https://orcid.org/0000-0002-3950-0569
Figures
Citation: Allaire M, Nikkhou S, Lu P-J, Bakchan A (2026) The sewer divide: Challenges and new approaches for closing gaps in U.S. wastewater access. PLOS Water 5(3): e0000525. https://doi.org/10.1371/journal.pwat.0000525
Editor: Alison Parker, Cranfield University, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
Published: March 12, 2026
Copyright: © 2026 Allaire et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by awards from Columbia World Projects and the NSF NCAR Early Career Faculty Innovator Program to MA. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The Authors have declared no competing interests exist.
1. Wastewater Infrastructure Access in the U.S
Gaps in access to adequate wastewater infrastructure are prevalent in the U.S., yet rarely addressed beyond local levels. More than 24 million households, representing nearly 20% nationwide, are not served by a centralized sewer system (U.S. Census [1]). Instead, they rely on on-site wastewater treatment systems (OWTS), such as septic systems and cesspools. OWTS fail at alarming rates [2,3], due to unsuitable environmental conditions or inadequate maintenance [2,4,5]. OWTS provide only primary treatment, removing up to 40% of organic compounds [6]. Unlike sewage treatment plants, OWTS are not effective for removing nutrients and pathogens. This can lead to water source impairment. Greater densities of OWTS are associated with elevated risk of diarrheal disease [7].
Wastewater treatment gaps in the U.S. are overlooked, partly due to the assumption that OWTS are a rural infrastructure and their dispersed nature poses limited impairment concerns. In reality, over half of OWTS in the U.S. are in suburban locations [8]. This phenomenon is unique among higher-income countries. For example, only 13% of Canadian households use OWTS (Statistics Canada, 2010), mainly in rural areas, compared to 20% in the U.S., driven by suburban systems. Sprawling development beyond the reach of sewer systems continues in the U.S., as 18% of new, single-family homes rely on OWTS [9].
This essay focuses on distinctive governance features in the U.S. that have shaped uneven coverage. We argue that suburban OWTS results from the prevalence of unincorporated communities and highly localized planning, management, and financing. By examining these governance dynamics and contrasting them with international approaches, we identify potential pathways for expanding access to sufficient wastewater treatment through regional planning, professionalized management, and more coordinated state and federal support. Currently, most U.S. municipalities conduct wastewater planning in isolation, with limited coordination with neighboring jurisdictions or state government.
Across income levels, a substantial portion of U.S. households use OWTS (Fig 1). OWTS coverage only falls below 18% for households with the lowest income, who are more likely to reside in sewered urban areas. Thus, communities relying on septic range from affluent homeowner associations to low- and middle-income suburban fringe. Communities with notable wastewater challenges include those relying on straightpipes in the Southeast and Appalachia, cesspools in the Southwest, and a variety of substandard systems in colonias near the U.S.-Mexico border.
Note: Counts of households served by OWTS and centralized sewer in 2023. Data from (U.S. Census [1]).
2. Local Autonomy & Gaps in Formal Governance: Drivers of Uneven Services
Why does wastewater access in the U.S. dramatically differ from comparable high-income countries? We propose two related features of U.S. wastewater governance – (i) absence of a local government for many communities, and (ii) highly localized wastewater planning, management, and financing.
2.1. Communities without Local Government
A uniquely American phenomenon is the prevalence of population living outside municipal boundaries. Nearly 37% of the U.S. population resides in unincorporated areas [10,11]. Beyond the U.S., these communities are rare; and those that do exist tend to be remote and sparsely populated. Without a local municipal government, unincorporated areas are under county authority, which are less powerful [12] and have fewer revenue-generating options to support local infrastructure.
The origins of unincorporated communities are frontier-era settlement patterns, which are shared by the U.S., Australia, and Canada. Due to the impracticalities of establishing a formal local government for each cluster of farms or mining camps, this led to the creation of strong county, state, and provincial governments, respectively. Basic services could be provided, which partially filled the formal governance vacuum. However, while Australia and Canada established strong municipal oversight and closely managed suburban growth to be contiguous and sewered [13,14], the U.S. did not. More permissive U.S. policies allowed leapfrog, unsewered development in unincorporated areas. Federal policies explicitly supported suburban expansion, including mortgage financing and the Interstate Highway System [15].
