Colorado Job Sites Go Green
The Leadership in Energy and Environmental Design program of the United States Green Building Council (USGBC) facilitates development of sustainable buildings nationwide. A number of Colorado general contractors are growing their expertise in constructing LEED-certified buildings as municipalities, educational systems and commercial developers specify green building.
Credits that can be earned in the LEED categories of Sustainable Site, Water Efficiency, and Materials and Resources contribute to a "green work site." The checklist for LEED New Construction divides credits into six categories with the following maximum credits: Sustainable Sites (14), Water Efficiency (5), Energy & Atmosphere (17), Materials & Resources (13), Indoor Environmental Quality (15), and Innovation & Design Process (5). A LEED-certified building earns 26–32 points, LEED Silver 33–38, LEED Gold 39–51, and LEED Platinum 52–69.
Design for buildings that apply for LEED certification starts with architects who are LEED-accredited professionals working with LEED AP individuals on the general contracting team. This design team, with an independent LEED consultant, submits a preliminary design phase review to the USGBC. After construction, the contractor working with the independent LEED consultant documents the credits and submits data to the USGBC for review and final ruling.
Four LEED Gold Projects
This article examines four projects either in construction or recently completed that were designed to LEED Gold standards.
Opus Northwest LLC of Denver built the LEED Gold Parkside Office Plaza at 349 Inverness between September 2007 and June 2008. MOA Architecture, Denver, designed the $9.5-million, 131,164-square-foot building, and Opus Architects & Engineers served as construction architects.
GH Phipps Construction Companies broke ground June 29, 2006, for the University of Colorado at Colorado Springs Science and Engineering building. Completion of the UCCS building will be late this spring. AR7 HooverDesmond Architects, Denver, designed the $45-million, 155,000-square-foot building to attain LEED Gold.
Saunders Construction Inc., Centennial, CO, started construction of 1900 16th Street near the Millennium Bridge in Lower Downtown Denver in October 2007 and is on target to complete the $105-million, 335,000-square-foot, 17-story office tower by mid September this year. Tryba Architects, Denver, designed this core shell structure to LEED Gold standards.
Heath Construction, Fort Collins, CO, completed the tenant finish construction at Council Tree Branch Library in Fort Collins in mid-February this year. Aller Lingle Massey Architects P.C., Fort Collins, designed the $1.6-million, 17,500-square-foot tenant finish to attain LEED for Commercial Interiors Gold certification. Total budget including materials, furnishings and building core is $6.6 million.
Sustainable Site Credits
The Council Tree Branch Library in Fort Collins occupies a unique space on the second floor of the Front Range Village shopping center. According to Kelly Karmel, Design Balance LLC of Missoula, MT, LEED consultant Fort Collins may pick up three sustainable site credits for performing the tenant finish in a LEED-certified building if Hoar Construction, Birmingham, AL, obtains LEED certification on the core and shell.
Parkside Office Plaza is adjacent to Cottonwood Creek. Approximately 3 percent of the site lies below the 100-year floodplain elevation. To address flood control concerns, Opus imported approximately 28,000 cubic yards of dirt to raise the western portion at least 5 feet above the floodplain. In the remaining land below the floodplain, the design placed landscaping, portions of the water-quality pond, a retaining wall, and sidewalk.
Saunders will be applying for a credit in Brownfield redevelopment at 1900 16th Street. This Lower Downtown (LoDo) area at the end of the 16th Street Mall once served as railroad yards, with a changing station at the new building location.
Graham Taylor, Saunders project engineer, observed, "The excavators found coal-filled dirt varied in depth throughout the square city block site from 2 to 3 feet to 18 feet deep. In total the contractor removed 58,900 cubic yards of dirt."
"We brought back some clean fill, but all and all it panned out well, as we needed to dig down a level for the underground parking," Taylor added.
Providing access to alternative transportation also earns credits in the sustainable site category. The 1900 16th Street building sits at a hub of public transportation served by the mall circulator buses and light rail. Also included in alternative transportation credits are providing bicycle storage, showers for riders, and parking for low-emission and fuel-efficient vehicles.
Parkside's access to public transportation is the Call 'N Ride program to a local light rail stop. Bicycle storage for 3 percent of building users is provided, along with shower and changing facilities for 0.5 percent of the building occupants. In addition, 20 preferred parking spaces (5 percent of on-site parking) is reserved for low-emission/fuel efficient vehicles.
UCCS provides bike racks for students and employees at the Science and Technology building plus showers/changing facilities for employees.
Maximizing open space also earns a credit in site development. At Parkside Office Plaza, the 91,493 square feet of open space is 135 percent more than the local zoning requirements.
Although stormwater control during construction doesn't earn credits in LEED, it's a prerequisite to apply for LEED certification.
