II-1 was the control; it received no treatment. In the other three sections 4" slotted corrugated polyethylene drainage lines (each covered with a sock) were laid down the middle. A 2 layer of limestone gravel was applied on top of the subsoil and drainage pipe in sections II-3 and II-4. Sulfur was mixed in with the gravel in section II-4. Finally, approximately 8 inches of sandy loam topsoil were applied to all three of these sections. As in Area I, a sampling station was installed in each of the sections with drainage, at the point of connection to the single collection line, which is connected to the evaporation pond.
Section # | Pipe | Sock | Gravel | Sulfur | Topsoil |
II-1 | |||||
II-2 | X | X | X | ||
II-3 | X | X | X | X | |
II-4 | X | X | X | X | X |
Evaporation Pond
The solar evaporation pond was constructed immediately to the north of Area
II. Sizing of the pond was based on mean historical meteorological data obtained
from the National Oceanic and Atmospheric Administration (NOAA) office. Budget
constraints also influenced the final design. The evaporation pond was designed
using a procedure similar to that used for wastewater stabilization ponds (3).
The pond surface area is approximately 9000 ft2. The berms around the solar
evaporation pond were constructed to a minimum height of 3 ft. The evaporation
pond was lined with a 60 mil thick black flexible polyethylene (HDPE) geotextile
with a permeability of 10-7 cm/sec. A barbed wire fence was constructed around the
pond to exclude livestock.
Phase III: Assessing the Performance of the Remediation Systems
The performance of the subsurface drainage systems was to have been assessed from the amount of salt in the leachate collected by each system and by the decrease in the salt content of the soil in the test plots. The collection of leachate samples did not prove to be as easy as anticipated. Both systems remained dry throughout the fall (see Appendix (PDF), Figs. 6 and 7). Winter rainfall then filled up both systems. The operator of the lease had initially stated that it would be possible to pump the contents of the sump into the produced water disposal system on the lease. This was to be achieved with a level-actuated sump pump. However, it was subsequently discovered that the disposal well would have to be worked over at considerable expense. Thus, a fluid flow control system was not installed in the Area I sump. Instead, the sump has been periodically emptied with a gasoline-powered pump. Before each pumping a number of the sampling stations were flooded, such that it was not possible to know if the leachate in the station had come form the adjacent test plot or from the drainage system as a whole.
In Area II so much fluid had accumulated in the pond by he end of the fall that it was suspected to have received run-off from the surrounding area This suspicion was supported by analytical results: the conductivity of an evaporation pond sample collected on 1/21/01, was 1000 ymhos, while that of a sample of standing water collected from test section II-1 was 1950 ymhos.
Composite surface soil samples were collected on three different dates, 9/24/00 (immediately after installation of the remediation systems), 1/21/01 and 5/8/01. Details of the collection and analysis of these samples are presented in the Appendix (PDF). The results are presented in Tables 5-7 and in Figures 1-5 (see Appendix (PDF)). The Tables correspond to data sheets from the Quality Assurance Project Plan. The Figures present specific sets of data in a manner that indicates both their spatial and temporal relationships.
From the initial set of data corresponding to the samples collected on 9/24/01, it can be seen that Area I is very heterogeneous. Some of the test sections are badly contaminated, while others are nearly pristine. This may prove to complicate interpretation of the data in the future.
It can be noted in the Figures that the conductivity and brine component concentrations for the second set of samples (sampling date 1/21/01) are much lower than those for the first and third sampling dates. The explanation for this anomaly is that the relatively cool and wet weather that preceded the second sampling (October was particularly wet) caused the brine components to distribute themselves more evenly throughout the topsoil profile, while the relatively warm and dry weather preceding the first and third samplings (less than 0.42 inches/month for the first sampling, 1.81 inches/month for the third) caused the brine components to concentrate near the surface, where the samples were collected. Such behavior has been observed in other studies (e.g. 4,5). The sample moisture values that appear in Tables 5-7 are consistent with this explanation.
