Attachment 8-Groundwater Well Sampling Procedures (110).pdf

Agency Document ID Number

DLR-OER-110

Groundwater Well Sampling Procedures

SOP OER-0110

Prepared for:

West Virginia Department of Environmental Protection

Division of Land Restoration Office of Environmental Remediation

Author Revision

No.

Effective

Date Description of Changes

Type of Change

Ruth Porter 1.0 7/1/2010 Reformatted, added SOP ID #, and renumbered. Supersedes Revision 0.0.

Editorial

Additional detail provided. Technical

Dave Long 2.0 9/21/2016 Revised procedures. Reformatted Editorial, Technical

Ross Brittain

3.0 11/10/2020 Edited grammatical issues, clarified details and changed it to XRF instruments in general.

Editorial, Technical

APPROVED:

Name Date

Digitally signed by: Ross Brittain DN: CN = Ross Brittain email = ross.a.brittain@wv.gov C = US O = DEP OU =

DLR-OER

Date: 2021.01.20 09:19:26 -05'00'

Ross Brittain

GROUNDWATER WELL SAMPLING PROCEDURES

SOP OER-0110

Table of Contents

1.0 Scope and Application

2.0 Summary of Method

3.0 Sample Preservation, Containers, Handling, and Storage

4.0 Interferences and Potential Problems

4.1 General

4.2 Purging

5.0 Equipment Apparatus

6.0 Reagents

7.0 Procedures

7.1 General Procedures

7.2 Peristaltic Pump (Low Flow Sampling)

7.3 Submersible Pump (Low Flow Sampling)

7.4 Bailer Method

7.5 Sampling Wells in Low-Permeability Formations

8.0 Calculations

9.0 Quality Assurance/Quality Control

10.0 Data Validation

11.0 Health and Safety

12.0 References

List of Acronyms and Abbreviations

DQO Data Quality Objectives

FID Flame Ionization Detector

HASP Health and Safety Plan

HAZWOPER Hazardous Waste Operations and Emergency Response

ID Identification

IDW Investigation Derived Wasted

NTU Nephelometric Turbidity Unit

OER Office of Environmental Remediation

ORP Oxidation Reduction Potential

OSHA Occupational Safety and Health Administration

PDBS Passive Diffusion Bag Sampler

PID Photoionization Detector

PPE Personal Protective Equipment

QA/QC Quality Assurance/Quality Control

QAPrP Quality Assurance Project Plan

SAP Sampling and Analysis Plan

SAWP Site Assessment Work Plan

SDS Safety Data Sheet

SOP Standard Operating Procedure

TOC Top of Casing

USEPA United States Environmental Protection Agency

WVDEP West Virginia Department of Environmental Protection

VOC Volatile Organic Compounds

Disclaimer: Any mention in this SOP of any products or services does not constitute or imply the endorsement, recommendation or favoring by WVDEP or any of its employees or contractors acting on its behalf.

1.0 SCOPE AND APPLICATION

The purpose of this standard operating procedure (SOP) is to provide general reference information on sampling of groundwater wells for projects in the Office of Environmental Remediation (OER) within the West Virginia Department of Environmental Protection (WVDEP). Groundwater samples provide data on groundwater quality and give an indication of the nature and extent of any groundwater contamination. Groundwater sampling procedures are generally split into two tasks, purging and sampling. Purging is the process of removing water from the monitoring well prior to sampling and replacing it with adjacent groundwater from within the formation. This ensures that a more representative sample of the actual aquifer condition is collected. Every effort must be made to ensure that the sample is representative of the particular zone of water being sampled. These procedures are designed to be used in conjunction with analyses for the most common types of ground water contaminants (i.e., volatiles, semi-volatiles, and metals). These procedures may be varied or changed as required, dependent upon site conditions, equipment limitations or limitations imposed by the procedure.

The procedures utilized at a site should be documented and included in the site investigation report.

2.0 SUMMARY OF METHOD

In order to obtain a representative groundwater sample for chemical analysis, it is important to either purge water from the monitoring well or take steps to ensure that only water meeting the data quality objectives (DQO’s) and work plan objectives is removed from the well during sampling. Purging is generally performed by removing a pre-determined number of well volumes (well-volume purging), or by removing groundwater until water quality parameters have stabilized. Purging is conducted to remove stagnant water in the well casing and/or immediately adjacent to the well screen before collecting the sample. This may be achieved in a variety of ways. Commonly used methods include but are not limited to the use of bailers and pumps. When utilizing pumps, low flow (or low stress) purging/sampling is recommended.

