Mass drain fields aka community wastewater systems

A PRIMER: THE BENEFITS OF IMPLEMENTING A COMMUNITY ONSITE WASTEWATER SYSTEM

With a growing number of subdivision developments occurring in non-sewered rural or semi-rural areas — selecting the appropriate wastewater systems and structures to service those developments for maximum development value, long-term success, and environmental stewardship requires thought. The systems need to be cost-effective, efficient, and easy to maintain for optimal long-term use. One promising solution is the community onsite wastewater system (also known as community or mass drain fields, offsite systems, or decentralized systems).

WHAT IS A COMMUNITY ONSITE WASTEWATER SYSTEM?

In the past, it was common for each family residence to be equipped with a well and septic system for their own use. But with subdivisions in rural locations and some unique industry innovations, it’s possible to save time, money, and provide a significantly better experience for residents, developers, and the environment.

A community onsite wastewater system functions similarly to a residential septic system in some ways. Each residence has a septic tank to collect wastewater and separate the sludge (thicker solids) from the effluent. In a traditional system, the effluent leaves the tank and is dispersed through layers of soil through a drainfield before it re-enters the groundwater supply as clean water. In a community onsite wastewater system, the effluent is collected from multiple septic tanks and pumped to a singular, larger drainfield that all of the homes share. Increasingly, this wastewater passes through a treatment system prior to final dispersal.

BENEFITS OF A COMMUNITY ONSITE WASTEWATER SYSTEM

Historically, if a home or development was to be built in an area that was outside of the jurisdiction of a wastewater collection system, the only option was a traditional septic system with an individualized drainfield.  These on-lot septic systems can be very efficient and affordable; however, they severely restrict development opportunities in areas with poor soil or in areas where it would be preferable to have homes on smaller lots and clustered together with larger undisturbed tracts of natural area as a wildlife habitat. 

According to the U.S. Census Bureau (1999), 23 percent of the estimated 115 million occupied homes in the U.S. are served by community onsite wastewater systems with more than a third of homes in the southeastern United States depending on these systems (EPA). As technology and innovation improve, these systems are becoming the choice solution for public health departments and organizations.

Flexibility in Development & Building: Lot Size, Design, Mature Hardwoods, Green Space

Community onsite wastewater systems allow for more ease and flexibility in the way lots are developed, giving developers and residents alike more options. In traditional septic systems, each lot has to be able to accommodate a drainfield for each residence so there are significant restrictions on the size (and shape) of each lot. By creating a centralized drainfield in a community onsite wastewater system, developers can provide residents with more options in lot size. Some families may choose larger lots with more space at a higher price point, while some residents may prefer a smaller lot for easier up-keep or because it’s a more accessible price.

When individual drain fields aren’t a requirement for each lot, developers and builders have more options in terms of the design of the residence.  When drain fields will be on-lot, care has to be taken to keep drain fields functioning properly, driveways or car parks can’t be placed above them. The weight of vehicles and pressure can lead to soil compaction and clogging (or even worse, crushing the leach lines). But with a shared or mass drainfield, builders and residences have more choices about driveways, garage entrance and the orientation of the home on the lot.  Homeowners without a septic system on-lot have more usable lot space to accommodate pools, sheds, mother-in-law suites etc.

Using a community drainfield design, developers are also more able to accommodate variability in soil and conditions on individual lots. Lots with unacceptable percolation rates or shallow groundwater supply might not be good candidates for a traditional septic system, but would benefit from a shared community system. 

When a community onsite wastewater system is implemented, developers don’t have to excavate as much of a lot to accommodate a drainfield for each residence. Developers are able to preserve more usable lot area, mature growth and hardwoods on each lot as a result. This makes the properties more attractive to home buyers and to the neighborhood at large. With less deforestation, more of the natural ecosystem is also preserved.

When developers plan for the mass drainfield that the individual residences will tie into, it’s common for the area above ground to be designated green space. The larger, more open spaces provide accommodation for small parks, playgrounds, dog-walking trails and other recreational activities. These amenities add to the desirability of community living.

Cost-Effectiveness Through Shared Maintenance Costs

When an onsite wastewater system is used, residents typically share the cost of maintaining it through a monthly or annual fee (oftentimes as part of homeowners’ association dues). When these community systems incorporate treatment, it effectively guarantees that the community drain fields will not fail like untreated on-lot drain fields are expected to. Although some residents may prefer a traditional septic system because it eliminates monthly charges related to a shared system, there are still maintenance costs associated with on-lot systems including tank pump outs, and eventual drain field failure and replacement.

Typically, individual septic systems require maintenance of some sort every three years or so, with national pumping and cleaning costs averaging $383 (Home Advisor). Routine maintenance requirements are compounded by homeowners who flush personal products unknowingly, plant trees over a drainfield, or routinely park vehicles on the ground above a drainfield, causing soil compaction. Lack of education and understanding on the part of the homeowner can lead to a clogged drainfield or poorly performing septic system, speeding up the need for maintenance. If a system is ignored and performs poorly for long enough, serious repair may be required, sometimes costing several thousand dollars. The average lifespan of most septic systems is 15 to 25 years, with costs to replace or repair a failed system easily exceeding $10,000 when labor charges and landscaping are included.

Residents on a community wastewater treatment system can effectively use their home and yard in the same way any homeowner on city sewer would be able to without concern that they may cause thousands of dollars of damage to their property.

Safer for the Environment and Residents

Community onsite wastewater systems are the preferred treatment system for many public health departments and regulatory agencies overseeing area development.

These community systems help mitigate environmental concerns that increasingly drive more stringent septic system design and maintenance criteria in areas like the Chesapeake Bay in Virginia. Conventional septic systems are a potential source of pollution to area water bodies and wells which leads to more regulations requiring treatment systems to be incorporated in septic system design.

These treatment requirements increase the cost per lot for homes to be built when homes are served by on-lot septic systems.  Community systems help bring that cost per lot back down allowing for more affordable housing opportunities as well as a higher standard of wastewater treatment.

Properly trained and licensed wastewater treatment operations firms are able to manage these central treatment and dispersal systems.  Central treatment systems also allow for much more efficient regulatory oversight by state and local agencies. 

All in all, the result achieved from community treatment and dispersal systems is superior to on-lot systems in terms of better effluent quality, less environmental impact, and lower cost per lot. 

Reach out to us and ask about a few community wastewater collections and treatment systems we have worked on. We have sites in NC, VA, and SC that we’d be happy to tell you about! 252-243-7693, info@aqwa.net