Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

Natural Gas Drilling in the Marcellus Shale
 

NPDES Program Frequently Asked Questions 

1) What is the Marcellus Shale? 

The Marcellus Shale is an organic rich rock that has been estimated to contain from 50 to 

500 trillion cubic feet of natural gas1

. It was deposited in the Appalachian Basin 350 

million years ago as part of an ancient river delta and consists of the bottom layer of an 

Upper Devonian age sedimentary rock sequence. Like most shale, the Marcellus was 

deposited as extremely fine grained sediment, with small pore spaces and low 

permeability that prevents gas from easily migrating1. Often called the Marcellus Black 

Shale due to its color, the formation exists under much of southern New York, 

Pennsylvania, West Virginia, eastern Ohio, and far western Maryland. Although the 

shale outcrops at its namesake, Marcellus, New York, it generally lies at depths of 5,000 

to 9,000 feet throughout much of the area.2 The Marcellus Shale generally ranges in 

thickness from 50 to 200 feet. 

2) Why is the Marcellus Shale gas extraction suddenly important for natural gas 

production? 

The combination of advances in drilling and fracturing technology, the large volume of 

natural gas reserves, and its proximity to eastern cities have made the Marcellus Shale an 

important resource. Although the first commercial shale gas well was drilled in New 

York in 1821, extensive drilling and extraction of natural gas from shale deposits in the 

United States did not begin until the 1980’s.3,4 Horizontal drilling techniques, that make 

gas extraction viable in the Marcellus Shale, did not become commercially available until 

the late 1980s.5 Fracturing techniques that are needed to economically extract gas from 

impermeable shale deposits, like the Marcellus, also recently became refined.6 Analysis 

of the Marcellus formation geology suggests that areas in the north central and 

northeastern regions of Pennsylvania have a high potential to produce significant 

amounts of gas. This area of the country has not traditionally seen extensive gas well 

drilling.7 

1

 Soeder, D.J., and Kappel, W.M., 2009, Water Resources and Natural Gas Production from the Marcellus 

Shale: U.S. Geological Survey Fact Sheet 2009–3032, 6 p. 2 USGS, 2006, Assessment of Appalachian Basin Oil and Gas Resources: Devonian Shale-Middle and 

Upper Paleozoic Total Petroleum System.

3

 Hill, D.G., etal, 2003 , Fractured Shale Gas Potential in New York, posted at: 

http://www.pe.tamu.edu/wattenbarger/public_html/Selected_papers/--

Shale%20Gas/fractured%20shale%20gas%20potential%20in%20new%20york.pdf 

4

 Shirley, K., 2001, Shale Gas Exciting Again, Explorer, posted at: 

http://www.aapg.org/explorer/2001/03mar/gas_shales.cfm 

5

 Energy Information Administration, Office of Oil and Gas, U.S. Department of Energy, Drilling Sideways 

– A Review of Horizontal Well Technology and its Domestic Application, April, 1993. 6

 Ground Water protection Council, 2009, Modern Shale Gas Development in the United States: A Primer, 

116 p., posted at: www.gwpc.org

7

 Reference: “Drilling for Natural Gas in the Marcellus Shale Formation - Frequently Asked Questions” as 

written by the Pennsylvania Department of Environmental Protection and posted at 

http://www.dep.state.pa.us/dep/deputate/minres/oilgas/new_forms/marcellus/marcellus.htm. 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

Figure 1: Location of Marcellus Shale8 

3) How is extraction from the Marcellus Shale different from other natural gas 

extraction? 

Marcellus gas extraction is considered “unconventional” by the Department of Energy’s 

Energy Information Administration because the gas is found within a shale formation 

rather than a more normal sandstone or limestone rock layer.9 Conventional gas 

extraction typically involves drilling through an impervious rock formation into a porous 

formation saturated with gas and trapped by the impervious cap rock. Conventional 

extraction typically relies on the high permeability of the rock that allows gas to readily 

flow to the well for production. Although horizontal wells have become more common 

8

 Milici, R.C., USGS Open File Reports 2005-1268, Assessment of Undiscovered Natural Gas Resources 

in Devonian Black Shales, Appalachian Basin, Eastern United States, 2005 9

 See http://www.eia.doe.gov/oiaf/analysispaper/unconventional_gas.html. 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

over time for conventional gas extraction, wells are more typically relatively straight and 

vertical. 

Unconventional gas extraction includes: deep gas (greater than 15,000 feet), tight gas, 

shale gas, coal bed methane, gas from geopressurized zones, and methane hydrates. Like 

tight gas which is extracted from sandstone and limestone deposits that have a low 

permeability, shale gas extraction requires techniques such as fracturing and horizontal 

drilling that are less commonly used in conventional extraction. Horizontal drilling is 

commonly used in shale gas extraction as a means to increase potential production. 

Horizontal drilling results in a well extending through a much larger portion of the shale; 

thereby increasing the area from which a well can produce and the amount of gas 

produced. 

In addition to greater use of horizontal drilling, operators make extensive use of hydraulic 

fracturing as a means to economically produce gas from deposits with low permeability, 

such as the Marcellus Shale. Hydraulic fracturing requires drillers to pump large 

amounts of water mixed with sand or other proppants into the shale formation under high 

pressure (approximately 10,000 psi) to fracture the shale formation adjacent to the 

wellbore and to create paths that connect the gas to the well. This allows the natural gas 

to flow freely up the well for compression, transmission, and sale. Once the hydraulic 

fracturing process is completed and the wellbore pressure is released, approximately onethird of the water flows out of the well11. That hydraulic fracturing flowback water 

(HFFW) must be treated to remove chemicals and minerals.1

 Horizontal wells in the 

Marcellus Shale require 3 to 5 million gallons for hydraulic fracturing, whereas 

conventional wells of a similar depth required approximately 1 million gallons of water.10 

The greater quantity of water used for fracturing in shale gas wells is due in part to the 

extended reach of horizontal wells in addition to the amount of fracturing required to 

extract gas from a rock that has low permeability11. 

