9 Va. Admin. Code § 20-81-250 - Groundwater monitoring program

A. General requirements.

1. Applicability.

a. Existing landfills. Owners or operators of all existing landfills shall be in compliance with the groundwater monitoring requirements specified in this section, except as provided for in subdivision 1 c of this subsection. Owners or operators of landfills that were permitted prior to December 21, 1988, but were closed in accordance with the requirements of their permit or existing regulation prior to December 21, 1988, are not required to be in compliance with the groundwater monitoring requirements specified in this section, unless conditions are recognized that classify the landfill as an Open Dump as defined under 9VAC20-81-45.

b. New landfills. Owners or operators of new facilities shall be in compliance with the groundwater monitoring requirements specified in this section before waste can be placed in the landfill except as provided for in subdivision 1 c of this subsection.

c. No migration potential exemption. Groundwater monitoring requirements under this section may be suspended by the director if the owner or operator can demonstrate that there is no potential for migration of any Table 3.1 constituents to the uppermost aquifer during the active life and the postclosure care period of the landfill. This demonstration shall be certified by a qualified groundwater scientist and shall be based upon:

(1) Site-specific field collected measurements including sampling and analysis of physical, chemical, and biological processes affecting contaminant fate and transport; and

(2) Contaminant fate and transport predictions that maximize contaminant migration and consider impacts on human health and the environment.

2. General requirements.

a. Purpose. Owners or operators shall install, operate, and maintain a groundwater monitoring system that is capable of determining the landfill's impact on the quality of groundwater in the uppermost aquifer at the disposal unit boundary during the active life and postclosure care period of the landfill.

b. Program requirements. The groundwater monitoring program shall meet the requirements of subdivision 3 of this subsection and comply with all other applicable requirements of this section.

c. Director authority. The groundwater monitoring and reporting requirements set forth here are minimum requirements. The director may require, by modifying the permit as allowed under 9VAC20-81-600 E, any owner or operator to install, operate, and maintain a groundwater monitoring system and conduct a monitoring program that contains requirements more stringent than this chapter imposes whenever it is determined that such requirements are necessary to protect human health and the environment.

3. Groundwater monitoring system.

a. System requirements. A groundwater monitoring system shall be installed consisting of a sufficient number of monitoring wells, at appropriate locations and depths, capable of yielding sufficient quantities of groundwater for sampling and analysis purposes from the uppermost aquifer that:

(1) Represent the quality of background groundwater that has not been affected by a release from the landfill; and

(2) Represent the quality of groundwater at the disposal unit boundary. The downgradient monitoring system shall be installed at the disposal unit boundary in a manner that ensures detection of groundwater contamination in the uppermost aquifer unless a variance has been granted by the director under 9VAC20-81-740.

(3) When physical obstacles preclude installation of groundwater monitoring wells at the disposal unit boundary, the downgradient monitoring wells may be installed at the closest practicable distance hydraulically downgradient from the boundary in locations that ensure detection of groundwater contamination in the uppermost aquifer.

b. Multiunit systems. The director may approve a groundwater monitoring system that covers multiple waste disposal units instead of requiring separate groundwater monitoring systems for each unit when the landfill has several units, provided the multiunit groundwater monitoring system meets the requirement of subdivision 3 of this subsection and can be demonstrated to be equally protective of human health and the environment as individual monitoring systems. The system for each waste disposal unit would be based on the following factors:

(1) Number, spacing, and orientation of the waste disposal units;

(2) Hydrogeologic setting;

(3) Site history;

(4) Engineering design of the waste disposal units; and

(5) Type of waste accepted at the waste disposal units.

c. Well construction. All monitoring wells shall be of a size adequate for sampling and shall be cased and grouted in a manner that maintains the integrity of the monitoring well bore hole. This casing shall be screened or perforated, and packed with gravel or sand where necessary, to enable sample collection at depths where appropriate aquifer flow zones exist. The annular space above the sampling depth shall be sealed with a suitable material to prevent contamination of samples and the groundwater.

d. Boring logs. A log shall be made of each newly installed monitoring well describing the soils or rock encountered, and the hydraulic conductivity of the geologic units (formations) encountered. A copy of the final log(s) with appropriate maps, including at a minimum a site plan showing the location of all monitoring wells, the total depth of monitoring well, the location of the screened interval, the top and bottom of sand or gravel pack, and the top and bottom of the seal shall be sent to the department with the certification required under subdivision 3 g of this subsection.

e. Well maintenance. The monitoring wells, piezometers, and other groundwater measurement, sampling, and analytical devices shall be operated and maintained in a manner that allows them to perform to design specifications throughout the duration of the groundwater monitoring program. Nonfunctioning monitoring wells must be replaced or repaired upon recognition of damage or nonperformance. Well repair or replacement shall be coordinated with the department prior to initiating the action.

f. Network specifics. The network shall include at least one upgradient monitoring well and at least three downgradient monitoring wells. The number, spacing, and depths of monitoring wells included in a landfill's network shall be determined based on:

(1) Site-specific technical information that shall include thorough characterization by the owner or operator of:

(a) The thickness of any unsaturated geologic units or fill materials that may overlay the uppermost aquifer;

(b) The thickness and description of materials comprising the uppermost aquifer;

(c) Materials comprising the confining unit defining the lower boundary of the uppermost aquifer, including, but not limited to, thicknesses, stratigraphy, lithology, hydraulic conductivities, porosities, and effective porosities; and

(d) the calculated groundwater flow rate and direction within the uppermost aquifer including any seasonal and temporal fluctuations in groundwater flow.

(2) The lateral spacing between downgradient monitoring wells based on site-specific information supplied under subdivision 3 f (1) of this subsection.

g. Monitoring well certification. The groundwater monitoring well(s) shall, within 30 days of well(s) installation, be certified by a qualified groundwater scientist noting that all wells have been installed in accordance with the documentation submitted under subdivision 3 d of this subsection. Within 14 days of completing this certification, the owner or operator shall transmit the certification to the department.

4. The groundwater sampling and analysis requirements for the groundwater monitoring system are as follows:

a. Quality assurance and control. The groundwater monitoring program shall include consistent field sampling and laboratory analysis procedures that are designed to ensure monitoring results that provide an accurate representation of the groundwater quality at the background and downgradient wells. At a minimum the program shall include procedures and techniques for:

(1) Sample collection;

(2) Sample preservation and shipment;

(3) Analytical procedures;

(4) Chain of custody control; and

(5) Quality assurance and quality control.

b. Analytical methods. The groundwater monitoring program shall include sampling and analytical methods that are appropriate for groundwater sampling and that accurately measure solid waste constituents in groundwater samples. Groundwater samples obtained pursuant to 9VAC20-81-250 B or C shall not be filtered prior to laboratory analysis. The sampling, analysis and quality control/quality assurance methods set forth in EPA document SW-846, as amended, shall be used. The department may require re-sampling if it believes the samples were not properly sampled or analyzed.

