Field studies have been conducted throughout the Delta region to support the preparation of a thorough and accurate EIR/EIS for the BDCP. To date, these studies have gathered environmental and engineering data where potential habitat conservation and water conveyance options may take place.
Some properties located within the planning area have been selected for further study in order to improve the accuracy of the evaluation. In these cases, DWR representatives have sought access to properties through the use of a Temporary Entry Permit (TEP). TEPs grant field crews temporary access to private property so that studies may be conducted. If a particular parcel is chosen for further study, one or more of the following activities may be conducted: ground and aerial surveys, and geotechnical, biological, geological, archaeological, floral and faunal studies.
DWR has prepared an Addendum and filed an NOD to the 2010 IS/MND for Geotechnical Exploration Activities. DWR has been unable to obtain access to many properties in the study area in order to complete the activities within the timeframe established under the 2010 IS/MND. Therefore it is necessary to extend the December 31, 2012 completion date. In addition, locations along SR 160 are being highlighted in this Addendum because temporary lane closures will be necessary.
Soil Boring Data Available
In an effort to address questions about the tunnel material and how it might be reused, DWR is publishing data collected from soil borings. DWR has sampled soils at depths from 120 to 170 feet throughout the Delta; however, access to private property is generally granted only with assurances that results will remain private, except as required by law. The results shown are from soil borings taken from waterways and public lands.
Results of a nearby San Francisco Public Utilities Commission tunnel project beneath the San Francisco Bay suggest that as much as 98 percent of the excavated material will be reusable.
shows where the soil borings were performed and the graphic soil boring log explains the soil types found. As shown in the graphic soil boring log
, the tunnel boring machine is expected to encounter mixed face conditions (mixed materials). The log shows that reusable tunnel material will consist mainly of silty sands, sands, and clays. The material excavated during construction has been identified for many possible reuses, including habitat restoration projects and engineered backfill. Engineered backfill can be used for levee improvements, subsidence remediation, and roadway construction.
The tunnel boring machine requires mixing water and biodegradable, eco-friendly soil conditioners with the soil to reduce resistance at the tunnel face and more easily transport the material. While tunnel material has been successfully reused for various purposes around the world, DWR is currently performing tests to ensure the feasibility and safety of reusing this material.
For more information about current geotechnical and environmental field studies, contact BDCP staff at info@BayDeltaConservationPlan.com or 1-866-924-9955.