A presentation about the status of tunnel rehabilitation projects for the Oakdale Irrigation District was given by Contracts/Special Projects Manager Gary Jernigan at the OID Board of Directors regular meeting on Dec. 18.
Jernigan’s PowerPoint addressed the Two-Mile Bar Tunnel and South Main Canal emergency response plan. He discussed the history of failures in the district for the past 100 years and gave details of each of the failures where information was available and costs associated with them. He also translated some of those costs into today’s dollars.
Jernigan showed a satellite photo with potential future and past failure sites on South Main locations downstream of Two-Mile Bar. Several red lines highlighted the three high hazard areas on the canal and a yellow line showed the location of the new 5,860-feet tunnel planned to bypass the approximately 7,100 feet canal section that contains about 2,000 feet of high hazard areas, of which about 200 feet could fail at any time.
He shared photos of some repairs that were made over the years and commented on the present condition of those repairs. He said the South Main stabilization projects from Goodwin Dam to Two-Mile Bar totaled about $6 million in rehab and that area is in generally good condition but noted there are still some unknowns about underlying conditions and the stacked rock construction will always be a problem.
Jernigan also shared multiple photos of the landscape/topography of each of the high hazard areas. He reported that from Two-Mile Bar to Tunnel #7 the general condition is poor. He discussed the type of loose, sediment material in these areas, as well as rock overhangs and the problems they present to the canal. He noted that at the end of every irrigation season, they find rocks and debris at the bottom of the canal and a big rock fall or landslide is expected at some point.
“Right now, as of today, we’re 50 percent complete on the design (for the tunnel),” Jernigan said.
He added that geotechnical investigations are 95 percent done, the final design is 90 percent complete and budgeted for 2013, the easements are also nearly complete. He noted that the permitting has been “a big education.”
Jernigan told the board that there are basically two ways to build the tunnel: planned or emergency. A planned tunnel construction will cost about $16 million. It would take about three months to get started and the construction schedule would be 18 months. Emergency tunnel costs will be about $19 million and the construction would be eight months.
He added that safety is an issue for dealing with canal failures and reviewed the costs and other details of lesser and catastrophic failures in that part of the system. There was discussion amongst the board and General Manager Steve Knell regarding if there were a failure during irrigation season, how farmers who rely on the South Main would fare. Knell said he believed permanent crop loss would be minimal as there are a lot of ground water pumps in that area but people with pastures and possibly dairies and grains would have issues. Director Al Bairos asked when the last time those farmers cranked up their deep wells and stated that some could have been out of operation for 20 years or more.
The new tunnel would not increase the capacity of the South Main, just the reliability. Knell said that there is $8 million in a tunnel reserve account and the plan was to feed the tunnel fund through water sales, and pay as they go on the tunnel but OID currently doesn’t have any transfer contracts.
In other discussion, the board talked about the upcoming Tri Dam meeting agenda item about establishing a maintenance reserve in the case of a catastrophic failure there. Director Frank Clark posed several questions asking if a reserve was needed, how much would it be, how long would it take to fund it, and how would it be funded. He also wanted to know what kind of assurances OID and its Tri Dam partner and sister district South San Joaquin Irrigation District would have if there was a major failure at Tri Dam.
Bairos said he wants to fund it “uphill,” meaning that OID would keep the funds in their reserves and then send the money to Tri Dam if/when needed. Director Steve Webb agreed and called OID more “hawkish” about money than SSJID. Knell noted concerns about California law and the number of entities controlling funds and said the money doesn’t belong to Tri Dam, it belongs to OID and SSJID. He added that Tri Dam is a facility owned by the districts, not its own entity.
The next regular meeting of the OID Board of Directors will be at 9 a.m. on Tuesday, Jan. 15, as the Jan.1 meeting was cancelled, in the OID boardroom, 1205 East F.
The next regular meeting for the Tri Dam Project will be at 9 a.m. on Thursday, Jan. 20, also in the OID boardroom.