NACWA’s Comments on EPA Reconsideration of Sewage Sludge Incineration 

August 14, 2006 

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August 14, 2006 

 

 

EPA Docket Center (EPA/DC) 

United States Environmental Protection Agency 

U.S. EPA (MD-6102T) 

1200 Pennsylvania Avenue NW 

Washington, D.C. 20460

Re: Comments of the National Association of Clean Water Agencies (NACWA) on U.S. 

EPA’s Standards of Performance for New Stationary Sources and Emission Guidelines 

for Existing Sources: Other Solid Waste Incineration Units: Reconsideration 

Attention Docket ID No. EPA-HQ-OAR-2003-0156 

Dear Sir or Madam: 

These comments are submitted on behalf of the National Association of Clean Water Agencies

(“NACWA”)1

 in support of the United States Environmental Protection Agency’s (“U.S. EPA” or the “Agency”) 

determination that sewage sludge incinerators (“SSIs”) are not subject to regulation as other solid waste 

incineration units (“OSWIs”) pursuant to Section 129 of the Clean Air Act (“CAA”). NACWA submits these 

comments in response to U.S. EPA’s June 28, 2006 notice of its reconsideration of, and requests for public 

comments on, the issue of whether SSIs should be excluded from the CAA § 129 regulations for OSWIs 

promulgated on December 16, 2005 (the “final OSWI rule”).2

 

While NACWA understands and supports U.S. EPA’s efforts to ensure a full opportunity for public 

comment in its rulemaking process, NACWA respectfully submits that U.S. EPA has already properly 

determined — after thorough evaluation and analysis — that SSIs are not subject to regulation as OSWIs under 

CAA § 129. This determination is the result of 10 years of notice and comment rulemaking, judicial challenges 

and negotiations involving all interested parties. Additional public comment during reconsideration is not 

expected to generate new information. As such, this process should only serve to reinforce U.S. EPA’s decision

to exclude SSIs from the final OSWI rule to preserve incineration as a safe, viable, and cost-effective biosolids 

(or “sewage sludge”) management practice consistent with the intent of Congress and U.S. EPA. Accordingly, 

 

1

 NACWA (formerly the Association of Metropolitan Sewerage Agencies or AMSA) represents the interests of nearly 300 

publicly owned wastewater treatment agencies or works (POTWs) nationwide. NACWA's members serve the majority of 

the sewered population in the United States, and collectively treat and reclaim more than 18 billion gallons of wastewater 

each day. 

2 See Standards of Performance for New Stationary Sources and Emissions Guidelines for Existing Sources: Other Solid Waste 

Incineration Units: Reconsideration, 71 Fed. Reg. 36726 (June 28, 2006); Standards of Performance for New Stationary Sources and 

Emission Guidelines for Existing Sources: Other Solid Waste Incineration Units; Final Rule, 70 Fed. Reg. 74870 (Dec. 16, 2005). 
NACWA’s Comments on EPA Reconsideration of Sewage Sludge Incineration 

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NACWA strongly supports U.S. EPA’s decision not to include SSIs among the categories of OSWIs regulated 

under the final OSWI rule.

GENERAL COMMENTS 

 

1. NACWA’s Public Agency Members Rely on Incineration as a Safe, Effective, and 

Federally-Approved Biosolids Management Practice. 

NACWA represents the interests of the country’s wastewater treatment agencies, true environmental 

practitioners that serve the majority of the sewered population in the United States, and collectively treat and 

reclaim more than 18 billion gallons of wastewater each day. For over thirty-six years, NACWA has maintained 

a leadership role in issues affecting POTWs, and has been at the forefront of the development and 

implementation of scientifically-based, technically-sound, and cost-effective environmental programs for 

protecting public and ecosystem health. 

The approximately 16,000 POTWs located in the United States utilize U.S. EPA-approved methods to 

manage the estimated eight million dry metric tons of biosolids that are generated annually as a product of 

their wastewater treatment activities. These approved methods include incineration. As U.S. EPA has 

repeatedly stated, the Agency does not have a position regarding the biosolids management options most 

suitable for a particular community and, instead, recognizes that such choices are local decisions (subject, of 

course, to applicable federal and state regulations).3

 U.S. EPA also stated that it continues to support 

incineration (as well as land application, and disposal at municipal solid waste landfills and disposal at surface 

disposal sites) as a viable option for the management of biosolids.4

The incineration of biosolids results in an 80-95% reduction in volume, the effective destruction of 

pathogens, the degradation of toxic organic compounds, and the production of a sanitary, odorless, and nonhazardous by-product (i.e., ash). Incineration is thus an important, safe, and effective component of the 

biosolids management practices utilized by POTWs. U.S. EPA has estimated that, in 1998, up to 22% of 

biosolids generated at POTWs located within the United States is disposed of through incineration.5

 Using this 

and other available surveys, NACWA has estimated that 17% of the biosolids generated by U.S. POTWs is 

presently managed through incineration. 