c. Groundwater rate and flow. Groundwater elevations at each monitoring well shall be determined immediately prior to purging each time a sample is obtained. The owner or operator shall determine the rate and direction of groundwater flow each time groundwater is sampled pursuant to subsection B or C of this section or 9VAC20-81-260. Groundwater elevations in wells that monitor the same waste disposal unit or units shall be measured within a period of time short enough to avoid temporal variations, which could preclude accurate determination of groundwater flow rate and direction.

d. Background data. The owner or operator shall establish background groundwater quality in a hydraulically upgradient or background well, or wells, for each of the monitoring parameters or constituents required in the particular groundwater monitoring program that applies to the landfill. Background groundwater quality may be established at wells that are not located hydraulically upgradient from the landfill if they meet the requirements of subdivision 4 e of this subsection.

e. Alternate well provision. A determination of background quality may be based on sampling of wells that are not upgradient from the waste disposal unit or units where:

(1) Hydrogeologic conditions do not allow the owner or operator to determine what wells are upgradient; and

(2) Sampling at these wells will provide an indication of background groundwater quality that is as representative or more representative than that provided by the upgradient wells.

f. Sampling and statistics. The number of samples collected to establish groundwater quality data shall be consistent with the appropriate statistical procedures determined pursuant to subdivision 4 g of this subsection.

g. Statistical methods. The owner or operator shall specify in the Groundwater Monitoring Plan the statistical method(s) listed in subsection D of this section that will be used in evaluating groundwater monitoring data for each monitoring constituent. The statistical test(s) chosen shall be applied separately for each groundwater constituent in each well after each individual sampling event required under subdivision B 2 or 3, C 2 or 3, or as required under 9VAC20-81-260 E 1.

h. Evaluation and response. After each sampling event required under subsection B or C of this section, the owner or operator shall determine whether or not there is a statistically significant increase over background values for each groundwater constituent required in the particular groundwater monitoring program by comparing the groundwater quality of each constituent at each monitoring well installed pursuant to subdivision 3 a of this subsection to the background value of that constituent. In determining whether a statistically significant increase has occurred, the owner or operator shall:

(1) Ensure the sampling result comparisons are made according to the statistical procedures and performance standards specified in subsection D of this section;

(2) Ensure that within 30 days of completion of sampling and laboratory analysis actions, the determination of whether there has been a statistically significant increase over background at each monitoring well has been completed; and

(3) If identified, the statistically significant increase shall be reported to the department within the notification timeframes identified in subsection B or C of this section and discussed in the quarterly or semi-annual report submission described under subdivision E 2 c of this section. Notifications qualified as being "preliminary," "suspect," "unverified," or otherwise not a final determination of a statistical exceedance will not be accepted.

i. Verification sampling. The owner or operator may at any time within the 30-day statistically significant increases determination period defined under subdivision A 4 h (2) of this section, obtain verification samples if the initial review of analytical data suggests results that might not be an accurate reflection of groundwater quality at the disposal unit boundary. Undertaking verification sampling is a voluntary action on the part of the owner or operator and shall not alter the timeframes associated with determining or reporting a statistically significant increase as otherwise defined under subdivision A 4 h (2), B 2 or 3, or C 2 or 3 of this section.

j. Data validation. The owner or operator may at any time within the 30-day statistically significant increases determination period defined under subdivision A 4 h (2) of this subsection, undertake third-party data validation of the analytical data received from the laboratory. Undertaking such validation efforts is a voluntary action on the part of the owner or operator and shall not alter the timeframes associated with determining or reporting a statistically significant increase as otherwise defined under subdivision A 4 h (2), B 2 or 3, or C 2 or 3 of this section.

5. Alternate source demonstration allowance.

a. Allowance. As a result of any statistically significant increase identified while monitoring groundwater under subdivision B 2 or 3, or C 2 or 3 of this section, or at anytime within the Corrective Action process under 9VAC20-81-260, the owner or operator has the option of submitting an Alternate Source Demonstration report, certified by a qualified groundwater scientist, demonstrating:

(1) A source other than the landfill caused the statistical exceedance;

(2) The exceedance resulted from error in sampling, analysis, or evaluation; or

(3) The exceedance resulted from a natural variation in groundwater quality.

b. Timeframes. A successful demonstration must be made within 90 days of noting a statistically significant increase. The director may approve a longer timeframe for submittal and approval of the Alternate Source Demonstration with appropriate justification.

c. Evaluation and response. Based on the information submitted in accordance with subdivision 5 a of this subsection, the director will:

(1) In the case of the successful demonstration of an error in sampling, analysis, or evaluation, allow the owner or operator to continue monitoring groundwater in accordance with the monitoring program in place at the time of the statistical exceedance.

(2) In the case of a successful demonstration of an alternate source for the release or natural variability in the aquifer matrix:

(a) Require changes in the groundwater monitoring system as needed to accurately reflect the groundwater conditions and allow the owner or operator to continue monitoring groundwater in accordance with the monitoring program in place at the time of the statistical exceedance;

(b) Require any changes to the monitoring system be completed prior to the next regularly scheduled groundwater monitoring event or within 90 days (whichever is greater); and

(c) Require any changes to the monitoring system be approved via the modification process under 9VAC20-81-600 within 90 days of the approval of the alternate source demonstration.

(3) In the case of an unsuccessful Alternate Source Demonstration, require the owner or operator to initiate the actions that would otherwise be required as a result of the statistically significant increase noted under subdivision B 2 or 3, or C 2 or 3 of this section as appropriate.

6. Establishment of groundwater protection standards.

a. Requirement. Upon recognition of a statistically significant increase over background and while monitoring in the Assessment or Phase II monitoring programs defined under subdivision B 3 or C 3 of this section, the owner or operator shall propose a groundwater protection standard for all detected Table 3.1 Column B constituents. The proposed standards shall be submitted to the department by a qualified groundwater scientist and be accompanied by relevant historical groundwater sampling data to justify the proposed concentration levels.

b. Establishment process. The groundwater protection standards shall be established in the following manner:

(1) For constituents for which a maximum contaminant level (MCL) has been promulgated under § 1412 of the Safe Drinking Water Act (40 CFR Part 141), the MCL for that constituent shall be automatically established as the groundwater protection standard upon submission of the proposed standards.

(2) If the owner or operator determines that a site-specific background concentration is greater than the MCL associated with that constituent under subdivision 6 b (1) of this subsection, the background value may be substituted for use as the groundwater protection standard in lieu of the MCL for that constituent upon receiving written department approval.

(3) For constituents for which no MCL has been promulgated, site-specific background concentration value(s) may be used upon receiving written department approval.

(4) For constituents for which no MCL has been promulgated, a risk-based alternate concentration levels may be used if approved by the director as long as:

(a) The owner or operator submits a request to the department asking for approval to use risk-based alternate concentration levels for a specific list of constituents and identifies that these constituents lack an MCL. In the request the owner or operator shall specify whether site-specific, independently calculated, risk-based alternate concentration levels will be applied, or if the facility will accept the default department-provided limits.

