Wastewater System Alternatives

Issues Addressed:
Housing Options Infrastructure Sustainable Housing

What is it?

Wastewater system alternatives are used to overcome limited wastewater discharge capacity, in order to build the appropriate housing types for a community. Dealing with wastewater is a major constraint on housing development in many communities. There are two conventional wastewater options for housing developments, and choosing one typically just comes down to location: (1) connect houses to (public) sewer systems, which usually treat and discharge wastewater into surface water; or (2) build an individual septic system for each home, which separates wastewater into liquids and solids, and discharges the liquids onto the land. 

Sewer-connected homes are realistically only built within or sometimes directly adjacent to existing sewer systems, since laying new sewer is very expensive. Therefore, most septic-connected homes are much more common in many suburban and rural communities. In the case of septic systems, the density of housing depends on how much land there is for each home to safely discharge wastewater. Factors such as the type of soil, number of bedrooms, proximity to wells and aquifers, etc. must be factored in to determine the minimum lot size for a home, based on its wastewater needs. 

Relatively dense housing that minimizes land costs per unit is often impossible to build with conventional septic systems. Therefore, some developers turn to alternative wastewater systems. Various technologies have been successfully employed to safely discharge effluent onto land, rather than into surface water, even for larger developments with multiple sources. There are three basic strategies new developments might employ:

  • Unconventional site planning and subdivision design
    Unconventional designs can allow individual septic discharge fields to fit into relatively small spaces, decreasing land costs of development. Unconventional designs may require zoning variances or waivers from subdivision regulations.
  • Community septic systems
    These systems collect wastewater from several households into one septic system. This decreases the amount of land needed overall and lowers construction and maintenance costs. Community septic systems vary in scale, but they are sometimes referred to as decentralized wastewater treatment systems.
  • “Innovative/Alternative” (I/A) septic technologies
    I/A septic systems rely on pretreatment of wastewater before it is discharged into soil. Typically this is through the addition of a denitrification system, though I/A technologies can treat other hazards as well. The state maintains a list of I/A technologies that are approved in New Hampshire.

These strategies can be used on their own or combined to produce more and better designed housing. Ultimately wastewater systems, their design, and available technologies are regulated by the New Hampshire Department of Environmental Services. In some cases, communities can require local approval of septic systems.

How can it help?

Wastewater system alternatives can…

  • Cut costs of land, development and maintenance, lowering housing costs overall.
  • Preserve open space that would otherwise be used for private leach fields.
  • Permit traditional patterns of small-lot development in villages without public sewer systems.
  • Enable mixed-use and multifamily development possible in areas without public sewer.
  • Increase the supply of affordable housing.
  • Provides design flexibility.
  • Fix failing wastewater systems.
  • Significantly improve water quality with better treatment.
  • Provide groundwater recharge.
  • Spur economic development in small rural communities.

Getting Started

  1. Make sure wastewater system alternatives are part of your community’s comprehensive plan. Recognize their impact on other planning goals, and include them as a recommendation if undertaking a plan.
  2. Audit your community’s zoning, site plan, and subdivision regulations. Identify any barriers to implementing these systems, such as explicit rules for conventional septic and dimensional regulations that do not accommodate such systems.
  3. If needed, amend zoning, site plan, subdivision, and/or other regulations to remove barriers to implementing these tools. This can be done by removing all barriers directly, or by using other land use regulatory tools (like cluster zoning) that will explicitly accommodate these systems.
  4. Work with property owners and developers to promote these tools. Incorporate discussions of potential alternative wastewater systems into early meetings with developers before development proposals are submitted.


  • Consultation with engineers will be required throughout pre-design and design processes due to the site-specificity and complexity of wastewater management. Engineers with less experience in wastewater system alternatives may need help looking at a specific site from all angles.
  • As with any septic system, big or small, regularly scheduled maintenance is critical, and a  mechanism to fund maintenance, repairs, and replacement reserves is essential.
  • Some local governments (such as Newbury, NH, see case study below) operate their own decentralized wastewater systems where they want to provide utilities but sewer is unavailable. These systems are typically larger than the community septic systems for particular developments. Setting up a public decentralized septic system is a large undertaking, but communities with significant resources could look into this option more.
  • Communities can require local approval of septic systems by the health officer of a town under RSA 147:1, prior to DES approval (RSA 485-A:32, I & II).
  • Building partnerships with local and regional river and lake associations, conservation organizations, and local conservation commissions can help assess and address concerns related to the impact of wastewater on water quality.