Strategies for Rural Development in Areas with Limited Public Infrastructure: Alternative Septic Systems

Water Supply Source Alternatives

Decentralized water supply systems can provide drinking water in growth areas that are not served by public waterlines.  System options include individual onsite wells, neighborhood shared wells, and large community wells. The number of connections and the design flow may trigger specific state rules dealing with increased setbacks and hydrological analysis, design criteria, construction details, and the ongoing operation, maintenance and monitoring of community water supply systems.

Maine’s Subsurface Wastewater Disposal Rules describe the required setbacks from drinking water supplies for first-time septic systems.   Minimum setbacks from onsite private potable drinking water supplies vary from 100 feet to 300 feet, depending on the design flows of both the septic system and the drinking water source.  Reduced setbacks are allowed for small wells that are drilled into bedrock, based on the depth of casing in the well.  For example,  the minimum setback can be reduced from the standard 100 feet to just 60 feet for a drilled well with more than 86 feet of casing.  Wells that tap sand and gravel aquifers are not permitted to take reductions from the standard 100 foot minimum setback, unless a Specialty Well application is submitted and approved.   Maine’s Well Drillers and Pump Installers Rules describe other criteria for siting and constructing new wells, including allowable construction materials, special requirements for installations in unconsolidated materials, disinfection, and design flow rates.

Types of Wells and Their Sources

Ninety percent of Maine’s rural residents tap into groundwater as their drinking water source. The most common types of water supply wells include bedrock, overburden, and dug or shallow wells.  Most drilled wells in Maine are bedrock wells, with steel casing drilled and grouted into the bedrock, tapping a groundwater aquifer in the rock fractures. These wells tend to be the most stable since they are protected from surface groundwater contamination, and there is little variation in the quantity and quality of water.  The only health issue associated with bedrock wells is the potential for dissolved mineral content in the groundwater, such as arsenic or radon.  (Other dissolved minerals, such as manganese and iron, may create unaesthetic color and odor problems but are not health hazards.)  If dissolved mineral content is an issue, numerous treatment systems are available to remove them.  

Drilled overburden wells are also relatively deep, but the aquifer flows within a layer of soil above the bedrock, usually in porous sands and gravels.  Overburden wells can tap into either a confined or an unconfined aquifer, and the quality and quantity of water are usually equivalent to those of a bedrock well.  The same health and aesthetic concerns due to dissolved mineral content may apply.  

Shallow wells, dug wells, and springs are also constructed in the soil overburden, but they usually draw groundwater from very shallow depths. These water supplies are the most susceptible to contamination from surface water and groundwater pollutants, failing septic systems, and animal pathogens (many of which can also affect human health).  Therefore they must be carefully located, constructed, maintained, and protected to ensure a safe long-term water supply. Many older shallow wells do not have these safeguards, so they may be more susceptible to water quantity and quality problems. 

Public health officials recommend that all Maine well users have their water tested at least once per year.  Numerous firms throughout Maine provide this service at a reasonable cost, and subsidized testing services are available for low-income households.  

Shared and Community Water Supplies

Wells serving more than one property may fall under one of several categories of shared wells and community water systems, each with specific state laws pertaining to siting, testing, design, construction, maintenance and monitoring.   Aquifer drawdown areas surrounding these wells are designated by the Maine Public Drinking Water Program as Source Water Protection Areas, and they require protective setbacks from septic systems that vary according to the design flows of both the well(s) and the septic system(s).   Source Water Protection Areas are intended to protect the groundwater within the drawdown zone from potential contamination.  Some aquifers (particularly the more sensitive overburden aquifers) may require very large protection areas to reduce the possibility of contamination.

The Maine Rural Water Association prepared a document for the Maine Drinking Water Program entitled “Best Management Practices for Groundwater Protection: A Guide for Local Officials and Public Water Suppliers.” This manual provides good technical information on how to minimize the potential for groundwater contamination, and offers best management practices (BMPs) that can be implemented on a local level to protect and preserve water sources. The manual asserts that good local planning is key to determining the best location and design of water supplies for new developments. The recommended BMPs include land use restrictions within different zones around a community well, and lot size recommendations to control development densities within these zones.

For more information on groundwater, water supply wells, and the planning process to site and protect water supply systems for new development, refer to the State Planning Office’s Technical Assistance Bulletin #1, Groundwater.

Related Work Plan Components

Workgroup Contacts

In Aroostook County: Jay Kamm, Ken Murchison, Joella Theriault

In Washington County: Judy East