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Home My WebLink AboutCT 12-03; 201 Walnut Townhomes; Geotechnical Report; 2015-05-18HETHERIIVIGTOlU ENGIiyEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY 201 Walnut LLC 17828 Villa Moura Drive Poway, California 92064 May 18,2015 ProjectNo. 7598.1 Log No. 17700 Attention: Subject: Mr. Greg LaMarca GRADING PLAN REVIEW Proposed Townhomes 201 Walnut Avenue Carlsbad, Califomia Reference; 1. "Geotechnical Update, Proposed Townhomes, 201 Walnut Avenue, Carlsbad, California," by Hetherington Engineering, Inc., dated November 30,2012. 2. "Grading Plans for: 201 Walnut Townhomes," by Pasco Laret Suiter & Associates, dated April 4,2015. Dear Mr. LaMarca: In response to tlie request of Mr. Brian Ardolino, Pasco Laret Suiter & Associates, we have reviewed the "Geotechnical Update..." (Reference 1) and the "Grading Plans..." (Reference 2) for the proposed townhome development. Based on our review, it appears that the grading plans has been developed in general accordance with the recommendations presented in the geotechnical update. If you have any questions please do not hesitate to contact this office. HETHB Civil Engineer 3048J Geotechnical Engineer 397 (expire 3/31/16) RECEIVED JUL 0 6 201,5 LAND DEVELOPIVIENT ENGINEERING Distiibution: 1-Addressee 1-via e-mail GREG LA MARCA [gi-eglamarca@sbcglobal.net] 1-via e-mail BRIAN ARDOLINO [bardolino@plsaengineering.com] 5365 Avenida Encinas, Suite A • Carlsbad. CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651-2306 • (949) 715-5440 • Fax (949) 715-5442 www/.hethieringtonengineering.com HETHERINGTOIM ENGINEERIIUG, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY 201 Walnut LLC 17828 Villa Moura Drive Poway, California 92064 March 9,2015 ProjectNo. 7598.1 Log No. 173 50 Attention: Mr. Greg LaMarca Subject: RECOMMENDED MATERIAL FOR RETAINING WALL BACKFILL Proposed Townhomes 201 Walnut Avenue Carlsbad, Califomia Reference: "Geotechnical Update, Proposed Townhomes, 201 Wahiut Avenue, Califomia, California," by Hetherington Engineering, Inc., dated November 30,2012. Dear Mr. LaMarca: In response to the request of Mr. Brian Ardolino, Pasco Laret Suiter & Associates, we are providing this letter addressing retaining wall backfill at the subject site. Retaining wall backflll should consist of the on-site silty sand terrace deposits with a veiy low expansion potential or import consisting of gianular soils with a very low expansion potential. Any import should be approved by the Geotechnical Consultant prior to import to the site. With respect to the retaining wall abutting the property line which will not require backfill due to the slot cut construction method, the materials which will be exposed in the backcut will consist ofthe on-site silty sand teixace deposits with a very low expansion potential consistent with the design parameters provided for retaining walls. The retaining wall backcut should be observed by the Geotechnical Consultant during constiuction to confirm that the exposed materials are as anticipated. Ifyou have any questions please do not hesitate to contact our office. H&theMgli Civil Engineer 30488 Geotechnical Engineer 397 (expire 3/31/16) Distribution: 1-Addressee 1-via e-mail GREG LA MARCA [greglamarca@sbcglobal.net] 1-via e-mail BRLAN ARDOLINO [bardolina@plsengineering.com] 5365 Avenida Encinas, Suite A • Carlsbad. CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Ttilrd Street • Laguna Beach. CA 92651-2306 • (949) 715-5440 • Fax (949) 715-5442 Virww.hetheringtonengineering.com HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY October 10,2014 ProjectNo. 7391.1 Log No. 17093 Walnut Beach Townhomes, LLC 3555 5* Avenue, Suite 100 San Diego, Califomia 92101 Attention: Mr. Matthew Gordon Subject: RETAINING WALL TEMPORARY EXCAVATIONS Proposed Townhomes 201 Walnut Avenue Carlsbad, Califomia References: Attached Dear Mr. Gordon: In response to the request of Mr. Brian Ardolino, Pasco Laret Suiter & Associates, we are providing the following recommendations regarding retaining wall temporary backcut excavations. A retaining wall abutting adjacent property is proposed along the southerly and a portion of the westerly property boundaries. The retained height is up to 7.3-feet. Temporary excavations to facilitate retaining wall constmction are anticipated to vary from 2 to 9.3- feet with a vertical backcut due to property boundary constraints. Temporary excavations greater than 5-feet high, may either be shored or excavated in slot cuts using the A-B-C method. Slot cuts should be excavated in sections no longer than 10-feet and the retaining wall should be constmcted and backfilled prior to the next section being excavated. During initial site grading, a temporary 1:1 (horizontal to vertical) slope should be excavated adjacent to the property line pending slot cut excavation for retaining wall constmction. Geotechnical conditions associated with retaining wall backcuts will be assessed during grading and constmction, with updated recommendations presented as necessary. Earthwork and temporary backcuts performed during the rainy season require precautions to "winterize" the site as appropriate and protect the site from adverse impacts that may be caused by water. Vertical slot cut backcuts should not be open for more than the time needed to constmct the retaining walls. 5365 Avenida Encinas, Suite A • Carlsbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651 • (949) 715-5440 • Fax (949) 715-5442 www.hetheringtonengineering.com RETAINING WALL TEMPORARY EXCAVATIONS ProjectNo. 