 

3

 Letter from Benjamin H. Grumbles, then Acting Assistant Administrator for the Office of Water, U.S. EPA, to Scott 

Hassett, Secretary of Wisconsin Department of Natural Resources dated October 7, 2004 (attached hereto at Attachment B) 

(“we do not believe that EPA should be involved in determining the biosolids management practices most suitable for a 

particular community”); James A. Hanlon, Director of U.S. EPA Office of Wastewater Management, to Greg Kester, State of 

Wisconsin Department of Environmental Resources dated September 20, 2004 (attached hereto at Attachment C). 

4 See id.

5 See United States Environmental Protection Agency, Biosolids Generation, Use, and Disposal in the United States 26-27 (1999) 

(EPA No. 530R-99-009), available at www.epa.gov/epaoswer/non-hw/compost/biosolid.pdf.
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2. U.S. EPA’s Decision Not to Regulate SSIs under CAA § 129 was Reached After 

Thorough and Complete Evaluation of the Issue. 

Given the importance of incineration to NACWA members and the non-member POTWs that practice 

incineration, NACWA has been an active participant in U.S. EPA’s evaluation of the emissions from sewage 

sludge incineration and the Agency’s regulatory actions related to SSIs. During this process, NACWA has 

cooperatively provided U.S. EPA with data and other information about its members’ biosolids incineration 

activities and the level and types of pollutants released during this process in order to assist the Agency in 

evaluating the applicability of CAA §§ 129, 112(d), and 112(k). NACWA has also been heavily involved in U.S. 

EPA’s development of the existing regulations under the CAA and Clean Water Act (“CWA”) pertaining to 

emissions from POTWs and SSIs, including 40 CFR Part 503 (Standards for the Disposal of Sewage Sludge) and 

40 CFR Part 63, Subpart VVV (National Emissions Standards for Hazardous Air Pollutants: Publicly Owned 

Treatment Works). 

NACWA’s history of involvement in this specific regulatory issue spans nearly a decade, beginning with 

U.S. EPA’s notice of its initial intent to include SSIs as a category of OSWIs under CAA § 129(a)(1)(E).6

 In 

response to U.S. EPA’s notice, NACWA (then named the Association of Metropolitan Sewerage Agencies or 

AMSA) and many of its individual member agencies provided extensive comments to U.S. EPA, which explained 

in detail the many reasons that SSIs should not be included as OSWIs under CAA § 129. As discussed in 

NACWA’s March 17, 1997 comment letter, these reasons include: 

(i) The regulation of SSIs under Section 129 is beyond the U.S. EPA’s statutory authority; 

(ii) U.S. EPA’s contemplated method for establishing Maximum Achievable Control 

Technology (“MACT”) Standards for SSIs under Section 129 would lead to results contrary 

to the intent of Congress – i.e., it would lead to the elimination of biosolids incineration (a 

safe, viable and cost-effective sewage sludge management practice); 

(iii) The properties of biosolids are very different from those of hazardous, medical or 

municipal solid wastes. Thus, SSIs should not be subject to the same type of regulations 

imposed on these other types of incinerators; 

(iv) The emissions from SSIs are already subject to comprehensive and stringent 

regulations that are protective of human health and the environment. U.S. EPA has 

determined that, through compliance with the Part 503 limits and management practices 

under the CWA, emissions from SSIs do not adversely affect human health and the 

environment; and

(v) Accordingly, no environmental benefit will be realized from the expensive and/or 

infeasible control measures that Section 129 will impose, and there may be a net loss of 

environmental benefit. 

 

6 New Source Performance Standards and Emissions Guidelines: Sewage Sludge Incinerators, 62 Fed. Reg. 1868 (Jan. 14, 1997).
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NACWA’s March 17, 1997 comments to U.S. EPA remain fully applicable to the issues raised by U.S. EPA’s 

current reconsideration of the final OSWI rule, and are accordingly attached hereto as Attachment A and 

incorporated by reference. 

Following the close of the public comment period in 1997, U.S. EPA evaluated NACWA’s and other 

interested parties’ comments, conducted legal analysis, and further studied SSIs. This process was completed, 

in part, through the Industrial Combustion Coordinated Rulemaking Advisory Committee convened under the 

Federal Advisory Committee Act (“FACA”) on which NACWA member agencies participated extensively and 

provided their technical expertise and experience. During this three year process, NACWA and its member 

agencies provided U.S. EPA with significant information regarding its members’ biosolids incineration 

activities and the emissions released during this process. After U.S. EPA’s full evaluation and consideration of 

the applicability of Section 129 to SSIs, U.S. EPA properly determined that SSIs should not be regulated under 

CAA § 129 because they do not constitute “solid waste incineration units.” U.S. EPA accordingly announced 

that decision in its semiannual regulatory agenda for 2000.7

 U.S. EPA reiterated this determination when it 

announced in November 2000 that the Agency would complete the CAA § 129 regulations for OSWIs by 

November 15, 2005, and confirmed the sources that would be covered by the OSWI rulemaking – tellingly, SSIs 

were not among those sources.8

Further demonstrating its intent not to regulate SSIs under CAA § 129, U.S. EPA provided an express 

exemption from the final CAA § 129 rules promulgated in December 2000 for commercial and industrial solid 

waste incinerators. SSIs complying with 40 CFR Part 60, Subpart O (Standards of Performance for Sewage 