10 Gaudlip, A.W., et. al., 2008, Marcellus Shale Water Management Challenges in Pennsylvania, SPE
 

119898 

11 University of Maryland, Reconciling Shale Gas Development with Environmental Protection,
 

Landowner Rights, and Local Community Needs, Schools of Public Policy, July, 2010.
 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

Figure 2: Example of a Horizontal Well1 

4) How many wells could be expected at a Marcellus gas extraction site? 

The number of wells drilled at a site is highly variable and is dependent on local drilling 

activity, recycling practices of operators, state regulations on well spacing, and local 

ordinances, among other factors. In general, 1 to 8 wells can be placed on a well pad. A 

site is expected to consist of only one well pad. Since each well will require numerous 

trucks to haul away HFFW, a treatment facility (Publicly Owned Treatment Works 

(POTW) or Centralized Waste Treatment facility (CWT)) would be expected to receive a 

number of truck loads from a single site. 

5) How similar is the Marcellus Shale to other shale deposits where natural gas is 

currently extracted? 

Major shale deposits currently being developed in the United States include the Antrim, 

Barnett, Fayetteville, Haynesville, Marcellus, and Woodford Shale. Those shale deposits 

all have the common characteristic of low porosity and permeability. Extraction almost 

universally requires horizontal drilling combined with extensive hydraulic fracturing. 

There are some differences in depth, aerial extent, gas content, and thickness that 

distinguish between the different shale deposits. A comparison follows in Table 1. Gas 

4
 
 

 

Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

extraction activities at all of those shale deposits will present the same challenges for 

waste disposal. 

Figure 3: Shale Gas Plays in the United States12 

Table 1: Comparison of Data for the Gas Shales in the United States12 

Gas Shale 

Basin 

Estimated 

Basin Area 

(mi2) 

Depth (ft) Net Thickness 

(ft) 

Gas Content 

(scf/ton) 

Antrim 12,000 600-2,200 70-12 40-100 

Barnett 5,000 6,500-8,500 100-600 300-350 

Fayetteville 9,000 1,000-7,000 20-200 60-220 

Haynesville 9,000 10,500-13,500 200-300 100-330 

Marcellus 95,000 4,000-8,500 50-200 60-100 

Woodford 11,000 6,000-11,000 120-220 200-300 

12 Arthur, J., et.al., 2008, An Overview of Modern Shale Gas Development in the United States, ALL 

Consulting, 21 p., posted at: http://www.all-llc.com/publicdownloads/ALLShaleOverviewFINAL.pdf 

5 
Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

6) Does the Clean Water Act apply to discharges from Marcellus Shale Drilling 

operations? 

Yes. Natural gas drilling can result in discharges to surface waters. The discharge of this 

water is subject to requirements under the Clean Water Act (CWA). 

The CWA prohibits the discharge of pollutants by point sources into waters of the United 

States, except in compliance with certain provisions of the CWA, including section 402. 

33 U.S.C. 1311(a). Section 402 of the CWA establishes the National Pollutant Discharge 

Elimination System (“NPDES”) program, under which EPA, or an authorized state 

agency, may issue a permit allowing the discharge of pollutants into waters of the U.S. 

33 U.S.C. 1342(a). When developing effluent limitations for an NPDES permit, a permit 

writer must consider limits based on both the technology available to control the 

pollutants (i.e., technology-based effluent limits) and limits that are protective of the 

water quality standards of the receiving water (i.e., water quality-based effluent limits). 

CWA section 301, 33 U.S.C. § 1311; 40 CFR 125.3(a). The technology-based 

requirements for direct discharges from oil and gas extraction facilities into surface 

waters are found in 40 Code of Federal Regulations (CFR) Part 435 (see question7, 

below). 

In addition to direct discharges, wastewaters may be indirectly discharged into 

waters of the U.S. through sewer systems connected to publicly owned treatment works 

(POTW) that discharge directly to waters of the U.S. or by being introduced by truck or 

rail into a POTW that discharges directly. EPA regulations set standards for the 

pretreatment of wastewater introduced to a POTW including prohibiting introduction of 

wastes that interferes with, passes through or are otherwise incompatible with POTW 

operations. 33 U.S.C. § 1317(b)(1). EPA has developed other nationally applicable 

pretreatment standards under section 307(b) in its General Pretreatment Regulations for 

Existing and New Sources of Pollution (Pretreatment Regulations) at 40 C.F.R. Part 403. 

These pretreatment standards are applicable to any user of a POTW, defined as a source 

of an indirect discharge. 40 C.F.R. 403.3(h). These national pretreatment standards 

include: 1) a general prohibition and 2) specific prohibitions. 40 C.F.R. 403.5.(a)(1) and 

(b). The general prohibition prohibits any user of a POTW to introduce a pollutant into 

the POTW that will cause pass through or interference. The regulations define both pass 

through and interference. Section 307(d) of the Act prohibits discharge in violation of 

any pretreatment standard. 33 U.S.C. § 1317(d). See questions 10 and11, below, for 

additional information on pretreatment requirements. 

