Tucked against the banks of the Charles River, 20 miles outside of Boston in Dedham, Massachusetts, Hebrew SeniorLife’s NewBridge on the Charles project will be a state-of-the-art, continuing-care retirement facility that represents the organization’s commitment to meeting the specific needs of seniors. Offering a continuum of independent-living residences and health-care services for active older adults, NewBridge on the Charles will also be a model for how sustainable design can be used to save increasingly scarce natural resources, lower operating costs, and attract the growing number of people who want to reflect their concerns for the environment in the way they live their daily lives.

The $485-million development, located on a scenic 162-acre campus, will open in the fall of 2009. It will incorporate building design elements and finishes that complement the surrounding natural beauty of the area. The development will feature 256 cottage homes, villas and apartments supported with senior services, 91 assisted-living units, 48 short-term recuperative beds, 220 long-term care beds, a community center and health care center. Further, the design calls for a K-8 school which will offer activities that will bring together community members of all ages.

The multigenerational opportunities offered on-campus will have benefits for both students and older residents. The elementary and junior-high school youth will gain a positive perspective on aging and share in the seniors’ life experiences and wisdom, while the seniors get an opportunity to participate in stimulating activities, conversation, and a chance simply to enjoy the enthusiasm of youth.

Just as the development will illustrate the positive experience that can come with a multi-generational environment, Hebrew SeniorLife’s commitment to ­responsible environmental stewardship will be evident throughout the community in ways large and small.

NewBridge planners incorporated sustainable principles in every possible aspect, highlighted by a $4 million investment in a system of geothermal wells that will provide heating and cooling for the 1-million-square-foot campus. The site design also includes a 170,000 gallon water harvesting system that will provide water for irrigation, drought-resistant landscaping, narrower roadways to limit the amount of impervious areas, and a calculated conservation effort that enabled facilities to be clustered on 62 acres of the site, leaving 100 acres in its natural state.

Geothermal system
The centerpiece of NewBridge on the Charles’ green developments is a 408-well geothermal heating and cooling system that, when completed, will be the largest of its kind in New England.

Generally, geothermal heat pumps use the earth as a heat source by using a circulating water loop that can utilize deep, vertical wells or shallow horizontal piping systems buried in trenches. Designers decided to implement a vertical system whose vertical holes require less land area and can be dug deep to maximize the heating and cooling load. The design features 408 such boreholes, each approximately 500 feet deep and providing approximately one kW of heating and cooling capacity for every 16 meters of depth.

During construction, individual boreholes are drilled and a pair of pipes joined with a U-shaped cross connector is placed inside. The pipes are filled with water and then sealed to re-circulate within the well. The borehole is then filled with a grout to provide a good thermal connection between the pipe and surrounding soil, and is sealed at the surface. This closed-loop system will prevent any direct interaction between the fluid and the earth, but will still allow heat to transfer across the pipe. At no time during or after the installation of the system will water be discharged to or withdrawn from the ground or the nearby Charles River. The only net discharge from the wells will be heat, which in this system will be run through a closed-loop cooling tower so the annual thermal discharge to the ground will remain zero.

One of the major challenges posed by the construction of the geothermal system was the timing of the well drilling around the excavation and foundation work on the buildings. Working closely with the project’s general contractor, Suffolk Construction, NewBridge designers developed a phased schedule that enabled the wells to be drilled without interfering with the foundation work.

The most critical component of the geothermal system is the heat pump itself, which is the unit that transfers heat from one reservoir to another. The heat pump will extract heat energy from the circulating water and make it available for heating or cooling purposes by increasing or decreasing the absolute temperature with respect to that of the energy source. As the temperature range of the water in the system remains constant throughout the year, the heat pump will concentrate the differential energy between the heat source and the pump and make it available for heating or cooling purposes. In the summer, the heat pump will extract heat from the conditioned space and send it down into the earth loop to warm the relatively cool ground. In the winter, this process is reversed, as the heat pump extracts heat from the relatively warm ground and pumps this heat into the conditioned space.

The overall efficiency of NewBridge’s system is derived from the pump’s ability to transfer heat rather than produce it. By extracting more than two thirds of its energy from the earth and moving it to the heat-pump unit, the geothermal heating and cooling system will generate approximately 1,600 tons of heating and cooling capacity and reduce the campus’ heating-related CO2 emissions by 34 percent – the equivalent of taking more than 1,700 cars off of Massachusetts roads annually.

