GROUNDWATER MONITORING GUIDANCE DOCUMENT Introduction It is important to understand the difference between a ground water monitoring well and a water supply well. This distinction is obvious when comparing well construction techniques characteristic of various formations throughout the State. For instance, the western part of North Carolina is dominated by a series of crystalline metamorphic rocks. Subsequently, water supply wells in these regions are typically constructed by drilling through the saprolite (weathered rock) and into very hard resistant rock below the true water table. Because of the resistant lithologic character of these units, well drillers often feel that it is unnecessary to case a well drilled in rock. This rationale may hold true for drinking water supply wells but it is unacceptable for ground water monitoring purposes due to contamination problems associated with uncased or partially cased wells. Subsequently the Solid Waste Section requires completely cased boreholes for all ground water monitoring wells. The Section strongly urges all contractors and consultants to become familiar with well construction techniques and specifications of monitoring wells as illustrated by the ground water monitoring well schematic (figure 1). Monitoring well construction standards must conform to requirements cited in 15A NCAC 2C "Well Construction Standards: Criteria and Standards Applicable to Water Supply and Certain Other Wells". A. Specific Monitoring Well Construction Requirements Because the location and design of ground water monitoring wells at landfills is one of the most critical phases of site development, the importance of a thorough hydrogeologic evaluation which clearly delineates ground water elevation and flow characteristics is of highest significance. In order to assure consistent and proper installation techniques which are in accordance with EPA regulations, all deviations to the following methods, or questions regarding materials, monitoring well locations or other techniques, should be directed to the Solid Waste Section Hydrogeologist at (919) 733-0692, c.o. the Solid Waste Section, P.O. Box 27687, Raleigh, N.C. 27611-7687. The Solid Waste Section reserves the right to evaluate in the field, the actual well installation techniques and procedures. Proper installation of monitoring wells and placement of well screens is critical to assure that the ground water sample represents the portion of the aquifer where contaminants may migrate. The maximum length of the well screen is 15 feet. Well screens should be placed at depths based on hydrogeologic data collected during previous site investigations. Well sorted sand to be used as a pre-screening filter pack of influent ground water should be washed to remove all fines in order to prevent clogging of the well screen. In connecting well casing sections threaded pipe fittings are required as opposed to various types of glues or other cements which have the potential for contaminating ground water samples. Various casing types and sizes are available and acceptable for installation of monitoring wells. Generally, 2" inside diameter PVC casing is used. Under certain circumstances stainless steel or Teflon well casings are preferred, however, Teflon casings are relatively malleable and may not hold-up under stressed conditions. The most common size bore holes include those which are drilled with an 8" hollow-stem auger. These will accommodate 2" and 4" I.D. casings. The Solid Waste Section recommends the use of 2" I.D. casings for wells drilled 100' or less. Monitoring wells drilled to depths exceeding 100' such as wells designed to monitor water quality through possible fracture patterns may be cased with 4" I.D. casings to allow for the use of pumps to purge the wells. A typical monitoring well schematic is shown in figure 1. In general all Type II monitoring wells used for detection monitoring should conform to the construction design specifications indicated. Because accidental or natural events may influence the condition of monitoring wells, an on-going well inspection and maintenance program should be conducted by landfill personnel. Some of the items which should be regularly maintained by facility personnel include: 1) insuring that all wells are locked at all times, 2) insuring that all casings have a secure cap, 3) insuring that the outer casing is upright and undamaged by equipment or vehicles, 4) insuring that each well location is clearly marked and an unobstructed path exists, free of dense vegetation. These maintenance factors are critical for helping insure proper ground water monitoring. B. Ground-water Monitoring Because a tremendous liability is associated with water quality data obtained from analytical laboratory results, it is of the utmost importance to insure the validity and integrity of sampling techniques and methodology. Two distinct monitoring systems exist which may be used to purge and sample a monitoring well. These two systems are the portable monitoring system and the dedicated monitoring system. Portable Monitoring 1. Bailers The portable monitoring system is by far the most common method used to collect samples to monitor ground water quality. The most popular portable purging and sampling device is the Teflon bailer. Teflon is considered to be a preferred material to use for ground water monitoring because of its relatively inert chemical character. Stainless steel bailers are also acceptable but are not used as frequently. Because of the possibility of an interaction between the sample and bailer components, the use of high density polyethylene (HDPE) bailers or PVC bailers is generally not allowed for collecting samples for analysis of ground water quality . The bailer line that attaches to bailers should consist of either 1) nylon rope, 2) Teflon coated wire, 3) single stranded stainless steel wire, or 4) some other monofilament line. A new segment of line should always be used for each well. Unused line should be protected from contamination as much as possible. 