Rule 3745-525-630 | Hydrologic and hydraulic capacity requirements for CCR surface impoundments, 40 C.F.R. 257.82.
(A) The owner or operator of an existing or new CCR surface impoundment or any lateral expansion of a CCR surface impoundment shall design, construct, operate, and maintain an inflow design flood control system as specified in paragraphs (A)(1) and (A)(2) of this rule.
(1) The inflow design flood control system shall adequately manage flow into the CCR unit during and following the peak discharge of the inflow design flood specified in paragraph (A)(3) of this rule.
(2) The inflow design flood control system shall adequately manage flow from the CCR unit to collect and control the peak discharge resulting from the inflow design flood specified in paragraph (A)(3) of this rule.
(3) The inflow design flood is as follows:
(a) For a high hazard potential CCR surface impoundment, as determined under paragraph (A)(2) of rule 3745-525-204 or paragraph (A)(2) of rule 3745-525-205 of the Administrative Code, the probable maximum flood.
(b) For a significant hazard potential CCR surface impoundment, as determined under paragraph (A)(2) of rule 3745-525-204 or paragraph (A)(2) of rule 3745-525-205 of the Administrative Code, the one-thousand-year flood.
(c) For a low hazard potential CCR surface impoundment, as determined under paragraph (A)(2) of rule 3745-525-204 or paragraph (A)(2) of rule 3745-525-205 of the Administrative Code, the one-hundred-year flood.
(d) For an incised CCR surface impoundment, the twenty-five-year flood.
(B) Discharge from the CCR unit shall be handled in accordance with the surface water requirements under Chapter 6111. of the Revised Code.
(C) Inflow design flood control system plan.
(1) Content of the plan. The owner or operator shall prepare initial and periodic inflow design flood control system plans for the CCR unit according to the timeframes specified in paragraphs (C)(3) and (C)(4) of this rule. These plans shall document how the inflow design flood control system has been designed and constructed to meet the requirements of this rule. Each plan shall be supported by appropriate engineering calculations. The owner or operator of the CCR unit has completed the inflow design flood control system plan when the plan has been placed in the facility's operating record as required by paragraph (G)(4) of rule 3745-525-50 of the Administrative Code.
(2) Amendment of the plan. The owner or operator of the CCR unit may amend the written inflow design flood control system plan at any time provided the revised plan is placed in the facility's operating record as required by paragraph (G)(4) of rule 3745-525-50 of the Administrative Code. The owner or operator shall amend the written inflow design flood control system plan whenever there is a change in conditions that would substantially affect the written plan in effect.
(3) Timeframes for preparing the initial plan.
(a) Existing CCR surface impoundments. The owner or operator of the CCR unit shall have prepared the initial inflow design flood control system plan not later than October 17, 2016.
(b) New CCR surface impoundments and any lateral expansion of a CCR surface impoundment. The owner or operator shall prepare the initial inflow design flood control system plan not later than the date of initial receipt of CCR in the CCR unit.
(4) Frequency for revising the plan. The owner or operator shall prepare periodic inflow design flood control system plans required by paragraph (C)(1) of this rule every five years. The date of completing the initial plan is the basis for establishing the deadline to complete the first periodic plan. The owner or operator may complete any required plan prior to the required deadline provided the owner or operator places the completed plan into the facility's operating record within a reasonable amount of time. In all cases, the deadline for completing a subsequent plan is based on the date of completing the previous plan. For purposes of this paragraph, the owner or operator has completed an inflow design flood control system plan when the plan has been placed in the facility's operating record as required by paragraph (G)(4) of rule 3745-525-50 of the Administrative Code.
(5) The owner or operator shall obtain a certification from a qualified professional engineer stating that the initial and periodic inflow design flood control system plans meet the requirements of this rule.
(D) The owner or operator of the CCR unit shall comply with the recordkeeping requirements specified in paragraph (G) of rule 3745-525-50 of the Administrative Code, the notification requirements specified in paragraph (G) of rule 3745-525-60 of the Administrative Code, and the internet requirements specified in paragraph (G) of rule 3745-525-70 of the Administrative Code.
Last updated October 1, 2026 at 9:20 AM
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