The proliferation of unincorporated suburbs, reliant on OWTS, is driven by an emphasis on local autonomy, both for municipalities and communities beyond city boundaries. Annexation decisions in the U.S. are municipal-led. Selective expansion of boundaries can lead to affluent areas being absorbed by cities, while by bypassing lower-income areas or communities of color [16–22]. This practice of municipal underbounding can leave excluded areas with fewer options for accessing infrastructure services.
Local autonomy also extends to unincorporated communities. Incorporation is a choice. Residents can opt to remain unincorporated and avoid municipal taxes and regulations, if annexation is proposed. Wealthier neighborhoods may choose to self-fund services. In contrast, while Australia and Canada do consult residents, decision power over incorporation rests with state and provincial government. Legal and financial barriers to annexation and self-incorporation can trap communities in formal governance gaps. New incorporations located nearby an existing city are often subject to approval of the municipality [17,23].
A lack of local government can deprive such communities of adequate infrastructure access. County governments may overlook unincorporated areas or strategically withhold investments. Unincorporated residents face diluted voting power since all county residents vote for commissioners. Since unincorporated constituents are entirely dependent on county decisions, they can be underrepresented on issues that disproportionately affect them [24,25]. Through strategic disinvestment, county governments coordinating with adjacent municipalities can pave the way for redevelopment and displacement of existing residents, using powers of zoning, condemnation, and eminent domain (Such policies can be overt – the 1970s General Plan for Tulare County, CA described withholding public facilities, such as sewer, to displace unincorporated neighborhoods with “no authentic future” [26].).
2.2. Highly localized planning, management, & financing
Wastewater services are highly local, in contrast to other, regional utility services. Over 16,000 publicly-owned wastewater treatment works exist nationwide, compared to only 3,000 electricity providers [21]. This fragmented approach means that wastewater infrastructure is highly dependent on a community’s financial capacity and political will. Wealthier areas may actively avoid sewer in order to limit housing density (see Section 2.2.1). In less wealthy areas, the prevalence of suburban OWTS often reflects defaulting to short-term cost savings. In low-density areas, high per-connection costs hinder sewer development without higher-level government support. Yet, unincorporated communities face barriers in securing federal funding [27,28,29], as discussed further in Section 2.2.3. Counties responsible for serving them face noncontiguous service territories – remnants from selective annexation [30]. Ultimately, the decentralized planning and funding model produces uneven sewer coverage. Disparities differ across states due to U.S. federalism – states decide how much to intervene in local planning.
2.2.1. Planning.
Wastewater planning occurs at the most local levels in the U.S., with little coordination among neighboring municipalities or within a state. In contrast, Australia and Canada emphasize strong state-level planning. States can have greater capacity for comprehensive planning, compared to counties. Australian state water agencies take on the additional role of service provision in remote, unincorporated areas.
Local self-determination in the U.S. can be at odds with goals for uniform service delivery. Downstream communities often bear the environmental impacts of fragmented planning and management. Localized planning reflects the interests of one municipality and not possible benefits of sewer expansion to outside communities. Most U.S. municipalities plan sewer expansion in isolation through comprehensive growth plans. State governments have limited influence – fewer than one-quarter of states require plans to be consistent with neighboring municipalities [31,32] and only 16 states require sewer infrastructure to be included [32]. Developers can build unincorporated subdivisions without sewers, defaulting to OWTS as the lowest cost, short-term option. In Canada, provincial oversight keeps suburban growth largely within municipal boundaries, which limited unsewered, dense development.
Localized planning, by municipal and county governments, also enables exclusionary infrastructure avoidance, or ‘zoning by septic’. Affluent communities can resist sewer expansion to preserve large-lot zoning. Reliance on OWTS justifies minimum lot size requirements for the stated purpose of ensuring environmental quality [33], rather than avoiding multi-family housing. This practice exists in communities that are incorporated (e.g., costal New England) and not (e.g., Ramapo, NY). Aging OWTS can cause environmental harm, as seen in Old Lyme, CT, where a consent order required sewer installation to halt coastal pollution [34]. While state regulators can intervene after problems emerge, stronger regional planning could prevent them. Ultimately, barriers to state involvement in local wastewater decisions are political, not legal. Efforts to strengthen state-level control can be met with resistance, such as Maryland’s 2011 proposed OWTS limits [35] and a 2010 law in Florida for mandatory OWTS inspections. Currently, regionally-beneficial projects and policies can be hindered by local decisions.
