By Tracy Correa
Last week, 365 trees were planted in a one-time 54-acre quarry site near the popular Bass Lake resort in Madera County. Construction crews, along with their heavy machinery, are packing up and leaving.
The seismic retrofit of Crane Valley Dam – which began October 2010 – is in its final stage.
Except for a few “punch list” items, dam construction is largely done, said PG&E’s Jeff Matthews, restoration project manager for the Crane Valley Dam seismic retrofit.
Formal completion approval still must come from regulatory agencies, which must sign off on the project.
With dam construction primarily finished, restoration of the quarry site just west of the dam is the primary focus. It’s this area where rock was mined for use in building up the dam’s upstream and downstream buttresses. Also being restored is a smaller 7-acre section downstream east of the dam.
“We are planting approximately 30,000 trees and plants of various species,” said PG&E’s Matt Brown, restoration work supervisor. “The plan is to return the site back to a natural forest, similar to what existed at the site prior to project implementation. This includes pine, cedar, oak, grass, and riparian vegetation grown from native seed collected from the site prior to construction.”
Making sure the dam meets seismic standards
The construction project was done to strengthen the dam in order to meet today’s stricter seismic standards. The retrofit also ensures future, safe recreation on Bass Lake, which continues to attract visitors even though the water level had to be lowered about 10-feet below (recreation season normal) maximum during construction.
PG&E is responsible for managing Crane Valley Dam and Bass Lake, the reservoir formed by construction of the dam as part of its Federal Energy Regulatory Commission License supplying clean hydroelectric power to PG&E customers and providing recreational opportunities to nearby residents and visitors to the area. It is one of more than 100 reservoirs that PG&E manages as part of its hydroelectric portfolio.
Following construction, the crest of the dam is now about six feet higher, providing for additional dam safety. The improvements were built up using about 300,000 cubic yards of rock – most of it from the on-site quarry just west of the dam; the remaining rock was brought in from a quarry about 30 miles away.
At the height of construction nearly 50 workers from a number of PG&E contractors were at the site. Now, they are moving out and taking with them some of the trailers that served as on-site offices.
Matthews said ongoing restoration of the large quarry area near the dam has involved meticulous work and close coordination with the U.S. Forest Service
Planting native trees and plants
The land affected had to be re-contoured and the soil amended and readied for new plantings. Hydrological features such as creeks had to be built to tie into existing water features. The plants are coming from Intermountain Nursery, which had an entire section of its nursery in nearby Prather devoted to growing and nurturing the native trees and plants in preparation for relocation to the former quarry.
“This is a first-class restoration project and PG&E is pulling out all the stops,” said Brown. “The resources that we are putting into the reforestation effort — including the overhead irrigation, planting methods, and plant protection — is well above industry standards.”
In a few weeks, PG&E – working with the Department of Fish and Game — plans to turn its attention to the lake and stock it with more 2,000 pounds of fish, including rainbow trout. This is the first of several planned fish stockings.
The construction, restoration and fish stocking are all part of the effort to ensure that visitors will continue to enjoy Bass Lake.
“The goal is, that within years to come, it will look like nothing has changed,” said Matthews.
E-mail Tracy Correa at Tracy.Correa@pge.com