Caliornia Geology Magazine Nov-Dec 1992

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DMG REGIONAL GEOLOGIC MAP RELEASE .DIVISION OF MINES AND GEOLOGY'S ENVIRONMENTALPROTECTION PROGRAM ..GEOLOGIC CONDITIONS AT THREE RANCHO PALOSVERDES SUBDIVISIONS .......GEOLOGIC HAZARDS AT THE NEW BAY FARM ISLANDELEMENTARY SCHOOL . .IMPLEMENTING AN AWARD WINNING RECLAMATION PLAN ATCASTLE MOUNTAIN MINE... . .SEDIMENTATION IN A HIGHLY EROSIVE WATERSHED.TEACHER FEATURE .PUBLICATIONS REOUEST FORM .DMG SPECIAL PUBLICATION RELEASE .CALIFORNIA GEOLOGY SUBSCRIPTION AND CHANGE OFADDRESS FORM ...INDEX TO VOLUME 45 - \992DMG OPEN-FILE REPORT RELEASE.

In ThisCALIFORNIAGEOLOGY

Depart"""'t 01 Consl'INat"'" EDWARD G. HEIDIGDIf8Ctor

The R8SO'Jfces AQ&nc:y DOUGLAS P. WHEELERSecrerary for Resources

Stare 01 Calot""",, PETE WILSONGovernor

Oivislor1 01 M,,_ & Geology JAMES F. DAVISSlate Geologisr

A PUBLICATION OF THEDEPARTMENT OF CONSERVATIONDIVISION OF MINES AND GEOLOGY

CALIFORNIA GEOLOGYTens $8.00/1 y' (6 iSSueS); $1 S.50J2 yrs. (12 ,"ues):$23.0013 yrs.lI8,ssues).SendSUbSCr'ptoonOtderSandchange01 addfessinlormation to CALIFORNIAGEOLOOY. P 0 Bo.2980. Sacramento, CA 9!;812-2980

NOVEMBERIOECEMBER 1992VOlume 45/Number 6CGEOA 45 (6) 165-196 (1992)

Cover Photo: Nursery for maintaining salvaged plantsfor reclamation of mined land. Photo courtesy of ViceroyResource Corporation.

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Photo 2. Exploratory excavations tor lett abutment of Auburn Dam as originally proposed In1979. then abandoned. The dam site was within the Foothills fault system and faults within2 miles (3 km) of the project were determined to be capable of a M6.5 earthquake. DMG andthe Department ot Water Resource's Division ot Dam Safety participated in the 1979 seismiCevaluation of the anginal dam site. DMG recently commented on seismic and mineralresource issues contained In the Final Environmental Impact Statement for the AmericanRiver Watershed Investiga\lon. The new project proposes to build the flood control detentIOndam 500 yards downstream trom the previously proposed location to avoid potentiai faultproblems and to accommodate the Slate's design criteria ot 9 Inches (23 cm) of potenllal taultdisplacement at the site. Photo by Trinda L. Bedrossian,

a pennit agency first prepares a brief Envi-ronmental Assessment (E.A.) of the proposed action. If the EA indicates therewill be a significant environmental effect.NEPA requires federal agencies to declarein an Environmental Impact Statement(85) the potential significant adverse environmental impacts of their actions. Theagency must also prepare a final E1S thatresponds to public comments on the draftElS and documents the decision-makingprocess, Examples of projects revi\.Vdby ERP staff where an 8S was preparedin conjunction with an 8R include theAuburn Dam/American River WatershedProject (Photo 2) and the Mojave DesertConservation Area,CECA Review

The majority of plans reviewed by ERPare CEQA documents. Approximately95 percent of the reviews deal with publicsafety issues related to seismic hazards.CEQA was enacted in 1970. primarilyto ensure that public agency decisionmakers consider and document the environmental implications of their actions(Remy and others. 1990). The purpose ofthis legislation is to establish a process thatI) informs the public of the potential environmental impacts of a proposed project:2) examines alternative projects that mayhave fewer impacts; and 3) identifies methods to reduce the environmental impactsof the project selected. CEQA differs fromNEPA by requiring public agencies toseek and implement feasible means ofreducing or avoiding the potential significant adverse impacts of proposed projects,rather than merely considering them. If theInitial Studies (IS) indicate the proposedproject may cause a Significant adverseeffect or impact on the environment. thepublic agency must prepare an E1R.

During a public comment period.CEQA documents are sent to the StateClearinghouse within theWvemor'sOffice of Planning and Research. Fromthere. they are distributed to the variousState agencies for review. DMG receivesdocwnents that pertain to geologic, seismic, and mineral resources issues throughthe Resources Agency and the Department of Conservation's Office of Governmental and Environmental Relations. ERPstaff comment on geologic and seismichazards. potential damage from faultmovement and earthquake shaking. liquefaction. landslides. settlement. unstable cutand fill slopes, expansive soils, erosion,

land subsidence. and related land-use planning and mineral resource issues (seeMcMillan. this issue).

ERP staff also provide technical assistance to cities and counties that are leadagencies under CEQA/NEPA, to otherState agencies revievJing the same documents for their concerns and perspectives.and to consultants and lead agencies whoprepare documents, or who must respondto DMG comments. ERP's role is to provide advice so that site-specific commentsin environmental documents contain geologic data that are accurate. complete. andapply directly to assessing the potentialimpacts of land-use modifications. Thepurpose of ERP reviews is to improvepublic safety by ensuring that geologic andseismic hazards have been identified andavoided or mitigated, and that appropriatedesign requirements have been considered.Safety Elements

In addition to reviewing documentstmder CEQA/NEPA. ERP staff review andcompile geologic/seismic infonnalionrelated to General Plan Safety Elements.California law requires lhat each city andcounty prepare and adopt a comprehen-

sive. long-tenn General Plan that describescommmunity development goals andprovides concrete direction for decisionmaking relative to the distribution of futureland use (Baker and others, 1987). Follovring devastating wildland fires in 1970and the San Fernando earthquake of1971. legislation was passed that requireda community's General Plan to containa Safety Element to address wildlandand urban fires and a Seismic Safety Ele-ment to address earthquake shaking andother geologic hazards. In 1984, underAS 2038, Seismic Safety Element requirements were consolidated with those 01the Safety Element. Because many SafetyElements failed to provide complete documentation of source infonnation and failedto recognize all types. magnitudes, andpotential impacts of hazards (Mintier andStromberg. 1983: Smith. 1985), AS 890was enacted in 1989. It requires eachcity and county to consult DMG prior toreviewing its General Plan and prior topreparing or revising its Safety Elementfor the purpose of including the most current infonnation on geologic and seismichazards in the revised plans. The legislalion also requires the agency to submit adraft Safety Element to DMG for reviewprior to adoption.

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site. and the liquefaction and settlementpotential of earth materials underlyingthe foundation.School Site Review

HSSRP staff review engineering geo-logic reports for proposed school sites sub-mitted to OSA under provisions of the PleldAct. as specified in the Education Code.and administrative regtllations of OSA con-tained in Tille 24 of the California Code 01Regulations (see McCrink, thiS issue). TheRekl Act was first enacted as an emergencymeasure in April 1933. folloo.ving the 1933Long Beach earthquake in which 70 schoolbuildings were destroyed. 120 sufferedmajor damage. and 300 had minor damage(Meehan. 1982).Photo 3. Recentlyconstructed twostory building at Olive View Hospltal in Sylmar, LosAngeles County, where the second ltoor dropped to ground level during the 1971 SanFernando earthquake. Photo courtesy of the Los AngeleS Times.

HOSPITAL AND SCHOOL SITEREVIEW PROJECTThe Hospital and School Site ReviewPro}ect (HSSRP) ensures that geologic.seismic. and geotechnical data in applications lor hospital. school. and essentialservices structures submitted to the Officeof Statewide Health Planning and Devel

opment (OSHPD) and the Departmentof General Services. Office of the StateArchitect (OSA) are accurate. complete.and reflect state-of-practice knouiIedge. sothat these sensitive structures are properlysited and designed. DMG staff also providerecommendations to OSHPD and OSAregarding State Buikling Code revisions.Hospital Site ReviewThe Hospital Facilities Seismic SafetyAct. Health and Safety Code. was firstenacted in 1973 following the 1971San Femardo earthquake. The earth

quake caused damage to at least threehospital buiklings resulting in 47 of the 65deaths (Photo 3) (Greensfelder. 1971).Under the Hospital Act. new hospitalstructures must remain functional duringand after an earthquake. The governingboard of each hospital must submit build-ing plan specifications and structuraldesign computations to OSHPD. including an assessment of the nalure of the sitealx.! potential for earthquake damage.OSHPD contractswith DMG for the

review of engineering geologic data anddetermination of the adequacy of the siteevaluation reports submitted.HSSRP staff review engineering ge0-logic data submitted to OSHPD accordingto requirements of Title 24 of the California Code of Regulations. California Build-ing Code (CSC). and associated adminis'

trative regulations of OSHPD. The CBCis revised every 3 years. based on changesin the previous year's version of theUniform Building Code and State amendments. Under the CBC. structures mustbe designed and constructed to resist theeffects of seismic ground motions takingimo account proximity to active faults.the site geology and soil characteristics.function of the structure (Le.. hospital.emergency vehicle shelter). and buildingconfiguralion (regular or irregular). Engi-neering geologic reports dentify the ge0-logic and seismic conditions tnat ma yrequire pro;ect mitigation. and provide anassessment of the nature of the site andpotential earthquake damage based oninvestigations or the regional and site geol-ogy. foundatbn conditions. and the potential seismic shaking at the site. HSSRPreviews the reports to ensure that adequategeologic investigations have been performed and that knOVJll active and potentiaDy active faults have been evaluatedHSSRP also reviews the reports for consid-eration of slope stability at or near the

The FJekl Act applies to elementaryand secondary public schools and commu'nity colleges; it does not apply to privateschools, slate colleges, or universities. TheAct requires OSA to approve aD plans andspecif)cations for every new school beforethey are adopted by the school OOard. andto inspect all public school construction. 1/the prospective school site is located withineither 1) the boundaries of an Alquist PrioloSpecial Studies Zone (Hart. 1990); or2) an area designated as geologically haz-ardous in the Safety Element of the localGeneral Plan for the site. a geologic studyand a soils analysis must be corKlueted toassess the nature of the site and potentialfor earthquake or other geologic hazarddamage. OSA may also request geologicstudies and soil analyses on school siteslocated outside these study zones if thereis evidence that such studies are warranted(Department of Education. 1989).

