PB95-207452
GUIDANCE FOR ESTABLISHING RELIEF FROM
EFFLUENT LIMITATIONS FOR THE COAL MINING
POINT SOURCE CATEGORY
(U.S.) ENVIRONMENTAL PROTECTION AGENCY, WASHINGTON, DC
1995
U;S DEPARTMENT Of COMMERCE
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON DC 20460
SUBJECT: Guidance for Establishing Relief from Effluent limitations
for the Coal Mining Point Source Category
FROM; Robert B* Schaffer, Director
Effluent Guidelines Division
TO: Deputy Assistant Administrator v.. wr Enforcement
Reg1onal Enfo rcement D1rectors
Director, Permit Division
Director, Office of Environmental Review
* *'
Summary:
This memorandum offers guidance on the application of the exemption
clause contained 1n the BPT and NSPS regulation for the coal mining
point source category* General guidance Is offered which 1s
applicable to all discharges from the coal mining point source
category. Specific considerations are offered for discharges from "^
surface mines, from deep mines, and from coal preparation plants. The
specific considerations are further divided for the purpose of the
exemption, as to the meaning of the term "contain" and the meaning of
the term "treat" as they relate to runoff from a 10-year 24-hour
rainfall* Examples are provided to further explain the exemption.
History:
On April 26, 1977, the Agency promulgated effluent limitations
guidelines representing best practicable control technology currently
available (BPT) for the Coal HInlng Point Source Category (42FR21380).
Contained 1n this final BPT regulation was an exemption for discharges
resulting from any precipitation event at facilities designed,
constructed, and maintained to contain or treat the volume of
discharge trf»1ch would result from a ten-year 24-hour precipitation
event*
On January 12, 1979, the Agency promul gated final new source
performance standards {NSPS) for the Coal Mining Point Source Category
(44FR2586), The NSPS also contained an exemption for discharges
res¥Tt1r>g from precipitation events for facilities designed,
constructed, and maintained to contain or treat the volume of
WBStewater which would result from a 10-year 24-hour precipitation
event. However, the exemption 1n the NSPS differed from the exemption
1n the BPT regulation in that relief from NSPS effluent standards was
granted only upon the occurance of a 10-year 24-hour or larger
precipitation event or snow melt, That is, relief was predicated both
on the design, construction, and maintenance of the facility and upon
demonstration by the operator that a 10-year 24-hour precipitation
event had occurred.
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In order to mafce EPA's BPT regulations identical to the NSPS, and to
make both consistent with the regulations promulgated by the
Department of Interior under the Surface Mining Control and
Reclamation Act of 1977, the Agency on April 2, 1-979, amended the BPT
regulation, changing the exemption in 8PT to agree with the exemption
contained in the HSPS (44FR19193),
The Agency received many comments from industry on this change and was
sued by the National Coal Association on both NSPS and the revised BPT
precipitation exemptions.
On July 6, 1979 the Agency suspended that portion of the exemption
which required that a 10-year 24-hour or larger precipitation event
actually occur and initiated a new rulemaking (44FR39391), On
August 14, 1&79, the Agency circulated and made available for public
comment two technical reports concerning the Issue (44£R47595). ?
* '
After receiving comments on these reports the Agency again
promulgated, on December 28, 1979, an exemption from otherwise
applicable effluent limitations and new source performance standards
for the coal mining point source category (44FR76788), With small
modifications* the exemption is essentially t"Re same as the original
provision contained in the BPT regulations promulgated on April 26,
1977.
Background;
The Agency has always recognized that relief is lecessary as a
practical matter for many discharges from the coal raining point source
category during and immediately after some precipitation events. It
would be unreasonable to require the coal mining industry to construct
retention structures or treatment facilities to handle the runoff from
extreme rainfall conditions which could statistically occur. It must
be emphasized,, however, that the regulations for the coal mining point
source category dd not require any specific treatment technique,
construction activity, or other process for the reduction of
pollution. The effluent limitations guidelines and new source
performance standards limit the concentration of pollutants which may
be discharged„ but allow for an excursion from the normal requirements
when precipitation causes an overflow or increase in the volume of a
discharge from a facility properly designed, constructed, and
maintained to contain or treat a 10-year 24-hour rainfall.
