WAC 173-350-500   Groundwater monitoring.  (1) Groundwater monitoring - Professional qualifications. All reports, plans, procedures, and design specifications required by this section shall be prepared by a licensed professional in accordance with the requirements of chapter 18.220 RCW.

     (2) Groundwater monitoring - Site characterization. A site proposed for solid waste activities shall be characterized for its geologic and hydrogeologic properties and suitability for constructing, operating, and monitoring a solid waste facility in accordance with all applicable requirements of this chapter. The site characterization report shall be submitted with the permit application and shall include at a minimum the following:

     (a) A summary of local and regional geology and hydrology, including:

     (i) Faults;

     (ii) Zones of joint concentrations;

     (iii) Unstable slopes and subsidence areas on-site;

     (iv) Areas of groundwater recharge and discharge;

     (v) Stratigraphy; and

     (vi) Erosional and depositional environments and facies interpretation(s);

     (b) A site-specific borehole program including description of lithology, soil/bedrock types and properties, preferential groundwater flow paths or zones of higher hydraulic conductivity, the presence of confining unit(s) and geologic features such as fault zones, cross-cutting structures, etc., and the target hydrostratigraphic unit(s) to be monitored. Requirements of the borehole program include:

     (i) Each boring will be of sufficient depth below the proposed grade of the bottom liner to identify soil, bedrock, and hydrostratigraphic unit(s);

     (ii) Boring samples shall be collected from five-foot intervals at a minimum and at changes in lithology. Representative samples shall be described using the unified soil classification system following ASTM D2487-85 and tested for the following if appropriate:

     (A) Particle size distribution by sieve and hydrometer analyses in accordance with approved ASTM methods (D422 and D1120); and

     (B) Atterburg limits following approved ASTM method D4318;

     (iii) Each lithologic unit on-site will be analyzed for:

     (A) Moisture content sufficient to characterize the unit using ASTM method D2216; and

     (B) Hydraulic conductivity by an in situ field method or laboratory method. All samples collected for the determination of permeability shall be collected by standard ASTM procedures;

     (iv) All boring logs shall be submitted with the following information:

     (A) Soil and rock descriptions and classifications;

     (B) Method of sampling;

     (C) Sample depth, interval and recovery;

     (D) Date of boring;

     (E) Water level measurements;

     (F) Standard penetration number following approved ASTM method D1586-67;

     (G) Boring location; and

     (H) Soil test data;

     (v) All borings not converted to monitoring wells or piezometers shall be carefully backfilled, plugged, and recorded in accordance with WAC 173-160-420;

     (vi) During the borehole drilling program, any on-site drilling and lithologic unit identification shall be performed under the direction of a licensed professional in accordance with the requirements of chapter 18.220 RCW who is trained to sample and identify soils and bedrock lithology;

     (vii) An on-site horizontal and vertical reference datum shall be established during the site characterization. The standards for land boundary surveys and geodetic control surveys and guidelines for the preparation of land descriptions shall be used to establish borehole and monitoring well coordinates and casing elevations from the reference datum;

     (viii) Other methods, including geophysical techniques, may be used to supplement the borehole program to ensure that a sufficient hydrogeologic site characterization is accomplished;

     (c) A site-specific flow path analysis that includes:

     (i) The depths to groundwater and hydrostratigraphic unit(s) including transmissive and confining units; and

     (ii) Potentiometric surface elevations and contour maps, direction and rate of horizontal and vertical groundwater flow;

     (d) Identification of the quantity, location, and construction (where available) of private and public wells within a two thousand-foot radius, measured from the site boundaries;

     (e) Tabulation of all water rights for groundwater and surface water within a two thousand-foot (610 m) radius, measured from site boundaries;

     (f) Identification and description of all surface waters within a one-mile (1.6 km) radius, measured from site boundaries;

     (g) A summary of all previously collected site groundwater and surface water analytical data, and for expanded facilities, identification of impacts of the existing facility upon ground and surface waters from landfill leachate discharges to date;

     (h) Calculation of a site water balance;

     (i) Conceptual design of groundwater and surface water monitoring systems, and where applicable a vadose zone monitoring system, including proposed construction and installation methods for these systems;

     (j) Description of land use in the area, including nearby residences;

     (k) A topographic map of the site and drainage patterns, including an outline of the waste management area, property boundary, the proposed location of groundwater monitoring wells, and township and range designations; and

     (l) Geologic cross sections.

     (3) Groundwater monitoring - System design.

     (a) The groundwater monitoring system design and report shall be submitted with the permit application and shall meet the following criteria:

     (i) A sufficient number of monitoring wells shall be installed at appropriate locations and depths to yield representative groundwater samples from those hydrostratigraphic units which have been identified in the site characterization as the earliest potential contaminant flowpaths;

     (ii) Represent the quality of groundwater at the point of compliance, and include at a minimum:

     (A) A groundwater flow path analysis which supports why the chosen hydrostratigraphic unit is capable of providing an early warning detection of any groundwater contamination.