Treatment Plants) are expressly excluded from this incinerator rule.9

 

 

 

7

 United States Environmental Protection Agency, Unified Agenda, April 2000 Agenda of Regulatory and Deregulatory Actions, 65 

Fed. Reg. 23430, 23460 (April 24, 2000). In the regulatory agenda, U.S. EPA expressly stated: 

The Agency has decided not to regulate sewage sludge incinerators as a category under Section 129 of the 

Clean Air Act. Section 129(a)(1) requires the Agency to establish standards under Section 129 for each 

category of “solid waste incineration units.” “Solid waste incineration unit” is defined as a “distinct 

operating unit of any facility which combusts any solid waste material from commercial or industrial 

establishments or the general public (including single and multiple residences, hotels, or motels).” The 

Agency believes that sewage sludge generated by publicly-owned treatment works (POTWs) and 

combusted in SSIs is “solid waste.” However, this sludge is from a municipal source, and not from 

“commercial or industrial establishments or the general public.” Therefore, SSIs that combust this sludge are 

not “solid waste incineration units” and section 129 does not apply to them. Virtually all of the SSIs that would be 

candidates for regulation combust sludge from POTWs, and thus are not covered under Section 129. 

8 Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources for Other Solid Waste Incinerator 

Units, 65 Fed. Reg. 67357 (Nov. 9, 2000).

9 Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Commercial and Industrial Solid 

Waste Incineration Units, 65 Fed. Reg. 75338, 75351 (Dec. 1, 2000); see also 40 CFR § 60.2020(m). 
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NACWA also intervened in support of U.S. EPA in the litigation initiated by Sierra Club (the petitioner 

for this reconsideration proceeding) in federal court in 2001 to compel the Agency to issue performance 

standards and other requirements under CAA § 129 for OSWIs.10 In the legal filings and discussions in this 

lawsuit, NACWA again explained that U.S. EPA had already made a determination not to regulate SSIs under 

CAA § 129 and, therefore, the Agency was not required to promulgate performance standards or other 

requirements for SSIs under that section of the CAA. While this litigation resulted in a settlement in which 

U.S. EPA agreed to establish a schedule for promulgating the standards for OSWIs under CAA § 129, the 

settlement did not alter or affect the Agency’s earlier determination that SSIs are not an OSWI category subject 

to regulation under Section 129(a)(1)(E). 

U.S. EPA accordingly did not include SSIs among the categories of OSWIs in the proposed OSWI rule in 

December 2004 or in the final rule in December 2005.11 U.S. EPA’s basis for doing so was clear — the Agency 

had already made clear that it determined that SSIs were not a category of OSWIs subject to regulation under 

CAA § 129. While Sierra Club contends in its petition for reconsideration that there was no opportunity to 

comment on U.S. EPA’s decision not to include SSIs in the OSWI proposed rulemaking, EarthJustice did in fact 

comment on this specific issue in its comment letter on the proposed OSWI rule.12 In response to EarthJustice’s 

comment, U.S. EPA again articulated that, as early as April 2000, the Agency indicated that it no longer 

intended to regulate SSIs under CAA § 129 and made clear that it intended to instead regulate SSIs under CAA 

§ 112 to the extent that additional regulation beyond 40 CFR Part 503 is required.13

Given this extensive regulatory history, NACWA believes the various rulemaking activities taken by U.S. 

EPA over the past decade related to this issue firmly establish that U.S. EPA has already thoroughly considered 

whether SSIs are subject to regulation as OSWIs under CAA 129, and has reasonably and appropriately 

determined that they are not. Nevertheless, in light of U.S. EPA’s reconsideration of this issue, NACWA 

provides the following additional comments in further support of U.S. EPA’s proper determination that SSIs 

are sufficiently regulated under other regulatory programs. 

 

10 Sierra Club v. Whitman et al., Case No. 1:01CV01578 (D.D.C.). 

11 Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Other Solid Waste Incineration 

Units: Proposed Rule, 69 Fed. Reg. 71472 (Dec. 9, 2004); Standards of Performance for New Stationary Sources and Emission 

Guidelines for Existing Sources: Other Solid Waste Incineration Units: Final Rule, 70 Fed. Reg. 74870 (Dec. 16, 2005). 

12 See Comments of EarthJustice, page 4 (Docket No. EPA-HA-OAR-2003-0156-0070) (Feb. 7, 2005). 

13 Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Other Solid Waste Incineration 

(OSWI) Units: Summary of Public Comments and Responses, pages 57-58 (Docket No. EPA-HQ-OAR-2003-0156-0104). 
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SPECIFIC COMMENTS 

 

1. U.S. EPA Properly Exercised its Discretion Under the CAA in Reasonably 

Determining that SSIs Should Not Be Included as a Category of OSWIs in the Final 

OSWI Rule. 

