SEPTIC OR CENTRAL SEWER IS THERE A BETTER WAY? Craig Goodwin NCS Wastewater Solutions Puyallup, Washington

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1 SEPTIC OR CENTRAL SEWER IS THERE A BETTER WAY? Craig Goodwin NCS Wastewater Solutions Puyallup, Washington Should central sewer be extended to a new subdivision or do we rely on septic systems for new development? This public policy choice, often made by default through lack of adequate resources and resistance to growth, has major implications for shaping the future character of our communities. The use of decentralized Small Community Sewer is an emerging trend designed to address the inherent limitations of both central sewer and septic systems. This trend also uniquely melds the interests of growth planners, the environmental community, homeowners, developers and builders. This paper will explore what comprises a Small Community Sewer and why it may make sense for your community land-use planning implications, benefits to the environment, sustainable management infrastructure and development economics. What Is A Small Community Sewer? Small Community Sewer (SCS) has the following design elements: 1. Clustered wastewater treatment and dispersal fields placed at one or more strategic locations in a development. Each cluster may support 20 residences or 500 residences. Clustering reduces collection costs and makes phased development more feasible and cost effective. 2. Use of low tech and easy to maintain treatment systems. Operators are not required to be on site every day. Weekly or even monthly inspection intervals are adequate. As a result, ongoing operating costs are affordable. 3. Use of drip or spray irrigation for land application of treated wastewater. This provides flexibility in locating dispersal fields and provides effective distribution of treated wastewater across larger areas. 4. Provides the ability to meet advanced nutrient reduction goals (e.g., nitrogen and phosphorus) through a cost effective combination of mechanical treatment and treatment in the soil. 5. Provides a management infrastructure by either a public or private utility. A utility structure best provides long-term sustainability. Land-Use Planning Benefits A 100-acre property filled with 50 to 75 large 1 or 2 acre lots is one definition of suburban sprawl. We call it septic sprawl. Yet that is the result we often see when our land use choices are limited by septic system design constraints. Community green space areas and playfields are economically limited by the large lot sizes. Development with a mix of ¼ acre, ½ acre, 1 and 2 acre lots is not feasible. Providing more affordable duplex

2 or multi-family housing in suburban areas can be out of the question. SCS can overcome these obstacles. Figure 1 illustrates a development based on septic. Figure 2 outlines this same development at equivalent density designed with SCS. Figure 1 igure 2 Figure 2 As Figure 2 illustrates, it is possible to maintain significant community green space, provide a variety of lot sizes and achieve target development densities all at the same time. Areas used for dispersal of treated wastewater can be used by the community for playfields, walking paths or just left in a natural state. Green space, rather than be a cost of development, actually becomes a major asset, providing homeowners with highly desired amenities at an affordable cost to the developer.

3 Development Economics Using SCS in non-sewered areas often permits development to the maximum density allowed by zoning regulations. Development on septic faces many more soils and site constraints. With SCS, we can locate the most suitable soils on a piece of property, treat to the level needed, even in environmentally sensitive areas, and utilize alternatives for dispersal that may not be practical for home septic systems. The site plan illustrated in Figure 3 shows a 68-acre parcel in an environmentally sensitive area. Very few lots are suitable for individual home onsite systems. However, by locating the best soils on the property and using drip irrigation technology to disperse treated effluent over a large area, this property will now support development of 29 total residences that match area zoning limits. Figure 3

4 Benefits To The Environment The primary domestic water supply in many communities is drawn from underlying aquifers. Water is pumped from wells, used for domestic and industrial purposes, collected, treated at a municipal treatment plant and finally discharged to area surface waters. This process actually removes water from local watersheds and can result in long-term deterioration of water supply sources. Land application of treated wastewater through drip or spray irrigation serves to recharge groundwater and preserves local watershed resources. Bays and lakes in many regions of the country carry high concentrations of nitrogen and phosphorus. Excessive nutrient loading contributes to excessive algae growth and low oxygen levels that render these environments uninhabitable for fish and other marine populations. Discharge of treated wastewater to these bodies of water can be a major source of nutrient overload. Over 30% of annual nutrient loading to Chesapeake Bay, for example, is estimated to be from municipal treatment plants. Flush fees now charged in the state of Maryland are specifically targeted to fund the high cost of investment in Advanced Nutrient Reduction (ANR) technology. SCS can often avoid the high cost of ANR technology through a combination of less intensive mechanical means and more natural processes in the soil. To illustrate, following is the nutrient balance for an SCS site in southern Maryland: Nutrient Concentrations (mg/l) Total Total Nitrogen Phosphorus Raw Sewage Municipal Treatment Plant Treatment Required Bay Discharge Limit (55) 5 (9) 1 SCS Land Application Treatment Required Soil Removal Groundwater Discharge Limit (30) (25) 5 0 (9) 1 With a discharge limit of 5 mg/l total nitrogen and 1 mg/l phosphorus, a municipal treatment plant must be capable of removing 92% of the nitrogen and 90% of phosphorus in the waste stream. The SCS treatment plant with drip dispersal must remove only 58% of nitrogen and no phosphorus to meet the same discharge limits, relying instead on the soil and plant root uptake for nutrient removal. The nitrogen balance and treatment plant limits will vary from site to site depending on soil characteristics, cover crop utilized and drip dispersal application rates.

5 SCS sites also do an efficient and reliable job of protecting groundwater resources from excessive nitrate contamination. While meeting < 10 mg/l drinking water standards for nitrates is readily achievable at SCS sites, conventional septic systems offer much more limited nitrate reduction capability. Management Infrastructure Lack of ongoing management is one of the greatest concerns of individual home septic systems. It is also one of the greatest benefits provided by a SCS. A long-term management infrastructure is established; ongoing permit and performance monitoring regimens are in place. Financing is fully funded by the development with no requirement that the broader community in any way be called upon to subsidize such new development. What remains after the development is an important long-term community asset. Conclusion Small Community Sewers offer an important alternative to individual home septic systems or central municipal sewer. Development with a Small Community Sewer also leaves many winners: Homeowner can expect quality sewer service. Underserved low income communities can now be served economically. The community is left with an established long-term management infrastructure. Land use planners will see less sprawl, a greater mix of development densities and greater opportunity for desirable green spaces and community amenities. Development can occur while protecting and enhancing the environment. Developers can achieve density goals at affordable economics, resulting in higher net profits. For more information regarding Small Community Sewers, contact NCS Wastewater Solutions at (800) or Craig Goodwin at: craig@nwcascade.com