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CASE STUDY The General Theological Seminary of the Episcopal Church 175 9th Avenue Chelsea District, New York, NY Project Contact: Dennis Frawley, Owner’s Representative Background

The General Theological Seminary of the Episcopal Church covers an entire city block between 9th and 10th Avenues, and West 20th and West 21st Streets in the Chelsea district of Manhattan. The General Theological Seminary (GTS) is the oldest seminary of the Episcopal Church, founded in 1817 at this location. The campus consists of classrooms, dormitories, and faculty housing buildings and a chapel, in 16 landmarked Gothic Revival buildings and serene, gardenlike open space set in the heart of bustling Chelsea.

Since 1999, the Seminary has been restoring its landmark Chelsea Square campus, a masterwork of 19th century architect Charles Coolidge Haight. As part of this renovation project, GTS has decided to work towards decommissioning its boiler plant and convert to a campus-wide, energy-efficient geothermal heat pump HVAC system to provide the buildings with heating and air conditioning. The installation of a geothermal system will replace the use of the campus’ aging oil-fired boilers, and will provide centralized cooling to the campus for the first time in its history.

The Episcopal Church's General Convention passed significant "green" legislation encouraging the church at every level to reduce "energy use through conservation and increased efficiency, and by replacing consumption of fossil fuels with energy from renewable resources" toward the reduction of global warming. The Plan

The Seminary’s plan is to install as many as 22 standing column wells beneath the sidewalks surrounding the campus, to tap into the underlying bedrock and ground water system for heat exchange. Wells will be linked to seven mechanical rooms located throughout the campus, each housing 30-ton capacity Mammoth brand centralized, water-to-water heat-pumps that will produce chilled or heated water for distribution to fan coils and VAV’s located throughout the buildings. Two to four wells will serve each mechanical room depending on the space conditioning load of the buildings served.

Courtesy Beyer Blinder Belle Architects

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The Seminary's system will provide 850 tons of heating and cooling to 260,000 square feet of buildings. Upon completion, the Seminary’s system will be the single largest geothermal well field in the New York City area, if not in the northeastern United States. Ultimately, all of the campus buildings will be heated and cooled without the need for on-site fuel combustion. The Seminary estimates the new system will reduce its annual carbon emissions (”carbon footprint”) by more than 1,400 tons of carbon dioxide per year. The need for roof-level cooling towers and window air conditioners will be permanently eliminated, helping to preserve the architectural integrity of the campus. Simple payback to re-coup the upfront costs for the campus-wide installation program was initially calculated to occur in nine years; thereafter, the Seminary would realize significant net savings in its operating budget. Phase 1 of the project is complete and involved retrofit to geothermal during renovation of the 10th Avenue buildings for the new Desmond Tutu Education Center (below), and renovation of the Dodge and Kohne Halls (dormitories). Desmond Tutu Education Center

In May 2005, the Seminary began renovating three of its historic 19th century buildings located along 10th Avenue (Chelsea 8/9, Eigenbrodt and Hoffman Halls) to house two new centers, the Center for Peace and Reconciliation and the Center for Continuing Education, within the new Desmond Tutu Education Center. The renovation includes a modern facility with 60 guest rooms, large meeting areas, smaller break-out rooms, and the most up-to-date amenities. By June 2008, the geothermal system was completed and began to provide cooling to the Tutu Center.

Permit Applications, Filings, and Notifications

The presence of a new leg of the city’s public water supply tunnel system (Tunnel #3) directly beneath the site presented obstacles to permitting including the need to monitor “drift,” or deflection of the drill bit assembly at each well location. Certain wells had to be eliminated or moved further away from the tunnel alignment, and strict tolerances over encroaching towards the tunnel and neighboring properties were mandated by the city. Additionally, there were some community concerns over vibrations and noise levels during the drilling and potential for settlement of their townhouses. The Seminary organized and led several technical outreach meetings with the community and Community Board 14 to discuss the drilling program and thus alleviate concerns. Sensitive instruments were used to monitor vibrations during the drilling process and measures were taken to minimize and control noise. Prior to breaking ground, permit applications and notifications were filed with the USEPA (Underground Injection Control Program notification), NYSDEC Division of Mineral Resources (drilling permit), NYC DEP (discharge of groundwater to the city sewers during construction); and NYC DOT (Revocable Consent Agreement for permanent well installations and piping below the city sidewalks, street closings, and sidewalk closings). Separate approval to drill in proximity to the city water tunnel was required from NYCDEP as part of the Revocable Consent Agreement.

Courtesy Beyer Blinder Belle Architects

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building loop.

