Strategies for Rural Development in Areas with Limited Public Infrastructure: Alternative Septic Systems
The cost of septic system installation will depend upon the mobilization costs for construction equipment, system components, site conditions (whether a mound or subsurface system is constructed), and local availability of materials.
- A typical stone-bed conventional system in Maine usually costs in the range of $3000-$8000 for a 3-bedroom single-family home.
- Mound systems run higher, in the $8000-$15,000 range.
- For larger and more complex engineered systems, the costs can vary widely depending on the difficulties presented by the site and the nature of the wastewater stream, but in most cases the final cost will be upwards of $15,000.
- Pre-treatment systems may range in price from $5000-15,000 above the basic system costs, and most of the proprietary systems require contracts for continued technical assistance and remote monitoring. However, there may be offsetting savings in the construction of a smaller and simpler disposal field, as pre-treatment makes it easier to secure a variance from the prescribed design sizes in Maine’s wastewater rules . Obviously, if pre-treatment allows placement of a septic system on a lot that otherwise would have been undevelopable, the developer will happily pay these higher charges and recoup them through lot sales.
- Clustered systems include a collection system, in some cases a pre-treatment system, and common disposal fields that are often located at some distance from the properties they serve. Collection piping costs can vary depending on the length of piping and soil conditions (such as depth to bedrock), and long lengths of pipe with any associated pumping systems may add up to a significant percentage of the total construction costs. Disposal fields for systems with design flows of greater than 2,000 gallons per day will require a full-sized reserve area to be designated on the plans at the time of approval, and this reserve area cannot be developed with other land uses (although it can be applied to the developer’s total open space percentage for the subdivision).
Clustered system costs are unique to each site, and there is limited information available for cost comparisons. A large subdivision developer may have to work with a locally based engineer to determine the “magic number” where the economics favor building a clustered system versus traditional onsite systems, but it will probably be in the range of 10 to 25 lots depending on site conditions.
Two University of Rhode Island researchers published a cost comparison paper in 1998 entitled, “Shared Septic Systems: A shared sand filter and drain field was the least expensive solution for a difficult site.” In this paper, individual onsite systems requiring pre-treatment were estimated to cost approximately $100,000 to $120,000 for ten homes. For a clustered system using the same pre-treatment technology, the cost would have been $75,000 to $85,000 for the same ten homes. Operation and maintenance costs for the clustered system were estimated to be approximately $150-200 per year, comparable to onsite system estimates. Construction and mobilization costs are significantly higher now than they were in 1998, but it is reasonable to assume that the same relative cost savings for the clustered system would apply today.
Individual drilled wells in Maine generally cost in the range of $3000 to $7,000.
Related Work Plan Components
- Climate Change and Infrastructure Resilience
- Modernizing Communications/Electric Utility Infrastructure
In Washington County: Judy East