7391.1 Log No. 17093 October 10, 2014 Page 2 Permission to encroach onto adjacent properties with temporary excavations and replacement of removed improvements may also be considered. This opportunity to be of services is sincerely appreciated. If you have any questions, please call this office. Sinccrclyj HETHERINGTON ENGINEERING, INC. Civil Engineer 30488 Geotechnical Engineer 397 (expire 3/31/16^==^s^ i>aul A. Bo^eth Professional Geologist 3772 Certified Engineering Geologist 1153 Certified Hydrogeologist 591 (expire 3/31/16)^^^^^EEfl^ Distribution: 1-via e-mail (gordon.matthewO@gmail.com) 1-via e-mail Cchris@,h2asandiego.com) 1 -via e-mail (bardolino@plsaengineering.com) HETHERINGTON ENGINEERING, INC. REFERENCES 1) "Geotechnical Investigation, Proposed Condominium Development, 3335-45 Lincoln Street, Carisbad, Califomia," by Hetherington Engineering, Inc., dated July 26, 2007. 2) "Geotechnical Update, Proposed Townhomes, 201 Walnut Avenue, Carisbad, Califomia," by Hetherington Engineering, Inc., dated November 30, 2012. 3) Civil Improvement Plans and Grading Plans, "201 Walnut Condomuiiums," by Pasco Laret Suiter and Associates, Inc., dated May 6, 2014 (Sheets 1 through 8). 4) "Geotechnical Response to Plan Check Comments, Proposed Townhomes, 201 Walnut Avenue, Carisbad, Califomia," by Hetherington Engineering, Inc., dated August 20, 2014. ProjectNo. 7391.1 Log No. 17093 HETHERINGTON ENGINEERING, INC. HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY August 20, 2014 ProjectNo. 7391.1 Log No. 17005 Walnut Beach Townhomes, LLC 3555 5*^ Avenue, Suite 100 San Diego, Califomia 92101 Attention: Mr. Matthew Gordon Subject: GEOTECHNICAL RESPONSE TO PLAN CHECK COMMENTS Proposed Townhomes 201 Walnut Avenue Carlsbad, CaUfomia References: Attached Dear Mr. Gordon: In response to your request, we are providing the following responses to the red line plan check comments included on Reference 4. 1) The soils which will support the proposed retaining walls adjacent to bioretention basins consist of medium dense to dense silty sand terrace deposits or compacted fill comprised of the terrace deposits with a very low expansion potential. The geotechnical parameters provided for retaining wall design are based on shear strength testing of saturated on-site soils modeling the condition of wetted soils in the vicinity ofthe bioretention basins. The introduction of water in the bioretention areas with adjacent retaining walls should not adversely impact the performance of the retaining walls. 2) The soils which will support the proposed building foundations consist of medium dense to dense silty sand terrace deposits or compacted fill comprised of the terrace deposits with a very low expansion potential. The geotechnical parameters provided for building foundation design are based on shear strength testing of saturated on-site soils modeling the condition of wetted soils in the vicinity of the permeable interlocking concrete pavement. The introduction of water in the permeable interlocking concrete pavement areas with adjacent building foundations should not adversely impact the performance ofthe building foundations. 5365 Avenida Encinas, Suite A • Carisbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651 • (949) 715-5440 • Fax (949) 715-5442 www.hetheringtonengineering.com GEOTECHNICAL RESPONSE TO PLAN CHECK COMMENTS ProjectNo. 7391.1 Log No. 17005 August 20, 2014 Page 2 This opportunity to be of services is sincerely appreciated. If you have any questions, please call this office. Sincerely, HETHERINGTON ENGINEERING, INC. Civil Engineer 304^ Geotechnical Engineer 397 »aul A. Bogseth Professional Geologist 3772 Certified Engineering Geologist 1153 Certified Hydrogeologist SE^s^^asssw.^ (expire 3/31/16) E.G.1153 B<p._ Distribution: 1-via e-mail (gordon.matthewO@gmail.com) 1-via e-mail (chris@h2asandiego.com) 1-via e-mail (bardonno@plsaengineering.com) HETHERINGTON ENGINEERING, INC. REFERENCES 1) "Geotechnical Investigation, Proposed Condominium DevelopmenL 3335-45 Lincoln Street, Carisbad, Califomia," by Hetherington Engineering, Inc., dated July 26, 2007. 2) "Geotechnical Update, Proposed Townhomes, 201 Walnut Avenue, Carisbad, Califomia," by Hetherington Engineering, Inc., dated November 30, 2012. 3) "Infiltration Rates and Depth to Groundwater, Proposed Townhomes, 201 Walnut Avenue, Carlsbad, Califomia," by Hetherington Engineering, Inc., dated November 30, 2012. 4) "Bioretention Areas, Proposed Townhomes, 201 Walnut Avenue, Carlsbad, Califomia," by Hetherington Engineering, Inc., dated January 30, 2013 (with red line plan check comments). 5) Civil Improvement Plans and Grading Plans, "201 Walnut Condominiums," by Pasco Laret Suiter and Associates, Inc., dated May 6, 2014 (Sheets 1 through 8). Project No. 7391.1 Log No. 17005 HETHERINGTON ENGINEERING, INC. HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY Walnut Beach Townhomes, LLC P.O. Box 12508 San Diego, Califomia 921112 January 30, 2013 ProjectNo. 7089.1 Log No. 16038 Attention: Mr. A. J. Tangsoc Subject: BIORETENTION AREAS Proposed Townhomes 201 Walnut Avenue Carlsbad, Califomia References: 1. "Geotechnical. Update, Proposed Townhomes, 201 Walnut Avenue, Carlsbad, Califomia," by Hetherington Engineering, Inc., dated November 30, 2012. 