Standing Column Well System Operation

A standing column well system consists of three main parts: the wells and buried connecting piping (the “well loop”), an interior plumbing system circulating city water throughout the spaces to be conditioned (the “building loop”), and the water-to-water heat pumps located in the mechanical rooms. The heat pumps separate the “well loop” from the “building loop,” and contain their own refrigerant loop. In short, a standing column well is a re-circulating water well. A standing column well can be envisioned as a long, narrow glass of water with a straw inserted to the bottom. The “glass” consists of an 8” diameter borehole drilled through the soil and into the rock to a depth of on average about 1,500 feet at GTS. The drill bit and rods are removed and what is left is a self-supporting, open rock borehole. The shallow, soil portion of the borehole is supported by 10” or 12” diameter steel casing. The “straw,” referred to as the “Porter Shroud,” is a 6-inch diameter plastic pipe inserted into the completed borehole to the bottom. The bottom 50 feet of the shroud has holes drilled into it to act as an intake.

Because the well is open to the rock formation, groundwater from fractures and faults in the rock intercepted during drilling fills the well. A down-hole pump is installed inside the straw/shroud below the “standing” water level, near the top of the well, which circulates the groundwater through the system. During operation, the pump draws water up from the bottom of the well, sends it through the heat pumps in the building, and then releases it back into the top of the well. The water then must flow all the way down to the bottom where it is drawn back out the shroud intake and the cycle repeats. Heat exchange occurs at two points in the system, first in the heat pumps between the well loop and building loop, and second, between the circulating groundwater and the exposed rock in the well. During cooling mode in the summer, the heat pumps extract unwanted heat from the building loop, transfer it to the well loop, then it is released to the rock in the well. In the winter during the heating mode, the water flow is reversed, extracting heat energy from the rock, delivering it to the heat pumps which boost the temperature, then transferring it to the spaces to be heated via the

One of the seven 30-ton capacity heat pumps serving the Tutu Center

Drilling and Installation Program

During Phase 1, seven standing column wells were drilled; five to 1,510 ft depth, one to 1,460 ft, and one to 1,800 ft. The well drilling progressed in two phases. Phase 1 was the installation of the steel surface casing through the soil and into shallow rock. Total depths of surface casings installed ranged from 85 to 107 ft below ground surface. A dual rotary drill rig (Barber Rig) was used for the surface casings, which allows simultaneous drilling and casing installation. A 20” steel conductor casing was first advanced to top of rock to stabilize the unconsolidated overburden, to facilitate the surface casing installation and deep borehole drilling. The Phase 1 drilling started on 14 August 2007 and was completed on 31 October 2007. Phase 2 was the open-hole drilling within the deeper competent bedrock. A Shramm TW685 model, air rotary drill rig was used. A “stiff” drill string was employed to drill as straight as possible to achieve the tolerances set under the Revocable Consent Agreement and state drilling permits. The stiff drill string consisted of (from bottom to top) an 8-3/4” carbide button bit and fluted down-the-hole percussion

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hammer assembly, one 20-ft long square stabilizer, two nominal 8-5/8” diameter and 20-ft long drill collars, followed by 25-ft long nominal 6.5” diameter drill rod sections. Phase 2 drilling started on 8 October 2007 and was completed on 29 April 2008. The entire drilling setup comprised the drill rig, auxiliary air compressor, air booster, a support truck to store drill rods, a plastic lined roll-off container to contain drill cuttings and water generated during drilling, and associated pumps and piping.

Installing surface casings along 10th Avenue Deep rock drilling setup along W. 21st Street for Dodge & Kohne dorms

Because of the tunnel beneath the site, the city Revocable Consent Agreement required borehole deviation surveys to be performed for each well at various depths and frequencies. A specialty subcontractor working for the driller performed the deviation surveys using a down-hole gyroscope. Borehole geophysical and video logging was conducted at selected boreholes. The primary objective was to document baseline rock borehole wall conditions prior to installing the shrouds. The logging results also confirmed the depths of fractured rock zones noted by the driller during drilling, and generally contributes to establishing the baseline conditions around the well field. The U.S. Geological Survey also conducted supplemental geophysical logging at selected wells as part of a collaborative program with the city. The geophysical logging included groundwater temperature, conductivity, resistivity, caliper, optical televiewer, and gamma logs.

Rock conditions at certain wells required mitigative measures to stabilize the borehole walls (to allow the wells to remain as open boreholes for the life of the system). For Well 21, the driller had to install a permanent 10” steel casing (sleeve) to a depth of 164 ft below grade to stabilize a fractured bedrock zone. For Well 22, a steel sleeve had to be installed to a depth of 175 ft for the same reason (see illustration on next page). After the hole was drilled, it was found that the sleeve had cut off groundwater infiltration into the borehole; therefore, holes were punched in the sleeve using a down-

Installing the straws (Porter shrouds); l-Dodge Hall, r-Tutu Center.