(b) The alternate concentration levels that may be provided as default values by the department and those independently calculated by the owner or operator are demonstrated to meet the following criteria or factors before they can be used as groundwater protection standards:

(i) Groundwater quality - The potential for adverse quality effects considering the physical and chemical characteristics of the waste in the landfill, its potential for migration in the aquifer; the hydrogeological characteristics of the facility and surrounding land; the rate and direction of groundwater flow; the proximity and withdrawal rates of groundwater users; the current and future uses of groundwater in the area; the existing quality of groundwater, including other sources of contamination and their cumulative impact on the groundwater quality.

(ii) Human exposure - Potential for health risks caused by exposure to waste constituents released from the landfill using federal guidelines for assessing the health risks of environmental pollutants; scientifically valid studies conducted in accordance with the Toxic Substances Control Act Good Laboratory Practice Standards (40 CFR Part 792); or equivalent standards. For carcinogens, the alternate concentration levels must be set based on a lifetime cancer risk level due to continuous lifetime exposure within the 1x10^-4 to 1x10^-6 range. For systemic toxicants, alternate concentration levels must be demonstrated to be levels to which the human population (including sensitive subgroups) could be exposed to on a daily basis without the likelihood of appreciable risk of deleterious effects during a lifetime.

(iii) Surface water - The potential adverse effect on hydraulically connected surface water quality based on the volume, physical and chemical characteristics of the waste in the landfill; the hydrogeological characteristics of the facility and surrounding land; the rate and direction of groundwater flow; the patterns of rainfall in the region; the proximity of the landfill to surface waters; the current and future uses of surface waters in the area and any water quality standards established for those surface waters; the existing quality of surface water, including other sources of contamination and the cumulative impact on surface water quality.

(iv) Other adverse effects - Potential damage to wildlife, crops, vegetation, and physical structures caused by exposure to waste constituents; the persistence and permanence of the potential adverse effects; and the potential for health risks caused by human exposure to waste constituents using factors shown in subdivision b (4) (b) (ii) of this subsection.

(5) In making any determination regarding the use of alternate concentration levels under this section, the director will:

(a) Consider any identification of underground sources of drinking water as identified by EPA under 40 CFR 144.7,

(b) Consider additional or modified monitoring requirements or control measures,

(c) Include a schedule for the periodic review of the alternate concentration levels, or

(d) Approve the alternate concentration levels as proposed or issue modified alternate concentration levels.

c. Implementation. Groundwater protection standards shall be considered established for the facility upon completion of the actions described under either subdivision A 6 b (1), (2), (3) or if necessary (4) and shall be placed in the facility Operating Record and shall be used during subsequent comparisons of groundwater sampling data consistent with the requirements of subdivision B 3 f or C 3 e of this section.

d. MCL and background revisions. After establishment of groundwater protection standards under subdivision B 6 b, if the standards are modified as a result of revisions to any MCL or department-approved background, the facility shall update its listing of groundwater protection standards and shall place the new list in the Operating Record and shall use the new values during subsequent comparisons of sampling data consistent with the requirements of subdivision B 3 f or C 3 e of this section.

e. Alternate concentration levels revisions. After establishment of groundwater protection standards under subdivision B 6 b of this section, if the department-approved alternate concentration levels change based on information released by EPA, to the extent practical, the department will issue revisions to the alternate concentration levels for facility use no more often than an annual basis. The facility shall use the alternate concentration levels listing in effect at the time the sampling event takes place when comparing the results against the groundwater protection standards under subdivision B 3 f or C 3 e of this section.

B. Monitoring for sanitary landfills.

1. Applicability.

a. Existing facilities. Except for those sanitary landfills identified in subdivision C 1 of this section, existing sanitary landfill facilities and closed facilities that have accepted waste on or after October 9, 1993, and in the case of 'small' landfills on or after April 9, 1994, shall be in compliance with the detection monitoring requirements specified in subdivision 2 of this subsection unless existing sampling data requires a move to assessment monitoring described under subdivision 3 of this subsection.

b. New facilities. Facilities placed in operation to receive waste after October 9, 1993, shall be in compliance with the detection monitoring requirements specified in subdivision 2 of this section before waste can be placed in the landfill unless existing sampling data requires a move to assessment monitoring described under subdivision 3 of this subsection.

c. Closed facilities. Unless an extension to the deadline above has been granted by the director, closed facilities that have ceased to accept any waste on or before October 9, 1993, and in the case of a "small" landfill, before April 9, 1994, may comply with the "State Monitoring Program" monitoring requirements specified in subdivision C 2 or 3 of this section.

d. Other facilities. Owners or operators of disposal facilities not subject to the federal groundwater monitoring requirements prescribed under 40 CFR Parts 257 and 258 must perform the groundwater monitoring described in subdivision C 2 or 3 of this section.

e. Proximity to wetlands. Owners or operators of sanitary landfills that accepted waste after June 30, 1999, must:

(1) Perform quarterly groundwater monitoring unless the director determines that less frequent monitoring is necessary consistent with the requirements of the special provisions regarding wetlands in § 10.1-1408.5 of the Code of Virginia.

(2) The quarterly monitoring frequency shall remain in effect until the department is notified waste is no longer being accepted at the sanitary landfill.

(3) This requirement will not limit the authority of the Waste Management Board or the director to require more frequent groundwater monitoring if required to protect human health and the environment.

(4) For purposes of this subdivision "proximity to wetlands" shall be defined as landfills that were constructed on a wetland, have a potential hydrologic connection to such a wetland in the event of an escape of liquids from the facility, or are within a mile of such a wetland.

2. Detection monitoring program.

a. Sampling requirements. All sanitary landfills shall implement detection monitoring except as otherwise provided in subdivision 1 of this subsection. The monitoring frequency for all constituents listed in Table 3.1 Column A shall be as follows:

(1) Initial sampling period.

(a) For facilities that monitor groundwater on a semi-annual basis, a minimum of four independent samples from each well (background and downgradient) shall be collected and analyzed for the Table 3.1 Column A constituents during the first semi-annual sampling period. A semi-annual period is defined under 9VAC20-81-10.

(b) For facilities that monitor groundwater on a quarterly basis as a result of subdivision 1 e of this subsection, a minimum of four samples from each well (background and downgradient) shall be collected and analyzed for the Table 3.1 Column A constituents. The samples shall be collected within the first quarterly period, using a schedule that ensures, to the greatest extent possible, an accurate calculation of background concentrations.

(2) Subsequent sampling events. At least one sample from each well (background and downgradient) shall be collected and analyzed during subsequent semi-annual or quarterly events during the active life and postclosure period. Data from subsequent background sampling events may be added to the previously calculated background data so that the facility maintains the most accurate representation of background groundwater quality with which to carry out statistical analysis required under subdivision A 4 h of this section.