Wastewater may also be disposed of at centralized waste treatment facilities (CWTs). 

Technology-based standards for CWTs can be found at 40 CFR Part 437. Issues and 

requirements associated with CWTs are discussed below under questions13, 14 and 15. 

7) Do the Oil and Gas Extraction effluent guidelines for onshore operations, found 

at 40 CFR Part 435, Subpart C, apply to Marcellus Shale gas drilling? 

6
 
 

 

 

 

Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

Yes. The technology-based regulations (40 CFR Part 435, Subpart C) apply to onshore 

facilities “engaged in the production, field exploration, drilling, well completion and well 

treatment in the oil and gas extraction industry.” Gas drilling in the Marcellus Shale fits 

squarely within this applicability statement. Although, as discussed in Question 3 above, 

Marcellus Shale gas extraction may be considered “unconventional” gas extraction, the 

wastestreams generated by processes used in such extraction, such as hydraulic 

fracturing, were considered and covered by the effluent guideline. See, e.g. 41 Fed. Reg. 

44946 (Oct. 13, 1976); Technical Development Document at 22-23, 96, 137. 

Accordingly, the discharge prohibitions in 40 CFR Part 435, Subpart C, apply to 

Marcellus Shale gas extraction. 

The effluent guidelines at 40 CFR 435, Subpart C establish best practicable control 

technology currently available (BPT) requirements for onshore facilities: "there shall be 

no discharge of waste water pollutants into navigable waters from any source associated 

with production, field exploration, drilling, well completion or well treatment (i.e., 

produced water, drilling muds, drill cuttings, and produced sand)." During the issuance 

process for the guidelines, EPA identified different technologies that operators can use to 

comply with this technology-based regulation (e.g., underground injection, use of 

pits/ponds for evaporation). 

8) Since 40 CFR Part 435, Subpart C applies to the Marcellus Shale drilling activity, 

may an NPDES permit authorize onsite discharge of this wastewater to a water of 

the U.S.? 

No. Because all applicable technology based requirements must be applied in NPDES 

permits under the CWA section 402(a) and implementing regulations at 40 CFR 125.3, 

an NPDES permit issued for the drilling activity would need to be consistent with 40 

CFR Part 435, Subpart C, which states that ‘there shall be no discharge of wastewater 

pollutants into navigable waters from any source associated with production, field 

exploration, drilling, well completion, or well treatment (i.e., produced water, drilling 

muds, drill cuttings, and produced sand).” 13 

9) Are facilities subject to 40 CFR Part 435, Subpart C required to obtain an 

NPDES permit that imposes the "no discharge" requirement for the activities 

identified in Subpart C? 

No. EPA’s regulations at 40 CFR 122.21(a) require permits only for facilities that 

“discharge or propose to discharge.” Accordingly, facilities subject to a "no discharge" 

13 Note: Shale gas wells from other formations that are located west of the 98th meridian may be regulated 

under the Agriculture and Wildlife Water Use Subcategory of the Oil and Gas Extraction Category (40 

CFR Part 435, Subpart E). Produced water discharges can be authorized under that subcategory if they are 

of good enough quality to be used by agriculture or wildlife watering and actually are put to that use. The 

subcategory only allows the discharge of produced water. The discharge of all other waste streams, such as 

completion fluids, cannot be authorized under Subpart E. 

7
 
 

 

Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

limit that do not discharge or propose to discharge are not required to apply for NPDES 

permits. States can use their own authority to ensure that the no discharge requirement in 

the effluent guideline is properly applied and to ensure that operator compliance is 

demonstrated. 

Facilities subject to a zero discharge requirement may apply for permit coverage to 

qualify for the upset or bypass defense in the event of an unanticipated discharge 

resulting from an exceptional incident that otherwise would trigger a CWA Section 301 

violation for discharging without a permit. See 40 CFR 122.41(m) and (n). 

10) May Shale Gas extraction (SGE)14 wastewaters be discharged to a POTW? 

POTWs may accept SGE wastewater under certain circumstances. Process wastewater 

from such operations may be introduced to POTWs but only to the extent that such 

wastewater discharges are in compliance with all Federal, State, and local requirements 

governing the introduction of such wastewaters into the POTW. EPA has generally 

promulgated pretreatment standards that apply to wastewater introduced to POTWs along 

with effluent guideline for industrial categories. 

The current Federal regulations at 40 CFR 435, Subpart C do not include pretreatment 

standards that address the disposal of Marcellus Shale wastewater to POTWs. However, 

EPA’s General Pretreatment regulations prohibit the introduction of wastewater into a 

POTW in certain defined circumstances, including the introduction of any pollutants 

which “pass through” or cause “interference” with POTW operations. 40 CFR Part 

403.3(k)(1) defines interference as inhibiting or disrupting the POTW, its treatment 

processes or operations, or its sludge processes, use or disposal. Therefore, in addition to 

prohibiting the introduction of pollutants into the POTW that would disrupt the treatment 

process, the general regulations also prohibit the introduction of pollutants in 

concentrations that contaminate biosolids and make them inconsistent with the POTW’s 

chosen method of use or disposal. Pass through is defined at 40 CFR 403.3(p) to mean “a 

discharge which exits the POTW into waters of the United States in quantities or 

concentrations which, alone or in conjunction with a discharge or discharges from other 

sources, is a cause of a violation of any requirement of the POTW’s NPDES permit 

(including an increase in the magnitude of a violation).” All non-domestic discharges 

must comply with these requirements. See 40 CFR 403.5(a) and (b). 

