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2006-395 CN/G C I T Y OF E N C I N I T A S ENGINEERING SERVICES DEPARTMENT 505 S . VULCAN AVE. 10$svw ENCINITAS, CA 92024 GRADING PERMIT PERMIT NO. : 395GI PARCEL NO. 258-073-4300 PLAN NO. : JOB SITE ADDRESS : 520 FOURTH ST. CASE NO. : 06229 / CDP APPLICANT NAME GEIRMAN (WILLIAM) MAILING ADDRESS : 520 FOURTH ST. PHONE NO. : 760-815-5096 CITY: ENCINITAS STATE: CA ZIP: 92024- CONTRACTOR : PANETTI CONSTRUCTION CO. INC. PHONE NO. : 760-801-7326 LICENSE NO. : 799482 LICENSE TYPE: C8 ENGINEER : LINTVEDT, MCCOLL AND ASSOCIATES PHONE NO. : 619-294-4440 PERMIT ISSUE DATE: 9/28/07 PERMIT EXP. D 9/28/08 PERMIT ISSUED BY: �� INSPECTOR: N BRADY ----- --- ---- -- -- -- ---- -- PERMIT FEES & DEPOSITS ---------------------------- 1 . PERMIT FEE . 00 2 . GIS MAP FEE . 00 3 . INSPECTION FEE 792 . 00 4 . INSPECTION DEPOSIT: . 00 5 . NPDES INSPT FEE 158 . 00 6 . SECURITY DEPOSIT . 00 7 . FLOOD CONTROL FEE . 00 8 . TRAFFIC FEE . 00 9 . IN-LIEU UNDERGRND . 00 10 . IN-LIEU IMPROVMT . 00 ll . PLAN CHECK FEE . 00 12 . PLAN CHECK DEPOSIT: . 00 ------------------------ - DESCRIPTION OF WORK --- ------------ - - -- - ----------- PERMIT TO GUARANTEE BOTH PERFORMANCE AND LABOR/MATERIALS FOR EARTHWORK, DRAINAGE, PRIVATE IMPROVEMENTS AND EROSION CONTROL PER APPROVED GRADING PLAN 395-G. CONTRACTOR SHALL MAINTAIN TRAFFIC CONTROL AT ALL TIMES PER APPROVED TRAFFIC CONTROL PLAN OR PER WATCH STDS . LETTER DATED JUNE 7, 2007 APPLIES . ---- INSPECTION ---------------- DATE ----- --- INSPECTOR' S SIGNATURE ---- INITIAL INSPECTION COMPACTION REPORT RECEIVED ENGINEER CERT. RECEIVED ROUGH GRADING INSPECTION FINAL INSPECTION ----------------------------------------------------------------- -------------- I HEREBY ACKNOWLEDGE THAT I HAVE READ THE APPLICATION AND STATE THAT THE INFORMATION IS CORRECT AND AGREE TO COMPLY WITH ALL CITY ORDINANCES AND STATE LAWS REGULATING EXCAVATING AND GRADING, AND THE PROVISIONS AND CONDITIONS OF ANY PERMIT ISSUED PURSUANT TO THIS APPLICATION. 9 - 2 -7 SIGNATURE DATE SIGNED Lcy,// C 6 'c/co-t,,.vy 7,�ra $/jr PRINT NAME TELEPHONE NUMBER CIRCLE ONE: 1 . OWNER) 2 . AGENT 3 . OTHER Li Er 7 , s Lj RESPONSE TO THIRD PARTY REVIEW COMMENTS 520 4T"STREET, ENCINITAS SAN DIEGO COUNTY, CALIFORNIA FOR MR.BILL GEIERMAN 520 4T"STREET ENCINITAS,CALIFORNIA 92024 W.O.4799-A=SC JULY 6,2006 s, . Geotechnical • Coastal • Geologic • Environmental 5741 Palmer Way Carlsbad, California 92008 • (760) 438-3155 • FAX (760) 931-0915 July 6, 2006 W.O. 4799-A-SC Mr. Bill Geierman 520 4h Street Encinitas, California 92024 Subject: Response to Third Parry Review Comments, 520 4"' Street, Encinitas, San Diego County, California References: 1."Third Party Review,520 a Street,Encinitas,APN:258-073-43/Applicant: Bill Geierman," No. Case No., dated June 3, 2006, by Geopacifica. 2."Revised Preliminary Geotechnical Evaluation,520 e Street,Encinitas,San Diego County, California,"W.O. 4799-A-SC, dated November 29,2005, by GeoSoils, Inc. Dear Mr. Geierman: In accordance with your request, GeoSoils, Inc. (GSI) has reviewed the comments prepared by Geopacifica,for the City of Encinitas. Based on our review, including a review of field conditions, and a review of our referenced report (see Reference No. 2), the following comments are offered. For convenience, review comments prepared by Geopacifica are repeated below in bold print. REVIEW COMMENTS AND RESPONSES Review Comment No. 1 "Document 1 indicates it is a revised report. Please provide a copy of the original report for our review." Response to Review Comment No. 1 Our initial report,dated August 5,2005,was revised,and re-issued on November 29,2005. The revised report (see Reference No. 2) contains the findings of the initial report plus revisions based on the currently proposed work, and is the applicable and appropriate report for this site. The initial report, dated August 5, 2005, is not considered valid, and/or applicable to the proposed work at the subject site,and should not be used in design. The revised report is specific to the proposed work,and is generally considered within current standards of practice. Thus, this outdated report is of no geotechnical benefit to the reviewer, and is not necessary for a review of the current report. Review Comment No. 2 "Document 1 indicates a `deep' boring was made for the project. The log of boring provided is to 30 feet only and was more than 170 feet east of the bluff top. The bluff top in the area is more than 65 feet in height. Please provide the log of boring for the height of the bluff plus 10 feet. Please provide the log of boring made on the site and/or adjacent to the bluff top." Response to Review Comment No. 2 As shown in Appendix B of the referenced report, Boring B-1 was completed to a depth of approximately 52 feet below grade,and encountered the underlying Eocene-age bedrock (Torrey Formation) at an approximate depth of 50 feet, or 16 feet Mean Sea Level (MSL). Mapping of the sea cliff/bluff slope, west of the boring, indicated similar geologic conditions to those encountered within the boring, including the location of the terrace deposit/Torrey Formation un-conformity, at an approximately elevation of 19 feet. Based on our experience in the vicinity,and information presented in other published documents (US Army Corp of Engineers [USACOEj, 1996), bedrock conditions within 10 feet (below), and exposures at low tides when bedrock exposed, indicate conditions at the toe of slope are similar to those observed at the face of the sea cliff (Torrey sandstone), and encountered within the boring below 50 feet. A log of the boring is also presented in Appendix B, herein. Review Comment No. 3 "Certain references for the project (Appendix A of document 1) do not appear to be applicable to the project and others that might be applicable are not on the list. Please provide references applicable for the project site." Response to Comment No. 3 A revised reference list of documents cited in the report is included in Appendix A. Review Comment No. 4 "Laboratory test data in document 1 appear were performed from a boring more than 170 feet east of the bluff top. Please provide soil test data and parameters obtained fro the bluff top area." Response to Comment No. 4 The boring location was chosen based upon drill access to the flag lot. The boring location was as close as feasible to the proposed work, in order to obtain representative samples and general engineering properties of the subsurface conditions. As stated in the Mr. Bill Geierman W.O.4799-A-SC 520 4'Street, Encinitas July 6, 2006 Re:e:\wp9\4700\4799a.rtt Page 2 GeoSoils, Inc. response to Comment No. 2,the soil column encountered within Boring B-1 is considered to be similar to the soil column exposed within the sea cliff/bluff slope, and all soil profiles in between,except specifically on the bluff face,where increased weathering occurs. This difference was considered during our evaluation. As such, the laboratory testing is considered to be representative of soil conditions in the immediate vicinity of the bluff. Review Comment No. 5 "Document 1 needs to provide a slope stability analysis of the bluff top in the present condition and with as-built mitigated conditions. The slope stability provided in the report (figure 5) is for stability only." Response to Comment No. 5 A response to Comment No. 5 will be provided by Soil Engineering Construction, Inc. (SEC). Review Comment No. 6 "The foundation recommendations provided in document 1 cannot be justified because there is no long term slope stability analysis performed for the project property." Response to Comment No. 6 The location -of Boring B-1 is shown on Plate 1 of the referenced report. Additional response to Comment No. 6 will be provided by SEC. Review Comment No. 7 "Figure 2 of document 1 needs to provide the location of the on-site test exploration, the failure plane analysis set back, the 75 year erosion plane, and the slope stability failure plane. These need to be on the geotechnical cross sections as well as on the plans (document 2)." Response to Review Comment No 7 A response to Comment No. 7 will be provided by SEC. It is our understanding that SEC will assume the role of geotechnical consultant of record. Mr. Bill Geierman W.O. 4799-A-SC 520 4h Street, Encinitas July 6, 2006 Fi1e:e:\wp9\4700\4799a.rtt Page 3 GeoSoiils, Inc. Review Comment No. 8 "The top of the bluff and definition need to be clearly provided by the geotechnical consultant and shown on the geotechnical map (Plate 1 of document 1) the geologic cross section (Figure 2 of document 1), and the project plans (document 2)." Response to Comment No. 8 A response to Comment No. 8 will be provided by SEC. Review Comment No. 9 "The geotechnical report (document 1) needs to provide discussion of the impact to the property/project in the event of a "maximum credible earthquake." Response to Review Comment No 9 The site is located within Reach 3 per USACOE (1996), and the Pacific View Subunit per Zeiser Kling Consultants, Inc. (ZKCI, 1994). Analyses performed in preparation of USACOE (1996) indicated a factor of safety of greater than 1.0 for seismic stability. The analysis performed in preparation of ZKCI (1994) indicated a "moderate" seismic slope failure potential,where slope failure was evaluated for"moderate local," large distant,"and large local earthquakes. The ZKCI study indicated that slope failure would most likely occur during a "large-local earthquake." A more detailed response to this comment will be provided by SEC. Review Comment No. 10 "The geotechnical consultant needs to provide discussion of the failed structures especially regarding if they were permitted or not. In addition, the geotechnical consultant is required to provide discussion analysis for other mitigation and/or correction options including but not limited to removal of all structures from the property, allowing the bluff face to erode and supplement the sand on the beach, providing a non-structural building set-back and other options as listed in the Municipal Code (document 6)." Response to Comment No 10 A response to Comment No. 10 will be provided by SEC. Review Comment No. 11 "The document 1 (page 25) provides for review of project plans. Please provide a copy of the geotechnical review of project plans (document 2)." Mr. Bill Geierman W.O. 4799-A-SC 520 4"' Street, Encinitas July 6, 2006 Fi1e:eAwp9\4700\4799a.rtt Page 4 GeoSoifls, Inc. Response to Comment No. 11 A response to Comment No. 11 will be provided by SEC. Review Comment No. 12 "Document 4 provides that Soils Engineering Construction Inc., "...is providing the geotechnical review work undertaken to receive this Coastal Emergency permit...". A standard assumption of geotechnical responsibility for the GeoSoils, Inc. report (document 1) as well as response to the review items listed above will be required from Soil Engineering Construction Inc." Response to Comment No. 12 A response to Comment No. 12 will be provided by SEC. LIMITATIONS The conclusions and recommendations presented herein are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. Mr. Bill Geierman W.O. 4799-A-SC 520 4t'Street, Encinitas July 6, 2006 File:e:\wp9\4700\4799a.rtt Page 5 GeoSoils, Inc. We appreciate the opportunity to be of service. If you have any questions pertaining to this report, please contact us at (760) 438-3155. Respectfully submitte ,SXOtAAL cRC,Fs �Q�p AO FjE.SS�/pN<�O S < GeoSoils, Inc. 0 a 0. 19 4 w � C 4 7 Certified Engineering 7t Geologist :`r Robert G. Crisman �gTFOF CAS\ � David W. Skelly qTc� c Engineering Geologist, 4 Civil Engineer, RCE A RGC/JPF/DWS/jk/jh Attachments: Appendix A- References (Revised) Appendix B - Boring Log B-1 Distribution: (4) Addressee Mr. Bill Geierman W.O. 4799-A-SC 520 4h Street, Encinitas July 6, 2006 File:eAwp9\4700\4799a.rtt Page 6 GeoSoils, Inc. APPENDIX A REFERENCES (REVISED) APPENDIX A REFERENCES (REVISED) Bird, Eric C.F., 1985, Coastline changes, a global review: John Wiley and Sons. Blake, T.F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version, updated to September, 2004. 2000b, EQSEARCH, A computer program for the estimation of peak horizontal acceleration from California historical earthquake catalogs; Updated through December, 2005, Windows 95/98 version. 2000c, FRISKSP, A computer program for the probabilistic estimation of peak acceleration and uniform hazard spectra using 3-D faults as earthquake sources; Windows 95/98 version, updated to September, 2004. Bozorgnia, Y., Campbell, K.W., and Niazi, M., 1999, Vertical ground motion: Characteristics, relationship with horizontal component, and building-code implications; Proceedings of the SMIP99 seminar on utilization of strong-motion data, September, 15, Oakland, pp. 23-49. Campbell, K.W. and Bozorgnia, Y. 1997, Attenuation relations for soft rock conditions; in EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version, Blake, 2000a. Curray, J.R., 1965, Late Quaternary history; continental shelves of the United States, p.723-735 in H.E. Wright, Jr. and D.G. Frey (eds), The Quaternary of the United States, Princeton University Press, 922 p. 1961, Late Quaternary sea level: a discussion, Geological Society of America Bulletin 72, p. 1707-12. 1960, Sediments and history of Holocene transgression, continental shelf, northwest Gulf of Mexico, p. 221-266, in F.P. Shepard, F.B. Phlefer, and Tj. H. van Andel (eds), Recent Sediments, Northwest Gulf of Mexico, 1951-1958, American Association of Petroleum Geologists, Tulsa, Oklahoma, 394 p. Eisenberg, L.T., 1985,Pleistocene faults and marine terraces, Northern San Diego County, in P.L. Abbott, ed.: On the Manner of De[position of the Eocene strata in Northern San Diego County. Pages 87-91, 3 Plates, San Diego Association of Geologists Guidebook. Emery, K.O. and Aubrey, D.G., 1991, Sea levels, land levels, and tide gauges: Springer- Verlag Publishers, New York, NY, 237 p., 113 figures. GeoSoils, Inc. Emery, K.O. and Kuhn, G.G., 1982, Sea cliffs: their processes, profiles, and classification: Geological Society of America Bulletin, v. 93, no 7. Hart, E.W. and Bryant, W.A., 1997, Fault-rupture hazard zones in California,Alquist-Priolo earthquake fault zoning act with index to earthquake fault zones maps; California Division of Mines and Geology Special Publication 42, with Supplements 1 and 2, 1999. Inman, D.L., 1976, Summary report of man's impact on the California coastal zone; prepared for the Department of Navigation and Ocean Development, State Of California. Inman, D.L. and Veeh, H.H., 1966, Dating the 10-fathom terrace off Hawaii, American Geophysical Union, Trans. 