Low flow purging/sampling is also highly recommended when sampling for volatile organic compounds (VOC’s) and metals. Due to agitation, the tendency to mix formation water with stagnant water above the well screen, and the tendency to stir up fines in the bottom of the well, purging and sampling with a bailer should only be conducted as a last resort. Data is collected under the OER programs to delineate the extent of contamination from sites and to formulate remedial actions utilizing risk-based standards; therefore, a high level of data accuracy and validation is required for these programs. As such, groundwater data collected for volatile organic compounds (VOC’s) and metals analysis utilizing bailers for purging and sampling may not be accepted in these programs. Note that passive sampling, minimal purge and no-purge methods do not attempt to purge the stagnant water in the well prior to sampling.

The primary method of sampling groundwater is to use low-flow sampling. However, low-flow sampling may not be possible or appropriate in low-yielding wells, in which case the well volume should be purged before sampling. When purging, monitoring wells should be purged, at a minimum, the equivalent of three times the well volume of standing water or they should continue to be purged until specific conductance, temperature, and pH stabilize. For well-volume purging, the volume of water present in each well shall be computed based on the length of water column and well casing diameter. Once purging is completed, sampling may proceed.

Care should be taken when choosing the sampling device as some will affect the integrity of the sample, depending on the analytical parameters of interest. If information about the contaminant levels in a well is known, then sampling should be performed in a progression from the least to most contaminated well. Specific details for sampling at any location should be found in the Sampling and Analysis Plan (SAP) or Site Assessment Work Plan (SAWP, hereafter both are referred to as SAWP).

3.0 SAMPLE PRESERVATION, CONTAINERS, HANDLING, AND STORAGE

The type of sample container, the preservative, holding time, and filtering requirements are all dependent upon the type of analysis to be performed upon the sample. This information should be clearly set forth in the Sampling and Analysis Plan (SAWP) for the site. The sampler should consult the SAWP for all pertinent information relating to the proper sample preservation, type of containers, handling, and storage procedures for their project. A pair of clean, new, non-powdered disposable gloves shall be worn each time a different location is sampled to prevent cross-contamination. Samples should be collected directly from the sampling device (i.e. bailer or pump) into appropriate laboratory cleaned containers, without making contact with the sampling device. Samples shall be appropriately preserved, labeled, and placed in a cooler to be maintained at ≤6ºC, but without freezing the sample, in accordance with the SAWP requirements. The samples should be shipped with adequate packing and cooling to ensure that they arrive at the laboratory intact and still cold. Refer to Table 2 of the OER QAPrP for information on sample containers, preservation, and holding times for common contaminants.

4.0 INTERFERENCES AND POTENTIAL PROBLEMS

4.1 General

The goal is to obtain a representative sample of the groundwater. Proper field sampling techniques need to be utilized in order to ensure that a representative sample is collected and the sampler does not compromise the sample through their actions. Analysis can be compromised by field personnel in three primary ways; taking an unrepresentative sample, by incorrectly handling the sample or by improperly labeling the sample. There are a variety of ways to introduce contaminants into a sample; that is why it is very important to follow sampling protocols.

4.2 Purging

Purging is generally conducted with the use of a pump or a bailer. Two commonly recognized purging methods include the low-stress approach (utilized during low-flow sampling) and the well-volume approach.

5.0 EQUIPMENT APPARATUS

The following are some of the materials and equipment that are potentially needed for groundwater well sampling activities:

Water level indicator Photoionization detector (PID) and/or Flame Ionization Detector (FID) Logbook

Calculator Field data sheets and sample labels Chain of custody records and seals Sample and shipping containers Preservatives, as applicable Pails, tubs, or buckets Plastic sheeting Packing materials and Ziploc plastic bags Decontamination solutions (i.e., tap water, non-phosphate soap, deionized water) Brushes Clean, decontaminated or new unused bailers Nylon line, enough to dedicate to each well In-line filters, 0.45 microns (µm), typically for sampling dissolved metals Water quality meter (e.g., YSI) 55-gallon drums for storage of purged groundwater Paper towels Personal protective equipment (PPE) Pump

6.0 REAGENTS

Reagents may be utilized for preservation of samples and for decontamination of sampling equipment. Refer to the SOP for the decontamination procedures and required reagents. Refer to the site-specific Sampling and Analysis Plan for the preservatives required for the specified analysis to be performed.

