MEETING SEISMIC & MEETING SEISMIC & GEOTECHNICAL GEOTECHNICAL

CHALLENGES IN WEST CHALLENGES IN WEST COUNTY SCHOOLS COUNTY SCHOOLS

Presentation to West Contra Costa Unified School District

Board of EducationJanuary 7, 2009

AgendaAgenda

West County seismic & geotechnical challengesBond program renovations◦ Initial Structural/Seismic assessments◦ Geotechnical evaluationsGeotechnical Impacts◦ Globe Soils follow-up: Kropp “17 Schools Studies”◦ Riverside Elementary, Washington ElementaryPortola Middle SchoolSeismic Update◦ AB 300 List, Prop. 1D Seismic Program◦ Adams Middle SchoolRecent geotech studies◦ Pinole Valley High School

Seismic & Geotechnical ChallengesSeismic & Geotechnical Challenges

East Bay region high seismicity◦ Living along the Hayward Fault◦ Other local faults—Calveras, San Andreas

High ground motion, surface fault ruptureSeismic impacts on specific soils conditionsExample--Shaking on unconsolidated soils

Geotechnical issues◦ East Bay hills—landslides

Both “active” and historic slidesLiquefaction—unconsolidated soils◦ Tendency to “liquefy”—turn to mush when shaken

◦ Clay soils—expansive nature◦ Serpentine rock—associated with fault

Naturally occurring asbestos

Insert Hayward Fault graphic

Structural & Seismic EvaluationsStructural & Seismic Evaluations

Background investigations◦ Part of Master Architect planning process Structural & seismic evaluations of all District schools◦ Measure M Elementary Schools—Dasse Design March 2002 Report◦ Measure D Secondary Schools—Dasse Design October 2002 Report◦ Identified deficiencies◦ Ranked deficiencies and rated schools◦ Used to prioritize schools for Bond Program renovations

Geotechnical evaluationsGeotechnical evaluations

Background investigations◦ Part of Master Architect planning process Preliminary geotechnical reviews◦ Jensen van Leinden Geotechnical Engineers◦ District sites—screening level surveys◦ Guidelines for future geotechnical workMeasure M & Measure D projects◦ Globe Soils◦ Prepared Geotechnical & Geohazard reports◦ Used by structural engineers as basis of design◦ First 17 Measure M projects◦ Initial 5 Measure D projects

Geotechnical ImpactsGeotechnical Impacts

Globe Soils reports identified as deficient◦ 2004/2005—initial construction findings at variance with reports◦ Globe Soils goes out of business◦ District retains a bridging firm and testing labs engineers to complete first 17 schools

Late 2004 “qualifications-based selection process” for new geotechnical engineer◦ 44 firms solicited, 17 firms submit◦ Alan Kropp Associates ranked #1

January 2005 approved by BoardReview of Measure M projectsGeotech engineer of record, Measure D projects

Geotechnical ImpactsGeotechnical Impacts

Measure M ProjectsKropp--Full review of all Globe Soils work ◦ “17 Schools Studies” December 2005◦ Screening study of literature, maps, aerials◦ Identify and prioritize future in-depth reviewFollow-up testing recommended—Phase 1 Studies include borings, soils testing◦ 7 sites high priority: Ellerhorst, Madera, Mira Vista, Riverside, Sheldon, Verde, Washington◦ 5 sites lower priority: Bayview, Harding, Kensington, Lincoln, Peres◦ Landslide potential, liquefaction evaluation, fault evaluation investigations

Geotechnical ImpactsGeotechnical Impacts

Measure M Projects“Phase 1 Studies” completed 2006-2008Kropp’s “Phase 1 Studies” indicate additional testing required at 3 sites◦ Ellerhorst, Riverside, Washington“Phase 2 Studies” completed 2007◦ Additional borings and analysis at each site ◦ Ellerhorst—liquefaction potential “minor”◦ No further testing required◦ As with other “cleared” sites work performed under Measure M—foundations, structures, etc. found to be ok

Riverside ElementaryRiverside Elementary

Kropp completes two rounds testing◦ Reports issued identify geohazard potential at site◦ Earthquake-induced soil liquefaction and instability

of creek bank are serious concerns◦ Phase 1 Report 2006, Phase 2 Report 2007District commissions Peer Review◦ “Engeo” selected from qualified list of firms◦ Reviews Kropp findings, confirms concerns◦ Interaction between firms suggesting additional

testing and analysisDistrict retains structural engineer to review building impacts◦ Issa Structural Engineers◦ Liquefaction settlement—ability of building

foundations to resist identified potential settlement

Riverside ElementaryRiverside Elementary

Kropp completes Phase 2a Report 2008◦ 2 additional borings on site, further analysis◦ Focus on seismic slope stability & deformations

“Site susceptible to seismically-induced landsliding (at creek bank) due to weak clayey soils that underlie the site at depth.”“The deformation analyses we performed calculate that landslide movements of about a foot or more may occur as a result of earthquake ground shaking.”“We believe it is possible that one or more down-dropped blocks with about a foot or more of vertical offset could occur beneath school buildings.”

