Perimeter Air Monitoring for Soil Remediation

Transcription

1 REMEDIATION Autumn 2007 Perimeter Air Monitoring for Soil Remediation Guy J. Graening Most environmental project managers are well versed in characterizing and remediating contaminants in soil and water media. When soil remediation activities are conducted at an environmental site, however, some project managers are faced with monitoring contaminants in the air medium for the first time. Remediation activities can disturb contaminants that are normally immobile in soil and transfer them to air. The resulting increase in airborne concentrations of contaminants, even if temporary, may be a health concern for individuals in neighboring residences or businesses. Perimeter air monitoring may be required by a regulatory agency to determine if unhealthy conditions are created and if work practices should be limited or modified. This article serves as a resource for project managers involved in perimeter air monitoring for soil remediation and provides a general summary of candidate sites, remediation activities that release contaminants, regulatory requirements, equipment and target contaminants, monitoring locations and schedule, analytical methods, and data interpretation. Oc 2007 Wiley Periodicals, Inc. INTRODUCTION When activities are conducted to remediate contaminated soil at an environmental site, in most cases, a project manager s primary focus is on attaining soil cleanup levels and a status of No Further Action from a regulatory agency. However, remediation activities can disturb contaminants that are normally immobile in soil and transfer them to air. The resulting increase in airborne concentrations of contaminants, even if temporary, may be a health concern for individuals in neighboring residences or businesses. Thus, a project manager should consider the need to conduct perimeter air monitoring during remediation activities to determine if unhealthy conditions are created and if work practices should be limited or modified. The following sections provide a general summary of candidate sites, remediation activities that release contaminants, regulatory requirements, equipment and target contaminants, monitoring locations and schedule, analytical methods, and data interpretation. CANDIDATE SITES Environmental sites with significant soil contamination that are currently undergoing active remediation are the primary candidates for perimeter air monitoring. These sites include petroleum refining and bulk facilities, mines, corporation and maintenance yards, c 2007 Wiley Periodicals, Inc. Published online in Wiley Interscience ( DOI: /rem

2 Perimeter Air Monitoring for Soil Remediation painting and plating shops, wood treating facilities, and manufacturing and chemical processing plants. Less obvious candidates for perimeter air monitoring include large demolition projects that may release significant airborne contaminants such as metals, asbestos, lead-based paint, or other building materials of concern. REMEDIATION ACTIVITIES THAT RELEASE CONTAMINANTS Perimeter air monitoring during remediation activities may be required by a local regulatory agency such as an air-quality management district or a city/county building department. Contaminants can become airborne when surface or subsurface soil remediation activities are conducted at these candidate sites. Surface activities can increase ambient dust levels and cause aqueous or solid contaminants that are adsorbed to particles in shallow soil to become airborne. These activities include grubbing, grading, stockpiling, loading for off-site disposal, consolidating contaminated soil and capping, and on-site soil treatment operations. Soil, asphalt, or concrete stockpiles and crushing operations are additional sources of airborne contaminants. Subsurface activities can expose deep soil to atmospheric conditions and cause gaseous contaminants to disperse or aqueous contaminants with high vapor pressures to volatilize. These activities include excavating, trenching, and large-diameter auguring. REGULATORY REQUIREMENTS Perimeter air monitoring during remediation activities may be required by a local regulatory agency such as an air-quality management district or a city/county building department. Specific requirements for air monitoring may be prescribed in a public ordinance, air permit, or a special-use permit for construction. The requirements are usually expressed in the form of chemical-specific concentration limits not to be exceeded at the site perimeter and may intentionally not prescribe the specific monitoring equipment and analytical methods to be used. The project manager may need to propose specific equipment, analytical methods, sample locations and schedule, and data collection and reporting in a work plan submitted to and approved by the regulatory agency prior to work commencing. Additional guidance on preparing an air monitoring work plan can be found in Superfund Program Representative Sampling Guidance: Volume 2 Air (Short-Term Monitoring) (US EPA, 1995). Even if monitoring is not required by an agency, the project manager and owner may wish to limit liability by documenting levels of airborne contaminants at the site perimeter generated during remediation. In some instances, individuals in neighboring residences or businesses express concerns or complaints regarding airborne contaminant migration to the local agency once remediation activities have begun. These complaints can subsequently trigger an official requirement for air monitoring and cause delays in remediation. EQUIPMENT AND TARGET CONTAMINANTS Before discussing air-monitoring equipment in detail, it is important to distinguish perimeter air monitoring from worker exposure monitoring. The project manager or owner may conduct air monitoring at the site perimeter to determine if airborne contaminants are reaching unhealthy levels and migrating to neighboring residences or businesses. The construction contractor may conduct simultaneous, but separate, 42 Remediation DOI: rem c 2007 Wiley Periodicals, Inc.

