Section 327IAC15-7-2. Definitions

   The following definitions apply throughout this rule:

(1) "1-year, 2-year, and 10-year, 24-hour precipitation event" means the maximum 24-hour precipitation event with a probable recurrence interval of once in one (1), two (2), and ten (10) years, respectively, as defined by the National Weather Service and Technical Paper No. 40, "Rainfall Frequency Atlas of the U.S.", May 1961, or equivalent regional or rainfall probability information developed therefrom.

(2) "4 × yearly sample frequency" means the performance of the associated monitoring once any time during each of the four (4) annual quarters:

(A) January-February-March;

(B) April-May-June;

(C) July-August-September; and

(D) October-November-December.

(3) "Acid or ferruginous mine drainage" means mine drainage which, before any treatment, either has a pH of less than six (6.0) or a total iron concentration equal to or greater than ten (10) milligrams per liter.

(4) "Active mining area" means the area, on and beneath land, used or disturbed in activity related to the extraction, removal, or recovery of coal from its natural deposits. This term excludes coal preparation plants, coal preparation plant associated areas, and post mining areas.

(5) "Alkaline mine drainage" means mine drainage which, before any treatment, has a pH equal to or greater than six (6.0) and a total iron concentration of less than ten (10) milligrams per liter.

(6) "Bond release" means the time at which the appropriate regulatory authority returns a reclamation or performance bond based upon its determination that reclamation work (including, in the case of underground mines, mine sealing and abandonment procedures) has been satisfactorily completed.

(7) "Coal preparation plant" means a facility where coal is subjected to cleaning, concentrating, or other processing or preparation in order to separate coal from its impurities and thereafter is loaded for transit to a consuming facility.

(8) "Coal preparation plant associated areas" means the coal preparation plant yards, immediate access roads, coal refuse piles, and coal storage piles and facilities.

(9) "Coal refuse disposal pile" means any coal refuse deposited on the earth and intended as a permanent disposal or long term storage (greater than one hundred eighty (180) days) of such material but does not include coal refuse deposited within the active mining area or coal refuse that is never removed from the active mining area.

(10) "Concentration" means the mass of any given material present in a unit volume of liquid. Unless otherwise indicated in this rule, concentration values shall be expressed in milligrams per liter (mg/l).

(11) "Controlled surface mine discharge" means any surface mine drainage that is pumped or siphoned from the active mining area.

(12) "Dry weather base flow" means the normal base flow coming from an area or treatment facility which is not immediately affected by run-off caused by rainfall. This flow is a result of ground water interference or a build-up of rainwater over a long period of time. Alternate limitations apply when this dry weather flow increases due to a precipitation event and continues until the flow again returns to the dry weather rate.

(13) "Mine drainage" means any drainage, and any water pumped or siphoned, from an active mining area or a post mining area.

(14) "ml/l" means milliliters per liter.

(15) "Post mining area" means either of the following:

(A) A reclamation area.

(B) The underground workings of an underground coal mine after the extraction, removal, or recovery of coal from its natural deposit has ceased and prior to bond release.

(16) "Precipitation event" means a rainfall, snow melt, or ice melt which causes a discharge or an increase in the volume of a discharge.

(17) "Reclamation area" means the surface area of a coal mine which has been returned to required contour and on which revegetation (specifically, seeding or planting) work has commenced.

(18) "Settleable solids" means that matter measured by the volumetric method specified in 40 CFR 434.64, which is: Fill an Imhoff cone to the one (1) liter mark with a thoroughly mixed sample. Allow to settle undisturbed for forty-five (45) minutes. Gently stir along the inside surface of the cone with a stirring rod. Allow to settle undisturbed for fifteen (15) minutes longer. Record the volume of settled material in the cone as milliliters per liter (ml/l). Where a separation of settleable and floating materials occurs, do not include the floating material in the reading. The method detection limit for measuring settleable solids shall be four-tenths (0.4) ml/l.

(19) "TSS" or "total suspended solids" means the mass of suspended matter in wastewater retained on a standard glass fiber filter after filtration of a well-mixed sample after drying for one (1) hour at one hundred three degrees Celsius (103°C).

(Water Pollution Control Division; 327 IAC 15-7-2; filed May 25, 1994, 11:00 a.m.: 17 IR 2284; errata filed Jul 11, 1994, 3:00 p.m.: 17 IR 2657; readopted filed Jan 10, 2001, 3:23 p.m.: 24 IR 1518; readopted filed Nov 21, 2007, 1:16 p.m.: 20071219-IR-327070553BFA; readopted filed Jul 29, 2013, 9:21 a.m.: 20130828-IR-327130176BFA)