2. "Tentative Map For: 201 Walnut Townhomes, 201 Walnut Ave., Carlsbad, CA 92009," by Pasco Laret Suiter & Associates, dated Decembers, 2012. Dear Mr. Tangsoc: In response to the request of Mr. Brian Ardolino (Pasco Laret Suiter & Associates), we have reviewed the referenced "Geotechnical Update..." and "Tentative Map..." with respect to the proposed bioretention areas. Based on our review, we note that the soils which will support the proposed improvements consist of medium dense to dense terrace deposits with a very low expansion potential, consequently, the introduction of water in the bioretention areas should not result in detrimental ground movement and the bioretention areas are considered acceptable from a geotechnical standpoint. This opportunity to be of service is sincerely appreciated. Ifyou have any questions, please call this office. Sincerely HETHE: ;ERING, INC, Registered Civil Enginee/30488 Geotechnical Engineer 397 (expires 3/31/14) Distribution: 2-Addressee 1-via email atangsoc@gmail.com 1-via e-mail bai-dolino@plsaengineering.com 5365 Avenida Encinas, Suite A • Carlsbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651-2306 • (949) 715-5440 • Fax (949) 715-5442 www.hetheringtonengineering.com HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY November 30, 2012 Project No. 7089.1 Log No. 15896 Walnut Beach Townhomes, LLC P.O. Box 12508 San Diego, California 92112 Attention: Mr. A. J. Tangsoc Subject: GEOTECHNICAL UPDATE Proposed Townhomes 201 Walnut Avenue Carlsbad, Califomia References: Attached Dear Mr. Tangsoc: In accordance with your requesL we have performed a geotechnical update for the proposed townhome development at the subject site. Our work was performed in November 2012. The purpose of our work was to update the previous geotechnical work performed by Hetherington Engineering, Inc. (References 2 and 3). We have been provided with a "Tentative Map..." and "Site Plan..." (References 4 and 6) depicting the proposed development. This update includes seismic design criteria in accordance with the 2010 California Building Code, and updated conclusions and recommendations for the proposed construction. Our scope of work for this update included the following: . Research and review of available plans and geologic literature pertinent to the site (see References). • Site reconnaissance. • Engineering and geologic analysis. • Preparation of this report providing our findings, and our conclusions and recommendations. PROPOSED DEVELOPMENT Proposed development for the site consists of fourteen, three-story townhomes in two structures with attached garages. The previously proposed subterranean parking garage 5365 Avenida Encinas, Suite A • CaHsbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651 • Telephone (949) 715-5440 • Fax (949) 715-5442 www.hetheringtonengineering.com GEOTECHNICAL UPDATE Project No. 7089.1 Log No. 15896 November 30, 2012 Page 2 has been eliminated. Patios, motorcourt and landscaped areas are also proposed. We anticipate that the structures will be of relatively light wood-frame construction founded on conventional continuous/spread footings with slab-on-grade floors. Based on the "Tentative Map..." (Reference 6), we understand that proposed grading consists of 2,100-cubic-yards of design cut and 100-cubic-yards of design fill. Export of 2,000- cubic-yards will be required. The maximum depth of design cut is approximately 5-feet and design fill is approximately 1 to 2-feet. No slopes are proposed. Retaining walls to a maximum height of 5±-feet are proposed to accommodate grade changes. SEISMICITY The following table lists the known active faults that would have the most significant impact on the site: Fault Maximuin Probable Earthquake (Moment Magnitude) Slip Rate (mm/year) Fault Type Rose Canyon (6-kilometers/4-miles southwest) 7.0 1.5 B Elsinore (Julian Segment) (23-kilometers/14-miles northeast) 7.3 3 A SEISMIC EFFECTS 1. Ground Accelerations The most significant probable earthquake to effect the property would be a 7.0 magnitude earthquake on the Rose Canyon fault. Based on Section 1803.5.12 ofthe 2010 California Building Code, peak ground accelerations of 0.36g are possible for the design earthquake. 2. Landsliding The subject property is relatively level. The risk of seismically induced landsliding effecting the site following construction is considered nil. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE ProjectNo. 7089.1 Log No. 15896 November 30, 2012 Page 3 3. Ground Cracks The risk of surface fault rupture due to active faulting is considered low due to the absence of a known active fault on site. Ground cracks due to shaking from seismic events in the region are possible, as with all of southern Califomia. 4. Liquefaction The risk of seismically induced liquefaction within the site is considered very low due to the dense underlying terrace deposits and lack of shallow groundwater. 5. Tsunamis Review ofthe "Tsunami Inundation Map..." (Reference 1) indicates that the site is not located within an area considered susceptible to flooding by seismically generated wave acfion. The risk for seismically generated ocean waves to effect the site is considered low due to the relafively high elevation of the proposed building area above sea level. CONCLUSIONS AND RECOMMENDATIONS 1. General The proposed townhome development is considered feasible from a geotechnical standpoint. Grading and foundation plans should consider the appropriate geotechnical features of the site. The proposed construction is not anficipated to adversely impact the adjacent properties from a geotechnical standpoint, provided the recommendations presented in this report and good construction practices are implemented during design and construction. 