Geothermal systems also create less demand for electricity during peak periods, which helps to defer the need to construct new electric generating facilities. For the NewBridge project, the geothermal heating and cooling system is expected to reduce electrical demand by approximately 20 percent. In addition to lowering the carbon footprint of the campus, the geothermal heating and cooling system will produce no on-site pollutants, improve indoor air quality, and have lower operating and maintenance costs, increased reliability, and a longer life cycle than other traditional heating and cooling systems.

Sound investment in the future
The decision to use geothermal heating and cooling came as a result of Hebrew SeniorLife’s mission to care for its natural surroundings and serve future generations with a more sustainable, efficient operation. Although it costs more to install a geothermal system than a standard heating and cooling system, the system will ultimately benefit the nonprofit’s ledger. The geothermal system is expected to save more than $325,000 in operating costs the first year. If fuel energy costs continue to rise, annual savings are expected to rise above $400,000 within five years.

Comprehensive efforts
Hebrew SeniorLife’s comprehensive green efforts at NewBridge on the Charles extend well beyond the geothermal heating and cooling system. Among the energy efficient and green features also incorporated into the design are: high performance windows, doors and insulation, energy efficient lighting and appliances, and countertops made from recycled materials. Also, the drought-resistant landscaping will feature native plant materials and grasses that are low-maintenance and do not require frequent watering. The developers are saving as much of the mature natural vegetation on the site as possible, and a manicured landscape will only be maintained in areas close to the buildings.

Project designers also took into consideration the campus’s proximity to the sensitive Charles River waterway by incorporating an extensive water management system in which rainwater is collected in a 170,000-gallon underground cistern. Fed by an intricate system of pipes, pumps, and porous pavement roadways, the cistern will supply all of NewBridge’s irrigation needs and use excess water to recharge the groundwater aquifer. This scheme will not only allow the development to boast a completely self-sufficient landscape in which no outside water sources are tapped, but will also prevent any runoff from reaching the Charles River.

The water management system is capable of providing more than 74,000 gallons per day for irrigation during peak periods, and is expected to provide almost 41,000 gallons daily throughout the remainder of the year. A back-up well will be available for use at times when the water in the cistern is inadequate. Also, a water filtration system in the cistern will remove particulates in the runoff from building roofs and paved areas.

In addition, this drought management system will assure the most efficient use of resources. At times when the Charles River is at low levels, the irrigation system will be set to use only 80 percent of the normal amount. In a drought situation, the system will use just 60 percent of the normal irrigation on portions of the site, and 80 percent in areas close to buildings that require the most water.

A comprehensive weather station and a system of soil moisture gauges will simultaneously monitor the weather, soil, and river levels to determine the appropriate timing and amount of irrigation. The data provided by the weather station will be incorporated into the curriculum of the K-8 school on-site and shared with schools throughout the town of Dedham.

Rezoning to preserve open space
Perhaps the most impressive conservation effort at NewBridge on the Charles is the preservation of more than 100 acres of undisturbed meadows, ponds, woods and wetland areas as permanent open space. These natural surroundings will form a buffer around the buildings and will be enhanced by more than 1.4 miles of walking trails and 1,800 trees that will be planted across the campus to replace those lost during the construction process. These green features will create a vibrant and fulfilling living experience for NewBridge residents and serve as a model for environmentally responsible developments along the Charles River.

Preserving this large expanse of open space required having the site rezoned so buildings could be clustered together. Also included in the rezoning was a stipulation that the roadways could be 24-feet wide as opposed to the 30-foot roadways required by existing zoning regulations. This change enabled NewBridge designers to reduce the amount of impervious paved areas. The town’s Conservation Committee and other town leaders supported this and other changes to the zoning requested as part of Hebrew SeniorLife’s effort to build a sustainable community. Dedham officials and residents are hopeful that the standards for sustainability set by Hebrew SeniorLife will encourage other developers who come to the area to follow suit.

It’s what people want
One of the most exciting aspects of Hebrew SeniorLife’s sustainable initiatives has been the interest and enthusiasm they have generated among potential residents of NewBridge on the Charles. While the organization’s emphasis on sustainability perfectly matches its mission, it is rewarding to see that the steps taken are strongly welcomed by the people who will live at NewBridge. On any given day, there will be as many as 2,000 residents, students, staff, and visitors at NewBridge on the Charles, making it a lively campus in the present but built with careful consideration for future generations. SLDT