Note: SGE wastewater that is discharged to a POTW from a CWT may have the same 

issues as wastewater taken directly to a POTW from a shale gas extraction well and pass 

through and interference will also need to be addressed. 

11) What requirements do POTWs need to meet in order to accept shale gas 

wastewater? 

14 SGE wastewater includes HFFW, produced water, spent drilling fluids, and spent well completion and 

treatment fluids that have result from shale gas extraction activities. 

8
 
 

 

 

Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

POTWs need to comply with their NPDES permit terms and conditions. In accordance 

with the NPDES permitting regulation at 40 CFR 122.42(b)15, permits must include 

conditions that require - - -“all POTWs must provide adequate notice to the Director 

[EPA and/or the state NPDES permitting/pretreatment authority16] of the following: 

(1) Any new introduction of pollutants into the POTW from an indirect discharger 

which would be subject to section 301 or 306 of the CWA if it were directly 

discharging those pollutants; and 

(2) Any substantial change in the volume or character of pollutants being introduced 

into that POTW by a source introducing pollutants into the POTW at the time of 

issuance of the [POTW’s] permit. 

(3) For the purposes of this paragraph, adequate notice shall include information on 

(i) the quality and quantity of effluent introduced into the POTW, and (ii) any 

anticipated impact of the change on the quantity or quality of effluent to be 

discharged from the POTW.” 

To the extent that a permit so requires, when considering the acceptance of such 

wastewater, a POTW needs to collect information from the industry on the quality and 

quantity of the SGE wastewater proposed to be introduced to the POTW and assess the 

potential impact to the POTW if the POTW were to accept the wastewater. For SGE 

wastewater, that discharge characterization should include the concentrations of total 

dissolved solids, specific ions, such as chlorides and sulfate, specific radionuclides, 

metals, and other pollutants that could reasonably be expected to be present in wastewater 

from a well. In addition to the ions, radionuclides, and metals that can be expected to be 

present in wastewater produced from a well, the characterization should include all 

chemicals used in well drilling, completions, treatment, workover, or production, that 

could reasonably be expected to be present in wastewater. Pursuant to the permit, this 

information must generally be reported to EPA and/or the State program before the 

POTW may accept the HFFW. “Adequate notice” is meant to provide the EPA (or the 

state NPDES permitting authority) with enough time to determine if the POTW NPDES 

permit needs to be modified in order to address potential effects due to the potential new 

indirect discharger. In cases such as Pennsylvania, where the state is the permitting 

authority and EPA is the approval authority for pretreatment, the POTW must submit the 

required information to both agencies. In addition to this notification, all industrial user 

discharges to a POTW must comply with the specific prohibitions of 40 CFR 403.5(b), 

any applicable categorical standards, and any state and local limits. 

EPA Regions, in their oversight role, should work with authorized States to ensure that 

NPDES permits for POTWs include the pretreatment notification requirements and 

15Applicable to State NPDES programs, see 40 CFR 123.25. 16 Under 40 CFR 122.2, “Directormeans the Regional Administrator or the State Director, as the context 

requires, or an authorized representartive. When there is no “approved State program” and there is an EPA 

administered program, “Director” means the Regional Administrator.” Where a State not have an 

approved State pretreatment program, the Regional Administrator is the Director of the pretreatment 

program under this provision. 

9
 
 

 

 

 

Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

definitions of 40 CFR 122.2, 122.42(b), and 403.5(b). By including those requirements 

in permits, the permitting authorities will help prevent potential oversights of the 

notification requirements by POTW operators. 

EPA recognizes that POTW operations vary due to site-specific factors. All POTWs with 

approved pretreatment programs, and all other POTWs designated by EPA or the state as 

having experienced or having the potential to experience pass through or interference, 

must develop technically-based local limits where necessary to comply with the general 

pretreatment standards. See 40 CFR 403.5(c) & 403.8(a). To assist in this evaluation, 

EPA has issued guidance on establishing local limits: Local Limits Development 

Guidance, EPA-833-R-04-002A, July 2004.17 18 

12) What are the main potential pollutants of concern for POTWs accepting SGE 

wastewaters? 

Constituents in SGE wastewater such as total dissolved solids (TDS) have been found to 

be present at concentrations ranging from 280 mg/l to 345,000 mg/l.19 Chloride has been 

reported in concentrations up to 196,000 mg/l.20 TDS is not significantly removed by 

most conventional POTW treatment systems; therefore, pretreatment of the wastewater 

would be required prior to discharge to the POTW. However, very little comprehensive 

data have been collected nationwide on TDS treatment capability at POTWs. Common 

constituents of TDS include calcium and magnesium (also a measure of “hardness”), 

phosphates, nitrates, sodium, potassium, sulfates, chloride, and even barium, cadmium, 

and copper. A literature data search revealed that some of these individual constituents 

of TDS may result in POTW process inhibition in activated sludge, nitrification, and 

anaerobic digestion processes. POTWs may exhibit these process inhibitions from these 

individual constituents at concentrations that are several magnitudes lower than the 

composite TDS found in SGE wastewater (example: sulfate at 400-1000 mg/l disrupting 

anaerobic digestion processes; chloride at 180 mg/l disrupting nitrification processes21). 

High concentrations of chlorides, such as in Marcellus SGE wastewater, can disrupt 

biological treatment units. Some POTWs that had previously accepted oil and gas 

extraction waste through their pretreatment programs experienced operational problems 

due to high concentrations and spikes in concentrations of TDS.22 In addition, some of 

the constituents in oil and gas extraction waste, such as metals, can precipitate during the 

17Available at: http://cfpub.epa.gov/npdes/home.cfm?program_id=3 18 Guidance Manual for the Control of Wastes Hauled to Publicly owned treatment works” EPA 833-B-98-

003, September 1999.