3 REMEDIATION Autumn 2007 Exhibit 1. Contaminant monitoring equipment specifications Contaminant Class TSP PM 10 PM 10 SVOCs VOCs Equipment Type High Volume High Volume Continuous High Volume Whole Air Air Sampler Air Sampler Air Sampler Air Sampler Sampler Manufacturer Tisch Environmental Tisch Environmental Thermo Electron Tisch Environmental Laboratory supplied Model TE-5170D TE-6070D ADR-1200S TE-1000 Accessories Optional filter Flow controller cassette holder Sample Duration 24 hrs 24 hrs 1 to 60 sec 24 hrs 8 to 24 hrs Sample Flow Rate 1.10 to 1.02 to 1 to 5 L/min to 3.5 to 1.70 m 3 /min 1.24 m 3 /min m 3 /min 11.5 ml/min Target Volume 2,000 m 3 1,600 m 3 N/A 300 m 3 6L Media 8 in. by 10 in. 8 in. by 10 in. Optional 37-mm 4 in. diam. filter, Summa Canister filter filter diam. filter sorbent cartridge Portability Low Low High Low High Electrical Power 110V/6A 110V/5A 115V/300 ma 110V/5A Requirements or 9V battery Capital Cost $2,760 $5,550 $6,995 $2,495 (Rental Rate) ($580/mo) ($1,165/mo) ($700/mo) ($525/mo) ($50/canister $40/flow ctlr.) O&M Cost $150/year $150/year $150/year Misc. Costs $860 Calibration kit $860 Calibration kit $575 Calibration kit monitoring to determine worker exposure to airborne contaminants during remediation activities per federal or state occupational laws. Perimeter air monitoring typically involves high flow rates, large sample volumes, consideration of atmospheric conditions, and equipment that is in a fixed location. In contrast, personal air monitoring is limited to low flow rates or passive sampling, small sample volumes, and equipment that can be worn while the worker conducts remediation activities throughout the site. The type of equipment used during perimeter air monitoring generally consists of specialized monitors for target contaminants and a meteorological station. Target contaminants discussed in this article consist of particulate matter, metals, semivolatile organic compounds (SVOCs), and volatile organic compounds (VOCs). Specifications of equipment for monitoring these contaminants are summarized in Exhibit 1. A meteorological station measures and records atmospheric parameters necessary to adjust and interpret the data generated from the specialized monitors. Specifications of equipment for monitoring meteorological parameters are summarized in Exhibit 2. Particulate Matter Dust generated from a construction site can be a public nuisance by reducing visibility, coating nearby buildings and vegetation, and causing acute allergic reactions in people c 2007 Wiley Periodicals, Inc. Remediation DOI: rem 43

4 Perimeter Air Monitoring for Soil Remediation Exhibit 2. Meteorological monitoring equipment specifications Pocket Weather Meter Equipment Type and Wind Sock Meteorological Station Wind Speed/Direction Sensor Manufacturer/Model Kestrel 2500 RM Young Description Impeller-type anemometer and separate wind sock Propeller-type anemometer with fuselage and tail wind vane Accuracy ±3%, ±45 ±0.2 m/s, ±3 Barometric Pressure Sensor Manufacturer/Model Kestrel 2500 Vaisala CS105 Description Monolithic silicon piezoresistive Silicon capacitive sensor sensor Accuracy ±3 millibar ±3 millibar Ambient Temperature Sensor Manufacturer/Model Kestrel 2500 RM Young Description Hermetically sealed precision Platinum RTD temperature sensor thermistor Accuracy ±1 C ±0.3 C Data Logger Campbell Scientific CR10X Accessories 3 meter tripod (for wind sock) 3 meter tripod, outdoor enclosure Capital Cost $165 $5,100 (Rental Rate) ($400/mo) O&M Cost Misc Cost $20 case, $19 replacement impeller near the site. Particulate matter generated from an environmental remediation site poses an additional health concern because aqueous or solid contaminants adsorbed to particles in soil can become airborne and migrate. People near the site may inhale or ingest the suspended particles and, thus, be directly exposed to contaminants that were relatively immobile prior to soil remediation activities. Particulate matter is measured either in its entirety as total suspended particulates (TSP) or more commonly as a specific fraction based on particle size. Local public nuisance ordinances that limit particulate matter from a construction site are