General Groundwater Monitoring Requirements

The owner or operator shall comply with the following requirements for any groundwater monitoring program developed to comply with the requirements of 310 CMR 30.664, 30.671, or 30.672: (1) The groundwater monitoring system shall consist of a sufficient number of wells, installed at appropriate locations and depths, to yield from the uppermost aquifer groundwater samples that: (a) Represent the quality of background groundwater that has not been affected by leakage from a regulated unit. A determination of background quality may include sampling of wells that are not hydraulically upgradient of the waste management area where: 1. Hydrogeologic conditions do not allow the owner or operator to determine what wells are hydraulically upgradient; and 2. Sampling at other wells will provide an indication of background ground-water quality that is representative or more representative than that provided by upgradient wells; and (b) Represent the quality of groundwater passing a point of compliance; and (c) Allow for the detection of contamination when hazardous waste or hazardous constituents have migrated from the waste management area to the uppermost aquifer. (2) If a facility contains more than one regulated unit, separate groundwater monitoring systems shall not be required for each regulated unit if sampling of groundwater in the uppermost aquifer at a compliance point will enable detection and measurement of hazardous constituents from the regulated units. (3) All monitoring wells shall be cased in a manner that maintains the integrity of the monitoring well bore hole. To enable collection of groundwater samples, this casing shall be screened or perforated and, where necessary, packed with gravel or sand. The annular space (i.e., the space between the bore hole and well casing) above and below the sampling depth shall be sealed to prevent contamination of samples and of the groundwater. (a) The inside diameter shall be sized to facilitate the collection of samples. (b) The casing shall be constructed of a material which will not be reactive with or corroded by any leachate from any regulated unit. (c) PVC casing shall be joined in a manner which does not contribute organics to water samples. (d) The casing shall be screened or perforated in a manner that allows water to enter the well freely at low velocity, prevents sand from entering the well, and serves as the structural retainer to support loose formation material. (e) All monitoring wells shall be protected by a length of protective casing which is larger in diameter than the monitoring well casing and which extends below the land surface. 1. The protective casing shall be grouted and placed with a protective collar to hold it firmly in position. 2. The protective casing shall be identified by a highly visible color. 3. The protective casing shall be higher above grade than the inner well casing. 4. The protective casing shall have a vented cap that will allow the well to be secured against acts of vandalism. (f) All borings for monitoring wells shall be done by a technique that enables the well driller to obtain representative soil samples at five-foot intervals. 1. The soil samples shall be placed in covered glass jars and labelled so that a stratigraphic log can be prepared. 2. Sample jars containing soil samples shall be placed in the custody of the facility owner or operator after examination by an engineer or geologist, and shall be available for inspection by the Department. 3. When well clusters are used, soil sampling is onlynecessaryat the deepest boring and at other borings at the screened depth. (g) As technology changes in the field of groundwater monitoring, the Department may approve, in writing, different but equivalent or better methods for obtaining the information required to prepare a stratigraphic log, take water level measurements, or obtain representative groundwater samples. (4) The groundwater monitoring program shall include consistent sampling and analysis procedures that are designed to ensure monitoring results that provide a reliable indication of groundwater quality below the waste management area, as described in 310 CMR 30.669(2). At a minimum, the program shall include procedures and techniques for: (a) Sample collection; (b) Sample preservation, storage and shipment; (c) Analytical procedures, including quality control and assurance techniques; and (d) Chain-of-custody control. (5) The groundwater monitoring program shall include sampling and analytical methods that are appropriate for groundwater sampling and that accurately measure hazardous constituents in groundwater samples. (6) The groundwater monitoring program shall include a determination of the groundwater surface elevation each time groundwater is sampled. These data shall be plotted to make a map showing water table contours and presumed flow directions. Care shall be taken in preparing this map to consider the portions of the aquifer screened by each of the wells. All measurements shall be referenced to sea level, based on USGS or USC&GS data. By April 30th of each year, the owner or operator shall evaluate the data on groundwater elevations obtained in compliance with 310 CMR 30.663(6) to determine whether the requirements set forth in 310 CMR 30.663(1) for well locations continue to be met. If any such requirement is not met, the owner or operator shall: (a) Within ten days, notify the Department of this fact, and request, in writing, a license modification; and (b) Within a period of time specified by the Department, locate and install new wells to meet the requirements of 310 CMR 30.663(1). (7) In detection monitoring or where appropriate in compliance monitoring, data on each hazardous constituent specified in the license shall be collected from background wells and wells at compliance point(s). The number and kinds of samples collected to establish background shall be appropriate for the form of statistical test employed, following generally accepted statistical principles. The sample size shall be as large as necessary to ensure with reasonable confidence that a contaminant release to ground water from