2.2.2. Management.
Most OWTS in the U.S. are managed by individual homeowners [36], who often lack the knowledge, resources, and incentives for upkeep. Decentralized system performance is undermined by an absence of routine inspections and professional servicing [2]. Homeowner responsibility for operation and maintenance (O&M) is not the only arrangement possible. More centralized management models (Fig 2) include operating permits, maintenance contracts, and ownership by a responsible management entity (RME) [37]. An RME is a legally-established organization tasked with managing decentralized facilities in compliance with regulatory standards.
Homeowners can retain ownership while professionals handle upkeep through operating permits or maintenance contracts. These arrangements exist in some environmentally-sensitive locations or for advanced systems, such as aerobic treatment units. Under the operating permit model, system renewal depends on a satisfactory inspection, providing accountability and incentives for compliance, as seen in Sea Ranch, California, and Ireland’s National Inspection Plan [38]. Two features of the Ireland program defray costs to homeowners. First, rather than homeowners covering full costs of inspection when it occurs, they pay a one-time OWTS registration fee and the national government funds the remainder (Ireland Water Services Act 2012, s. 70B). Second, grants can cover up to 85% of repair costs for systems that fail inspection. In Florida, not addressing such concerns led to the repeal of a mandatory, statewide inspection program before it began in 2012 [39]; homeowners would have borne full costs of inspection and repairs.
The maintenance contract model requires homeowners to hold service contracts with certified providers. Tracking and enforcing lapsed contracts is a regulatory challenge. Enforcement can be strengthened by combining the maintenance contracts and operating permit models, which is done in Monroe County, Florida [38]. Another solution is to require an RME to provide maintenance on a regional basis. Taiwan uses this RME maintenance approach – OWTS owners pay a fee on their water bill that funds regular inspection and desludging (Waste Disposal [40]. Several South and Southeast Asian countries have adopted RME-led maintenance, such as India, Indonesia Philippines, Malaysia, Vietnam [41–44]. Academic circles in the U.S. advocate for expanding RME management to OWTS [45].
The most centralized model is where an RME owns and operates the infrastructure, similar to a public utility [37]. RMEs often own centralized sewer systems or decentralized systems serving multiple households, such as clustered systems (discussed in Section 3.1). Few examples of RME-owned OWTS exist. One case that comes close is the Otter Tail Water Management District in Minnesota. This special district mandates that it maintains septic systems for residents [38]; fees are paid via property taxes [46].
2.2.3. Funding.
Wastewater funding in the U.S. is overwhelmingly local. Federal sources cover only 4% of annual water and wastewater infrastructure spending [47]. Communities most in need face substantial barriers to Federal programs. Unincorporated communities face an additional hurdle of establishing a responsible management entity to operate the system and pay upfront installation costs [28].
The main Federal program to support wastewater, the EPA Clean Water State Revolving Fund, has historically supported centralized systems. Onsite systems became eligible only in 2014 (WRRDA; P.L. 113–121), not all states fund such projects [48]. Most states do not report decentralized wastewater needs – many lack data on number of needed decentralized systems and construction costs [48]. Eligible projects must advance compliance with the Clean Water Act; broader objectives of expanding infrastructure access are out of scope. While expanded access can be supported through the USDA’s Rural Development program, only rural communities qualify. This excludes underserved suburbs, including some colonias, which are low-income settlements within 150 miles of the U.S.-Mexico border and lack adequate water and sewage systems (Pub. L. No. 101–625, 1990). Growing suburbanization means that 60% of colonias will not qualify as rural for HUD block grants [49].
By contrast, countries like the U.K. and Canada have national infrastructure banks that offer long-term financing for debt that can require two or three decades to pay back. The closest U.S. equivalent, state revolving funds, focus narrowly on regulatory compliance and operate independently within each state. In Canada, funding can support system expansion and improved reliability of existing systems. Fewer barriers exist for unincorporated communities, since Canadian non-profits are eligible to receive funds on their behalf. In the U.S., non-profits rarely receive Clean Water State Revolving Fund financing [50].
3. Solutions: Expanding Coverage in the U.S
Filling the governance void for U.S. wastewater infrastructure requires shifting to professional management and coordinated planning. Municipal incorporation is a choice in the U.S.; strong local autonomy comes at the expense of uniform service delivery. How can access to reliable wastewater treatment be expanded to communities that lack local government?
A lack of political will is one of the largest obstacles to closing sanitation gaps. Those currently connected to centralized sewer or on OWTS by choice might see little benefit in extending services, given substantial upfront costs. Underserved, unincorporated communities have little recourse due to an absence of local government; there can also be the perception that they knowingly chose to reside in a location with fewer services and taxes. Building support could hinge on highlighting the tangible benefits, such as improved water quality for recreation and drinking sources. Such benefits accrue to existing and newly connected households. Yet, limited research on the environmental impact of OWTS at regional scales makes it difficult to communicate the consequences of inaction.