Since 1933. the performance of F"leklAct schools has been excellent. "There wasless than one percent property loss to pub-lic school buildings during the M7.7 KernCounty earthquake of 1952 (Calvert andAskin. 1971) and no Field Act schoolssustained sulfident damage to requirepermanent closing after the 1971 M6.6San Fernando earthquake (Tobin. 1992).The Lorna Prieta School. near the epicenter of the 1989M7.1 earthquake sustainedonly minor damage. while schools in thevicinity of the 1992 LanderslBig Bearearthquakes suffered no structural damage.despite being sub;ected 10 unusually highground motions \\lith long duration andsevere seismic forces (OSA. 1992).

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Essential Services BuildingsAn essential services buikling is a

building used or designed as a lire station,police station. emergency operationscenter. California Highway Patrol office.sheriff's office. or emergency communications dispatch center. According to theEssential Services Buildings Seismic SafetyAct of 1986 and administrative regulationsof OSA contained in Title 24 of the California Code of Regulations. all plans andspecifications for new essential servicesbuildings, or any existing building con-verted to essential services use. must besubmitted t o OSA for review and approval.HSSRP staff review geologic reports foressential services buildings submittedto OSA. Essential services buildings, asdesigned and constructed. must be capableof providing essential services t o t he publicafter a disaster. Site data for all new essential selVices buildings. and existing buildings converted to essential services. mustinclude a soil investigation report and ageologic and earthquake hazard report.including an evaluation 01 both known andpotentially active local and regional faultsystems. slope stability. liquelaction poten-tial. and other hazards.

MINED-LAND RECLAMATIONPROJECT

The Mined-Land Reclamation Project(MLRP) provides technical assistance in thereview of mined-land reclamation planssubmitted to local agencies in compliancewith the Surface Mining and ReclamationAct (SMARA). Because reclamation isconsidered a project under CEQA. sepa-rate CEQA documents are sometimesrequired by local agencies in conjunctionwith individual reclamation plans. DMGroutinely comments on proposed projectsaffecting mine reclamation and providesexpertise in revegetation. hydrology. ero-sion control. slope stability. and miningengineering. MLRP staff also participate inVJOrkshops. prepare articles and publications (Collins and Dunne, 1990; Evoy andHolland. 1989; Newton and Laidel, 1992;Van Kekerix and Kay, 1986). assist theState Mining and Geology Board (SMGB)and other agencies on issues involvingmined-land reclamation. and representCalifornia on the Western Governors'Association Mine Waste Task Force.SMARA ReviewSMARA was enacted in 1975 to pro

vide a means of locating and inventorying

potential mineral resources throughout theSta te and to provide for mine reclamationdUring local land-use planning. SMARAslocus is to: 1) prevent or minimize adverseenvironmental effects and reclaim minedlands to a usable condition which is readily adaptable for altemative land uses;2) encourage production and conselVation01 minerals while giving consideration tovalues relating to recreation. watershed,wildlife. range and lorage. and aesthetics;and 3) eliminate residual hazards t o t hepublic health and salety. SMARA's mineralresource conservation objective is achievedthrough a mineral inventory and economicassessment process termed "classificationdesignation. Infonnation on the locationof important mineral deposits is developedby DMG's SMARA Oassification Project.and used by the SMGB in designatingthose deposits which are of economicsignificance to a region, the State. or thenation. Local govemments use this information in developing mineral resourcemanagement policies and in making landuse decisions to assure the conservationand development of these resources,SMARA also provides for a coopera

tive State and local program to assure thatthe environmental impacts 01 miningare minimized and that mined lands arereclaimed to a useable condition (Photo 1).SMARA reclamation requirements applyto all lands in the State. including federallymanaged lands (see Pirozzoli and Pompy.this issue). Every mining operation in Califomia that plans to remove more than1.000 cubic yards (765 m)) of material ordisturb more than 1 acre (4.047 m") musthave an approved reclamation plan inaccordance with SMARA prior to miningoperations. Plans fOlWarded to the MLRPby lead agencies are reviewed to ensureSMARA reclamation plan requirementsand SMGB regulations are met. Leadagencies are advised of any infonnationrequired by SMARA which is not in theplans.

In 1987. changes to SMARA underAB 747. provided a ~ w i n d o w ~ lonoestedmining operators to file reclamation plansto be in compliance with SMARA Theamendments reqUired that all vestedsurface mining operations: \) have anapproved reclamation plan by July 1.1990: 2) be pending an appeal with theSMGB: or 3) have ceased operations ifthey did not have an approved reclamationplan. and remain closed until a reclamationplan is approved. Since \990. MLRP staff

have assisted the SMGB in the review of41 reclamation plan appeals filed underAB 747 provisions.Recent changes in SMARA under

AB 3551 and AB 3903, effective January1991. provide lor State review and appealof reclamation compliance issues (Newton.1991). Many enforcement requirementsare implemented by the DOC's Office ofMine Reporting and Reclamation Compliance (OMRRq. Since passage of this newlegislation. MLRP. SMGB. and OMRRCstaff have been conducting reclamationVJOrkshops for lead agencies and mineoperators to enhance understanding 01respective responsibilities under SMARAand to promote beller reclamation practices throughout the State. MLRP staffhave also assisted the SMGB and OMRRCon issues related to reclamation compliance. financial assurances. and the development of reclamation standards.Reclamation StandardsRevisions to SMARA. under AB 3551

and AB 3903, required the SMGB toestablish minimum. verifiable statewidestandards lor the reclamation of minedlands. which apply to each mining opera-t ion to the extent they are consistent withthe planned or actual subsequent uses ofthe mining site. During the past 2 years.MLRP stall have worked closely with theSMGB in the development and publicreview of proposed regulations that establish minimum standards lor reclamation.The regulations were adopted by SMGB inSeptember 1992. As required by SMARA.the regulations set standards for: 1) wildlifehabitat; 2} backfilling. regrading. slopestability. and recontouring: 3) revegetation:4) drainage. diversion structures. waterways. and erosion control; 5) prime andother agricultural land: 6) building. structure. and equipment removal: 7) streamprotection. including surface and groundwater: 8) topsoil salvage. maintenance.and redistribution: and 9) tailing and minewaste. The regulations also acldress closureof surface openings and clarify that financial assurances for reclamation shall beconsistent with both the approved reclamation plan and the reclamation standards. tothe extent the standards apply to individualmining operations.Acid Mine Drainage

In July 1992. the EnvironmentalProtection Agency (EPA) contracted withDMG lor a one-year study to evaluate the

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Pho10 4. ADMG engineern'lg geologIst surveys a CalTrans material site along Highway 120.40 miles east of Lee Vining in Mono County. The information obtained 'rom this survey. alongWith soil sample analySIS data and other flekl observations. wililleip determine the mostappropnate methods fOf site fegradmg and reclamation. Photo by RICk Wilson.

utility of sunace geophysical techniques inthe detection and monitoring of groundwater contamination from acid minedrainage (AMD). AMD has been identifiedas the largest single cause of adverse environmental impacts resulting from minewaste (University of California. 1988).including the contamination of both surface and ground water. AMD is particularly difficult to manage because it fonnsslowly. is difficult or impossible to stoponce fanned, and requires treatment thatcan be very expensive. Traditional methods used for detection. monitoring. anddelineation of ground-water contaminationrely on monitorir19 \A.lells which are expensive to install and provide infonnationonly at the location of the well. However.because AMD is generally associatedwith an increase in the concentration ofheavy metals and other ionic species thatincrease the specific conductance of bothsurlace and ground water. it is possiblethat the increase in specific conductancecould be used to map ground-water contamination from AMD using geophysicalmethods such as resistivity and geomagnetics. Surlace geophysical methods couldprovide a loI.v-c:OSt altematk.oe to monitoring wells for the detection of AMD andfacilitate the location of wells for monitoring purposes.

CALTRANS RECLAMATIONPLAN PROJECTIn May 1992. the California Department of Transportation (CarTrans) contracted with OOC/DMG to uJXlate redamation plans for approximately 80 minesites (borrow pits) in [nyc and Mono counties and portions of Kern and San Bernardino counties. 'The updated reclamationplans will suggest mining and site rehabilitation procedures that meet statewidestandards and department goals. conserveminerals. and minimize impacts on theenvironment. Under this contract. DMGstaff conduct vegetation and wildlife surveys. prepare revegetation plans. conductslope stability analyses. and recommendmitigation and monitoring proceduresrelated to revegetation. hydrology. erosioncontrol. and slope stability. In addition.DMG staff provide lead agencies withinfonnation needed to complete documents required by CEQA. To addressthese issues. CaITrans Reclamation PlanProject (CRPP) staff provide expertise inplant ecology and revegetation. wildlifebiology. and engineering geology.

Reclamation Plan PreparationReclamation plans developed byCRPP staff span a diverse environmentalgradient from the Mo;ave Desert tothe subalpine forests of the east SierraNevada. Reclamation measures address

site specific issues such as aridland revegetation. and erosion and sediment controlfor pristine subalpine stream corridors.Through close coordination with otherState and federal agencies such as theCalifornia Department of Rsh and Game(CDFG). State Water Resources ControlBoard (SWRCB), Bureau of land Management (BLM) and U.S. Forest Service(USFS). the reclamation plans are prepared in accordance with SMARA requirements, federal Best Management Practices. CEQA. and the SMGB regulationsfor surface mining and reclamation practice. Updated reclamation plans lorCarrrans will help guide the use of theState's mineral resources 10 ensure asafe and productive enVironment forCalifornia's present and future generations. while allowing the developmentand maintenance of a safe and effectivehighway system. In addition. interagencycooperation facilitates compliance withState and federal laws and results in monetary savings to the agencies involved.Geologic AssessmentsCRPP staff assess existing and pro

posed pits to document geologic concli-

lions. erosion potential. topography. anddrainage patterns (Photo 4). Geologicinlonnation is used to analyze site hydrology and slope stability. develop drainageplans. address erosion and sediment control. and prepare drainage and erosionplans to minimize the impacts of proposed mining on sunace and groundwater quality. Information includes anevaluation of the potential for erosion,sedimentation. acid mine drainage. andslope stability problems associated withproposed mining and reclamation. CRPPstall also develop site specific recommendations for measures to prevent or minimize adverse effects of mining and reclamation on the environment. Reclamationplans for each site will include maps andcross sections to show existing and proposed reclaimed site configuration.Biologic AssessmentsTIle narrow seasonal window forbiologic surveys necessitated an immedi'ate response by CRPP to conduct biologicsurveys for the first set of40 pit sitesduring the spring and early summer of1992. Some of the sites were revisitedduring the fall avian migration to lind out

if sensitive species had used them. Thesesurveys will fonn the basis for determiningproject impacts to sensitive species andfor developing appropriate revegetationplans. Reclamation plans include revegetating lands disturbed by surface mining

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operations: methods for removing. storing. and replacing topsoi.l: the use of soilamendments and fertilizers INhere appro-priate: selection of suitable plant speciesand planting techniques: and care of vegetation reestablished following mining.

