Achieving Net Zero Energy on Cape Cod
At the Massachusetts Military Reservation, the energy demands of an extensive groundwater cleanup program have been offset by construction of three wind turbines.
By Rose Forbes, P.E., M.SAME, Brad Johnson, P.E., and John T. A. Miller, P.E., M.SAME
The total output of the three wind turbines in operation at the Massachusetts Military Reservation have offset the energy demands of the groundwater cleanup program. IMAGE COURTESY AFCEC
Through comprehensive remedial process optimization and the construction of three utility-scale wind turbines, the Massachusetts Military Reservation (MMR) groundwater cleanup program, a joint-funded U.S. Army and U.S. Air Force project, is the first large-scale Department of Defense (DOD) cleanup effort to achieve Net Zero Energy.
Situated over 22,000-acres on Cape Cod, MMR was first established for military use in 1911. Today, the installation is home to five diverse military commands: the Massachusetts Army National Guard at Camp Edwards; the Massachusetts Air National Guard and U.S. Air Force 253rd Combat Communications Group at Otis ANG Base; the 6th Space Warning Squadron (6 SWS) PAVE PAWS radar site at Cape Cod AFS; and the U.S. Coast Guard at Air Station Cape Cod.
MITIGATING ADVERSE IMPACTS
The long history of military use at MMR had led to contamination of the Sagamore Lens, which is the sole-source drinking water aquifer for the residents of Upper Cape Cod. The Air Force Civil Engineer Center (AFCEC) manages the Installation Restoration Program to investigate and clean up the contamination. The program has managed 80 source areas and 14 groundwater plumes. AFCEC constructed nine treatment plants, more than 100 extraction and reinjection wells, and 27-mi of pipeline that, at their peak in 2007, pumped, transported and treated approximately 18-million-gal per day of contaminated groundwater. Through remedial process optimization, this treatment rate had been reduced to approximately 12-million-gal per day in 2012.
The treatment systems, however, are energy intensive and, as such, had a corresponding environmental impact. The fossil fuel-derived electricity produced thousands of tons of air pollution annually. AFCEC calculated that, before optimization, the electricity used to run the systems actually was adding more volatile organic compounds to the air than were being extracted from the groundwater.
The highest operating costs with pumpand- treat groundwater remediation systems are associated with the pumping of groundwater and the reactivation of granular activated carbon (GAC) used to remove contaminants. Each of these processes requires large amounts of electricity and natural gas. Remedial process optimization (which is essentially a systematic review of all processes involved in the performance of a remedial action to reduce costs and environmental impacts while not negatively affecting remedial action goals, such as cleanup timeframe and protection of human health and the environment) can substantially reduce the consumption of energy associated with these actions. And in fact, while annual consumption of electricity by the MMR groundwater treatment program peaked in 2007 at approximately 13,900-MWh, by 2012, electricity consumption had been reduced by 35 percent to 9,100-MWh.
An optimization effort at the Chemical Spill-21 remedial system alone reduced the total flow rate by 0.5-million-gal per day. This resulted in annual savings of $48,000 in electricity costs and a reduction of 225-T of greenhouse gases. The lower flow rate allowed for a reconfiguration of the GAC system. This significantly improved numerous efficiencies while also saving on operational and fuel costs. For instance, because the reconfiguration eliminated the need for 24 annual monitoring water samples, that, in turn, reduced the amount of automotive fuel required for collection and transport.
The Hunter Avenue Treatment Facility at MMR currently treats 4.2-million-gal per day of contaminated groundwater, but requires 1,900-MWh per year of electricity.
There were additional optimizations as well. Well pumps were resized after reductions in design flow rates to better improve efficiency rather than simply throttling the existing pump to achieve the lower flow rate. Sodium vapor lights at treatment plants were replaced with high-efficiency fluorescent fixtures. This reduced the total power consumed by lighting by 50 percent—an annual savings of approximately $55,000. Additionally, variable frequency drives were installed to improve the efficiency of centrifugal pump systems after reductions in flow rates. Obsolete lighting systems at the Operations and Maintenance building were replaced with high-efficiency lightemitting diode and fluorescent fixtures. The use of gas-fired heating systems was discontinued due to the geothermal effect gained by pumping 55°F groundwater through the systems. And GAC vessels were painted white to enhance ambient lighting.
