LADWP runoff preparations under way in Eastern Sierra

LADWP press release

BISHOP, CA – The Los Angeles Department of Water and Power (LADWP) is working proactively to prepare for the arrival of anticipated massive runoff water resulting from this year’s near record snowpack in the Eastern Sierra Nevada Mountains. These efforts are in partnership with Inyo County, the Inyo Sheriff’s Department, Bishop Police Department, Cal-Trans, Southern California Edison and others, as a member of the Inyo County Interagency Emergency Preparation team.

Work to prepare for the anticipated high water flows began in late February. The efforts have been assisted by an Emergency Declaration from the Mayor of the City of Los Angeles to allow LADWP to take immediate steps to protect infrastructure and aid in managing flood waters while also protecting public safety. Inyo County issued a similar declaration.

To maximize the beneficial use of runoff water to the fullest extent, LADWP is spreading water throughout the aqueduct system to replenish local groundwater aquifers. Current spreading is moderate and will increase as runoff occurs in larger quantities later this spring and summer. LADWP is also maximizing flows in the LA Aqueduct by lowering reservoirs to create more storage space for runoff water and supplying the City of Los Angeles with aqueduct water in place of purchased water and groundwater wherever possible to manage excess flows. Further, LADWP crews are hard at work preparing, cleaning, and repairing water conveyance ditches, spreading basins, sand traps, and other facilities located on City of Los Angeles property, areas controlled by LADWP, and along the Los Angeles Aqueduct, in order to manage the anticipated runoff.

Water that exceeds what can be spread to recharge local aquifers and which does not make it into the LA Aqueduct system will end up on the Owens Lakebed, the natural terminus point for waters flowing down the Owens River. Once there, it will add to the existing 30 sq. miles of saline brine pools and is expected to cause significant flood damage to dust control infrastructure managed and constructed by LADWP over the past 17 years. These measures, spread over nearly 50 sq. miles of dried lake, have effectively reduced dust pollution in the area by 96 percent. Damage to these dust control areas may result in increased air pollution that could threaten the health of the public after the runoff evaporates in 12 to 18 months.

LADWP is also concerned by the potential of water overflow in and around the towns and communities of the Eastern Sierra and is actively providing assistance in preventing and controlling runoff that could impact the public. Emergency assistance will be provided on lands throughout the valley should flooding threaten the property of a partner agency or the public.

“Inyo County is no stranger to emergencies and disasters,” Inyo County Sheriff Bill Lutze said. “Our resilience comes from a strong unified command made up of local, state and federal agencies as well as a public that is proactive in emergency preparedness. We continue to be grateful for our strong working relationships with our allied agencies, including Department of Water and Power, as well as with our residents.”

In order to keep the public informed of the steps being taken to manage runoff to the greatest extent possible and minimize the impact to dust control measures, LADWP will issue regular updates of its runoff management efforts.

Emergency Runoff Management Activities undertaken by LADWP as of April 11, 2017, include:

Water Spreading

Pleasant Valley to Tinemaha Reservoir –      23,500 acre feet (AF)

Tinemaha Reservoir to Haiwee Reservoir – 7,600 AF

South of Haiwee Reservoir –                         5,200 AF

Total Spreading Water                                    36,300 AF

Maintenance and Construction Activities

Mono County

  • Crowley Lake will be lowered to 80,000 AF to make room for anticipated runoff. Current level – 107,000 AF
  • Completed Long Valley Dam and spillway inspections (Work will be ongoing)
  • Snow removal to better access Long Valley Reservoir Dam (Complete)

Currently very little work is being conducted in the Mono Basin due to heavy snow. Equipment is planned to be staged at critical structures and areas likely to see high water conditions, such as Lee Vining Intake and Rock Creek sand trap at Toms Place. This will take place once site conditions allow.

Pleasant Valley Reservoir to Tinemaha Reservoir

  • Applied for variance from Department of Water Resources Division of Safety of Dams to raise Pleasant Valley Reservoir water level (Complete)

Work to repair and upgrade existing spreading ponds and diversion structures in the Laws/Five bridges area include:

  • Reinforce and increase size of pond berms to increase spreading capacity and durability. Installing additional head walls and diversion pipes and culverts to provide greater flexibility during spreading operations (90% complete)
  • Preparing to raise portions of patrol roads adjacent to the canals to provide additional free board and greater conveyance capacity in both the Upper and Lower McNally Canals. This work will provide the ability to spread over 100 cubic feet per second (cfs) into the nearby spreading ponds or to spreading areas located further downstream (Project starting this week)
  • Preparing portions of the McNally Canals East of Hwy 6 to accept water by mowing and cleaning (Complete)

Work on canals, ditches and ponds in the Bishop area include:

  • Cleaning the George Collins and the A.O. Collins Canals and repairing/replacing diversion and spreading structures (Complete)
  • Cleaning, mowing and repairing diversion structures on the Rawson Canal (Complete)
  • Cleaning, mowing and repairing diversion structures on the Ford Rawson Canal (Complete)
  • Cleaning and mowing Bishop Creek Canal (Complete)
  • Modifying irrigation ditches off Bishop Creek to maximize spreading potential (Complete – Additional work will be needed over the summer months to remove aquatic vegetation to maintain capacity in the canal)
  • Filling Farmers Ponds, located on the West side of Hwy 6, and installing new culvert and diversion structures to convey water to the ponds located on the East side of the highway (Complete)

Round Valley area work includes:

  • Hand crews cleaning all open diversions on Horton Creek and Lower Rock Creek (Complete –  Work will be ongoing in the area with both equipment and hand crews cleaning ditches, installing culverts and diversion structures to maximize spreading potential.)