typically specified as TSP, in which case the project manager would want to use equipment that measures TSP. Particulate matter with a mean aerodynamic diameter less than ten micrometers (PM 10 ) is a subset of TSP that can cause serious health effects because of its ability to pass through the throat and nose and enter the lungs (US EPA, 2007). As part of the Clean Air Act and amendments of 1990, the EPA revised the National Ambient Air Quality Standard (NAAQS) for particulate matter from TSP to PM 10. Particulate matter suspended in air at the site perimeter can be monitored with highvolume air samplers or continuous particulate samplers. The project manager must consider the data-quality objectives and available budget in deciding which equipment to select. 44 Remediation DOI: rem c 2007 Wiley Periodicals, Inc.

5 REMEDIATION Autumn 2007 High-Volume Air Samplers High-volume air samplers are the equipment referenced in the US EPA Method for measuring PM 10 (US EPA, 1998). The TE-6070D by Tisch Environmental Inc. is one brand of these samplers that have US EPA Reference Method certification. The equipment components are housed in an aluminum shelter with a special, vertically symmetric inlet that allows only PM 10 to enter. A blower motor assembly draws air through the 8-inch by 10-inch quartz fiber filter, which is preweighed by the laboratory under strict temperature and humidity conditions. A combination mass flow controller with airflow probe, digital timer, and digital elapsed time indicator provides a constant mass flow rate and programmable operation. A continuous flow/pressure recorder verifies that the 24-hour sample duration and 1,600-m 3 target volume are achieved. The sampler requires 120V, 5A electrical power to operate. Once the sample is collected, the filter is sent to the laboratory for a second weighing under strict conditions, and the difference between the final and tare weights (i.e., the gravimetric analysis) is the sample mass of PM 10.Itshould be noted that the TE-5170D TSP High Volume Air Sampler by Tisch Environmental is nearly identical to the TE-6070D PM 10 High Volume Sampler except that it does not have a special inlet and allows all suspended particles to deposit on the filter. The advantage of these air samplers is their high volumes generated over a 24-hour sample duration, which result in representative samples and low analytical detection limits. After weighing the filter for particulate matter, many subsequent analyses can be performed by taking sections from the large filter. The disadvantages of high-volume air samplers are mainly associated with their size and electrical power requirements. Although they are made of lightweight aluminum, the samplers require two people to load onto a truck and permanent electrical supply or a generator and extension cords in remote locations. Continuous Particulate Air Samplers Continuous particulate air samplers are capable of continuous operation and can provide PM 10 measurement on a near-real-time basis. The ADR-1200S by Thermo Electron is one brand of this sampler and uses a light-scattering photometry for mass measurements of particulate matter. The ADR-1200S is similar to worker exposure samplers like the PDR-1200 or DataRAM 4 by Thermo Electron but comes equipped with an external air pump for active sampling. Note that continuous, active airflow through a sampler is usually required to obtain a representative outdoor sample. Outdoor (i.e., ambient) air is not as homogenous as the air in an indoor workplace and can have variations in composition due to atmospheric conditions and site activities. The ADR can run on a rechargeable battery pack for remote operation for up to eight hours or can be powered with 120 V, 300 ma electrical power. Flexible tubing connects the sampler and air pump and the assembly can be easily mounted to a pole. The ADR can provide readings every minute, and results are typically averaged and recorded every 15 minutes. An optional filter cartridge can be installed that holds a 37-mm Teflon filter for subsequent analysis of metals or other analytes. The primary advantage of continuous particulate samplers is that an hourly profile of PM 10 can be created in addition to the 24-hour average. This profile enables a project manager to (1) determine if specific site remediation activities are causing high particulate The primary advantage of continuous particulate samplers is that an hourly profile of PM 10 can be created in addition to the 24-hour average. c 2007 Wiley Periodicals, Inc. Remediation DOI: rem 45