7.0 PROCEDURES

7.1 General Procedures

The following general procedures are applicable to all well sampling events.

a) Place plastic sheeting on the ground in the vicinity of the well to ensure that sampling equipment does not contact the ground surface.

b) Remove the well cap and check for volatile organics in the headspace using a PID/FID, if applicable. If concentrations are detected in the headspace above the action levels established in the Site Health and Safety Plan, appropriate personal protective equipment will be required.

c) Water-level measurement will be made using an electronic water level meter capable of measuring water levels to the nearest 0.01 foot.

d) Typically, all depth measurements should be made from the top (the highest point) of the inner well casing (top-of-casing, TOC), also known as the well riser. The reference point location should be described in the field logbook and should be used in all subsequent sampling efforts. Check for well damage at each well that could indicate a shift in the reference point. Lower the water-level measurement tape and gauge the depth to water and total depth of the well. Care should be taken to assure that the water-level measurement device hangs freely in the monitoring well and is not adhering to the wall of the well casing. Take replicate measurements (at least 3) in each well to ensure accuracy. Record water level data in the field logbook. The water level meter should be left in the well during low-flow purging and sampling.

e) As necessary (depending on the purging/sampling approach), determine the well volume using one of the formulas in Section 8.0 of this SOP. If more than 24 hours have passed since water levels were measured, re-gauge and record the static water level prior to purging.

7.2 Peristaltic Pump (Low Flow Sampling)

(Note that USEPA does not recommend using peristaltic pumps for VOC samples.)

a. Utilizing a water-level meter, find the depth to water. If water is above the screen interval, the tubing should be set at the middle of the screen; however, if the water level is below the top of the screen, the tubing should be set in the middle of the water column.

b. Lower tubing to the appropriate depth. If tubing coils, brass or stainless-steel weights can be added to the bottom of the tubing, capped by a small piece of silicon tubing. At the surface, tubing should connect to silicon tubing, which is placed within the peristaltic apparatus. Additional tubing is connected to the outflow side of the apparatus, which is then joined to the intake of the flow-thru cell. The flow-thru cell’s output should connect directly into a waste-water receptacle.

c. Record the location of the tubing intake (feet below TOC) so that future sampling will occur at the same depth interval.

d. Start the pump at the lowest possible flow setting. Increase the pump rate gradually until a continuous flow is achieved from the discharge tubing. The discharge rate of the pump can be determined by using a graduated cylinder and a stopwatch. Record the flow rate in milliliters per minute. Pumping rates should be kept at minimal flow to ensure minimal drawdown in the monitoring well. The flow rate should be maintained between 100 mL/min and 500 mL/min (0.03-0.13 gal/min), or between 100 mL/min and 300 mL/min (0.03-0.08 gal/min) for VOC sampling, throughout the purging and sampling activities. Flow rates achieved during the purging period should also be maintained throughout the sampling period.

e. When a stable purge rate has been established (i.e., pumping rate is equal to or less than well recharge rate), begin recording water quality readings at a frequency of every three to five minutes. Note that drawdown should not exceed 4 inches.

f. Continue to purge the well until water quality parameters have stabilized within the following stabilization criteria over three consecutive readings. Record the purging and sampling data in the field logbook.

g. Parameter Criteria

Water level drawdown

<0.3 feet pH +/- 0.1 standard units Conductivity +/- 3% of readings Temperature +/- 3% of readings Dissolved Oxygen

+/- 0.3 mg/L or 3% of readings, whichever is greater

Turbidity +/- 10% of readings for values greater than 1 nephelometric turbidity unit (NTU)

Eh/ORP +/- 10 millivolts

h. Once the water quality parameters have stabilized, collect the ground water sample by detaching the tubing from the flow-through cell. Under no circumstances should the ground water sample be collected from the flow-through cell discharge stream. Collect the samples in the following order:

i. Volatile organic compounds (Ensure that volatiles are immediately capped and have no headspace by inverting the vial, tapping gently and waiting at least 10 seconds. If an air bubble appears, unscrew the cap and pop the bubble or refill with more sample and re-seal the vial. Do not collect a sample with air trapped in the vial.)