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hole perforating device, which succeeded in allowing the bedrock groundwater to fill the borehole as the other wells. For Well 19, a thin, shallow fractured zone was stabilized using a 20-ft section of slotted stainless steel well screen. This physically supported the fractured rock but still allowed groundwater inflow for bleed purposes.

North (W. 21st St.) South (W. 20th St).

Construction of Tutu Center wells, north-south line along 10th Ave. (upper 250 feet of well/borehole only shown)

Three separate 24-hour groundwater pumping/drawdown tests were completed, one test for each mechanical room grouping of wells. The objective of the tests was to establish well yields, thus maximum sustainable bleed rates. Well yields varied, ranging from about 1.6 gpm to about 15 gpm. Wells serving separate mechanical rooms were found to be hydraulically connected to one another. Therefore, it was important to understand the rock aquifer response during bleed cycles for each well grouping alone and bleeding together, since the effects on water levels is compounded as more wells start to bleed at the same time. On a parallel track with the drilling work, the interior spaces were renovated and fitted out for the geothermal system. The heat pumps were delivered and installed in the mechanical rooms, and in March 2008, two of the wells went online to provide heating for Dodge and Kohne Halls. By June 2008, the remaining five wells were brought on line and began to provide cooling for the Tutu Center building. The systems will be undergoing balancing and fine-tuning this fall.

Completed wells with reconstructed sidewalks; l-Tutu Center, r-Dodge and Kohne

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Ninth Avenue Development

In conjunction with The Brodsky Organization, a prominent NYC developer, the newer campus structures located along 9th Avenue are being demolished and replaced with construction of a new seven-story mixed-use residential building. The Seminary will retain first floor and basement level space to house a new state-of-the-art library and archive storage. The Seminary’s space in this new building will be heated and cooled with geothermal heat pumps, served by a new well to be located along the 9th Avenue side of the block.

Courtesy Polshek Partnership

HIGHLIGHTS OF SUCCESS OF PROJECT

The Seminary has stated that as a teaching institution which attracts students from all parts of the US and many other countries, they are uniquely positioned to demonstrate to the Church's future leadership that environmentally sensitive technology is cost-effective and achievable in the here and now--even in relatively expensive settings, such as New York City--and with cherished, historic structures nearby. With General's geothermal project as a model, the next generation of church leaders will be better informed and able to play an influential role in promoting understanding of and support for environmentally sensitive energy development. Some of the project features that the Seminary attributes to the success of the project to date include the following:

• The success of the architect (Beyer Blinder Belle) to effectively incorporate the geothermal system elements into the historic structures while preserving the buildings’ historic charm, both interior and exterior.

• Close coordination by the architect with the various engineers and consultants.

• Participation of professional geologists and other experts knowledgeable of deep bedrock conditions in the city, geothermal well drilling methods and construction, and drift monitoring.

• Field inspection by qualified experts to provide real-time consultation on potential well performance and the need for borehole mitigative measures.

• An overall experienced team of engineers, consultants, and contractors.

• Timely communication of field conditions between the Owner, field team (driller, construction manager, geologists, geotechnical engineer), and the design engineers (mechanical and geothermal engineers).

• Timely consultation and coordination with the city and state regulators as unanticipated ground conditions are encountered which require modified field procedures.

Simple payback was recalculated after ground breaking to be in the 19-year range, as a result of several unanticipated conditions, including increased measures to appease the community (monitoring for vibrations and noise), increased field project duration and drilling costs due to extensive drift monitoring relative to the water tunnel, generally higher drilling costs due to project complexity and liability over the tunnel, higher interior retrofit costs than originally estimated, and increased consulting fees to appease the regulatory agencies and community concerns.

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LESSONS LEARNED • Research whether or not the governing agencies are familiar with and have regulations in place

for geothermal well drilling; if not, anticipate significant delays and costs to educate and negotiate with them

• If possible use same engineer and mechanical contractors for indoor and outdoor portions • Clearly define the loads and communicate early on to all parties • Know minimum flows required by heat pumps versus what the well pumps deliver under varying

head conditions • Be prepared to drill more or deeper wells to meet the demand contingent on rock conditions • Prepare for contingency measures to stabilize rock borehole • Remain flexible, if possible, with matching wells with specific buildings, based on the loads and

individual well performance • Establish a surface casing grouting plan before the work to manage excess liquids and cement

grout generated • Don’t skimp on system monitoring and controls • Be proactive and inform your neighbors about the pending construction work whether or not you

have to by the agencies

For more information contact:

• Dennis Frawley, Owner’s Representative/Redevelopment Project Manager, General Theological Seminary, 212-243-5150, x254

• John Rhyner, Senior Project Manager, P.W. Grosser Consulting, 631-589-6353