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HomeMy WebLinkAboutAGENDA REPORT 1996 1218 CC REG ITEM 07CAGENDA REPORT CITY OF MOORPARK TO: The Honorable City Council FROM: Nelson Miller, Director of Community Development DATE: December 11, 1996 (For the City Council Meeting of December 18, 1996) SUBJECT: State Mining and Geology Board Draft Guidelines for Evaluating and Mitigating Seismic Hazards and Preliminary Seismic Hazards Maps Relating to Liquefaction and Earthquake- Induced Landslides Attached is a letter and bulletin from the State Division of Mines and Geology which briefly describes the draft guidelines and maps relating to the seismic hazard review and mapping. A reduced copy of the Simi Valley West Quadrangle map, which affects Moorpark, is also attached. This is one of only six maps which have been currently released. It covers Moorpark, approximately east of Spring Road. Maps covering the rest of the City have not yet been prepared. The draft guidelines and maps were prepared by the state in accordance with legislation which was adopted subsequent to the Northridge earthquake, in order to reduce and mitigate earthquake hazards. They have been released for a ninety day comment period, which ends January 7, 1997. DISCUSSION We have discussed the guidelines and map with representatives of Bing Yen & Associates, Inc., the City's geotechnical consultant. They have indicated that the City is already reviewing projects in a manner largely consistent with the proposed guidelines. They also did not have major concerns regarding the preliminary map. They do have a few technical concerns regarding the guidelines which they are preparing for the City of Malibu, for whom they also consult. The State intends to adopt the guidelines and map in the Spring. Following adoption these guidelines would be required. The guidelines and maps would also be required to be considered in any updates of the General Plan Land Use or Safety Elements and any changes in ordinances. The areas mapped would also be considered mapped hazard zones which would be used by the insurance companies in determining risk and rates and would be required to be disclosed as part of any real estate transaction. ' �_l Wo I D10 1X 19 Receive and file this report. Attachments: Letter and Bulletin #1 Seismic Hazard Zone Map /,(z _ 7 C. \OFFICE \W P WIN\ WPDOCS \CCRPTS \SEISMCHZ- WPD (WU25 STATE OF CALIFORNIA - THE RESOURCES AGENCY PETE WILSON Govemor DEPARTMENT OF CONSERVATION DIVISION OF MINES AND GEOLOGY HEADQUARTERS 801 K Street, MS 12 -30 Sacramento, CA 95814 -3530 Phone: 1. (916) 324 -1825 FAX: (916) 445 -5718 To: City Managers RF�E�VF� October�� CE �F Ty Ci,T h' 4� 1 Grp The purpose of the Seismic Hazard Mapping Act is to reduce and mitigate earthquake hazards in order to protect public health and safety. Responsible agencies affected by the regulatory zones must regulate specified "projects" within the zones in order to identify and mitigate seismic hazards. I am pleased to announce the release of six (6) Preliminary Review Maps of Proposed Seismic Hazard Zones for public comment. These maps, addressing the hazards of liquefaction and earthquake - induced landslides, were developed pursuant to the Seismic Hazard Mapping Act (Division 2, Chapter 7.8, California Public Resources Code (PRC)). These maps are issued in addition to, and do not replace, any existing Alquist- Priolo Earthquake Fault Zone maps that may cover the same area. The enclosed index map identifies the maps released. A color copy of each Preliminary Seismic Hazard Zone Map affecting your jurisdiction is enclosed for your immediate review. You will recall that our staff recently met with you and/or your staff to show you each map and to discuss the requirements of the Act. Please check the zone and map boundaries to determine whether you have received the correct map(s). The Seismic Hazards Mapping Act (SHM Act) requires the State Geologist to compile and issue maps identifying seismic hazard zones, and to submit