U.S. EPA was well within its discretion to exclude SSIs from the final OSWI rule. Congress expressly 

directed U.S. EPA to regulate certain categories of incineration enumerated in Sections 129(a)(1)(A)-(D) of the 

Act. The statute does not define the categories of “other” solid waste incineration units that must be regulated 

under CAA § 129(a)(1)(E). Therefore, inherent in U.S. EPA’s implementation of CAA § 129 is the discretion for 

the Agency to reasonably define what constitutes the statutorily undefined “other categories” of solid waste 

incineration units and then determine which of those categories warrant regulation under CAA § 129. 

This conclusion is firmly supported by the text of CAA § 129. Notably, while the statute provides firm 

timelines for the promulgation of standards and other requirements for specifically identified categories of 

solid waste incinerators (e.g., municipal waste incinerators, commercial and industrial waste incinerators, and 

hospital and medical waste incinerators), the CAA then only states that U.S. EPA must publish a schedule for the 

promulgation of standards for statutorily undefined “other categories of solid waste incineration units.” CAA 

§ 129(a)(1)(E). Thus, CAA § 129 plainly does not require U.S. EPA to promulgate OSWI standards for “every” or 

“all” possible categories of solid waste incineration units, without any consideration of the size of the 

incinerator or its impact on public health and the environment. 

An interpretation of CAA § 129 that would include all solid waste incineration units is not only 

inconsistent with the statutory language, but is also illogical because it would require U.S. EPA to expend a 

tremendous amount of federal Agency resources to develop MACT standards for every category of such units, 

regardless of the level of actual emissions from the units. Congress simply could not have required this result 

by merely directing U.S. EPA to publish a schedule for the promulgation of standards applicable to “other 

categories” of solid waste incineration units. 

Moreover, if Congress truly intended such far-reaching consequences, the legislature would have 

provided that directive to U.S. EPA within the text of CAA § 129(a)(1)(E). In other words, Congress would have 

instructed U.S. EPA to regulate “all” or “every” other category of solid waste incineration units. To the 

contrary, such an intent by Congress is noticeably absent in the text of CAA § 129 or its legislative history. As 

discussed below, the legislative history actually indicates that, in drafting CAA § 129, Congress was primarily 

concerned with regulating incinerators burning municipal waste. Congress did not direct U.S. EPA to regulate 

SSIs or any other specific type of incinerators under the OSWI category. 

For all of these reasons, Section 129 is clearly ambiguous with respect to the “other categories” of solid 

waste incineration units that must be regulated under CAA § 129(a)(1)(E). Congress’ instructions to the Agency 

to publish a schedule for the promulgation of standards for “other categories” of solid waste incineration units, 

therefore, inherently includes the authority for U.S. EPA to reasonably delineate which categories of 
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incinerators should be subject to regulation as OSWIs. U.S. EPA properly exercised that authority by collecting 

and analyzing information regarding potential OSWIs and ultimately concluding that SSIs should not be 

regulated as a category of OSWIs. As discussed below, this determination was a reasonable exercise of U.S. 

EPA’s discretion under the Act.

 

A. U.S. EPA’s Regulation of SSIs under CAA § 112 Prevents the Regulation 

of SSIs under CAA § 129. 

As an initial matter, U.S. EPA can not include SSIs among the categories of OSWIs to be regulated by 

the final OSWI rule because U.S. EPA has already determined that SSIs are more properly regulated under CAA 

§ 112. Section 129(h)(2) clearly states that: “no solid waste incineration units subject to performance standards 

under [Sections 129 and 111] shall be subject to standards under [Section 112(d)].” Thus, the language of 

Section 129(h) makes clear that U.S. EPA’s regulation of sources under CAA § 129 or CAA § 112 must be 

mutually exclusive. As U.S. EPA has rationally concluded, any unit that is subject to CAA § 112 standards can 

not be subject to CAA § 129. 

 SSIs are subject to regulation under CAA § 112, as U.S. EPA has already identified SSIs as an area source 

category under CAA § 112. After initially listing SSIs as a hazardous air pollutant (“HAP”) “source category” 

under CAA § 112, U.S. EPA subsequently determined that the SSI category did not have any sources with the 

potential to emit HAPs at a level approaching major source levels.14 In 2002, U.S. EPA then included SSIs as an 

additional area source category under CAA §§ 112(c)(3) and 112(k)(3)(B)(ii).15 Since area source categories are 

subject to the promulgation of emission standards under CAA § 112(d), SSIs may not also be subject to 

regulation under § 129.

 

 

B. Emissions from SSIs and POTWs are Already Stringently Regulated. 

U.S. EPA’s decision not to regulate SSIs as OSWIs under CAA § 129(a)(1)(E) is also reasonable and 

appropriate given that emissions from SSIs are already heavily regulated by other Congressionally-mandated, 

comprehensive regulations that are adequately protective of human health and the environment. Accordingly, 

no public health or environmental benefit will be realized from the expensive control measures that CAA § 129 

would impose if SSIs were erroneously included in the final OSWI rule. 

Since 1993, POTWs that practice incineration have been subject to a comprehensive, risk-based 

program for reducing the potential environmental risks of sewage sludge pursuant to Section 405 of the CWA 

 

14 See National Emission Standards for Hazardous Air Pollutants: Revisions of Source Category List under Section 112 of the Clean Air 

Act, 67 Fed. Reg. 6521 (Feb. 12, 2002). 

