A new restaurant/banquet facility under construction in Bedford, New Hampshire, will employ an extensive, sophisticated wastewater pretreatment system that, despite its complexity and size, will remain for the most part hidden from sight.

Under construction by NorthPoint CM of Hudson, New Hampshire, along Route 101, Murphy's Taproom, a 120-seat restaurant with a 240-seat banquet facility, will quietly process its wastewater on site in an advanced SeptiTech wastewater pretreatment system that is almost completely underground.

Jennings Excavation Inc. of Hollis, New Hampshire, is performing site work for NorthPoint including the excavation and installation of the SeptiTech system and three sizeable Enviro-Septic leach fields.

An Imposing Spread

The size of the pretreatment system is impressive, according to longtime construction veteran Ben Jager, Senior Estimator for Jennings Excavation.

"I've been in this business for 40 years and I've never seen such an extensive pretreatment/septic system - six very large precast concrete tanks in a row ranging from 8,000-gallon to 10,000-gallon capacity, plus a smaller tank for a pump chamber," Jager said.

Construction drawings show tanks to be 10 feet long by 17 feet wide, approximately 10 feet and 12 feet tall, respectively, with weights of 33 tons and 37 tons, respectively. Since the tanks are backfilled to have just 1.5 feet of cover, they are heavily reinforced and designed for H-20 loading, which is equivalent to the loads imparted by the wheels of an 18-wheel tractor trailer truck. Site work also consists of excavating and installing three large septic leach fields that are the final step of the pretreatment/septic system.

Scope and Equipment

In addition to excavating and installing the tanks and other units of the SeptiTech system, Jennings is responsible for all demolition and site preparation at the 10-acre site. This involves excavation and grading for the building foundation, 200-space parking lot, access roads, a concrete sidewalk and site lighting. The contractor also had to demolish existing bituminous parking lots, old septic fields, fences and remnants of the foundations of previous structures including a seafood restaurant.  

Jennings' work also extends off-site to Route 101, where the contractor is widening about 950 feet of turning lane for vehicles entering and exiting the restaurant lot.

The Hollis contractor has fielded nearly two dozen pieces of heavy equipment and trucks to perform site work for this complex project, with certified surveyors for TF Moran of Bedford, ensuring the cuts, fills and grading are done with extraordinary precision. In line with this, TF Moran is providing civil/site, structural and traffic engineering, permitting, land surveying and landscape architectural services for Murphy's Taproom.

While water has been no problem at the site, ledge is prevalent and in some places has been encountered at depths of only 5.5 feet, requiring the services of subcontractor Maine Drilling & Blasting. According to Mike Tagliareni, Jennings' Project Manager, the blasting company shattered about 4,700 cubic yards of rock, much of which was crushed on site to be reused for subgrade and base for roads and other structures, and landscape purposes.

Environment Friendly

Murphy's Taproom pretreatment/septic system is designed to process maximum flows of approximately 9,300 gallons per day and produce an effluent that has lower turbidity, or is clearer, has lower biochemical oxygen demand (BOD), lower Nitrates and less total suspended solids (TSS), than ordinary septic systems. These are all indicators of the amount of organic pollutants present in treated wastewater. The lower these figures, the better it is for the quality of groundwater and nearby surface waters.

According to SeptiTech, a Bio-Microbics Inc. subsidiary located in Lewiston, Maine, the pretreatment/septic system uses an aerobic, recirculating biological trickling filter process to remove a high percentage of BOD, TSS, and nitrogen from wastewater. The SeptiTech processor is added to a conventional system between the septic tank and leach field.

The system has two principal process loops - a treatment loop and a sludge return loop.

In the treatment loop, pumps circulate water through the media in the processor tanks and discharge pumps send treated wastewater to leach fields. In the sludge return loop, pumps periodically return solids produced by the treatment process back to the primary septic tank for settling. These solids are removed when the septic tank is pumped out during the regularly scheduled septic tank maintenance.

Meeting Tough Specs

Jennings' layout of the process tanks as well as the three septic leach fields is done with extreme precision to meet SeptiTech specifications. To do so, the contractor employed GPS technology provided by Eastpoint Laser LLC of Hooksett, New Hampshire. This included a Sokkia GPS system with data collector and Carlson software.  

The six principal tanks of the system, all manufactured by Phoenix Precast of Concord, New Hampshire, were stepped down at a 2 percent gradient. The layout can be likened to a flight of stairs, with each tank being a step and the flight as a whole sloping downward at 2 percent. The first tank in the lineup is an 8,000-gallon grease trap tank, followed in succession by a 10,000-gallon primary septic tank and four 8,000-gallon pretreatment process septic tanks set as two-side-by-side pairs. A Trapzilla high-capacity grease interceptor supplied by Thermaco Inc. of Asheboro, North Carolina, precedes the line of tanks, while a 3,500-gallon capacity pump chamber tank supplied by R.E. Prescott Co. Inc. of Exeter, New Hampshire. is installed at the end of the line. Each tank is set on a bed of crushed gravel, while the entire tank layout runs approximately 125 feet. A PVC force main conveys the finished treatment effluent to three septic leach fields.

Unique Leach Fields           

Septic fields contain a total of 5,400 linear feet of Enviro-Septic pipe in 100-foot lengths, laid level 1.5 feet apart on 6 inches of special septic sand. Unlike ordinary leach field piping, Enviro-Septic pipe actually further treats the effluent from the SeptiTech system due to a unique design consisting of ridged plastic pipe encased in green plastic fiber mat and non-woven black geotextile.

For the restaurant's 203-space parking lot, Litchfield Sand & Gravel and Brox Industries/Northeast Sand & Gravel provided the base materials. Continental Paving of Londonderry, New Hampshire, is responsible for installing 2,450 tons of asphalt pavement including about 2,000 linear feet of Cape Cod curbing.

A Mid-Summer's Finish

Jennings Excavation is expected to complete its work at Murphy's Taproom by mid-summer 2017, followed soon thereafter by the opening of the new restaurant.

The new Irish pub, which is actually a 22,265-square-foot "white tablecloth" restaurant, was designed by Warrenstreet Architects of Concord to resemble a farmhouse with an attached barn and two outdoor patios for seating an additional 120 patrons.