2. Seismic Parameters for Structural Design Seismic considerations that may be used for structural design at the site include the following: a. Ground Motion - The proposed structures should be designed and constructed to resist the effects of seismic ground mofions as provided in Secfion 1613 ofthe 2010 Califomia Building Code. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE Project No. 7089.1 Log No. 15896 November 30, 2012 Page 4 Site Address: 201 Walnut Avenue, Carlsbad, California Latitude: 33.1545° Longitude: -117.3487° b. Spectral Response Accelerations - Using the location of the property and data obtained from the U.S.G.S. Java Ground Motion Calculator Program, short period Spectral Response Accelerations Ss (0.2 second period) and Si (1.0 second period) are: Ss= 1.336 Sl = 0.501 c. Site Class - In accordance with Table 1613.5.2, and the underlying geologic condifions, a Site Class D is considered appropriate for the subject property. d. Site Coefficients F. and Fy - In accordance with Table 1613.5.3 and considering the values of Ss and Si, Site Coefficients for a Class D site are: Fa= 1.0 Fv= 1.5 e. Spectral Response Acceleration Parameters Sm.; and Smi - In accordance with Section 1613.5.3 and considering the values of Ss and Si, and Fa and Fv, Spectral Response Acceleration Parameters for Maximum Considered Earthquake are: Sms = (Fa)(Ss)= 1.336 Sm, = (Fv)(Si) = 0.752 f. Design Spectral Response Accelerafion Parameters Sds and Sdi - In accordance with Section 1613.5.4 and considering the values of Sms and Smi, Design Spectral Response Acceleration Parameters for Maximum Considered Earthquake are: Sds 2/3 Sms = 0.890 Sdl =2/3 Smi = 0.501 g. Long Period Transition Period - A Long Period Transition Period of TL = 8 seconds is provided for use in San Diego County. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE Project No. 7089.1 Log No. 15896 November 30, 2012 Page 5 h. Seismic Design Categorv - In accordance with Tables 1613.5.6(1) and 1613.5.6(2), and ASCE 7-05, an Occupancy Category II and a Seismic Design Category D are considered appropriate for the subject property. 3. Slope Stabilitv The site is relatively level and no permanent cut and/or fill slopes are proposed. 4. Site Grading Prior to grading, the site should be cleared of existing improvements vegetation and debris; all of which should be disposed of at an approved location off-site. Grading will consist primarily of cut. In areas where improvements are planned at exisfing site grades, and where not removed by design cuL any existing fill and terrace deposits disturbed by demolition of existing improvements should be removed and replaced as compacted fill. The recommended remedial grading should extend to a distance equal to the removal depth outside the limits of proposed site improvements where practical. Any existing underground improvements to be removed should be completely removed and replaced with properly compacted fill. Actual removal depths should be determined in the field by the Geotechnical Consultant based on conditions exposed during grading. Following overexcavation of unsuitable materials, all areas of the site to receive fill should be scarified to a depth of 6 to 8-inches, brought to near optimum moisture conditions and compacted to at least 90-percent relative compaction. Fill should be compacted by mechanical means in uniform horizontal lifts of 6 to 8- inches in thickness. All fill should be compacted to a minimum relative compaction of 90 percent based upon ASTM: D 1557 at about optimum moisture content. Rock fragments over 6-inches in dimension and other perishable or unsuitable materials should be excluded from the fill. All grading and compaction should be observed and tested as necessary by the Geotechnical Consultant. 5. Foundation and Slab Recommendations The proposed structures may be supported on convenfional continuous/spread footings founded at least 24-inches below lowest adjacent grade and bearing entirely into approved terrace deposits and/or compacted fill. Continuous footings should be at least 18-inches wide and reinforced with a minimum of four #4 bars, two top and HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE Project No. 7089.1 Log No. 15896 November 30, 2012 Page 6 two bottom. Foundations located adjacent to utility trenches should extend to below a 1:1 plane projected upward from the bottom of the trench. Foundations bearing as recommended may be designed for a dead plus live load bearing value of 3000-pounds-per-square-foot. This value may be increased by one- third for loads including wind and seismic forces. A lateral bearing value of 250- pounds-per-square-foot per foot of depth and a coefficient of friction between foundation soil and concrete of 0.35 may be assumed. These values assume that footings will be poured neat against the foundation soils. Footing excavafions should be observed by the Geotechnical Consultant prior to the placement of reinforcing steel in order to verify that they are founded in suitable bearing materials. Total and differential settlement due to foundation loads is considered to be less than 3/4 and 3/8-inches, respectively, for foundations founded as recommended. Slab-on-grade floors supported by approved bearing material should have a minimum thickness of 5-inches and should be reinforced with #4 bars spaced at 18-inches, center-to-center, in two directions, and supported on chairs so that the reinforcement is at mid-height in the slab. Floor slabs should be underiain with a moisture vapor retarder consisfing of a minimum 10-mil polyvinyl chloride membrane. At least 2- inches of sand should be placed over the vapor retarder to assist in concrete curing and at least 2-inches of sand should be placed below the vapor retarder. The vapor retarder should be placed in accordance with ASTM: E 1643. Prior to placing concrete, the slab subgrade soils should be thoroughly moistened. Vapor retarders are not intended to provide a waterproofing function. Should moisture vapor sensifive floor coverings be planned, a qualified consultant/contractor should be consulted to evaluate moisture vapor transmission rates and to provide recommendations to mitigate potential adverse impacts of moisture vapor transmissions on the proposed flooring. 