15 See National Emission Standards for Hazardous Air Pollutants: Revisions of Area Source Category List under Sections 112(c)(3) and 

112(k)(3)(B)(ii) of the Clean Air Act, 67 Fed. Reg. 43112 (June 26, 2002). 
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and the implementing regulations set forth in 40 CFR Part 503 (Standards for the Use or Disposal of Sewage 

Sludge). Section 405(d) of the CWA requires EPA to establish numeric limits and management practices that 

protect public health and the environment from the adverse effects of toxic pollutants in biosolids. Section 

405(e) of the CWA prohibits any person from disposing of biosolids from a POTW or other treatment works 

treating domestic sewage through any use or disposal practice for which regulations have been established 

pursuant to Section 405, except as in compliance with the Part 503 regulations. 

In the Part 503 regulations, U.S. EPA has identified the pollutants in biosolids that may adversely affect 

public health or the environment and has specified the management practices for the utilization and disposal 

of biosolids that are protective of public health and the environment. For disposal by incineration, the Part 503 

regulations require, among other requirements: 

(i) numerous management practices and general requirements; 

(ii) risk-based, site-specific limits for arsenic, cadmium, chromium, lead, and nickel 

content in the biosolids incinerated; 

(iii) compliance with National Standards for Hazardous Air Pollutants (NESHAPs) for 

mercury and beryllium (as discussed below); 

(iv) operational emission limits for total hydrocarbon (THC) or an alternative emission 

limit for carbon monoxide (CO); and 

(v) monitoring, recordkeeping and reporting requirements. 

See 40 CFR Part 503, Subpart E. 

Furthermore, in the course of developing the Part 503 regulations, U.S. EPA also proposed to establish 

requirements for dioxins (including specific congeners of dioxin, dibenzofuran, and coplanar PCBs).16 

However, after evaluating the emissions of dioxins from biosolids incineration, as well as surface disposal and 

land application, U.S. EPA decided such requirements were not warranted.17 This decision was based on the 

results of a comprehensive risk assessment that demonstrated that dioxin levels in biosolids and biosolids 

incinerator exhaust gases do not pose a significant risk to human health or the environment.18

As explained in detail in NACWA’s 1997 comments (pages 15-17), the numeric emission limits and 

management practices requirements established under the Part 503 regulations were derived from years of 

study and evaluation of the potential risks to human health and the environment which could be posed by the 

 

16 See Standards for the Use or Disposal of Sewage Sludge: Proposed Rule, 64 Fed. Reg. 72045 (Dec. 23, 1999). 

17 See Standards for the Use or Disposal of Sewage Sludge: Final Notice, 66 Fed. Reg. 66028 (Dec. 21, 2001). 

18 See id. 
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incineration of biosolids. The regulation of SSIs under this existing regime are risk-based standards which 

were developed to protect human health and the environment from any reasonably anticipated adverse effects 

from pollutants that may be present in biosolids. As a result, SSIs can clearly demonstrate that the emissions 

from their units are not adversely impacting human health and the environment by demonstrating compliance 

with the Part 503 requirements. Moreover, the statutory framework of this regime provides for ample means 

for U.S. EPA to identify and regulate additional concerns if supported by scientific evidence. For example, CWA 

Section 405 provides for a biennial review process that was specifically established for identifying and 

regulating any additional pollutants of concern. U.S. EPA has repeatedly emphasized its confidence that the 

Part 503 regulations are adequately protective of public health and the environment.19

Additionally, since 1975, U.S. EPA has imposed NESHAPs for mercury and beryllium emissions which 

apply to certain SSIs. See 40 CFR Part 61, Subpart E and C. The mercury NESHAP applies, in relevant part, to 

any source that incinerates wastewater treatment plant sludge and imposes emission limits for mercury, as well 

as imposes stack testing, sampling, and monitoring requirements. See 40 CFR Part 61, Subpart E. The 

beryllium NESHAP applies, in relevant part, to incinerators which process beryllium-containing waste and 

imposes emission limits for beryllium, as well as sampling requirements. See 40 CFR Part 61, Subpart C. These 

NESHAPs are expressly incorporated into the 40 CFR Part 503 requirements for POTWs. 

Since 1974, U.S. EPA has also imposed New Source Performance Standards (NSPS) for SSIs under CAA 

§ 111. See 40 CFR Part 60, Subpart O. These regulations apply to any incinerator constructed or modified after 

June 11, 1973 that 1) combusts wastes containing more than 10% sludge (dry basis) produced by municipal 

sewage treatment plants; or 2) charges more than 1,000 kg (2,205 lbs.) per day municipal sewage sludge (dry 

basis). See 40 CFR § 160.150. Under the existing NSPS for SSIs, regulated incinerators must comply with 

emission limits for particulate matter and opacity, as well as operational, monitoring, testing and reporting 

requirements. 

