Owner: Dare County Water Department
Where: Kill Devil Hills, N.C.
Project: Roanoke Island Water Treatment System Expansion
Procurement method: construction manager at risk (CMAR)
Guaranteed maximum price (GMP): $20,387,815
Expected completion date: June 2012
Often called the Lost Colony, Roanoke Island was the first English colony settled in the New World in what was then Virginia. The tiny island — just 11 miles long and 2 miles wide — is now part of North Carolina's Dare County. Nestled between the mainland and barrier islands near Nags Head, the island is a popular tourist attraction for both its history and natural beauty. The Outer Banks beaches are a coveted destination in the summer, when the island's population swells from 10,000 year-round residents.
Saltwater intrusion is an ongoing challenge in the Outer Banks, but Roanoke Island presents a particular problem. The Dare County Water Department's 6-mgd Skyco ion-exchange treatment plant serves the town of Manteo and limited unincorporated areas in the central part of the island, but residents in northern Roanoke Island, the southern area of Wanchese, and other unincorporated areas rely on private wells supplied by two aquifers. Tourist attractions including the Lost Colony, Fort Raleigh, and an historic fishing village in Wanchese also are in these unserved areas.
For many years, the private wells supplying these areas have experienced low water levels and saltwater intrusion, a common problem where groundwater is pumped from coastal wells. Because the private wells provided no reliable fire protection, public safety was another concern. Local fire departments had asked the county board of commissioners to expand public water service to ensure adequate supplies for fire suppression.
The county replaced many of the shallow wells in Wanchese with deeper wells in the 1980s, but saltwater again became an issue in the late 1990s. A study concluded that well water quality was deteriorating because the replacement wells were poorly constructed. But extending municipal water service to the rest of the island, which would be the county's largest water services project since the early 1950s, wasn't without issues, either. There was the potential impact of widespread construction on tourism, the island's primary industry, as well as wildlife and wetlands, to consider. Like many communities, Dare County faced revenue shortages and budget concerns. Finally, retrofitting homes — some 50 years old — with new pipes would pose logistic and communications challenges.
Modeling strategic improvements
For more than 20 years, the county has collaborated with CDM Smith on water supply, treatment, and distribution projects. In 2005, the Water Department enlisted the consulting engineering firm to conduct a system planning study to determine what improvements were necessary to expand water distribution on Roanoke Island. The firm developed existing and future demand projections, created a hydraulic model, and recommended infrastructure improvements based on projected water demands through 2025.
To assess the county's needs, a computer model of the distribution system was developed using billing data, population projections, parcel data, and land use data. Projected conditions — including average day, maximum day, maximum day plus fire flow, and peak hour demands — were simulated and observed. Because the Skyco plant's existing storage tank and mains wouldn't meet the projected daily demand of 2.83 million gallons, the firm's 2006 recommendations included:
Minimum fire flow capacities were determined based on standards by the Insurance Services Office (ISO), a private rating service that insurance companies use to establish fire flow requirements for communities. Flows are based on maintaining a residual pressure of 20 psi to overcome frictional losses through the hydrant and hoses and maintain positive pressure on the suction side of a fire department pumper truck.
For residential areas, ISO recommends fire flow capacity of no less than 750 gallons per minute (gpm) for one- and two-family dwellings not exceeding two stories in height and spaced 31 to 100 feet apart. This describes the majority of structures in the service area. Requirements for commercial and industrial areas are generally higher, so CDM Smith developed specific flow requirements for commercial and industrial developments as well as public facilities such as schools, hospitals, and nursing homes.
Structuring bid packages
In 2009, the Dare County Board of Commissioners saw an opportunity to address the island's water issues and reinvigorate the economy. Aided by a $500,000 North Carolina Rural Economic Development Center grant, they decided to move forward with the proposed expansion. In addition to providing high-quality water, the project would support local businesses and create much-needed jobs on the island.
In March 2009, through a qualifications-based selection process, the Water Department selected CDM Smith as the design engineer; and in August 2009, through a separate qualifications-based selection, selected CDM Constructors as the construction manager at risk (CMAR).
“From experience with three previous projects, we believe CMAR provides a high level of coordination early in the project, resulting in improved schedule management and controlling project costs,” says Dare County Finance Director David Clawson. “In addition, references are essential for firms to be able to obtain future work — an incentive to provide a quality project.”
In November 2010, at approximately the 30% design level, CDM Smith's team developed a guaranteed maximum price (GMP) of $20,387,815; and in January 2011 began construction.
The CMAR approach offered a number of advantages over traditional design-bid-build methods. Establishing a GMP early, while the bidding environment was favorable, ensured the county wouldn't be affected by economic factors that could increase costs. These savings will ultimately be passed on to ratepayers.
In addition, the procurement method provides flexibility that streamlines the design process, which at 50% completion is estimated to have saved $900,000. In one instance, the CDM Smith team coordinated with electrical and mechanical pump room subcontractors and Water Department employees to develop a sequence of work that required only short-term shutdowns. Existing water systems remained operational while the new pumping system was installed, avoiding costly bypass pumping and saving nearly $100,000. And in several areas of the distribution system, the firm's team worked with pipeline subcontractors and the local DOT to make minor revisions to the alignment and reduce pipe lengths or repaving.
These savings have helped offset other unforeseen conditions and keep the project on budget. Unexpected issues included pavement that was found to be 12 inches thick from several overlaying treatments over the years. In other instances, work restrictions or additional paving were needed to work around areas where easement couldn't be obtained without condemnation.
The method also generated subcontracts in a size range that was both attractive to and manageable by local contractors. The project was divided into five design packages that were then divided into more than 15 separate procurement and construction packages. The first design package included the pump room improvements and new ground and elevated storage tanks. The remaining four design packages included the 56 miles of water main, which were divided up geographically.
It's worked: At the halfway point, nearly 85% of the work has gone to regional subcontractors and allowed approximately 60% of the construction work to be performed by subcontractors located in Dare County.
With a great deal of construction taking place on private property, the level of communication CMAR requires has greatly facilitated resolution of right-of-way issues. The CDM Smith construction team and county quickly identified areas where easements were unavailable. Working closely with pipeline subcontractors and the local DOT has averted costly condemnation proceedings. To date, the county hasn't had to condemn a single easement. All easements have been obtained through negotiations or avoided by modifying construction means and methods.
Throughout the project, construction continues to be guided by the county's desire to protect the island's wildlife and wetlands. An environmental assessment was performed to identify habitats and areas considered environmentally sensitive. Where possible, trenchless technology is being used to install pipelines — under a stream or designated wetland, for example — in ways that don't disturb sensitive areas.
In November 2011, residential customers were brought online; and in December the Dare County Justice Center and municipal complex was connected to the system — both key milestones. When finished, the project may provide the additional benefit of lowering fire insurance premiums for county residents and businesses.
—Irby (firstname.lastname@example.org) is an associate with CDM Smith, the engineering consulting company formerly known as CDM; Flatt (email@example.com) is the Dare County Water Department's utilities director; and Hernandez (firstname.lastname@example.org) is a principal with CDM Smith.