A Small New Hampshire Waterfront Success Story Featuring a Stone and Pipe Leachfield and Wastewater Treatment System Comprising 75% Less Space than a Traditional Leachfield
When the Darby family of Hampstead, New Hampshire needed a new septic system for their small property on Sunset Lake, it was out of critical necessity. Their home at Edgewater Lane – part of a waterfront neighborhood that was formerly swampland before it was filled-in and subdivided in the 1920s – was still serviced by its original, outdated and now-failing cesspool.
When the Darbys’ one-story cottage-style home was built in 1927, the cesspool was located in the backyard. However, the previous owners had built a series of additions that resulted in positioning the cesspool below the cottage. Because the cesspool was constructed in the water table, it had technically been in a state of failure for years, unbeknownst to the Darbys. In the summer of 2013 they noticed strong odors coming from underneath the cottage. Further exploration revealed the cesspool’s condition and the need to remove it from service.
Small Waterfront Lots – A Common Challenge for NH Homeowners and Septic System Designers
Since water comprises nearly 5 percent of the 14-sq mile town of Hampstead – as well as 4.2% percent of the entire state of NH – waterfront property owners and prospective buyers commonly seek guidance from septic system designers experienced in the challenges of small-lot septic system design.
The Darby family sought the expertise of professional designers at NH-based Geometres Blue Hills, LLC –(603-749-4000) a full-service firm specializing in land surveys, land use consulting, septic system design, and environmental consulting – to assess their situation and specify a viable septic solution with visual appeal and long-term value for their small lakefront property.
The septic system designer, Mr. Ashley Rowe, recommended the Norweco Singulair wastewater treatment system for this project, having experienced its proven performance as a self-contained, value-engineered, alternative septic treatment solution for small properties situated near water.
The project’s approval and installation processes were filled with challenges, but through the diligent planning of Geometres Blue Hills, LLC, as well as the quality Norweco septic system manufactured and installed by A.J. Foss, Inc., and the meticulous excavation performed by G.E.Merrill and Son Excavating, this success story unfolds to include the major milestones detailed below.
Testing for Viability of Installation
To determine the viability of installing a new septic system, these factors were taken into account before a test pit was dug:
- The existing yard sits approximately 3.5-ft above the lake level, and is held back by a concrete retaining wall to the south.
- The entire neighborhood was once a swamp, filled nearly a century ago.
- A brook feeds the lake approximately 70-ft west of the property. The brook runs out of an area of poorly-drained soils approximately 200-ft north of the site.
- The lot was inspected for wetlands, and off-site options for leachfield placement were thoroughly explored.
The test pit was then dug with the lake at its full elevation, and percolation testing determined an acceptable flow for system installation.
Determining the Type of Septic System to Install
Many of the neighboring waterfront cottages were serviced by holding tanks – which were a better option for the Darbys than leaving the cesspool in service. However, when the Darbys considered the long-term financial implications such as the cost of constant tank-pumping, as well as the septic system’s impact to the property’s resale value, they decided that the ideal alternative was a stone and pipe leachfield with the Norweco Singulair septic system.
Consultations with the Town of Hampstead’s Code Enforcement Officer and officials from the New Hampshire Department of Environmental Services (DES) prompted the designer to seek several key waivers from the town and state, to enable installation of a conventional stone and pipe leachfield in the property’s small waterfront footprint.
Shoreland Water Quality Protection Act Compliance
To ensure compliance with the Shoreland Water Quality Protection Act (SWQPA), a proposed septic design plan must be approved by the New Hampshire DES before the design is completed. One example of the Act’s limitations involves the calculation of area that may be disturbed by heavy machinery. The Norweco Singulair system enabled this project to comply with the Shoreland Protection Act, since the Norweco system’s leachfield requires 75 percent less area than a conventional leachfield, making it ideally suited for small-lot waterfront properties.
Designing the Septic System
Designing the Norweco Singulair septic system with a stone and pipe leachfield involved these key steps:
Calculating the Leachfield Size
Because the Norweco Singulair system is granted a waiver by the DES that enables a 75% leachfield size-reduction, the septic system designer calculated the Darby project’s leachfield size as follows:
- The 2-bedroom cottage would typically require a 400 sq. ft leachfield
- The Norweco waiver reduced the leachfield size requirement by 75% , to 100 sq ft total
- A 7-ft wide by 15-ft long leachfield was designed, providing 105 sq ft of effluent disposal area (EDA)
Determining Hydraulic Mounding
Once the leachfield size was determined, the septic system designer calculated its vertical placement. Another advantage of the Norweco system is the waiver it earns in the form of a valuable soil credit, enabling placement of the leachfield only two feet from the water table, instead of the typical four-foot setback distance required by a traditional leachfield.
In order to take advantage of both waivers – reducing the leachfield size and its distance to the water table – the designer calculated how the discharge of liquid through the leachfield would affect the water table beneath it. This was because the discharge of a significant amount of liquid in a concentrated area would cause the water table to mound slightly below the area of discharge, and the hydraulic mounding had to be compensated for.