the maps to all affected cities, counties, and state agencies for review and comment. Concerned jurisdictions and agencies must submit all comments to the State Mining and Geology Board (SMGB) for review and consideration within 90 days. (See enclosed SMGB information.) Within 90 days of the closure of the comment period, the revised maps will be issued as Official Maps of Seismic Hazard Zones. Cities and counties affected by the official zones must require a geotechnical (hazards) investigation report for each subdivision and most structures that qualify as projects under the Act. They must submit copies of these reports to the State Geologist after they have been approved (PRC Section 2697) by the local government. California Code of Regulations (CCR) Section 3724 outlines specific criteria for project approval. Additional guidance regarding the responsibilities of cities, counties, and state agencies, and guidelines for evaluating and mitigating seismic hazards have been developed by the State Mining and Geology Board as required by PRC Section 2695. Those draft guidelines are also enclosed for your review and comment. These maps were prepared using techniques recommended by the Seismic Hazard Mapping Act Advisory Committee and the State Mining and Geology Board. To define liquefaction hazard zones, basic geologic and detailed subsurface information was used in O}WZ(S City Managers October 4, 1996 _Page combination with historic high water table data and the estimation of the maximum earthquake ground shaking likely to occur at alllocations shown on the maps in the next 50 years. The earthquake- induced landslide hazard zones were delineated using a modified Newmark analysis that incorporated geologic and rock - strength data and estimates of ground shaking associated with future earthquakes. The extent of the liquefaction and landsliding hazards in each zone is not uniform. The purpose of establishing these zones is to include areas within which soil conditions, topography, and the likelihood of future ground shaking indicate sufficient hazard potential to justify a geotechnical (hazards) investigation of the individual characteristics of specific project sites before land -use permits are granted. This process enables local government to stipulate appropriate conditional requirements for the design and/or construction that can mitigate future earthquake losses. In developed regions, the zone maps delineating areas where geologic studies are required should not be used to infer that all existing construction within the zone boundaries is hazardous. The properties of local soil conditions and the characteristics of individual buildings are too variable for such regional conclusions about overall vulnerability to be justified or appropriate. Please also note that within five days of receipt of the Official Maps, counties are required to post a notice at specified locations (county recorder, county assessor, and county planning commission) announcing their availability (PRC Section 2696(c)). The California Department of Conservation has established a World Wide Web site (http: /lwww.consrv.ca.govn to aid in disseminating information about this and other programs. On the Seismic Hazard Mapping Program Home Page ( http: //www.consrv.ca.gov /dmg /shezp /) you will find links to articles that describe the program and the hazards being addressed, copies of draft guidelines (once they are released), and ways to obtain copies of the maps and other products. If you need additional information, please contact Ted Smith, Local Government Outreach Coordinator for Seismic Hazard Mapping, at (916) 323 -8569 (e -mail: tsmith @consrv.ca.gov) or Bea McKamey at (916) 324 -1407 (e -mail: bmckamey @consrv.ca.gov). Sincerely, James 'r Davis State Geologist Enclosures Draft Guidelines Availability of Seismic Hazard Zone Maps Seismic Hazard Mapping Maps Seismic Hazard Mapping Bulletin Qwfjz? seis0 mic ffazalw Mapping Bulletin #I Department of Conservation Division of Mines and