One might argue that, if surface samples are susceptible to the effect noted above, core samples might provide more complete and meaningful results. However, surface samples directly indicate the conditions experienced by plants as they attempt to revegetate contaminated soil. It is important to know this maximum concentration in order to predict when revegetation can be expected.
Given the effect of the weather on the samples for the first year of this study, it is premature to state if any one of the treatment options considered in Area I is more effective than the others. Sample collection and analysis will be continued for at least two more years in order that a clearer picture may emerge.
The results for Area II are also presented in the Tables and Figures. Test sections II-3 and II-4, which were equipped with a layer of gravel to aid drainage, remained relatively uncontaminated after 8 months. Also, sparse vegetation was present in these sections. During the third and final sampling it was noted that significant portions of test sections II-1 and II-2 were visibly moist despite the relatively dry weather conditions. The brine component concentrations in the moist portion of section II-2 (topsoil and drain pipe only) were comparable to those in section II-1 (control). Vegetation was absent in the moist portion of II-2 as well as II-1. These observations are consistent with the upwelling of brine contamination into the topsoil that was applied to section II-2. However, the source of the brine components may not simply be the underlying contaminated subsoil. Instead, leachate from the former waterflooding pond adjacent and up-gradient to sections II-1 and II-2 may be seeping into this area. With time we will learn if the gravel drainage layer in sections II-3 and II-4 can prevent the migration of this fluid into the clean topsoil that was applied to these sections.
The last aspect of this project that deserves comment is the use sulfur as a means of enhancing the release of calcium ion from limestone gravel. The sulfur must first be oxidized to sulfate ion by microorganisms in the soil. The sulfate concentrations in sections 1-9 and 1-10 are actually lower than those for a number of the test sections that did were not treated with sulfur. However, the soil samples are composites taken from across each test section, rather than exclusively from the vicinity of the drainage ditch.
Microbiological tests indicated that there was an overall increase in the number of heterotrophic CFUs per gram of soil (dry basis) from 8.3E+04 to 1.30E+05. It cannot be concluded, however, that this is due to the sulfur amendments. As seen in the Table 4, it can be observed from the table that the sulfur amended soil actually produced higher average heterotrophic CFU counts, but they also produced some of the lowest plate counts with respect to the non-amended sites (data included in Table 8 in Appendix (PDF)). Data were grouped to see if there was any difference between the bacterial populations derived from intact permeability core samples and from loose soil collected using sterile techniques. Amended soil had slightly higher average bacterial counts than did the non-amended core samples. The total collection of core samples had a slightly lower bacterial count than the total amended soils that could be due to the fact the bacteria benefited from the favorable conditions caused by the soil disturbance performed before adding sulfur.
Type of Sample | Lower Limit | Higher Limit | Average |
Samples (All) | 7.01E+04 | 2.27E+05 | 1.30E+05 |
Core Sample (All) | 7.01E+04 | 1.83E+05 | 1.28E+05 |
Sulfur Amended (All Samples) | 1.02E+05 | 1.98E+05 | 1.32E+05 |
Non Sulfur Amended (All Samples) | 2.80E+04 | 1.90E+05 | 1.27E+05 |
Amended Core | 1.02E+05 | 1.51E+05 | 1.27E+05 |
Amended Soil | 8.44E+04 | 2.27E+05 | 1.36E+05 |
Non Amended Cores | 7.01E+04 | 1.83E+05 | 1.30E+05 |
Non Amended Soil | 2.80E+04 | 1.90E+05 | 1.26E+05 |
CFU counts are performed on agar plates containing TGY (Tryptone, Glucose, and Yeast) agar. This agar is for culturing heterotrophic bacteria. The media does not contain sulfur except as an element in the composition of the materials in the recipe. It is likely that since background and present bacteriological work is being done with an agar that gives the advantage to heterotrophic bacteria, this procedure may not indicate an increase in the population of sulfur oxidizing bacteria. It is also possible that in increase in sulfur oxidizing bacteria will decrease the proportion of bacteria that grow well on this agar, thus implying that a decrease in heterotrophic bacteria may indicate an increase in sulfur oxidizing bacteria.