PhOlO 5. During the !ield review of proposed TImber HaNeslmg Plans, THPRP staff address areas wllh high alld extremeerOSion hazard ratings. unstable stream banks and lalldsliding.road constructIOn alld haNestlng on Sleep slopes. alld cumulatlve effects related 10 erOS/Ofl and sedimentation. THPRPstaff are prepanng an Inventory of efOSlVe walersheds thaImay be affected by timber harvesllng Photo by Tnnda L.""""" , , ,n

TIMBER HARVESTING PLANREVIEW PROJECTDMG's Timber Harvesting PlanReview Project (THPRp) provides engi

neering geok:lgic r of Tunber Harvesting Plans (THPs) submilled to CDF toensure jXlIenliallandslide. erosion. andsedimentation areas are not adverselyaffected by road construction and othertimber harvesting operations. DMG ge0logists also serve on technical commilleesconcerning forest practices. address theBoard of Forestry (BOA on issues relaledto geologic and erosion hazards on timberlands. conduct training on slope stabilityand related geologic topics for CDF andindustry personnel, inspect geologic anderosional problems associatedwith violations 01 the ForestPractices Act (fPA). and prCNideexper1lNitness teslimony in courtactions involving CDF and BOF.THP Review

Under the FPA of 1973.ll-iPs are required for aU pr0posed timber harvesting on pri-vate or State forest lands in California. ll-lPs are submined toCDF in lieu of an ElR and arereviewed by represenlives ofCDF. CDFG. and the appropriate Regional Water Quality Control Board (RWQCB). The reviewlearn screens the plans for conformance to all standards andForest Practice Rules (FPRs) thatare in effect at the time the planis submitted. For most plans. thereview team requires a preharvest ftekl inspection. An inspection by a DMG geok:lgist mayalso be requested if the THP isIOf geclogic terrain where slopestability problems may occurduring road construction andlimber harvesting (Huffman andBedrossian. 1979). CDF hascontracted with DMG since1975 to make such r ~

During the preharvest inspection. DMG identifies and evalu-

ates poIentia! environmental effects oflogging practices In unstable environments.PaI'ticUar allention is given to exiSting andproposed road alignments. areas of activesoil movement. stream crossings. pro-posed logging on steep slopes. and areaswith high or extreme erosion hazard ratings (Photo 5). With recent changes inthe FPRs. additional emphasis is placedon cumulative effects of a given THP onerosion and sedimentation in the watershed(s) in which it is kxated (see Huber.this issue). ll-iPRP staff confer IAlith theforesters. bdogists. water ~ i t y specialists. and Iogge:rs concerning jXlIentia!impacts and alternative methods of k:lg-ging. Upon completion of the preharvestIlspection. ll-iPRP staff recommerv::Imitigation measures based on engineer'ing geology. prepare maps. and VJTitereports for each plan. decribing the findings and explaining the recommendations.When geologiC conditions are particularlysevere or require mitigation using engi-

neered structures. THPRP staff recommend that a detailed geologic report beprepared by an engineering geoIogJcconsultant certified in California

Whether a plan is approved or diSapproved, and what mitigation should beincluded in the plan. is decided by recommendations from participants of lhepreharvesl inspection and public comments received by CDF prior 10 a secondreview learn evaluation. In reaching adecision. CDF must address in writlflgaU environmental issues raised duringthe review process. statements of n0n-concurrence by revi0N tearn members.and recommendations of the review leamthat are noc required in the final plan ThelliP. the THP review process. and theapplication of lhe FPRs are consideredthe functional equivalent of EIR preparalion urder CEQA.

In addition 10 making preharvest fieldinspections, THPRP staff makelollov.rup inspections of loggedareas that have geologic reviewsand. when r ~ e d . conductreviews of sites proJX)SOO underCOF Timber Sales. and CaliforniaFOfest ImprCM?ment and Vegetal jon Managemenl ProgramsMore detailed reviews are pro-vided for geoIogjc and landslidehazard problems related to pr0posed construction al CDF (irestations and CDF conservation(prison) camp sites. DMG staffalso assist CDF in evaluatingerosion control measures neededfollowing major wildland fires.Forest Practice Rules

The FPA assigns authority toBOF to adopl ruJes alfec11flgfore:SlJy and fire protection thatCOF must then enforce (MartIn.19 9) BOF has appointro van-ous sulxonuniltees and taskforces 10 SI1.Jdy specific forestpractice issues_ THPRP stall haveparticipated on numerous BOFtask (orces and suocommilteesrelated to watercourse and lakeprotection. logging roads andlandings. erosion control in granitic terrain (Bedrossian. 1(91).and landsliding/rnass waSlIflgconcerns. Most recently. THPRPstaff haw provided inpulto CDFand BOF regarding proJXlSed

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regulalions related to the evaluation ofcumulative effects and identificalion of sensitive watersheds.Watersheds Mapping

Since 1981. CDF has conlracted withDMG 10 map geologic and geomorphicfealures relaled to landsIiding in selectednorth coast walersheds. The data are usefulin the preparation and review of THPsand as a Iand-manager's guide fo r recognizing areas of potentially unslable groundwhere on-sile geologic review is neededprior 10 development. DMG is also compiling an inventory of highly erosive watersheds In California lhat may be affectedby timber harvesting. The IA/Ork includesdevelopment of a Geographic InfonnalionSystem (GIS) and the preparation of mapsat a scale of 1:500.000 shooring the relative erosion sensitivity and hazard of individual watersheds.

REFERENCESBaker. DeAnn. Ferguson. J.M . Keene. K.A.,Milligan. Pamela. Rlvasplata, Antero. 1987,General plan guklelines: OfIice of Planningand Research. Sacramenlo. 368 p.8edrossian. T.l., 1991, Timber harvesllng IngrarlJllC lerrain, Grass Valley Creek. TnMyCounty CALIFORNIA GEOLOGY. v. 44,no 11. p. 25Q.255.Collins. Brian. and Dunne, Thomas, 1990,

FlUVial geomorphology and river-gravelmining: A guide for planners. case sludiesincluded: California Department 01 Conservation. Division of Mines and Geology,Special Publication 98. 29 p.

Department of Educallon. 1989. SChool Slleselection and approval guide: SChoolFacilities Planning Division. Sacramento,34 p.Evoy, Barbara. and Holland. Mel. 1989. Surface groundwater managemenllfl surfacemll1ecl-land reclamalion California Departmenl 01 Conservation, DIVision of Minesand Geology. Special Report 163, 39 p.Greenslelder, Roger, 1971, SelsmologlC andcrustal movement investigations o! theSan Femando earthquake: CAliFORNIAGEOLOGY. v 24. no. 4-5. p 62-68Hart. EW . 1990, FaultRupture haZard zonesin CaJitornia. Alquist-Priolo SpecIal Studies Zones Act 011972 With Index 10 Spe-

CIal Studies Zones maps: Calilornla DlviSIOfl 01 ~ J l l n e s and Geology Special Publicat1Ofl42, Revised 1990.26 p.Herson, A.l" 1987. EnVlfonmenlal perminiogExpediting lhe NEPA process: Naturalresources & enVlfonmenl: Journal 01 theSection 01 Natural Resources law of lhe

American Bar AssOCiatIOn. v. 2. no 3,Winter. p. 13-15,46.Huffman, M E_. and Bedrossian. TL . 1979.The geologisrs role in timber harvestplanning' CALIFORNIA GEOLOGY. v 32,no 6, p 115119.Koehler. Dave, 1991, Canada geese - A

sweet song IS back The Trust CUlrent.News lor Summer 1991 f rom The SanJoaquin River Parkway and ConservationTrust.Martlfl. E.F.. 1989. "A tale 01 two certificales"'The CalifornIa Foresl Practice Program1976 through 1988: Calilornia Department

01 Forestry. 299 pMeehan, J.F., 1982, PublIC school and hosPilal budding geologIC hazard conslderalions. In Hart. E. W. Hlfschleld, S.E.,and SChull. S.S .. editors. PrOCeedings:

Conference on earthquake hazards in lheeastern San Francisco Bay area, Calilornia: California Department of Conservation, DlYtsion 01Mines and Geology Special PublICation 62. p. 387-391.Mintier. J.L.. and Stromberg, P.A., 1983,seismic salety altha local level: Doesplanfllng make a difference?: CALIFORNIAGEOLOGY. v. 36. no 7, p. 148154.Newton, Gail, 1991, Update on the SurfaceMining and Reclamation Act of 1975:CALIFORNIA GEOLOGY. v. 44. no. 12 .p.288-29O.Newton. Gail. and laldet. Laura, 1992. Nursery sources lor California nabvB p1anls1992: California Department of Conserva!Ion. Division of Mines and Geology.Open-Fde Report 9004. 30 p.OfIice 01 the State Architect 1992. LanderslBig Bear earthquakes, PrehmmaryRepor1-Public Schools Unpublishedmemorandum. 4 p.Remy. M.H . Thomas. T.A., Duggan. S.E.,and Moose. J.G.. 1990. Guide 10 lheCalifornia Environmental Duality Act(CEOA): Solano Press Books. PomtArena. Calilofflla. 479 p.Smith. T.C . 1985. Geohazards inlormatlOn Ingeneral plans: Problems and recommendahons: Unpublished M.A. theSIS. Consorllum 01 the California Stale UniverSity andColleges. 61 p.Ufllversily 01 Cafiforma, Berkeley. 1988. Minin9 waste study, final report: Unpublishedreport, Mining Waste Siudy Team of U.C.Berkeley. 416p.Van K e k e f l ~ . l o r r a m e . and Kay. B.l., 1986,AevegetatlOfl 01 diSlurbed land in CallIer

nia: An element 01 minedland reclamation: Cahlorflla Department 01 Conservatlon, CalifornIa DIVISion 01 Mines andGeology. Open-File Report 86-14,105 p.