47, 125. International Conference of Building Officials, 1997, Uniform building code: Whittier, California. Kennedy, M.P., 1975, Geology of the San Diego metropolitan area, California; California Division of Mines and Geology, Bulletin 200, Section A, Western San Diego- Metropolitan Area, Del Mar, La Jolla, and Point Loma, 71h minute quadrangles. Kern. J.P., 1977, Origin and history of upper Pleistocene marine terraces, San Diego California, Geological Society of American Bulletin 88. Kuhn, G.G.,and Shepard, F.P., 1984, Sea Cliffs, beaches and coastal valleys of San Diego County: some amazing histories and some horrifying implications: University of California Press, Berkeley, California, and London, England. 1980 Coastal erosion in San Diego County, California, in Edge, B.L., ed., Coastal Zone `80, Proceedings of second Symposium on Coastal and Ocean Management held in Hollywood, Florida, on 17-20 November, 1980: American Society of Civil Engineers, V. III. Masters, P.M., and Fleming, N.C., 1983, Quaternary coastlines and marine archaeology: towards the prehistory of land bridges and continental shelves: Academic Press, New York, 641 p. Shakelton, N.J., and Opdyke, N.D., 1976, Oxygen - isotope and paleomagnetic stratigraphy of Pacific core V28-239, late Pliocene to Latest Pleistocene, Geological Society of America, Memoir 145. Sowers and Sowers, 1979, Unified soil classification system (After U. S. Waterways Experiment Station and ASTM 02487-667)in Introductory soil mechanics,New York. Mr. Bill Geierman Appendix A F1e:eAwp9\4700\4799aAt Page 2 GeoSoi ls, Inc. Tan, S.S., and Kennedy, M.P., 1996, Geologic maps of the Northwestern part of san Diego County, California, Plates 1 and 2, DMG Open File Report 96-02. Trenhaile, A.S., 1987, The geomorphology of rock coasts: Clarendon Press, Oxford. US Army Corps of Engineers, 1996, Reconnaissance report, Encinitas shoreline, San Diego County, California, dated March. Zeiser Kling Consultants, Inc., 1994, Final beach bluff erosion report, RFP#93-01, City of Encinitas, California, PN 93181-00, dated January 24. Mr. Bill Geierman Appendix A Fi1e:eAwp914700\4799a.rU Page 3 GeoSoiills, Inc. APPENDIX B BORING LOG 8-1 UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY Major Divisions Group Typical Names CRITERIA Symbols Well-graded gravels and gravel- CD GW sand mixtures,little or no fines Standard Penetration Test m o U Poorly graded gravels and Penetration m m m o GP gravel-sand mixtures,little or no Resistance N Relative o o > Z E w fines (blows/ft) Density O m o o ° Q o o m m GM Silty gravels gravel-sand-silt 0-4 Very loose ro Z ,° o � L. mixtures W o m C7 3 4-10 Loose m I GC Clayey gravels,gravel-sand-clay 0 9 mixtures 10-30 Medium m N Well-graded sands and gravelly 30-50 Dense 0 o m y SW sands,little or no fines U � o-5i U m >50 Very dense m C3 v SP Poorly graded sands and m c = o gravelly sands,little or no fines ° m L m Z m 0 aa) m w SM Silty sands,sand-silt mixtures O O � t m E a 3 .9 SC Clayey sands,sand-day mixtures Inorganic silts,very fine sands, Standard Penetration Test ML rock flour,silty or clayey fine % sands a� m •- > v E m Inorganic days of low to Unconfined m �— Penetration Compressive ° CL medium plasticity,gravelly clays, Resistance N Strength g a v o sandy days,silty days,lean (blows/ft) Consistency (tons/ft� J in clays 0 0 En Z <2 Very Soft <0.25 CD Organic silts and organic silty ry rmn OL clays of low plasticity a 2-4 Soft 0.25-.050 m P Inorganic silts,micaceous or LL ° MH diatomaceous fine sands or silts, 4-8 Medium 0.50-1.00 LL E ,° elastic silts ° U E c 8-15 Stiff 1.00-2.00 LO v Inorganic clays of high plasticity, N J CH fat clays 15-30 Very Stiff 2.00-4.00 m °1 Organic clays of medium to high >30 Hard >4.00 OH plasticity Highly Organic Soils PT Peat,mucic,and other highly organic soils 3" 3/4" #4 #10 #40 #200 U-S.Standard Sieve Unified Soil Cobbles Gravel Sand Silt or Clay Gassification coarse fine coarse medium fine MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS Dry Absence of moisture:dusty,dry to the touch trace 0-5% C Core Sample Slightly Moist Below optimum moisture content for compaction few 5-10% S SPT Sample Moist Near optimum moisture content little 10-25% B Bulk Sample Very Moist Above optimum moisture content some 25-45% 7 Groundwater Wet Visible free water;below water table Qp Pocket Penetrometer BASIC LOG FORMAT: Group name,Group symbol,(grain size),color,moisture,consistency or relative density. Additional comments:odor,presence of roots,mica,gypsum, coarse grained particles,etc. EXAMPLE: Sand(SP),fine to medium grained,brown,moist,loose,trace silt,little fine gravel,few cobbles up to 4"in size,some hair roots and rootlets. FIe:Mgr:c;\SoilClassif_wpd PLATE B-1 BORING LOG GeoSoils, Inc. WO. 4799-A-SC PROJECT.•MR. BILL GEIERMAN BORING B-1 SHEET 1 OF 2 520 4th Street, Encinitas DATE EXCAVATED 6-13-05 Sample SAMPLE METHOD: Hollow Stem Auger/California Sampler aStandard Penetration Test CD E �Z Groundwater 3 >1 _ m o ® Undisturbed,Ring Sample L o1 N U) C 7 N m 7 C O U) L, 6 o m D M D o v, Description of Material sM TERRACE DEPOSITS: S: 0'SILTY SAND, dark brown, moist, loose- many roots. 5 31 114.5 3.6 21.5 @ 5' SILTY SAND, brown, slightly moist, medium dense. 10 _ s: 15 � : s: f. 20 48 5P 3.3 @ 20'SAND w/SILT, light brown, slightly moist, dense. 25 5204th Street, Encinitas GeoSoils, Inc. PLATE 8-2 BORING LOG GeoSoils, Inc. W.0. 4799-A-SC PROJECT.-MR.BILL GEIERMAN BORING B-1 SHEET 2 OF 2 520 4th Street,Encinitas — DATE EXCAVATED 6-13-05 jSam SAMPLE METHOD: Hollow Stem Auger/California Sampler 0 Standard Penetration Test E c Graundwater Undisturbed,Ring Sample U)U D o M �, Description of Material sP z.4 11.7 @ 30' SAND w/SILT, yellowish gray, slightly moist, dense. 35 45 102.0 3.5 14.9 @ 35' SAND w/SILT, yellowish gray, slightly moist, dense. 40 45 so @ 49-50'Seepage encountered. 50-6° SP 106.0 THole Y FORMATION: ANDSTONE, light olive gray, slightly moist, dense. epth= 52' e Encountered @ 49-50' ckfilled 6-13-2005 With Bentonite Chips tes Sample Disturbed 55 520 4th Street, Encinitas GeoSoils, Inc. PLATE B-3 Geotechnical • Geologic • Environmental 5741 Palmer Way Carlsbad, California 92008 (760) 438-3155 • FAX (760) 931-0915 November 29, 2005 W.Q. 4799-A-SC Mr. Bill Geierman i "I s 520 4t'Street �� 1 62006 l _ Encinitas, California 92024 i� Subject: Revised Preliminary Geotechni al Evaluation;520,, Street, ncinitas, San Diego County, California --------- Dear Mr. Geierman: In accordance with your request, GeoSoils, Inc. (GSI) is pleased to present the results of ' our preliminary geotechnical evaluation at the subject site. The purpose of our study was to evaluate the geologic and geotechnical conditions of the bluff,so that recommendations for foundation design and earthwork parameters could be provided for the proposed construction. EXECUTIVE SUMMARY An existing "post and board" stabilization system at the subject property has been deteriorating over the past 25+ years. Due to a record rainfall in 2005,the system and mid to upper bluff recently experienced a significant failure that has placed the residential structure under imminent threat of damage/failure. It is our opinion that the threat to the structure is imminent and that remedial stabilization measures should be designed and implemented at the earliest time possible. Based upon our field exploration, geologic, and geotechnical engineering analysis, the proposed development appears feasible from a soils engineering and geologic viewpoint, provided that the recommendations presented in the text of this report are properly incorporated into the design and construction of the project. The most significant elements of our study are summarized below: • Earth materials, encountered or observed during the field investigation of the subject site,consisted of, Quaternary beach, Quaternary slump/talus deposits,and Quaternary terrace deposits, which are underlain by bedrock consisting of the Eocene-age Torrey Formation. Recent slope failure appears to be limited to within the terrace deposits occurring on the upper bluff. • Based upon the results of our evaluation, the existing bluff is surficially unstable. The existing residential structure is located within approximately 40 feet from the top of bluff, and is built out to the top of the bluff. A surficial slope failure within the upper bluff slope has recently occurred, resulting in the removal of some surficial improvements to the slope face (i.e., pipe and board slope stabilization), and continued failure of the slope will adversely affect the overall stability of the slope. In order to substantially mitigate any potential failure of soils supporting the existing residence, the residence should be supported on drilled piers bearing into the underlying bedrock material. • Laboratory testing indicates that site soils are low expansive(Expansion Index[E.I.] 21 to 50). However,the potential for medium expansive soils (E.I. = 51 to 90)to be locally encountered during construction cannot be entirely precluded. This should be considered during project planning and design. • Sulfate testing indicates that site soils have a negligible exposure to concrete per Table 19-A-4 of the Uniform Building Code ([UBC], International Conference of Building Officials [ICBO], 1997 [sample = 0.114 percent by weight]). Corrosion testing (pH/resistivity) indicates that the soils are essentially neutral (pH = 7.1) and are corrosive to ferrous metals (saturated resistivity = 1,500 ohms-cm). Alternative methods and additional comments should be obtained by a qualified corrosion engineer with regards to foundations, piping, etc., in light of site soils and nearby corrosive marine environment. • Subsurface and surface water are generally not anticipated to affect proposed site development provided that the recommendations contained in this report are incorporated into final design and construction, and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Perched groundwater conditions along fill/formational contacts, and along zones of contrasting permeabilities,may not be precluded from occurring in the future due to site irrigation, poor drainage conditions, or damaged utilities, and should be anticipated. Cross lot subsurface seepage cannot be precluded and may occur. Should perched groundwater conditions develop, this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions. The owner should be notified of the above potential. • No known active faults were observed to transect the site. • The geotechnical design parameters provided herein should be considered during construction by the project structural engineer and/or architect. Mr. Bill Geierman W.O.4799-A-SC Re:e:\wp12\4700\4799a.pge Page Two GeoSoiiis, Inc. We appreciate the opportunity to be of service. If you have any questions pertaining to this report, please contact us at (760) 438-3155. Respectfully submitted, \OSAL �Q?DFES3!014,/ F � o � �tv5 fie. FRgN�lo t.J` GeoSoils, Inc. 0 No. 1340 -a u n- Certified 0. 41857 Engineering Geologist r Uohn P. Fra 1 gTF0 C'koF � David W. Skell arc lVIL o`r�\ ngineering Geologist, C Civil Engineer, RCE 47 clk RGC/JPF/DWS/jh/jk Distribution: (4) Addressee Mr. Bill Geierman W.O. 4799-A-SC File:e:\wp12\4700\4799a_pge Page Three GeoSoils, Inc. TABLE OF CONTENTS SCOPE OF SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 SITE DESCRIPTION AND PROPOSED DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . . . . 1 FIELD STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 REGIONAL GEOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 COASTAL BLUFF GEOMORPHOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 SITE GEOLOGIC UNITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Quaternary Beach Deposits (Map Symbol - Qb) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Quaternary Slump/Talus Deposits (Map Symbol - Qs/t) . . . . . . . . . . . . . . . . . . . . 6 Quaternary Bay Point Formation (Map Symbol - Qt) . . . . . . . . . . . . . . . . . . . . . . 6 Torrey Formation (Map Symbol -Tt) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 FAULTING AND REGIONAL SEISMICITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Seismicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Seismic Shaking Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 SECONDARY SEISMIC HAZARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 GROUNDWATER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 LONG-TERM SEA LEVEL CHANGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lo COASTAL-BLUFF RETREAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Marine Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Mechanical and Biological Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Water Depth, Wave Height, and Platform Slope . . . . . . . . . . . . . . . . . . 12 Marine Erosion at the Cliff-Platform Junction . . . . . . . . . . . . . . . . . . . . . . 12 Subaerial Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Slope Decline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Surface Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Bluff Erosion Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 LABORATORY TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Moisture Density Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Laboratory Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : . . . . . . . . . . 14 Expansion Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Direct Shear Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 GrainSize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Saturated Resistivity, pH, and Soluble Sulfates . . . . . . . . . . . . . . . . . . . . . . . . . 15 GeoSoils, Inc. SLOPE STABILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 DISCUSSION AND PRELIMINARY CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Slope Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Proposed Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 PRELIMINARY RECOMMENDATIONS - FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . 19 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Drilled Pier and Grade Beam Foundation Recommendations . . . . . . . . 