"Proving we are meeting EPA and local jurisdiction requirements for stormwater control during construction is providing good documentation, such as taking photos and duplicating reports from weekly inspections showing we are not contaminating surrounding areas," observed Mike Hester, project manager for PH Phipps.
At Parkside Office Plaza, Opus met Douglas County's requirements for grading, erosion and sediment control plans. For example inlet protection was used on all sump inlets. Silt fence was used on the north, east and west sides of the site to filter downstream flows. Vehicle-tracking control was used at two locations to prevent construction vehicles from tracking debris onto public roadways. Erosion-control blankets were used on all slopes steeper than 4-1 ratio. A sediment basin was used to capture sediment from on-site flows. To prevent erosion prior to final stabilization, the contractor used surface roughening, temporary seeding and mulching.
Stormwater control during construction was less complex at 1900 16th Street. Saunders sloped the excavation for the parking garage into the site to contain any rainwater on site until it filtered into the earth. By the time the construction reached the street elevation level, the concrete deck prevented soil runoff. Rock bags at the curbs stop any sedimentation before it reaches the city sewer system.
Credits can be awarded for stormwater design in both quantity and quality control.
At UCCS there are stormwater detention ponds to filter water before it exits the site. At Parkside, densely grassed and landscaped areas maximize infiltration of stormwater and reduce pollutants. An extended detention basin is designed to drain water in 40 hours. It then travels to a regional detention pond.
Preventing a heat island effect from large paved areas and roofs also earns credits. The 1900 16th Street project has applied for reduction of heat island effect credit for eliminating a large parking lot by covering at least 50 percent of the parking through underground, stacked deck parking. Parkside prevented a heat island effect by covering 75 percent of the roof surface with white roofing material compliant with Solar Reflective Index values.
Water Efficiency and Construction Waste Diversion
Reducing water use for landscaping by 50 percent earns a credit, and using no potable water on landscaping earns another credit. Parkside achieved both of these points in water efficiency. Inverness has gray water, processed water not treated to the level of drinking water, available for landscape irrigation. Compared to a calculated baseline, the project requires 65.2 percent less water. This was accomplished with plant selection; zone planting of native grasses and beds of moderate water-demanding shrubs; plus an efficient irrigation system of drip heads, short-radius nozzles and state-of-the-art controls.
In the Materials and Resources category, companies can earn credits for diverting construction waste from disposal, one credit for diverting 50 percent of the waste and a second credit when 75 percent is diverted. GH Phipps is applying for three credits on its UCCS project by asking for credit for the waste diverted beyond 75 percent as a point in the Innovation and Design category. Currently the construction waste recycling is at 95 percent by weight.
How is the company attaining such a high rate?
"It's the planning and having processes in place and training the workers," Hester explained. "GH Phipps has always been an advocate of recycling and has proactively encouraged team members through employee incentives such as jobsite pizza parties."
At the Council Tree Library, Waste Not Recycling of Loveland, CO, brought in individual dumpsters for cardboard, dry wall and steel, and 95-gallon carts for office paper and daily plastic trash. In meetings Heath supervisors reviewed the recycling plan and asked each trade to do its part. Signs were posted in English and Spanish. Heath employees even checked the trash carts weekly to make sure everything that could be recycled was transferred to the dumpsters. The result is recycling above 90 percent.
"Our latest recycling report shows 91 percent recycled, and I am optimistic when we complete our reviews we will achieve 95 percent recycling," observed Jim Matlock, Health Construction project manager. "That means we can apply for an unexpected credit under the Innovation and Design for exemplary performance in Construction Waste Recycling."
Saunders is at 80 percent on its 1900 16th Street project, having recycled 4,000 tons of construction waste, according to Taylor. He adds that the company hopes to stay above 80 percent, though the tenant finish processes produce waste that is difficult to recycle. Saunders is using Allied Waste for wood, concrete and metal; Metal Management for some of the metal; and Horn Construction for concrete and asphalt recycling. Taylor estimates the company will have recycled 5,000 tons of waste by the end of construction.
Opus diverted 633.17 tons (81.493 percent) of site-generated construction waste from the landfill. According to Bernida Egging, LEED AP and PH Phipps project manager, the high tonnage on recycling is the addition of the concrete casting slabs to the recycled concrete.
Heath finished the Council Tree Library with 80-percent diversion of construction waste by recycling 30.56 tons of the 35.59 tons of construction waste.
While this article has discussed credits for green work sites, these four LEED projects are green for the life of the buildings. They contain high percentages of recycled and renewable building materials, local materials that reduce transportation costs, environmentally friendly materials, and mechanical systems that reduce energy use. The green work site is one component of the new sustainable building.
|Carol Carder is a Denver writer who covers Colorado construction for RMC.|