Groundwater in the Bunker Hill Basin generally flows in a southwesterly direction from the San Bernardino Mountains to the San Jacinto Fault. The San Jacinto Fault acts as a barrier, or underground dam, causing the groundwater behind the fault to rise toward land surface in the form of high groundwater. In addition to the rising water associated with the groundwater barrier, this area of the basin also experiences a "pressure effect" caused by the higher water surface elevation along the foothills. This high groundwater area is located within the City of San Bernardino and is commonly referred to as the "Pressure Zone" or the "Area of Historic High Groundwater (AHHG)". In the past, water levels in the AHHG have risen high enough to cause artesian conditions (groundwater pooling above land surface). Groundwater levels which are this shallow frequently cause basements to flood, adversely affect the load-bearing capacity of streets, disrupt underground utilities and may cause "liquefaction" during an earthquake. Liquefaction occurs when saturated, sandy soil turns into a "quicksand" state during an earthquake. When liquefaction occurs, the ground no longer provides support to underground utilities or overlying structures, allowing them to sink or to float. In some cases, the foundational supports have been compromised, resulting in buildings toppling over. Liquefaction can be mitigated by removing the water from the soil or by changing the soil characteristics through grouting or other methods.
The general purpose for these facilities is to pump the high groundwater from the AHHG and deliver it throughout Valley District's service area. Once water levels within the AHHG have been lowered to between 30 and 50 feet below ground surface, Valley District will be able to artificially recharge the basin through multiple spreading basins along the foothills with native water from the Santa Ana River or imported water from the State of California Department of Water Resources State Water Project. Ultimately, Valley District is hopeful that the groundwater extraction and distribution facilities of the Master Plan will enable the San Bernardino Basin Area to be used for conjunctive use, further protecting the region from drought.
One of the pipelines in the Master Plan is the 6.5 mile, water transmission pipeline named the "Central Feeder Pipeline" which runs east/west roughly through the center of the District's service area. Once complete, the Central Feeder Pipeline will require two (2) pump stations, the "San Bernardino Pump Station" and the "Redlands Pump Station", to move water from the AHHG in the west to the eastern portion of the District service area. One of the pipelines that will ultimately attach to the Central Feeder Pipeline is the Baseline Feeder Extension South Pipeline which was recently completed using Proposition 13 funds. In the east, the Central Feeder Pipeline will ultimately connect to the Department of Water Resources East Branch Extension and provide delivery to Yucaipa and possibly to the San Gorgonio Pass Water Agency.
GOALS AND SCOPE OF PROJECT
- Reduce reliance on imported water during drought periods through better management of the groundwater basin which provides a benefit to all of southern California.
- Help alleviate the high groundwater condition by intercepting groundwater upstream of the AHHG.
- Help speed up the cleanup of the Perchlorate plume in Redlands by removing the contaminated water, treating it and delivering it through the pipeline.
- Provide a benefit to multiple agencies. Treated groundwater may be delivered to (1) local agencies, (2) the San Gorgonio Pass Water Agency via the East Branch Extension; and (3) the Metropolitan Water District of Southern California (MWDSC).
- Once the Project is ultimately connected to the Baseline Feeder Extension South Pipeline, Valley District will also be able to convey "nuisance" high groundwater directly from the AHHG to those entities listed above.
- Once the Project is ultimately connected to the Santa Ana Valley Pipeline (California Aqueduct), it will be able to deliver State Water Project Water throughout Valley District's service area.
The Project is generally located within the City of Redlands from Texas Street in the west to just beyond Opal Avenue in the east.
Phase 1 of the Central Feeder Project (Project) consists of approximately 4 miles of 78-inch diameter pipeline and a portion of the Redlands Pump Station. The pump station is provides a lift of 720 feet and is capable of delivering 50 cfs utilizing three (3) pumps. The pump station sits on top of a below-ground 510,000 gallon regulating reservoir. Initially, the pipeline will deliver an estimated 21,000 acre-feet/year of unused capacity from the City of Redlands wells which will be obtained from the City's Reservoir No. 1 located just northeast of the corner of Texas Street and San Bernardino Avenue. The pipeline runs in San Bernardino Avenue from the Redlands Pump Station in the west to just beyond the primary "customer" for this phase of the project, the Metropolitan Water District of Southern California's Inland Feeder Pipeline.
The project delivery method used for this project was "design-build". This delivery method requires competition among teams made up of an engineering firm and a contractor. Because the engineer and the contractor are on the same "team", it results in fewer construction issues as compared to traditional design-bid-build. The issue which required the most time and effort was the connection to the Metropolitan Water District of Southern California's (MWDSC) Inland Feeder Pipeline. MWDSC required a unique valve at the connection which takes approximately 1 year to fabricate. In addition to the unique valve, it also took quite a bit of time to gain approval from MWDSC to connect to the Inland Feeder pipeline.
The Project was initiated in 2006. Construction was completed in mid 2007.