This relief applies to the excess volume caused by precipitation or
snow melt, and the resulting increase in flow or shock flow to the
settling facility or treatment facility*
While there nas been criticism of the relief used by the Agency, the
few alternatives suggested by environmental groups and industry are
substantially less satisfactory in light of the data available to the
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Agency at this time. This 1s discussed in detail in the preamble to
the original BPT regulation {42FR21380) and in the preamble to the
precipitation exemption amendment (44£R76789).
In order to minimize duplication and Inconsistency in regulation of
this industry, the Agency and the Department of Interior's Office of
Surface Mining (GSM) are working closely together on rulemaMng and
permits. On December 31, 1979, OSM suspended its existing
precipitation event exemption contained 1n its final regulation and
stated that relevant elements of EPA's revised precipitation exemption
would be used in lieu of the OSM exemption pending further OSM
rulemaking (44FR77440).
As a result of the EPA and OSM rulemaking, there have been numerous
requests by EPA Regional offices and the Office of Surface Mining for
guidance for granting relief from effluent limitations and guidelines.
* ;
The general relief or exemption as promulgated on December 28, 1979,
states that:
"Any overflow, increase 1r» volume of discharge or discharge from
a by-pass system caused by precipitation or snow melt shall not
be subject to the limitations set forth in .*,« of this section.
this exemption shall be available only if the facility is
designed, constructed and maintained to contain or treat the
volume of water which would fall on the areas covered by this
subpart during a 10-year 24-hour or larger precipitation event
{or snow melt of equivalent volume). The operator shall have the
burden of demonstrating to the appropriate authority that the
prerequisites for an exemption set forth in this subsection are
met."
General Guidance for Granting Belief
1* The exemption as stated in the final rule of December 28, 1979
must be included in the operators1 permit in order to be applicable to
that facility. Many existing permits have exemptions or relief
clauses stating requirements other than those set'forth in the final
rule. Such relief clauses remain binding unless and until an operator
requests a modification of his permit to include the exemption as
stated in the final rule of December 28, 1979,
2, The precipitation exemption is an affirmative defense to an
enforcement action. Therefore* there is no need to evaluate each and
every settling pond or treatment facility now under permit.
3. Relief can be granted to deep mine, surface mine, and preparation
plant discharges* This Includes discharges subcategorized as Coal
Preparation Plants and Associated Areas, Acid or Ferruginous Nine
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Drainage, and Alkaline Mine Drainage 1n the final rules for BPT and
NSPS.
4. Relief 1s granted as an excursion to the requirements for normal
operating conditions (i.e. without overflow, Increase In volume of
discharge, or discharge from a by-pass system) caused by surface
runoff only,
5« Relief can be granted for discharges during and Immediately after
any precipitation or snow melt* The Intensity of the event 1s not
specified.,
6. the term •"fcalntaln" Is intended to be synonymous with "operate,"
The facility must be operated at the time of the precipitation event
to contain or treat the specified volume of wastewater. Specifically,
In flaking a determ1n»t10ft of the ability of a facility to contain a
volume of waste water, sediment and sludge must not be permitted to
accumulate to such an extent that the settling facility or pond cannot
1n fact hold the volume of wastewater resulting from a 10-year 24-hour
rainfall. That is, sediment and sludge must be removed as required to
maintain a specific volume of wastewater*
7. "Contain" and "maintain" do not mean providing for draw down of
the pool level of the settling facility. There 1s no requirement that
relief be based on the settling basin or facility being emptied prior
to the rain fall or snow melt upon which the relief Is granted.
8, The relief does not grant, nor 1s It Intended to Imply to the
operator, the option of ceasing In his attempt to contain or treat the
runoff resulting from a precipitation event or snow melt* For
example, an operator does not have the option of turning off the lime
feed to a facility treating acid mine drainage at the start of or
during a precipitation event, regardless of the design and
construction of the waste
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"contain11 a volume of water* Additional guidance is offered below as
to the meaning of the term "contain" for the purpose of the
precipitation exemption.
12. The term "treat" for the purpose of the exemption means the
addition of flocculants in addition to physical settling to meet the
effluent limitations. "Treat" means the''.wastewter facility was
designed, constructed, and maintained to meet the dally maximum
effluent limitations for the maximum flow that would result from a
10-year 24-hour rainfall« While 8PT was not based on fl.occu1at1.on,
flocculants may be used to meet effluent limitations and the operator
has the option to "treat*1 the volume of water that would result from a
10-year 24-hour rainfall In order to qualify for the rainfall
exemption. As mentioned in paragraph 11 above, the second option 1s
to "contain" the volume of wastewater.