3.1. Extending sewer lines and clustered systems
Access to wastewater treatment could be expanded through extending sewer networks and adopting modular, neighborhood-scale systems. The suitability of these systems will depend on settlement patterns, topography, and proximity to existing networks [51]. Septic-to-sewer conversions are feasible with adequate housing density and location near existing collection networks. State and federal policy could address barriers faced by unincorporated suburban areas, in cases where existing sewers are within municipal boundaries. Federal funding for municipal wastewater infrastructure could be conditional on providing extraterritorial service to unincorporated residents. States could also require service connections to lower-income unincorporated areas as a condition for annexation or service extensions to affluent areas, similar to inclusionary zoning for affordable housing.
Sewer extensions are not the only technology option. Decentralized, clustered systems connect multiple homes to a shared treatment unit [28]. Unlike conventional sewer, these feature a liquids-only collection network, with each household retaining an underground tank for solids. Liquids-only systems use less expensive, smaller-diameter pipes compared to conventional sewer [52]. These systems offer a flexible middle ground between costly centralized sewers and individual OWTS. Clustered systems at the neighborhood scale provide an entry point for professionalize management [53] and could ultimately shift the physical scale and layout of U.S. wastewater infrastructure. Noncontiguous service areas left behind by underbounding are inefficient and costly to serve with conventional sewer [30]; yet clustered systems offer a viable alternative. These systems could also appeal to wealthier, unsewered communities seeking to maintain low density and large lots. Secondary treatment is possible without the excess capacity to support new housing development. Federal and state financing for installation costs could incentivize adoption.
State environmental regulators have tools to compel sewer extensions or new systems. Some states can mandate sewer connections in cases where public health concerns arise. In all states, consent decrees can mandate infrastructure for municipalities or counties releasing effluent that impairs surface waters. Other states go further and demonstrate what is possible, particularly for extending service to unincorporated communities. In Ohio, the state regulator can order counties to address sanitary concerns in unincorporated areas by creating county sewer districts and providing funds for construction and O&M (Ohio Rev. Code § 6117.34). In Rhode Island, OWTS owners can connect to nearby sewer lines outside their jurisdiction if that connection is closer and less costly to the homeowner (RI Gen L §45-24.5-6). Such a policy for unincorporated areas could address jurisdictional barriers for septic-to-sewer conversions.
3.2. Planning at Local and Regional Levels
Unincorporated communities could be integrated into existing planning processes and new, regional approaches. State mandates could compel nearby municipalities to consider unincorporated residents’ needs. For example, city master plans in California must assess infrastructure needs of adjacent low-income unincorporated areas. Counties in California offer advisory councils for unincorporated residents to provide input on county planning decisions. These mechanisms leave all decision power with local governments. Stronger reform would shift wastewater planning to regional levels. Regionalization could overcome local veto power of defensive, anti-growth factions and extend services to those not represented by a local government. In some metropolitan areas, regional planning is already conducted by special districts. Yet, many places lack cross-jurisdictional entities. Existing regional councils – some 500 that include over 35,000 local governments – could facilitate wastewater planning across jurisdictions, similar to metropolitan transportation planning.
State-level planning policy could also enable this shift. Comprehensive growth plans at the state level could designate areas for wastewater infrastructure expansion. States could also require local comprehensive plans to align with statewide goals and the plans of neighboring jurisdictions. Currently, vertical and horizontal consistency is required by less than a third and a quarter of states, respectively [31]. Regional councils could ensure that local wastewater plans are consistent with regionwide goals before projects are approved. A successful example is the Metropolitan Council in Minnesota, which reviews local comprehensive plans to ensure that align with regional aims for water and wastewater in the Twin Cities area.
3.3. Financial capacity & affordability
Expanded access to finance for wastewater infrastructure is essential for moving beyond localized planning. Existing federal programs could better support new wastewater systems in unincorporated areas. Grants and low-interest loans through EPA and USDA programs remain key financing mechanisms, yet unincorporated communities often struggle to qualify and navigate the application process [3]. Expanded technical assistance and planning grants are a step in the right direction. Unincorporated communities could be better served by technical assistance networks, such as the Rural Community Assistance Partnership (Federally-funded) and the Water Finance Exchange (philanthropically-supported), which aid in project planning and federal applications. Federal commissions, such as the Appalachian Regional Commission, can bundle projects regionally and vertically, thus combining multiple funding sources or grouping small projects into a single application. This aids communities in more efficiently accessing federal funds.