(3) Alternate sampling events. The director may specify an appropriate alternate frequency for repeated sampling and analysis during the active life (including closure) and the postclosure care period. The alternate frequency during the active life (including closure) and the postclosure period shall be no less than annual. The alternate frequency shall be based on consideration of the following factors:

(a) Lithology of the aquifer and unsaturated zone;

(b) Hydraulic conductivity of the aquifer and unsaturated zone;

(c) Groundwater flow rates;

(d) Minimum distance between upgradient edge of the disposal unit boundary and downgradient monitoring well screen (minimum distance of travel); and

(e) Resource value of the aquifer.

b. Evaluation and response. If the owner or operator determines under subdivision A 4 h of this section, that there is:

(1) A statistically significant increase over background as determined by a method meeting the requirements of subsection D of this section, for one or more of the constituents listed in Table 3.1 Column A at any of the monitoring wells at the disposal unit boundary during any detection monitoring sampling event, the owner or operator shall:

(a) Within 14 days of this finding, notify the department of this fact, indicating which constituents have shown statistically significant increases over background levels; and

(b) Within 90 days, (i) establish an assessment monitoring program meeting the requirements of subdivision 3 of this subsection, or (ii) submit an Alternate Source Demonstration as specified in subdivision A 5 of this section. If, after 90 days, a successful demonstration has not been made, the owner or operator shall initiate an assessment monitoring program as otherwise required in subdivision 3 of this subsection. The 90-day Alternate Source Demonstration period may be extended by the director for good cause.

(2) No statistically significant increase over background as determined by a method meeting the requirements of subsection D of this section, for any of the constituents listed in Table 3.1 Column A at any of the monitoring wells at the disposal unit boundary during any detection monitoring sampling event; the owner or operator may remain in detection monitoring and include a discussion of the sampling results and statistical analysis in the semi-annual or quarterly report required under subdivision E 2 c of this section.

3. Assessment monitoring program. The owner or operator shall implement the assessment monitoring program whenever a statistically significant increase over background has been detected during monitoring conducted under the detection monitoring program.

a. Sampling requirements. Within 90 days of recognizing a statistically significant increase over background for one or more of the constituents listed in Table 3.1 Column A, the owner or operator shall, unless in receipt of an approval to an Alternate Source Demonstration under subdivision A 5 of this section or a director-approved extension, conduct the initial assessment monitoring sampling event for the constituents found in Table 3.1 Column B. A minimum of one sample from each well installed under subdivision A 3 a of this section shall be collected and analyzed during the initial and all subsequent annual Table 3.1 Column B sampling events.

b. Director provisions:

(1) The owner or operator may request that the director approve an appropriate subset of monitoring wells that may remain in detection monitoring defined under subdivision 2 of this subsection, based on the results of the initial, or subsequent annual Table 3.1 Column B sampling events. Monitoring wells may be considered for the subset if:

(a) They show no detections of Table 3.1 Column B constituents other than those already previously detected in detection monitoring defined under subdivision 2 of this subsection; and

(b) They display no statistically significant increases over background for any constituents on the Table 3.1 Column A list. If an increase is subsequently recognized in a well approved for the subset, the well shall no longer be considered part of the detection monitoring subset.

(2) The owner or operator may request the director delete any of the Table 3.1 Column B monitoring constituents from the assessment monitoring program if the owner or operator demonstrates that the deleted constituents are not reasonably expected to be in or derived from the waste.

(3) The director may specify an appropriate alternate frequency for repeated sampling and analysis for the full set of Table 3.1 Column B constituents required by subdivision 3 a of this subsection during the active life and postclosure care period based on the consideration of the following factors:

(a) Lithology of the aquifer and unsaturated zone;

(b) Hydraulic conductivity of the aquifer and unsaturatedzone;

(c) Groundwater flow rates;

(d) Minimum distance between upgradient edge of the disposal unit boundary and downgradient monitoring well screen (minimum distance of travel);

(e) Resource value of the aquifer; and

(f) Nature (fate and transport) of any constituents detected in response to subdivision 3 f of this subsection.

c. Development of background. After obtaining the results from the initial or subsequent annual sampling events required in subdivision 3 a of this subsection, the owner or operator shall:

(1) Within 14 days, notify the department identifying the Table 3.1 Column B constituents that have been detected;

(2) Within 90 days, and on at least a semi-annual basis thereafter, resample all wells installed under subdivision A 3 a of this section, conduct analyses for all constituents in Table 3.1 Column A as well as those constituents in Column B that are detected in response to subdivision 3 a of this subsection and subsequent Table 3.1 Column B sampling events as may be required of this section, and report this data in the semi-annual or quarterly report defined under subdivision E 2 c of this section;

(3) Within 180 days of the initial sampling event, establish background concentrations for any Table 3.1 Column B constituents detected pursuant to subdivision B 3 a of this subsection. A minimum of four independent samples from each well (background and downgradient) shall be collected and analyzed to establish background for the detected constituents.

d. Establishment of groundwater protection standards. Within 30 days of establishing background under subdivision 3 c (3) of this subsection, submit proposed groundwater protection standards for all constituents detected under Assessment monitoring. The groundwater protection standards shall be approved by the director in accordance with the provisions of subdivision A 6 of this section.

e. Groundwater monitoring plan. No later than 60 days after approval of the groundwater protection standards in accordance with subdivision A 6 of this section, the owner or operator shall submit an updated Groundwater Monitoring Plan that details the site monitoring well network and sampling and analysis procedures undertaken during groundwater monitoring events. The owner or operator shall additionally:

(1) No later than 30 days after the submission of the Groundwater Monitoring Plan, request a permit modification to incorporate the plan and related groundwater monitoring modules into the landfill's permit in accordance with 9VAC20-81-600. The department may waive the requirement for a permit modification if the Groundwater Monitoring Plan included in the landfill's permit reflects current site conditions in accordance with the regulations.

(2) If the 30-day timeframe specified in subdivision 3 e (1) of this subsection is exceeded, the director will modify the permit in accordance with 9VAC20-81-600 E.

f. Evaluation and response.

(1) If the concentrations of all Table 3.1 Column B constituents are shown to be at or below background values, using the statistical procedures in subsection D of this section, for two consecutive Table 3.1 Column B sampling events, the owner or operator shall notify the director of this finding in the semi-annual or quarterly monitoring report and may return to detection monitoring defined under subdivision 2 of this subsection.

(2) If the concentrations of any Table 3.1 Column B constituents are found to be above background values, but below the groundwater protection standards established under subdivision A 6 of this section using the statistical procedures in subsection D of this section, the owner or operator shall continue in assessment monitoring in accordance with this section and present the findings to the department in the semi-annual or quarterly report.

(3) If one or more Table 3.1 Column B constituents are detected at statistically significant levels above the groundwater protection standard established under subdivision A 6 of this section using the statistical procedures in subsection D of this section, the owner or operator shall:

(a) Within 14 days of this finding, notify the department identifying the Table 3.1 Column B constituents that have exceeded the groundwater protection standard. The notification will include a statement that within 90 days the owner or operator will either:

(i) Undertake characterization and assessment actions required under 9VAC20-81-260 C 1; or

(ii) Submit an Alternate Source Demonstration as specified in subdivision A 5 of this section. If a successful demonstration is made within 90 days, the owner or operator may continue monitoring in accordance with the assessment monitoring program pursuant to subdivision 3 of this subsection. If the 90-day period passes without demonstration approval, the owner or operator shall comply with the actions under 9VAC20-81-260 C within the timeframes specified unless the director has granted an extension to those timeframes.

(b) Describe the results in the semi-annual or quarterly report.