ii. Semi-volatile organic compounds

iii. Nitroaromatics

iv. Herbicides/pesticides

v. Metals

vi. All other parameters

i. Samples for total metals analysis, if applicable, should be collected prior to sampling for dissolved metals. However, OER generally only collects dissolved metals for groundwater assessment, and does both total metals and dissolved metals for surface water only. To collect samples for dissolved metals analysis, a 0.45μm filter should be added to the discharge line. Samples for dissolved metals analysis should be collected after 500 mL of water has passed through the in-line filter. Remove the filter following collection of samples for dissolved metals.

j. Preserve and filter according to the requirements set forth in the site-specific SAWP. Label the sample containers using indelible pen, attach a chain-of-custody seal to each container lid, place the containers in plastic bags, and place them on ice in a cooler. Record sample collection date and time. Handle and store samples in accordance with the approved QAPrP and/or SAWP.

k. Remove the water level meter (if not already removed) and then the pump from the monitoring well. Decontaminate the pump and dispose of the tubing if it is non-dedicated to the well. Protect equipment from contamination by storing on plastic sheeting.

l. Close and lock the well.

m. Record the following information in the field logbook:

Sample ID

Location

Purging and sampling data

Color

Odor

Field screening instrument readings, if applicable

Any other pertinent information (e.g., date, time and sampler)

7.3 Submersible Pump (Low Flow Sampling)

a) Connect the pump tubing to the flow-through cell and connect the multi-parameter probe to the cell. Connect the discharge from the flow-through cell to a purge water drum for later IDW disposal. Keep the flow-through cell out of direct sunlight.

b) Lower the pump slowly in the well to minimize the disturbance of the water column.

Do not let the pump, tubing, electrical cords, and support cable touch the ground as you are lowering the pump into place.

Secure the pump at the desired depth using the support cable. The entire pump and tubing assembly should be supported by a stainless steel or Teflon coated cable. It is not advisable to use the tubing to support the pump.

Place the pump intake as close to the middle of the screened interval for wells with water levels above the top of the screen. For wells with water levels below the top of the screen, the pump should be set near the top of the water column and slowly lowered, being careful not to expose the screen to air, until the pump is placed in the middle (or just below the middle) of the water column.

The pump or water level probe should not be allowed to hit the bottom of the well before or during sampling because it will disturb sediment. It should be noted that at least three feet of water is needed to implement low flow sampling.

c) Record the location of the pump intake (feet below TOC) so that future sampling will occur at the same depth interval.

d) Start the pump at the lowest possible flow setting. Increase the pump rate gradually until a continuous flow is achieved from the discharge tubing. The discharge rate of the pump can be determined by using a graduated cylinder and a stopwatch. Record the flow rate in gallons per minute. Pumping rates should be kept at minimal flow to ensure minimal drawdown in the monitoring well.

The flow rate should be maintained between 100 mL/min and 500 mL/min (0.03-

0.13 gal/min), or between 100 mL/min and 300 mL/min (0.03-0.08 gal/min) for VOC sampling, throughout the purging and sampling activities. Flow rates achieved during the purging period should also be maintained throughout the sampling period.

e) When a stable purge rate has been established (i.e., pumping rate is equal to or less than well recharge rate), begin recording water quality readings at a frequency of every three to five minutes. Note that drawdown should not exceed 4 inches.

f) Continue to purge the well until the water quality parameters have stabilized within the following stabilization criteria over three consecutive readings.

Record the purging and sampling data in the field logbook.

Parameter Criteria Water level drawdown

<0.3 feet pH +/- 0.1 standard units Conductivity +/- 3% of readings Temperature +/- 3% of readings Dissolved Oxygen

+/- 0.3 mg/L or 3% of readings, whichever is greater

Turbidity +/- 10% of readings for values greater than 1 nephelometric turbidity unit (NTU)

g) Once the water quality parameters have stabilized, collect the ground water sample by detaching the tubing from the flow-through cell. Under no circumstances should the ground water sample be collected from the flow-through cell discharge stream. Collect the samples in the following order:

i. Volatile organic compounds (Ensure that volatiles are immediately capped and have no headspace by inverting the vial, tapping gently and waiting at least 10 seconds. If an air bubble appears, unscrew the cap and pop the bubble or refill with more sample and re-seal the vial. Do not collect a sample with air trapped in the vial.)