Both amended and non-amended soil samples are being preserved at -14°C for possible future work with different media favoring sulfur-oxidizing bacteria if warranted. It was a concern that the extended storage of the samples would affect the bacterial community in the soil, but there have been no outstanding signs that this is the case since growth was seen in 72 hours and the counts indicated greater populations than previous tests. In the future, some control samples may be included in the plating procedures to test this observation.
Some secondary tests for presence of sulfur oxidizing bacteria could be a change in the soil pH, although this may not afford much information due to the high buffering capacity of a brine contaminated soil.
Ultimately, a decrease in the amount of sodium, magnesium, and chloride in the soil will indicate that the process is being accomplished. Determining the mechanism, especially the contribution of sulfur oxidizing bacteria, may prove difficult.
Conclusions:
This project involved a field demonstration of subsurface drainage and solar evaporation pond technology for the remediation of soil contaminated with oilfield brine. This subsurface drainage technology was applied to two different areas of the study site. In an area that was gently sloped and had retained much of its topsoil, alternative subsurface drainage designs are being evaluated. In the other area, which has experienced significant erosion, subsurface drainage is being evaluated as a means of protecting clean topsoil applied to the area from contamination through upward migration of brine components from the contaminated material beneath. Leachate from the second area is flowing into a solar evaporation pond capable of concentrating the brine components for inexpensive disposal.
Assessment of the various design issues considered in this project has been hampered by two factors. The assessment was to involve the collection and analysis of both leachate and soil samples. However, the sampling stations installed in each section of the subsurface drainage systems have not provided samples on a regular basis (due primarily to dry weather), and have allowed for cross-contamination following significant rainfalls. Not much more success has been achieved with the soil samples. Twice when samples were collected the soil was very dry. This condition yields excessively high brine component concentrations. It is clear from the results generated to date that soil samples will need to be collected and analyzed over the course of several years to obtain a clear picture of the efficacy of the various design variables considered in this project.
Some conclusions can be drawn about the cost of these technologies. First and foremost, an appropriately lined evaporation pond will be much too expensive to use on a routine basis for the treatment of leachate from a subsurface drainage system. Thus, disposal in an existing produced water disposal system is the only viable option. Second, a trencher cannot be used on a site that is uneven or rocky. Thus, it may not be possible to reduce significantly the cost of installing a subsurface drainage system.
References:
1. American Society for Testing and Materials, Annual Book of ASTM Standards, Section 4: Construction, ASTM West Conshohocken, PA. (1997).
2. United States Environmental Protection Agency, Design Manual: Municipal Wastewater Stabilization Ponds, Office of Research and Development (EPA 626/1-83-015) (1983).