19 Passive Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Pointof Fixity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Allowable Axial Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Caisson Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Drilled Pier and Grade Beam Foundation Settlement . . . . . . . . . . . . . . . . . . . . . 21 Corrosion and Concrete Mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 DEVELOPMENT CRITERIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Erosion Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Landscape Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Gutters and Downspouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Subsurface and Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Site Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Additional Grading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Pier Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 OTHER DESIGN PROFESSIONALS/CONSULTANTS . . . . . . . . . . . . . . . . . . . . . . . . . . 25 PLAN REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 LIMITATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 FIGURES: Figure 1 - Site Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Figure 2 - Geologic Cross Section A-A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Figure 3 - California Fault Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 4 - Laboratory Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Figure 5 - Surficial Slope Stability . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 18 ATTACHMENTS: Appendix A - References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rear of Text Appendix B - Boring Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Rear of Text Plate 1 - Geotechnical Map . . . . . . . . . . . . . . . . . . . . . . . . . Rear of Text in Folder Mr. Bill Geierman Table of Contents Flee:\wp12\4700\4799a.pge GeoSoils, I»e. Page ii PRELIMINARY GEOTECHNICAL EVALUATION 520 4u' STREET, ENCINITAS SAN DIEGO COUNTY, CALIFORNIA SCOPE OF SERVICES The scope of our services has included the following: 1. Review of readily available published literature,aerial photographs,and maps of the vicinity, including available geologic/geotechnical reports published for other sites within the vicinity of the subject site (see Appendix A). 2. Site reconnaissance and subsurface explorations, consisting of geologic logging and mapping of earth materials exposed on the bluff face and a deep small-diameter, hollow stem auger boring, to evaluate the soil/bedrock profiles, sampling of representative materials, and the delineation of earth materials (see Appendix B and Plate 1). 3. General areal seismicity evaluation. 4. Appropriate laboratory testing of representative soil samples collected during our geologic mapping and subsurface exploration program. 5. Slope stability analysis of the recently failed coastal bluff with remedial recommendations for mitigation of stability concerns for the existing residence. 6. Appropriate engineering and geologic analyses of data collected, and the preparation of this report and accompaniments SITE DESCRIPTION AND PROPOSED DEVELOPMENT The site consists of a flag-shaped lot, located at 520 4t' Street, between D Street and E Street, in Encinitas, San Diego County, California(see Figure 1 -Site Location Map). The site is bounded by the Pacific Ocean to the west, 4h Street to the east, and existing residential development on the remaining sides. The existing structure is located very near, or on, the bluff edge. The bluff face was fitted with an extensive "post and board" stabilization system sometime between 1979 and 1987. Portions of the system have failed over the years. The system recently experienced a significant failure as a result of the recent record rainfall. The bluff top has eroded beneath the deck and structure foundation. Based upon our review of the published geologic data in this area and our own site exploration, it appears that the site is underlain by Quaternary-age terrace deposits exposed within the upper, bluff slope,and older, Eocene-age sedimentary bedrock,within the lower bluff, or sea cliff. It is our recommendation that the applicant take immediate steps to obtain an engineered solution that will return an acceptable level of mitigation of the existing residential structure. GeoSoils, Inc. A �lt aa*r� � r y 0 tOW FEET Base Map: TOPOW ©2003 National Geographic, USGS Encinitas Quadrangle, California-San Diego Co., 7.5-Minute, dated 1997, current 1999. E ()R Aj spa ; vCVW:1' BEACH ►- ~ " - sro . } � H SMET w YT£WPOINt RK . w s PA " �k ST Q 1000 FEET Base Map: The Thomas Guide, San Diego Co. Street Guide and Directory, 2005 Edition, by Thomas Bros. Maps, page 1147. LOCATION AND SCALES APPROXIMATE Reproduced with permission granted by Thomas Bros.Maps. i _ ,i - W.O. 4799-A-SC This rW is copyrighted by Thomas Bros.Maps. It is unlawful to 0009i, s `� � copy or reproduce a9 or any part thereof.whether for personal or resale,wilfiaA permission. AN rights Reserved 4116, SITE LOCATION MAP Figure 1 It appears from our analysis that the most minimal form of such a stabilization effort would include the design and placement of an upper bluff retention wall on the face of the failed upper bluff. FIELD STUDIES Site specific field studies,conducted by GSI, consisted of geologic mapping of the coastal bluff, and the advancement of a small diameter boring near the eastern end of the property, for an evaluation of near-surface soil and geologic conditions. The coastal bluff and boring were mapped and logged by an engineering geologist from our firm who collected representative bulk and undisturbed samples for appropriate laboratory testing. The logs of the borings are presented in Appendix B. Site geology and the location of the boring are presented on the Geotechnical Map (see Plate 1) and shown in the cross section on Figure 2. REGIONAL GEOLOGY The subject property is located within a prominent natural geomorphic province in southwestern California known as the Peninsular Ranges. It is characterized by steep, elongated mountain ranges and valleys that trend northwesterly. The mountain ranges are underlain by basement rocks consisting of pre-Cretaceous metasedimentary rocks, Jurassic metavolcanic rocks, and Cretaceous plutonic rocks of the southern California batholith. In the San Diego region, deposition occurred during the Cretaceous Period and Cenozoic Era in the continental margin of a forearc basin. Sediments, derived from Cretaceous-age plutonic rocks and Jurassic-age volcanic rocks, were deposited during the Tertiary Period (Eocene-age) into the narrow, steep, coastal plain and continental margin of the basin. These rocks have been uplifted, eroded, and deeply incised. During early Pleistocene time, a broad coastal plain was developed from the deposition of marine terrace deposits. During mid to late Pleistocene time, this plain was uplifted, eroded and incised. Alluvial deposits have since filled the lower valleys, and young marine sediments are currently being deposited/eroded within coastal and beach areas. The subject site is underlain by Quaternary-age terrace deposits deposited along an unconformity (contact) with the underlying Eocene-age bedrock. COASTAL BLUFF GEOMORPHOLOGY The typical coastal-bluff profile may be divided into three zones:the shore platform; a lower near-vertical cliff surface termed the sea cliff; and an upper bluff slope generally ranging in inclination between about 35 and 65 degrees (measured from the horizontal). The bluff top is the boundary between the upper bluff and coastal terrace. Mr. Bill Geierman W.O. 4799-A-SC 520 4"'Street, Encinitas November 29, 2005 He:e:\wp12\4700\4799a.rpge GeoSoiis, Inc. Page 3 0 0 co 0 N 0 0 N Q M O g � N W.-!W> Qf..—OZ ~ W Z W L) Z p U Q o � Q LLI Co i n Oa ir O LL �- ~ LL W LL��,. W U. .J O W V Z W _0 W C3 ~ Z co X W av W C 8 U C7 O O O v.. O C O E �X O 1 W Z O d W J F' LL to QW � J Q ti yu,W U 4) LL o- Q Z v O u' C0 W ` o W U i 4: N m J E Il ca c � o y 0 I p N I v y a CL w E v W E LL y WJW>QF- -OZ ? C MO cr- � d M O - - N o O � Offshore from the sea cliff is an area of indefinite extent termed the near-shore zone. The bedrock surface in the near-shore zone,which extends out to sea from the base of the sea cliff, is the shore platform. As pointed out by Trenhaile (1987), worldwide the shore platform may vary in inclination from near horizontal to as steep as 3:1 (horizontal: vertical [h:v]). The boundary between the sea cliff (the lower vertical and near-vertical section of the bluff) and the shore platform is called the cliff-platform junction, or sometimes the shoreline angle. Within the near-shore zone is a subdivision called the inshore zone, beginning where the waves begin to break. This boundary varies with time because the point at which waves begin to break changes dramatically with changes in wave size and tidal level. During low tides, large waves will begin to break further away from shore. During high tides, waves may not break at all, or they may break directly on the lower cliff. Closer to shore is the foreshore zone, that portion of the shore lying between the upper limit of wave wash at high tide and the ordinary low water mark. Both of these boundaries often lie on a sand or cobble beach. In this case,a shoreline with a bluff,the foreshore zone extends from low water to the lower face of the bluff. Emery and Kuhn (1982)developed a global system of classification of coastal bluff profiles, and applied that system to the San Diego County coastline from San Onofre State Park to the southerly tip of Point Loma. Emery and Kuhn (1982) designated this portion of the coast as "active" and "Type A (a)," as the surficial deposits are relatively thin with respect to the underlying bedrock The letter "A" designates coastal bluffs having uniformly resistant geologic formation throughout the entire bluff profile. The relative effectiveness of marine erosion compared to subaerial erosion of the bluff produces a characteristic profile. Extremely rapid marine erosion produces a less gently-sloping and steeper upper bluff. The letter "(a)" indicates that the long-term rate of subaerial erosion is much less than that of marine erosion. SITE GEOLOGIC UNITS The earth material units that were observed and/or encountered in the vicinity of the subject site and the coastal bluff consist of Quaternary Beach Deposits, older Quaternary-age terrace deposits, and Eocence-age bedrock belonging to the Torrey and Point Loma Formations. Mapped units are shown on the Geotechnical Map (see Plate 1) and shown in the cross section on Figure 2. A general description of each material type is presented as follows, from youngest to oldest. Quaternary Beach Deposits (Map Symbol - Qb) A transient shingle beach composed of sand and rounded cobbles exists at the base of the bluff. The beach deposits will not be encountered in the vicinity of the existing structure. Mr. Bill Geierman W.O. 4799-A-SC 520 a Street, Encinitas November 29, 2005 He:e:\wp12\4700\4799a.rpge GeoSoils, Inc. Page 5 Quaternary Slump/Talus Deposits (Map Symbol - Qs/t) Slump/talus deposits composed of sand and rounded cobbles exist near the base of the bluff slope, and appear to have locally burried the lower bluff slope, or sea cliff. While the scar created by the detachment of the material from the upper bluff slope remains, the slump/talus deposits are located near the base of the bluff and will not be encountered in the vicinity of the existing structure. Quaternary Bay Point Formation (Map Symbol - Qtl Our field observations, and literature review indicate that the upper-most portion of the coastal bluff at the subject site is primarily composed of the Quaternary-age terrace deposits. These formational materials generally consist of brown to gray,moist and dense sand and silty sand. The upper ±1 foot to ±2 feet of near-surface weathered terrace deposits are generally loose/soft and potentially compressible. Below this depth,terrace deposits become weakly cemented/indurated to an approximate depth of 15 feet. Below this depth, terrace deposits are less cemented and more friable. Terrace deposits are weakly bedded. Bedding orientations were observed to be generally sub-horizontal. Torrey Formation (Map Symbol -Tt) The Eocene Torrey Formation unconformably underlies terrace deposits atthe subject site. These formational materials consist of cemented and indurated sandstones. Cross bedding is relatively well developed. Bedding trends(strikes)were observed to range from approximately N3W to N70W, with dips (inclination) ranging from 3 to 22 degrees to the northeast. Fractures trending about N30E, dipping 89NW and N80W,dipping 30 NE were also observed. FAULTING AND REGIONAL SEISMICITY Our review indicates that there are no known active faults crossing this site within the area proposed for development, and the site is not within an Earthquake Fault Zone (Hart and Bryant, 1997). However, the site is situated in an area of active, as well as potentially active, faulting. These include, but are not limited to: the San Andreas fault; the San Jacinto fault; the Elsinore fault; the Coronado Bank fault zone; and the Newport-Inglewood Rose Canyon fault zone. The location of these, and other major faults relative'to the site, are indicated on Figure 3 (California Fault Map). The possibility of ground acceleration,or shaking at the site, may be considered as approximately similar to the southern California region as a whole. Major active fault zones that may have a significant affect on the site,should they experience activity,are listed in the following table (modified from Blake, 2000a): Mr. Bill Geierman• W.O. 4799-A-SC 520 a Street, Encinitas November 29, 2005 File:e:\wp12\4700\4799a.rpge Geosoils, Inc. Page 6 CALIFORNIA FAULT MAP 4799 1100 1000 900 800 700 600 500 400 300 200 100 o ;SI 0 -100 -400 -300 -200 -100 0 100 200 300 400 500 600 W.O. 4799-A-SC GeoSoils, Inc. Figure 3 APPROXIMATE DISTANCE `ABBREVIATED FAULT NAME ?.MILES KM Rose Canyon 2.9 (4.7) Coronado Bank 10.8 (17.4) Newport-Inglewood (Offshore) 25.9 (41.7) Elsinore (Julian) 40.3 (64.8) Elsinore (Temecula) 41.9 (67.5) Earthquake Valle 47.4(76.3 Seismicity The acceleration-attenuation relations of Bozorgnia, Campbell, and Niazi (1999) and Campbell and Bozorgnia (1997 Revised) have been incorporated into EQFAULT (Blake, 2000a). EQFAULT is a computer program developed by Thomas F. Blake (2000a),which performs deterministic seismic hazard analyses using digitized