6. Retaining Walls Retaining wall foundations should be designed in accordance with the previous building foundation recommendations. Retaining walls free to rotate (cantilevered walls) should be designed for an active pressure of 35-pounds-per-cubic-foot (equivalent fluid pressure) assuming level backfill consisting of onsite granular soils. Walls restrained from movement at the top should be designed for an at-rest earth pressure of 60-pounds-per-cubic-foot (equivalent fluid pressure). Any additional surcharge pressures behind the retaining walls should be added to these values. Retaining walls should be provided with adequate drainage to prevent buildup of HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE Project No. 7089.1 Log No. 15896 November 30, 2012 Page 7 hydrostatic pressure and should be adequately waterproofed. The subdrain system behind retaining walls should consist at a minimum of 4-inch diameter Schedule 40 (or equivalent) perforated (perforations "down") PVC pipe embedded in at least 1- cubic-foot of 3/4-inch crushed rock per lineal foot of pipe all wrapped in approved filter fabric. Other backdrain systems that may be contemplated for use behind retaining walls due to the ulfimate design and construction methodology will be considered on a case- by-case basis. Recommendations for wall waterproofing should be provided by the Project Architect and/or Structural Engineer. The lateral pressure on retaining walls due to earthquake motions (dynamic lateral force) should be calculated as PA = 3/8 y H^kh where PA = dynamic lateral force (lbs) Y = unit weight = 115 pcf H = height of wall (feet) kh = effective horizontal ground acceleration = 1/2 peak ground accelerafion = 0.18g If considered necessary by the Structural Engineer, the dynamic lateral force is in addition to the static force and should be applied at 0.6H above the base ofthe wall. 7. Temporarv Slopes Temporary slopes necessary to facilitate site grading or the construction of retaining walls may be cut vertically up to 4-feet where the cuts are not influenced by existing structures/improvements or property line constraints. Any portion of temporary slopes near existing structures/improvements, higher than 4-feet, or exposing potentially unstable soils should be sloped at a ratio no steeper than 1:1 (horizontal to vertical), slot cut, or shored. 8. Concrete Flatwork Concrete flatwork should be at least 5-inches thick (actual) and reinforced with at least No. 4 bars placed at 18-inches on center (two directions) and placed on chairs so that the reinforcement is in the center of the concrete. Contraction joints should be provided at 8-feet spacings (maximum). Joints should create square panels where possible. For rectangular panels (where necessary) the long dimension should be no more than 1.5 fimes the short dimension. Joint depth should be at least 0.25 times the HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE ProjectNo. 7089.1 Log No. 15896 November 30, 2012 Page 8 flatwork thickness. Expansion joints should be thoroughly sealed to prevent the infiltrafion of water into the underlying soils. 9. Retaining Wall and Utilitv Trench Backfill All retaining wall and utility trench backfill should be compacted to at least 90- percent relative compaction (ASTM: D 1557). Backfill should be observed and tested by the Geotechnical Consultant. 10. Corrosivitv Representative samples of the on-site soils were submitted for sulfate testing. The sulfate content is consistent with a severe sulfate exposure classification per American Concrete Institute Publicafion 318, Secfion 4.3. Consequenfiy, special provisions for sulfate resistant concrete in accordance with Table 4.2.1 of the American Concrete Institute Publication 318 are considered necessary. Other corrosivity testing has not been performed, consequently, the on-site soils should be assumed to be severely corrosive to buried metals unless testing is performed to indicate otherwise. 11. Site Drainage Site drainage and choice of landscaping are important. The following recommendations are intended to minimize the potential adverse effects of water on the structures and appurtenances. Surface drainage issues should be addressed by the project Architect and/or Civil Engineer. a. Consideration should be given to providing the structures with roof gutters and downspouts that discharge water to an area drain system, or other designed outlet system that discharges water away from the structures/improvements, and to the street or storm drain system. b. All site drainage should be directed away from the structures, and to designed outlet structures. This may be accomplished through area drains or through sheet drainage. Drainage should not be allowed to pond behind retaining walls or adjacent to the structures. c. No landscaping should be allowed against the structures. Moisture accumulation or watering adjacent to foundations can result in deteriorafion of wood/stucco and may adversely effect footings and the performance of the structure. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE ProjectNo. 7089.1 Log No. 15896 November 30, 2012 Page 9 d. Irrigated areas should not be over-watered. Irrigation should be limited to that required for maintaining the vegetation. Additionally, automafic systems should be seasonally adjusted. e. All yard and roof drains should be periodically checked to verify they are not blocked and flow properly. 12. Recommended Observation and Testing During Construcfion The following tests and/or observations by the Geotechnical Consultant are recommended: a) Site grading. b) Footing excavations prior to placement of forms and reinforcing steel. c) Retaining wall backdrains and backflll. d) Utility trench backfill. e) Hardscape subgrade. 13. Grading and Foundafion Plans Review Grading and foundation plans should be reviewed by the Geotechnical Consultant to confirm conformance with the recommendations presented herein and to provide additional recommendations, as necessary. LIMITATIONS The analyses, conclusions and recommendations contained in this report are based on site condifions, as they existed at the time of our prior investigafion and further assume the excavations to be representative of the subsurface conditions throughout the site. If different subsurface conditions from those encountered during our exploration are observed or appear to be present in excavations, the Geotechnical Consultant should be promptly notified for review and reconsideration of recommendations. Our update was performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable Geotechnical Consultants pracficing in this or similar HETHERINGTON ENGINEERING, INC. GEOTECHNICAL UPDATE ProjectNo. 7089.1 Log No. 15896 November 30, 2012 Page 10 localities. No other warranty, express or implied, is made as to the conclusions and professional advice included in this report. This opportunity to be of service is sincerely appreciated. If you have any questions, please call this office. Sincerely, Hetherington Engineering, Inc. 'aui A. Bogseth Professional Geologist 3772 Certified Engineering Geol Certified Hydrogeologist (expires 3/31/14) Distribution: 5-Addressee Civil Engineer 3048S Geotechnical Engineer 397 (expires 3/31/14) ^,s*sa==^ate^ ^^^^ HETHERINGTON ENGINEERING, INC. REFERENCES 1) California Emergency Management Agency, et al., "Tsunami Inundation Map for Emergency Planning, Oceanside Quadrangle and San Luis Rey Quadrangle," dated June 1,2009. 2) Hetherington Engineering, Inc., "Geotechnical Investigation, Proposed Condominium Development, 3335-45 Lincoln StreeL Carisbad, California," dated July 26, 2007 (ProjectNo. 5956.1) 3) Hetherington Engineering, Inc., "Results of Soil Sulfate Testing, Proposed Condominium Development, 3335-45 Lincoln Street, Carisbad, California, APN204-131-01 through 04," dated August 2, 2007. 4) Hawkins + Hawkins Architects, "Site Plan, 201 Walnut Townhomes, 201 Walnut Avenue, Carlsbad, CA," dated August 14, 2012 (Sheet AO.l). 5) ICBO, "California Building Code," 2010 Edifion. 6) Pasco Laret Suiter & Associates, "Tentative Map for 201 Walnut Townhomes, 201 Walnut Avenue, Carisbad, CA," dated August 1, 2012 (Sheet 1 of 3). 7) Peterson, Mark P., et al, "Documentation for the 2008 Update of the United States Nafional Seismic Hazards Maps," USGS Open File Report 2008-1128, dated 2008. 8) United States Geologic Survey, "Java Ground Motion Calculator," Version 5.1.0. 9) 2007 Working Group and California Earthquake Probability, "The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF-2)," USGS Open File Report 2007-1437 and CGS Special Report 203, dated 2008. Project No 7089.1 Log No. 15896 HETHERINGTON ENGINEERING, INC. HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY November 29, 2012 ProjectNo. 7089.1 Log No. 15992 Walnut Beach Townhomes, LLC P.O. Box 12508 San Diego, CaUfomia 92112 Attention: Mr. A. J. Tangsoc Subject: INFILTRATION RATES AND DEPTH TO GROUNDWATER Proposed Townhomes 201 Walnut Avenue Carlsbad, Califomia References: 1. "San Diego County Hydrology Manual," prepared by the County of San Diego, Department of Public Works, Flood Control Section, dated June 2003. 2. "Geotechnical Investigation, Proposed Condominium Development, 3335-45 Lincoln Street, Carisbad, Califomia," by Hetherington Engineering, Inc., dated July 26, 2007. Dear Mr. Tangsoc: In response to your request, we have evaluated infiltration rates and depth to groundwater at the subject site. Based on the results of our geotechnical investigation (Reference 2), the site is underlain by terrace deposits consisting of moist, loose to dense, silty sand. No groundwater was encountered in the borings to the maximum depth explored of 19-feet. The San Diego County Hydrology Manual, Soil Hydrologic Group map indicates that the site is in soil hydrologic group B which are soils which have moderate infiltration rates when thoroughly wetted. Percolation tests were performed by this office on November 20 and 21, 2012 in accordance with the County of San Diego, Department of Environmental Health, Land and Water Quality Division, Design Manual for On-Site Waste Water Treatment Systems. The approximate locations of the percolation tests are shown on the attached Plot Plan, Figure 1 and the test results are shown on the attached Percolation Test Data Sheets, Figures 2 through 4. The average infiltration rate based on the percolation testing is 4.8 inches/hour. 5365 Avenida Encinas, Suite A • Carisbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651 • Telephone (949) 715-5440 • Fax (949) 715-5442 www.hetheringtonengineering.com INFILTRATION RATES AND DEPTH TO GROUNDWATER ProjectNo. 