19 Haynes, Thomas, 2009, Sampling and Analysis of Water Streams Associated with the Development of 

Marcellus Shale Gas, Gas Technology Institute, Des Plaines, IL. 

20 NYSDEC, 2009, Supplemental Generic Environmental Statement on the Oil, Gas, and Solution Mining 

Regulatory Program, Well Permit Issuance for Horizontal Drilling and High-Volume Fracturing to 

Develop the Marcellus Shale and Other Low Permeability Gas Reservoirs, Appendix 13, available at: 

http://www.dec.ny.gov/energy/58440.html

21 USEPA, Local Limits Development Guidance Appendices, EPA 833-R-04-002B, July, 2004 

22 Record of communications between Scott Wilson (EPA, OWM), Morgan City, LA pretreatment 

program, and Ted Palit (EPA Region 6) 

10
 
Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

treatment process and contaminate biosolids which may require expensive 

decontamination of biosolids drying beds or change the chosen method of use or disposal. 

Bromide, which can be present in SGE wastewater in significant concentrations, has the 

potential to be present in POTW effluent as a disinfection byproduct and may cause an 

increase in whole effluent toxicity21. 

Because there is a significant possibility that SGE wastewater may “pass through” the 

POTW, causing the POTW to violate its permit, cause “interference” with the POTW’s 

operation, or contamination of biosolids, acceptance of the waste is not advisable unless 

it’s effects on the treatment system are well understood and the wastewater is not 

reasonably expected to cause pass through or interference. POTWs cannot accept 

Marcellus wastewater if acceptance of the wastewater would result in violations of the 

POTW’s permit, the POTW’s requirement under 40 CFR 403.5(c) to develop and 

enforce local limits to implement the general and specific prohibitions of 403.5(a)(1) and 

(b), or contamination that interferes or disrupts biosolids processes, uses, or disposal. 

NPDES permits for discharges from POTWs to water of the U.S. also must meet 

applicable water quality-based requirements that are discussed in more detail in question 

number 21. 

Radionuclides in Marcellus SGE wastewater also pose a challenge for POTWs. 

Radionuclides are discussed below in the response to question number 19. 

These same pollutants may be of concern to POTWs that accept wastewater from CWTs 

that themselves accept SGE wastewaters. Many CWTs may not effectively treat SGE 

wastewater. Appropriate limits and pretreatment requirements will need to be developed 

by the permitting authority and the pretreatment control authority. 

13) Could SGE wastewater be transferred to a CWT facility for treatment and 

discharge? 

Yes. Although the direct discharge of wastewater from drilling operations is not 

authorized, the wastewater may be transported to a CWTs for treatment and subsequent 

discharge. Discharges from a CWT are subject to the effluent limitations guidelines and 

standards established under 40 CFR Part 437. 

Additional limits may be required to address pollutants in the wastewater that were not 

considered in developing the CWT effluent guideline. For such pollutants, EPA’s 

NPDES regulations require that permit writers include technology-based limits developed 

on a case-by-case, “best professional judgment” (BPJ) basis. See 40 CFR §125.3(c)(3) 

(“Where promulgated effluent limitations guidelines only apply to certain aspects of the 

discharger’s operation, or to certain pollutants, other aspects or activities are subject to 

regulation on a case by case basis...”). In developing technology-based BPJ limits, the 

permit writer must consider the factors specified in 40 CFR 125.3(d), the same factors 

that EPA considers in establishing categorical effluent guidelines. 

11
 
 

 

 

Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

In developing the CWT effluent guideline, EPA did not evaluate certain 

pollutants that are likely to be present in SGE wastewater, such as radionuclides. 

Consequently, the permitting authority will need to develop best professional judgment 

technology based effluent limits to address those pollutants identified in the effluent but 

not considered by the CWT Effluent Guidelines and incorporate these limits in the 

CWT’s NPDES permit. 

For some pollutants, such as total dissolved solids (TDS), EPA considered, but did not 

establish, pollutant limitations in the effluent guidelines. TDS levels in Marcellus Shale 

wastewaters have been measured to be present in concentrations up to 345,000 mg/l20. 

High concentrations of TDS will require advanced waste water treatment, such as 

distillation, and may cause scaling which requires frequent cleaning of equipment10. In 

addition to any applicable technology-based requirements, NPDES permits for discharges 

from CWTs to waters of the U.S. also must meet applicable water quality-based 

permitting requirements. See question number 21 for more detail on water quality 

permitting. 

14) What Subpart of 40 CFR Part 437 should be used for the Marcellus Shale 

wastewater? 

40 CFR Part 437 includes three subparts to address different industries that may dispose 

of wastewater in a CWT. Those subparts include: Metals Treatment and Recovery, Oils 

Treatment and Recovery, and Organics Treatment and Recovery. When the Effluent 

Limitations Guidelines were promulgated, EPA understood that industrial wastes would 

not always clearly fit under one of the subcategories. To address the issue of 

categorization of wastewater, EPA developed guidance for permit writers to determine 

which subpart of the 40 CFR Part 437 ELGs best addresses waste accepted by a CWT.23 

Chapter 5 of the guidance lists different waste sources that were examined during 

development of the ELG and were determined to best be addressed under each subpart. 

For waste sources not listed, the guidance contains additional criteria based on oil and 

grease content and metals concentrations that can be used for this determination. 