Thus, of the eleven pollutants identified in CAA § 129, many are already directly regulated under Parts 

503, 60, or 61, including total particulate matter, opacity, lead, cadmium, mercury, and CO (optional, as a 

surrogate for THC). See CAA § 129(a)(4). Additionally, U.S. EPA and NACWA have both also determined that 

SSIs are only very minor sources of several other of the CAA § 129 pollutants, including dioxins, sulfur dioxide, 

and hydrogen chloride. NACWA’s March 17, 1997 comment letter (pages 13-14) documents in detail many 

specific examples of existing SSI regulations, or information regarding emissions from SSIs, for each of the 

pollutants listed in Section 129. 

In addition to the federal requirements applicable to SSIs outlined above, public agencies operating 

SSIs are also required to obtain a Title V operating permit if they are “major sources” as defined by the CAA. 

Pursuant to 40 CFR Part 403, POTWs additionally implement, through local regulatory authority, pretreatment 

standards to prevent discharge of pollutants to the POTW that may pass through or interfere with treatment 

processes. Pretreatment is an effective way to reduce harmful constituents in the biosolids combusted by SSIs. 

 

19 See Letter from James A. Hanlon, Director of U.S. EPA Office of Wastewater Management, to Greg Kester, State of 

Wisconsin Department of Environmental Resources, dated September 20, 2004 (“EPA believes that 40 CFR Part [503] 

regulations are protective of public health and the environment and we continue to support biosolids management in full 

compliance with the Part 503 regulation.”) (attached hereto as Attachment C). 
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States also have authority to regulate and, in fact, do regulate air emissions from SSIs under their respective 

CAA State Implementation Plans. Together, these federal, state, and local regulations form an existing and 

effective regulatory scheme for regulating emissions from SSIs. Further regulation of SSIs under Section 129 is 

not appropriate or necessary for the protection of public health and the environment. 

 

C. Regulation of SSIs under CAA § 129 Would Result in Prohibitive Costs 

and Only Negligible Beneficial Impacts.

U.S. EPA’s decision not to include SSIs among the categories of OSWI covered by the final OSWI rule is 

also supported by an analysis of costs and benefits. The additional regulatory burdens imposed under CAA § 

129 would be substantial to SSI operators, while offering no discernable corresponding benefits. The added 

costs then imposed upon POTW ratepayers would be considerable, and could potentially lead to the 

elimination of incineration as a biosolids management option for many communities. 

Cost would invariably increase under CAA § 129 as SSI operators face competing MACT standards for 

pollutants that cannot be simultaneously achieved (e.g., NOx and CO). For further discussion see NACWA’s 

1997 comment letter (pages 17-19). 

An overwhelming cost or regulatory burden on SSIs would be inconsistent with U.S. EPA’s declarations 

that incineration is a safe and acceptable biosolids disposal method. It would also be contrary to the 

congressional intent expressed in Section 405 of the CWA, in which Congress mandates that U.S. EPA must 

provide for safe management practices for the use and disposal of biosolids, and not to dictate “preferred” 

practices and eliminate others. For example, Section 405(e) of the CWA states that “[t]he determination of the 

manner of disposal or use of sludge is a local determination,” as long as the practice is in accordance with U.S. 

EPA’s regulations. 

For all of these reasons, NACWA believes that U.S. EPA has properly interpreted CAA § 129, and 

reasonably exercised its discretion not to regulate SSIs as OSWIs pursuant to CAA § 129(a)(1)(E). 

 

2. U.S. EPA Properly Determined that SSIs are Not “Solid Waste Incineration Units” 

and, Therefore, Are Not Subject to Regulation Under CAA § 129.

Section 129 of the CAA requires U.S. EPA to develop and adopt new source performance standards and 

emissions guidelines for “solid waste incineration units.” Therefore, the potential scope of incineration units 

covered by Section 129 is expressly limited by the definition of “solid waste incineration units.” In CAA § 

129(g)(1), Congress expressly defined this term to mean: 

a distinct operating unit of any facility which combusts any solid waste material from any 

commercial or industrial establishments or the general public (including single and multiple 

residences, hotels, and motels). . . . 
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CAA § 129(g)(1). As fully explained below (as well as in NACWA’s March 17, 1997 comment letter), biosolids 

generated by POTWs is not a “solid waste,” nor is it “from commercial or industrial establishments or the 

general public.” Simply stated, incinerators which combust biosolids from POTWs are not “solid waste 

incineration units” and do not fall within the scope of U.S. EPA’s duty to regulate pursuant to Section 129. 

 

A. Sewage Sludge Is Not from Commercial or Industrial Establishments or 

the General Public. 

As U.S. EPA has previously determined, SSIs are not subject to regulation under CAA § 129 because the 

biosolids combusted by SSIs are generated at POTWs, rather than from “commercial or industrial 

establishments or the general public.” POTWs are not, contrary to the arguments advanced in petitioner’s 

request for reconsideration, properly characterized as “commercial or industrial establishments.” The fact that 

the sewered population served by a POTW is assessed a monetary rate for the collection and treatment services 

provided by the POTW does not transform it into a “commercial establishment” within the commonly 

understood meaning of that term, which must presumably be the meaning intended by Congress in CAA § 

129(g)(1). Moreover, the fact that Congress and NACWA refer to POTWs as “plants” or “facilities,” or that they 

refer to their works collectively as an “industry,” does not transform POTWs into “industrial establishments” 

within any reasonable interpretation of the term. 