DMG Notes Useful in Preparationof Environmental Documents

DMGNOTE TiTLE26 Surface Mining and Reclamation Ac t of 197542 Guidelines 10GeoIogiclSeismic Reports44 Guidelines fo r Preparing Engineering Geologic Reports45 Guidelines for Geologic Reports for 11mber Ha1VCSting P1artS46 Guidelines lo r GeologiclSeismic Considerations irt EnvirOllmerttallmpactRepo",47 Guidelines lo r Geologic Reports on Offshore Operations and Facilities48 Checklists fo r the Review of Geologic/Seismic Reports fo r Hospitals49 Guidelines fo r Evalualing lhe Hazard of Surface Fault Ruplure

AVAILABLE WITHOUT CHARGEAT DMG OFFICES

CALIFORNIA GEOLOGY NOVEMBER DECEMBER 1992 '"


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Geologic Conditions atThree Rancho Palos Verdes Subdivisions

Los Angeles CountyJACK R. McMILLANEngineering GeologistDivision of Mines and Geology

INTRODUCTIONThis article describes three PalosVerdes area subdivisions reviewed bythe Environmental Review Project (ERP)(Hgure 1). These examples illustrate someof the geologic condit)ons tnat can beencountered and how they are addressedin ERP review. The Palos Verdes areawas chosen because there are a numberof geologic: hazards on the Palos VerdesPeninsula that have affected land use andhousing sulxHvisions in the past. Theongoing demand for new housing has leftland developers and city planners examining properties that have not been devel-

-

oped because of geologic and OUler land-use constraints. The projects proposedfor this area have benefited from the multi-level (local. county. and State) review underthe California Environmental Quality Act(CEQA).

BACKGROUNDThe city of Rancho Palos Verdes is onthe southern side of the Palos Verdes Pen

ninsula about 25 miles (40 kml southwestof dov.!ntoum Los Angeles. Since the citywas incorporated in 1973. much of thehilly terrain along Hawthorne Boulevard.Crest Road. and Palos Verdes Drive WestI ~ ' l " , ' ~

has been developed for residenllaJ andcommercial use. However. a large portionof the marine terrace along Palos VerdesDrive South is open land.

This land is undeveloped partlybecause of a change in zoning densitywhich occured in 1975 and partlybecause of past movement on the Portuguese Bend. Abalone Cove. KlondikeCanyon. and Flying Triangle landslides.The Portuguese Bend landslide is one ofthe most studied and publicized landslidesin the area (EhUg and Keene. 1985).Beginning in 1956. movement on thislandslide damaged or destroyed more

..

Figure 1. Location map showmg three subdivisions In the Palos Verdes area: Wiodport. TentatJVe Tract #46628. aod Forrestal. The RanchoPalos Verdes (RPV) Redevelopment Project. FlYing Tnangle. Abalone Cove. Portuguese Bend. and Klondike Canyon landslides are alsoshown. Modified from Ehlig. /992.

CALIFORNIA GEOLOGY NOVEMBER/DECEMBER 1992


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than ISO private residences and disruptedutilities and public roads. The ensuinglitigation cost taxpayers $7.5 million.Los Angeles County has spent an additional $10 million to maintain publicstreets in the Portuguese Berxl area be-cause of the continued land movementwithin the slKle complex (Scullin. 1990).The city's Rancho Palos Verdes Redevelopment Project was started in 1984arxl has ben involved in stabilizationefforts in this area since then (UrbanFutures. Inc.. 1984).

In the past few years, several majorproperties have become available fordevelopment in Rancho Palos Verdes.The type and scale of development represents a significant change in recent landuse development. When the Division ofMines and Geology (DMG) was reviewingthe three sulxlivisions discussed in thisarticle. Rancho Palos Verdes was processing six development applications. Theyrange from single lot splits to largemixed developments that may includeresidences. apartments. recreation areas.and golf courses. Because of the adversegeologic conditions. slope instabilities arean important consideration for city planners making landuse decisions.REGIONAL GEOLOGY

The Palos Verdes Peninsula is atopographically and structurally high blockof ground underlain by folded sedimentaryrocks of the Miocene Monterey Fonnation (Figure 2). The peninsula is 9 miles(14 kmllong and 5 miles (8 km) wide

with a maximum elevation near 1.480feet (450 mI. The middle Miocene andyounger bedded sedimentary rocksexposed on the peninsula are faulted andfolded over a core of Mesozoic CatalinaSchist basement rock. Basaltic rocks areexposed in several areas along the seacliffs and in association with volcanicrocks (andesite) in the peninsula's interior.The bedrock is overlain by various unitsincluding terrace material. alluvial deposits. and artificial fill. The peninsula slopesare cut by a series of marine terraces andterrace remnants that stairstep along thepeninsula flanks. The terraces are bestdefined and most extensively preservedon the west and south slopes. Thirteenprincipal terrace levels have been recognized by Woodring and others (1946).Massive ground failures occurred onthe peninsula during Holocene and latePleistocene time after weak layers withinthe bedded rocks were saturated fromlong periods of rainfall. In places. thelandslides have signifkantly modified andreshaped the landscape and topography.

SITE CONDITIONSThe four most commongeologichazards in Rancho Palos Verdes are landsettlement. shoreline cliff erosion, activelandslides. and inactive landslides(Envicom. 1975).Lond settlemenl is the compactionof unconsolidated soils over time. Compaction is often caused by foundationloading. the settlement of unengineered

and weak fill. or the loss of lateral supporton slopes. City grading codes and inspection are generally an effective guard againstthis type of hazard.

Shoreline cliff erosion results fromcontinued wave erosion at the cliff bases.Numerous small-scale failures have led thecity to establish setback requirements toprotect developments that extend to thecliff edges.Active landslides are areas withextremely unstable ground unsuitablefor residential development. They arerestricted in the city's General Plan bydesignating them as open space or hazardareas.Inactive landslides are areaswhere massive downslope movement hasoccurred. but the landslide material is notpresently moving. Movement in theseinactive areas cook! be triggered by longperiods of rainfall. seismic shaking. construction activities. or drainage changesthat unbalance the groundwater conditions.TIle following infonnation was takenprimarily from recent CEQA documentssubmitted through the Slate Clearinghousefor public agency review.

Windpon ProjectThe Windport Project is a proposedsingle-family residential. four-lot subdilJisionon 8. 8 acres (3.5 hectares) originally zonedas an open-space hazard area. ApprOXimately one-half of the site VJill be rezoned

P a l o s V e r d e s HillsNORTHEAST-- - -

- - - - - --L os A n g e l e s B a s i n

-Se(/; ................. - - ...... frIef//a --...... ry ----- .......... ...... ROCks-- - - - - - ~ -MetamorphicRocks1111111I1111I1

MetamorphicRocks

11I111I11I11OFFSHORE

FAULT PALOS VERDESFAULTFigure 2. $dlemallc prohle through the Palos Verdes Peninsula.

CALIFORNIA GEOlOGY NOVEMBER/DECEMBER 1992 '75


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Photo 1. Near-vertical quarry slope at the Forrestal Project. Photo by J.R. McMillan

to residential use as part of the project;the rest will remain an open-space hazardarea. lhe proposed building sites are atthe end of Wlndport Drive along thenorth side of Aqua Amarga Canyon. Thissection of the canyon was filled duringthe late 19505 and early 19605; there isminimal information on the compositionand placement of the fill. lh e buildingsites are bordered on the south by agutted stream channel and on the westby a steep. west-facing fill slope morethan 100 feet (30 m) high. lhe areahas undergone settlement because ofthe WlConsolidated nature of the under-lying fill.

The geotechnical reports for thisproject indicate the property has twomajor geologic problems: 1) lh e material overlying the bedrock consists of shallow landslide deposits and up to 120 feet(35 m) of non-engineered artificial fill; and2) the bedrock underlying the fill is foldedinto a syncline with its north limb dipping12-14 degrees toward the south. obliqueto the fill sk>pe's face (Jim Hinzdel andAssoc . 1991). lhe slope stability concli-tions are complicated by the unknovJnnature of the fill and the Jack of a sub-drain system.

Geotechnical investigations of thissite began in 1987 and have continuedthrough a number of reports and reviews.In July. 1991. the Draft EnvironmentalImpact Report (DElR) determined the siteis suitable for the proposed developmentprovided that a number of recommendations are follO'J.Jed. These recommendations include a driUed pier and beam foun-dation design. sizing requirements for thepiles. removal and recompaction of aportion of the fill on the lots. and supplemental inspection of the drilled piersand foundation rock during construction.Aminimum 01 two piezometers and asettlement marker would be installed dur-ing construction to enable water level andcompaction monitoring of the fill.

DMG revie\.ltd the DEIR for thisproject and concluded thai the cumulativeeffect 01 the geologic conditions has created a potentially unstable fill that will failunder saturated conditions when accompanied by earthquake shaking. Also. theadverse dip of the underlying bedrockpresents an unknown hazard to the proposed deep foundations. DMG felt the

conditions were sufficient to limit development on the artificial fill area and an advi-sory review letter was sent to the leadagency during the CEQA review period.lhe CityCouncil denied this proJect inOctober 1991. based primarily on plan-ning staff concerns about exces'sivesettlement.Forrestal Project

lh e Forrestal ProJect consists of42 single-family lots and four open-spacelots on 2\ acres (8 hectares) of a 163acre(66-hectare) site. It is east of KlondikeCanyon in Rancho Palos Verdes andpartially within the Rancho Palos VerdesRedevelopment Pro)ect. Part of thepro)ect is on an old quarry site.

