7 Del. Admin. Code § 1302-265-F-265.93

Current through Reigster Vol. 28, No. 6, December 1, 2024

Section 1302-265-F-265.93 - Preparation, Evaluation and Response

(a) By the effective date of these amendments, the owner or operator must prepare an outline of a ground-water quality assessment program. The outline must describe a more comprehensive ground-water monitoring program (than that described in § 265.91 and § 265.92) capable of determining:

(1) Whether hazardous waste or hazardous waste constituents have entered the groundwater;

(2) The rate and extent of migration of hazardous waste or hazardous waste constituents in the groundwater; and

(3) The concentrations of hazardous waste or hazardous waste constituents in the groundwater.

(b) For each indicator parameter specified in § 265.92 (b)(3), and other specific parameters designated by the Department, as addressed in § 265.92 (d)(3), the owner or operator must calculate the arithmetic mean and variance, based on at least four replicate measurements on each sample, for each well monitored in accordance with § 265.92 (d)(2) and (d)(3), and compare these results with its initial background arithmetic mean. The comparison must consider individually each of the wells in the monitoring system, and must use the Student's t-test at the 0.01 level of significance (see Appendix IV) to determine statistically significant increases (and decreases, in the case of pH) over initial background.

(c)

(1) If the comparisons for the upgradient wells made under paragraph (b) of this section show a significant increase (or pH decrease) the owner or operator must submit this information in accordance with § 265.94 (a)(2)(ii).

(2) If the comparisons for downgradient wells made under paragraph (b) of this section show a significant increase (or pH decrease), the owner or operator must then immediately obtain additional ground-water samples from those downgradient wells where a significant difference was detected, split the samples in two, or obtain analyses of all additional samples to determine whether the significant difference was a result of laboratory error.

(d)

(1) If the analyses performed under paragraph (c)(2) of this section confirm the significant increases (or pH decrease), the owner or operator must provide written notice to the Secretary - within seven days of the date of such confirmation - that the facility may be affecting ground-water quality.

(2) Within 15 days after the notification under paragraph (d)(1) of this section, the owner or operator must develop and submit to the Secretary a specific plan, based on the outline required under paragraph (a) of this section and certified by a "qualified engineer" or "qualified geologist" for a ground-water quality assessment program at the facility. This report is to be placed in the facility's operating record and maintained until closure of the facility.

(3) The plan to be submitted under § 265.90 (e)(1) or paragraph (d)(2) of this section must specify:

(i) The number, location, and depth of wells;

(ii) Sampling and analytical methods for those hazardous wastes or hazardous waste constituents in the facility;

(iii) Evaluation procedures, including any use of previously gathered ground-water quality information; and

(iv) A schedule of implementation.

(4) The owner or operator must implement the ground-water quality assessment plan which satisfies the requirements of paragraph (d)(3) of this section, and, at a minimum, determine:

(i) The rate and extent of migration of the hazardous waste or hazardous waste constituents in the groundwater; and

(ii) The concentrations of the hazardous waste or hazardous waste constituents in the groundwater.

(5) The owner or operator must make his first determination under paragraph (d)(4) of this section as soon as technically feasible, and, within 15 days after that determination, submit to the Secretary a written report containing an assessment of the ground-water quality. This report is to be placed in the facility's operating record and maintained until closure of the facility.

(6) If the owner or operator determines, based on the results of the first determination under paragraph (d)(4) of this section, that no hazardous waste or hazardous waste constituents from the facility have entered the groundwater, then he may reinstate the indicator evaluation program described in § 265.92 and paragraph (b) of this section. If the owner or operator reinstates the indicator evaluation program, he must so notify the Secretary in the report submitted under paragraph (d)(5) of this section.

(7) If the owner or operator determines, based on the first determination under paragraph (d)(4) of this section, that hazardous waste or hazardous waste constituents from the facility have entered the groundwater, then he:

(i) Must, within 180 days of this determination, submit to the Department a plan including measures to mitigate and prevent and if necessary further monitor the spread of hazardous waste or hazardous waste constituents off site. Subsequent to written approval of the plan or portions thereof by the Department, the plan must be implemented by the owner or operator of the facility in accordance with the timetable specified by the Department. Depending on the contents of the mitigation plan, including the nature of the mitigation measures, the plan must be prepared and implemented by a "qualified engineer" and/or "qualified geologist", as appropriate. The mitigation plan must include the following as a minimum:

(1) Analysis of the concentration and extent of migration of the hazardous waste or hazardous waste constituents and potential problems associated with this condition. This must include an isopach map and cross-section showing the extent of migration of hazardous waste or hazardous waste constituents, if any.

(2) A detailed technical plan including the proposed procedure for containing and removing the condition of contamination.

(3) A schedule for implementation of the plan.

(4) An assessment of the potential impact of the mitigation program on the quality and quantity of groundwater and surface water.

(5) A proposed monitoring program to detect and determine the impact of the mitigation lan on groundwater and surface water at the site.

(ii) Must continue to make the determinations required under paragraph (d)(4) of this section on a quarterly basis until final closure of the facility, if the ground-water quality assessment plan was implemented prior to final closure of the facility; or

(iii) May cease to make the determinations required under paragraph (d)(4) of this section, if the ground-water quality assessment plan was implemented during the post-closure care period.

(e) Notwithstanding any other provision of this subpart, any ground-water quality assessment to satisfy the requirements of § 265.93 (d)(4) which is initiated prior to final closure of the facility must be completed and reported in accordance with § 265.93 (d)(5).

(f) Unless the groundwater is monitored to satisfy the requirements of § 265.93 (d)(4), at least annually the owner or operator must evaluate the data on ground-water surface elevations obtained under § 265.92 (e) to determine whether the requirements under § 265.91 (a) for locating the monitoring wells continues to be satisfied. If the evaluation shows that § 265.91 (a) is no longer satisfied, the owner or operator must immediately modify the number, location, or depth of the monitoring wells to bring the ground-water monitoring system into compliance with this requirement.

7 Del. Admin. Code § 1302-265-F-265.93

22 DE Reg. 678 (2/1/2019) (Final)