STUDY OF ASSESSMENT AND REMEDIATION TECHNOLOGIES FOR DRYCLEANER SITES
State Coalition for Remediation of Drycleaners
Bob Jurgens, Kansas Department of
Health & Environment
With Support from
In 1998, the State Coalition for Remediation of Drycleaners (Coalition) was formed with the aid of the United States Environmental Protection Agency's (EPA) Technology Innovation Office to facilitate states sharing program and technical information from their individual programs. The Coalition members currently include nine states that have specific drycleaner remediation programs: Florida, Illinois, Kansas, Minnesota, North Carolina, Oregon, South Carolina, Tennessee, and Wisconsin. Associate member, states that are likely to have programs in the near future, are Louisiana, Missouri, and New Mexico. In addition, a number of other states, including California, New Jersey, New York, and Vermont have expressed interest in participating in Coalition activities.
A Project Management/Technical Issues Subgroup was formed to research the state programs and innovative technologies used to assess and remediate drycleaning solvent-contaminated sites. This report documents the results from this research.
Objective. The objective of this project is to provide program and project-specific information concerning contaminants, general costs, innovative technologies, cleanup standards, and guidance documents. One page summaries will be created to describe and discuss the advantages and disadvantages of the technologies. The summaries will be posted on the Coalition's web page as they are finalized. The information is to be made available to the regulatory community to aid their review of proposals, work plans, reports, and fund reimbursement requests. The private consulting industry should also find the information useful to learn about the results of technologies that are operational or have been tested at various sites throughout the United States.
The first phase of the project involved sending basic questionnaires to all the states in the United States of America. The focus of this project was to identify innovative technologies, as well as the more traditional technologies commonly used across the United States. Specific areas of interest were: history of the programs dealing with drycleaner sites, level of experience dealing with assessment reports and technologies, level of experience dealing with remediation reports and technologies, and type of guidance documents and standards used to determine cleanup criteria.
The second phase involved contacting the responding states and eliciting additional information concerning specific technologies utilized in the assessment and remediation phases of a soil and/or ground-water cleanup at drycleaning facilities. These second questionnaires were then reviewed and sites using common innovative technologies were compared with regards to implementation, contaminant reduction effectiveness, cost efficiency, and reliability.
RESULTS & DISCUSSION
The questionnaires were reviewed to help determine the experience level the state agencies have with respect to soil and/or ground-water assessments and cleanup.
State Response. Twenty-eight (28) states responded to the initial questionnaire that was sent out in the Summer of 1999. Nine of the responding states (33%) had programs dealing solely with the drycleaning industry. Three of the states without drycleaner programs (16%) were actively considering development of a drycleaner assessment/remediation program. States without drycleaner programs typically handled drycleaning-related contamination through their state superfund, voluntary cleanup, or hazardous waste programs.
This portion of the questionnaire enabled the subgroup to determine what type of programs were responding to the technical portion of the questionnaire. Programs dedicated solely to drycleaner sites will often approach site cleanups differently based on the type of contracts set up for consultant contracting, as well as the experience that comes with working a large number of sites directly related to the drycleaning industry. States with state-led trust funds often are limited significantly by the dollars available annually through the trust fund receipts. Therefore, the importance placed on cost may be different than a site requiring the responsible party (RP) to complete the work with their own funds. The level of review for work plans and reports may also be different if large numbers of consultants are completing work compared to a small number of contractors that may have been awarded state-run contracts.
The level of assessment and cleanup is directly related to the cleanup standards adopted by the individual states. Many states have adopted risk-based levels for soil and ground water. Alternative evaluation methods considered included: presence of receptors, risk pathways, beneficial use of water, future land use, and locality of the facility. Ground-water cleanup guidelines varied from the maximum contaminant levels established by the United States Environmental Protection Agency to state calculated or approved risk-based standards.
Assessment. All but one of the responding states (96%) have conducted or reviewed assessment work conducted at contaminated drycleaner sites. The scope of involvement that a state agency is involved in the assessment process ranged from conducting assessments to review of applications for reimbursement of assessment activities. Assessment technologies that are used include: soil gas surveys, soil sampling, ground-water sampling, geophysical interpretation, analysis of samples, dense non-aqueous phase liquid (DNAPL) detection, fracture trace analysis, and use of video cameras for in situ sewer lines and borehole interpretation.
Media, such as soil gas, soil, and water, are collected during typical assessment activities. Soil gas surveys are conducted with active or passive sample collection methods. Active methods collect soil gas samples immediately during the sampling event, whereas, passive soil gas methods use collection modules which allow gas infiltration into the module to collect a sample over a longer period of time (1-2 weeks). Soil and ground-water sampling is probably the most common method of media sampling to be used for site assessments. Monitoring wells(MW)/borings, direct-push technology (e.g. Geoprobe®), and micro wells.(small diameter wells (e.g. 3/4" diameter) are the most common methods used to collect soil and/or ground-water samples. Many sites incorporated one or more of these technologies (see figure below).