One ob;ective of the proJect is 10grade the area to stabilize the slopes andalleviate hazards associated with a nearvertical quarry wall (Photo 1). The necessity of cutting back the quarry slope wasanalyzed in the ElR.

lh e preferred grading solution proposed remedial grading of the existingquarry slope to decrease the risk of rockfall and increase the safety of hikers alongthe upper bluffs. The upper slope appearsto be made of colluvium and perhapsweathered rock (Photo 2). The proposedcut \A1OUki Rallen the lower slope andundercut Ihe natural upper slope abovethe quarry.

lhe original E1R was prepared in1979. A Supplemental ElR was preparedin 1991 to analyze potential impacts ofremedial grading and stabilization andto assess the environmental impacts ofthe past 10 years of local development.After reviewing the project. DMG felt thatCUlling back the toe of the upper slopecould destabilize the material and leadto downslope movement on the upperslope. DMG recommended that the character and stability of the material on thenatural slope above the quarry face beaddressed as part of the overall slopehazard assessment in the Final EIR. Mea-sures should be proposed to ensure thematerial on the upper slope remains inplace after the rock face is cut back.

The Forrestal Pro;ect was denied bythe City Council in July 1992. The land-owners have filed suit against the city.and the council is currently involved ina court supervised settlement procedure(Carolynn Petru. City Planning. oralcommunication. 1992).Vested Tentative Tract #46628

TentativeTract 1146628 is a 132acre (53-hectare) single-family residentialdevelopment just north of Poinl Vkente.The site is an extensive marine terracealong the west side of Palos Verdes DriveWest. Geologic concerns include cliffslope erosion and the possibility of large.undetected landslides.

'" CALIfORNIA GEOLOGY NOVEMBER'OeCEMBER 1992


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Photo 2. Natura! slope above the quarry lace. Note the break in slope. Photo byJ .R.McMIllan.

issue was addressed using a coastal setback line during project development. Atthe DEIR stage. the Division reviewed thedocument and returned a "no commentMreply on the basis that the site investigation contained adequate geoIogk data toensure publk safety from the geologichazards, This project was approved by theCity Council in March 1992 and is pending the recording of the fmal map.Observations and Conclusions

Unlike local review agencies. theDivision's ERP reviews projects fromthroughout the State. Therefore DMG canhelp standardize the geologic INOrk doneon projects and ensure a more even compliance with CEQA. In this role. ERPstaff have an opportunity to examinethe practical geologic techniques used incounties like Los Angeles and apply thosestandards to counties VJith less geologicexpertise.

Geologic exploration began on thispropeny in the mid-1950s when geologicinvestigation was conducted for the original propeny owners (Jahns. 1957). In1972. after additional geologic exploration. the tract was approved for gradingby Los Angeles County since RanchoPalos Verdes was not yet incorporated.While grading was in progress. LosAngeles County was sued by local residents who claimed that the housing density approved for the subclilJision was inviolation of the county'sGeneral Plan(lmpacl Sciences, Inc . 1991). In subsequent litigation, the court ruled in the

Ehbg, PL.. and Keene. AG_. 1986. Landslidesot the Palos Verdes Peninsula. Calirornla inEhl,g, P.L. edllor, Landslides and landslidem'tlgatlOTl ,n southem California (guide'book): 82nd Annual Meeting ot the Cofd,lleran Secl!On or Amenca. Los Angeles, Cali-rornla, 1986,p 195201Ehlog. PL .. 1992, EvolullOn, mechanICS. andm'togallOn ot the POl1vguese Bend Landshoe Palos Verdes Peninsula, Cahtomla InEngoneenng prachce on southern CallrornlaAssocoallOTl ot Englr'l&eong GeologIStS.Southern Califorllla SeellOn, Special publlcation No 4. p 531553.Envocom Corporation, 1975. TechOlcal database ror s e i s m ~ sarety and publIC safetygen9fal plan elements. Cltoes ot RanchoPalos V8foes, Rolling HIllS ESlales, andRoIhng Holls. lOOp

plaintiffs' favor and the county directedthe nearly-oomplete grading to be halted.The geologic evaluation of the prop

erty for the latesl proposed developmentincllXled approximately 90 borings. Thegeologic structurewas louOOIO contribulesignificantly to the slope stability aOO thesite was detemlined to be adequate forthe proposed development.

DMG commented on the dill stabilityhazard during Ihe Notice of Preparationstage of the CEQA documentalion. ThaI

REFERENCESImpact SCIences. Inc., 1991. Draft Enwonmen

lallmpacl Report no 35 tOf vesllng lenla-lIve Irac1"46628: State Cleannghoose No91031057

Jahns. R H .. 1957, Geology or tracl no. 19743.Palos Verdes Hills. Los Angeles County.CahforOia In Impacl ScIences, Inc,. 1991,Draft EnVlronmenlal Impact Repol1 no 35tor vestmg lenlatlve Iracl #46628 SlaleCleannghouse No 91031057Jim Hmzdel and ASSOCIates. Inc., 1991. DraftEnVironmentallmpaet repofl no 31 forlenlatlve parcel map no 18947,GR 1460: State Cleannghouse No. 91031087

Planning and DeSIgn SoluIlQllS, 1991. Supplemental EnvIronmental Impact Report lenta\lVe Iract no 37885 (Fofrestal PfO,ect)Slate Cleannghoose No. 90011 1I I

In the previous examples, some of thecomplexities of the Palos Verdes area havebeen examined and the geologic reviewprocess described. Environmental reviewat the State level can be a valuable component of multi-level review. HOO'e\Ier. aclear picture of the project must be presented in CEQA documents. TIle problems, mitigations. and geotechnical datamust be VJeIi organized and complete lorproper review. DMG"s objective is 10 workwith lead agency staff to ensure the projectis safe aOO environmentally sound. aOOthemitigations are appropriate for local aOOcumulative site coOOitions.

SCullin. M C.. 1990. E ~ c a v a l l o n and gradingcode admlfllSlratlon, InSpecllOn and enforcement: PrentICeHall. Inc.. 405 p.

Urban Futures. Inc .. 1984. Rancho PalosVerdes Redevelopment ProJect: DraftEnVIronmental Impact Report, Slate ClearInghouse No. 8408151 1,Vondef LJnden. Karl. and Lindvall. C.E. 1982,The Portuguese Bend landslide: landslideSand landslide abalement Palos V9fOOSPeninsula, southern Cahtornia: AssocIatlon ot Englneenng GeologislS. SoulhemCalirornia SeeIIOTl. p 4956.Woodnng, W.P.. Bfamlene. M.N.. and Kew.W S.W. 1946. Geology and paleontologyof Palos Verdes Hills. California: U.s.GeologICal StJrvey Protesslonal Paper 2fJ7.145 p .. 37 plates.

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Geologic Hazardsat the New Bay

Farm IslandBementary School

Alameda County$AH ~ A l L O'"

_u,

Ns., .'

o 5 10 Milltscl----''--,r--",o 10 Kilometer., .. .o." ' l .UI

"""'" ..".. I' [ ~ U L ( 1I

r - - - + ~ '.... ,.+11---. ...!7"'----"- l i " " ' ~ -

~ -'-_..,Figure 1. Map ot the san Fraf1ClSCO Bay region showing the approximate locationof the New Bay Farm Island Elementary School. Modified from Goldman. 1969.

TIM McCRINK. Engineering GeologistDivision of Mines and Geology

INTRODUCTION

The Hospital and School Site ReviewProject (HSSRPj of the CaliforniaDivision of Mines and Geology lOMG)reviews geologic and seismic hazardsinvestigations for elemenla'Y and middleschools under contract to the Office ofIhe Slate Architect (GSA). One projectrecently reviewed by HSSRP wasAlameda Unified School District's NewBay Fann Island Elementary School onBay Fann Island (Figure 1). In additionto being close to several active faults.the school design was influenced bysome unusual subsurface conditionsiocluding the presence of Young BayMud. hydraulically placed sand fill. andburied deslroyoer-class Navy warships.

GEOlOOIC SETTINGBedrock beneath the project site isJurassic 10 Cretaceous Franciscan assemblage. North of the project site. along thealignment of the San Francisco-OaklandBay Bridge. bedrock is composed of feldspathic sandstone. graywacke. siltstone,shale. interbedded chert and shale. andvarious types of basic and u1trabaslc igneous rocks. altered to greenstone and serpentine. This formation was severelydeformed. faulted. and eroded to a surface of considerable relief. then covered

VJith sediment.The bay sediments consist 01 fiveformations of late Quaternary age: theAlameda Formation. San Antonio Formation. Posey Formation. Merritt Sand. andYoung Bay Mud rrrask and Rolston.

1951).lhe Pleistocene Alameda Formation. which can be more than 200 feet

(60 m) thick. consists of layers of firmsand. sandy clay. and clay. According toRogers and FJgUers (1991). the upperAlameda appears to be a mixture ofmarine estuarine and continental alluvialsediments. while the lower Alameda iscomposed of a thicker continental facies.The San Antonio Formation is 15 to120 feet thick (5 10 37 mI. and consistsof clay. silty clay. and some sand rr raskand Rolston. 1951). Radbruch (1957.1969) separated the basal marine clayfrom the overlying alllNial facies. Sloan(1981) redesignated the basal clay as

~ Y e r b a Buena M u d . ~The Merritt Sand is an aeolian sanddeposited on an eroded surface duringlate Wisconsin time. It is a shallow freshwater aquifer that is exposed across mostof Alameda and Oakland. It is absent

where ercx:led by Holocene channels.and is often covered by Young Bay Mudwhere it dips below sea level (Rogersand FIguets. 1991).The youngest geologic unit in theEast Bay is the Holocene Young BayMud. These marine clays infiJIed lateWisconsin age channels as sea levelsrose 6.000 to 11.000 years ago. Themud reaches its greatest thickness of150 feet (46 mI. between Hunters Pointand the San Francisco Embarcadero(Rogers and FJguers. 1991). In the vicinity of Bay Fann Island the Young BayMud ranges in thickness from 20 to

50 feet (61015 m) (Golclman. 1969).Sloan (1992) studied boreholesamples drilled in 1969 from a proposed

bridge alignment thaI was to run fromHunters Point in San Francisco to Bay

". CALIFORNIA GEOLOGY NOVEMBER DECEMBER 1992


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Figure 2a. LocatIOn ofboreholes across SanFranciSCO Bay along theSouthern Crossing.MOlilfied from Sloan,1992.