RENEWABLE ENERGY OPPORTUNITY
To complete the path to Net Zero Energy, AFCEC performed a wind turbine constructability assessment and a wind resource assessment to evaluate the potential energy output, economic feasibility and the environmental impact of potential generation of electricity onsite.
Results indicated that, due to net metering under the Massachusetts Green Communities Act, wind-generated electricity provided an economic advantage over purchasing grid electricity. Sufficient open land, higher elevation, proximity to an existing power distribution line and adequate distance from residential housing all were seen as preferential siting factors. A previously disturbed tract of land adjacent to the Landfill-1 (LF-1) treatment plant was identified for use.
The team then completed an environmental assessment under National Environmental Policy Act requirements and found that the proposed project posed no significant impact to wildlife or other natural resources. Factors reviewed included the potential for disruption of aviation patterns and radar equipment used by onsite and nearby facilities operated by the Air Force, Otis ANGB Airport, the Coast Guard and Camp Edwards. The Federal Aviation Administration (FAA) along with eight additional consulting agencies determined that the project would not significantly impact their missions.
DEVELOPING WIND TURBINES
Construction began in 2008 after nearly three years of planning and approvals. Now known as Wind I, the Fuhrländer 1500/77 wind turbine located adjacent to the LF-1 treatment plant began operation in December 2009, with a total installed cost of $5.8 million. Through two full years of operation, the turbine had produced more than 8,300-MWh of electricity, representing an avoided cost of more than $1 million. Wind I replaces approximately one-third of the remediation program’s energy usage.
Following startup of Wind I, AFCEC began scouting locations for Wind II. Due to changes in mission requirements for Air Station Cape Cod, however, the southwest corner of MMR was deemed inappropriate for additional utility-scale turbines of comparable size. AFCEC moved to select a location in the northern part of the installation, approximately 8-mi from Wind I, behind the PAVE PAWS radar facility.
The radar system covers 240° of horizon from north-northwest to south-southwest. Siting the turbines behind the radar created no interference with the mission. Yet these locations did require additional discussion with FAA, which led to a minor increase in the minimum vectoring altitude for Cape TRACON’s Area A. After further aeronautical studies, FAA determined that the turbines would have no substantial adverse effect on the safe and efficient utilization of the navigable airspace by aircraft or on the operation of air navigation facilities. An environmental assessment conducted for Wind II also resulted in a Finding of No Significant Impact, similar to the assessment for Wind I.
Construction of Wind II started in 2010. Two General Electric 1.5-77 wind turbines and a new 7.5-MV-A substation became operational in November 2011, with a total installed cost of $10.4 million. Through the end of 2012 (14 months of operation), they had produced over 8,000-MWh of electricity, representing an avoided cost of nearly $1 million. Wind II replaces approximately two-thirds of the program’s energy usage.
AFCEC’s robust optimization effort, along with the combined output of Wind I and Wind II for 2012, offset approximately 100 percent of the program’s energy usage, making the MMR project the first large-scale DOD cleanup program to be completely offset by renewable energy. And it is blazing a trail for further development on the installation.
A new wind turbine project is currently under construction at MMR, with a late 2013 estimated on-line date. Overseen by AFCEC, though not connected to the groundwater cleanup program, the two PAVE PAWS turbines will share a substa¬tion with Wind II, but the energy generated is going to be used to offset usage at the radar facility of 6 SWS at Cape Cod AFS. Moreover, the PAVE PAWS project was able to prepare a categorical exclusion during planning as opposed to a more-costly and time-consuming environmental assessment by tiering off the Wind II Finding of No Significant Impact.
Alternative energy generation such as wind turbines—and geothermal heating and cooling systems, which the Coast Guard is utilizing at MMR—are becoming viable solutions to the great energy demands of military installations, especially those where the solar energy opportunity may not be as abundant. The innovative work being done on Cape Cod proves just that.