Interpretation of the subsurface is key to completion of site assessments. Many geophysical techniques are available for this interpretation of subsurface conditions. Ground penetrating radar (GPR) helps locate underground objects or NAPL. Soil conductivity surveys (SCS) help provide a continuous reading of the subsurface lithology. Magnetometers are able to detect buried metallic objects. Electrical resistivity surveys (ERS) help to delineate the stratigraphy and locate buried objects. Induced laser fluoroscopy (ILF) can be used to determine contaminant mass distribution and the presence of NAPL. The following figure identifies the percentage of responding states that have used the above mentioned geophysical techniques.
After soil, ground-water, and/or soil gas samples are collected, the samples must be analyzed to provide a relative or actual concentrations of the contaminants in the sampled media. Fixed location laboratories were the most common and reliable method used for sample analysis. Mobile on-site laboratories are commonly used because they are set up at the site and results are relayed to the field managers in a relatively short period of time. This allows for a change of scope of work in the field resulting in more rapid site assessments. Portable gas chromatographs(GC) are also very mobile. Some of the respondents may have considered the mobile laboratory and portable GC as the same type of analytical unit. Immunoassay kits are quick field kits that can give relative concentrations as a screening tool. Colorimetric tubes are another quick, cheap method for screening vapor for contaminants. Typically all the field methods require submission of samples to a laboratory for quality assurance/quality control. The figure below identifies the percentage of responding states that use the these analytical methods.
Depending on the severity of contamination at a drycleaner site, DNAPL may be present if tetrachloroethylene (PCE) was used by the facility for the cleaning process. DNAPL can be difficult to detect and clearly identify. Ultraviolet fluorescence uses a flourescent light to help identify DNAPLs when screening field samples. Hydrophobic dye is another quick detection method. A partitioning interwell tracer test (PITT), while expensive, is an accurate test for determining the presence and distribution of DNAPL in the subsurface. This figure identifies the percentage of responding states that use the DNAPL detection methods.
Several other technologies that were identified during the study that could be used during the assessment process. Fracture trace analysis is an inexpensive method of identifying fracture zones with aerial photographs and a knowledge of area geology. Sonic drilling is an expensive method of drilling that can penetrate consolidated and unconsolidated formations. Video cameras are being used to inspect the inside of sewer lines to help identify possible joints, cracks, or holes in the lines that may have allowed the release of solvent-contaminated waste water. Cameras are also used in boreholes to identify fractures and dissolution zones.
Remediation. All but three of the responding states (89%) have conducted or reviewed remediation work conducted at contaminated drycleaner sites. As with the assessment work, the scope of involvement of a state agency in the remediation process ranged from designing remediation systems to review of applications for reimbursement of remediation system installations.
Remediation technologies that are used were split into five basic groups: soil, ground water- general, ground water - in situ bioremediation and chemical oxidation, ground water in situ flushing, and ground water - in situ thermal treatment.
Soil remediation technologies used to date by the responding states was limited to fairly common technologies, such as excavation and removal, soil vapor extraction (SVE), and bioventing. Excavation is the digging and removal of contaminated soil followed by off-site disposal or treatment. SVE involves placing a negative pressure on wells in the vadose zone to pull contaminated soil vapors from the subsurface soils. Bioventing involves the enhancement of biological activity to degrade solvents in the vadose zone using passive venting techniques. The following figure identifies the percentage of responding states that use the soil remediation methods.
General ground-water remediation can be conducted using a variety of innovative technologies. Many of the newer technologies have not been implemented on a full scale, therefore, bench scale and pilot studies are included in this project. Natural attenuation of the contaminants is being attempted in a large number of the responding sites. Permeable reaction walls use reactive materials to degrade the solvents as they pass through the reactive media. Multi-phase extraction typically involves removal of vapor and water in the same system, attempting to enhance the removal of both media with one system. Air sparging injects air or other gases into the aquifer attempting to volatilize the contaminants or enhance bioremediation in the ground water. Recirculating wells attempt to remove contaminants through a volatilization process or chemical reaction. The process is enhanced by theoretically passing a particle of water through the same process by recirculating the water via pumping with mechanical pumps or an air lift process. The next figure identifies the percentage of responding states that use these remediation methods.
Bioremediation ground-water treatment systems enhance the existing in situ natural biological organisms by providing a food source or other key ingredients necessary for the organisms to thrive. Two common technologies are Hydrogen Release Compound (HRC) for chlorinated compounds and Oxygen Release Compounds (ORC) for halogenated compounds. Chemical oxidation is the process of reacting the contaminants with chemicals that are injected into the saturated zone. The chemicals are supplied to provide an in situ reaction and subsequent destruction/degradation of the contaminants. Chemicals falling in this category are potassium and sodium permanganate, hydrogen peroxide, sodium lactate, and ozone.