122 22'30 '

"A o $ 1 Mil.~ ~ - r ; ~ ' ' - r - " ' ' : : : : ; ; K.lo....'. "122 15

I.20

..:[ JO"':>j ..,..w

Farm Island on the east side of the bay.As shown in Figure 2. this work indicatesthat the stratigraphic sequence underlyingthe New Bay Farm Island School site isPleistocene aliuviaVestuarine AlamedaFonnation overlain by Verba Buena Mud,which is unconformably overlain by upperPleistoceneMoiocene aeolian sand(Merritt Sand). Holocene estuarine sedi-ments (Younger Bay Mud) overlie thesequence.ACTIVE FAULTS AND SEISMICITYThere are active faults in the SanFrancisco Bay region which cook! affectthe proposed ew Bay Farm Island School

_ Holo(:ene 8S1uarine doposits Uppel PleisIoceneJHoloc:el aeolian_ Uppa' PeisloceoelHoloc8l'llllluv,al_ Yerba Buena Mud_ Pleisloe&ne slluviallflluanno

site. "The Hayward. San Andreas. andCalaveras faults are the most significant.The table 10 the right shOVJS the shortestdistance from the school site to thesefaults. and lists the significant historicearthquakes that have occurred oneach (Toppozada and others. 1981;Slemmons and Chung. 1982).Earthquake planning scenarios havebeen prepared for the effects of largeearthquakes on the San Andreas (Davisand others. 1982) and Hayward faults(Steinbrugge and others. 1987). Theseplanning scenarios indicate the schoolsite cook! expect M


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WorldWar I era Navy destroyer. Photo courtesy of Treasure Island Museum,

IBRIEF HISTORYOF THE SITEPrior to deYelopment. Bay FannIsland was a tidal flatland, Levees wereconstructed and much of the island wasfanned in the early part of the 20th century. However. these Jevees were prone

to failure by wave action and there arerecords of inundation of the fannland.Na"'Y destroyers, sold as scrap probablyin the 19205 or 19305. IJJere used asbreakwaters. Ten ships VJere placed end-to-end along the northwest end of BayFann Island. These ships can be observedon air photos taken prior to 1966. whenhydraulic filling began.The class 01 deslroyer believed to beburied at Bay Fann Island was knO\.Vl1 asthe "four-piper fluslldeck for its characteristic four exhaust stacks and relatively

low profile (see photo). The largest class01 destroyer built before Work:! War II. itwas 314 feet (96 m) long and 30.5 feet(9 m) wide. The depth of the hull was18 feet (5 mI. \Alith a maximum draft of12 feet (4 m) and 6 feet (2 m) of freeboard. The hull was made of 1/4-lnch(0.6 em) steel that was lightly plated toinhibit corrosion (Edward Vanderport.Treasure Island Museum, oral communication. 1991).Hydraulic Filling of New BayFarm Island

Hydraulic filling of the northVJe$tportion of Bay Fann Island began in late1966. The process usually requires thecreation of earth embankments. Afterward. sand can be hydraulically pumped.in this case from the San Francisco Bayto the area behind the embankments.and allO\4led to drain. People familiar withthe filling of Bay Fann Island say thatthe only compactive effort applied to thesand was the occasional movement ofbulldozers over the fill.SIGNIFICANCE OF THE SUBSURFACECONDITIONS TO SEISMIC HAZARDSThere are three reasons why seismicground shaking is a Significant consideration at this site. Rrst is the potential foramplification of seismic energy by the

underlying Young Bay Mud. The amplification of seismic waves was well documented in the San Francisco Bay areafollowing the 1989 Lorna Prieta earthquake (&rchardt and Hough. 1989).

Second is the potential for liquefactionof the sandy hydraulic fill materials onthe site. Similarly placed mateTialliquefiedat Treasure Island. the Oakland Harbor.Alameda Naval Air Station. and theOaklancllntemational AiT]X>rt in 1989.Rnally. it is uncertain how the buried ships1.UOl1IcI respond to strong earthquake shaking. and what effect they VJOUkl have onstructures built above them.EVALUATION OF GEOLOOtC HAZARDS

1be California Department of Education. recognizing the unusual subsurfaceconditions at this school site. asked GSAto pass the report to DMG for a review ofpotential geologic hazards. In the spring of1990. GSA requested that HSSRP reviewthe proposed project.First Review

Uke most projects reviewed byHSSRP, this project involved a two-stepreview. The first report submitted forreview was a "Geologic Hazards andFeaSibility Foundation Investigation" prepared for the Alameda Unified SchoolDistrict. [n this first report. the pro;ectconsultant identified the main geologicand seismk: hazards. and presented the

school district \Alith foundation alternatives. The report also recommended thatmore detailed subsurface investigation beconducted at the site.HSSRP recommended that subse

quent investigations should identify thehorizontal and vertical extent of the buriedships. evaluate the potential for soilliquefaction as well as discuss what effect theOctober 1989 Lorna Prieta earthquakehad on the site. and evaluate the potentialfor seismic seulement and differentialcompaction, The potential for site amplification was noted as an issue that shouldbe addressed.Second Review

HSSRP received copies of subsequent investigation rep:l1ts in January1991, These reports included an updatedgeologic hazards evaluation. a geotechnical investigation. and a detailed investigation of the Iocatlon of the burieddestroyers.The consultant studied the site usingaerial photographs taken between 1947and 1988. The location of the destroyerswas detennined by a magnetometer studyand by drilling 68 soil borings. The con-

'" CALIFORNIA GEOlOGY NOVEMBER DECEMBER 1992


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sultant proposed to mitigate the potentialfor soil liquefaction and long-term differential settlement by driving erKl-bearingpiles to firm alluvium at depths of 45 to70 feet (14 to 21 mI. Building foundalions were proposed to span the buriedships to avoid having to drive pilesthrough the ship hulls. The piles werespecially designed to withstand excessivebending without damage. because liquefaction of the upper IS to 20 feet (5 to6 m) of the site soils during a major earthquake would result in very Umited lateralresistance to such movement.

HSSRP review included a reconnaissance-level magnetometer survey byDMG geophysicists on the portion ofthe sHe northwest of the existing buriedships. This area is obscured by bay waterin DMG air photos taken in 1939 andthe consultant"s geophysical survey didno t incll.de this area. DMGs magnetom-

Borchardt. A.D .. and Hough. S.E .. t989,Mud may have contributed to collapse ofthe Nimitz Freeway dunng Loma Prietaearthquake: Earth in Space, v. 2, no. 4.December 1989.DavIs, J. F.. Bennen. J, H.. Borchardt. G. A.,Kahle, J. E.. RICe. S. J" and Silva. M. A.,1982. Earthquake planning scenario for amagnitude 8.3 earthquake on the San

Andreas fault in the San Francisco Bayarea: California Division of Mines andGeology Special Publication 61. 160 p.Goldman. H. B., editor. 1969. GeologIC and60glneenng aspects of San FranCISCOBay fill: California DiviSion of Mines andGeology Special Report 97, \30 p.Radbruch. D.H .. 1957. Areal and engineering geology of the Oakland West Quadrangle: U.S. GeologICal Survey Map1-239. scale 1:24,000.Radbruch, D.H., 1969, Areal and engilleennggeology of the Oakland West Quadrangle: U.S. Geological Survey Map GO768, scale 1:24.000.

eter survey was conducted to determineif metallic debris or other delectableobstructions were hidden from view onthe air photos, or emplaced after 1939,DMG's survey shovJed no large anomalies that would indicate that additionalsubsurface investigationswere needednorthwest of the buried ships.

DMG also evaluated the possibilitythat the buried ships might still containlarge water-filled spaces due to incomplete hydraulic filling. DMG"s concernwas that these void spaces could causethe ships to shift or could induce significant surface selliement during a largeearthquake. Experts at the TreasureIsland Naval Museum believe that theships were signifk:antly stripped. leavingseveral large openings in the deck atthe time these ships were buried. Withthe exception of fuel and water tanks.and perhaps VJhere there are double

REFERENCESRogers. J.D., and Figuers. S.H .. 199\, Sitestratigraphy elfects on soil amplificatIOn Inthe vicinity 01 Oakland. California: Proceedings. Foorth International Conference on Seismic Zonallon, August 25-29,1991, Stanford University: EarthquakeEngineering Research Institute, Oakland.p.343-350.5lemmons, D. B" and Chung, D. H., \982.

Mcl)umum credible earthquake magnitudes lor the Calaveras and Hayward!ault zones, Califomla in Hart, E.W"Hirschleld. S,E .. and SChulz. 5.5.. editors. Proceedings: Conlerence on Earthquake hazards In the eastern San Fran,cisco Bay area: Calilornla DIVISIOn ofMines and Geology Special Publication62, p. 115134.Sloan, Doris, 1981, Ecostratigraphic study 01Sangamon sediments beneath centralSan Francisco Bay: Ph.D. dissertation InPaleontology. University of California.Berkeley. 1981.

hulls. it would have been diffiruh forlarge voids to have developed (EdwardVanderport. Treasure Island Museum.oral communication. 1991). This indiocates there is a Ioo.v potential for significant effects caused by voids in the ships.

HSSRP's second review of thesite Included an evaluation of theconsultant's reports. as lNCli as air photo.magnetometer. and historical information.1he data presented by the consultant. aslNCll as that gathered by H$SRP in itssecond review. indicated a comprehensive investigation had been conductedfor this project. and that the proposedfoundation system would likely be thebest to inhibit structural damage duringa major earthquake. On this basis.HSSRP recommended to OSA that nofurther study would be nC(;essary forthis project.

Sloan. Doris, 1992, The Yerba Buena Mud:record of the lastinterglacialpredecessorof the San Francisco Bay, Califorma:GeologICal Society 01 America Bulletin,V. 104. p. 716-727.

SteinbfUgge, K. V.. Bennett, J. H., Lagono,H. J" Davis, J. F.. Borchardt. Glenn. andToppozada. T. R" 1987, Earthquakeplanning scenario for a magnitude 7.5earthquake on the Hayward Fault Ifl theSan Francisco Bay area: Califomla Division of Mines and Geology Special Publication 78. 243 p.

Toppozada, T. R.. Real. C. R.. and Parke. D.L.. 1981, Prepardtion of isoseismal mapsand summanes 01 reported effects for pre1900 California earthquakes: CahfornlaDivision of Mines and Geology OpenFileRepon81-11 SAC. 182p.Trask. P.O., and Rolston. J.w., 1951, Engl'neenng Geology 01 San Fraoosco Bay,California: Geological Society of AmencaButletin. v. 62. p. 10791110.

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Castle Mountain Mine layout.