The following guidance presents specific considerations for surface
mines, deep mines, and preparation plants. The considerations are
divided as to the meaning and determination of a facility's ability to
"contain1* a volume equivalent ty the runoff from a 10-year 24-hour
rainfall and as to the meaning and determination of a facility's
ability to "treat" a volume equivalent to the runoff from a 10-year
24-hour rainfall.
In the following guidance, definitions are the same as those contained
in the final BPT rule which is attached to this memorandum
(42FR21380), These definitions are also contained in the final NSPS.
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guidance for granting Relief .to Surface
The roost frequent request for interpretation and guidance on the
precipitation exemption involves mine drainage from surface mines and
the discharge from settling ponds,
CASE 1- Relief can be granted to a surface mine drainage discharge
based on a facility being designed, constructed, and maintained to
contain a volume equivalent to the runoff from a 10-year 24~hour
rainfall *
Alternative A
o The mine operator must show the calculation of the area
contributing runoff to the settling basin or treatment facility.
This area includes the "active mining area" (Ai) as defined in
paragraph 434»llt»42jnat2138Q in the case of surface mines. In
addition, the area includes the drainage area (A2) which is
commingled with the drainage from the active mining area as
described if paragraph 434,32(d) and paragraph 434.42(c) of the
final regulation (42FR2138Q}.
o The mine operator must show the "10-year 24-^hour precipitation
event" (P) used for the location as defined in paragraph
434.T '«i) of the final regulation (42FJ2138Q).
o Obviously, all rainfall does not go to runoff. Some rainfall
does percolate into the ground to enter the ground water system.
Therefore, the operator may show a runoff coefficient (C), ?*ny
factors affect the runoff coefficient, including the soil
texture, topography, and vegetation. In lieu of other
calculations and methods of determining the runoff Coefficient,
the operator and the permitting authority may use the following
•runoff coefficients;
Runoff Coefficient Factors (Cj
Soil Texture
Sandy Clay and
loam loam Cjjjy,
Virgin land and Land Under
Reclamation 0.1 0.3 0.4
Active Mine Area 0.3 0.5 0,6
The above values are for land with 0-6% slopes. Increase the value by
0.1 for land with S-l0% slope and 0.2 for land with 10-30% slope*
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The above runoff factors are from "Erosion and Sedfmerit Control
Surface Hining In the Eastern United States Design", Environmental
Protection Agency, Technology Transfer Branch.
o The operator must show that the settling pond Mas maintained by
removal of the sludge and silt to maintain a pond volume (V)
equivalent to or greater titan -
V * P/12 C(Alx CJ,} + (A2 X Cjp
where: V » volume in acre • feet
P * 10-year 24-hour rainfall at the facility's site
1n Inches
Al * area of the active mining area In acres
Cl * runoff coefficient factor for the active mining area.
A]? * area from which runoff Is commingled Kith runoff from
~" the active mining area in acres.
C2 * runoff coefficient 'actor for the area from which runoff
"" is commingled with runoff from the active wining area
Example
An enforcement action 1s initiated against a surface mine operator
because of violation of the limitations for mine drainage.
The mine operator requests relief under the exemption contained in Ms
permit, which is the exemption contained In 44£R?6788. The sampling
mas conducted during a measurable precipitation event. The mine
operator shows that he designed and constructed a settling basin
having a capacity of 1£ acre .feet frora the top of the stage of the
highest dewatering device to tlie original bottom of the basin at the
time of construction.
At the time of sampling the mine operator shows he had 25 acres (Al)
1n the "active mining area*.,, including'the.bench' and fill. At the"
time of sampling, the settling basin received drainage from an
additional 35 acres (A2) of virgin land and land undergoing
reclamation. ~"
The active mine area has a slope of 0 to 5% and the virgin land and
land under reclamation where runoff goes to the settling basin has a
slope of 101 to 301. The soil is clay and loam. Therefore, from the
table above, the runoff coefficient for the active mining area (CJ.) is
0,5. For the other area contributing runoff to the settling basing
the runoff coefficient (C2) Is .3 «• .2 for slopes of 10* to 3QX or C2
» .5.