Moreover, the careful phrasing employed by Congress in the definition of “solid waste incineration 

unit”—“solid waste material from commercial or industrial establishments or the general public (including single and 

multiple residences, hotels, and motels)”—unambiguously indicates that not every category of incineration units is 

subject to regulation under CAA § 129. Indeed, if Congress had intended that incinerator units that burn solid 

waste material from any source would be regulated by CAA § 129, it would have simply stated that intention. In 

other words, Congress would not have added this second phrase which limits the scope of Section 129 to the 

specific waste sources of “commercial or industrial establishments or the general public.” The inclusion of 

such language by Congress was purposeful; CAA § 129(g)(1) cannot be read in such a manner that would render 

this limiting language meaningless. 

Finally, while untreated domestic sewage may originate at “commercial or industrial establishments or 

the general public,” it is not a solid waste when it comes “from” these establishments. As discussed below, 

untreated domestic sewage is expressly excluded from the definition of “solid waste.” Thus, under CAA § 

129(g)(1), SSIs cannot be properly characterized as incinerating a solid waste coming from commercial or 

industrial establishments or the general public. Even if the CAA is deemed ambiguous on this point, Chevron 

U.S.A., Inc. v. Natural Resource Defense Council, Inc., 467 U.S. 837 (1984), directs that we defer to U.S. EPA’s 

reasonable interpretation of ambiguous statutory terms. Certainly, U.S. EPA’s reading of the CAA § 129 as 

excluding SSIs from Section 129 because the biosolids that they combust are generated at POTWs and do not 

“come from” commercial or industrial establishments or the general public is a reasonable exercise of Agency 

discretion. 

 
NACWA’s Comments on EPA Reconsideration of Sewage Sludge Incineration 

August 14, 2006 

Page 12 of 15 

B. Sewage Sludge Is Not a Solid Waste.

While NACWA acknowledges that U.S. EPA has previously stated that it believes otherwise, NACWA 

respectfully maintains that the biosolids generated by POTWs and combusted in SSIs is not a “solid waste” for 

purposes of the definition of “solid waste incineration unit” provided in CAA § 129(g)(1). “Solid waste” is 

defined in Section 129 of the CAA by reference to the definition of “solid waste” under the Solid Waste Disposal 

Act (which is generally referred to as the Resource Conservation and Recovery Act or “RCRA”).20 

RCRA defines “solid waste” as: 

any garbage, refuse, sludge from a waste treatment plant, water supply treatment plant, or air 

pollution control facility and other discarded material, including solid, liquid, semisolid, or 

contained gaseous material resulting from industrial, commercial, mining, and agricultural 

operations, and from community activities, but does not include solid or dissolved material in domestic 

sewage . . . 

RCRA § 1004(27) (emphasis added). Sewage sludge from POTWs is exempt from the definition of “solid waste” 

as “solid or dissolved material in domestic sewage.” This exception is commonly referred to as the “Domestic 

Sewage Exclusion” under RCRA. In fact, both Congress and U.S. EPA have expressly interpreted the definition 

of “waste” under RCRA to exclude POTW sewage sludge pursuant to the Domestic Sewage Exclusion. 

While the legislative history of Section 129 of the CAA is silent as to the definition of “solid waste” 

(other than, as discussed below, Congress was primarily concerned with municipal solid waste), the Domestic 

Sewage Exclusion had been written into RCRA for 25 years at the time Congress passed the 1990 CAA 

Amendment. Accordingly, in incorporating RCRA’s definition of “solid waste” in Section 129, Congress was 

well aware of the Domestic Sewage Exclusion encompassed in the definition of “solid waste.” 

Moreover, shortly after Congress passed the 1990 CAA, Congress amended RCRA to expand the scope 

of the Domestic Sewage Exclusion to cover Federally Owned Treatment Works. At the time of passage of this 

amendment (and after a year of debate and revision), Senator Chafee clearly confirmed Congress’ 

understanding that the Domestic Sewage Exclusion exempts POTW sludge from RCRA regulation: 

Sewage treatment plants operated by local governments - POTWs – have a special exemption 

called the domestic sewage exclusion under RCRA. If most of the waste received by a POTW is 

domestic sewage, their sludge and wastewater is exempt from hazardous industrial waste regulation even if 

they are also receiving hazardous industrial waste through sewer connections.

138 Cong. Rec. 514755, 514758 (September 23, 1992) (emphasis added). Accordingly, in using the limited 

definition of “solid waste” under RCRA for purposes of defining the scope of Section 129, Congress was aware 

that POTW sewage sludge would be excluded from the Section 129(g) definitions, which, in turn, would 

 

20 CAA § 129(g)(6) (“The term ‘solid waste’ shall have the meaning established by the Administrator pursuant to the Solid 

Waste Disposal Act.”) 
NACWA’s Comments on EPA Reconsideration of Sewage Sludge Incineration 

August 14, 2006 

Page 13 of 15 

exclude regulation of SSIs under Section 129. Express exemption of SSIs under the definition of “Solid Waste 

Incineration Units” under Section 129 would have been redundant. 