California faults as earthquake sources. The program estimates the closest distance between each fault and a given site. If a fault is found to be within a user-selected radius,the program estimates peak horizontal ground acceleration that may occur at the site from an upper bound ("maximum credible") earthquake on that fault. Site acceleration (g) is computed by one or more user-selected acceleration-attenuation relations that are contained in EQFAULT. Based on the EQFAULT program, peak horizontal ground accelerations from an upper bound event at the site may be on the order of 0.74g to 0.86g. Historical site seismicity was evaluated with the acceleration-attenuation relations of Campbell and Bozorgnia (1997 Revised) and the computer program EQSEARCH (Blake, 2000b). This program performs a search of the historical earthquake records for magnitude 4.0 to 9.0 seismic events within a 100-mile radius, between the years 1800 to June 2004. Based on the selected acceleration-attenuation relationship,a peak horizontal ground acceleration is estimated, which may have effected the site during the specific event listed. Based on the available data and the attenuation relationship used, the estimated maximum (peak) site acceleration during the period 1800 to June 2004, was 0.24g. Site specific probability of exceeding various peak horizontal ground accelerations and a seismic recurrence curve are also estimated/generated from the historical data. A probabilistic seismic hazards analyses was performed using FRISKSP (Blake, 2000c), which models earthquake sources as three-dimensional planes and evaluates the site specific probabilities of exceedance for given peak acceleration levels or pseudo-relative velocity levels. Based on a review of this data,and considering the relative seismic activity of the southern California region, a peak horizontal ground acceleration of 0.34g was Mr. Bill Geierman W.O. 4799-A-SC 520 a Street, Encinitas November 29, 2005 File:e:\wp12\4700\4799a.rpge GeoSoils, Inc. Page 8 calculated. This value was chosen as it corresponds to a 10 percent probability of exceedance in 50 years (or a 475-year return period). Seismic Shaking Parameters Based on the site conditions, Chapter 16 of the Uniform Building Code ([UBC], International Conference of Building Officials [ICBO], 1997), the following seismic parameters are provided below. The Rose Canyon Fault is the design earthquake fault for the subject site as it is located approximately 2.9 miles (4.7 km) east of the site. Seismic zone (per Figure 16-2*) 4 Seismic Zone Factor (per Table 16-1*) 0.40 Soil Profile Type (per Table 16-J*) Sp Seismic Coefficient C.(per Table 16-Q*) 0.44 N. Seismic Coefficient C„(per Table 16-R*) 0.64 N„ Near Source Factor N.(per Table 16-S*) 1.1 Near Source Factor N„(per Table 16-T*) 1.3 Seismic Source Type (per Table 16-U*) B Distance to Seismic Source (Rose Canyon) 2.9 mi (4.7 km) Upper Bound Earthquake (Rose Canyon) M,,,6.9 * Figure and table references from Chapter 16 of the UBC (IC13 1997). SECONDARY SEISMIC HAZARDS Potential secondary seismic related hazards such as ground rupture due to faulting, liquefaction, dynamic settlement,tsunami,and seiche,are often associated with a seismic event. Since no active faults are known to cross the site, the potential for ground rupture is considered low. Based on the dense nature of the Quaternary and Cretaceous bedrock that underlie the site,the potential for liquefaction to affect the site appears to be low. The potential for dynamic settlement and associated distress to affect the site appears to be low to moderate. Due to the elevation of the proposed residential structure above Mean Sea Level (MSL), i.e., approximately ±60 feet, the potential for tsunami to affect the proposed development is considered low. However,significant tidal waves generated from a seismic event could affect the lower portion of the site and affect overall bluff stability, possibly even affecting the proposed structure. The potential for seiche to affect the proposed development is considered nil due to the non-existence of enclosed shallow bodies of water near the site. Mr. Bill Geierman W.O. 4799-A-SC 520 e Street, Encinitas November 29, 2005 File:e:\wp12\4700\4799a.rpge GeoSoils, Ine. Page 9 GROUNDWATER Perched water was observed along the contact between terrace deposits and the underlying bedrock within Boring B-1, but was not observed along the contact exposed at the slope face. While not observed at the time of our study, seepage may not be precluded from developing at the slope face in the future. Perched water seepage,exiting the bluff face,could potentially cause spring sapping and solution cavities along joints,and bedding planes, locally accelerating marine erosion where these conditions exist. In addition, perched water may infiltrate bluff-parallel joints,which form naturally behind and parallel to the bluff face as a result of near-surface, stress-relief. Perched groundwater is not expected to significantly influence the stabilization of the existing residence. Should manifestations of this perched condition (i.e., seepage) develop in the future, this office could assess the conditions and provide mitigative recommendations, as necessary. The regional water table is generally consistent with sea level. LONG-TERM SEA LEVEL CHANGE Long-term (geologic) sea level change is the major factor determining coastal evolution (Emery and Aubrey, 1991). Three general sea level conditions are recognized: rising, falling,and stationary. The rising and falling stages result in massive sediment release and transport,while the stationary stage allows time for adjustment and reorganization toward equilibrium. Major changes in sea level of the Quaternary period were caused by worldwide climate fluctuation resulting in at least seventeen glacial and interglacial stages in the last 800,000 years and many before then (Shakelton and Opdyke, 1973 and 1976). Worldwide sea level rise associated with the melting of glaciers is commonly referred to as"glacio-eustatic"or"true"sea level rise. During the past 200,000 years,eustatic sea level has ranged from more than ±350 feet below the present to possibly as high as about ±31 feet above. Tectonic activity can also account for significant relative changes in sea level in a local area. Past movement along the Rose Canyon fault zone and associated faults, which served to uplift Mount Soledad and formed Point La Jolla,also created a zone of structural weakness along which the La Jolla Submarine Canyon has been incised. The Torrey Pines block, with its relatively horizontally stratified Eocene-age formations and wave-cut terraces, has experienced more than 450 feet of tectonic uplift in the last 2 million years, while the tilted and uplifted Soledad Mountain block has undergone more than 750 feet of tectonic uplift in the same period (Kern, 1977). Sea level changes during the last 18,000 years have resulted in an approximately 400-foot rise in sea level when relatively cold global climates of the Wisconsin ice age started to become warmer, melting a substantial portion of the continental ice caps (Curray, 1960 and 1961). Sea level data show a relatively rapid rise of about 1 meter per century from about 18,000 years before present to about 8,000 years ago, as indicated in Masters and Fleming (1983). About 8,000 years ago, the rate of sea level rise slowed, ultimately to a Mr. Bill Geierman W.O. 4799-A-SC 520 a Street, Encinitas November 29, 2005 Fi1e:e:\wp12\4700\4799a.rpge GeoSoiils, Znc. Page 10 relatively constant rate of about 10 centimeters per century since about 6,000 years ago (Curray, 1960 and 1965; Inman and Veeh, 1966). More importantly, the world coastline, including that of California and the subject site, has been shaped largely within this 6,000-year period, with the sea at or within 16 feet of its present level (Bird, 1985). COASTAL-BLUFF RETREAT Most of San Diego County's coastline has experienced a measurable amount of erosion in the last 20 to 30 years,with more rapid erosion occurring during periods of heavy storm surf (Kuhn and Shepard, 1984). The entire base of the sea cliff portion of the coastal bluff is exposed to direct wave attack along most of the coast. The waves erode the sea cliff by impact on small joints/fractures and fissures in the otherwise essentially massive bedrock units, and by water-hammer effects. The upper bluffs, which often support little or no vegetation, are subject to wave spray and splash, sometimes causing saturation of the outer layer and subsequent sloughing of over-steepened slopes. Wind,rain,irrigation,and uncontrolled surface runoff contribute to the erosion of the upper coastal bluff, especially on the more exposed over-steepened portions of the friable sands. Where these processes are active, unraveling of cohesionless sands has resulted along portions of the upper bluffs. Marine Erosion The factors contributing to "Marine Erosion" processes are described below. Mechanical and Biological Processes Mechanical erosion processes at the cliff-platform junction include water abrasion, rock abrasion, cavitation, water hammer, air compression in joints/fractures, breaking-wave shock, and alternation of hydrostatic pressure with the waves and tides. All of these processes are active in .backwearing. Downwearing processes include all but breaking-wave shock (Trenhaile, 1987). Backwearing and downwearing, by the mechanical processes described above, are both augmented by bioerosion,the removal of rock by the direct action of organisms (Trenhaile, 1987). Backwearing at the site is assisted by algae in the intertidal and splash zones and by rock-boring mollusks in the tidal range. Algae and associated small organisms bore into rock up to several millimeters. Mollusks may bore several centimeters into the rock. Chemical and salt weathering also contribute to the erosion process. Mr. Bill Geierman W.O. 4799-A-SC 520 4"'Street, Encinitas November 29, 2005 File:e:\wp12\4700\4799a.rpge GeoSoiis, Ine. Page 11 Water Depth, Wave Height, and Platform Slope The key factors affecting the marine erosion component of bluff-retreat are water depth at the base of the cliff, breaking wave height, and the slope of the shore platform. Along the entire coastline, the sea cliff is subject to periodic attack by breaking and broken waves, which create the dynamic effects of turbulent water and the compression of entrapped air pockets. When acting upon jointed and fractured rock, the "water-hammer" effect tends to cause hydraulic fracturing which exacerbates sea cliff erosion. Erosion associated with breaking waves is most active when water depths atthe cliff-platform junction coincide with the respective critical incoming wave height, such that the water depth is approximately equal to 1.3 times the wave-height. Marine Erosion at the Cliff-Platform Junction The cliff-platform junction contribution to retreat of the overall sea cliff is from marine erosion,which includes mechanical, chemical, and biological erosion processes. Marine erosion, which operates horizontally (backwearing) on the cliff as far up as the top of the splash zone, and vertically (downwearing) on the shore platform (Emery and Kuhn, 1980; Trenhaile, 1987). Backwearing and downwearing typically progress at rates that will maintain the existing gradient of the shore platform. Subaerial Erosion "Subaerial Erosion" processes are discussed as follows: Groundwater The primary erosive effect of groundwater seepage upon the formational materials at the site is spring sapping, or the mechanical erosion of sand grains by water exiting the bluff face. Chemical solution, however, is also a significant contributor(especially of carbonate matrix material). As indicated previously,as groundwater approaches the bluff,it infiltrates near-surface, stress-relief, bluff-parallel joints/fractures, which form naturally behind and parallel to the bluff face. Hydrostatic loading of bluff parallel (and sub-parallel) joints/fractures is an important cause of block-toppling on steep-cliffed lower bluffs (Kuhn and Shepard, 1980). Slope Decline The process of slope decline consists of a series of steps, which ultimately cause the bluff to retreat. The base of the bluff is first weakened by wave attack and the development of wave cut niches and/or sea caves, and bluff parallel tension joint/fractures. As the weakened sea cliff fails by blockfall or rockfall,an over-steepened bluff face is left,with the debris at the toe of the sea cliff. Ultimately,the rockfall/blockfall debris is removed by wave action, and the marginal support for the upper bluff is thereby removed. Progressive surficial slumping and failure of the bluff will occur until a condition approaching the angle Mr. Bill Geierman W.O.4799-A-SC 520 a Street, Encinitas November 29, 2005 Fe:eAwp12\4700\4799a.rpge GeoSoils, Inc. Page 12 of repose is established over time, and the process begins anew. Upper bluffs with slope angles in the 35 to 40 degrees range may indicate ages in the 75- to 100-year range. Steeper slopes indicate a younger age. Slopes angles at the site vicinity indicate a relatively young age (i.e., 30 to 40 years), which are generally typical of active erosion. Surface Drainage Uncontrolled concentrated surface drainage has resulted in significant upper bluff erosion in the vicinity of the site in the recent past. Improvements, such as patios and pools, located at, or adjacent to, the bluff top can result in the creation of water paths that concentrate surface water runoff on the bluff soils. In addition, patio area drains often become clogged with vegetation during torrential rains which results in concentrated uncontrolled surface water runoff over the bluff. These "top down" type bluff failures are characterized by small W"shaped erosion gullies,a few feet across,that extend down the bluff face but terminate above the wave runup line. Wave induced marine erosion is characterized by wave notching at the bluff face resulting in the failure from the bottom of the bluff upward. The subject site has no such bluff top or near the bluff top improvements, and site drainage is controlled and does not significantly contribute to bluff erosion. Bluff Erosion Summary A comprehensive study of bluff erosion along the Encinitas Shoreline and covering this site was conducted by the US Army Corps of Engineers in 1996 (USACOE, 1996). The report examined available