C. Monitoring for CDD, industrial, and State Monitoring Program sanitary landfills.

1. Applicability.

a. Sanitary landfills. Owners or operators of sanitary disposal facilities that have ceased to accept solid waste prior to the federally imposed deadline of October 9, 1993, or in the case of a "small landfill" before April 9, 1994, are eligible, with the director's approval, to conduct the state groundwater monitoring program described in this section in lieu of the groundwater monitoring program required under subdivision B 2 or 3 of this section.

b. CDD and industrial landfills. Owners or operators of CDD and industrial landfills not subject to the federal groundwater monitoring requirements prescribed under 40 CFR Parts 257 and 258 shall perform the groundwater monitoring described in this section.

c. Other landfills. All other landfills excluding sanitary landfills, including those that accepted hazardous waste from very small quantity generators after July 1, 1998, shall perform the groundwater monitoring described in this section.

2. First determination monitoring program.

a. Sampling requirements. A first determination monitoring program shall consist of a background-establishing period followed by semi-annual sampling and analysis for the constituents shown in Table 3.1 Column A at all wells installed under subdivision A 3 a of this section. Within 14 days of each event during first determination monitoring, notify the department identifying the Table 3.1 Column A constituents that have been detected.

b. Development of background. Within 360 days of the initial first determination sampling event:

(1) Establish background concentrations for any constituents detected pursuant to subdivision 2 a of this subsection.

(a) A minimum of four independent samples from each well (background and downgradient) shall be collected and analyzed to establish background concentrations for the detected constituents using the procedures in subsection D of this section.

(b) In those cases where new wells are installed downgradient of waste disposal units that already have received waste, but these wells have not yet undergone their initial sampling event, collection of four independent samples for background development will not be required.

(2) Within 30 days of completing the background calculations required under subdivision 2 b (1) (a) of this subsection, submit a first determination report, signed by a qualified groundwater scientist, to the department which must include a summary of the background concentration data developed during the background sampling efforts as well as the statistical calculations for each constituent detected in the groundwater during the background sampling events.

c. Semi-annual sampling and analysis. Within 90 days of the last sampling event during the background-establishing period and at least semi-annually thereafter, sample each monitoring well in the compliance network for analysis of the constituents in Table 3.1 Column A.

d. Evaluation and response. Upon determination of site background under subdivision 2 b (1) (a) of this subsection, the results of all subsequent first determination monitoring events shall be assessed as follows:

(1) If no Table 3.1 Column A constituents are found to have entered the groundwater at statistically significant levels over background, the owner or operator shall:

(a) Remain in first determination monitoring; and

(b) May request the director delete any Table 3.1 Column A constituents from the semi-annual sampling list if the owner or operator demonstrates that the proposed deleted constituents are not reasonably expected to be in or derived from the waste.

(2) If the owner or operator recognizes a statistically significant increase over background for any Table 3.1 Column A constituent, within 14 days of this finding, the owner or operator shall notify the department identifying the Table 3.1 Column A constituents that have exceeded background levels. The notification will include a statement that within 90 days the owner or operator shall:

(a) Initiate a Phase II sampling program; or

(b) Submit an Alternate Source Demonstration under subdivision A 5 of this section.

(3) If a successful demonstration is made and approved within the timeframes established under subdivision A 5 of this section, the owner or operator may remain in First Determination monitoring.

(4) If a successful demonstration is not made and approved within the timeframes established under subdivision A 5 of this section, the owner or operator shall initiate Phase II monitoring in accordance with the timeframes in subdivision C 3 of this section. The director may approve a longer timeframe with appropriate justification.

3. Phase II monitoring.

a. Sampling requirements. The owner or operator shall:

(1) Within 90 days of noting the exceedance over background determined under subdivision C 2 d of this section, sample the groundwater in all monitoring wells installed under subdivision A 3 a of this section for all Table 3.1 Column B constituents;

(2) After completing the initial Phase II sampling event, continue to sample and analyze groundwater on a semi-annual basis within the Phase II monitoring program;

b. Background development. If no additional Table 3.1 Column B constituents are detected other than those previously detected under Column A, which already have established their background levels, the owner or operator shall follow the requirements under subdivision 3 c of this subsection regarding groundwater protection standard establishment while continuing to sample for the Table 3.1 Column A list on a semi-annual basis. If one or more additional Table 3.1 Column B constituents are detected during the initial Phase II sampling event:

(1) Within 360 days, establish a background value for each additional detected Table 3.1 Column B constituent.

(2) Submit a Phase II Background report within 30 days of completing the background calculations including a summary of the background concentration data for each constituent detected in the groundwater during the Table 3.1 Column B background sampling events.

(3) If any detected Table 3.1 Column B constituent is subsequently not detected for a period of two years, the owner or operator may petition the director to delete the constituent from the list of detected Table 3.1 Column B constituents that must be sampled semi-annually.

c. Establishment of groundwater protection standards. No later than:

(1) Thirty days after submitting the Phase II Background report required under the provisions of subdivision 3 b (2) of this subsection, or within 30 days of obtaining the results from the initial Table 3.1 Column B sampling event indicating no further sampling for background determination is necessary, the owner or operator shall propose a groundwater protection standard for all detected Table 3.1 constituents.

(2) The groundwater protection standard proposed shall be established in a manner consistent with the provisions in subdivision A 6 of this section.

d. Groundwater monitoring plan. No later than 60 days after establishment of groundwater protection standards in accordance with subdivision A 6 of this section, the owner or operator shall submit an updated Groundwater Monitoring Plan that details the site monitoring well network and sampling and analysis procedures undertaken during groundwater monitoring events. The department may waive the requirement for an updated plan if the Groundwater Monitoring Plan included in the landfill's permit reflects current site conditions in accordance with the regulations.

(1) No later than 30 days after the submission of the Groundwater Monitoring Plan, the owner or operator shall request a permit modification to incorporate the updated plan and related groundwater monitoring modules into the landfill's permit in accordance with 9VAC20-81-600.

(2) If the 30-day timeframe specified in subdivision 3 d (1) of this subsection is exceeded, the director will modify the permit in accordance with 9VAC20-81-600 E.

e. Evaluation and response. After each subsequent Phase II monitoring event following establishment of groundwater protection standards, the concentration of Table 3.1 Column B constituents found in the groundwater at each monitoring well installed pursuant to subdivision A 3 a of this section will be evaluated against the groundwater protection standards. The evaluation will be presented to the department in a semi-annual Phase II report. The evaluation will be as follows:

(1) If all Table 3.1 constituents are shown to be at or below background values, using the statistical procedures in subsection D of this section, for two consecutive Table 3.1 Column B sampling events, the owner or operator shall notify the director of this finding in the semi-annual report and may return to first determination monitoring;

(2) If any Table 3.1 Column B constituents are found to be above background values, but are below the established groundwater protection standard using the statistical procedures in subsection D of this section, the owner or operator shall continue semi-annual Phase II monitoring and present the findings in a semi-annual report;

(3) If one or more Table 3.1 Column B constituents are above the established groundwater protection standard using the statistical procedures in subsection D of this section, the owner or operator shall:

(a) Notify the department within 14 days of this finding. The notification will include a statement that within 90 days the owner or operator will either:

(i) undertake the characterization and assessment actions required under 9VAC20-81-260 C 1; or

(ii) submit an alternate source demonstration as specified in subdivision A 5 of this section. If a successful demonstration is made within 90 days, the owner or operator may continue monitoring in accordance with Phase II monitoring program. If the 90-day period is exceeded, the owner or operator shall comply with the timeframes of 9VAC20-81-260 C unless the director has granted an extension to those timeframes; and

(b) Present the findings in the semi-annual report.