Big Pine area sand trap and diversion structure work includes:

  • Cleaning the Baker Creek sand traps, diversion structures and ponds (50% complete)
  • Cleaning and mowing the Big Pine Canal (Complete – Further work will be needed throughout the summer to maintain capacity once aquatic growth begins to restrict flows.)
  • Tinemaha Creek and Red Mountain Creek diversions cleaned and marked. (75% complete – Further work will be needed to direct flows into existing catch basins and spreading ponds located in the adjacent areas.)

Tinemaha Reservoir to Haiwee Reservoir

  • Repairing/rebuilding spreading basin infrastructure (70% complete – Able to spread in excess of 200 cubic feet per second at this time)

Work in the Black Rock Ditch area includes:

  • Rebuild/repair/replace culverts, check structures and distribution pipes (Complete)
  • Clean and/or repair distribution channels (70% complete)

Work in the Stevens Ditch area includes:

  • Mowing, cleaning and adding spreading culverts (Complete – Currently at 50% of capacity)
  • Prepare Thibaut area ditches and berms (Complete)

Work to prepare the two canals located east of the Owens River to divert imminent flow into the LORP includes:

  • Clearing McIver Ditch from East of Goose Lake to south of Mazourka Road (100% complete. Currently flowing 15 cfs during Owens River pulse flow. Evaluating additional work for maximum flows and spreading.)
  • Clearing the Eclipse/East Side Ditch from Mazourka Road to south of Owenyo area (100% complete – Currently flowing 13 cfs during Owens River pulse flow. Evaluating additional work for maximum flows and spreading.)

Los Angeles Aqueduct (LAA) work includes:

  • Cleaning the Unlined section of the LAA (75% complete – Cleaning will be needed throughout runoff season)
  • Cleaning the Lined section of the LAA to the Alabama Gates (100% complete – Cleaning will be ongoing as needed)

Equipment Staging

  • All requested heavy equipment has been rented and received based on forecast needs. Equipment is performing preparation tasks, will be staged during spreading and cleaning operations.

Work to prepare the Lower Owens River Project (LORP) intake includes:

  • Cleaning the Forebay (Complete – Will need to be cleaned throughout the year.)
  • Cleaning the measuring section (Complete)
  • Jetting the Langeman Gate area (Complete)
  • Cleaning the LORP tail bay and 100 Yards downstream (Complete)

Continually preparing the alluvial fan creek diversions west of the LORP:

  • DWP lands:                                          95% complete
  • Bureau of Land Management areas:  70% complete
  • Forest Service areas.                                     100% complete

Owens Lake

  • Armoring of berms, northwest area Owens Lake (Work not yet commenced, in purchasing for contract award)
  • Construction of new trenches northwest area of Owens Lake (5% complete)

  Lower Owens River Pump-back Station (Pump-back Station) work includes:

  • Placement of temporary barriers, gravels, sandbags and related components around the Pump-back Station to protect it from inundation (Waiting to receive approval from the respective agencies)
  • Widen the path of water within the Lower Owens River across from the Pump-back Station through creating a temporary channel allowing for greater conveyance of water. This temporary measure is intended to prevent ponding of the water in the vicinity of the Pump-back Station and decreasing the potential for water elevation rising in the vicinity of the Pump-back Station (Waiting to receive approval from the respective agencies)

Lower Owens River Temporary Flow Modification work includes:

  • Placement of temporary barriers and related components to redirect the water away from the Corridor 1 Road and the T36 DCA northern berm. This temporary measure is intended to prevent inundation and damage to the existing managed vegetation area in the T36 DCA (Waiting to receive approval from the respective agencies)
  • Modify the east bank of the Owens Lake Delta and tamp down the existing vegetation (tulles) along east side of the Owens Lake Delta to improve water conveyance capability and create a preferred pathway (Waiting to receive approval from the respective agencies)

Western High Density Polyethylene (HDPE) Pipeline work includes:

  • Temporarily securing in place about 825 feet of the irrigation supply lines from T36 dust control area (DCA) to T37 DCA. This measure is intended to prevent the existing three, 18-inch-diamater plastic pipelines from potential floatation and damage (Waiting to receive approval from the respective agencies)

Zonal Mainline work includes:

  • Placement of temporary plastic lining and related components to protect the Zonal Mainline from damage due to inundation and erosion of the slope of westerly berm road, the Brady Highway, from wave action due to high winds (Waiting to receive approval from the respective agencies)

South of Haiwee Reservoir

  • As of 4/2/17, LADWP has discharged a total of 4,600 from the Los Angeles Aqueduct at three locations: Rose Valley south of Haiwee Reservoir, Freeman Wash west of Ridgecrest, and Cameron Wash north of Mojave.
  • Working on reestablishing the Maclay Highline, which diverts LAA water to the Pacoima Spreading Grounds (20% complete)
  • Structuring the Power Plant One Slide Gate to place water into San Francisco Creek (Currently pursuing permits for this).

To request runoff preparation assistance, please contact Greg Loveland by emailinggregory.loveland@ladwp.com or calling 760–872-1104.

 

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One Response to LADWP runoff preparations under way in Eastern Sierra

  1. Bill Garnett April 13, 2017 at 5:35 pm #

    This should be good for the water tables in the Owens valley. Hopefully LADWP will take this opportunity to let Mono Lake fill as much as possible by not taking water from its tributaries this year. It would seem they are expecting too much water downstream as it is.

     

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