ii. Semi-volatile organic compounds

iii. Nitroaromatics

iv. Herbicides/pesticides

v. Metals

vi. All other parameters

h) Samples for total metals analysis should be collected prior to sampling for dissolved metals. To collect samples for dissolved metals analysis, a 0.45μm filter should be added to the discharge line. Samples for dissolved metals analysis should be collected after 500 mL of water has passed through the in-line filter. Remove the filter following collection of samples for dissolved metals.

i) Preserve and filter according to the requirements set forth in the site-specific SAWP. Label the sample containers using indelible pen, attach a chain-of-custody seal to each container lid, place the containers in plastic bags, and place them on ice in a cooler. Record sample collection date and time. Handle and store samples in accordance with the approved QAPrP and/or SAWP.

j) Remove the water level meter (if not already removed) and then the pump from the monitoring well. Decontaminate the pump and dispose of the tubing if it is non-dedicated to the well. Protect equipment from contamination by storing on plastic sheeting.

k) Close and lock the well.

l) Record the following information in the field logbook:

Sample ID Location Purging and sampling data Color Odor Field screening instrument readings, if applicable

7.4 Bailer Method

[As noted above, bailers are not recommended for most purging/sampling situations, other than in low-permeability formations (see below). If bailers are to be used, justification must be provided in the SAWP.]

a) Purge the well by manually bailing until a minimum of three well volumes have been removed and water quality parameters have stabilized within the following stabilization criteria over three consecutive readings. Record the purging and sampling data in the field logbook.

Parameter Criteria pH +/- 0.1 standard units Conductivity +/- 3% of readings Temperature +/- 3% of readings Dissolved Oxygen +/- 0.3 mg/L or 3% of readings, whichever is greater Turbidity +/- 10% of readings for values greater than 1 nephelometric turbidity unit (NTU)

b) Lower bailer slowly and gently into well, do not drop or splash bailer into the water column. Stop lowering at desired point adjacent to well screen. Withdraw a sample from the well, transfer the sample from the bailer directly into sample containers. Preserve and filter according to the requirements set forth in the site-specific SAWP.

c) Collect the samples in the following order:

i. Volatile organic compounds (Ensure that volatiles are immediately capped and have no headspace by inverting the vial, tapping gently and waiting at least 10 seconds. If an air bubble appears, unscrew the cap and pop the bubble or refill with more sample and re-seal the vial. Do not collect a sample with air trapped in the vial.)

ii. Semi-volatile organic compounds

iii. Nitroaromatics

iv. Herbicides/pesticides

v. Metals

vi. All other parameters

d) To collect samples for dissolved metals analysis, a 0.45μm filter should be attached to a syringe (or other device to force water through the filter). Samples for dissolved metals analysis should be collected after 500 mL of water has passed through the filter. Discard the filter following collection of samples for dissolved metals.

e) Label appropriate sampling containers with sampling details and custody information.

f) Replace the well cap and lock the cover.

g) Record the following information in the field logbook:

Sample ID Location Purging and sampling data Color Odor Field screening instrument readings (i.e., water quality, PID)

7.5 Sampling Wells in Low-Permeability Formations

Wells located in low-permeability formations (i.e., slow-recovery wells, wells that can be purged to dryness, etc.) require alternate sampling procedures than the methods listed above. One approach, for a well screened below the water table, is to remove the stagnant water in the casing to just above the top of the screened interval, to prevent the exposure of the gravel pack or formation to atmospheric conditions. The pumping rate should be as low as possible to minimize disturbance as much as possible in the well. A sample should then be secured from the water within the screened interval. Another approach is to use a dedicated pump located within the screened interval and purge only the pump and tubing volume before collecting the sample (“passive sampling”). Another type of passive sampling uses a passive diffusion bag sampler (PDBS) which is deployed in the screened interval of the monitoring well for a period recommended by the manufacturer. Analytes of interest passively diffuse into deionized water contained within the sampler as the well equilibrates. It should be noted that only certain VOCs will diffuse into the PDBS. The PDBS is retrieved from the well and the sample is poured into appropriate sample containers. Other no-purge samplers include equilibrated grab samplers such as the HYDRASleeve™ and the Snap Sampler®. These samplers are deployed in the screened interval of the monitoring well and the well is allowed to equilibrate. Use of these passive sampling and no-purge sampling techniques will require development of a method-specific SOP to be included in the SAWP.