◦ Kropp’s report indicates not feasible to mitigate seismic slope stability issues at the site

Riverside Elementary Riverside Elementary

Engeo completes 2nd Peer Review ◦ Assesses Kropp Ph 2a Report◦ Do not concur with most pessimistic conclusions in Kropp report◦ Considers that the analysis used is too simplified to reach conclusions regarding extent of soil movement◦ Recommends a more comprehensive, dynamic analysis—additional testing & study◦ “The conclusions essentially condemn the portions

of the property adjacent to the creek bank by ruling out the possibility that more comprehensive analysis may lead to different conclusions and by suggesting that future mitigation is not possible.”

Washington ElementaryWashington Elementary

Screening level study◦ High liquefaction potential◦ Portions of the site are bay fill◦ Very high ground water◦ Loose, unconsolidated soilsKropp completes Phase 2 study◦ Site borings with additional analysis◦ High potential identified for earthquake-induced liquefaction ◦ Causing settlement, and differential settlement across buildings

Next steps—peer review, structural analysis of settlement impacts on buildings

Geotechnical ImpactsGeotechnical Impacts

Measure D Projects Geotechnical◦ El Cerrito HS

Upper corner of site is base of “Blakemont Slide”Buildings moved to create 50’ setback

◦ Pinole Middle New ConstructionUndocumented fill of former valley at siteConstruction included full removal, recompactionto current standardsGym building moved to current location to avoid deepest old fill areas

◦ Downer ElementaryLiquefiable layersSite “Ground Improvement” projectStone columns—740—50’ deep, 3’ diameter columns of gravel injected below site

Portola Middle School Portola Middle School

Kropp completes geohazard report 2005◦ Large-diameter borings, trenching◦ Earthquake-induced landslide hazardPeer review—Cal Engineering & Geology◦ 2005 report concurs with basic findings, challenges

some slope movement assumptionsStructural engineering analysis◦ Kam Yan Engineers reviews potential site mitigationReview by California Geologic Survey (“CGS”)◦ State agency with responsibility for all schools

geotechnical issues◦ CGS concurs with findings regarding geohazard◦ Division of State Architect (“DSA”)

“Safety of students is at risk and must be corrected.”

Seismic UpdateSeismic Update

AB 300 List◦ 2002 “Seismic Safety Inventory of California Public Schools◦ First statewide inventory of seismically-vulnerable school buildings◦ Screening-level review of building drawings

Any buildings built before 1978Wood frame buildings not consideredIdentified, prioritized structural systems of concern

◦ Report was “confidential” only provided to Districts upon request◦ WCCUSD has 14 sites on AB 300 list

Seismic UpdateSeismic Update

Adams MiddleDowner ElementaryEl Cerrito High Granada High (now Kennedy)Crespi MiddlePinole Valley HighRichmond High

Del MarMira VistaPullman (now King)EllerhorstMontalvinRoosevelt Jr. High (now Gompers)Vista Hills

West Contra Costa Unified AB 300 List Schools

Seismic UpdateSeismic Update

Proposition 1D Seismic Program◦ 2006 statewide bond measure for school construction ◦ First funds identified for seismic mitigation of “most vulnerable school buildings”◦ 10% of new construction funding in bond measure set aside for program--$199.9 mil◦ Regulations implementing program set very stringent thresholds

Only sites with over 1.7g ground motionCategory 2 Structural types

◦ After adoption of regulations—no applications received by state

Outreach begins by DSA and OPSC

Seismic UpdateSeismic Update

Proposition 1D Seismic ProgramOct. 28, 2008: DSA notifies WCCUSD that 6 sites meet ground motion threshold for program

Adams Middle School 1.713gEl Cerrito High School 1.7gHarding Elementary 1.7gKensington Elementary 1.737gMadera Elementary 1.711gVista High (Alternative) 1.717g

District has completed structural work on 4 of these sites

Reconstruction, to current codes—ECHSVoluntary seismic upgrades—Harding, Kensington, Madera

Adams Middle SchoolAdams Middle School

Adams identified with seismic poor performing buildings in original Dasse Report◦ Not included in original Measure D projects◦ No upgrades to buildingsStaff had identified Adams on AB 300 list◦ Review site ground motion using DSA methods◦ Initiated structural analysis for potential inclusion in Prop. 1D Seismic Program application

Adams Middle SchoolAdams Middle School

Dasse Design, Structural Engineers retained by District◦ Report: “Adams Middle School Academic Building Seismic Vulnerability Assessment.”