Siting the Norweco System for Installation
As it was sited in the Darby’s side yard, the entire Norweco Singulair tank was designed for installation within the water table. Anti-floatation weights and cables were specified, to eliminate the possibility of the tank rising out of its intended location.
Installing the Pump Chamber
The system’s 4-ft by 4-ft pump chamber was specified for installation between the Norweco tank and its leachfield, or effluent disposal area (EDA). The pump chamber, which was also designed completely in the water table, was custom-cast by the area’s licensed Norweco manufacturer and distributor, A.J. Foss, Inc. of Farmington NH, to include a 6-inch thick concrete ring protruding 16 inches around its base to prevent floatation.
Designing the Small Leachfield / Effluent Disposal Area (EDA)
Since traditional septic systems require a large leachfield that can span 20 x 20 feet or more, they are not feasible for small waterfront properties. The Norweco Singulair, however, required only a 7-ft by 15-ft stone and pipe leachfield, tucked into the corner of the lot and placed vertically 2.5’ above the seasonal high water table, leaving the finished grade above the leachfield an aesthetically-pleasing 3.2± feet above the original grade.
The septic system designer requested several waivers for siting the septic tank and stone and pipe leachfield/EDA in the property’s small waterfront footprint. Diligent coordination and open communication with town and state officials enabled the project to continue without interruption.
Key Requested Waivers included:
- EDA must be 75’ from an abutter’s well (Env-Wq 1008.04)
- EDA must be 75’ from onsite wells (Env-Wq 1008.04)
- Tank must be 75’ from an abutters well (Env-Wq 1008.04)
- Tank must be 75’ from surface water (Env-Wq 1008.04)
- Tank must be 75’ from on-site wells (Env-Wq 1008.04)
- Finished grade must extend 5’ horizontally beyond bed. (Requested 3.5’) (Env-Wq 1021.0)
- The sides of the EDA shall taper at a 3:1 slope. (Requested 1.5:1) (Env-Wq 1021.04)
- EDA must be 125’ from surface water due to soil conditions on site (RSA 483-B:9 V.(c)(2)(A)(i))
Submitting the Septic System Design for Approval
Within two days of submission, the design received local approval from the Town of Hampstead’s Code Enforcement Officer. He explained to the designer that he was satisfied with the plans, and agreed that the proposed system would be a valuable improvement to the property. Shortly thereafter, the NH DES granted their approval, and the designer began to elicit installation bids on behalf of the Darbys.
Due to the several key installation challenges cited below, several contractors passed on bidding this project because of uncertainty that they could install the septic system safely without undermining the existing cottage. In late December 2014, G.E. Merrill & Son Excavating, Inc. stepped up to the challenge.
Installation Challenges included:
- Tight quarters for excavation
- Very high water table and Live Gravel
- Proximity of excavation to the cottage
- Repeated snowfall
- Overhead power and utility lines
Tight Quarters for Excavation
The Darby’s small lakefront lot posed quite an excavation challenge, considering the various obstacles including the cottage, fencing, hedge rows, stone fireplace, and overhead utility lines that impacted the maneuverability of the moderate-sized excavator required for installing the Norweco Singulair tank.
High Water Table and Live Gravel
A high water table, in conjunction with the liveliness of the onsite gravel, made it extremely challenging to excavate such a large hole in such a small space. Stone has been added to the material at this point, in an effort to help stabilize it.
Proximity of Excavation to the Cottage
As pictured, excavation took place in very close proximity to the cottage. The edge of the hole was within two feet of the concrete blocks that support the cottage, as well as the opposing stone fireplace (just out of view). Of great concern was the potential undermining of the hole, due to gravel giving way under the weight of these structures – which proved to be a non-issue.
Installation was done during the winter to reduce the complication of the high water table, and to take advantage of peak drawdown of the lake. Had construction taken place in the spring, the lake would have been a full four feet higher, making the water table much more of a challenge. A further complication was the unprecedented, repeated snowfall that covered the entire site every two to three days that necessitated clearing before work could resume.
Overhead Power and Utility Lines
Utility lines that once ran to the cottage’s galvanized mast pictured in the photo were disconnected from the pole by their respective utility providers prior to construction. However, the lot was crisscrossed with several other lines (highlighted red in the photo), all without easement and many running directly over the cottage. Several attempts were made to have the utility providers re-route the lines so they didn’t run directly over the cottage, which resulted in moving all but the cable lines. However, all of the relocated lines were then positioned directly over the work area. After two months of phone calls to the utilities, with the winter window of opportunity closing, the excavator proceeded to work meticulously around the overhead lines, to safely install the septic system.
Thoughtful Design plus Norweco Quality Provide a Long-Term Septic Solution
Despite its many challenges, the project successfully passed inspection by the NH DEP. This success story illustrates how thoughtful, well-planned septic system design and installation, coupled with the system advantages and overall value of the Norweco Singulair, led to a long-term solution for the Darby family, and any future owners of the desirable lakefront property.