D. Statistical methods and constituent lists.

1. Acceptable test methods. The following statistical test methods may be used to evaluate groundwater monitoring data:

a. A parametric analysis of variance (ANOVA) followed by multiple comparisons procedures to identify statistically significant evidence of contamination. The method must 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 comparisons procedures to identify statistically significant evidence of contamination. The method must 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 that meets the performance standards specified below. Based on the justification submitted to the department, the director may approve the use of an alternative test. The justification must demonstrate that the alternative method meets the performance standards in subdivision 2 of this subsection.

2. Performance standards. Any statistical method chosen by the owner or operator shall comply with the following performance standards, as appropriate:

a. The statistical method used to evaluate groundwater monitoring data shall be appropriate for the distribution of monitoring parameters or constituents. If the distribution 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 groundwater 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 comparisons procedure is used, the Type I experiment-wise 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 must be maintained.

c. If a control chart approach is used to evaluate groundwater monitoring data, the specific type of control chart and its associated parameter values shall be protective of human health and the environment. The parameters shall 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.

d. If a tolerance interval or a predictional interval is used to evaluate groundwater monitoring data, the levels of confidence and, for tolerance intervals, the percentage of the population that the interval must contain, shall be protective of human health and the environment. These parameters shall 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 human health and the environment. Any estimated quantitation limit (EQL) 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 landfill.

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.

E. Recordkeeping and reporting.

1. Records pertaining to groundwater monitoring activities shall be retained at a specified location by the owner or operator throughout the active life and postclosure care period of the landfill, and shall include at a minimum:

a. All historical groundwater surface elevation data obtained from wells installed pursuant to subdivision A 3 a of this section;

b. All historical laboratory analytical results for groundwater sampling events required under the groundwater monitoring programs as described in this section;

c. All records of well installation, repair, or abandonment actions;

d. All department correspondence to the landfill; and

e. All approved variances, well subsets, wetlands, or other such director/department approvals.

2. Reporting requirements.

a. Annual report.

(1) An Annual Groundwater Monitoring Report shall be submitted by the owner or operator to the department no later than 120 days from the completion of sampling and analysis conducted under subdivision A 4 h of this section for the second semi-annual event or fourth quarterly event during each calendar year and shall by accompanied by:

(a) A signature page; and

(b) A completed QA/QC DEQ Form ARSC-01.

(2) The technical content of the annual report shall at a minimum, contain the following topical content:

(a) The landfill's name, type, permit number, current owner or operator, and location keyed to a USGS topographic map;

(b) Summary of the design type (i.e., lined versus unlined), operational history (i.e., trench fill versus area fill), and size (acres) of the landfill including key dates such as beginning and termination of waste disposal actions and dates different groundwater monitoring phases were entered;

(c) Description of the surrounding land use noting whether any adjoining land owners utilize private wells as a potable water source;

(d) A discussion of the topographic, geologic, and hydrologic setting of the landfill including a discussion on the nature of the uppermost aquifer (i.e., confined versus unconfined) and proximity to surface waters;

(e) A discussion of the monitoring wells network noting any modifications that were made to the network during the year or any nonperformance issues and a statement noting that the monitoring well network meets (or did not meet) the requirements of subdivision A 3 of this section;

(f) A listing of the groundwater sampling events undertaken during the previous calendar year;

(g) A historical table listing the detected constituents, and their concentrations identified in each well during the sampling period; and

(h) Evaluations of and appropriate responses to the groundwater elevation data; groundwater flow rate as calculated using the prior years elevation data; groundwater flow direction (as illustrated on a potentiometric surface map); and sampling and analytical data obtained during the past calendar year.

b. Semi-annual or quarterly report.

(1) After each sampling event has been completed for the 1st semi-annual or first, second and third quarterly groundwater sampling events, a semi-annual or quarterly monitoring report shall be submitted under separate cover by the owner or operator to the department no later than 120 days from the completion of sampling and analysis conducted under subdivision A 4 h of this section, unless as allowed under a director-approved extension. The report shall at a minimum contain the following items:

(a) Signature page signed by a professional geologist or qualified groundwater scientist;

(b) Landfill name and permit number;

(c) Statement noting whether or not all monitoring points within the permitted network installed to meet the requirements of subdivision A 3 a of this section were sampled as required under subdivision B 2 or 3 or C 2 or 3 during the event;

(d) Calculated rate of groundwater flow during the sampling period as required under subdivision A 4 c of this section;

(e) The groundwater flow direction as determined during the sampling period as required under subdivision A 4 c of this section presented as either plain text or graphically as a potentiometric surface map;

(f) Statement noting whether or not there were statistically significant increases over background or groundwater protection standards during the sampling period, the supporting statistical calculations, and reference to the date the director was notified of the increase pursuant to timeframes in subdivision B 2 or 3 or C 2 or 3, if applicable;

(g) Copy of the full Laboratory Analytical Report including dated signature page (laboratory manager or representative) to demonstrate compliance with the timeframes of subdivision A 4 h of this section. The department will accept the lab report in CD-ROM format.

(2) In order to reduce the reporting burden on the owner or operator and potential redundancy within the operating record, a discussion of the second semi-annual or fourth quarterly sampling event results may be presented in the Annual Report submission.

c. Other submissions. Statistically significant increase notifications, well certifications, the first determination report, alternate source demonstration, nature and extent study, assessment of corrective measures, presumptive remedy proposal, corrective action plan or monitoring plan, or other such report or notification types as may be required under 9VAC20-81-250 or 9VAC20-81-260, shall be submitted in a manner which achieves the timeframe requirements as listed in 9VAC20-81-250 or 9VAC20-81-260.