information and published reports concerning bluff retreat rates along the Encinitas shoreline. The subject site is located in what the Corps report describes as Reach 3. Reach 3 covers the coastal segment from Moonlight Beach to the Self Realization Fellowship Beach access stairs. The average bluff erosion rate along Reach 3 is reported to be 0.2 feet/yr. Although GSI disagrees with the concept of average erosion rates coastal bluffs (Kuhn and Shepard, 1984),however,in consideration of the weightthat various governmental agencies unscientifically ascribe to assigning an erosion rate to coastal bluffs, GSI has reviewed the data regarding erosion rates in the site vicinity, and is in general agreement with the range of erosion rates presented above, and it is our opinion that these rates are generally applicable to the subject site. While bluff erosion characteristically coincides with major storm events, our evaluation indicates that erosion in the range of 1 inch to 2 inches per year may be occurring. This range appears to be relatively conservative for estimating future bluff erosion at this site. This translates to about 61/4 to 121/2 feet in 75 years. A review of aerial photographs (www.californiacoastline.org) between the years of 1972 and 2002, does not indicate a significant amount of bluff retreat. A visual comparison of the photographs show anywhere from 0 to about 5 feet of erosion in the vicinity of the site. The recent site bluff failure was located within the upper and middle portions of the bluff and resulted in downslope movement of about 2 feet of thickness of the face. In addition, the bluff failed at the top to at, or beneath, the existing structure and attached patio. Mr. Bill Geierman W.O. 4799-A-SC 520 e Street, Encinitas November 29, 2005 File:e:\wpl2\4700\4799a.rpge GeoSoils, Ine. Page 13 LABORATORY TESTING Laboratory tests were performed on representative samples of representative site earth materials in order to evaluate their physical characteristics. Test procedures used and results obtained are presented below. Classification Soils were classified visually according to the Unified Soils Classification System (Sowers and Sowers, 1979). The soil classifications of onsite soils is provided on the Boring Log in Appendix B. Moisture Density Relations The field moisture contents and dry unit weights were determined for selected undisturbed samples in the laboratory. The dry unit weight was determined in pounds per cubic foot (pcf), and the field moisture content was determined as a percentage of the dry weight. The results of these tests are shown on the Boring Log in Appendix B. Laboratory Standard The maximum dry density and optimum moisture content was determined for representative, bulk soil samples. The laboratory standard used was ASTM D-1557. The moisture density relationships obtained for these soils are shown below: SAMPLE LOCATION AND MAXIMUM DENSITY OP..TIMUM MOISTURE ." DEPTH ' c CONTENT. 9'0 . B-1 @ 0 to 5 feet r 122.5 9.5 Expansion Potential Expansion testing was performed on a representative, composite sample of site soil in accordance with UBC Standard 18-2. The results of the expansion testing are presented in the following table: SAMPLE LOCATION SOIL TYPE EXPANSION EXPANSION AND DEPTH INDEX, POTENTIAL B-1 @ 0-5 feet (composite) SILTY SAND, Brown <10 Very Low Mr. Bill Geierman W.O. 4799-A-SC 520 4"'Street, Encinitas November 29, 2005 He:e:\wp12\4700\4799a.rpge GeoSoils, Inc. Page 14 Direct Shear Tests Shear testing was performed on relatively undisturbed and remolded samples of site soil in general accordance with ASTM Test Method D-3080. Test results are presented on the following table. PRIMARY RESIDUAL SAMPLE LOCATION AND COHESION FRICTION AN COHESION FRICTION ANGLE:, DEPTIi(FT) PS ?.: DEGREE S) PS DEGREES .. B-1 @ 5' (undisturbed) 65 37 72 36 B-1 @ 20' (undisturbed) 269 30 240 30 B-1 @ 45' undisturbed 225 33 152 34 Grain Size Testing to determine the grain size distribution of selected soil samples was performed in general accordance with ASTM D-422. Test results are included as Figure 4. Saturated Resistivity, pH, and Soluble Sulfates A typical sample of the site material was analyzed by M. J. Schiff and Associates, Inc., for saturated resistivity, pH,and soluble sulfates. Results indicate that site soils are neutral to slightly acidic (pH=6.2) with respect to acidity and have a saturated resistivity of 4,000 ohm-cm. Thus, the site soils are corrosive to ferrous metals when saturated. Corrosive soils are considered to range between 1,000 and 2,000 ohms-cm. Testing indicates that the site soils have a negligible sulfate exposure to concrete (1997 UBC range for negligible sulfate exposure is 0.00 to 0.10 percentage by weight soluble ISO41 in soil). Alternative testing methods and additional comments should be obtained from a qualified corrosion engineer with regard to foundations,metal,piping,etc.,that may come into contact with site soils. Laboratory test results are presented in Figure 4. SLOPE STABILITY This existing bluff slope is currently in the process of eroding and surfiicial bluff failure has occurred within the upper bluff slope. Due to the granular and the lightly indurated, unconfined nature of earth materials exposed atthe slope face,they will continue to recede if left exposed to weathering. Mr. Bill Geierman W.O.4799-A-SC 520 a Street, Encinitas November 29, 2005 Flee:\wp12\4700\4799a.rpge GeoSonls, Inc. Page 15 M. J. Schiff& Associates, Inc. Consulting Corrosion Engineers-Since 1959 Phone: (909) 626-0967 Fax. (909) 626-3316 431 W.Baseline Road E-mail lab@,mjschiff.com Claremont,CA 91711 website:mjschiff.com Table 1 - Laboratory Tests on Soil Samples GeoSoils,Inc. Gierman Your#4799-A-SC,MJS&A 905-0901LSD 23-Jun-05 Sample ID B-1 Resistivity Units as-received ohm-cm 220,000 saturated ohm-cm 4,000 pH 6.2 Electrical Conductivioj MS/cm 0.12 Chemical Analyses Cations calcium Ca"_ mg/kg 44 magnesium Mg" mg/kg 10 sodium Nal- mg/kg ND Anions carbonate CO3 2- mg/kg ND bicarbonate HCO3 mg/kg 55 chloride Cl'- mg/kg 40 sulfate SO4 2- mg/kg ND Other Tests ammonium NH4 1+ mg/kg na nitrate NO3 I- mg/kg na sulfide S 2- qual na Redox my na Electrical conductivity in millisiemens/cm and chemical analysis were made on a 1:5 soil-to-water extract. mg/kg=milligrams per kilogram(parts per million)of dry soil. Redox=oxidation-reduction potential in millivolts ND=not detected na=not analyzed W.O. 4799-A-SC Figure 4 Based on a review of Plate 1, the existing structure generally lies within approximately 40 feet from the top of the existing bluff. Our experience with slope stability issues and analysis of slope stability in the vicinity indicates that this area of the bluff does not possess an adequate factor of safety against failure, and is less stable than areas located further to the east of the bluff top. It should be noted that the City generally requires a setback of at least 40 feet to any new construction,from the top of the bluff. Slope stability analyses are provided as Figure 5. The bluff slope, if left untreated, will likely continue to progressively erode and/or slump and may accelerate during strong seismic shaking, severe winter storms, or other similar events. Accordingly, there is some potential that natural slopes may be subject to instability during seismic shaking, heavy precipitation, or strong storms, as would other similar existing slopes in the coastal southern California area. Based on the general location of the existing structure relative to the slope, mitigation, in the form of underpinning of the existing structure is necessary in order to stabilize the structure. DISCUSSION AND PRELIMINARY CONCLUSIONS General Based on our field exploration, laboratory testing and geotechnical engineering analysis, it is our opinion that the subject site appears suitable for the proposed residential development from a geotechnical engineering and geologic viewpoint, provided that the recommendations presented in the following sections are incorporated into the design and construction phases of site development. The primary geotechnical concerns with respect to the proposed development are: • Slope stability of the coastal bluff. • Depth to competent bearing material. • Expansion and corrosion potential of the onsite soil. • Potential for perched water. • Regional seismicity and related effects. Slope Stability Proposed Development The existing residence is in imminent danger from bluff failure and should be stabilized as soon as possible. While a mid/upper bluff retaining wall and or a seawall with bluff reconstruction may be suitable for stabilizing the structure, it is our experience that the regulatory agencies prefer either a soldier pile system or drilled pier and grade beam system. The geotechnical design parameters forthe soldier pile system and the drilled pier and grade beam system are the same. These design parameters are provided in the next Mr.Bill Geierman W.O.4799-A-SC 520 a Street, Encinitas November 29, 2005 File:e:\wpl2\4700\4799a.rpge Page 17 GeoSoils, Inc. SURFICIAL SLOPE STABILITY ANALYSIS 1.5 1 z rr Seepage parallel to slope Tract/Project: Geierman Material Type: Terrace Deposits Depth of Saturation z 4 feet Slope Angle (i for 1.5:1 slopes) 33.7 degrees Unit Weight of Water (y,,) 62.4 Ib/ft3 Saturated Unit Weight of Soil (ys.J 125 Ib/ft3 lApparent Angle of Internal Friction 30 Idegrees Apparent Cohesion (C) A 70 Ib/ft2 Fs= Static Safety Factor= z Cos2(i)Tan (�) + C z(yS,J Sin (i)Cos (i) DEPTH OF SATURATION SLOPE FACTOR OF SAFETY 4 FEET 1'/2: 1 0.74 JF W.O. 4799-A-SC SURFICIAL SLOPE STABILITY 11/2: 1 SLOPE Figure 5 section. Any future development of the site will require a stability analysis that demonstrates an adequate factor of safety from a regulatory standpoint. PRELIMINARY RECOMMENDATIONS - FOUNDATIONS General In the eventthat the information concerning the proposed development plan is not correct, or any changes in the design, location or loading conditions of the proposed structure are made, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and conclusions of this report are modified or approved in writing by this office. The information and recommendations presented in this section are not meant to supercede design by the project structural engineer or civil engineer specializing in structural design. Upon request,GSI could provide additional input/consultation regarding soil parameters, as related to foundation design. Drilled Pier and Grade Beam Foundation Recommendations The existing residence should be underpinned and supported by drilled, cast-in-place, concrete piers. All drilled piers should extend through the existing terrace deposits and be embedded at least 5 feet into the Torrey Sandstone Formation. Actual pier layout and embedment should be finalized by the project's structural engineer. The structural strength of the piers should be checked by the structural engineer or civil engineer specializing in structural analysis. Pier holes should be drilled straight and plumb. Locations (both plan and elevation) and plumbness should be the contractors responsibility. Grade beams should be at a minimum of 24 inches by 24 inches in cross section and supported by drilled caissons 24 inches in diameter which are placed at a maximum spacing of 6 feet on center, at beam intersections, and at critical settlement-sensitive locations within the structure's footprint. The structural mat slab should be constructed in accordance with the recommendations provided above but without the perimeter footings. The design of the grade beam and caissons should be in accordance with the recommendations of the project structural engineer,and utilize the following geotechnical parameters: Creep Zone: 5-foot vertical zone below the slope face and projected upward parallel to the slope face. Mr. Bill Geierman W.O. 4799-A-SC 520 4"'Street, Encinitas November 29, 2005 File:e:\wpl2\4700\4799a.rpge Page 19 GeoSoils, Inc. Creep Load: The creep load projected on the area of the grade beam should be taken as an equivalent fluid approach, having a density of 60 pcf. For the caisson, it should be taken as a uniform 900 pounds per linear foot of caisson's depth, located above the creep zone. Passive Resistance Passive earth pressure of 500 pcf per foot of caisson depth, to a maximum value of 5,000 psf may be used to determine caisson depth and spacing, provided that they meet or exceed the minimum requirements stated above. Point of Fixity The point of fixity should be located at a distance equivalent to one-third of the caissons length below the bottom of the grade beam. Allowable Axial Capacity A shaft capacity of 400 psf should be applied over the surface area of the shaft located in bedrock only. The tip capacity should be 6,000 psf. Caisson Construction a. The excavation and installation of the drilled caissons should be observed and documented by the project geotechnical engineer to verify the recommended depth. b. The drilled holes should be cased, specifically below the water table to prevent caving. The bottom of the casing should be at least 4 feet below the top of the concrete as the concrete is poured and the casing is withdrawn. Dewatering may be required for concrete placement if significant seepage or groundwater is encountered during construction. This should be considered during project planning. The bottom of the drilled caisson should be cleared of any loose or soft soils before concrete placement. C. The exact depths of caissons should be determined during the final precise grading plan review. d. Proper slump concrete should be used and should be delivered through tremie pipe. We recommend that concrete be placed through the tremie pipe immediately subsequent to approved excavation and steel placement. Due to the proximity of a saline environment and the uplifted marine terrace that the property is located upon, Type V concrete should be considered. Care should be taken to prevent striking the walls of the excavations with the tremie pipe during concrete placement. Mr.Bill Geierman W.O. 4799-A-SC 520 4"'Street, Encinitas November 29, 2005 Re:e:\wp12\4700\4799a.rpge GeoSoils, Inc. Page 20 e. All footing excavations should be inspected and approved by the geotechnical consultant prior to placement of concrete forms and reinforcement. f. Drilled pier steel reinforcement cages should have spacers to allow for a minimum spacing of steel from the side of the pier excavation. g. During