7089.1 Log No. 15992 November 29, 2012 Page 2 Based on our work, the underlying terrace deposits at the subject site are considered to have high infiltration rates consistent with soil hydrologic group A and the depth to groundwater is at least 19-feet. Soil hydrologic group A should be used for storm water management design. This opportunity to be of service is sincerely appreciated. If you have any questions, please call this office. Sincerely, HETHERINGTON ENGINEERING, INC. Mm; D. Hetnei Civil Engineer 30 Geotechnical Engi (expire 3/31/14) MDH/dkw Distribution: 2-Addressee Paul A. Bogseth Professional Geologist 3772 Certified Engineering Geologist 1^ Certified Hydrogeologist 591 (expires 3/31/14) 1-via e-mail (atangsoc@gmail.com) HETHERINGTON ENGINEERING, INC. PERCOLATION DATA SHEET Project: Walnut Job No. 7089.1 Test Hole No.: 1 Date Excavated: 11/20/12 Depth of Test Hole: 3.5" Soil Classification: Silty Sand Check for Sandy Soil Criteria Tested by: CDF Date: 11/21/12 Check for Sandy Soil Criteria Tested by: CDF Presoak: 11/20/12 Actual Percolation Tested by: CDF Date: 11/21/12 Sandv Soil Criteria Test Trial No. Time Time Interval Initial Water Final Water • in Water (Min) Level (inches) Level (inches) Level (Inches) i 8:44 39 12.9 6.0 6 9:14 2 9:14 19 6.0 4.0 2 9:33 Time 9:33 10:03 Use: (^rmapSandy (Circle One) Soil Criteria Time Interval (min) 30 Total Elapsed Time (min) 30 Initial Water Level (inches) 6.00 Final Water Level (inches) 3.00 • in Water Level (inches) 3.00 Percolation Rate (min/inch) 10.00 10:33 10:33 30 60 6.00 3.25 2.75 10.90 10:33 11:03 11:03 11:33 11:33 12:03 12:03 12:33 12:33 1:03 1:03 1:33 30 30 30 30 30 30 90 6.00 3.75 120 6.00 3.80 150 6.00 3.90 180 6.50 4.20 210 6.25 4.0 240 6.10 4.20 2.25 2.20 2.10 2.30 2.25 1.90 13.30 13.60 14.30 13.00 13.30 15.80 Log No. 16000 PERCOLATION DATA SHEET Project: Walnut Job No. 7089.1 Test Hole No.: 2 Date Excavated: 11/20/12 Depth of Test Hole: 2'6" Soil Classification: Silty Sand Check for Sandy Soil Criteria Tested by: CDF Date: 11/21/12 Check for Sandy Soil Criteria Tested by: CDF Presoak: 11/20/12 Actual Percolafion Tested by: CDF Date: 11/21/12 Sandv Soil Criteria Test Trial No. Time Time Interval (Min) Initial Water Level (inches) Final Water Level (inches) • in Water Level (Inches) i 8:42 30 12 6 6 9:12 2 9:13 17 6 3.8 2.2 9:30 Use: (^ormapSandy (Circle One) Soil Criteria Time 9:31 10:01 Time Interval (min) 30 Total Elapsed Time (min) 30 Initial Water Level (inches) 6.90 Final Water Level (inches) 3.70 A in Water Level (inches) 3.20 Percolation Rate (min/inch) 9.40 10:01 10:31 10:31 11:01 11:01 11:31 11:31 12:01 12:01 12:31 12:31 1:01 30 30 30 30 30 30 60 6.30 3.70 90 6.25 3.80 120 6.00 3.80 150 6.00 3.90 180 6.00 3.50 210 6.00 3.50 2.80 2.45 2.20 2.10 2.50 2.50 10.70 12.20 13.60 14.30 12.00 12.00 1:01 1:31 30 240 6.00 3.70 2.30 13.00 Log No. 16000 PERCOLATION DATA SHEET Project: Walnut Job No. 7089.1 Test Hole No.: 3 Date Excavated: 11/20/12 Depth of Test Hole: 2' 2" Soil Classification: Sandy Check for Sandy Soil Criteria Tested by: CDF Date: 11/21/12 Check for Sandy Soil Criteria Tested by: CDF Presoak: 11/20/12 Actual Percolation Tested by: CDF Date: 11/21/12 Sandv Soil Criteria Test Trial No. Time Time Interval (Min) Initial Water Level (inches) Final Water Level (inches) • in Water Level (Inches) i 8:40 30 12 3.25 8.75 9:10 2 9:10 18 6.25 2.80 3.45 9:20 Time 9:30 10:00 Use: (^ormapSandy (Circle One) Soil Criteria Time Interval (min) 30 Total Elapsed Time (min) 30 Initial Water Level (inches) 6.00 Final Water Level (inches) 1.70 • in Water Level (inches) 4.30 Percolation Rate (min/inch) 6.10 10:00 10:30 30 60 6.00 1.80 4.20 7.10 10:30 11:00 11:00 11:30 11:30 12:00 30 30 30 90 6.25 120 6.00 150 6.50 2.00 1.90 2.00 4.25 4.10 4.50 7.10 7.30 6.70 12:00 12:30 12:30 1:00 1:00 11:30 30 30 30 180 210 240 6.00 6.50 6.00 2.00 2.50 2.60 4.00 4.00 3.40 7.50 7.50 8.80 Log No. 16000 GEOTECHNICAL INVESTIGATION Proposed Condominium Development 3335-45 Lincoln Street Carlsbad, Califomia HETHERINGTON ENGINEERING, INC. HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY July 26, 2007 ProjectNo. 5956.1 Log No. 11029 Barron Investment Group, LLC 1135 Camino del Mar Del Mar, CaUfomia 92014 Attention: Mr. Jim Schmitz Subject: GEOTECHNICAL INVESTIGATION Proposed Condominium Development 3335-45 Lincoln Street Carlsbad, Califomia APN 204-131-01 through 04 References: Attached Dear Mr. Schmitz: In accordance with your requesl, Hetherington Engineering, Inc. has performed a geotechnical investigation^- th^roposed condominium development to be located at the subject site. Our^^k ^ms performed in July 2007. The purpose ofthe investigation was to evaluate gwldgic and soil conditions within the areas intended for new constmctioii ana ^5'provide grading and foundation recommendations for the proposed residential s'^Kture with a subterranean parking garage. With the above in mind, our scope of work included the following: • Research and review of available plans and geologic literature pertinent to the site vicinity (see References). • Subsurface exploration consisting of two small-diameter auger borings for soil sampling and geologic observation. • Laboratory testing of samples obtained from the subsurface exploration. • Engineering and geologic analysis. • Preparation of this report providing the resuhs of our field and laboratory work, analyses, and our conclusions and recommendations. 