Implementing anAwardWinning

ReclamationPlan at CastleMountain Mine

San Bernardino CountyLYNN A. PIROZZOU. Vice PresidentEnvironmental and Government Affairs

Castle Mountain Ventureaod

JAMES S. POMPYMined-Land ReclamationProgram ManagerDivision of Mines and GeologyINTRODUCTIONAPproval of a reclamation plan is prerequisite to mining in California. TheMined-land Reclamation Project (MLRP)provides technical assistance in the reviewof reclamation plans. Plans are reviewedby MLRP to determine il they include

mandatory information and are technically sound. This article highlights theimplementation of the reclamation planfor Castle Mountain Mine. Redamation isproceeding according 10 a plan approvedby San Bernardino County. Prior 10its approval, the plan was enhanced torefJed input by MLRP.

PROJECT DESCRIPTIONCastle Mountain Mine is in the MojaveDesert about 100 miles (160 kin) east ofBarstow. California. and about 70 miles

(110 kin) south of Las Vegas. Nevada.The project encompasses approximately2.620 acres (10 kin:?) of Bureau of LandManagement (BLM) property and 115acres (46 hectares) of patented miningclaims. Elevations range from 4.100 to5.100 feet (1.250 to 1.555 m). P r e c i p i t a ~tion averages 8 inches (20 em) per year.Temperatures range from below freezingduring the occasional cold snap in thewinter. to as high as 110 degrees (43oqduring the summer.

Search LightAccess Road

Viceroy Resource Corporationacquired control of the Castle MountainProject in I985. On March 7. 1991.Viceroy Gold Corporation. a whollyowned subsidiary of Viceroy ResourceCorporation. entered into a venturewith MK Gold Company. a subsidiaryof Morrison Knudsen Corporation.Castle Mountain Venture was fonnedwith MK Gold receiving a 25 percentparticipating interest upon paymentof $17.5 million, Viceroy retains a75 percent interest as manager of CastleMountain Venture.Castle Mountain Mine is a typical

open-pit heap-leach gold operation.Groundbreaking ceremonies for the1OO.OOO-ounce-per-year Castle MountainMine were held on April 15. 1991.Proouction is anticipated to continuethrough the year 2000. with potentialfor extension of operations for severaladditional years. The deposit consistsof two distinct are b


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Monitoring and Maintenance ProgramA 10-year monitoring and maintenance program has been established toensure that appropriate procedures areimplemented to protect the environmentand reclaim areas disturbed by operations.During this lO-year time frame. performance goals will be monitored to ensurereclamation success. In addition. federal.

Success of Viceroy'srevegetation program willbe determined by densityand diversity of perennialspecies. Vegetation onreclaimed areas will becompared to speciesfound on undisturbedcontrol sites. Controlsites will be selected thatare representative 01naturally occurring veg.etation growing underconditions similar tothose found on the minesite. The lO-year goalfor vegetation density is21 percent of the control.The 10'year goal for species diversity is 15 percent. expressed as a similarity index ofthe control. A similarity index measuresthe similarity 01 one multi-species population to another by comparing the species

common to both.

Performance GoalsAn important aspect of the reclamation plan is the establishment of measur'able performance goals. Performancegoals are important to the mine operatorbecause they establish clear criteria forthe release of financialassurances. Performancegoals are also importantto the regulatory agencybecause they offer ameans to monitor compli-ance with the approvedreclamation plan.

by the end of each year and must beadequate for the agencies to completereclamation in the event the operatordefaults. Periodic adjustments will includeincreases based on additional disturbancesin the following year as well as decreasesto account for areas successfully reclaimedduring the past year. Currently a bond isposted in the amount of $619.000.

Pursuant to an agreement betweenBLM and the county. a single surety bondis held by the two agencies to assure rec-lamation in accordance with the approvedreclamation plan. This bond is administered by the county for the benefit of bothagencies. The amount of the bond isbased on the total acreage to be disturbed

Financial Assurancefor Reclamation

federal requirements as well. Development of the plan was coordinated by BLMofficials in the California Desert District.Needles Resource Area office.

A Memorandum of Understandingbetween the State and BLM specifies howthe California Surface Mining and Recla-mation Act (SMARA) is applied to miningoperations on lands within the jurisdictionof BLM. Prior to mining. Viceroy wasrequired to obtain approval of the reclamation plan from San Bernardino Countyin accordance with SMARA. Since mostof the land is within the jurisdiction ofBlM. the reclamation plan had to meet

and natural resources. Viceroy's goal wasto develop a plan that would minimizeimpacts through progressive and innovative reclamation.

Photo 1. Aerial photo of Caslle Mountain's leaching operations. Photocourtesy of Viceroy Resource Corpora/ion.

RECLAMATIONThe San Bernardino County PlanningCommission approvedthe reclamation plan forCastle Mountain Mineon September 27.1990. following alengthy public hearing.At the hearing. testimonyin support of the plan was presented byrepresentatives from San BernardinoCounty. MLRP. BLM. and the Sierra ClubLegal Defense Fund. which also represented the Wilderness Society and theNatural Resources Defense Council. Theplan was hailed by the California environ'mental community as state-of-the-artprecedent-selting. and a model for futurereclamation planning. The follO\ving year.the Califomia Mining Association awardedCastle Mountain Venture the 1991 Excel-lence in Reclamation Award for Best Rec-lamation Plan. Mining operations by theirvery nature involve the disturbance of land

A piping collection system is used torecover the gold-laden solution from theheaps and deliver it to the pregnant solu-tion tanks. Most heap-leaching operationsuse open leachate ponds for solutionstorage. Open solution storage ponds canaUract wildlife and lead to mortalities.Viceroy engineered a fully enclosed sys-tem using sealed steel tanks for solutionstorage. The enclosed system protectswildlife and eliminates many of the envi-ronmental problems associated with openponds.

Gold is extracted from solution byadsorption in a series of columns usingactivated carbon. Thegold is then strippedfrom the carbon with aconcentrated solutionof cyanide and causticsoda and plated onsteel wool by electrolysis. The final product atthe mine is a dore barcontaining approximately 80 percentgold. 19 percent silver.and 1 percent impuri-ties. The dore bars areshipped to a commercial refinery whichseparates the gold andsilver.

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Viceroy will reclaim thepreviously mined clay pits aspart of its comprehensive reclamation plan for the CastleMountain Mine. Approximately5 million tons (4.5 million metric tons) of overburden will bebackfiUed in the south clay pitto form four terraces. GrO


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Photo 3. Area disturbed by mining activity. shown before reclamation. Photo courtesy ofViceroy Resource Corporation.

Council. Desen Protection Council. andCitizens for Mojave National Park.Viceroy files an annual repon withSan Bernardino County and BLM summarizing revegetation programs conducted at the mine. The RRC meets at

least annually to discuss each repon andto make recommendations regarding theeffectiveness of the revegetation program.Recommendations prepared by the RRCand provided to Viceroy. the county.and BLM can fonn the basis lor changing revegetation techniques and performance standards. Flexibility offered bythis approach is critical to developingachievable performance standards foran area where success has not beendemonstrated.Plant Salvage Operations

Prior to mining. areas proposed forearly excavation were flagged for a plantsalvage program conducted by BLM.Seven species of cacti. three species ofyucca. and numerous species of nativeshrubs were included in the program.Salvage operations were conductedin lour stages. During the lirst stage.mining and reclamation groups. scientificorganizations. and botanical societieswere allowed to salvage plants duringa weekend. The following weekend wasdesignated for the public. Commercialnurseries were allowed to collect specimens over the third weekend.

BLM rangers. mine personnel. andvolunteers were on site 10 supervisethe salvage operation and provide assis'tance. Permits were issued by BLMfor plant salvage activities. Special permits required by the California DesenNative Plant Act were affixed to allplants before transit.

During the final stage of plant salvageoperations. Viceroy salvaged plants foruse in future on-site reclamation. A goalto transplant 25 percent of the barrelcactus and 25 percent of the Joshuatrees was established in the environmen'tal documentation lor the protect. Salvage operations began on March 23.1991.

Photo 4. Same area as Photo 3. shown after reclamation. Photo courtesy 01 ViceroyResource Corporallon.

Two companies specializing in thesalvage of desert plant material werecontracted to conduct the salvage opera'tion. Plant materials in the access road.leach pad. and pit areas proposed forearly excavation were salvaged first.A crew of 16 spent 2 weeks transplanting 10.625 plants. Larger specimenswere excavated using a tree spade whichremoves a ball of eanh with the roots.Mos! plants were salvaged using the bareroot method which is a more economicaltechnique. Bare root stock was dug witha mattock (bladed pick-axe).Two salvaged plant hokling areaswere prepared to receive the plant materials (cover photo). Separate holdingareas reduce the risk of an unforseen

ew:!nt. stich as a lire or disease. destroying all the salvaged plant material.

CALIFORNIA GEOlOGY NOVEMBER/DECEMBER 1992 '"s


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Before disrupting the plants each wasmarked with nontoxic paint to indicatenorth, because a cactus will sunburn iftransplanted with an orientation differentthan ils original. Roots were air-driedand lightly dusted with sulfur to preventdisease.The "post hole methoo" was used to

plant plants in one of the hok!ing areas.A hole large enough to accommodate thebase of the plant and its roots was dugand filled with VJater. The plant was positioned in the hole and soil was lightlytamped around the roots.An irrigation system was installed toprovide water to the plant nurseries.A 2-inch (5-


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Sedimentation in a HighlyErosive WatershedSalmon Creek, Humboldt County

OSCAR L. HUBEREngineering GeologistDivision of Mines and Geology

INTRODUCTIONThe evaluation 01 cumulative effects from haTvesting timberis a major concern for all State agencies that review TimberHarvesting Plans rn;ps), for timber landowners and forestersresponsible for managing the forest resources. and for localcitizens who wish to see that future land-use activities do nOIdamage the natural environment. During the past decade. par

ticular attention has been given to highly erosive watersheds inwhich timber harvesting has triggered landslides and soil erosion.and has resulted in the deposition of sediment and debris instream channels.Re


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, .. ..... ...- .. .' .....00"'''''' '"""" ... "0",,,,,. " . " " .. , , , . , '0'00' ,.,.,.,""'"0'" '. ~ , , , ." ." """N ~ l ~ ~ - " ' : ' , ' : ' . ' : ' : " ' ! . ' : : \ " ' : " " ' : . ~ ' ' : : ' ..' ' : ~ ' . ~'. - " - '..." EXPLANATION

(1 TranslationaVrotational slide-'tt) Earthtlowc'@ Debris slider Debris lIowltorrenl track,

Debris slide slopeActive slide (too small to delin-eate al this scale)

f . ~ , Disrupted ground.; ;1 Spring

Marsh

0,1 Artificial fill (Holocene) - - - - Lithologic contacta Alluvium (Holocene) .................. Thrust fault (barbs on upperOf Alluvial fan deposits (Holocene) plale)art River terrace deposits , ..._%- Fault(Holocene)omts Marine terrace deposits (Late -+- Anticlinal axisPleistocene) -I- Synclinal axisOh Hookton Formation (Middle to

Late Pleistocene) ~ Strike and dip of bedding, Volcanic ash Approximate strike and dipOTwu Wildcat group undifferenliated of bedding(Miocene-Late Pleistocene) ...\C'Ty Yager Formation (Tertiary) Strike and dip of fault as pro-jec ted from subsource dataFigure 2. Geology and geomorphic features related to landsliding in the Salmon Creek watershed. and locations of selected features discussed in the text. Modified from Kilbourne. 1985: Kilbourne and Momson. 1985; and Huber. 1991.