2. Pumps A number of types of submersible electric pumps are available with stainless steel and Teflon components that are allowed to be used in certain circumstances (ie. deep wells with large diameter casings) for purging of wells prior to sampling. Purge rates must be carefully controlled or the resulting agitation within the well may change the sample chemistry. Electric pumps designed to remain outside the well on the ground surface with an intake pipe inside the well can also be used for purging. However, intake tubing placed in the well must be composed of Teflon and properly decontaminated prior to use. Sampling is discouraged with this system because of the obvious problem with flow control rate. Hand pumps are useful for purging wells in a relatively short period of time, but unfortunately, are usually unsuitable for sampling. The primary reasons being the possibility of contamination and lack of availability of Teflon or stainless hand-pumps in the commercial market. In addition, the regulation of flow rate, which is very important for most sampling situations, is difficult to control. Proper cleaning and decontamination can be a problem in the field if a pump is used for more than one well. Dedicated Monitoring So far previous discussions have focused on equipment related to portable monitoring systems. A short overview of dedicated systems is in order. Dedicated well monitoring differs from portable monitoring primarily by the permanency of the set- up. Because portable systems require the use of much of the same equipment from well to well, great care must be exercised to avoid cross contamination. Dedicated systems, however, require no between-well cleaning procedures. These systems offer permanently affixed down-well and well-head components that are capped after initial set-up. All dedicated monitoring systems must be approved by the Solid Waste Section before installation. Most dedicated monitoring systems are comprised of an in- well submersible bladder pump, with air supply and sample discharge tubing, and an above-ground driver/controller for regulation of flow rates and volumes. The pump and all tubing housed within the well should be composed of Teflon or stainless steel components. This includes seals inside the pump, the pump body and fittings used to connect tubing to the pump. Because ground water will not be in contact with incompatible constituents and because the well is sealed from the surface, virtually no contamination is possible from intrinsic sources during sampling and between sampling intervals. Flow rate during sample collection is very important when using any type of pump system. Changes in sample pH, sample chemistry and volatilization of organic constituents are possible with high flow rates during purging and sample collection. Flow rates as low as 100ml/ min. are necessary when collecting samples. In contrast to the above described system, occasionally individuals are under the false impression that bailers which are initially cleaned in a laboratory and permanently placed in monitoring wells are considered dedicated systems and subsequently are acceptable for monitoring purposes. While it is permissible to assign a particular bailer to an individual well, the bailer should always be decontaminated between sampling events and never stored inside the well. A separate laboratory cleaned Teflon or stainless steel bailer is required for each monitoring well during each sampling episode. Equipment Cleaning Procedures The preferred setting for cleaning all equipment coming in contact with samples or ground water inside a monitoring well is within an established and properly equipped laboratory. In general, field cleaning of sampling equipment such as bailers is not allowed. With detection limits of parts per million or even parts per billion for various sample constituents, extreme care should be taken to insure that all sampling equipment is properly cleaned before use. The following procedures have been established by EPA Region IV as a minimum for cleaning equipment for sample collection for RCRA based programs. Teflon bailers, etc.: 1. Phosphate-free soap and tap water wash 2. Tap water rinse 3. 10% nitric acid or 10% hydrochloric acid soak 4. Deionized or distilled water rinse 5. Isopropyl alcohol rinse 6. Deionized or distilled water rinse 7. Air dry 8. Aluminum foil wrap with shiny side out Stainless steel bailers, etc.: 1. Phosphate-free soap and tap water wash 2. Tap water rinse 3. Deionized or distilled water rinse 4. Isopropyl alcohol rinse 5. Deionized or distilled water rinse 6. Air dry 7. Aluminum foil wrap with shiny side out Sample Collection Of primary importance in the collection of monitoring well samples is the need to collect a sample that is as representative of the ground water as possible. It is very important not to add to, delete from, or cause any change in the sample being collected. The use of properly decontaminated equipment with acceptable sampling and sample handling technique cannot be over- emphasized. Nothing should be placed inside the well casing that has not been decontaminated and decontaminated equipment should never be handled without the use of new clean disposable gloves. Once the well cap is removed from the casing all equipment and all sampling procedures should be performed while wearing gloves. Extreme care should always be taken to prevent bailers, bailing line, and open sample containers from coming in contact with anything other than the well contents. Each monitoring well should be treated