pier placement, concrete should not be allowed to free fall more than 5 feet. h. Concrete used in the foundation should be tested by a qualified materials testing consultant for strength and mix design. Drilled Pier and Grade Beam Foundation Settlement Drilled pier and grade beam foundations should be designed to accommodate'/2 inch over a 40-foot horizontal span. Corrosion and Concrete Mix Upon completion of earthwork and prior to placing reinforcement steel, metal piping, concrete, etc., laboratory testing should be performed of site materials for corrosion to concrete and corrosion to steel. Additional comments may be obtained from a qualified corrosion engineer at that time. DEVELOPMENT CRITERIA Drainage Adequate lot surface drainage is a very important factor in reducing the likelihood of adverse performance of foundations, hadscape,and slopes. Surface drainage should be sufficient to prevent ponding of water anywhere on a lot,and especially near structures and tops of slopes/coastal bluff. Lot surface drainage should be carefully taken into consideration during fine grading,landscaping,and building construction. Therefore,care should be taken that future landscaping or construction activities do not create adverse drainage conditions. Positive site drainage within the lot should be provided and maintained at all times. Drainage should not flow uncontrolled down any descending slope/coastal bluff. Water should be directed away from foundations and not allowed to pond and/or seep into the ground. In general, the area within 5 feet around a structure should slope away from the structure. We recommend that unpaved lawn and landscape areas have a minimum gradient of 1 percent sloping away from structures, and whenever possible, should be above adjacent paved areas. Consideration should be given to avoiding construction of planters adjacent to structures (buildings, pools, spas, etc.). Pad drainage should be directed toward the street or other approved area(s). Although not a geotechnical requirement, roof gutters, down spouts,or other appropriate means may be Mr.Bill Geierman W.O. 4799-A-SC 520 a Street, Encinitas November 29, 2005 F1e:e:\wp12\4700\4799a.rpge Page 21 GeoSo>tis, Inc. utilized to control roof drainage. Down spouts, or drainage devices should outlet a minimum of 5 feet from structures or into a subsurface drainage system. Areas of seepage may develop due to irrigation or heavy rainfall, and should be anticipated. Minimizing irrigation will lessen this potential. If areas of seepage develop, recommendations for minimizing this effect could be provided upon request. Erosion Control Onsite earth materials have a moderate to high erosion potential. Consideration should be given to providing hay bales and silt fences for the temporary control of surface water, from a geotechnical viewpoint. Landscape Maintenance Only the amount of irrigation necessary to sustain plant. life should be provided. Over-watering the landscape areas will adversely affect proposed site improvements. We would recommend that any proposed open-bottom planters adjacent to proposed structures be eliminated for a minimum distance of 10 feet. As an alternative, closed-bottom type planters could be utilized. An outlet placed in the bottom of the planter,could be installed to direct drainage away from structures or any exterior concrete flatwork. If planters are constructed adjacent to structures, the sides and bottom of the planter should be provided with a moisture barrier to prevent penetration of irrigation water into the subgrade. Provisions should be made to drain the excess irrigation water from the planters without saturating the subgrade below or adjacent to the planters. Graded slope areas should be planted with drought resistant vegetation. Consideration should be given to the type of vegetation chosen and their potential effect upon surface improvements(i.e., some trees will have an effect on concrete flatwork with their extensive root systems). From a geotechnical standpoint leaching is not recommended for establishing landscaping. If the surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent minimum relative compaction. Gutters and Downspouts As previously discussed in the drainage section,the installation of gutters and downspouts should be considered to collect roof water that may otherwise infiltrate the soils adjacent to the structures. If utilized, the downspouts should be drained into PVC collector pipes or other non-erosive devices (e.g., paved swales or ditches; below grade,solid tight-lined PVC pipes; etc.),that will carry the water away from the house,to an appropriate outlet, in accordance with the recommendations of the design civil engineer. Downspouts and gutters are not a requirement; however, from a geotechnical viewpoint, provided that positive drainage is incorporated into project design (as discussed previously). Mr. Bill Geierman W.O. 4799-A-SC 520 e Street, Encinitas November 29, 2005 He:e:\wp12\4700\4799a.rpge Page 22 GeoSoils, Inc. Subsurface and Surface Water Subsurface and surface water are not anticipated to affect site development, provided that the recommendations contained in this report are incorporated into final design and construction and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Perched groundwater conditions along zones of contrasting permeabilities may not be precluded from occurring in the future due to site irrigation,poor drainage conditions, or damaged utilities, and should be anticipated. Should perched groundwater conditions develop,this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions. Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors. Site Improvements If in the future, any additional improvements (e.g., pools, spas, etc.) are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. Pools and/or spas should not be constructed without specific design and construction recommendations from GSI, and this construction recommendation should be provided to the homeowner and/or other interested parties. This office should be notified in advance of any fill placement, grading of the site, or trench backfilling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills, flatwork, etc. Additional Grading Any grading necessary to complete the project should be performed in accordance with the 1997 UBC and other applicable codes and ordinances. This office should be notified in advance of any fill placement, supplemental regrading of the site, or trench backfilling after rough grading has been completed. This includes completion of grading in the street, driveway approaches, driveways, parking areas, and utility trench and retaining wall backfills. Pier Excavation All pier excavations should be observed by a representative of this firm subsequent to trenching and prior to concrete form and reinforcement placement. The purpose of the observations is to evaluate that the excavations have been made into the recommended bearing material and to the minimum widths and depths recommended for construction. Excavation spoil and any excess soils generated from utility trench excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Mr. Bill Geierman W.O.4799-A-SC 520 4'Street, Encinitas November 29, 2005 He:eAwp12\4700\4799a.rpge Page 23 GeoSoiis, Inc. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING We recommend that observation and/or testing be performed by-GSI at each of the following construction stages: • During grading/recertification. • During excavation. • During placement of subdrains, toe drains, or other subdrainage devices, prior to placing fill and/or backfill. • After excavation of building footings, retaining wall footings,and free standing walls footings, prior to the placement of reinforcing steel or concrete. • Drilling of piles and piers. • Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other flatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor barriers (i.e., visqueen, etc.). • During retaining wall subdrain installation, prior to backfill placement. • During placement of backfill for area drain, interior plumbing, utility line trenches, and retaining wall backfill. • During slope construction/repair. • When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance of this report. When any developer or homeowner improvements, such as flatwork, spas, pools, walls, etc., are constructed, prior to construction. • A report of geotechnical observation and testing should be provided at the conclusion of each of the above stages, in order to provide concise and clear documentation of site work, and/or to comply with code requirements. GSI should review project sales documents to the homeowner for geotechnical aspects, including irrigation practices, the conditions outlined above, etc., prior to any sales. At that stage, GSI will provide homeowners maintenance guidelines which should be incorporated into such documents. Mr. Bill Geierman W.O.4799-A-SC 520 a Street, Encinitas November 29, 2005 Fle:e:\wp12\4700\4799a.rpge Page 24 GeoSoils, Inc. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer,structural engineer, post-tension designer,architect, landscape architect, wall designer, etc., should review the recommendations provided herein, incorporate those recommendations into all their respective plans, and by explicit reference, make this report part of their project plans. This report presents minimum design criteria for the design of slabs,foundations and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer/designer. Please note that the recommendations contained herein are not intended to preclude the transmission of water or vapor through the slab or foundation. The structural engineer/foundation and/or slab designer should provide recommendations to not allow water or vapor to enter into the structure so as to cause damage to another building component, or so as to limit the installation of the type of flooring materials typically used for the particular application. The structural engineer/designer should analyze actual soil-structure interaction and consider, as needed, bearing, expansive soil influence, and strength, stiffness and deflections in the various slab, foundation, and other elements in order to develop appropriate, design-specific details. As conditions dictate, it is possible that other influences will also have to be considered. The structural engineer/designer should consider all applicable codes and authoritative sources where needed. If analyses by the structural engineer/designer result in less critical details than are provided herein as minimums,the minimums presented herein should be adopted. It is considered likely that some, more restrictive details will be required. If the structural engineer/designer has any questions.or requires further assistance, they should not hesitate to call or otherwise transmit their requests to GSI. In order to mitigate potential distress, the foundation and/or improvement's designer should confirm to GSI and the governing agency,in writing,that the proposed foundations and/or improvements can tolerate the amount of differential settlement and/or expansion characteristics and other design criteria specified herein. PLAN REVIEW Final project plans(grading,precise grading,foundation,retaining wall,landscaping,etc.), should be reviewed by this office prior to construction, so that construction is in accordance with the conclusions and recommendations of this report. Based on our review, supplemental recommendations and/or further geotechnical studies may be warranted. Mr. Bill Geierman W.O. 4799-A-SC 520 4"'Street, Encinitas November 29, 2005 F1e:e:\wp12\4700\4799a.rpge Page 25 GeoSoiils, Inc. LIMITATIONS The materials encountered on the project site and.utilized for our analysis are believed representative of the area; however,soil and bedrock materials vary in character between excavations and natural outcrops or,conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. All samples will be disposed of after 30 days, unless specifically requested by the client, in writing. Mr. Bill Geierrnan W.O. 4799-A-SC 520 4"'Street, Encinitas November 29, 2005 F1e:eAwp12\4700\4799a.rpge i Page 26 GeoSols, Inc. APPENDIX A REFERENCES APPENDIX A REFERENCES Bird, Eric C.F., 1985, Coastline changes, a global review: John Wiley and Sons. Blake, T.F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version. 2000b, EQSEARCH, A computer program for the estimation of peak horizontal acceleration from California historical earthquake catalogs; Updated to April,2004, Windows 95/98 version. 2000c, FRISKSP, A computer program for the probabilistic estimation of peak acceleration and uniform hazard spectra using 3-D faults as earthquake sources; Windows 95/98 version. Bozorgnia, Y., Campbell, K.W., and Niazi, M., 1999, Vertical ground motion: Characteristics, relationship with horizontal component, and building-code implications; Proceedings of the SMIP99 seminar on utilization of strong-motion data, September, 15, Oakland, pp. 23-49. Campbell, K.W. and Bozorgnia, Y. 1997, Attenuation relations for soft rock conditions; in EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-D fault sources; Windows 95/98 version, Blake, 2000a. Curray,J.R., 1965,Late Quaternary history;continental shelves of the United States,p.723- 735 in H.E. Wright, Jr. and D.G. Frey (eds), The Quaternary of the United States, Princeton University Press, 922 p. 1961, Late Quaternary sea level: a discussion, Geological Society of America Bulletin 72, p. 1707-12. 1960, Sediments and history of 'Holocene transgression, continental shelf, northwest Gulf of Mexico, p. 221-266, in F.P. Shepard, F.B. Phlefer, and Tj. H. van Andel (eds), Recent Sediments, Northwest Gulf of Mexico, 1951-1958, American Association of Petroleum Geologists, Tulsa, Oklahoma, 394 p. Emery, K.O. and Aubrey, D.G., 1991, Sea levels, land levels, and tide gauges: Springer- Verlag Publishers, New York, NY, 237 p., 113 figures. Emery, K.O. and Kuhn, G.G., 1982, Sea cliffs: their processes, profiles, and classification: Geological Society of America Bulletin, v. 93, no 7. 