CALIFORNIA STATE EDITION
A Supplement to:
May 10 2020 Vol. I • No. 10
“The Nation’s Best Read Construction Newspaper… Founded in 1957.” Your California Connection – Debbie Hansen – 1-702-239-0348 – dhansen@cegltd.com
Wirtgen Cold Milling Machines Key At Oroville Dam By Tom Kuennen
California Department of Water Resources photo
SPECIAL TO CEG
In a grueling mountain application — while aimed downward at a 30-degree angle and steadied by cables from the top — two Wirtgen cold milling machines removed a temporary, emergency-placed concrete surface of the lower part of the great spillway of the Oroville Dam and reservoir in advance of permanent resurfacing. In the hills north of Sacramento, at 770 ft. (235 m) high, the Lake Oroville dam is the tallest dam in the United States, and provides water supply, hydroelectricity generation and flood control. The dam impounds Lake Oroville, the second largest man-made lake in the state of Calif., capable of storing more than 3.5 million acre ft. (1.1 trillion gallons, or 4.3 trillion liters) of rain and snowmelt water. The main spillway is just under 180 ft. wide, as wide as a 12-lane freeway with center divider. With a total length of 3,055 ft., it can handle 270,000 cu. ft. per second if necessary. The 2016-2017 season was the wettest winter ever in northern Calif., and the record-setting precipitation brought a massive amount of runoff to the region. At that time, Lake Oroville received an entire year’s average runoff, 4.4 million-acre ft., in about 50 days. Beginning in January 2017, record inflows forced the project owner — the California Department of Water Resources (DWR) — to release excess water down the spillway. More than five million-acre ft. of water from Lake Oroville was released from February through May 2017, more than twice the amount that had ever been released from the main spillway. But due to the unprecedented volume of water going down the spillway and water pressure from beneath, the main spillway was eroded and damaged to the point where reconstruction was required. In a race to complete the project in time for the winter of 2018-2019, the $1.1 billion Lake Oroville Spillways Emergency Recovery Project was completed Nov. 1, 2018, and Wirtgen products and its
On steep spillway slope, with forward speed of 9 ft. per minute, a Wirtgen W 2100 cold milling machine prepares surface for reinforced concrete slab; millings placed in 7 cu. yd. haul vehicles, usually used in difficult open-cast mine applications.
customer, Anrak Corporation, Sacramento played an important role as milling subcontractor to the prime, Kiewit Infrastructure West. Milling Through RCC First, to restore functionality to the spillway in case it was needed, roller compacted concrete (RCC) was placed where needed to fill eroded gaps, blow-outs and across the
surface of the spillway. But this temporary material had to be removed in advance of a permanent fix. “Anrak was milling roller-compacted concrete that had been placed temporarily during the emergency phase of the project,” said Tom Chastain, applications specialist for Wirtgen America Inc. “Ultimately, the finished concrete surface would be placed on that area.” see OROVILLE page 8
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