State or national infrastructure banks could offer further support. Currently, federal wastewater funding in the U.S. focuses on regulatory compliance for existing systems. A state or national bank could prioritize expanding wastewater access for underserved locations, similar to the Canada Infrastructure Bank. Such an institution could provide low-cost, long-term financing for major projects, making centralized sewer or modular decentralized systems financially viable, particularly for unincorporated areas lacking taxing power or for local governments extending services outside their service territory. To finance systems in unincorporated communities, loans could be either be made to the RME or government entities (e.g., county, special district). Repayment could be secured through user fees and/or special assessments.
Along with finance, states could address affordability of sewer extensions. Extensions are especially costly for unincorporated residents, who tend to face higher connection fees and out-of-city service charges [54]. Extraterritorial surcharges are justified based on tax equity (unincorporated residents do not pay municipal tax) and cost recovery of extending services to areas with higher per connection costs. Extensions are more appealing if capital costs are defrayed by external sources. Some states, such as North Carolina have prohibited connection fees for newly annexed communities; instead, expansion costs are spread across a service area. To address extraterritorial rates, some states require differential rates for out-of-city customers to reflect actual costs, preventing excessive markups.
3.4. Management: Local and regional levels
Professional management, at local or regional scales, shifts responsibility from homeowners to institutions. This introduces accountability and technical capacity historically lacking for decentralized systems. At the local level, clustered systems or individual OWTS can be managed by an RME serving a single community; this ensures consistent O&M while preserving local responsiveness. Some communities prefer a local approach and resist more centralized models [45]. Yet, smaller communities often lack technical, managerial, and financial capacity. County or state technical assistance and shared-service agreements could enable local autonomy while ensuring reliance performance.
Regional RMEs benefit from economies of scale and pooling technical expertise and financing. By overseeing multiple service areas, more uniform service standards can be delivered. Loudoun Water in Virginia exemplifies this model – a countywide special district managing clustered systems in unincorporated areas. Developers construct these systems that are either transferred to utility ownership or maintained under long-term contracts [55]. County planning and zoning ordinances that promoted managed cluster systems in exurban areas.
While new, clustered developments provide an entry point for professional management, existing OWTS remain a challenge. Policies at county or state levels could enable this transition by requiring management contracts or operating permits and/or an RME. State-level policies provide political cover for local officials to enact sweeping changes as well the potential to defray homeowner costs. Mandating maintenance will not guarantee entities will serve all communities in need. Private providers could be subsidized for servicing low-density or low-resourced locations. Public entities could be required to inspect and/or arrange routine pumping of OWTS in their jurisdiction.
Limited research exists on what management arrangements are effective. Questions remain regarding scale and institutional type. RMEs may take public or private forms. County governments and special districts are public entities that can ley fees, including through taxes. Private entities range from small mutual water companies to large, investor-owned utilities. Either public or private mechanisms could expand management capacity in unincorporated areas.
Regional-scale RMEs often maintain a professional workforce and establish standardized procedures for monitoring, maintenance, and billing [56]. For example, Australia serves remote, unincorporated areas with state-scale water agencies. Yet, such institutional stability can limit flexibility, as bureaucratic procedures constrain responsiveness to unique community needs. Ultimately, by professionalizing O&M and linking system operation to regional planning, RMEs could balance local autonomy of unincorporated areas and expanded wastewater service coverage.
4. Conclusion
The gap in U.S. wastewater access is fundamentally a governance failure, rooted in a fragmented and highly localized system unlike that of peer nations. Unincorporated communities, often left behind as islands or fringes in a metropolitan area, are governed by less-resourced county governments, which are ill-equipped to manage the capital-intensive nature of wastewater infrastructure. This problem is compounded by the U.S. tradition of voluntary incorporation and permissive planning rules that normalized septic reliance, leading to widespread municipal underbounding. Solutions for closing the wastewater gap are primarily political, not technological. Regional wastewater planning can overcome local vetoes and expand services by shifting away from a hyper-local focus. States can step up with greater oversight and resources, such as technical assistance or infrastructure banks to fund upfront connection costs and perhaps defray O&M. By combining professional management, regional planning, and targeted state and federal financial support, the governance void for infrastructure can be filled and reliable wastewater services can reach all communities.
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