TABLE 3.1 GroundWater Solid Waste Constituent Monitoring List
Column A - Common Name1, 2	Column B - Common Name1, 2	CAS RN3
Acenaphthene	83-32-9
Acenaphthylene	208-96-8
Acetone	Acetone	67-64-1
Acetonitrile; Methyl cyanide	75-05-8
Acetophenone	98-86-2
2-Acetylaminofluorene; 2-AAF	53-96-3
Acrolein	107-02-8
Acrylonitrile	Acrylonitrile	107-13-1
Aldrin	309-00-2
Allyl chloride	107-05-1
4-Aminobiphenyl	92-67-1
Anthracene	120-12-7
Antimony	Antimony	(Total)
Arsenic	Arsenic	(Total)
Barium	Barium	(Total)
Benzene	Benzene	71-43-2
Benzo[a]anthracene; Benzanthracene	56-55-3
Benzo[b]fluoranthene	205-99-2
Benzo[k]fluoranthene	207-08-9
Benzo[ghi]perylene	191-24-2
Benzo[a]pyrene	50-32-8
Benzyl alcohol	100-51-6
Beryllium	Beryllium	(Total)
alpha-BHC	319-84-6
beta-BHC	319-85-7
delta-BHC	319-86-8
gamma-BHC; Lindane	58-89-9
Bis(2-chloroethoxy)methane	111-91-1
Bis(2-chloroethyl) ether; Dichloroethyl ether	111-44-4
Bis(2-chloro-1-methylethyl) ether; 2, 2'-Dichlorodiisopropyl ether; DCIP	108-60-1, See note 4
Bis(2-ethylhexyl)phthalate	117-81-7
Bromochloromethane;.Chlorobromomethane	Bromochloromethane;.Chlorobromomethane	74-97-5
Bromodichloromethane;.Dibromochloromethane	Bromodichloromethane;.Dibromochloromethane	75-27-4
Bromoform; Tribromomethane	Bromoform; Tribromomethane	75-25-2
4-Bromophenyl phenyl ether	101-55-3
Butyl benzyl phthalate; Benzyl butyl phthalate	85-68-7
Cadmium	Cadmium	(Total)
Carbon disulfide	Carbon disulfide	75-15-0
Carbon tetrachloride	Carbon tetrachloride	56-23-5
Chlordane	Note 5
p-Chloroaniline	106-47-8
Chlorobenzene	Chlorobenzene	108-90-7
Chlorobenzilate	510-15-6
p-Chloro-m-cresol; 4-Chloro-3-methylphenol	59-50-7
Chloroethane; Ethyl chloride	Chloroethane; Ethyl chloride	75-00-3
Chloroform; Trichloromethane	Chloroform; Trichloromethane	67-66-3
2-Chloronaphthalene	91-58-7
2-Chlorophenol	95-57-8
4-Chlorophenyl phenyl ether	7005-72-3
Chloroprene	126-99-8
Chromium	Chromium	(Total)
Chrysene	218-01-9
Cobalt	Cobalt	(Total)
Copper	Copper	(Total)
m-Cresol; 3-methyphenol	108-39-4
o-Cresol; 2-methyphenol	95-48-7
p-Cresol; 4-methyphenol	106-44-5
Cyanide	57-12-5
2,4-D; 2,4-Dichlorophenoxyacetic acid	94-75-7
4,4'-DDD	72-54-8
4,4'-DDE	72-55-9
4,4'-DDT	50-29-3
Diallate	2303-16-4
Dibenz[a,h]anthracene	53-70-3
Dibenzofuran	132-64-9
Dibromochloromethane; Chlorodibromomethane	Dibromochloromethane; Chlorodibromomethane	124-48-1
1,2-Dibromo-3-chloropropane; DBCP	1,2-Dibromo-3-chloropropane; DBCP	96-12-8
1,2-Dibrimoethane; Ethylene dibromide; EDB	1,2-Dibrimoethane; Ethylene dibromide; EDB	106-93-4
Di-n-butyl phthalate	84-74-2
o-Dichlorobenzene; 1,2-Dichlorobenzene	o-Dichlorobenzene; 1,2-Dichlorobenzene	95-50-1
m-Dichlorobenzene; 1,3-Dichlorobenzene	541-73-1
p-Dichlorobenzene; 1,4-Dichlorobenzene	p-Dichlorobenzene; 1,4-Dichlorobenzene	106-46-7
3,3'-Dichlorobenzidine	91-94-2
trans-1,4-Dichloro-2-butene	trans-1,4-Dichloro-2-butene	110-57-6
Dichlorodifluoromethane; CFC 12;	75-71-8
1.1-Dichloroethane; Ethylidene chloride	1,1-Dichloroethane; Ethylidene chloride	75-34-3
1,2-Dichloroethane; Ethylene dichloride	1,2-Dichloroethane; Ethylene dichloride	107-06-2
1,1-Dichloroethylene; 1,1-Dichloroethene; Vinylidene chloride	1,1-Dichloroethylene; 1,1-Dichloroethene; Vinylidene chloride	75-35-4
cis-1,2-Dichloroethylene; cis-1,2-Dichloroethene	cis-1,2-Dichloroethylene; cis-1,2-Dichloroethene	156-59-2
trans-1,2-Dichloroethylene	trans-1,2-Dichloroethylene; trans-1,2-Dichroroethene	156-60-5
2,4-Dichlorophenol	120-83-2
2,6-Dichlorophenol	87-65-0
1,2-Dichloropropane; Propylene dichloride	1,2-Dichloropropane; Propylene dichloride	78-87-5
1,3-Dichloropropane; Trimethylene dichloride	142-28-9
2, 2-Dichloropropane; isopropylidene chloride	594-20-7
1,1-Dichloropropene	563-58-6
cis-1,3-Dichloropropene	cis-1,3-Dichloropropene	10061-01-5
trans-1,3-Dichloropropene	trans-1,3-Dichloropropene	10061-02-6
Dieldrin	60-57-1
Diethyl phthalate	84-66-2
O,O-Diethyl O-2-pyrazinyl phosphorothioate; Thionazin	297-97-2
Dimethoate	60-51-5
p-(Dimethylamino)azobenzene	60-11-7
7,12-Dimethylbenz[a]anthracene	57-97-6
3,3'-Dimethylbenzidine	119-93-7
2,4-Dimethylphenol; m-Xylenol	105-67-9
Dimethyl phthalate	131-11-3
m-Dinitrobenzene	99-65-0
4,6-Dinitro-o-cresol; 4,6-Dinitro-2-methylphenol	534-52-1
2,4-Dinitrophenol	51-28-5
2,4-Dinitrotoluene	121-14-2
2,6-Dinitrotoluene	606-20-2
Dinoseb; DNBP; 2-sec-Butyl-4,6-dinitrophenol	88-85-7
Di-n-octyl phthalate	117-84-0
Diphenylamine	122-39-4
Disulfoton	298-04-4
Endosulfan I	959-96-8
Endosulfan II	33213-65-9
Endosulfan sulfate	1031-07-8
Endrin	72-20-8
Endrin aldehyde	7421-93-4
Ethylbenzene	Ethylbenzene	100-41-4
Ethyl methacrylate	97-63-2
Ethylmethanesulfonate	62-50-0
Famphur	52-85-7
Fluoranthene	206-44-0
Fluorene	86-73-7
Heptachlor	76-44-8
Heptachlor epoxide	1024-57-3
Hexachlorobenzene	118-74-1
Hexachlorobutadiene	87-68-3
Hexachlorocyclopentadiene	77-47-4
Hexachloroethane	67-72-1
Hexachloropropene	1888-71-7
2-Hexanone; Methyl butyl ketone	2-Hexanone; Methyl butyl ketone	591-78-6
Indeno[1,2,3-cd]pyrene	193-39-5
Isobutyl alcohol	78-83-1
Isodrin	465-73-6
Isophorone	78-59-1
Isosafrole	120-58-1
Kepone	143-50-0
Lead	Lead	(Total)
Mercury	(Total)
Methacrylonitrile	126-98-7
Methapyrilene	91-80-5
Methoxychlor	72-43-5
Methyl bromide; Bromomethane	Methyl bromide; Bromomethane	74-83-9
Methyl chloride; Chloromethane	Methyl chloride; Chloromethane	74-87-3
3-Methylcholanthrene	56-49-5
Methyl ethyl ketone; MEK; 2-Butanone	Methyl ethyl ketone; MEK; 2-Butanone	78-93-3
Methyl iodide; Iodomethane	Methyl iodide; Iodomethane	74-88-4
Methyl methacrylate	80-62-6
Methyl methanesulfonate	66-27-3
2-Methylnaphthalene	91-57-6
Methyl parathion; Parathion methyl methyl	298-00-0
4-Methyl-2-pentanone; Methyl isobutyl ketone	4-Methyl-2-pentanone; Methyl isobutyl ketone	108-10-1
Methylene bromide; Dibromomethane	Methylene bromide; Dibromomethane	74-95-3
Methylene chloride; Dichloromethane	Methylene chloride; Dichloromethane	75-09-2
Naphthalene	91-20-3
1,4-Naphthoquinone	130-15-4
1- Naphthylamine	134-32-7
2-Napthylamine	91-59-8
Nickel	Nickel	(Total)
o-Nitroaniline; 2-Nitroaniline	88-74-4
m-Nitroaniline; 3-Nitroaniline	99-09-2
p-Nitroaniline; 4-Nitroaniline	100-01-6
Nitrobenzene	98-95-3
o-Nitrophenol; 2-Nitrophenol	88-75-5
p-Nitrophenol; 4-Nitrophenol	100-02-7
N-Nitrosodi-n-butylamine	924-16-3
N-Nitrosodiethylamine	55-18-5
N-Nitrosodimethylamine	62-75-9
N-Nitrosodiphenylamine	86-30-6
N-Nitrosodipropylamine; N-Nitroso-N-dipropylamine; Di-n-propylnitrosamine	621-64-7
N-Nitrosomethylethalamine	10595-95-6
N-Nitrosopiperidine	100-75-4
N-Nitrosopyrrolidine	930-55-2
5-Nitro-o-toluidine	99-55-8
Parathion	56-38-2
Pentachlorobenzene	608-93-5
Pentachloronitrobenzene	82-68-8
Pentachlorophenol	87-86-5
Phenacetin	62-44-2
Phenanthrene	85-01-8
Phenol	108-95-2
p-Phenylenediamine	106-50-3
Phorate	298-02-2
Polychlorinated biphenyls; PCBS; Aroclors	Note 6
Pronamide	23950-58-5
Propionitrile; Ethyl cyanide	107-12-0
Pyrene	129-00-0
Safrole	94-59-7
Selenium	Selenium	(Total)
Silver	Silver	(Total)
Silvex; 2,4,5-TP	93-72-1
Styrene	Styrene	100-42-5
Sulfide	18496-25-8
2,4,5-T; 2,4,5-Trichlorophenoxyacetic acid	93-76-5
1,2,4,5-Tetrachlorobenzene	95-94-3
1,1,1,2-Tetrachloroethane	1,1,1,2-Tetrachloroethane	630-20-6
1,1,2,2-Tetrachloroethane	1,1,2,2-Tetrachloroethane	79-34-5
Tetrachloroethylene; Tetrachloroethene; Perchloroethylene	Tetrachloroethylene; Tetrachloroethene; Perchloroethylene	127-18-4
2,3,4,6-Tetrachlorophenol	58-90-2
Thallium	Thallium	(Total)
Tin	(Total)
Toluene	Toluene	108-88-3
o-Toluidine	95-53-4
Toxaphene	Note 7
1,2,4-Trichlorobenzene	120-82-1
1,1,1-Trichloroethane; Methychloroform	1,1,1-Trichloroethane; Methychloroform	71-55-6
1,1,2-Trichloroethane	1,1,2-Trichloroethane	79-00-5
Trichloroethylene; Trichloroethene ethene	Trichloroethylene; Trichloroethene ethane	79-01-6
Trichlorofluoromethane; CFC-11	Trichlorofluoromethane; CFC-11	75-69-4
2,4,5-Trichlorophenol	95-95-4
2,4,6-Trichlorophenol	88-06-2
1,2,3-Trichloropropane	1,2,3-Trichloropropane	96-18-4
O,O,O-Triethyl phosphorothioate	126-68-1
sym-Trinitrobenzene	99-35-4
Vanadium	Vanadium	(Total)
Vinyl acetate	Vinyl acetate	108-05-4
Vinyl chloride; Chloroethene	Vinyl chloride; Chloroethene	75-01-4
Xylene(total)	Xylene(total)	Note 8
Zinc	Zinc	(Total)