U.S. EPA has similarly interpreted the scope of the Domestic Sewage Exclusion to include sewage sludge 

generated by POTWs. The clearest example of this exclusion of POTW sewage sludge from the definition of 

“solid waste” under RCRA is found in U.S. EPA’s promulgation of a rule to identify and list hazardous wastes 

for petroleum refinery process wastewaters. In the Preamble to the Final Rule (November 2, 1990), U.S. EPA 

concluded that POTW sewage sludge falls within the Domestic Sewage Exclusion: 

These wastes [P038 and K048 wastes] are being added to the list of [hazardous] wastes . . . in 

order to regulate sludges generated at wastewater treatment facilities on site at petroleum 

refineries as well as sludges generated at off-site wastewater treatment facilities.14

. . . 

14 It should be noted that if wastewaters generated at petroleum refineries are 

discharged to a POTW and such wastewaters are mixed with domestic sewage 

from nonindustrial sources, the sludges generated in the POTW are covered under the 

domestic sewage exclusion and are not included in today’s listings. 

55 Fed. Reg. 46354, 46364 (November 2, 1990) (emphasis added). 

Accordingly both Congress and U.S. EPA interpret the definition of “solid waste” under RCRA to 

exclude POTW sewage sludge pursuant to the Domestic Sewage Exclusion. Therefore, POTW sewage sludge is 

not “solid waste” as defined by RCRA, and incinerators which combust POTW sewage sludge do not qualify as 

“solid waste incineration units” under Section 129.

 

C. The Legislative History of CAA § 129 Further Indicates that SSIs Were 

Not Intended To Be Regulated as “Solid Waste Incineration Units.” 

The legislative history of CAA § 129 is fully consistent with the conclusion that SSIs do not constitute 

solid waste incineration units. The provisions now codified in Section 129 of the CAA originated in a bill 

entitled “Municipal Waste Combustion Control Act of 1989,” introduced in Congress on January 25, 1989. The 

express purpose of the proposed legislation was to address the “garbage crisis” facing the nation in the late 

1980s – “the unseemly aspects of the growing garbage crisis - garbage washing upon ocean beaches, a garbage 

barge sailing the Caribbean for weeks in search of a disposal facility.”21

The bill further explained that Congress’ underlying objective was to “establish the needed regulatory 

program to make municipal waste incineration an environmentally sound part of our Nation’s waste 

 

21 135 Cong. Rec. S289-01 (Jan. 25, 1989). 
NACWA’s Comments on EPA Reconsideration of Sewage Sludge Incineration 

August 14, 2006 

Page 14 of 15 

management.”22 While subsequent legislative history reveals Congress’ concern with other specific, large 

incinerators other than municipal waste combustors (e.g., medical waste incinerators and industrial 

incinerators burning waste paper, wood, yard wastes, food wastes, batteries and plastics), Congress did not once 

mention POTW sewage sludge or SSIs, or even hint that its concerns over the incineration of municipal solid 

waste extended to the incineration of sewage sludge. 

 In sum, Congress did not intend SSIs to be subject to Section 129 regulation. While Congress provided 

U.S. EPA with authority to identify categories of OSWIs, it limited the scope of U.S. EPA’s authority in this 

regard to incinerators which combust “solid waste” as defined under RCRA and only solid waste “from 

commercial or industrial establishments or the general public.” SSIs do not fall within this definition, and 

therefore, cannot be regulated under Section 129 of the CAA. The plain language of Section 129, as further 

validated by the legislative history of CAA § 129, supports no other conclusion. 

CONCLUSION 

NACWA strongly believes that U.S. EPA has reasonably determined that SSIs are not subject to 

regulation under CAA § 129 and has, accordingly, properly excluded them from the scope of the final OSWI 

rule. NACWA urges U.S. EPA to maintain its current determination on this issue, and thanks U.S. EPA for the 

opportunity to submit comments in support of the Agency’s position. 

 

22 135 Cong. Rec. S556 (Jan. 3, 1989). 
NACWA’s Comments on EPA Reconsideration of Sewage Sludge Incineration 

August 14, 2006 

Page 15 of 15 

If you have any questions or require additional information concerning NACWA’s position on this 

issue, please do not hesitate to contact Robert P. Dominak, Co-Chair of NACWA Biosolids Management

Committee, at 216-881-6600, or Alexandra Dapolito Dunn, NACWA General Counsel, at 202-833-2672. 

 Sincerely,

 

 

Ken Kirk 

Executive Director 

Attachment A: NACWA’s March 17, 1997 comments to U.S. EPA. 

Attachment B: Letter from Benjamin H. Grumbles, Acting Assistant Administrator of U.S. EPA, to Scott 

Hassett, Secretary of Wisconsin Department of Natural Resources dated October 7, 2004. 

Attachment C: Letter from James A. Hanlon, Director of U.S. EPA Office of Wastewater Management, to 

Greg Kester, State of Wisconsin Department of Environmental Resources dated

September 20, 2004. 
ATTACHMENT A 



















ATTACHMENT B 


ATTACHMENT C