The 10-year 24-hour precipitation event for the mine location as taken
frosi the National Weather Service Technical Paper No. 40P "Rainfall
Frequency Atlas of the United States," May 1961, is four inches (P)
V - P/12 [(Al x Cl) + )A2 x C2)3
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V -4/12 1(25 x .5) + (S5x .5)3
V * 10 acre ft,
The mine operator can show that the sludge in the settling basin was
cleaned prior to the day of sampling and Is presently less than
one-third full. Therefore, the settling pond was maintained to
contain the required volume.
All requirements have been met for the operator to receive relief from
the effluent limitations and no enforcement action should be taken.
Alternative B
As an alternative to the above, the surface mine operator may use a
model such as the Water Shed Storm Hydrograph, Penn State Urban Runoff
Hodel, or similar model to determine the runoff volume at his site for
a 10-year 24-hour precipitation event.
o The operator must show the calculation for the active area and
the area contributing runoff to the settling basin as in
Alternative A above.
o The operator must show the 10-year 24-hour rainfall as in
Alternative A above*
o The operator must show the rationale for the composite curve
number (CN-or equivalent) used to determine the runoff volume for
the area contributing runoff to the settling pond.
o The operator must show that the settling basin was maintained to
contain the volume required for relief.
CASE 2. Relie' can be granted to a surface mine drainage discharge
based on the settling facility being designed, constructed, and
maintained to treat the volume equivalent to the runoff from a 10-year
24-hour precipitation event.
o The operator must show the areas contributing runoff to the
treatment facility as in CASE 1* above, including the active mine
area and the area from which runoff 1s commingled with runoff
from the active mining area.
o The operator must show the 10-year 24-hour precipitation event as
in CASE 1. above.
o Using the area and the 10-year 24-hour rainfall, the operator
must show what calculation was used to determine the volume of
water that would result from a 10-year 24-hour rainfall and the
corresponding design flow for the treatment system* The design
flow 1s based on the iixTmum flow contributing to the volume.
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The mine operator must show tils specific treatment for the design
flow to meet the daily maximum effluent limitations*
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guidance for grant Ing Relief to Deep Hlrvss
CASE 1. For deep mines relief can be granted when the operator
designs, constructs, and maintains Ms facility to contain the volume
of water equivalent to the runoff from a 10-year 24-hour precipitation
event on the surface areas,
o Relief Is not granted to facilities which receive only the
discharge Trow an underground mine. Relief is granted to
discharges caused by precipitation and the Subsequent surface
runoff. See paragraph 4 and 10 under General Guidance for
Granting Relief.
o Relief can be granted to discharges from facilities which receive
only surface runoff if the facilities are designed, constructed,
and maintained to contain the volume of water equivalent to the
run off from a iQ>v«aY 24-hour precipitation event* To determine
this volume refer to CASE 1, Alternative 8 under Guidance for
Granting Relief to Surface Nines.
o Relief 1s not granted to facilities designed, constructed, and
mairita1ne«rto contain only the volume of water equivalent to the
surface runoff going to the treatment facility when the runoff is
canning!ed with mine drainage discharged from the underground
mine itself. The discharge from the facility designed,
constructed, and maintained to contain the runoff volume from a
10-year £4-hour rainfall jgVus the volume discharged from the
underground mine Itself may oe granted relief from effluent
limitations.
o For the purpose of determining the volume discharged by the
underground wine itself, the volume discharged over 24 hours is
used, or the discharges by the deep mine must be retained 24
hours.
Exampl e
An enforcement action is taken against a deep mine operator because of
violation of the effluent limitations for mine drainage.
The mine operator requests relief from the enforcemsnt action, and the
exemption contained in his permit is the exemption contained 1n
44fj!p788. Tide sampling was conducted during a measurable
precipitation event. The mine operator shows that he designed,
constructed, and has maintained a settling basin capable of containing
10 acre feet of water.
The mine operator shows that 15 acres drain or send runoff to the
settling pond.
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The 10-year 24-hour rainfall is four Inches and the runoff coefficient
1s .5 for clay and 1o*m in a 0 to 51 slope*
V « 4/12 US x .5)
V * 2.5 acre feet
On Hie day of the violation the deep mine Itself discharged one and a
half million gallons of mine drainage. This volume of discharge 1s
verified by pump records or flow meters such as a weir or similar
device.
One million gallons equals 3.07 acre feet 1n volume, therefore, one
and a half million gallons equal 4.6 acre feet.