     (B) Documentation and calculations of all of the following information:

     (I) Hydrostratigraphic unit thickness including confining units and transmissive units;

     (II) Vertical and horizontal groundwater flow directions including seasonal, man-made, or other short-term fluctuations in groundwater flow;

     (III) Stratigraphy and lithology;

     (IV) Hydraulic conductivity; and

     (V) Porosity and effective porosity.

     (b) Upgradient monitoring wells (background wells) shall meet the following performance criteria:

     (i) Shall be installed in groundwater that has not been affected by leakage from a landfill unit; or

     (ii) If hydrogeologic conditions do not allow for the determination of an upgradient monitoring well, then sampling at other monitoring wells which provide representative background groundwater quality may be allowed.

     (c) Downgradient monitoring wells (compliance wells) shall meet the following performance criteria:

     (i) Represent the quality of groundwater at the point of compliance;

     (ii) Be installed as close as practical to the point of compliance;

     (iii) When physical obstacles preclude installation of groundwater monitoring wells at the relevant point of compliance at the landfill unit or solid waste facility, the downgradient monitoring system may be installed at the closest practical distance hydraulically downgradient from the relevant point of compliance that ensures detection of groundwater contamination in the chosen hydrostratigraphic unit.

     (d) All monitoring wells shall be constructed in accordance with chapter 173-160 WAC, Minimum standards for construction and maintenance of wells, and chapter 173-162 WAC, Regulation and licensing of well contractors and operators.

     (e) The owner or operator shall notify the jurisdictional health department and the department of any proposed changes to the design, installation, development, and decommission of any monitoring wells, piezometers, and other measurement, sampling, and analytical devices. Proposed changes shall not be implemented prior to the jurisdictional health department's written approval. Upon completing changes, all documentation, including date of change, new monitoring well location maps, boring logs, and monitoring well diagrams, shall be submitted to the jurisdictional health department and shall be placed in the operating record.

     (f) All monitoring wells, piezometers, and other measurement, sampling, and analytical devices shall be operated and maintained so that they perform to design specifications throughout the life of the monitoring program.

     (4) Groundwater monitoring - Sampling and analysis plan.

     (a) The groundwater monitoring program shall include consistent sampling and analysis procedures that are designed to provide monitoring results that are representative of groundwater quality at the upgradient and downgradient monitoring wells. In addition to monitoring wells, facilities with hydraulic gradient control and/or leak detection systems will provide representative groundwater samples from those systems. The owner or operator shall submit a compliance sampling and analysis plan as part of the permit application. The plan shall include procedures and techniques for:

     (i) Sample collection and handling;

     (ii) Sample preservation and shipment;

     (iii) Analytical procedures;

     (iv) Chain-of-custody control;

     (v) Quality assurance and quality control;

     (vi) Decontamination of drilling and sampling equipment;

     (vii) Procedures to ensure employee health and safety during well installation and monitoring; and

     (viii) Well operation and maintenance procedures.

     (b) Facilities collecting leachate shall include leachate sampling and analysis as part of compliance monitoring.

     (c) The groundwater monitoring program shall include sampling and analytical methods that are appropriate for groundwater samples. The sampling and analytical methods shall provide sufficient sensitivity, precision, selectivity and limited bias such that changes in groundwater quality can be detected and quantified. All samples shall be sent to an accredited laboratory for analyses in accordance with chapter 173-50 WAC, Accreditation of environmental laboratories.

     (d) Groundwater elevations shall be measured in each monitoring well immediately prior to purging, each time groundwater is sampled. The owner or operator shall determine the rate and direction of groundwater flow each time groundwater is sampled. All groundwater elevations shall be determined by a method that ensures measurement to the one hundredth of a foot (3 mm) relative to the top of the well casing.

     (e) Groundwater elevations in wells that monitor the same landfill unit shall be measured within a period of time short enough to avoid any groundwater fluctuations which could preclude the accurate determination of groundwater flow rate and direction.

     (f) The owner or operator shall establish background groundwater quality in each upgradient and downgradient monitoring well. Background groundwater quality shall be based upon a minimum of eight independent samples. Samples shall be collected for each monitoring well and shall be analyzed for parameters required in the permit for the first year of groundwater monitoring. Each independent sampling event shall be no less than one month after the previous sampling event.

     (g) Groundwater quality shall be determined at each monitoring well at least quarterly during the active life of the solid waste facility, including closure and the post-closure period. More frequent monitoring may be required to protect downgradient water supply wells. Groundwater monitoring shall begin after background groundwater quality has been established. The owner or operator may propose an alternate groundwater monitoring frequency. Groundwater monitoring frequency must be no less than semiannually. The owner or operator must apply for a permit modification or must apply during the renewal process for changes in groundwater monitoring frequency making a demonstration based on the following information:

     (i) A characterization of the hydrostratigraphic unit(s) including the unsaturated zone, transmissive and confining units and include the following:

     (A) Hydraulic conductivity; and

     (B) Groundwater flow rates;

     (ii) Minimum distance between upgradient edge of the solid waste handling unit and downgradient monitoring wells (minimum distance of travel); and

     (iii) Contaminant fate and transport characteristics.