Available data for Marcellus shale extraction waste water show that the waste does not fit 

under the Oils or Metals Subcategories. The guidance suggests regulating waste under 

the Organics Subcategory for cases where it does not fit under the other Subcategories.23 

However, this determination was made only using Marcellus shale waste data. CWTs are 

expected to receive waste containing different pollutant types and concentrations 

originating from a variety of sources.24 The permit writer will need to reexamine this 

determination based on site specific information when drafting a permit. 

15) How is transportation of waste by pipeline addressed by the CWT regulations? 

23 USEPA, Small Entity Compliance Guide, Centralized Waste Treatment Effluent Limitations Guidelines 

and Pretreatment Standards (40 CFR Part 437), EPA-821-B-01-003, June, 2001, posted online at: 

http://www.epa.gov/waterscience/guide/cwt/CWTcompliance_guide.pdf 24 64 FR 2286, January 13, 1999 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

CWTs may accept wastewater transported to the CWT via pipeline. The CWT would be 

subject to applicable limitations imposed on its discharge through its NPDES permit or 

pretreatment program control mechanism. The CWT ELGs are only applicable to CWT 

discharges of treated piped wastewater if the treated piped wastewater is comingled with 

other wastewater covered by the CWT ELG. If the piped wastes are not commingled, the 

permitting authority will need to develop best professional judgment technology based 

effluent limits for discharges of piped wastewater from the CWT. The CWT regulations 

at 40 CFR 437.1(b)(3) address waste received via pipeline from offsite as follows: 

“(b) This part does not apply to the following discharges of wastewater from a 

CWT facility: 

. 

. 

. 

(3) Wastewater from the treatment of wastes received from off-site via conduit 

(e.g., pipelines, channels, ditches, trenches, etc.) from the facility that generates the 

wastes unless the resulting wastewaters are commingled with other wastewaters 

subject to this provision. A facility that acts as a waste collection or consolidation 

center is not a facility that generates wastes.” 

The requirement was included in the regulations to address wastes that are not as variable 

as those that were typically found to be treated at the CWT facilities studied during 

development of the ELGs. Unlike traditional CWT facilities, pipeline customers and 

wastewater sources do not change and are limited by the physical and 

monetary constraints associated with pipelines. In addressing this issue, the preamble to 

the proposed regulation states: 

“EPA has concluded that the effluent limitations and pretreatment standards for 

centralized waste treatment facilities should not apply to such pipeline treatment 

facilities because their wastes differ fundamentally from those received at 

centralized waste treatment facilities. In large part, the waste streams received at 

centralized waste treatment facilities are more concentrated and variable, including 

sludges, tank bottoms, off-spec products, and process residuals. The limitations and 

standards developed for centralized waste treatment facilities, in turn, reflect the 

types of waste streams being treated and are necessarily different from those 

promulgated for discharges resulting from the treatment of process wastewater for 

categorical industries.”25 

This issue was also addressed in the final rule which further clarified that waste delivered 

via pipeline would have a more uniform flow rate and with a relatively consistent 

pollutant concentration. Wastes delivered solely by pipeline would be more consistent 

with a traditional manufacturing facility that did not accept waste from a variety of 

different sources.26 

25 60 FR 5463 - 5506, January 27, 1995 

26 65 FR 81241 - 81313, December 22, 2000 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

16) What potential hazardous waste issues apply to the acceptance of oil & gas 

extraction wastewater at a POTW or CWT via truck, train, or dedicated pipe? 

Waste generated by activities associated with the exploration, development, and 

production of crude oil or natural gas, at primary field operations, are exempt from 

regulation under RCRA Subtitle C. See 40 CFR 261.4(b)(5). See also the July 1988 

Regulatory Determination (53 FR 25466) and the March 1993 clarification of the 

Regulatory Determination (58 FR 15284) at 

http://www.epa.gov/epawaste/nonhaz/industrial/special/oil/index.htm. These wastes 

include drilling fluids, produced water, and other wastes associated with the exploration, 

development, or production of crude oil or natural gas. According to the legislative 

history, the term “other wastes associated” specifically includes waste materials 

intrinsically derived from primary field operations associated with the exploration, 

development, or production of crude oil and natural gas (e.g., spent hydraulic fracturing 

fluids). The exemption does not apply to excess supplies, such as unused drilling fluids 

or treatment chemicals. POTWs or CWTs receiving exempt oil and gas extraction 

wastewaters would not be receiving hazardous wastes and thus would not need to meet 

RCRA hazardous waste requirements, including RCRA permit or permit-by-rule 

requirements. For additional clarity on this issue regarding the status of oil and gas 

exploration and production wastes that are exempt from RCRA subtitle C regulations, 

see: http://www.epa.gov/epawaste/nonhaz/industrial/special/oil/oil-gas.pdf. 

17) Does Part 435 Subpart G apply to the treatment and discharge of wastewaters 

from the Onshore Subcategory if those wastewaters were sent off-site for treatment 

and discharge at a facility covered by another ELG, such as a Centralized Waste 

Treatment (CWT) facility under Part 437? 

No. EPA promulgated Subpart G, in part, to eliminate the practice of sending 

wastewaters from one Part 435 subcategory to another to take advantage of less stringent 

discharge requirements. Thus, for example, a facility regulated by the Coastal 

subcategory limitations located near a facility subject to the Offshore subcategory 

limitations might have sent its wastewater for treatment at the Offshore facility in order to 

get around the no discharge requirements. Under Subpart G, even if the Coastal 

subcategory facility transports its wastewater for treatment and/or disposal at the 

Offshore subcategory facility, the discharge would still be subject to the more stringent 

no discharge limitations for discharge to navigable waters. 