December 2008◦ Used procedures of ASCE-31-03, “Seismic Evaluation of Existing Buildings.”◦ More in-depth than original screening level studies from 2002◦ Only the main building included in first study

Mixed concrete, wood, some steel construction

Adams Middle SchoolAdams Middle School

Dasse 2008 Report findings:◦ Major deficiencies identified

Lack of collector and drag connections for shear transfer of diaphragm forces to shear wallsWeak out-of-plane conrete wall anchoragesDiscontinuous wood and concrete shear wallsWeak plywood diaphragms Lack of adequate wood shear wall capacities

◦ “In Dasse’s opinion, the structure could experience significant and likely irreparable damage in a moderate earthquake.”◦ “In a severe earthquake, with intense ground

motion at the site, it is conceivable that these deficiencies will pose significant life safety hazards and localized collapse in several locations of the building is possible.”

Recent Geotechnical StudiesRecent Geotechnical Studies

Measure J Projects new round of studies◦ District RFQ process 2006 for Geotechnical Engineers◦ “Kleinfelder” selected as Geotech of Record for Measure J projects◦ Prepared preliminary geotechnical reviews and geohazard assessments for project sites◦ Most sites cleared and ready for construction◦ Kleinfelder prepared final reports, using 2007 code updated procedures◦ CGS has approved all current design sites—with one exception…

Pinole Valley High SchoolPinole Valley High School

Initial Master Plan for the site ◦ Proposed a new building to remove over 20 portables on the crowded site◦ New building located at current 400 wing◦ Adjacent to rear hillsideKleinfelder’s initial Geohazard Report indicated concerns◦ City of Pinole Earthquake Special Study Zone

CGS required Fault Rupture Study◦ Potential landslide at rear of siteDistrict initiated in-depth studies at site◦ Fault rupture study—trenching across site◦ Slope stability study

Pinole Valley High SchoolPinole Valley High School

Kleinfelder study results◦ Fault rupture study finds no evidence of recent fault movement at site

CGS visits site trench and concurs◦ Slope Stability Study, December 2008

Finds evidence that the site is underlain by historic landslide debrisSlope stability— ”…marginally stable under static conditions and potentially unstable during an earthquake.”“…the slope could move on the order of 5 to 20 feet during an earthquake…Damage to existing structures would most likely be due to uplift of the ground surface. Our initial analyses suggest that existing buildings within 20 feet of the slope could be damaged due to slope movement.”

Pinole Valley High SchoolPinole Valley High School

Kleinfelder study follow up◦ Short-term recommendations in report

No grading/regrading of the slopeEnsure that groundwater levels are pumped out to reduce water pressure on the slopeClear existing surface water drainage facilities

◦ Longer-term follow up studiesSurface water management enhanced on hillsideSupplemental investigations including large-diameter borings◦ Establish more clearly extent of the landslide

◦ In lieu of additional studies“One option to consider includes replacing existing structures that are located within about 20 feet of the slope with new structures in the central and northern portions of the campus.”

SummarySummary

Substantial progress by District to date◦ Made possible through local bond measures approved by voters◦ Voluntary seismic upgrades at 17 Measure M Elementary schools◦ New construction at Downer with Ground Improvement◦ Replacement of El Cerrito High ◦ New construction at Pinole Middle◦ Replacement of Helms & DeAnza (underway)◦ Beginning removal of students from Gompers◦ Portola Middle School relocation process underway

SummarySummary

Significant challenges remain for District◦ Including assessments of student safety issues, considerations of temporary relocation◦ Washington—further testing liquefaction-related differential settlement◦ Riverside—liquefaction, landslide potential along the creek bank

Further testing and confirmation of extent ◦ Adams—structural system deficiencies

Site is suitable, buildings a concernPreparing application for State Seismic ProgramPeer review structural next step

◦ Pinole Valley High—slope stability at rear hillsFurther testing to characterize slide hazard