NOTES:

¹Common names are those widely used in government regulations, scientific publications, and commerce; synonyms exist for many chemicals.

²The corresponding Chemical Abstracts Service Index name as used in the 9th Collective Index, may be found in Appendix II of 40 CFR 258.

³Chemical Abstracts Service Registry Number. Where "Total" is entered, all species in the groundwater that contains this element are included.

⁴This substance is often called Bis(2-chloroisopropyl) ether, the name Chemical Abstracts Service applies to its noncommercial isomer, Propane, 2.2'-oxybis2-chloro (CAS RN 39638-32-9).

⁵Chlordane: This entry includes alpha-chlordane (CAS RN 5103-71-9), beta-chlordane (CAS RN 5103-74-2), gamma-chlordane (CAS RN 5566-34-7), and constituents of chlordane (CAS RN 57-74-9 and CAS RN 12739-03-6).

⁶Polychlorinated biphenyls (CAS RN 1336-36-3); this category contains congener chemicals, including constituents of Aroclor 1016 (CAS RN 12674-11-2), Aroclor 1221 (CAS RN 11104-28-2), Aroclor 1232 (CAS RN 11141-16-5), Aroclor 1242 (CAS RN 53469-21-9), Aroclor 1248 (CAS RN 12672-29-6), Aroclor 1254 (CAS RN 11097-69-1), and Arclor 1260 (CAS RN 11096-82-5).

⁷Toxaphene: This entry includes congener chemicals contained in technical toxaphene (CAS RN 8001-35-2), i.e., chlorinated camphene.

⁸Xylene (total): This entry includes o-xylene (CAS RN 96-47-6), m-xylene (CAS RN 108-38-3), p-xylene (CAS RN 106-42-3), and unspecified xylenes (dimethylbenzenes) (CAS RN 1330-20-7).

Notes

9 Va. Admin. Code § 20-81-250

Derived from Virginia Register Volume 27, Issue 12, eff. March 16, 2011; amended, Virginia Register Volume 27, Issue 22, eff. August 3, 2011; Amended, Virginia Register Volume 35, Issue 12, eff. 3/6/2019.

Statutory Authority: 9VAC02-81-10, 9VAC20-81-95, and 9VAC20-81-250: § 10.1-1402 of the Code of Virginia; 42 USC § 6941 et seq.; 40 CFR Parts 257 and 258.