6 Perimeter Air Monitoring for Soil Remediation emissions and (2) immediately modify work practices if necessary. Continuous particulate samplers are less bulky in size than high-volume samplers and can be powered with only a battery pack. Metals Similar to particulate matter and metals, SVOCs suspended in air at the site perimeter are typically monitored by collecting them with a high-volume air sampler; however, SVOCs require a special sorbent train to trap compounds that would normally pass through a filter. Metals are usually present at a site as compounds rather than in their elemental form and are often adsorbed to soil particles. Metals can become airborne when remediation activities disturb soil but do not remain suspended for long periods of time since they are heavier than air. The exception is elemental mercury, which is a liquid at room temperature and can volatilize readily. Mercury can stay in the atmosphere for extended periods and travel considerable distances before depositing. Metals suspended in air can migrate and be inhaled or ingested by people living near a site. Metals suspended in air at the site perimeter are typically monitored by collecting them on a filter via a sampler equipped with a vacuum (i.e., using the suction side of a blower motor). Thus, the equipment for monitoring metals has already been discussed in the section on particulate matter. Any of the PM 10 samplers discussed can be equipped with a filter that will capture not only metals suspended in the air, but also metals adsorbed to suspended particles. Note that a significant fraction of metal-containing particles are too large to be captured by the PM 10 samplers; however, it is the smaller metal-containing particles that will reach the lower regions of the respiratory tract and are likely to cause adverse health effects. The filter is subsequently sent to a laboratory for elemental analysis of the deposited metals. The unusual properties of mercury make it hard to detect on a sample filter since it may volatilize prior to analysis. Other collection devices, such as sorbent tubes or traps, are more effective at capturing mercury for subsequent analysis. The specific metals on the filters to be analyzed should be determined from soil samples or site activities. Metals present in soil have the potential to become airborne and should provide the basis for the list of metals to be analyzed in air. If site activities such as operation of a concrete crusher are occurring, then metals released from the process should also be considered for analysis. If there is not a basis for selecting individual metals to be analyzed, then a standard list of metals can be selected. Regardless, the initial list of metals can be reduced after reviewing the analytical results from an initial sampling period. Semivolatile Organic Compounds Organic compounds that have low vapor pressures (i.e., typically less than 10 1 mm Hg) do not volatilize readily and are often adsorbed to soil particles. These SVOCs can become airborne when remediation activities disturb soil. SVOCs suspended in air can migrate and be inhaled or ingested by people near the site. Similar to particulate matter and metals, SVOCs suspended in air at the site perimeter are typically monitored by collecting them with a high-volume air sampler; however, SVOCs require a special sorbent train to trap compounds that would normally pass through a filter. The train is typically composed of a prefilter and sorbent cartridge, which is similar to a small drinking glass with a wire mesh replacing the glass bottom. One or more sorbents are then placed inside the glass and held in place by the wire mesh. The high-volume air sampler does not have a special inlet and allows TSP to be pulled through the sorbent train. 46 Remediation DOI: rem c 2007 Wiley Periodicals, Inc.