Journal Articles:
No journal articles submitted with this report: View all 4 publications for this subprojectSupplemental Keywords:
RFA, Scientific Discipline, Geographic Area, Waste, Water, TREATMENT/CONTROL, Sustainable Industry/Business, Contaminated Sediments, Remediation, Chemistry, State, Technology, Civil/Environmental Engineering, Oil Spills, Hazardous Waste, New/Innovative technologies, Engineering, Hazardous, Environmental Engineering, solar evaporation pond, green engineering, contaminated soil, oil spill, soils, IPEC, soil, treatment, brine-impacted soil, subsurface drainage system, Oklahoma (OK), innovative technologiesProgress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R827015 Center for the Study of Metals in the Environment Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R827015C001 Evaluation of Road Base Material Derived from Tank Bottom Sludges
R827015C002 Passive Sampling Devices (PSDs) for Bioavailability Screening of Soils Containing Petrochemicals
R827015C003 Demonstration of a Subsurface Drainage System for the Remediation of Brine-Impacted Soil
R827015C004 Anaerobic Intrinsic Bioremediation of Whole Gasoline
R827015C005 Microflora Involved in Phytoremediation of Polyaromatic Hydrocarbons
R827015C006 Microbial Treatment of Naturally Occurring Radioactive Material (NORM)
R827015C007 Using Plants to Remediate Petroleum-Contaminated Soil
R827015C008 The Use of Nitrate for the Control of Sulfide Formation in Oklahoma Oil Fields
R827015C009 Surfactant-Enhanced Treatment of Oil-Contaminated Soils and Oil-Based Drill Cuttings
R827015C010 Novel Materials for Facile Separation of Petroleum Products from Aqueous Mixtures Via Magnetic Filtration
R827015C011 Development of Relevant Ecological Screening Criteria (RESC) for Petroleum Hydrocarbon-Contaminated Exploration and Production Sites
R827015C012 Humate-Induced Remediation of Petroleum Contaminated Surface Soils
R827015C013 New Process for Plugging Abandoned Wells
R827015C014 Enhancement of Microbial Sulfate Reduction for the Remediation of Hydrocarbon Contaminated Aquifers - A Laboratory and Field Scale Demonstration
R827015C015 Locating Oil-Water Interfaces in Process Vessels
R827015C016 Remediation of Brine Spills with Hay
R827015C017 Continuation of an Investigation into the Anaerobic Intrinsic Bioremediation of Whole Gasoline
R827015C018 Using Plants to Remediate Petroleum-Contaminated Soil
R827015C019 Biodegradation of Petroleum Hydrocarbons in Salt-Impacted Soil by Native Halophiles or Halotolerants and Strategies for Enhanced Degradation
R827015C020 Anaerobic Intrinsic Bioremediation of MTBE
R827015C021 Evaluation of Commercial, Microbial-Based Products to Treat Paraffin Deposition in Tank Bottoms and Oil Production Equipment
R827015C022 A Continuation: Humate-Induced Remediation of Petroleum Contaminated Surface Soils
R827015C023 Data for Design of Vapor Recovery Units for Crude Oil Stock Tank Emissions
R827015C024 Development of an Environmentally Friendly and Economical Process for Plugging Abandoned Wells
R827015C025 A Continuation of Remediation of Brine Spills with Hay
R827015C026 Identifying the Signature of the Natural Attenuation of MTBE in Goundwater Using Molecular Methods and "Bug Traps"
R827015C027 Identifying the Signature of Natural Attenuation in the Microbial
Ecology of Hydrocarbon Contaminated Groundwater Using Molecular Methods and
"Bug Traps"
R827015C028 Using Plants to Remediate Petroleum-Contaminated Soil: Project Continuation
R827015C030 Effective Stormwater and Sediment Control During Pipeline Construction Using a New Filter Fence Concept
R827015C031 Evaluation of Sub-micellar Synthetic Surfactants versus Biosurfactants for Enhanced LNAPL Recovery
R827015C032 Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
R830633 Integrated Petroleum Environmental Consortium (IPEC)
R830633C001 Development of an Environmentally Friendly and Economical Process for Plugging Abandoned Wells (Phase II)
R830633C002 A Continuation of Remediation of Brine Spills with Hay
R830633C003 Effective Stormwater and Sediment Control During Pipeline Construction Using a New Filter Fence Concept
R830633C004 Evaluation of Sub-micellar Synthetic Surfactants versus Biosurfactants for Enhanced LNAPL Recovery
R830633C005 Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
R830633C006 Evaluation of Commercial, Microbial-Based Products to Treat Paraffin Deposition in Tank Bottoms and Oil Production Equipment
R830633C007 Identifying the Signature of the Natural Attenuation in the Microbial Ecology of Hydrocarbon Contaminated Groundwater Using Molecular Methods and “Bug Traps”
R830633C008 Using Plants to Remediate Petroleum-Contaminated Soil: Project Continuation
R830633C009 Use of Earthworms to Accelerate the Restoration of Oil and Brine Impacted Sites
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
Main Center: R827015
120 publications for this center
16 journal articles for this center