If, however, an Onshore subcategory facility transports its wastewaters to an off-site 

centralized waste treatment facility, Subpart G would not apply. In this case, the 

wastewater discharge would be regulated by Part 437. See 40 CFR §437.1 (providing 

that Part 437 applies to “[t]reatment and recovery of ... industrial metal-bearing waters, 

oily wastes and organic-bearing wastes received from off-site”). In this scenario, 

transferring wastewaters off-site for authorized disposal meets the no discharge 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

requirement in Part 435 Subpart C ("no discharge of waste water pollutants into 

navigable waters"). 

18) What is the definition of “off-site” in regard to SGE wastewater treated at 

CWTs? 

From 40 CFR 122.2: 

Site means the land or water area where any “facility or activity” is physically located or 

conducted, including adjacent land used in connection with the facility or activity. 

Facility or activity means any NPDES “point source” or any other facility or activity 

(including land or appurtenances thereto) that is subject to regulation under the NPDES 

program. 

For gas drilling activities, the land identified in the drilling permit; including the locations 

of wells, access roads, lease areas, and any lands where the facility is conducting its 

exploratory, development or production activities, or adjacent lands used in connection 

with the facility or activity, would constitute the site. Land that is outside the boundaries 

of that area is considered to be “off-site.” (see also 40 CFR 437.2(n) 

19) The Marcellus Shale is often referred to as a radioactive black shale in 

literature27. Are radionuclides an issue of concern with natural gas extraction and 

wastewater disposal? 

Radionuclides associated with oil and gas extraction, also referred to as Naturally 

Occurring Radioactive Material (NORM), are a long standing waste management issue. 

Many states have addressed the issues associated with NORM in oil and gas extraction 

through their regulatory programs.28,30,6 Radionuclides often exist in low concentrations 

in oil and gas waste and have been found to form deposits over time in piping and 

equipment. The issues commonly related to radionuclides in oil and gas extraction waste 

are decontamination of equipment and human health risk for workers.29,30 Several states 

with extensive oil and gas extraction activity have also developed requirements for 

disposal facilities that accept radionuclide contaminated waste.28 Since oil and gas 

extraction waste is not discharged in many states, water quality and human health issues 

associated with discharges under NPDES permits have not been been extensively 

examined. 

27 Milici, R.C. and C.S. Sweeney, 2006, Assessment of Appalachian Basin Oil amd Gas Resources: 

Devonian Shale – Middle and Upper Paleozoic Total Petroleum System, Open File Report Series 2006-

1237, U.S. Department of Interior, USGS.

28 http://norm.iogcc.state.ok.us/reg/dsp_statereg.cfm 

29 USGS, 1999, Naturally Occurring Radioactive Materials (NORM) in Produced Water and Oil Field 

Equipment – an Issue for the Energy Industry, USGS Fact Sheet FS-142-99 30 Railroad Commission of Texas, NORM – Naturally Occurring Radioactive Material, posted at: 

http://www.rrc.state.tx.us/environmental/publications/norm.php 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

The Marcellus Shale has been found to contain NORM that can be in fairly high 

concentrations in oil and gas extraction wastewater. Radium 226 has been found to be 

present in concentrations up to 16,030 pCi/l in Marcellus Shale produced water.31 HFFW 

from the Marcellus Shale has not been monitored extensively for radionuclides; however, 

Alpha particles have been found to be present at concentrations up to 18,950 pCi/l.31 

Those radionuclide concentrations exceed the drinking water Maximum Contaminant 

Levels of 5 pCi/L for Radium 266 and 15 pCi/l for Alpha particles. Although few studies 

are available that would help to understand the issue of NORM in POTW or CWT 

effluent, EPA is working with Pennsylvania to gather information and determine whether 

additional permit limits are needed to protect downstream drinking water supplies. 

Based on existing information on NORM associated with oil and gas extraction, it 

appears that care should be taken to address impacts to treatment facilities, such as scale 

buildup in equipment and contamination of sludge [biosolids]. Contamination of 

biosolids at POTWs that requires a change of disposal practice (e.g., radioactivity, etc.) is 

considered to be interference under the pretreatment program. See 40 CFR 403.3(k)(2) 

and 403.5(a)(1). 

The discharge of shale gas wastewater from POTWs or CWTs has the potential to result 

in a discharge of radioactive contaminants. Such discharges must be characterized to 

determine whether reasonable potential exists for impacts to downstream Public Water 

Systems and other applicable water quality standards. If so, appropriate permit limits 

must be established. 

When the 40 CFR Part 437 effluent limitations guidelines were developed, EPA found 

that CWTs were not designed to remove radionuclides. Many CWTs also discharge to 

POTWs rather than directly discharging to Waters of the United States. The same issues 

that apply to POTWs accepting wastewater from gas well operators also apply to 

wastewater accepted from CWTs32. 

20) Can any of the Marcellus Shale gas extraction activity fall under Part 435 

Subpart F – Stripper Subcategory? 

No. The Stripper Subcategory is clearly limited to onshore facilities which produce 10 

barrels per well per calendar day or less of crude oil. The Marcellus Shale activity is gas 

extraction. 