Geology 801 K Street, MS 12-31 Sacramento, CA 95814 Seismic Hazard Zone Maps Released fState Department of onservation's Division of ines and Geology has leased six preliminary ismic Hazard Zone Maps, the first in a series. Five of the maps were prepared with funding from the Federal Emergency Management Agency and the Governor's Office of Emergency Services. Thirty-three more maps will be completed for portions of Ventura, Los Angeles and Orange counties over the next two years. On October 8, 1996, the six prelim- inary maps were distributed to all California cities and counties and to affected state and federal agencies, beginning a 90 -day review and comment period. At the same time the State Mining and Geology Board released draft implementation guide- lines for a 90 -day review. The Legislature passed the Seismic Hazard Mapping Act in 1990 (AB 3897; Public Resources Code, Chapter 7.8, Sections 2690 - 2699.6), directing the Division of Mines and Geology to prepare the maps. The purpose of the Act is to reduce threat to public health and safety and to minimise economic loss due to seismic hazards. The Act directs cities, counties and state agencies to use the maps in their land use planning and permitting processes. A site - specific geotechni- cal report is required prior to permit- ting most urban developments within the zones. The Act also requires sellers of real property (or their agents) within the zones to disclose this fact to potential buyers. The guidelines will aid local agencies in establishing land use management policies and ordinances to reduce and mitigate losses from IAP ground failure during earthquakes. The maps and guidelines may also be useful to insurance companies, con- sultants, investors and the public. A twelve - member advisory committee Condnaed on page 4 /3 114 116 Preliminary 10+°$196 (St2 San Francisco North g Official Maps 3!1197 western Oakland West not shown) Preliminary 411197 Official Maps 1011197 aAno 1 San Francisco 8 Calabasas North and Treas- 9 Canoga Park ure Island portion 10 Van Nuys of Oakland West 11 Burbank 12 Newhall 12 Pena 3 Mint Canyon 13 Mount Wilson 4 Simi Valley West 14 Azusa 5 Simi Valley East 15 Glendora 6 Oat Mountain 16 Topanga 7 San Fernando 17 Beverly Hills 29 Redondo Beach 18 Hollywood Preliminary 111198 Official Maps 711198 19 Los Angeles 30 Torrance 20 El Monte 31 Long Beach 21 Baldwin Park 32 Los Alamitos 22 San Dimas 33 Anaheim - " 23 Venice 34 Newport Beach 24 Inglewood 35 San Pedro 25 Southgate 38 Seal Beach 26 Whittier 37 Newport Beach 27 La Habra 38 Tustin 28 Yorba Linda 39 Laguna Beach 29 Redondo Beach Seismic Hazard Zone Maps Represent State -of -the -Art Technology he California Department of Conservation's Division of Mines and Geology, is working with state -of -the -art technology, identifying and mapping the state's most prominent earthquake hazards. The Department's geologists will ultimately chart areas prone to liquefaction (failure of water - saturated soil) and earthquake - induced landslides throughout the state's principal urban and major growth areas (see figure opposite). The official maps produced by the Seismic Hazard Mapping Program are mandated by the Seismic Hazard Map- ping Act of 1990 to be used by cities and counties to regulate development within identified seismic hazards. Local governments, at their discretion, can withhold development permits until geologic or soils investigations are conducted and mitigation measures are incorporated into project plans. UNIQUE ASPECTS Previously, seismic hazard maps may have been done by local governments or other parties in selected areas or for special purposes. The official Seismic Hazard Zone Maps are different in three key aspects: ♦ First, the Division scientists inte- grate the very latest geotechnical data available with state -of -the -art computer technology to produce the maps. The information is the most up-to -date possible at the time of production. ♦ The Department uses a standardized method of hazard assessment