Engineers are preparing to punch a $13-million, 6,300-foot-long tunnel through Cowles Mountain in Mission Trails Park, the highest peak in San Diego, as part of a 60-mile water pipeline project for the County Water Authority.
The tunnel is a sensitive element in the overall $530-million project to serve county growth by building a water delivery system that starts at Lake Skinner in Riverside County and ends at Lower Otay Reservoir east of Chula Vista.
Environmentalists and lovers of Cowles Mountain, popular with hikers and distinctive for the white "S" shaped into its side by college students decades ago, are generally grateful that officials chose to bore a 10.6-foot-diameter tunnel rather than chomping across the mountain's western face with a trench.
John Zona and his Dalmatian, named Captain January, stood on a craggy hilltop early Monday and watched a helicopter gingerly drop a drill rig and other equipment as engineers began exploring how and where to chew a tunnel through granite.
"I think it's a wonderful idea they're going underground rather than over the top," Zona said. A trench "would take away all the privacy and commercialize the mountain a bit," he said. Zona is a retired civilian employee for the Army who has lived in the Cowles Mountain area since 1982.
With a walking stick in one hand and Captain January's leash in the other, Zona often finds peace on the mountain. "Since I've been here, I estimate I go up there 200 times a year. I know every inch of that mountain," he said.
The decision to bore a tunnel was made after water authority officials met with the community and became convinced that alternatives were unacceptable.
With a tunnel, "you don't have a scar, and we were concerned about falling rocks" during grading, said Mike Stift, a senior civil engineer with the water authority. "Basically, we're tunneling through the whole mountain. To do a pipeline from North County to South County is a pretty ambitious project."
Environmentalists and community groups appear satisfied with the tunnel option, which is supported by the Mission Trails Regional Park Task Force, the Mission Trails Regional Park Citizens Advisory Committee, the San Carlos Area Council and the Navajo Community Planning Group. The San Diego chapter of the Sierra Club has taken no position on the tunnel.
"This was the best alternative environmentally," said Lou Ann Holmes, an aide to San Diego Deputy Mayor Judy McCarty, whose district includes the park.
To design the tunnel, water authority engineers will explore by first drilling five core holes to depths of 75 to 185 feet, afterward capping the holes. Actual boring will begin in early 1992 and take a year to complete.
Mark Stadler, a spokesman for the water authority, said neither the drilling nor the tunneling will interfere with recreation on the mountain. However, some residents in neighborhoods in the pipeline path leading to the mountain have told water officials at hearings that they are concerned about their streets being temporarily dug up for the pipe.
"They've been real vocal about making the disruption as little as possible," said Stadler, adding that a final pipeline route through neighborhoods hasn't been selected.
The tunnel is part of an 8-mile segment of pipeline that will cross parts of San Diego, La Mesa and Lemon Grove. A water authority report acknowledges the potential inconvenience, saying that pipeline construction "will be extremely difficult and disruptive to the neighborhoods in which it will finally be located."
However, the water authority, which provides 90% of the county's water by supplying six cities, 17 special districts, the county and Camp Pendleton, believes the 60-mile pipeline is critical to serving the county and meeting growth demands.
Some of the authority's pipes were laid in the 1940s and occasionally operate at peak capacity during warm months, forcing some agencies to rely on their stored water. By upgrading the existing water delivery system, it can receive water from Southern California's mammoth Metropolitan Water District and prepare for growth.
Stift said the county population was about 2 million in 1985 and is projected to reach 2.3 million next year and slightly more than 3 million by the year 2010. The overall project will be completed by 1996 and is funded by bond sales and a special assessment per parcel that was authorized by the state Legislature.