The chart below identifies the percentage of responding states that use these bioremediation and chemical oxidation remediation methods.
Ground water - In situ flushing is the process of promoting movement of contaminants by displacing the contamination using a co-solvent or surfactant. Thermal treatment provides heat to the impacted zones to help volatilize the contaminant enabling removal or in situ destruction. Steam injection and electrical heating are two methods used by the responding states. Figure 8 identifies the percentage of responding states that use these flushing and thermal remediation methods.
The initial survey provided excellent data concerning the types of technologies being used across the United States of America (see Appendix). The questionnaire responses were compiled and additional information is being gathered from the states in an effort to provide comprehensive information concerning general capital and operational costs, as well as help determine the effectiveness of the various technologies. One page summaries are being created to describe and discuss the advantages and disadvantages of the technologies. The summaries will be posted on the Project's web page as they are finalized. The web page is accessible from EPA's Cleanup Information (Clu-In) Internet site and can be found at http://www.clu-in.org/programs/dryclean/.
Special thanks to the states that provide information for this project. These states include:
Alaska, Arizona, Arkansas, Colorado, Delaware, Florida, Georgia, Illinois, Kansas, Louisiana,
Maryland, Minnesota, Missouri, Nebraska, Nevada, New Jersey, New York, North Carolina, North Dakota, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Vermont, Virginia, Wisconsin, and Wyoming. Additional thanks to the Technology Innovation Office (TIO) for their support of the Coalition.
Assessment Technologies Utilized at Drycleaner Sites
Soil Gas Surveys
Active Soil Gas Surveys
Applications: Useful tool for delineating contaminant source areas in the unsaturated zone and to a very limited extent in shallow ground water. Particularly useful if drycleaning facility has been razed and the former facility layout is unknown. Utilized with a mobile laboratory or portable gas-chromatographs (GC), an active soil gas survey provides real-time data that allows delineation of contaminant source areas in one mobilization. Shipping soil gas samples to fixed laboratory increases costs and delays receipt of data.
Disadvantages/limitations: Not applicable in areas with very shallow water tables (probe will log up with water) or in low permeability soils.
Passive Soil Gas Surveys
Applications: Similar to active soil gas surveys. Applicable to low permeability soils. Because it is collected over a longer time period, the data may be more representative than active soil gas survey data.
Disadvantages/Limitations: Does not provide real-time data. Requires two mobilizations (one to install and one to remove device) and a waiting period to receive analytical data from a fixed laboratory.
Direct-Push Vertical Profiling
Applications: Excellent screening tool for determining contaminant mass distribution and choosing monitor well locations. Minimizes number of monitor wells installed and insures that wells are screened over zones of concern. When utilized with a mobile laboratory or a portable GC, provides real time data that allows for adjustment of scope of work in the field - minimizing the former iterative nature of contamination assessments - saving time and money. Soil gas, soil and ground-water samples and geophysical data can be collected with this tool. Decreasing the interval between sampling points can provide a detailed picture of contaminant distribution in source areas - the type of data especially necessary for in situ remedial applications.
A wide variety of equipment is available including smaller rigs that can be utilized inside drycleaning facilities to sample beneath floor slabs in solvent use/storage areas.
Disadvantages/Limitations: Limited to unconsolidated or poorly indurated sediments and usually to depths of less than 100 feet.
Applications: Provide a quick, easily installed ground-water monitoring point. Material costs are low and well installation and sampling generates a minimum amount of wastes - no cuttings, minimum amount of development and purge water. Microwells can be especially useful in monitoring remedial systems.
Disadvantages/Limitations: Depth of installation limited by direct push refusal. Some regulatory agencies may not approve of usage. There are concerns by some that a sufficient seal cannot be obtained in the limited annular space. There are also concerns about microwell durability for long-term ground-water monitoring.
Applications: Provides a new method for ground-water monitoring. Eliminates the need for well purging, reducing investigation-derived wastes and sampling time.
Disadvantages/Limitations: Time - sampler must be left in monitor well at least 2 weeks to achieve chemical equilibrium. Then the sample must be sent to laboratory for analysis.
Ground Penetrating Radar
Applications: Can be used to locate septic tanks, underground storage tanks (USTs), buried utility lines and to delineate non-aqueous phase liquid (NAPL) in certain situations. When integrated with lithological data can be used to better define site stratigraphy.
Disadvantages/Limitations: Limited depth of investigation - generally < 30 ft. bls. Radio wave signal is attenuated by materials with higher electrical conductivity - sat-rated clays and pore spaces saturated with brackish, saline or high total-dissolved-solids (TDS) ground water.