to evaluate hazard potential consis- tently for the entire state. Other mappers have applied their own criteria for assessing hazards in the smaller study areas. Viewed together, these maps would show a patchwork -quilt view of the region as a whole. It is this standardized look at the hazards that make these official maps particularly valuable. ♦ These are the first seismic hazard maps to use a scale (1:24,000) large enough to provide a detailed look at a large region. Based on existing U.S. Geological Survey topo- graphic quadrangle maps, each map covers an area approximately 60 square miles in size. Most cur- rently available maps are at a much smaller scale of 1:100,000. PRODUCTION PROCESS The maps are the result of detailed data analyses by the Division's geolo- gists and seismologists. The experts examine the latest information about surface and subsurface geology, historic groundwater levels and damage and geologic effects resulting from the Northridge and other earthquakes throughout California. With a state -of- the -art seismic hazard mapping system, the data are integrated into a three - dimensional view of the ground. Capabilities of the seismic hazard mapping system include, but extend beyond those of a conventional geo- graphic information system. in addition to having the capability to store and manipulate large volumes of spatial data, the system permits subsurface geological analysis, photo- grammetry and remote sensing analysis, including stereoscopic display of aerial images of the land for interactive analysis of the surface geology and topography of the landscape. Division geoscientists in Sacra- mento, Los Angeles, and San Francisc are linked by a high -speed wide -area network with all the essential analysis tools for seismic hazard zone delinea- tion at the desktop. Time required for complex tasks, such as mapping of existing land - slides over large areas, have been reduced from months to weeks using this system. Seismic hazard zone map informa- tion will be made available in several formats, including the Spatial Data Transfer Standard (FIPS 173), for use on a local geographic information system. FUNDING The Seismic Hazard Mapping Program was originally funded by the California Residential Earthquake Recovery Fund and a portion of local building permit fees. In the early 90s, however, funding for the program was greatly reduced when the recession slowed construction and the Earth- quake Recovery Fund was cancelled. The Department of Conservation was able to continue the program with federal disaster relief funds from the Federal Emergency Management Agency, through the Governor's Offic of Emergency Services. As much as $15 million has been earmarked for seismic hazard mapping in Southern California counties affected by the 1994 Northridge earthquake. 4141. .04. ee OWW! Seismic Hazard Mapping Geographic Priorities W r� t S Maps to be released over the next two years are shown in black. The current release includes San Francisco North and the -' — Treasure Island portion of Oakland West, Topanga, Simi Valley East, Simi Valley West, Anaheim, and Newport Beach quadrangles. Maps scheduled for release in 1997 and 1998 are shown on front cover. Remaining areas shown identrfy possible future work, depending on availability of funding. ()WW U CoMbured from page l assisted the Board in developing the draft guidelines. The maps identify areas where soil liquefaction and earthquake - induced landslides are most likely to occur. The Liquefaction Hazard Zones are areas underlain by satur- ated sands and silts deposited during the last 10,000 years. The Landslide Hazard Zones are areas, generally steep hillslopes composed of weak materials, where earthquakes are likely to trigger landslides, rockfalls, and other slope failures.. The proposed hazard zones were delineated by highly - skilled staff using state -of- the -art computer technology to compile geologic data from local government agency files and other appropriate sources. The data