7 REMEDIATION Autumn 2007 The type of sorbent in the cartridge is tailored to the subset of SVOCs targeted such as polychlorinated biphenyls (PCBs), pesticides, and polynuclear aromatic hydrocarbons (PAHs). PCBs are a class of chlorinated hydrocarbons associated with transformer oil and other electrical products and include Aroclor-1242 and Aroclor Pesticides are a broad class of compounds that includes organophosphates such as diazinon and malathion. To trap PCBs and pesticides, the sorbent cartridge is filled with a polyurethane foam (PUF) plug. PAHs are a class of complex compounds associated with the heavier fractions of petroleum. Examples of PAHs include acenaphthene, benzo(a)pyrene, and naphthalene. To trap PAHs, the sorbent cartridge is filled with a PUF plug followed by the proprietary XAD-2 R powdered resin to trap the most volatile PAHs (e.g., naphthalene). Both cartridge arrangements are combined with a prefilter consisting of a four-inch-diameter quartz fiber filter. The entire train (prefilter and sorbent cartridge) is subsequently sent to a laboratory for analysis of the adsorbed SVOCs. Volatile Organic Compounds Organic compounds with high vapor pressures (i.e., typically above 10 1 mm Hg) can volatilize readily but, when present in soil, are adsorbed to organic carbon in soil or trapped in soil pore spaces (i.e., in soil gas). These VOCs can volatilize when remediation activities disturb soil and expose them to atmospheric pressure. At environmental sites where contamination was released years ago, VOCs are typically present only in deeper soil (i.e., greater than six inches) since surface soil is subject to diurnal barometric pressure changes, which have a purging effect. VOCs in the air at the site perimeter can be monitored by drawing them through and trapping them with a sorbent similar to the SVOC technique, but the most common method is by collecting a whole air sample. A whole air sample is obtained by collecting a small volume of ambient air in a container such that the target contaminants are captured with their host medium. The filter- and sorbent-based methods discussed so far are techniques that concentrate contaminants on a temporary medium (e.g., quartz fiber, PUF, or activated carbon) and allow the host medium (i.e., ambient air) to pass through. The whole air container recommended for highly defensible data is a Summa canister. VOC sampling using a Summa canister begins with the laboratory supplying a cleaned, evacuated canister and associated sampling equipment. The laboratory can provide canisters that have been batch-certified for cleanliness or canisters that have been individually documented to be free of contaminants (i.e., individually certified). The canisters are provided under high vacuum (i.e., near 29 inches Hg) so that air to be sampled enters automatically upon opening the valve and fills the canister within minutes. The laboratory can provide a flow controller to extend the sample duration to an eight- or ten-hour shift or even longer to a 24-hour period. The Summa canister is subsequently sent to the laboratory for analysis of VOCs in the whole air sample. In perimeter air monitoring, measurement of atmospheric conditions simultaneously with monitoring of target contaminants is crucial for accurate calculation of contaminant concentrations and data interpretation. Meteorological Parameters In perimeter air monitoring, measurement of atmospheric conditions simultaneously with monitoring of target contaminants is crucial for accurate calculation of contaminant concentrations and data interpretation. The primary meteorological parameters to monitor include ambient temperature, barometric pressure, and wind speed and direction c 2007 Wiley Periodicals, Inc. Remediation DOI: rem 47

8 Perimeter Air Monitoring for Soil Remediation The primary meteorological parameters can be measured with handheld instrumentation or a fixed meteorological station. (US EPA, 2000). Contaminant concentrations measured by the high-volume air samplers are expressed as mass of contaminant detected per standard cubic meter of air. Ambient temperature and barometric pressure are required to calibrate the equipment and correct sample volumes to standard conditions. Wind speed and direction are required to determine if contaminants generated from site activities have migrated. Other parameters such as precipitation, relative humidity, and solar radiation are less commonly monitored and are associated with complex sites requiring health risk assessment and air modeling. The project manager must