1980, Erosion of rock shores at La Jolla, California, in Marine Geology, v. 37. GeoSoils, Inc. Fisher, P.J., and Mills, G.I., 1991, The offshore Newport-Inglewood - Rose Canyon fault zone, California: structure, segmentation, and tectonics, in Abbot, P.L., and Elliott, W.J., eds., Environmental perils - San Diego region, published by San Diego Association of Geologists. Hart, E.W. and Bryant,W.A., 1997, Fault-rupture hazard zones in California,Alquist-Priolo earthquake fault zoning act with index to earthquake fault zones maps; California Division of Mines and Geology Special Publication 42, with Supplements 1 and 2, 1999. Inman, D.L., 1976, Summary report of man's impact on the California coastal zone; prepared for the Department of Navigation and Ocean Development, State Of California. Inman, D.L. and Veeh, H.H., 1966, Dating the 10-fathom terrace off Hawaii, American Geophysical Union, Trans. 47, 1.25. International Conference of Building Officials, 1997, Uniform building code: Whittier, California. Kennedy, M.P., 1975, Geology of the San Diego metropolitan area, California; California Division of Mines and Geology, Bulletin 200, Section A, Western San Diego Metropolitan Area, Del Mar, La Jolla, and Point Loma, 71/2 minute quadrangles. Kern. J.P., 1977, Origin and history of upper Pleistocene marine terraces, San Diego California, Geological Society of American Bulletin 88. Kuhn, G.G.,and Shepard, F.P., 1984, Sea Cliffs, beaches and coastal valleys of San Diego County: some amazing histories and some horrifying implications: University of California Press, Berkeley, California, and London, England. 1980 Coastal erosion in San Diego County, California, in Edge, B.L., ed., Coastal Zone'80, Proceedings of second Symposium on Coastal and Ocean Management held in Hollywood, Florida, on 17-20 November, 1980: American Society of Civil Engineers, V. III. Legg, M.R., and Kennedy, M.P., 1991, Oblique divergence and convergence in the California Continental Borderland, in Abbott, P.L., and Elliott, W.J., eds., Environmental perils - San Diego region, published by San Diego Association of Geologists. Leighton and Associates, Inc., 1990, Geotechnical investigation, proposed second-story addition, 5366 Calumet Avenue, San Diego, California, project no. 4900617-01, dated May 31. Mr. Bill Geierman Appendix A R1e:e:\wp1214700\4799a.pge Page 2 GeoSoiills, Inc. Lindvall, S.C., Rockwell, T.K., and Lindvall, E.C., 1989, The seismic hazard of San Diego revised: new evidence for magnitude 6+ Holocene earthquakes on the Rose Canyon fault zone, in Roquemore, G., ed., Proceedings, workshop on "the seismic risk in the San Diego region: special focus on the Rose Canyon fault system." Masters, P.M., and Fleming, N.C., 1983, Quaternary coastlines and marine archaeology: towards the prehistory of land bridges and continental shelves: Academic Press, New York, 641 p. Matti,J.C., Morton, D.M.,and Cox., B.F., 1992,The San Andreas fault system in the vicinity of the central Transverse Ranges province, southern California, in Sieh, K.E., and Matti, J.C., eds., Earthquake geology San Andreas fault system Palm Springs to Palmdale,guidebook and reprint volume,prepared for 35'annual meeting,October 2-9, 1992, Long Beach, California, Association of Engineering Geologists. Matti, J.C., and Morton, D.M., 1993, Paleogeographic evolution of the San Andreas fault in southern California: A reconstruction based on a new cross-fault correlation, in Powell, R.E., Weldon, R.J. II, and Matti, J. C., eds.,The San Andreas Fault System: Displacement, Palinspastic Reconstruction, and Geologic Evolution: Geological Society of America Memoir 178, pp 107 - 159. Shakelton, N.J., and Opdyke, N.D., 1976, Oxygen - isotope and paleomagnetic stratigraphy of Pacific core V28-239, late Pliocene to Latest Pleistocene, Geological Society of America, Memoir 145. Sowers and Sowers, 1979, Unified soil classification system (After U. S. Waterways Experiment Station and ASTM 02487-667)in Introductory soil mechanics,New York. Sylvester, A.G., 1988, Strike slip faults in Geological Society of America Bulletin, v. 100, p. 1666-1703. Treiman, J.A., 1984,The Rose Canyon fault zone, a review and analysis, published by the California Department of Conservation,Division of Mines and Geology,cooperative agreement EMF-83-k-0148. Trenhaile, A.S., 1987, The geomorphology of rock coasts: Clarendon Press, Oxford. US Army Corps of Engineers, 1996, Reconnaissance report, Encinitas shoreline, San Diego County, California, dated March. Mr. Bill Geierman Appendix A R1e:e:\wp12\4700\4799a.pge Page 3 GeoSoiils, Inc. APPENDIX B BORING LOG UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY Major Divisions Group Typical Names CRITERIA Symbols Well-graded gravels and gravel- (D sand mixtures,little or no fines Standard Penetration Test c m `o c - 0 Poorly graded gravels and Penetration > N o GP gravel-sand mixtures,little or no Resistance N Relative E z fines (blows/ft) Density °o m y a O � -0 Silty gravels gravel-sand-silt 0-4 Very loose o z ,°o o c m GM mixtures -0 c i° 3 4-10 Loose -0 0'a `� Clayey gravels,gravel-sand-clay c GC mixtures 10-30 Medium CS•� ai c Well-graded sands and gravelly 30-50 Dense 0 o m c m SW sands,little or no fines U _ a m m e iQ o c o .y v to >50 Very dense U) '6 `n a SP Poorly graded sands and m v c R o gravelly sands,little or no fines o � t m Z 2 m m o h SM Silty sands,sand-silt mixtures ca v, N E U o- 0 3 u_ SC Clayey sands,sand-clay mixtures Inorganic silts,very fine sands, Standard Penetration Test ML rock flour,silty or clayey fine N sands m " Unconfined >>i E m Inorganic clays of low to Penetration Compressive a o medium plasticity,gravelly clays Resistance N Strength C) CO o sandy clays,silty clays,lean (blows/ft) Consistency (tons/ft) U) a -J Lo clays � `U, Organic silts and organic silty <2 Very Soft <025 C uz OL clays of low plasticity R 2-4 Soft 0.25-050 d) N Inorganic silts,micaceous or c O MH diatomaceous fine sands or silts, 4-8 Medium 0.50-1.00 E >,:t-_ C. elastic silts Lc 8-15 1 Stiff 1.00-2,00 off° U E 05 u°s v Inorganic clays of high plasticity, CH fat clays 15-30 Very Stiff 2.00-4.00 N CO `° rn OH Organic clays of medium to high >30 Hard >4.00 plasticity Peat,mucic,and other highly Highly Organic Soils PT organic soils 3" 3/4" #4 #10 #40 #200 U.S.Standard Sieve i I Unified Soil Cobbles Gravel Sand Silt or Clay Classification coarse fine coarse medium fine I MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS Dry Absence of moisture:dusty,dry to the touch trace 0-5% C Core Sample Slightly Moist Below optimum moisture content for compaction few 5-10% S SPT Sample Moist Near optimum moisture content little 10-25% B Bulk Sample Very Moist Above optimum moisture content some 25-45% T Groundwater Wet Visible free water;below water table Qp Pocket Penetrometer BASIC LOG FORMAT: Group name,Group symbol,(grain size),color,moisture,consistency or relative density. Additional comments:odor,presence of roots,mica,gypsum, coarse grained particles,etc. EXAMPLE: Sand(zSP),fine to medium grained,brown,moist,loose,trace silt,little fine gravel,few cobbles up to 4"in size,some hair roots and rootlets. 9Ie:Mgr: c;\SoilClassif.wpd PLATE B-1 BORING LOG GeoSoils, Inc. WO. 4799-A-SC PROJECT.•MR. BILL GEIERMAN BORING B-1 SHEET 1 OF 2 520 4th Street, Encinitas DATE EXCAVATED 6-13-05 Sample SAMPLE METHOD: Hollow Stem Auger/California Sampler _ a Standard Penetration Test 0 0 m E �Z Groundwater j m o ® Undisturbed,Ring Sample c 3 T a�i c o ai o m ❑ m D in :3 ❑ � v, Description of Material sM TERRACE DEPOSITS: @ 0'SILTY SAND, dark brown, moist, loose; many roots. s: 5 31 114.5 3.6 21.5 @ 5'SILTY SAND, brown,slightly moist, medium dense. �. 10 _ s: 15 20 48 SP 3.3 @ 20'SAND w/SILT, light brown, slightly moist, dense. 25 5204th Street, Encinitas GeoSoils, Inc. PLATE B-2 520 FourthStreet Date 10-09-06 Hydrology Study WO# 5045 I ,f � IAN 31 2007 ".__ Y Hydrology Study 520 Fourth Street Encinitas CA Prepared for City of Encinitas Permit No-06-229 w a N..368 73 r m � Exp. 6.30- CF CAt�F Date: 10-09-06 Rev. 1-15-07 Prepared by Lintvedt, McColl & Associates 2810 Camino Del Rio South, Suite 200 San Diego, Ca 92108 (619) 294-4440 520 Fourth Street Date: 1-15-07 Hydrology Study WO#5045 TABLE OF CONTENTS VICINITYMAP.....................................................................................................3 INTRODUCTION...................................................................................................4 PURPOSEAND SCOPE.........................................................................................4 EXISTINGCONDITIONS ........................................................................................5 PROPOSEDCONDITIONS .....................................................................................6 METHODOLOGY AND CALCULATIONS ....................................................................7 CONCLUSIONS & RECOMMENDATIONS ..................................................................7 WORKSCITED ...................................................................................................8 APPENDIX ......................................................................................................0 a. Hydrology Calculations b. Hydrology Maps c. Soil Map d. Rainfall Isopluvial Maps e. Tank and Pump Capacity Calculations f. Pipe and Inlet Capacity Charts 2 520 Fourth Street Date: 1-15-07 Hydrology Study WO# 5045 Vicinity Map MAS N SITE 'G �Q �n T n n� ti VICINITY MAP 3 520 Fourth Street Date: 1-15-07 Hydrology Study WO#5045 Introduction The project consist of one existing single family home on a 6,600 square foot lot on the bluff just south of Moonlight Beach in the City of Encinitas. The property is located approximately 200 feet south of D Street. It is accessed via a 10-foot wide panhandle from Fourth Street. Runoff from the westerly portion of the site drains directly to the Pacific Ocean. Runoff from the roof top and panhandle driveway drains to Fourth Street. A mid bluff retention system is being be constructed to stabilize the existing home Purpose and Scope The existing home was constructed in the early 1950s. Historically the surface runoff from the decks and walkways surrounding the home was allowed to drain over the bluff to the beach below. As part of the mid-bluff retention project, an underground storm drain system will be constructed to redirect the surface runoff to Fourth Street in order to minimize the erosion potential to the bluff. The storm drain system will include an under ground conduit, storage tank and pumps. The purpose of this study is to provide surface runoff calculations and sizing of the storm drain system. Runoff calculations are limited to the site itself. 4 520 Fourth Street Date: 1-15-07 Hydrology Study WO#5045 Existing Conditions The project site is approximately 6,600 square feet in size and is located on the bluff just south of Moonlight Beach. The developed portion of the site including the existing home, walk way and patios comprise approximately 3,600 square feet of impervious surface. A portion of the home and decks were removed as a condition of the Coastal Commission Emergency permit. The impervious area addressed in this report is the area remaining as of this date. The existing home is set back approximately 150 feet from Fourth Street and is accessed via a 10 foot wide panhandle. The easterly eighty feet of the panhandle surface drains to Fourth Street. The westerly portion of the panhandle and all of the building pad area are below the grade of Fourth Street. Surface runoff from the decks and walkways has historically drained over the bluff to the beach below. Remnants of a private drainage system that conveyed runoff beyond the steepest part of the bluff still exist. They have been severed due to movement of the surface materials on the bluff. A roof drainage system conveys the building runoff to the northeast corner of the building where it is discharged to a gravity pipe system mounted on the existing masonry screen wall along the northerly property line. The pipe system outlets to the panhandle driveway and surface drains to Fourth Street. Existing curb and gutter conveys runoff in Fourth Street in a northerly direction. 5 520 Fourth Street Date: 1-15-07 Hydrology Study WO# 5045 Proposed Conditions In order to minimize the erosion potential to the bluff, the surface runoff from the building decks and walk ways will be redirected to the Fourth Street. Surface runoff conveyed to Fourth Street will flow via existing gutters to the public storm drain system. The proposed storm drain system consists of an underground pipe system, storage tanks and pumps. The panhandle driveway will be reconstructed to provide a consistent 1% grade to Fourth Street. The easterly eighty feet of the driveway will continue to surface drain to Fourth Street. A series of drains and catch basins will convey runoff from the decks and walkways to a holding tank near the northeast corner of the home. The existing roof gutter system will continue to outlet at the northeast corner of the home, but will be directed to the new holding tank to eliminate the pipe system mounted on the wall. A volume of runoff equivalent to the first .6 inch of rainfall (1,000 gallons) will be stored and used for irrigation. A dual pump system will be provided to pump excess flows to Fourth Street at a rate equal to the 100 year peak flow or 225 GPM. Each pump is sized to handle the flow independently of the other. s 520 Fourth Street Date: 1-15-07 Hydrology Study WO#5045 Methodology and Calculations The hydrology calculations were prepared in accordance with the County of San Diego Drainage Design Manual dated June 2003. Base maps were prepared to define the basin areas using the project topographic mapping and proposed grading plan. Flow rates were calculated using the rational method, Q=CIA, with `C' being the runoff coefficient, `I' being the intensity, and `A' being the drainage area in acres. The 'C' values used in this study for the developed area have been increased to 0.95 to reflect the amount of impervious surface. The intensities are calculated based on the County of San Diego Hydrology Manual where I = 7.44 P6D-o.145 P6 is the 6 hour precipitation in inches and D is the Time of Concentration of the storm in minutes. The drainage basins studied are very small, there fore a minimum Time of Concentration equal to five minutes has been assumed for all basins and sub-basins. All of the sub-basins within the study area are very small and produce low peak rates of runoff. A minimum size catch basin of 12"x12"" will be used. A minimum pipe size of 4" at a minimum slope of 1% will be used. Sizing charts are provided pipes an catch basins. All capacities exceed the demands within the study area. Conclusions & Recommendations The total impervious area has decreased slightly as a result of the project because a portion of the existing home and decks were removed. The drainage pattern and peak rate of runoff 520 Fourth Street Date: 1-15-07 Hydrology Study WO# 5045 from the existing panhandle driveway will remain the same as the existing condition. The historical flow pattern for portions of the site was directly to the Beach. Redirecting the flow to the public street will be mitigated by the use of on site detention. Without detention, there would have been a slight increase in the 100 year peak rate of runoff of approximately 0.1 CFS. Use of on site detention will decrease the peak rate of runoff for low volume storms to a level below the existing condition. The project will be provide a 1,000 gallon storage tank to collect runoff from the roof and deck areas and store for later irrigation use. The storage tank is sized to detain a volume equal to the first flush runoff (0.6 inch). During low volume storms all of the runoff will remain on site, thereby decreasing both the peak rate of runoff and total volume of runoff tributary to Fourth Street. During higher volume storms, runoff exceeding the volume of the storage tank will be pumped to Fourth Street.. A 20 foot long bio-swale will be provided at the outlet to Fourth Street to filter storm runoff before leaving the site. Works Cited Brater and King. Handbook of Hydraulics, Sixth Edition. Pages 6-14 - 6-16. McGraw-Hill, Inc. 1976. County of San Diego. Drainage Design Manual. s Fourth Street Date: 1-15-07 Hydrology Study WO#5045 APPENDIX Fourth Street Date: 1-15-07 Hydrology Study WO#5045 HYDROLOGY CALCULATIONS PAGE NO: 1 DATE: 09/02/06 W.O.