Soil Conductivity Survey
Applications: Can be used with direct push technology and lithology borings to delineate site stratigraphy. This will facilitate collection of ground-water samples at optimum locations and provide data that are critical for the design and installation of remedial systems.
Disadvantages/Limitations: May not be widely available.
Applications: Can be used to locate metallic objects in the subsurface - such as USTs, pipelines, utility lines, buried drums, etc. Cheap and widely available.
Disadvantages: Application limited to metallic objects.
Electrical Resistivity Survey
Applications: Can be used to delineate stratigraphy, locate buried objects and to a very limited extent may be used to identify NAPLs.
Disadvantages: Utilities, etc. can provide interference.
Induced Laser Fluoroscopy
Applications: Can be used to determine contaminant mass distribution and to determine the presence of NAPL. The greater application of the method is for sites with petroleum hydrocarbon contamination (so it could be utilized at sites with petroleum drycleaning solvent contamination). However, the technology has been utilized to delineate tetrachloroethylene (PCE) contamination (dense non-aqueous phase liquid, or DNAPL) at a drycleaner site that was a former service station.
Disadvantages: Limited to areas of relatively high contaminant concentrations. Technology is not widely available. The size of the equipment limit its use at certain drycleaner locations.
Membrane Interface Probe
Applications: Utilizes photoionization/flame ionization detectors (PID/FID) to detect organic compounds in soil/ground water. Can be utilized with direct push technology to show contaminant mass distribution.
Disadvantages/Limitations: Detection limits are in parts-per-million (ppm). This limits the tool to use in source areas in highly contaminated sites.
Borehole Geophysical Logs
Applications: Can be used to determine lithology, porosity, well casing depths, and to help delineate stratigraphy.
Disadvantages/Limitations: Expensive and not widely available. Requires certain minimal size, and in some cases open boreholes for use.
Global Positioning System/GIS
Useful in fieldwork to provide real-time locational data for wells, sampling points, potential receptors etc. thereby facilitating the production of maps and decision making.
Applications: Provides onsite analysis utilizing laboratory grade equipment, i.e., GC and gas chromatography/mass spectroscopy (GC/MS) units available. Laboratory certification is available in some states. When used in conjunction with direct push technology provides real-time data that allows for changing the scope of the assessment resulting in quicker, cheaper assessments.
Disadvantages/Limitations: Costs (though this may not be a valid concern when the big picture is considered). Not especially applicable for sites where petroleum drycleaning solvents are the constituents of concern because these solvents are mixtures largely composed of long-chain hydrocarbons that require extractions.
Advantages: Can be used as a screening tool that provides a quick verification that contamination is present.
Disadvantages/Limitations: Relatively high detection limits. Kits are compound specific.
Advantages: Can be used as a screening tool to provide a quick, relatively cheap determination of contaminants present.
Disadvantages/Limitations: Relatively high detection limits. Tubes are compound specific.
Advantages: A quick, inexpensive check for the presence of NAPL .
Disadvantages/Limitations: Not necessarily definitive, a number of substances besides NAPL are fluorescent under a black light. PCE does not fluoresce but petroleum drycleaning solvents do fluoresce.
Hydrophobic Dye (Sudan IV)
Advantages: A quick direct indicator of DNAPL.
Disadvantages: May not be definitive. The dye is a toxic material.
Partitioning Interwell Tracer Test
Advantages: A method to determine the presence and distribution (volume and saturation) of NAPL in the subsurface by injecting tracers with different partitioning coefficients, some of which are retarded by partitioning into and from the NAPL and then measuring the tracer concentrations in samples collected from a recovery well over time.
Disadvantages: Very Expensive and not especially applicable to the scale of work at drycleaner sites. Requires at least one injection and one recovery well.
Fracture Trace Analysis
Inexpensive way to identify fracture zones which act as preferential flow zones, utilizing aerial photographs and a knowledge of the area geology.
Advantages: Can penetrate both unconsolidated and indurated formations. Process generates continuous core that is invaluable in characterizing site stratigraphy. Generates a minimal amount of wastes - which is a consideration in contaminant source areas where investigation-derived wastes may be hazardous. No fluids are circulated in advancement of drill string, therefore there is no flushing or invasion of the formation nor is there any cross contamination that is associated with mud rotary drilling. Zones can be isolated with a packer to collect water samples during drilling operations.
Disadvantages: Expensive (though not necessarily so if cost savings on investigation-derived waste disposal are considered). The drill rig has a large "footprint" and may not be applicable to congested urban sites such as drycleaning facilities. Rig availability is limited.
Advantages: Can be used to provide a visual survey of the integrity of sewer lines. Breaches and leaks in sewer lines can act as point sources for discharge of drycleaning contact water that can contain free-phase solvent. Some city utility departments routinely run video cameras through sewer lines and have these video tapes on file. Borehole video cameras can be used in boreholes to identify fracture and dissolution zones.