as a separate entity. All disposable equipment, such as gloves and bailer line, should be discarded after being used at each well. Never use the same equipment between wells unless it has been properly decontaminated. Each sampling episode should have enough laboratory cleaned supplies available for one-time use for each well. 1. Purging Methods The primary purpose of purging a monitoring well is to remove stagnant water within the casing and surrounding filter pack, thereby helping insure that the sample collected will closely represent actual ground water in the vicinity of the well. The accepted standard is to purge 3 to 5 well volumes or until the well is dry once before sampling. Purging may need to be continued beyond 3 to 5 well volumes if the pH and specific conductivity have not stabilized. At no time should purge rates cause cascading of recharge water inside the casing because of the possibility of increased loss of volatile compounds. In some instances, dependent upon the hydrogeologic setting, the recharge rate may be exceptionally slow after purging and sampling may not be possible until the next day. However, efforts should be made to sample all wells within 24 hours after purging. As a rule, the water level in all wells is measured and standing volumes are calculated before any well purging begins. The most accurate method of determining water level is with the use of an electronic indicator. Measurements should always be recorded to the nearest 0.01 foot. The use of carpenter's measuring tapes, monofilament lines, lead pipe "plopers", etc. is not recommended. Water level indicator cables and probes should always be decontaminated before and between well usage, and stored and transported in such a manner as to prevent contamination from outside sources. 2. Sample Containers Because samples are analyzed for various parameters, several types of containers are required for a complete sampling scheme. All sample containers must be properly decontaminated before use. The number of containers for sample collection and the use of acid for preservation of samples is dependent upon the protocol required by the laboratory performing the analyses. As a rule, samples for organics analyses are collected in glass containers, and samples for metals analyses are collected in plastic containers. If containers have a pre-measured amount of acid, no rinsing should be done prior to the addition of the sample. 3. Sampling Order Samples should always be collected in the order of parameter volatilization sensitivity. A preferred collection order for some parameters is as follows: * Volatile Organic Compounds (VOCs) * Total Organic Halogens (TOX) * Total Organic Carbon (TOC) * Extractable Organic Compounds (Semi-volatiles) * Total Metals * Cations and Anions 4. Field Filtering of Samples EPA regulations for analyses of samples from RCRA based programs require an analysis for total analyte concentrations. As a result, field filtration of monitoring samples to be evaluated for compliance purposes is not allowed. The 3030C preparation method required by the Division of Environmental Management is not allowed for solid waste management facilities. 5. Transport and Storage of Samples Upon completion of sample collection, all samples should be stored and transported on ice or in a refrigerated state to the laboratory performing the analyses. Samples should be stored in such a manner as to prohibit breakage or accidental spillage. Unless unusual circumstances prevent otherwise, all samples should be delivered to the laboratory on the same day as collected. 6. Administrative Procedures A chain-of-custody record should be completed and accompany each sample to the laboratory. The record should contain the following information: * Sample number * Signature of collector * Date and time of collection * Sample type * Well identification * Total number of containers * Signature of person(s) involved in chain-of-possession * Inclusive dates of possession 7. Quality Assurance/Quality Control All sampling events should include provisions for quality assurance and quality control to help insure the reliability and validity of the sampling data. At a minimum, one trip blank and one equipment blank must be included for each sampling episode. Analytical Procedures 1. Detection Monitoring Requirements The detection monitoring program for each Municipal Solid Waste Landfill (MSWLF) receiving solid waste after April 9, 1994 is required to comply with Solid Waste Management Rules 15A NCAC 13B .1630 through .1633. Generally, all monitoring well and surface water samples should be analyzed for the constituents listed in Appendix I of CFR Part 258 (Table 1). After the initial 4 independent sampling events to establish background water quality, sampling should be on a semi-annual basis unless otherwise specified by the Solid Waste Section. Field measurements for temperature, pH, specific conductivity, and the determination of rate and direction of ground water flow must also be included for each well at each sampling event. All analytical monitoring well data from the above referenced landfills must be evaluated statistically for compliance purposes. Surface water data does not have to be statistically analyzed. Acceptable statistical methods are listed under Rule .1632(g) of the North Carolina Solid Waste Management Rules 15A NCAC 13B. Construction and Demolition (C&D) Landfills are also required to be monitored semi-annually. At a minimum C&D landfill monitoring should be done for RCRA metals and volatile organic compounds (EPA Method 8240 or 8260), specific conductance, pH, and temperature. Determination of ground water flow rate and direction is not required during each sampling episode of C&D landfills. Landfills that stopped receiving solid waste before April 9, 1994 or landfills that do not have to comply with the Subtitle D monitoring requirements should sample and analyze for the parameters listed in Tables 1 and 2, unless otherwise directed by the Solid Waste Section. A statistical analysis of the monitoring well data is not required. Monitoring data, quality assurance/quality control data, statistical analyses, chain of custody records and any other required information should be submitted to the Solid Waste Section within 15 days of receipt by the facility owner/operator. 