§ 250.704. General attainment requirements for groundwater.
(a) For any standard selected, the attainment demonstration for the groundwater media shall be made at the point of compliance as defined in Subchapters BD (relating to background standards; Statewide health standards; and site-specific standards).
(b) A sufficient number and location of monitoring wells necessary to demonstrate attainment of each plume of contamination shall be installed at the point of compliance for each aquifer based on site-specific conditions. Well locations shall be selected to yield an adequate amount of water to produce statistically valid results.
(c) In cases where the site characterization has determined the groundwater contamination (plume) extends beyond the property boundary, and the concentration of regulated substances beyond the property is above the cleanup levels of the standard selected, then the location and number of wells shall determine compliance:
(1) At and beyond the property boundary.
(2) Within the area of property shown, in the site investigation report, to be contaminated with regulated substances above the selected standard.
(d) For statistical methods under § 250.707(b)(2)(i) (relating to statistical tests), the demonstration of attainment for groundwater shall be based on at least eight consecutive quarters of groundwater data, which may include characterization data. As an alternative, the Department may accept fewer quarterly sampling events with written approval from the Department under the following conditions:
(1) There is adequate spatial monitoring of the plume upgradient which indicates a decreasing concentration trend toward the downgradient property boundary.
(2) Parameters affecting the fate and transport of regulated substances within the plume have been fully evaluated.
(3) Concentrations of regulated substances in the plume at the point of compliance monitoring wells along the downgradient property boundary are all less than or equal to the groundwater standard or the limit relating to the PQL, whichever is higher, in all samples collected during the quarters of monitoring.
(4) One of the following requirements are met:
(i) The age of the plume is sufficiently well known to permit a judgment to be made regarding its stability.
(ii) The remediation includes source removal or containment actions which would reduce the chemical flux into the plume.
(e) For statistical methods under § 250.707(b)(2)(ii) and (c), the minimum number of samples required for demonstrating attainment shall be as specified by the documentation of the chosen method.
The provisions of this § 250.704 issued under sections 104(a) and 303(a) of the Land Recycling and Environmental Remediation Standards Act (35 P. S. § § 6026.104(a) and 6026.303(a)).
The provisions of this § 250.704 amended January 7, 2011, effective January 8, 2011, 41 Pa.B. 230. Immediately preceding text appears at serial pages (285793) to (285794).
This section cited in 25 Pa. Code § 250.707 (relating to statistical tests).
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