include basic geologic mapping by state and federal geologists, historic records, and topographic data. Interpretation of the data leads to identification of areas known to have experienced landslides or liquefaction during historic (last 250 years) earthquakes, or where conditions indicate that these hazards are likely to occur in the future. Following the review period, the maps and guidelines will be revised in response to comments received. The State Mining and Geology Board plans to adopt the guidelines no later than March 1 unless revisions are extensive. About the same time, the State Geologist will issue official versions of the first six maps. The deadline for submitting comments on both the maps and guidelines is January 7, 1997. Copies of the maps are available as blue -line prints for the cost of reproduction from: BPS Reprographic Services 149 Second Street San Francisco, CA 94103 (415) 495 -8700 ext. 550 ,lint Clock IPAO% Frequently Asked Questions abort ear*quake hazards and the Seismic Hazard Mapping Act Q. What hazards do the maps show? A. The maps show areas that have potential for landslide and liquefaction hazards. Q. What is liquefaction? A. During an earthquake saturated sandy and silty soils may "liquefy. " The soils 'fail" to support buildings, which can sustain severe damage unless the hazard is recognized and mitigated Q. How are these maps different from the maps released last February? A. Although these maps partly cover the same areas as the "reconnaissance " maps released in early February, they are based on additional data thus they are much more detailed and accurate than the earlier maps. Q. What are the responsibilities of the cities and counties? Are they required to enact an ordinance? A. The Act leaves the implementation procedures to the discretion of local governments. The State Mining or Universal Reprographics, Inc. 2076 Wilshire Blvd. Los Angeles, CA 90057 (213) 365 -7750 Reduced -size versions of the maps and copies of the draft guidelines are available through the Department of Conservation's home page at: http://www.consrv.ca.gov/. To purchase copies of the draft guidelines or for assistance with map and guideline interpretation, contact the Department of Conservation at one of these locations: Los Angeles (213) 620- 3560; Sacramento (916) 445 -5716; San Francisco (415) 9047707; or email: tsmith @consrv.ca.gov. Please send comments on the maps and/or guidelines to: State Mining and Geology Board 801 K Street, MS 24 -05 Sacramento, CA 95814 10464. and Geology Board has drafted guidelines to assist in local implementation Some cities may want to enact an ordinance; others may rely on CEQA and the planning process, or their own permit review procedures. Q. Does the Seismic Hazard Act apply to all development? A. No. The Act is directed at mitigating hazards to new structures for human occupancy, though some smaller developments may be exempt. Cities and counties may have more restrictive requirements. Q. How can I find out about earthquake hazards on my property? A. Copies of the maps can be purchased from BPS Repro - graphic Services and Universal Graphics. The addresses are provided above. Many cities and counties may make copies available for viewing in their offices. Q. When the next earthquake occurs will the entire area_ shown on the maps be devastated? A. The maps show areas that are prone to landslides and liquefaction This does not mean that the area will be uniformly affected during an earthquake, nor that s outside the zone will be unaffected (�,(�(t 'I I � 118 523C ¢� 9ase IAOp e1e-1d b1 U S Geological Survey, 1951, pbl {prev -sac !96Y J ,rt r. 0 OLTE S.aaKw 16,1Ne IMPOWANT - PLEASE NOTE ems` xrr �� lemnld na •Does ell u.0 Net hew t4a pas tW for 4'queaafon, Uap .vM4ueks WdoOltrW Waaro •f1eN/m IXDN•r••Iplgpeka Md �• /0euprlp i ; �✓r¢7' .s. - _-�� —_ _; . 