8.0 CALCULATIONS

Volume estimates per foot for common inside diameter tubing is presented in the following table:

Tubing Inside Diameter (inches)

Tubing Volume (gallon per foot)

1/4 0.0003 3/8 0.0057 1/2 0.010

If it is necessary to calculate the volume of the well, utilize the following equation:

V = khπr2

Where: V = Volume (gallons) π = 3.14 r = radius of the well (feet) h = water column height (feet) k = conversion factor (7.48 gal/ft3)

Or if the variables are known:

V = k{r2 ich + [(r2 bh - r2 och) * ne]}

Where: V = Volume (gallons) ric = radius inside diameter of casing (feet) rb = radius of borehole (feet) roc = radius outside diameter of casing (feet) h = water column height (feet) k = conversion factor (7.48 gal/ft3) ne = effective porosity of filter pack material (~ 35%)

9.0 QUALITY ASSURANCE/QUALITY CONTROL

The following general quality assurance procedures apply:

All data must be documented on field data sheets and/or within the field logbook.

All instrumentation should be operated and calibrated in accordance with the manufacturer’s instructions unless specified otherwise in the site-specific SAWP.

The collection of an equipment rinsate blank is recommended to evaluate potential for cross-contamination from the purging and/or sampling equipment.

The collection of duplicate samples will likely be a requirement set forth in the

SAWP and/or QAPrP.

Trip blanks are required for each cooler with samples for volatile organic compounds analysis.

Refer to the site-specific SAWP and/or QAPrP for specific quality assurance/quality control measures that may be applicable for the given project.

10.0 DATA VALIDATION

Data validation requirements set forth in the site-specific SAWP or QAPrP shall be adhered to for any given project. Results of quality control samples will be evaluated for contaminants.

This information will be utilized to qualify the environmental sample results in accordance with the project's data quality objectives as set forth in the site-specific SAWP and/or QAPrP.

11.0 HEALTH AND SAFETY

OSHA regulations should be adhered when working with potentially hazardous materials.

Personnel performing environmental work at OER sites should have their 40 Hour Hazardous Waste Operations and Emergency Response (HAZWOPER) with 8 Hour refreshers as appropriate. Some level of Personal Protective Equipment (PPE) is generally required for all sampling and decontamination activities. The appropriate level of PPE for these activities may be found in the site-specific SAWP and/or the Site Health and Safety Plan (HASP). Personnel should adhere to the safety requirements outlined in the site-specific plans. The following is a summary of just some of the hazards associated with well sampling:

Exposure to unknown contaminants.

Lifting injuries associated with moving equipment, coolers with samples, and retrieving pumps and bailers.

Heat/cold stress as a result of exposure to extreme temperatures and the use of PPE.

Slips, trips, and fall hazards.

Potential electrical shocks associated with use of submersible pumps.

Biohazards, such as snakes, biting insects, and poison ivy.

Safety data sheets (SDS) should be readily available on-site for all decontamination solvents or solutions, as well as known contaminants, as required by the Hazard Communication Standard requirements set forth in the OSHA regulations. Investigation derive waste (IDW) generated from decontamination activities requires proper handling, storage, and disposal. Refer to the site-specific SAWP for IDW procedures.

12.0 REFERENCES

Guidance for Preparing Standard Operating Procedures (SOPs), EPA QA/G-6, US EPA, Office of Environmental Information, April 2007

Ground Water Well Sampling, SOP# 2007, US EPA, Environmental Response Team, January 26, 1995

Field Sampling Procedures Manual, New Jersey Department of Environmental Protection, August 2005, Updated – April, 2011

Standard Operating Procedure for Ground Water Sampling, The Office of Environmental Measurement and Evaluation, EPA New England - Region 1, January 9, 2003

ASTM D4448-01 (Reapproved 2013), Standard Guide for Sampling Ground-Water Monitoring Wells, ASTM International, West Conshohocken, PA, 2013, www.astm.org

Ground-Water Sampling Guidelines for Superfund and RCRA Project Managers, Ground Water Forum Issue Paper, EPA 542-S-02-001, EPA Technology Innovative Office, Office of Solid Waste and Emergency Response, May, 2002

ITRC (Interstate Technology & Regulatory Council). 2005. Technology Overview of Passive Sampler Technologies. DSP-4. Washington, D.C.: Interstate Technology & Regulatory Council, Authoring Team. www.itrcweb.org