SPECIAL GREEN SOLUTIONS REPORT
PROJECT CASE STUDY:
Watering Death Valley Calls for Fertile Ecological Engineering
As published by CE News Magazine
Furnace Creek Water System, Death Valley National Park, CA
National Park Service, Denver, CO
Psomas, Los Angeles, CA
ZFA Structural Engineers, Sacramento, CA
CRM Architects & Planners, Inc., Sacramento, CA
Erick Ammon, Inc., Salyer, Calif.
A.T.E.E.M. Electrical Engineering Inc., Sacramento, CA
Design of a new potable and non-potable water supply system for the Furnace Creek area in California’s Death Valley National Park offered a number of opportunities to implement the principles of sustainable design. The National Park Service is rebuilding the water system to implement water conservation measures and to protect natural resources by allowing the springs to flow down and nourish a wetland and the riparian areas around it.
Furnace Creek is the recreational center of Death Valley National Park, the lowest, driest and hottest valley in the United States. This is also one of the few places in Death Valley where there is a series of natural springs. The springs supply water to the historic Furnace Creek Ranch and Furnace Creek Inn, as well as a date tree farm, golf course, swimming pools, and for irrigation purposes. The springs provide water to offices and residences for the Timbisha Shoshone Tribe and for National Park Services administrative offices, Visitor’s Center and three campgrounds. The springs are also the water source for wetlands and riparian areas throughout the Furnace Creek area.
Dual water collection and distribution system
The new water system consists of a dual water collection and distribution system and a water treatment system for potable water use. Three new, deep groundwater wells will supply the potable water, and a new collection gallery, in conjunction with an existing collection system, will provide non-potable water to the area.
Designed by Psomas, the $7-million project includes the following:
- three production wells supplying a total of 750 gallons per minute (gpm);
- five monitoring wells for historical groundwater monitoring;
- 6-inch, 8-inch, and 12-inch potable and non-potable distribution piping;
- a 600-gpm (1 million-gallon-per-day (mgd)) reverse osmosis (RO) facility consisting of a three-array, two-stage system—two duty arrays will produce 0.5 mgd each;
- electrical and instrumentation for the well sites and the RO system, including a supervisory control and data acquisition system and photovoltaic system for the RO building and repeater site; and
- a 900-gpm collection gallery for non-potable water.
The collection gallery for non-potable water was designed to capture 900 gpm with an array of slotted collection pipes, sandy gravel filter pack, and a headwall. Based on historical data, the water surface elevation fluctuates throughout the year, with the lowest elevation occurring during late summer. The collection gallery was placed below the lowest water surface elevation. The potable water system consists of three wells, which are located 3,500 feet up-gradient from the springs and at a depth of 225 feet.
The RO treatment system will be used to reduce the levels of arsenic and fluoride in the potable water. The groundwater water quality exceeds the maximum contaminant levels of the state primary drinking water standards for arsenic and fluoride, with levels of 0.024 milligrams per liter and 3.6 milligrams per liter, respectively.
Protecting and preserving resources
The Furnace Creek Water System includes several sustainable design features, the most obvious one being the very nature of the project itself. By relocating the potable and non-potable water supply, the park can restore and protect the historic wetland and riparian habitat at the existing Furnace Creek Springs, which support several special-status species. The new collection gallery for non-potable use will be located downstream of the springs in the Lower Furnace Creek Wash, letting water first flow over the wetland and riparian areas, allowing them to grow and flourish. The water will then percolate back into the ground, combine with the existing groundwater aquifer, and flow into the collection gallery.
The RO treatment building has a number of green features. The facility will have a 21,000-watt photovoltaic panel system on the roof, which will provide sufficient energy to power the treatment plant during normal operations. The photovoltaic panels are suspended above and shade a portion of the roof, which provides a floating roof shading effect. The building is earth-sheltered with the south side of the building partially below grade. In addition, the thermo-siphoning roof geometry of the RO building provides a passive ventilation system—the walls are louvered and the roof is low on the south side and high on the north side, encouraging air to flow up the underside of the roof. The building’s concrete slab contains 15 percent fly ash, which provides a significant benefit for the environment by avoiding landfill disposal and increasing the durability of the concrete.
The dual water system has many sustainable advantages. The non-potable water will be used for golf course irrigation, landscape irrigation, water features at the Furnace Creek Inn, and the flow-through swimming pools. This water will not be treated, thus reducing treatment costs to the park. In addition, the potable water system was designed to minimize the use of pumps, thereby reducing use of electricity.
The RO treatment unit requires the feed water inlet pressure to be approximately 100 pounds per square inch (psi) to operate effectively. Wells were located at an elevation to provide sufficient pressure to the system while only using minimal pumping head. The discharge pressure out of the well sites is approximately 25 psi, with the remaining pressure being created by the elevation difference between the well sites and the treatment plant.
Death Valley National Park is home to a number of cultural and natural resources, so it is difficult to find locations within the park where construction will not disturb resources—cultural, natural, or archeological. Several Native American sites in the area had to be considered in project siting and in planning construction. An archeological monitor was required during staking of the facilities and during excavation and installation of the water pipeline along a previously undisturbed route in the park.
Drainage also has been an ongoing challenge. There are many washes along the system and care is required to not disturb them so they will provide adequate drainage in event of a flash flood.
Finally, this project demands coordination with many agencies and stakeholders, including the Timbisha Shoshone Tribe, Xanterra Parks and Resorts (owner and operator of the Furnace Creek Inn and Furnace Creek Ranch), the National Park Service and its various divisions, Southern California Edison, Inyo County, California Department of Public Health, The California Department of Transportation, the Regional Water Quality Control Board, and the State Historic Preservation Office.
However, the outcome will be well worth the challenges when this important National Park Service recreational area receives a new water system designed to respect and protect the surrounding environment.
Author Michael G. Thalhamer, now retired, was vice president and principal with Psomas, and was project director for the reconstruction of the Furnace Creek water collection system. He has over 40 years of experience in planning, design, construction, and operation of domestic water systems.