2J o 4uf of Hand Z. w -y "D c w, Arede eu a ptia. to fha epecte ntly dip �N.a et� nNrthe the f ro ekwp •D•un beret.. a now Duna areae, 31 eie map ears Daenow agwaf -Prm/D Y ec'uin Mb Plw. rearm pre aa•f == DfE ;; t"" Fedr zones fa aecro.ure, STATE OF CALIFORNIA SEISMIC t end Dtbu.IX(pde pletM requll•tl by p!• Alquish .'rlWd fgnhquek. Feup Zonlnp Att HAZARD ZONES dl rendelDa Cewwr AJ, pivlden i dz hoard mgoe pvp•r.d oy p1e U.& ir!q,ppW aWe4a � tl &rvN a2. of M. nmae q.wun;.. uoa. /•.faMS NeruW MWNrN AN ° " meDe, ha us c.uDp �aawrmewn: "" `dd' desfpnad to epXae ro'.v msppda ro ecssla .qql queksdldepd ar!ddp• h•rarde. SIMI VALLEY WEST QUADRANGLE 5' The man'rpnon e d to aebn Dfn wf . be a ° vvieDrs a iinia�:V`e "p° ul °' °ee eiaed dyarae PRELIMINARY REVIEW MAP m • mruml. non dspbfed n 9 been tlnwn " Released: October 1 es POs lb f Iha map .tale 1 1996 B 11 On ( I .p 1 not suU�canf f0 prve aE a eubsf lure !Or fne 9111. p, - M Ital '! � Inv.aUpetbn. rsqulre0 urMU Chapters ).° yr0 B '' °^ 2 Ip el'bmra PUDIIO Reaourese Code. MFj s war'. %; J:SC;,;IV.Eq: Tne Sle.'e of Celifomi. end UN O epuLll•DI01 COnaervdtion 'n,:ke n0 rep'epn.'at:Me 9fi K Sp.e1, NS 26-� S.venvm G �< CAAIMEM UEaDtJhF,y Or lvanentlN r. udl Ivmm rmlch Nap maps vnre dsdwtl. N wW�• emurcy da o/pM te he'; oe IaSie under z ury ircumsWpe W etly dl—t lnd�, aefUnant Inc•de ^M; or eanse4u n!al demepee vAN rp � - ..i..' party on eccoun! l or arielny M1 �huNSe Ot thls r� user • { Y saf ft� �� #� raw .- '."}Yi6��,Y ¢%F,��6g' •� t° l.�j@'1v t'-�l �r5'd YY' fix I ! k: +[ i .A � .+/. 1( �r .�lr`.� l�`' ✓ 4� / ./: � g: �� ° _. �, � y '• �"g,�yy} � 6R,�� 6 ill � �/: v%J/ ' yd/ viii' � �, � "���1 � I d� � ..f.� (�'�v� �r �'�•Ttl►' ,tom e4p l 6 1 C A > A^ tom.. �p,_i!.V�� ,•.a.F: •- FA I � 118 523C ¢� 9ase IAOp e1e-1d b1 U S Geological Survey, 1951, pbl {prev -sac !96Y J ,rt r. 0 OLTE S.aaKw 16,1Ne IMPOWANT - PLEASE NOTE ems` xrr �� lemnld na •Does ell u.0 Net hew t4a pas tW for 4'queaafon, Uap .vM4ueks WdoOltrW Waaro •f1eN/m IXDN•r••Iplgpeka Md �• /0euprlp �, p llgw7 cfbn r Ulm lendslldolell��lwlll ormd eNea pq udk• erM oorrW .s. - _-�� —_ _; . 2J o 4uf of Hand Z. w -y "D c w, Arede eu a ptia. to fha epecte ntly dip �N.a et� nNrthe the f ro ekwp •D•un beret.. a now Duna areae, 31 eie map ears Daenow agwaf -Prm/D Y ec'uin Mb Plw. rearm pre aa•f == DfE ;; t"" Fedr zones fa aecro.ure, STATE OF CALIFORNIA SEISMIC t end Dtbu.IX(pde pletM requll•tl by p!• Alquish .'rlWd fgnhquek. Feup Zonlnp Att HAZARD ZONES dl rendelDa Cewwr AJ, pivlden i dz hoard mgoe pvp•r.d oy p1e U.& ir!q,ppW aWe4a � tl &rvN a2. of M. nmae q.wun;.. uoa. /•.faMS NeruW MWNrN AN ° " meDe, ha us c.uDp �aawrmewn: "" `dd' desfpnad to epXae ro'.v msppda ro ecssla .qql queksdldepd ar!ddp• h•rarde. SIMI VALLEY WEST QUADRANGLE 5' The man'rpnon e d to aebn Dfn wf . be a ° vvieDrs a iinia�:V`e "p° ul °' °ee eiaed dyarae PRELIMINARY REVIEW MAP m • mruml. non dspbfed n 9 been tlnwn " Released: October 1 es POs lb f Iha map .tale 1 1996 B 11 On ( I .p 1 not suU�canf f0 prve aE a eubsf lure !Or fne 9111. p, - M Ital '! � Inv.aUpetbn. rsqulre0 urMU Chapters ).° yr0 B '' °^ 2 Ip el'bmra PUDIIO Reaourese Code. MFj s war'. %; J:SC;,;IV.Eq: Tne Sle.'e of Celifomi. end UN O epuLll•DI01 COnaervdtion 'n,:ke n0 rep'epn.'at:Me 9fi K Sp.e1, NS 26-� S.venvm G �< CAAIMEM UEaDtJhF,y Or lvanentlN r. udl Ivmm rmlch Nap maps vnre dsdwtl. N wW�• emurcy da o/pM te he'; oe IaSie under z ury ircumsWpe W etly dl—t lnd�, aefUnant Inc•de ^M; or eanse4u n!al demepee vAN rp � - ..i..' party on eccoun! l or arielny M1 �huNSe Ot thls r� user 34.15' 118- 45' c t� MAP EXPLANATION Llq..f..d.. N—d Zones Ares Mess Nmb a.wnrrpe dlbyy.cppn. a balp.do�l pea.dwpdend pmeld xafu awlralare L,� a poaM ku' Neepaos Cad• S.dWr �M� bs+aYO �d.M1Ntl h E.dkgwk. -Md.. Le-Yid. NSS*M Z• ODl—Sp rasurtu,o. darpeltle nnwtflent akaal elope �dko a Wl.td. kr psrrnYdN "de S *C apaorrwds wld Memel aro d.hNtl H PWIb A.sauDn Code Sedbn Z9p3(D) woultl ba r REFERENCES USED TO COMPILE THIS MAP SM WYry Iyw D-p 4 r 034 e.mm.vevuo�� .:. ..fie au r�v. cln.n o ua h� - fie hnu�+eriiz WrouemYal wo �bpr tuuauw Wmum er�uu,.en a ow. evm mt xa u fral�•m�m��v.u� �'u °A1 +'wmu�la�a a�io �