     (h) All facilities shall test for the following parameters:

     (i) Field parameters:

     (A) pH;

     (B) Specific conductance;

     (C) Temperature;

     (D) Static water level;

     (ii) Geochemical indicator parameters:

     (A) Alkalinity (as Ca CO₃);

     (B) Bicarbonate (HCO₃);

     (C) Calcium (Ca);

     (D) Chloride (Cl);

     (E) Iron (Fe);

     (F) Magnesium (Mg);

     (G) Manganese (Mn);

     (H) Nitrate(NO₃);

     (I) Sodium (Na);

     (J) Sulfate (SO₄);

     (iii) Leachate indicators:

     (A) Ammonia (NH₃-N);

     (B) Total organic carbon (TOC);

     (C) Total dissolved solids (TDS).

     (i) Based upon the site specific waste profile and also the leachate characteristics for lined facilities, the owner or operator shall propose additional constituents to include in the monitoring program. The jurisdictional health department shall specify the additional constituents in the solid waste permit.

     (j) Testing shall be performed in accordance with "Test Methods for Evaluating Solid Waste, Physical/Chemical Methods," U.S. EPA Publication SW-846, or other testing methods approved by the jurisdictional health department.

     (k) Maximum contaminant levels (MCL) for groundwater are those specified in chapter 173-200 WAC, Water quality standards for groundwaters of the state of Washington.

     (5) Groundwater monitoring - Data analysis, notification and reporting.

     (a) The results of monitoring well sample analyses as required by subsection (4)(h) and (i) of this section shall be evaluated using an appropriate statistical procedure(s), as approved by the jurisdictional health department during the permitting process, to determine if a significant increase over background has occurred. The statistical procedure(s) used shall be proposed in the sampling and analysis plan and be designed specifically for the intended site, or prescriptive statistical procedures from appropriate state and federal guidance may be used.

     (b) If statistical analyses determine a significant increase over background:

     (i) The owner or operator shall:

     (A) Notify the jurisdictional health department and the department of this finding within thirty days of receipt of the sampling data. The notification shall indicate what parameters or constituents have shown statistically significant increases;

     (B) Immediately resample the groundwater for the parameter(s) showing statistically significant increase in the monitoring well(s) where the statistically significant increase has occurred;

     (C) Establish a groundwater protection standard using the groundwater quality criteria of chapter 173-200 WAC, Water quality standards for groundwaters of the state of Washington. Constituents for which the background concentration level is higher than the protection standard, the owner or operator shall use background concentration for constituents established in the facility's monitoring record.

     (ii) The owner or operator may demonstrate that a source other than a landfill unit or solid waste facility caused the contamination, or the statistically significant increase resulted from error in sampling, analyses, statistical evaluation, or natural variation in groundwater quality. If such a demonstration cannot be made and the concentrations or levels of the constituents:

     (A) Meet the criteria established by chapter 173-200 WAC, Water quality standards for groundwaters of the state of Washington, the owner or operator shall:

     (I) Assess and evaluate sources of contamination; and

     (II) Implement remedial measures in consultation with the jurisdictional health department and the department.

     (B) Exceed the criteria established by chapter 173-200 WAC, Water quality standards for groundwaters of the state of Washington, the owner or operator shall:

     (I) Characterize the chemical composition of the release and the contaminant fate and transport characteristics by installing additional monitoring wells;

     (II) Assess and, if necessary, implement appropriate intermediate measures to remedy the release. The measures shall be approved by the jurisdictional health department and the department; and

     (III) Evaluate, select, and implement remedial measures as required by chapter 173-340 WAC, the Model Toxics Control Act cleanup regulation, where applicable. The roles of the jurisdictional health department and the department in remedial action are further defined by WAC 173-350-900.

     (c) The owner or operator shall submit a copy of an annual report to the jurisdictional health department and the department by April 1st of each year. The jurisdictional health department may require more frequent reporting based on the results of groundwater monitoring. The annual report shall summarize and interpret the following information:

     (i) All groundwater monitoring data, including laboratory and field data for the sampling periods;

     (ii) Statistical results and/or any statistical trends including any findings of any statistical increases for the year and time/concentration series plots;

     (iii) A summary of concentrations above the maximum contaminant levels of chapter 173-200 WAC;

     (iv) Static water level readings for each monitoring well for each sampling event;

     (v) Potentiometric surface elevation maps depicting groundwater flow rate and direction for each sampling event, noting any trends or changes during the year;

     (vi) Geochemical evaluation including cation-anion balancing and trilinear and/or stiff diagraming for each sampling event noting any changes or trends in water chemistry for each well during the year; and

     (vii) Leachate analyses where appropriate for each sampling event.



[Statutory Authority: Chapter 70.95 RCW. 03-03-043 (Order 99-24), § 173-350-500, filed 1/10/03, effective 2/10/03.]