Nov. 5, 2010
With 9/11 almost nine years in the past and with a new manager at the helm of the El Dorado Irrigation District the Akin Powerhouse was opened for its first public tour Thursday. The guests were Rotary Club members from Placerville and Pollock Pines.
All were impressed with the facility, first licensed in 1922 and generating power in 1924. The two Pelton water wheels and two horizontal generators remain essentially the same as what was designed and built by Western States Power Co. and sold to PG&E in 1928.
One of the Pelton water wheels was replaced in 1956. Pelton water wheels are basically buckets on a wheel refined by 19th century inventor Lester Allan Pelton. Pelton, observing a waterwheel built by Samuel S. Knight at Knight’s foundry in Sutter Creek, Amador County, misaligned the high pressure water nozzle and noticed that it spun faster than when the water jet hit in the middle of the bucket.
Pelton, after testing, manufactured his first Pelton wheel at the Miners Foundry in Nevada City in Nevada County. The Pelton water wheel used dual buckets and a splitter on the hydraulic spray nozzle. It achieved 90 percent efficiency, whereas the industry-leading Knight wheel achieved only 40 percent efficiency. The Pelton water wheel was the first used to generate electricity in 1878.
The Pelton wheel and its high efficiency is especially suited for high pressure water that comes out of a penstock like EID’s.
The water comes from four alpine reservoirs and is collected by a diversion dam near Kyburz that shunts the water into the El Dorado Canal — 22.5 miles of canal, flumes and tunnels that brings 160-165 cubic feet per second of water to the 400 acre-foot Forebay Reservoir in Pollock Pines. One cfs of water will produce 1.98 acre-feet of water per day. Forebay supplies water to the district via a three-mile-long canal to Water Treatment Plant No. 1.
Also tapping into Forebay is the El Dorado Powerhouse. It begins with 11,750 feet of very large diameter steel pipe and ends in a surge tank that rises 245 feet in the air to absorb excess penstock energy. From the surge tank the water travels through 3,443 feet of increasingly thicker pipe that starts out at 54 inches and narrows to 30 inches, at which point it splits into two pipes 572 feet above the powerhouse. By the time it gets to the powerhouse the water has a pressure of 840 psi.
EID restored the 21-megawatt powerhouse in June 1996 and began generating power 20 percent higher than the historical average. By the end of that year EID had made $1 million off power sales. It did that by arrangement with PG&E, which was slated to sell the project to EID.
Then Jan. 1, 1997, brought a flood that was rated near a 200-year event. EID Power Supervisor Robert Pretzer estimated the South Fork of the American River was flowing at 70,000 cfs. That compared to the 1955 flood, which saw the South Fork flowing at an estimated 24,000 cfs. By comparison, the river at the time of Aug. 19 tour was flowing at 160 cfs, somewhat more than normal for this time of year. Dry year flows are 40-50 cfs, according to Hydro Manager Dan Downey.
The 1997 flood overtopped the exterior concrete barrier that had been put in on the upstream side of the powerhouse after the 1955 flood. The water then came in the raised air intakes and the windows. It was so high that it floated out the timber flood barrier on the west side of the powerhouse. Pretzer said at the time he had a PG&E gate key and he and the other man in the powerhouse exited uphill.
Two years later EID finally concluded a deal with PG&E and won approval from the California Public Utilities Commission for the transfer. Then it spent $2.5 million to rebuild the powerhouse. The air intakes were raised again and the lower windows replaced with concrete. Entrance to the powerhouse is through a water-tight hatch. The steel roll-up bay door has a steel slot in front where steel beams are dropped in by crane in the winter to seal it against possible inundation. The powerhouse, as well as all the alpine reservoir spillways, are operated remotely. After-hours operators on duty monitor them from laptop computers.
Along the canal there are 10 emergency spillways and 25 alarms, according to Downey. All are remotely monitored. Releases from the four alpine lakes are carefully calibrated by a hydrographer who must meet fish flows, agreed-upon lake levels and still provide drinking water and hydro power.
EID has concluded a contract with PG&E that is more lucrative than the previous power broker contract it had. It is more lucrative because hydro power projects under 30 megawatts qualify as “green energy” projects for which PG&E pays a premium because it is required by the state to obtain 20 percent of its energy from renewable energy sources — so-called “green” energy.
EID General Manager Jim Abercrombie said he can’t reveal how much EID has made from power sales to PG&E this year until the PUC approves the contract, probably in October. Suffice to say, with the heavy snowpack, late spring storms, a cool spring and cool early summer, everyone involved with EID’s hydro program has a smile on his or her face. They all report that it has been a very good hydro year.
For Abercrombie being in charge of Project 184 — the lakes, canal and powerhouse — is like deja vu all over again. He oversaw Project 184 in the 1980s and 1990s when he was El Dorado District manager for PG&E. When EID was negotiating with PG&E to buy the project Abercrombie was at the forefront of PG&E’s tough negotiations.
As EID manager, Abercrombie is promoting public tours of district facilities that belong to the ratepayers. The Rotarians said they were impressed and appreciative of the knowledge gained from actually seeing the facilities and hearing summaries from their operators.
The El Dorado Wastewater Treatment Plant was the subject of a tour by local legislators and a tour of that plant for the general public is planned. All of EID’s facilities are amazingly sophisticated and use the latest technology. Even the 86-year-old power plant depends on computers to fine tune its output.