decide which parameters to monitor and what level of meteorological equipment is required for the project. The primary meteorological parameters can be measured with handheld instrumentation or a fixed meteorological station. Specifications for both types of meteorological equipment are summarized in Exhibit 2. The Kestrel 2500 Pocket Weather Meter is one brand of handheld instrumentation that features an anemometer for wind speed measurement and sensors for barometric pressure and ambient temperature. A wind vane or sock can be added to provide a qualitative indication of wind direction. The disadvantage to this combination of equipment is that they require manual data interpretation and recording. A meteorological station features a combination wind speed and direction sensor typically mounted on a 3-meter mast and sensors for ambient temperature and barometric pressure. Data from the sensors are recorded with a data logger housed in a weatherproof cabinet. The station can be run on permanent electrical power or a rechargeable battery pack. Sites requiring US EPA approval typically require a wind sensor mounted on a 10-meter tower placed in an unobstructed location (US EPA, 2000). MONITORING LOCATIONS AND SCHEDULE The specific locations to place monitoring equipment and the schedule for their operation should be tailored to each perimeter air monitoring application, but some general guidelines are discussed in this section. Monitoring Locations The primary factors in determining where to monitor are the predominant wind direction and the location of off-site receptors. Ideally, the site to be monitored would have one predominant wind direction. In this case, one monitoring location is placed at the site perimeter in the upwind direction to determine baseline conditions (i.e., conditions that exist independent of site activities). Note that in urban settings there may be other sources of contaminants than site activities and the airborne concentrations measured at the upwind location can be significant. Typically, two or more monitoring locations are placed at the site perimeter in downwind directions to determine impacts from site activities. In reality, the site may have variable wind direction (i.e., the absence of a predominant direction) or two predominant wind directions that are opposite (e.g., diurnal direction changes caused by a mountain range or water body). In this case, additional monitoring locations may be needed. The presence of off-site receptors such as individuals in neighboring residences or businesses may also influence the placement of air-monitoring locations. Even if an off-site receptor may be in a cross-wind direction and unlikely to be affected by site activities, 48 Remediation DOI: rem c 2007 Wiley Periodicals, Inc.

9 REMEDIATION Autumn 2007 placing a monitoring station at the site perimeter near the receptor can be helpful in documenting that site contaminants did not migrate. Conducting air monitoring beyond the site perimeter carries the risk that off-site sources may be detected and provide a false indication of site impacts. Secondary factors in determining where to monitor include the size of the site, the presence of obstacles, and the availability of electrical power. Large sites may require additional monitoring locations than the typical arrangement of one upwind and two downwind. If there is a limited budget, handheld meters can be used to measure contaminants at intermediate locations. Each monitoring location should be separated from obstacles such as buildings, walls, berms, or stockpiles that may hinder the correct measurement of parameters such as wind speed and direction. The separation distance should be two to ten times the height of the obstacle (US EPA, 2000). Many types of air-monitoring equipment require permanent electrical power. Extension cords can extend the monitoring radius another 100 feet from the electrical power source before the voltage drop becomes restrictive. Mobile electrical generators can be used in remote locations, but they should be placed downwind of the equipment they are servicing so that their exhaust does not interfere with monitoring. Some air-monitoring equipment can be outfitted with battery packs for use in remote locations, but their operating duration is generally limited from eight to ten hours. Monitoring Schedule The air monitoring schedule should specify the frequency and duration that the equipment should be operated during three periods of the project: baseline, start-up, and ongoing. Contaminant monitoring prior to