Geotechnical Exploration for Reach 2B of the San Joaquin River Restoration Program

Nicholas HightowerDivision of Engineering, Project Geology2011 DWR Geology and Groundwater Meeting

BackgroundThe San Joaquin River Restoration Program

is the result of a Settlement which has two goals:◦ Restoration Goal: To restore and maintain river

flows to help reproduce and sustain populations of salmon and other fish

◦ Water Management Goal: To reduce and avoid adverse water supply impacts on water contractors due to interim and restoration flows.

The US Bureau of Reclamation is the lead federal agency, while DWR is the lead state agency for the program. South Central Region Office is the lead for DWR.

SJRRP DESCRIPTIONLOCATION

◦ 150 miles of the San Joaquin River from Friant Dam (Millerton Lake) to the confluence with the Merced River

◦ Also includes 13 miles of the Eastside and Mariposa Bypasses

COMPONENTS

◦ 350 miles of existing and new levees

◦ 8 control structures◦ 8 river crossing

structures◦ Seepage

monitoring ◦ Borrow areas

Reach 2B Geotechnical Investigation

DWR and the Bureau of Reclamation is responsible for gathering geotechnical data to support the alternative channel alignment designs◦ USBR: Focused efforts on groundwater

seepage◦ DWR: Geologic exploration and analysis to

support engineering design of proposed modifications to increase the San Joaquin River channel carrying capacity, along with accompanying structures.

Reach 2B ExplorationReach 2B is about 35

miles west of Fresno

South Central Region OfficeSecured TEPs and

notified landowners with Right-of-Way’s assistance

Coordinated and performed Environmental and Cultural Clearances

Created and provided essential GIS mapping

Marked/Staked hole locations prior to clearances

Requested underground utility clearances from USA

SCRO Field Staff helped log holes and coordinate the field effort

2010 Geotechnical Exploration

Completed in three separate phases:◦ March◦ June◦ November-December

21 Borings range in depth from 50 to 64 feet

72 CPTs range in depth from 60 to 90 feet.

2010 Geotechnical Exploration (Continued)

Drilling◦ 20 borings drilling using

mud rotary methods because of heaving sands

◦ 1 boring drilled using hollow-stem auger method

◦ Standard Penetration Tests conducted every five feet with sample bagged

◦ Two thin-walled Shelby tube samples typically collected from each boring for potential shear strength, permeability, compaction, and other geotechnical tests

Cone Penetration Testing◦ 72 soundings◦ Continuously measured

tip resistance, sleeve friction, and dynamic pore pressure

◦ Pore pressure dissipation tests conducted at selected depths in each sounding to determine depth to groundwater

◦ Used as primary exploration, with lithology confirmed at selected locations with paired drill holes

2010 Geotechnical Exploration

2010 Geotechnical Exploration

Borings and CPTs were placed at locations where specific design and foundation information was needed

Post-Field Work—Office TimeFirst Step: Review Field Drilling LogsEntered logs into gINT, a borehole database

program gINT has multiple functions:

◦ Creates official logs◦ Stores soils data in database◦ Allows data export to Microsoft Excel

Field Log Draft Report Log

Creating Cross-Sections in ArcGISExport borehole data from gINT into

Excel format for ArcGIS, along with CPT logs

Draw desired cross-section lines in map view

CrossView

CrossView and ArcGIS

FINDINGSThe CPT logs

correlated well on the majority of the borings.

Soil lab tests are still in the process of being tested.

The general soil stratigraphy can be summarized as:◦ 0-5’ Silty Sand

and Silt◦ 5-20’ Sandy Clay,

Clay and Silt◦ 20-60’ Silty Sand

and Poorly Graded Sand

CONCLUSIONSFirst phase of exploration for Reach 2B

resulted in sufficient geotechnical data to begin preliminary design.

Additional exploration will be necessary to go forward with more detailed design, and to explore conditions for specific structures and borrow areas.

The use of gINT for boring logs makes drill hole data more useable and manageable.

The use of ArcGIS and CrossView makes compilation of geologic cross sections efficient and easy for data analysis and presentation.

Thanks!