'" CALIFORNIA GEOLOGY NOVEMBER/DECEMBER 1992


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undifferentiated rocks of the Wildcat Group (upstream half ofthe timberlands). The Yager and Wildcat units are gently folded.with fold axes running east and west. Salmon Creek crosses theUttle Salmon Fault near the contact between Wildcat Grouprocks and alluvium (Kilboume and Morrison. 1985). The YagerFOlTTlation is composed of moderately hard to hard. yellowishbrown to gray sandstone. The Wildcat Group rocks are of soft.yellowish brown to bluish gray siltstone. claystone. and finesandstone. The alluvium and fan deposits are unconsolidatedsilts. sands. and gravels. which were derived by erosion andtransportation of Yager and Wildcat Group rocks.There are many landslides in Salmon Creek where it flowsover Wildcat Group rocks (Rgure 2) (Kilbourne and Morrison.1985). Conversely. few landslides exist where the stream chan

nel is in the Yager FOlTTlation. even where Wildcat Group rocksoverlie the Yager Fonnation (Kilboume, 1985). Differencesin the strength and durability of these bedrock units explaindifferences in slope stability along the stream channel. WhereWildcat Group rocks are exposed in the channel. erosion rapidlyremoves the toes of slopes. This destabilizes slopes which thenfail much more readily than in areas where the harder andstronger Yager FOlTTlation is exposed in the channel. Becauseof the weak and predominantly clayey to silty nature of theWildcat Group sedimentary rocks. most of the material thatenters the channel of Salmon Creek in the central portion ofthe drainage is fine-grained.

SALMON CREEK CHANNELIn the area examined. the stream channel is 15 to 30 feet

(5 to 9 m) wide and 8 to 15 feet (2 to 5 m) deep, with steep(50 percent to 80 percent) side slopes. The stream gradientranges from 2.7 percent to 3. 5 percent and the channel consists of shallow pools and riffles with no significant waterfalls orrapids. At the lime of inspection. the riffles were 6to 12 inches(15 to 30 cm) deep and about 10 feet (3 m) wide. Pools were2 to 3 feet (60 to 90 em) deep.Average nows for the months of May. June. and July are

8.1. 3.2. and 0.9 cubic feet per second (cfs) (0.22. 0.09.0.03 ems). respectively. The average flow for February is54.5 cfs 0.5 cms) (U.S. Department of the Interior. Rsh andWildlife Service, 1987). The peak now for major storms wouldbe significantiy greater than the average February now. As withother coastal streams in California. most of the sediment transportation and channel erosion occur dUring infrequent. shortduration. high stOITTl nows.Streambank erosion is evident at every bend in the channeland at the toes of all the larger slides. At some locations. bare,eroding. undercut. nearly vertical banks are more than 40 feet(12 m) high. All of the rock outcrops in the downstream halfof the forested portion of the watershed are composed of soft.gray to yellowish brown siltstone and fine sandstone of the Wild-cat Group (Photo 1). These rocks are easily broken by hand.and erosion of the rock produces silt and sand with no durablegravel component. Sediments in the active stream channel are amixture of sill. fine sand. and gravel. The gravel is composed ofwell rounded fragments of hard sandstone. most of which are

smaller than 8 inches (20 cm) in diameter. but some are aslarge as 12 inches (30 cm). The hard sandstone gravel wasderived from the Yager Formation. exposed several miles fartherupstream. and was transported to the lower reaches of the watercourse. probably dUring high stOITTl nows.Throughout the middle portion of the watershed. the gravels

in the riffles are embedded in fine sediment and the pools arepartly filled with fine sand and sill. Along inside bends and adjacent to toes of slides. fine sediment covers. or partly covers. thegravel in the riffles. The in-stream sediment appears to be quitethin (2 to 4 feet or about 1 m). except where trapped behindobstructions in th channel. where it locally reaches thicknessesof 20 feet (6 m) or more. Remnants of previously trapped sediment are present as terrace deposits adjacent to the channel.Most of the terrace deposits are poorly stratified silt. with largeamounts of embedded wood.LANDSLIDES

The aerial photographs document that most of the largelandslides adjacent to Salmon Creek, within the central portionof the watershed. were present prior to 1940. However. theaerial photographs also indicate that most of these landslidesbecame larger during and after the timber harvesting operationsbetween 1940 and 1960. and that some landslides were probably initiated by the construction of roads and skid roads.The landslide at point 1 (Rgure 2) is among the largest activelandslides on Salmon Creek. The aerial photographs indicatesliding began prior to 1940 and that repeated movement has

occurred, as evidenced on 1972. 1981. and 1988 photos. Treesand stumps in the area around the slide indicate there have been

Photo 1. Typical exposure of soft Siltstone bedrock in theSalmon Creek channel. The siltstone is pan of the undilter-entiated Wildcat Group. Photo by OscarHuber. June 1,. 1992.

CALIFORNIA GEOLOGY NOVEMBER/DECEMBER 1992'"


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tw o cycles of logging there (about 1900 and 1%0). At present.the slide includes numerous scarps up to 6 feet (2 m) high. Itssurface is mostly revegetated and appears to be relatively stable.Previous stream surveys reported the presence of logjams. mud.and debris at this location (Bugbee and others. 1964: Trzeciak.1984). but none VJere observed during this study.The landslide at point 2 on Figure 2 is also very large andactive. The air photos indicate that it moved prior to 1940.The photos taken in 1954 and thereafter indicate periodicmovemenl. Trees and stumps on the slope adjacent to the slideindicate the (irst cycle of logging occurred here in the early1940s. Debris at the toe of this slide presently fiUs the streamchannel for about 500 feet (I 50 m). wilh an average depthof about 15 feet (5 m) (Photo 2). This debris is composed ofJogs. soil. and blocks of siltstone. The stream has establisheda route over and through this feature and formed a large pondupstream. For several hundred feet downstream. the channel islocally aggraded with sediment and other material from the slide.This landslide is a constant source of fine sediment.

L OGJAMS AND IN-STREAM SEDIMENTConditions of Salmon Creek prior to the beginning ofroad construction and timber harvesting are unknown. However. the geomorphic processes of channel erosion and streambank undercutting were probably operating in a manner similar

10 those observed today. 11le processes that fonn logjams wereactive so some logiarns were almost certainly present. Throughout the last few thousands of years. major earthquakes or stonnsundoubtedly triggered landslides that deposited many fallen treesin the stream channel.Interpretation of the various aerial photographs indicatesthat unregulated road construction and logging practices 30 to

50 years ago increased Jandsliding and erosion. and probablycreated logjams. The 1954 photos show the stream channelfilled with sediment for about a mile (600 m) upstream of a l0g-jam at point 4 (Rgure 2). For about 650 feet (190 m) upstreamfrom the logjam there is no surface flow of water evident onthe photographs.The 1962 photographs show a logjam 600 feet (180 m)downstream from point 4. Sediment filled the channel forabout 4.200 feet (1.280 m) upstream. The 1972 photographsindicate this logjam no longer dammed the stream. which hadcut through the sediments behind the jam. By 1981 vegeta1ionobscured most of the remnants of these deposits (Huber. 19911.11le 1964 stonn. the largest on record for the north coastof California. undoubtedly played a role in removing logjamsand sediment in the Salmon Creek channel. Also. many logjams were removed prior to the mid-1970s to control erosion.salvage Jogs. and/or allow fish migration (McConnick. 1955;GaryGiannandrea. timber operator. oral communication.1991). Recent investigations indicate thaI large VJOOdy debrisis now rare in the Salmon Creek channel.Prior to the initiation of stream clearance VJOrk conducted inthe early 1970s. pools between riffles in Salmon Creek VJere

probably deeper than at present because more logs woukI produce more plunge-pools. Even so. the highly erodible nature ofthe Wildcat Group sedimentary rocks and the occurrence ofmajor stonns and earthquakes in the area suggest thatlhe poolsand gravels VJere frequently filled with fine sediment. similar tothe present conditions.EFFECTS OF TIMBER HARVESTING

Unregulated timber harvesting activities between 1940and 1960 caused changes in slope stability and erosion. andprobably in stream conditions in Salmon Creek. Common Jogging practices in California at that time included skidding logsin stream channels. sidecasting earth into streams during roadconstruction. removing or burning stream canopy vegetation.and tractor harvesting on steep slopes. However. many of theseeffects on the slopes appear to have recovered by vegetativeregrourth and geomorphic processes. In addition. the passage01 the Z'Berg-Ne;ed1y Forest Practice Act of 1973 restrictedthe limber harvest practices that probably caused the greatestimpacts to the stream system. Slope stability is no w a majorconsideration during road design. trees on Sleep slopes areroutinely haJVeSled with cable yarders instead of tractors. erosionmust be kept to a minimum. and stream canopy vegetation mustbe protected. In addition. erosion problems caused by pastharvesting are often mitigated in current n-trs.

Even though logging practices have improved and there arenow strict regulations gO'v'elTling them. slope stability and erosionrisks associated with timber harvesting remain. Those risks areevaluated during the review of proposed n-trs. and specialmitigation may be imposed. In the case of Salmon Creek. proposed timber harvesting may cause increases in the erosionof line-grained sediment from slopes or increases in the occurrence of landslides. For this reason. THPs in the Salmon Creekwatershed are