the start of soil remediation activities (i.e., during the baseline period) enables baseline concentrations of target contaminants to be determined. The frequency of monitoring in this period is primarily based on acquiring enough data for meaningful statistics, and at least three samples should be taken to calculate an average baseline concentration. The monitoring can be conducted for eight to ten hours during daytime to represent a construction work shift or for a duration of 24 hours. Monitoring for short durations up to ten hours provides information on acute exposure and represents a worst-case exposure scenario since air quality generally improves during nighttime. Monitoring for the entire day provides chronic exposure information and tends to be a more accurate representation of exposure. If low concentrations are expected during the baseline period because ambient air quality is good, then the longer 24-hour sampling duration is preferable. Longer sampling durations equate to larger sample volumes and more contaminant mass concentrated for analytical detection. Meteorological monitoring during the baseline period is also crucial since the locations of upwind and downwind portions of the site need to be identified. Wind direction data can be obtained by operating the site meteorological station or by requesting data from the nearest National Oceanographic and Atmospheric Agency (NOAA) cooperative station (e.g., a local airport). Fifteen minutes is a typical frequency for measuring meteorological parameters, which results in 96 measurements per day. The baseline contaminant and meteorological monitoring should be conducted for at least two weeks, but a longer duration may be required to capture seasonal fluctuations in wind direction. Monitoring is usually conducted intensively at the start of the project and at the start of a new type of activity (e.g., concrete crushing). This start-up monitoring period helps Secondary factors in determining where to monitor include the size of the site, the presence of obstacles, and the availability of electrical power. c 2007 Wiley Periodicals, Inc. Remediation DOI: rem 49

10 Perimeter Air Monitoring for Soil Remediation Exhibit 3. Summary of analytical methods Estimated Typical Reporting Estimated Analyte US EPA Method Sample Media Media Cost Limit Analysis Cost PM CFR Part 50 8 by 10 quartz fiber filter $ µg $30 Appendix J Metals a SW846 series 8 by 10 quartz fiber filter $ µg $150 VOCs b TO-15 6 L Summa canister/24-hr flow controller $50/$ ppbv $200 SVOCs c TO-13A PUF/XAD cartridge and 4 diameter filter $ µg $165 PCBs d TO-4A PUF cartridge and 4 diameter filter $ µg $155 a 10 metals by ICP/MS. b 60 VOCs by GC/MS. c 18 PAHs by GC/MS. d 6 PCBs by GC/ECD. determine: when contaminant concentrations reach unhealthy levels, what construction activities are causing them, and when mitigation measures are effective in improving air quality. In the ongoing monitoring period, the monitoring frequency can be reduced based upon the initial results. If certain target contaminants are not detected during the start-up monitoring period, they may be eliminated from the program. The monitoring frequency can be daily for the first week or two of construction activity and then be reduced to weekly. The sampling duration (e.g., 24 hours) selected during the baseline period is usually carried through to the start-up and ongoing periods to enable a direct comparison of contaminant concentrations. ANALYTICAL METHODS Analytical methods for detecting contaminants in air at a soil remediation site typically target classes of contaminants. Exhibit 3 summarizes analytical methods, sample media, typical detection limits, and costs for both media and analysis for the target contaminant classes discussed previously. Note that filter- or sorbent-based methods are different than whole air methods in that the laboratory provides analytical results in mass of contaminant detected rather than the concentration of the contaminant in air. Since contaminant concentrations are the desired product of air monitoring, the project manager must divide the masses detected by the laboratory by the sample volumes. Greater sample volumes correspond to lower concentration detection limits. DATA INTERPRETATION For a site with one predominant wind direction, the contribution of contaminants from site activities would equal the difference between concentrations measured at the downwind and upwind locations (i.e., background subtraction). The net contaminant 50 Remediation DOI: rem c 2007 Wiley Periodicals, Inc.