#: 5045.000 CALC'D BY: PM CHECKED BY: PM BASIN MAP TITLE: 520 Fourth Street Existing Conditions BASIN MAP DATE: 520 Fourth Street Proposed Conditions LINTVEDT,McCOLL,&ASSOCIATES 100 Year Runoff Calculations BASIN I.D. AREA(ACRE) RUNOFF COEF. Tc P 6 hour 1Wear Storm 100 yr INTENSITY DESTIN-ATION BASIN O Ids) TOTAL Q(cfs) EXISTING CONDITIONS 0,019 0,9 5.0 1.14 7.9 A 0.143 0.143 enln'a 0. 5.0 J.14 7.9 Ch _ 0.225 0.225 0,032 0A 5.0 114_ 7.9 0.240 0.240 TONAM 0M 0.608 T A1-` A+` C 0.383 T_. 1 PROPOSED CONDITIONS t11 , ,,, 5.0 1,14 7.9 41KSNM 0.143 0.143 D. 5.0 1 7.9 0.165 0.165 5.0 1.14 7.9 QdWVJW 0.068 0.068 BaSM S-3 U. 5.0 1. 7.9 0.023 0.023 5.0 1.14 7.9 0.203 0.203 T 0.600 ToOd ftw to t�tar&n Sulu 9-+Sulin C 0.458 Calculations in this table are based on the Rational Method with the following formulas 1 Q=CIA=Runoff Coefficient'Intensity'Area Runoff Coefficient"C:is based on the County of San Diego Hydrology Manual. See Appendix for County Chart and Basin 2 breakdown by development type. Time of Concentration(Tc)for Urban Areas Overland Flow is based on the formula in the County of San Diego Drainage 3 Manual Chart. Tc=(1.8(1.1-C)D1/2/S1/3) Time of Concentration(Tc)for Overland flow-Natural is based on the formula in the County of San Diego Drainage Manual 4 Chart. Tc=(11.9 L3/H)0.385 Time of Concentration(Tc)for Gutter Flow,Ditch Flow and Pipe Flow is based on Tc=Travel Length\Velocity where velocity 5 is estimated based on slope. P 6 Hour storm is taken from the County of San Diego Drainage Manual Isopluvial Maps for the Design Storm. See copy in 6 Appendix 7 Intensity(1)is based on the formula in the County of San Diego Hydrology Manual I=7.44(P6)D-.645 100 Year Hydrology PAGE NO: 1 DATE: 09102/06 W.O.#7. 5045.000 CALC'D BY: PM CHECKED BY: PM BASIN MAP TITLE: 520 Fourth Street Existing Conditions BASIN MAP DATE: 520 Fourth Street Proposed Conditions LINTVEDT,McCOLL,&ASSOCIATES 10 Year Run-"Calculations BASIN I.D. AREA(ACRE) RUNOFF COEF. Tc P 6 hour 10 Year Storm 10 yr INTENSITY DESTIN-ATION BASIN Q(cfs) TOTAL Q(cfs) EXISTING CONDITIONS Basin A 0,1019 &W 5.0 1, 4.5 AM She 0.081 0.081 Bosky B VAX 0195 5.0 1.14 4.5 Ono 0.128 0.128 Basin C . 0.032 0,95 5.0 11 4.5 0.137 0.137 TOW AM 0.346 T m.stab A- * C 0.218 PROPOSED CONDITIONS A 5.0 ; 4 4.5 0.081 0.081 1 5.0 4.5 0.094 0.094 nosmis--2 0300 Us, 5.0 1 4 4.5 powan 0.038 0.038 Basin W3 0=1 5.0 1.14 4.5 0.013 0.013 Basin C 0-gy 0M 5.0 1.14 4.5 0.115 0.115 .12W A njaaa 0.080 0.342 TOW to Dstentlon=Basin B}Basin C 0.261 100 Calculations in this table are based on the Rational Method with the following formulas 1 Q=CIA=Runoff Coefficient'Intensity'Area Runoff Coefficient"C:is based on the County of San Diego Hydrology Manual. See Appendix for County Chart and Basin 2 breakdown by development type. Time of Concentration(Tc)for Urban Areas Overland Flow is based on the formula in the County of San Diego Drainage 3 Manual Chart. Tc=(1.8(1.1-C)D1/2/S1/3) Time of Concentration(Tc)for Overland flow-Natural is based on the formula in the County of San Diego Drainage Manual 4 Chart. Tc=(11.9 L3/H)0.385 Time of Concentration(Tc)for Gutter Flow,Ditch Flow and Pipe Flow is based on Tc=Travel Length\Velocity where velocity 5 is estimated based on slope. P 6 Hour storm is taken from the County of San Diego Drainage Manual Isopluvial Maps for the Design Storm. See copy in 6 Appendix 7 Intensity(1)is based on the formula in the County of San Diego Hydrology Manual I=7.44(P6)D-.645 10 Year Hydrology PAGE NO: 1 DATE: 09/02/06 W.O.#: 5045.000 CALC'D BY: PM CHECKED BY: PM BASIN MAP TITLE: 520 Fourth Street Existing Conditions BASIN MAP DATE: 520 Fourth Street Proposed Conditions LINTVEDT,McCOLL,&ASSOCIATES 2 Yew Runoff Calculations BASIN I.D. AREA(ACRE) RUNOFF COEF. Tc P 6 hour 2 Year 2 yr INTENSITY DESTIN-ATION BASIN Q(cfs) TOTAL Q Ida) Storm EXISTING CONDITIONS A 0.019 0195 5.0 114 3.0 -41h 0.054 0.054 0.030, 0196 5.0 1.14 3.0 Basch 0.086 0.086 Soon C 0= S 5.0 114 3.0 0.091 0.091 TWA! 0 0.231 T bo 4&ftvst ap Basin A f Best C 0.145 TOW I 0:, PROPOSED CONDITIONS 6,01 M Basin A 5.0 114 3.0 441 SkW 0.054 0.054 1 5.0 v 1,14 3.0 Dmalowi 0.063 0.063 5.0 1,114 3.0 0.026 0.026 saiin&3 0A w 0.95 5.0 1.1 14, 3.0 0.009 0.009 Basin C, 0,02-1 5.0 1.1 3.0 041014M 0.077 0.077 T 0.228 aaaaaaaaaj� Total flow to Dstontlob a Basin B*Basin C 0.174 Calculations in this table are based on the Rational Method with the following formulas 1 Q=CIA=Runoff Coefficient`Intensity'Area Runoff Coefficient"C:is based on the County of San Diego Hydrology Manual. See Appendix for County Chart and Basin 2 breakdown by development type. Time of Concentration(Tc)for Urban Areas Overland Flow is based on the formula in the County of San Diego Drainage 3 Manual Chart. Tc=(1.8(1.1-C)D1/2/S1/3) Time of Concentration(Tc)for Overland flow-Natural is based on the formula in the County of San Diego Drainage Manual 4 Chart. Tc=(11.9 L3/H)0.385 Time of Concentration(Tc)for Gutter Flow,Ditch Flow and Pipe Flow is based on Tc=Travel Length\Velocity where velocity 5 is estimated based on slope. P 6 Hour storm is taken from the County of San Diego Drainage Manual Isopluvial Maps for the Design Storm. See copy in 6 Appendix 7 Intensity(1)is based on the formula in the County of San Diego Hydrology Manual I=7.44(P6)D-.645 2 Year Hydrology 520 Fourth Street Date 1-15-07 Hydrology Study WO# 5045 HYDROLOGY MAPS LEGEND: BASIN A BASIN NAME DIRECTION OF FLOW DRAINAGE BASIN Ili ii i a c� y CRES C.F. ". - � ' W W CC 3 0 rr 0 x Kai 5) r 10 0 10 30 Scale 1"=10' SHEET 1 OF 3 520 FOURTH STREET EXISTING CONDITIONS HYDROLOGY MAP CITY OF ENCINITAS DA1E71-7-06 w.a PbMS I DRrr-DF c"n Br.yr UnTVEDT, MoOOLL �„�,� fr A330CIATE3 . aio�Fe a m.seYm sin.zan sa w.w.a aeiae Ke+a)zw-ua sm(eie)ass-uaz LEGEND: BAS{N A BASIN NAME DIREC110N OF FLOW DRAINAGE BASIN ii I S W Ex I 11J BE II (n I O I U tir O I u- � v G� v 10 0 10 30 Scale 1"=10' SHEET 2 OF 3 520 FOURTH STREET PROPOSED CONDITIONS HYDROLOGY MAP CITY OF ENCINITAS DA1E11-7-OE 11L0,p5m DRFT:DF 0"er pm LUITVEDT, MoCOLL fr AS30CIATE3 ,, o , ma c�tio a me sdu.w�ma so.w.,,,u anm re,orn.-«w.�mtmo�ze.-«,: II I i SOURCE OF TOPOGRAPHY: THE EXISTING TOPOGRAPHY AND BOUNDARY SHOWN HEREON WAS TAKEN FROM THE 'TOPOGRAPHIC SURVEY, 520 FOURTH STREET, ENCINITAS, CA. 92041' PREPARED BY CIREMELE SURVEYING INC. DATED 8-1-05. REMOVE AND REPLACE tr - 13' OF CURB, GUTTER AND SIDEWALK, PER STANDARD DRAWING G-146. MATCH EXISTING q e GRADES EACH SIDE. u EXIST. DECKS TO # I IT TRENCH REPLACE EXISTING SEWER PER EMERGENCY +�i'' - _ LATERAL WITH THE ,L ,I ! PUBLIC RIGHT OF WAY. TYPIC 3 I � , O c r 31 FEN OB F PU BLIC C EXISTING CONDITIONS: :RENCE DRAWINGS. PROPERTY BOUNDARY INDEX CONTOUR z1 v 'MBOL INTERMEDIATE CONTOUR - - - EXISTING SEWER EXISTING STORM DRAIN --"- EXISTING WATER -"' "''� II _ •��=-rte EXISTING RETAINING WALL EXISTING SPOT ELEVATION �- l� BOTTOM STEP ., EXIS CONCRETE Y PER y° DRAIN INLET 1ABOL HIGH POINT Y,.. POWER POLE EXISTING MASONRY SCREEN WALL TOP STEP R EXISTING-FENCE WOOD FENCE FENCE � WATER METER 1" MA WATER VALVE x I 11 8 t 12' EXISTING x I RETAINING WALL/SEA WALL PER EMERGENCY 1X I PERMIT 6 7— I T DECORATIVE —REPLACE EXISTING DRIVEWAY ROCKS WIHT 4' PCC PAYING PER R.S.D. G18 WITH EXPOSED AGGREGATE SURFACE FINISH DECORATIVE ROCKS m FFORI SHEET 3 OF 3 GRASS PLANTED IN CHAT EASTERLY 20' WAn PAYI 520 FOURTH STREET A TYPICAL DRIVEWAY SECTION GRADING PLAN --- NOT TO SCALE CITY OF ENCINITAS DA1E11-15-06 IVLQP5045 I DWI'DF/MH I CHWD BY-PM 10 7 LinTVEDT, Mc LOLL Scale 1'=10' f! ASS 0 C I A T E 5 .,.,,o— a�a�ne or me sdm.nna m4 see w.w.a mm KeieY�w-ww rm{aa)ss�--uaz 520 Fourth Street Date 1-15-07 Hydrology Study WO# 5045 SOIL MAP bA M �. -. ► m ••} � `% a o M ` (4--J O w E 9Y> Q o a m v o ; O C? c7 c7 2 c2 U M o Imperial County Q sLSLL m _Of.9 L t _ � T l mss. . i . 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W.O.# Calc'd b Checked b 4 First Flush Runoff is equal to 0.6 inches Total volume to detain =Area X"C"X Depth of Rainfall\ 12 Basin Area Depth of Volume of Volume of SF "C"Factor Rainfall DetentionI CF Detention Gal 2800 0.95 0.60 133.0 984 Pump size for Peak 100 ear Flow=Q 100 (CFS)X 7.4 Gal/CF X 60 Sec/Min Pump Capacity Q 100(CFS) (GPM 0.5 222 Tank Capacty 520 Fourth Street Date 1-15-07 Hydrology Study WO# 5045 PIPE AND GRATE CAPACITY CALCULATIONS Pipe Capacity for Pipes Flowing Full 520 Fourth 56i4t . ., Date: W.O.#, 1. Calc'd b Checked b Q = (1.49/N)"A*(R--(2/3))"(S*".5) where: N =0.012 for PVC A=area of pipe R=hydraulic radius Pipe Size Inches Sloe Q Full cfs V Full (fps) 4 0.0075 0.18 2.1 4 0.01 0.21 2.4 4 0.02 0.29 3.4 6 0.005 0.43 2.2 6 0.0075 0.53 2.7 6 0.01 0.61 3.1 8 0.02 1.86 5.3 8 0.005 0.93 2.7 8 0.0075 1.14 3.3 8 0.015 1.61 4.6 10 0.02 3.36 6.2 10 0.0075 2.06 3.8 10 0.015 2.91 5.3 10 0.02 3.36 6.2 12 0.005 2.74 3.5 12 0.0075 3.35 4.3 12 0.015 4.74 6.0 15 0.02 9.92 8.1 15 0.005 4.96 4.0 15 0.01 7.01 5.7 15 0.01 7.01 5.7 24 0.02 34.74 11.1 24 0.05 54.92 17.5 30 0.04 89.07 18.2 36 0.04 144.83 20.5 36 0.01 72.42 10.2 36 0.025 114.50 16.2 48 0.02 220.55 17.6 Pipe Capacity Inlet Capacity 520 Fourth Street Date: ` ft W.O. #. . Calc'd by: Checked b Where QXP=3.0 H**3/2 Capacity with Depth (Inches) Grate size Max Capacity 50%of Inlet (Inches) (CFS) blocked (CFS 1 12 0.3 0.1 2 12 0.8 0.4 3 12 1.5 0.8 6 12 4.2 2.1 9 12 7.8 3.9 12 12 12.0 6.0 15 12 16.8 8.4 18 12 22.0 11.0 1 18 0.4 0.2 2 18 1.2 0.6 3 18 2.3 1.1 6 18 6.4 3.2 9 18 11.7 5.8 12 18 18.0 9.0 15 18 25.2 12.6 18 18 33.1 16.5 1 24 0.6 0.3 2 24 1.6 0.8 3 24 3.0 1.5 6 24 8.5 4.2 10 24 18.3 9.1 12 24 24.0 12.0 15 241 33.5 16.8 18 241 44.1 22.0 Inlet Capacity Calculations I tVl 1 t } j I r_-} i {_._ _ + E 4 _ , WN1 0 I ...v t _n .. . . ..- 1 is a P r . 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") [G 2:1ti-1171-45 Dal l 1 F .Ia € 1 3 € ( f ` 5 !)PS It ir' i I f € { - t E t 6. i 3 its I t t ,1 i € t 5 1 `I j E ! rt ( �,r ` i f- p _ ' l I f�`i t Ji ! `i t.3 ! i k[ fit€ 33 L:}. 4 t vV ."12 >>• , { ,_..i' _t 't i { t } j r:' �S � } �• t �''� It :..I i}t �t` V � .4'�'` - le , t ` r [t' fill '� `� itfF tYr' \Fl - • t t _ Li G� A n ` � � is MP a �' tI -P {yt j;., _a 3 � I € l tl. \ Jr ty 68YIg11' t��'./' 3 I - tSCAr"l��vN�.Y l I; (1 !' tt ,t ti �•,�{ \�'<J ( l I t t ! 1 (� { , ap,,,4t t, i Recent slump talus deposits ter; { a� ` S.` IS ' 1 E t l { I + 3 .J i '' t i z� l f,. .t '.j, fti i ' < .t i!, 3 I 1 i t i r`i 1 St y` I { 4 t`} it :.t 7' tS€ t($i:Y.'/' ,i' - r, ✓`d -t-rp t+.:its �Ify'` ff: i Recent beach deposits i n KF il" t"r 4si •••i YE t _ ,.,:r 3._,. .. _. l" tti t r, { i C: t :Vi .-r .I _ - 4 �—� — — - - Quaterna terrace d Daft _ _ w - C � l j t t 4 , { t , rat --- p - � — - - .. --,-- , - {i t t i 1 _ t , i t x :i ` ;t ._ _ , _ c t. i Torrey formation t°Tt4 -_,_... i -j - ,.l ! - - x "'1, r,Y ij tt tt 4 t_ i •.�..� �..�,�„ Approximate location of geologic contact Bedding attitude, with dip in ,i i ,...�' degrees j t ' t i�T, 1 : > � 4 Joint attitude, with dip in degree { Approximate location of - -- exploratory boring 1 i� xC t 10 MET l F�f st 1`.t e � ) Geologic cross section i i � trt i l ( i :,i • tit({ . ��:� LEGAL G -iL DE 3' . [�x�i, ill.t�� t i..• '-,,-. .€{- 1€,I , j .7k5(� ! ,tCl" t �"�` 'rf I 3 is �{y f )� L I I tt l i fir{ 14 AND T!1 oRift) rt t €' 3r_{ t O LCH 3, I{•; "{ (t [- - I '-n ,P 5_ [ s ri J t x __ __ eJi til�j.t�, i tiiF f - 1 Lt � ,, t Fj-- xC tf tt.:. e -,i i s 3! I€, III A • I E NCt41!it.S, ' r 1 t1. ^. ,3A1 EAU.! , f C -t ."A. All locations are approximate f i. t it Li._:'�: t CIE v. r.Lif iE:T . .-•^:itt ^�-_ e 'I:. {IISit (t:PYT_ll!€'.r ht �• :i'ilx }Ct .t.. _ •• , z ti AC F'"ii'i i f t "-() tl REI i { I f t.�€� C _ APN :\s� S.'.. {�rlt�€.tf.E_ eJi.€�:FtL!': 1 , -;,,,s v , RIVERSIDE CO, i E^�� i I— i f -'1Y ft€ - f. Fig:"",' 1 1 {.I .:.t.?!\i: POINT t I_3•. r-, ,t ! l tt.t i('t>i - s ue ' t € r i 1 4 -r S t IksS DISC t , IN ELL .�� in t t x at il3t€ Et .3.i u{ :., t ,�E ..t-. ;`MIIO fE.(I�.EN IN . 'ill # axi i 4�T i C)1-•, tT i_E PO I1,(_ R i(" �TFE' • ORANR&CO.f CStdC t t, 'i€ ,* SAN DIEGO CO. t IEt 1 .. yISII, I.t i*l ti il.V'_. €0o FEE 'N."'M#{!I{I ;ti_C)NG THE i_'i. I{ ,..,IS1 ti-! :_I SOUIHEASTEPLY Ci-IRB, LINE OF S. P01fl-AL ST. FL C' it x s 1�}' [' a4i!' I30! t �± ELtif ;i;ftid_ t1f,.=r 11 TwE. t, ' ?;1.::'.S; �P /�+L /� 1=: ttji' l ; t�OF�(Cr?..tk cE,lz� 4��� 1 �4r�N�CiI'!�L MAP ._C TS O ()T ltEPS t f. f'E CtiS{I f i�I t€_ J Y' } S ttj{ f'€ _ Plate I _'- ' _ ? r.S VIAf R M cF � -� � i t lrl I_; fi•It- ( ASr t ti ;{ifESV f 'x ; €i€ls I.jF'vI-'l !� 3i{i'. fl: :.t?t_h \./t E: q (r (_ 1� l�J ' R CAik t!i` YN (.-!f' E `.�f F�t}I�14 ST. iii: 4( �_.. B��g W.o, DATE $GAME 11' t r �\VF!-,€ tli•! s -',RCE t_ tiA t1f 1 3 F342i'., AS,:�✓.`3SUIR'c r r,CIA, P14}t.ai?t..f, ? i.':-[)i. -°'t i k - I 1 1_1_ t t 1 > q ?- ,-