V • 4.6 + 2.5 * 7.1 acre feet
All requirements have been met for the operator to receive relief from
effluent limitations and.no enforcement action should be taken,
» * •
CASE 2, Relief can be granted to. deep mines when faculties are
designed, constructed, and maintained to treat the volume of water
equivalent to the runoff from a 10-year 24-hour precipitation event on
thefr surface areas.
o Relief 1s not granted to facilities which receive only the
discharge Jrm an underground mine.
o A facility treating only surface runoff may be granted relief If
the operator can show his treatment system through steps similar
to those described 1n CASE 2 above under guidance for Granting
Relief to Surface Hlnes.
o Relief is not granted to facilities designed, constructed, and
maintained"!;!) treat only the volume of surface runoff if the
surface runoff is commingled ifith the drainage from the deep mine
itself. The design, construction, and maintenance of the
facility would have to Include the volume discharged by the deep
mine Itself.
o The design flow for the treatment Astern, when surface runoff is
commingled wlth fKi discharge fromi thet deep mine itself, is the
sum of the design flow attributable to the surface runoff and the
design flow from the deep mine itself based on maximum flow from
the deep mine. The design flow from surface runoff 1s determined
as under CASE 2 above, under Guidance for Granting Relief to
Surface Mines. The design flow from the deep mine itself may be
determined from pump records or flow meters.
o The mine operator must show his specific treatment for the design
flow for the treatment system to meet the daily maximum effluent
limitations.
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Guidance for Granting Relief to Preparation Plant Discharge
CASE 1. For preparation plants, relief can be granted to facilities
which are designed, constructed, and maintained to contain the volume
of water going to runoff from a 10-year 24-hour rainfall on the "coal
preparation plant associated areas** as defined in the final regulation
and, if the discharges are commingled, the discharge from the ''coal
preparation plant" as also defined (42FR21380).
o Relief is not granted to facilities which receive only the
discharge Trim the coal preparati>* plant itself * Relief is
granted to discharges caused by precipitation and the subsequent
runoff from the coal preparation plant associated areas.
o In determining the volume of runoff from coal storage areas and
refuse areas, the runoff coefficient for active areas shall be
used. See Runoff ^Coefficient Factors under CASE 1 for Guidance
for Granting Relief to Surface Mines*
o The volume of runoff from a 10-year 24-hour precipitation event
for coal preparation plant associated areas can be determined by
the methods used above under Guidance for Granting Relief to
Surface Mines.
o If preparation plant wastewater is commingled with runoff from
preparation plant associated areas, the facility must also be
designed to contain the preparation plant waste water discharge
for 24 hours.
o To determine the vol time of wastewater discharge from a coal
preparation plant itself, an allowance for the volume of water
recycled back to the plant, if any, is not to be considered.
o In determining the discharge from the preparation plant itself,
the pump capacity of the discharge may be used, or a flow
measuring device such as a weir may be used*
o. Alternatively, the discharge from the preparation plant itself
may be determined by the design of the preparation plant and the
water use per ton of coal. Therefore, the tonnage run by the
preparation plant that day may be used along with the design
water use to determine the total discharge.
Exampl e
On the day of the violation, the coal preparation plant processed
8,500 tons of coal. The preparation plant was designed to use 900
gallons per ton. total discharge for the preparation plant is
1,650,000 gallons or 5 acre feet of water.
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The coal preparation plant associated area would discharge IS acre
feet of water as determined from the calculated area, 10-year 24-hour
rainfall» and the runoff coefficient.
If the settling facility has a volume greater than 20 acre feet and
this volume has been maintained, an exemption 1s warranted; provided,
that the,sampling v«s conducted during a measurable precipitation
event and the preparation plant permit had the exemption contained in
44FK76788,
CASE 2. Relief can be granted to discharges from preparation plants
which design, construct, and maintain a facility to treat the volume
of water gofng to runoff from a Id-year 24-hour rainfatt on the coal
preparation plant associated areas and, if the discharges are
commingled, the discharge frow the coal preparation plant itself.
o The design flow fwrn the preparation plant associated areas can
be determined from the volume as determined from the area»
10-year 24-hour rainfall, and runoff coefficient. Design flow is
based on maximum flow.
o Where the discharge from the preparation plant Itself is
commingled with the runoff from the associated areas, the design
flow must include this maximum discharge from the preparation
plant Itself.
o The operator must show his specific treatment for the design flow
to meet the daily maximum effluent limitations.
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