11 REMEDIATION Autumn 2007 concentrations could be compared to limits set by the regulatory agency and work practices could be modified if necessary. Air-monitoring data interpretation becomes more difficult when wind direction is variable or when regulatory action levels for the site are not specified. Regardless of wind direction, it can be helpful to conduct an immediate check as to whether unhealthy conditions are being generated at the site perimeter. Contaminant concentrations measured from the monitoring equipment can be compared directly to state and federal regulatory limits (US EPA, 2006). Since off-site receptors are generally not located at the immediate site perimeter, this provides a conservative screening approach. Regulatory Concentration Limits State and federal regulations may provide concentration limits for contaminants targeted for monitoring. The US EPA has established National Ambient Air Quality Standards (NAAQS) and preliminary remediation goals (PRGs) for many contaminants in ambient air. The Occupational Safety and Health Administration levels are generally not appropriate for perimeter monitoring because they were designed with an indoor worker exposure scenario in mind. National Ambient Air Quality Standards NAAQS have been established for six criteria air pollutants including particulate matter and lead. The standards consist of an annual average concentration limit and a 24-hour concentration limit for each pollutant. An action level for an environmental site can be set at the 24-hour concentration limit. Exceeding the NAAQS for a short duration may not indicate an immediate health problem, but rather a need to modify site work practices or implement mitigation measures (e.g., water spraying). Preliminary Remediation Goals The US EPA Region 9 has established Preliminary Remediation Goals (PRGs) for specific contaminants (US EPA, 2004). PRGs are risk-based concentrations in environmental media (e.g., ambient air) that are considered by the US EPA to be health-protective of human exposures (including sensitive groups) over a lifetime. PRGs correspond to fixed levels of risk (i.e., either a one in a million [ ] cancer risk or a noncarcinogenic hazard quotient of 1.0) for a residential or industrial exposure scenario over a 30-year duration. A soil remediation project is typically conducted over a brief period of several months, which represents significantly less exposure than 30 years. For short-term exposure, site action levels can be set at 10 or 100 times the PRG values, which correspond to risk levels of and , respectively. The US EPA has established National Ambient Air Quality Standards (NAAQS) and preliminary remediation goals (PRGs) for many contaminants in ambient air. SUMMARY AND CONCLUSIONS Project managers should be aware that soil remediation activities at an environmental site could create airborne contaminants that may pose a health concern for individuals in neighboring residences or businesses. Perimeter air monitoring may be required by a c 2007 Wiley Periodicals, Inc. Remediation DOI: rem 51

12 Perimeter Air Monitoring for Soil Remediation regulatory agency to determine if unhealthy conditions are created and if work practices should be limited or modified. The project manager may need to provide the regulatory agency a detailed work plan that describes how the target contaminants will be monitored. Perimeter air monitoring includes the proper selection of specialized equipment for target contaminants, analytical methods, sample locations and schedule, and data collection and reporting techniques. The operation of a site meteorological station is crucial to adjust and interpret the data generated from the specialized monitors. For project managers that are unfamiliar with monitoring contaminants in the air medium, it may be helpful to read the reference material and consult an air-monitoring specialist prior to conducting a perimeter air-monitoring program. ACKNOWLEDGMENTS The author would like to thank Heidi Hayes (Air Toxics, Ltd.), Paul Duda (CHESTER LabNet), Karen Dahl (Severn Trent Laboratories), Wilbur Tisch (Tisch Environmental, Inc.), Sean O Doherty (EQUIPCO Rentals Corp.), and Mark Podrez (RTP Environmental Associates, Inc.) for their contributions to this article. REFERENCES United States Environmental Protection Agency (US EPA). (1995). Superfund program representative sampling guidance: Volume 2 Air (short-term monitoring). Interim final. EPA 540/R-95/140. Washington, DC: Author. United States Environmental Protection Agency (US EPA). (1998). Reference method for the determination of particulate matter as PM-10 in the atmosphere. 40 CFR, Chapter I, Appendix J to Part 50, Washington, DC: Author. United States Environmental Protection Agency (US EPA). (2000). Meteorological monitoring guidance for regulatory modeling applications. EPA-454/R Washington, DC: Author. United States Environmental Protection Agency (US EPA). (2004). Region 9 preliminary remediation goal (PRG) table. Retrieved May 1, 2007, from 04prgtable.pdf United States Environmental Protection Agency (US EPA). (2006). A preliminary risk-based screening approach for air toxics monitoring data sets. Version 1.2. EPA-904-B Washington, DC: Author. United States Environmental Protection Agency (US EPA). (2007). Particulate matter basic information. Retrieved May 1, 2007, from Guy J. Graening manages environmental investigation, remediation, and perimeter air monitoring projects for Brown and Caldwell in Sacramento, California. He is a California-registered professional mechanical engineer and holds a BS in aeronautical engineering from Stanford University and an MS in mechanical engineering from the University of Dayton. 52 Remediation DOI: rem c 2007 Wiley Periodicals, Inc.