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

Case Study 3: Taking Advantage of A Public Water Supply

Summary

A small town with an established village center did not designate any growth areas in its comprehensive plan.  Instead, it designated areas suitable for denser residential growth, some of which are close enough to tie in to the existing public water supply. One of these areas contains a property with about 23 acres of buildable land. If this property were subdivided using the assumptions of minimum allowable lot sizes, a public water supply, and individual septic systems, about 35 lots could be created.  In areas where public water is not available, slightly larger lot sizes would be required because of the mandated separation between drinking water sources and onsite wastewater disposal systems. 

In this example, property owners would own and manage their individual onsite septic systems, so there would be no need to create a municipal or quasi-municipal management entity.   However, the town has an educational opportunity through its public water utility to send out reminders in the monthly water bills, to insure that each property owner keeps up with routine septic system maintenance. This will help to ensure that the onsite systems will continue to perform well over the long term.

Case Study 3: Details 

The Setting:  The community is a small, largely rural but suburbanizing town with an established village.  There are no explicitly designated growth areas in its comprehensive plan, in part because of interspersed soils and varied topography that would create difficult siting challenges for dense development using conventional onsite septic systems. Instead, the plan identified lands within the town that were “most suitable for residential growth” or “somewhat suitable for residential growth” – that is, relatively free of natural constraints, with soils that are more or less appropriate for subsurface wastewater disposal.  Some of these lands lie to the north of the village, close to a fire station and numerous other public and commercial services.  Most importantly for this case study, these lands have access to a public water supply.

The Conditions:  The public water lines primarily serve the village, but radiate out along several roadways to the north and west of the village.  The lines are owned and the water is delivered by an independent public utility district regulated by the Public Utilities Commission.

The vacant lands in the vicinity of the water supply service area encompass a wide variety of soil types, including well to poorly drained silt loams, fine sandy loam with shallow bedrock (10-20 inches), and a poorly drained, hydric silt loam (indicative of a wetland) in which subsurface wastewater disposal would not be allowed.  There are also some steep and unbuildable slopes along drainage ways. aerial photo

For this case study, an undeveloped tract was identified with access to the public water line, within walking distance of the existing village, and close to many public services, including fire protection.  According to the town’s comprehensive plan, the site is relatively free of natural constraints to development.

Estimated Building Potential:  This site contains a total of about 23 acres of buildable area (excluding flood plains, wetlands, steep slopes, etc.).  Its soils are almost entirely silt loams, moderately well to poorly drained, and all over five feet to bedrock.  This case study assumes that an onsite septic system will be installed on each lot.  Maine’s Subsurface Wastewater Disposal Rules call for Medium-Large and Extra Large system installations, based on the soil classifications (Lyman and Buxton, respectively) identified on the developable area of the site.  Based on a three-bedroom home design, this would require systems covering approximately 900 square feet for the Lyman soils, and 1,350 square feet for the Buxton soils. The use of proprietary septic system components (in lieu of  the traditional stone beds) could reduce the space needed for each onsite leach field by 25 to 50 percent. Additional area might be needed for fill extensions.  aerial photo with plan

Reserve space is not required in this particular town.  State regulators have opined that allocation of reserve space for residential onsite septic systems is not necessary, unless the developer proposes to use a conditionally-approved proprietary technology as a test case.   However, some local subdivision ordinances require reserve space as a risk minimization strategy, to ensure a timely replacement should the original onsite septic system fail.  If reserve sites were included in this case study, 1,800 – 2,700 square feet of each residential lot would need to be allocated to its subsurface wastewater disposal system. 

This is where the availability of a public water line comes into play.  Because these lots will not have to incorporate well setbacks, the state’s minimum standard of 20,000 square feet per lot can still safely accommodate a typical 3-bedroom home, garage, and sizable yard area, plus the entire subsurface wastewater disposal system (and, if required by local ordinance, additional reserve space for a replacement field).  After reducing the buildable area by the amounts specified in town ordinances for street construction, open space, and buffers along natural drainage channels that cross corners of the site, there is still ample space for 35 residential lots on the site.  This translates into about 2.1 units per net acre, and 1.4 units per gross acre.  Because it is hard for most of us to envision what “density” looks like, this composite image illustrates the percentage of the total site that would actually be occupied by 35 half-acre lots if they were all lined up next to each other, plus the portion of each lot that would be be occupied by the footprints of homes and septic systems.  The actual layout, of course, would involve streets, planned open space, preserved natural areas, attractive placement of lots and homes to avoid a “cookie cutter” ambiance, and other community amenities. In addition, the actual configuration of lots would probably include some that are larger than 20,000 square feet.

Managing the systems:  Each property owner will own and manage his or her individual septic system, so there is no need for an independent management entity in this hypothetical case study.  State regulators and soil scientists are confident that contemporary site evaluation, inspection, and installation practices will permit onsite septic systems to function effectively on 20,000 square foot lots without danger of malfunctioning or of contaminating groundwater.  However, because the water utility periodically sends informational material to the homes, there is an opportunity to implement a systematic education and reminder system that will help to ensure that the systems are in fact properly maintained by their owners, so they will perform well over the long term.

Implementing the systems: Under this approach, the town would enter into an agreement with the water utility.  Along with the utility’s required annual report to customers on the quality of the water supply, it would enclose an annual educational brochure about the maintenance of onsite septic systems, including a reminder about septic tank pumping and other scheduled routines.  The brochure could be prepared by town staff (e.g., the local plumbing inspector), the regional planning agency, or the Maine Division of Health Engineering for inclusion in the mailing.  The cost of this effort would be minimal, but it could be defrayed if necessary by requiring at the time of subdivision approval that the developer pay a fee to the town to prepare the piece, pay for any additional mailing costs to the water district, and create a modest escrow fund for future updates and mailings.

 

Related Work Plan Components

Workgroup Contacts

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

In Washington County: Judy East