a facility will be detected. The owner or operator shall determine an appropriate sampling procedure and interval for each hazardous constituent listed in the facility license which shall be specified in the unit license upon approval by the Department. This sampling procedure shall be: (a) A sequence of at least four samples, taken at an interval that assures, to the greatest extent technically feasible, that an independent sample is obtained, by reference to the uppermost aquifer's effective porosity, hydraulic conductivity, and hydraulic gradient, and the fate and transport characteristics of the potential contaminants, or (b) An alternate sampling procedure proposed by the owner or operator and approved by the Department. (8) The owner or operator shall specify one of the following statistical methods to be used in evaluating ground-water monitoring data for each hazardous waste constituent which, upon approval by the Department, shall be specified in the unit license. The statistical test chosen shall be conducted separately for each hazardous constituent in each well. Where practical quantification limits (pql's) are used in any of the following statistical procedures to comply with 310 CMR 30.663(10)(e), the pql shall be proposed by the owner or operator and approved by the Department. Use of any of the following statistical methods shall be protective of public health, safety and welfare and the environment and shall comply with the performance standards outlined in 310 CMR 30.663(10). (a) A parametric analysis of variance (ANOVA) followed by multiple comparisons procedures to identify statistically significant evidence of contamination. The method shall include estimation and testing of the contrasts between each compliance well's mean and the background mean levels for each constituent. (b) An analysis of variance (ANOVA) based on ranks followed by multiple comparison procedures to identify statistically significant evidence of contamination. The method shall include estimation and testing of the contrasts between each compliance well's median and the background median levels for each constituent. (c) A tolerance or prediction interval procedure in which an interval for each constituent is established from the distribution of the background data, and the level of each constituent in each compliance well is compared to the upper tolerance or prediction limit. (d) A control chart approach that gives control limits for each constituent. (e) Another statistical test method submitted by the owner or operator and approved by the Department. (9) In addition to using a statistical test to determine whether background values or concentration limits have been exceeded, each owner or operator conducting a groundwater monitoring program shall compile the information for each water quality parameter at each sampling point in the form of a table covering the current year and on a graph showing the historical trend. This information shall be submitted to the Department annually by March 1 of each year. (10) Any statistical method chosen pursuant to 310 CMR 30.663(8) for specification in the unit license shall comply with the following performance standards, as appropriate: (a) The statistical method used to evaluate ground-water monitoring data shall be appropriate for the distribution of chemical parameters or hazardous constituents. If the distribution of the chemical parameters or hazardous constituents is shown by the owner or operator to be inappropriate for a normal theory test, then the data shall be transformed or a distribution-free theory test shall be used. If the distributions for the constituents differ more than one statistical method may be needed. (b) If an individual well comparison procedure is used to compare an individual compliance well constituent concentration with background constituent concentrations or a ground-water protection standard, the test shall be done at a Type I error level no less than 0.01 for each testing period. If a multiple comparison procedure is used, the Type I experimentwise error rate for each testing period shall be no less than 0.05; however, the Type I error of no less than 0.01 for individual well comparisons shall be maintained. This performance standard does not apply to tolerance intervals, prediction intervals or control charts. (c) If a control chart approach is used to evaluate ground-water monitoring data, the specific type of control chart and its associated parameter values shall be proposed by the owner or operator and approved by the Department if the Department finds it to be protective of public health, safety and welfare and the environment. (d) If a tolerance interval or a prediction interval is used to evaluate groundwater monitoring data, the levels of confidence and, for tolerance intervals, the percentage of the population that the interval shall contain, shall be proposed by the owner or operator and approved by the Department if the Department finds these parameters to be protective of public health, safety and welfare and the environment. These parameters will be determined after considering the number of samples in the background data base, the data distribution, and the range of the concentration values for each constituent of concern. (e) The statistical method shall account for data below the limit of detection with one or more statistical procedures that are protective of public health, safety and welfare and the environment. Any practical quantification limit (pql) approved by the Department pursuant to 310 CMR 30.663(8) that is used in the statistical method shall be the lowest concentration level that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operating conditions that are available to the facility. (f) If necessary, the statistical method shall include procedures to control or correct for seasonal and spatial variability as well as temporal correlation in the data. (11) Ground-water monitoringdatacollected in accordance with 310 CMR 30.663(7), including actual levels of constituents shall be maintained in the facility operating record. The Department will specify in the license when the data shall be submitted for review.