2. Laboratory Certification All monitoring samples should be analyzed by a laboratory certified under the Division of Environmental Management (DEM) Certification program. Tables 1 and 2 list lab certification requirements, sampling analytical methods, reporting limits and methodologies for analyses for the various sample parameters. C. Surface Water Monitoring Landfill sites which contain or border small rivers, streams or branches should include surface water sampling as part of the detection monitoring program for each sampling event. A simple procedure for selecting surface water monitoring sites is to locate a point on a stream where drainage leaves the site. This provides detection of contamination through, and possibly downstream, of site via discharge of surface waters. The sampling points selected should be downstream from any waste areas. An upstream sample should be obtained in order to determine water quality upstream of the influence of the landfill. The following procedure is recommended regarding sample collection of surface waters. Prior to collecting the sample, specific collection points should be determined. Samples should be collected in areas with minimal turbulence and aeration. Because sample containers may be dipped by hand into the stream, caution must be taken in avoiding contamination of the mouth of the container. The following procedure is recommended: 1. Hold the container near the base with one hand, and with he other hand remove the cap. 2. Rinse the sample container with the water to be sampled prior to filling the container unless it has a pre-measured amount of preservatives such as acid for metals samples. 3. Push the sample container rapidly into the water (mouth down) and tilt upwards toward the current to fill. A depth of about 6 inches is satisfactory. Do not breach the water surface while filling the container. 4. During times of little current flow, move the container laterally slowly through the water. 5. During times of drought when stream water depths are too shallow to allow submersion of the container, a pool may be scooped out of the channel bottom and allowed to clear prior to sampling. 6. Lift the container from the water and leave one-half inch of air space and place the cap on the container. Volatile organic samples should have no head space. 7. Place the samples on ice and transport to the laboratory with completed paperwork. Summary of Important Sampling Requirements 1. Monitoring requirements for MSWLF units must comply with Solid Waste Management Rules 15A NCAC 13B .1630 through .1633. 2. All monitoring wells that are part of the detection monitoring system must be sampled semi-annually unless otherwise specified by the Solid Waste Section. 3. All sampling equipment should be properly decontaminated before use according to EPA Region IV protocol. Once equipment has been cleaned it should be protected from contamination. This includes bailers, bailer line, water level indicator cable and probe. Equipment should not be transported unprotected from possible contamination sources. 4. Field cleaning of bailers and most other equipment is not allowed. A sufficient number of laboratory cleaned bailers should be available to provide a separate bailer for each monitoring well for a sampling episode. Water level indicator cable and probe should be cleaned and protected from contamination after usage between each well. When taking measurements at more than one well during a sampling event, a minimum cleaning for water level indicator probes and cables should be a thorough rinse with distilled or deionized water. 5. Always use clean disposable gloves when sampling or handling any sampling equipment. Frequent glove changes will lesson the possibility of cross-contamination between wells and equipment. 6. If bailers are used to sample monitoring wells, only bailers composed of Teflon or stainless steel are allowed. If disposable Teflon bailers are used, documentation of proper cleaning protocol must be provided. HDPE and PVC bailers may not be used. 7. Wells should be purged a minimum of 3 well volumes or to dryness at least once before being sampled. 8. If a well is not immediately sampled after purging and bailers are used as the sampling device, the bailer and line may be secured and temporarily stored inside the well casing above the water level until the well is sampled. However the well should be sampled as soon as recharge is sufficient. 9. Monitoring well samples should be collected in the following order: a. Volatile organics b. Semi-volatile organics c. Metals d. Cations and anions (ie. chlorides, sulfates, etc.) e. Indicator parameters (ie. BOD, COD, etc.) f. Other parameters (ie. TDS, etc.) 10. If pumps are used for sampling, flow rates should not exceed 100 ml/min. 11. Field filtration of ground water samples used for compliance monitoring is not permitted. Samples must be analyzed for total concentrations of all parameters unless otherwise specified by the Solid Waste Section. 12. QA/QC samples should be a part of each sampling episode. 13. Chain-of-Custody must be maintained for all samples. 14. Samples must be analyzed by laboratories meeting DEM certification requirements for each parameter using the methods approved by the Solid Waste Section.