American Academy of Environmental Engineers

INTEGRATED APPROACH

Dual Solution: The City of Santa Rosa, California sought an environmentally responsible way to dispose of recycled water without increasing discharge to the Russian River. Calpine Geothermal needed water to recharge the aquifer at the Geysers, the world’s largest steam field. The solution was a 40-mile pipeline conveying 11 million gallons of recycled water per day across the Santa Rosa plain and Alexander Valley and up 3,300 feet into the Mayacmas Mountains. From the terminal tank, Calpine distributes the water and injects it into 4,000-11,000-foot-deep wells to recharge the steam field.

Green Electricity: Compared to electricity generated by natural gas-fired power plants, the additional 85 megawatts of geothermal electricity reduces emissions of carbon dioxide by 570 million pounds and reduces nitrous oxides by 253,000 pounds annually.

Pollution Controls: Extensive erosion control measures prevented sediment from entering sensitive streams. In the valley, contractors controlled dust to protect crops. In the mountains, contractors monitored dust levels to protect workers from naturally occurring asbestos. Also, contractors returned excavated serpentine rock containing asbestos, chromium, nickel and lead to original and similar locations to avoid shipping hazardous waste.

Reduced Environmental Footprint: The design eliminated external reservoirs or tanks at the three mountain pump stations. The Bear Canyon pump station tops an underground one-million-gallon reservoir used to dampen surge pressures and enhance system control. Pump stations also blend into their surroundings. (For example, the station in the Audubon Wildlife Sanctuary is set into a hillside.)

QUALITY

Knowledgeable Team: “The project could easily have stalled in implementation were it not for the strong technical expertise and the close teamwork with the client and between team members,” says Jane Rozga, CH2M HILL construction manager. Challenges included installing large pipe with water pressures higher than industry standards through environmentally sensitive areas, tourist corridors, and in close proximity to valuable vineyards.

Flexible Design: “We designed the pipeline to accommodate future technology,” says Gary Nuss, CH2M HILL program manager. Although the interior monitoring “pigs” used in the oil and gas industry are not yet available for water pipelines or large diameter pipelines, large ball valves that open fully instead of standard butterfly valves will accommodate this technology.

With an ultimate capacity of 40 mgd, the 48-inch-diameter pipeline can provide additional irrigation along its valley route. Variable speed pumps allow adjustable flow rates to increase pumping during low rate periods or respond to specific water needs. Operators control the system remotely from laptop computers

Completion and Operation: The expected project completion date was December 2002. Despite numerous project changes and delays related to litigation and acquisition of right-of-way, the project was completed and on-line to meet the city’s commitment to the Regional Water Quality Control Board to develop an alternate reclamation system by December 31, 2003.

The project has been on line for more than a year, successfully delivering water and generating power. The Geysers operations staff is pleased with the system’s ease of operation.

ORIGINALITY AND INNOVATION

Unique System: The Geysers steam field is the world’s only geothermal system to use wastewater to replenish its dying steam fields.

Earthquake Protection: Extensive geologic work identified two active faults on the pipeline pathway. Sensors and isolation valves at the faults will shut down the pipeline if an earthquake of 5.5 magnitude or greater occurs. These systems are common in small piping systems carrying chemicals, but not typical for high-pressure water transmission lines.

Slide Protection: The pipeline crosses 1,000- and 700-foot-wide slide areas. Spring-loaded pipe sleeves connected by ball joints allow the pipeline to expand, contract and rotate to reduce risk of pipeline rupture when soils slide. State-of-the-art inclinometer sensing equipment monitors soil displacement, allowing pipeline stresses to be anticipated so the pipeline can be realigned before it ruptures.

Quiet Pumps: To keep noise whisper soft, the design replaced traditional air conditioner cooling for the five 1,000 HP pump motors at each pump station with water cooling derived from the pumped recycled water.

COMPLEXITY

Environmentally Sensitive Alignment: The pipeline would cross environmentally sensitive areas of premier vineyards and pristine mountain wilderness. By adjusting the alignment, the design avoided rare plant colonies and all but a dozen of the 1200 private properties. The design sequenced construction to avoid impacts on raptors and rare nesting birds.

Community Relations: Since the public opposed every alternative considered, the project required extensive communications. Mailings from a project database of more than 3,000 informed property owners, residents, and affected agencies. Other communication included Web sites, permission-based e-mail broadcasts, and contact management software.

Construction Challenges: Bike races, triathlons, year round tourist traffic, and seasonal harvest traffic challenged the schedule. Delays to grape trucks were limited to five minutes, and pilot cars led traffic through construction zones in tight corridors.

Crossing the Russian River twice without environmental impacts required microtunneling from up to 100-foot-deep shafts. In 15 tunnels crossing rivers, creeks and natural features such as valuable oak trees, the pipeline is double cased to protect the environment.

SOCIAL & ECONOMIC ADVANCEMENT

Savings: By changing the preliminary alignment to avoid several slide areas and a narrow county road, the design team saved the owner an estimated $10 million in construction costs out of an original budget of $100 million. The final construction budget was $130 million and the full project cost $200 million.

The three mountain pump stations pump in series eliminating costly tanks between them. Any interruption of 24/7 pumping would have placed the weight of 10 miles of water on the pipeline. The added steel thickness for strength would have increased pipeline cost dramatically. To dissipate pressure, pipeline release valves permit controlled backflow into the Bear Canyon underground reservoir.

Local Benefits: The plan divided construction into nine smaller contracts, four going to local contractors. The contractor worked at night on two miles of the mountainous Pine Flat Road to maintain residential access and maintained a radio communications system to avoid collisions.

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