31 NYSDEC, 2009, Supplemental Generic Environmental Statement on the Oil, Gas, and Solution Mining 

Regulatory Program, Well Permit Issuance for Horizontal Drilling and High-Volume Fracturing to 

Develop the Marcellus Shale and Other Low Permeability Gas Reservoirs, Appendix 13, available at: 

http://www.dec.ny.gov/energy/58440.html 

32 Development Document for the CWT Point Source Category, Final Rule: Development 

Document, USEPA, Washington, DC, 2000, available online at:. 

http://water.epa.gov/scitech/wastetech/guide/treatment/develop_index.cfm 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

21) What water quality-based requirements may apply in NPDES permits for 

discharges of Marcellus Shale Wastewater from POTWs and CWTs to waters of the 

U.S.? 

EPA’s NPDES regulations also require permit writers to include any more stringent 

requirements necessary to meet applicable water quality standards. Specifically, the 

regulations require limits to control all discharges that have the reasonable potential to 

cause or contribute to exceedences of water quality standards. 40 CFR 122.44(d)(1)(i). 

Accordingly, where, after application of technology-based effluent limits, the discharge 

of Marcellus Shale wastewater has a reasonable potential to cause or contribute to 

exceedences of water quality standards, the permit writer will need to develop water 

quality based effluent limits (WQBELs) for the POTWs or CWT’s NPDES permit to 

protect water quality. Additional requirements may be needed to comply with other State 

regulations.33 

WQBELs may be needed for TDS, in particular, where discharges of the pollutant from 

CWTs or POTWs have the reasonable potential to exceed state numeric or narrative 

water quality criteria. Since few states have established numeric water quality criteria for 

TDS, permitting authorities may need to develop a numeric translator to protect the 

state’s narrative water quality criteria. In the Marcellus Shale wastewater, chloride 

typically constitutes about 50% of the total makeup of Total Dissolved Solids (TDS) in a 

sample. Elevated chloride levels can interfere with an aquatic organism’s ability to 

maintain osmotic balance/control with its environment, as well as cause other effects. 

Some states have applicable numeric water quality criteria for chloride. Where a state 

has a numeric criterion, NPDES permit regulations require that permitting authorities 

assess reasonable potential and established permit limits where necessary to protect water 

quality based on the applicable numeric criterion. Where a state has not developed a 

numeric criterion for chloride, EPA recommends that permitting authorities use a 

numeric translation of the applicable narrative criterion pursuant to 40 CFR 

122.44(d)(1)(vi). In developing such translation, EPA recommends using EPA’s current 

304(a) national recommended criteria for chloride for protection of aquatic life. These 

criteria were published by EPA in 1988. The current national criteria for Chloride are: 

acute aquatic life criteria of 860 mg/l, and chronic aquatic life criteria of 230 mg/L. EPA 

is currently in the process of updating these recommended criteria to reflect the latest 

science. That update is expected to be proposed by the end of 2011 and finalized in 

2012. 

22) Does EPA’s storm water definition at 40 CFR 122.26(b)(14)(iii) include 

discharges from a natural gas drilling operation? 

40 CFR 122.26(b)(14)(iii) does include natural gas activities, but only to the extent that 

they require permit coverage as described in 122.26(a)(2)(ii) and 122.26(c)(1)(iii). 

33 PA Environmental Quality Board, Proposed Rulemaking, 39 Pa.B. 64671, November 7, 2009 

Available at: http://www.pabulletin.com/secure/data/vol39/39-45/2065.html 

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Attachment to memorandum from James Hanlon, Director of EPA’s Office of Wastewater Management to the EPA 

Regions titled, “Natural Gas Drilling in the Marcellus Shale under the NPDES Program” 

March 16, 2011 

In general, the Director may not require a permit for discharges of storm water from any 

field activities or operations associated with oil and gas exploration, production, 

processing, or treatment operations or transmission facilities, including activities 

necessary to prepare a site for drilling and for the movement and placement of drilling 

equipment, whether or not such field activities or operations may be considered to be 

construction activities.34 

Exceptions to the above general exemption may be found at 122.26(c)(1)(iii), which 

states: “The operator of an existing or new discharge composed entirely of storm water 

from an oil or gas exploration, production, processing, or treatment operation, or 

transmission facility is not required to submit a permit application in accordance with 

paragraph (c)(1)(i) of this section, unless the facility: 

(A) Has had a discharge of storm water resulting in the discharge of a reportable 

quantity for which notification is or was required pursuant to 40 CFR 117.21 or 

40 CFR 302.6 at anytime since November 16, 1987; or 

(B) Has had a discharge of storm water resulting in the discharge of a reportable 

quantity for which notification is or was required pursuant to 40 CFR 110.6 at 

any time since November 16, 1987; or 

(C) Contributes to a violation of a water quality standard.” 

While oil and gas-related construction is subject to the conditional exemption, operators 

should still implement best management practices when undertaking earth disturbing 

activities to prevent discharging pollutants, including sediment, that would cause or 

contribute to water quality violation, and which would trigger storm water permitting 

requirements. 

General Note 

These Q&As provide advice on how to issue National Pollutant Discharge Elimination 

System permits for discharges from natural gas drilling in the Marcellus Shale. These 

Q&As do not impose legally binding requirements on EPA, states, tribes, other 

regulatory authorities, or the regulated community, and may not apply to a particular 

situation based upon the circumstances. EPA, state, tribal and other decision makers 

retain the discretion to adopt approaches on a case-by-case basis that differ from those 

provided in the Q&As where appropriate. EPA may update these Q&As in the future as 

better information becomes available. 

34 See CWA section 402(l)(2) and CWA section 502(24) as amended by the Energy Policy Act of 2005 

section 323 

18