5365 Avenida Encinas, Suite A • Carisbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651 • (949) 715-5440 • Fax (949) 715-5442 www.hetheringtonengineering.com GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 2 SITE DESCRIPTION The subject property (3335-45 Lincoln Street) is located on the east comer of Walnut Avenue and Garfield Street within the city of Carisbad, CaUfomia (see Location Map, Figure 1). The approximately 0.85-acre site consists of a gently sloping, rectangular shaped, undeveloped parcel and an adjacent relatively level, parcel developed with a single-story, single-family-residence. The existing residence will be demolished. The property is bounded by Garfield Street to the southwest. Walnut Street to the northwest, Lincoln Street to the northeast and residential stmctures to the southeast. PROPOSED DEVELOPMENT Preliminary development plans indicate that the proposed constm(^on consist^ of a two- story residential condominium stmcture built over a subterrano.in park itig garage. Garage access will be via a ramp from Lincoln Street. Retainii:^'|^l%% to approximately 15- feet high are anticipated. We anticipate that th^3^%ise WiU be wood or steel frame, buih over the parking garage with a slab-on-grade glrage floor. Building loads are expected to be typical for this type (^elatmlp light constmction. Significant grading and soil export, in conjunction w ilh ihc inst^tion of shoring, is anticipated in order to excavate the parking garage. It is ah^Mipated that shoring will be necessary along the northwest and southeast pttperty boundaries and may be necessary in other areas. Temporary cm slopes are' anticipated for the southwest and northeast property boundaries. SUBSURFACE EXPLORATION Subsurface conditions were explored by excavating two small-diameter auger borings to depths of 19-feet below existing site grades. The approximate locations of the borings are shown on the attached Plot Plan, Figure 2. The subsurface exploration was supervised by a geologist from this office, who visually classified the soil and bedrock materials, and obtained bulk and relatively undisturbed samples for laboratory testing. The soils were visually classified according to the Unified Soil Classification System. Soil classifications are shown on the attached Boring Logs, Figures 3 and 4. LABORATORY TESTING Laboratory testing was performed on samples obtained during the subsurface exploration. Tests performed consisted of the following: HETHERINGTON ENGINEERING, INC. ADAPTED FROM: The Thomas Guide, San Dlego County, 2006 Edition, Page 1106 I N i SCALE: 1"-2000' (1 Grid = 0.5 x 0.5 miles) LOCATION MAP HETHERINGTON ENGINEERING, INC. GEOTECHNICAL CONSULTANTS 3335-45 Lincoln Street Carisbad, California PROJECT NO. 5956.1 FIGURE NO. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 3 • Dry Density and Moisture Content (ASTM: D 2216) • Sulfate Content (EPA 9038) • Direct Shear (ASTM: D 3080) • Expansion Index (ASTM: D 4829) Results of the dry density and moisture content determinations are presented on the Boring Logs, Figures 3 and 4. The remaining laboratory test results are presented on the Laboratory Test Resuhs, Figure 5. SOIL AND GEOLOGIC CONDITIONS 1. Geologic Setting The subject site lies within a relatively level marnie terrace that is contained within the coastal plain region of northe^an^fo-County, Califomia. The coastal plain region is characterized by numffiati|^fegressive marine terraces of Pleistocene age that have been established ata^veta^afe-eut platforms of underlying Eocene bedrock and were formed dur^^^So-eustatic changes in sea level. The terraces extend from areas of highaif,fe#tion east of the site and descend generally west-southwest in a "stairstef-^'.f^^pi aown to the present day coastiine. These marine terraces increase in age e^^^d The subject property is contained within the southwestem portion of the U.S.G.S San Luis Rey 7-1/2 minute quadrangle. As observed in the subsurface excavations, the site is underiain by Quatemary sedimentary marine and non-marine terrace deposits. No evidence of adverse geologic stmcture, faulting, or groundwater was observed in the borings. 2. Geologic Unit a. Terrace Deposits - Encountered in both borings were terrace deposits consisting of damp to moist, medium dense to very dense, light to dark brown to red brown, silty fine to medium sand. The terrace deposits are considered suitable for support of the proposed stmcture. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 4 3. Groundwater No seepage or groundwater was encountered in the exploratory excavations. It should be noted, however, that fluctuafions in the amount and level of groundwater may occur due to variations in rainfall, irrigation, and other factors that might not have been evident at the time of our field investigation. SEISMICITY The site is located within the seismically active southem Califomia region. There are, however, no known active or potentiaUy active fauhs presently mapped that pass through the site nor is the site located within the presentiy defined limits of aillAkuist-Priolo Earthquake Fauh Zone. Active or potenfially active fauh zones^wiiliin Uiclite region include the Rose Canyon, Coronado Bank and Elsinore (Julian l^j^pit).'" Strong ground mofion could also be expected from earthquakes occurrinjlT'Ckite fee San Jacinto and San Andreas fauh zones, which lie northeast of the site at i number of other offshore faults. ater distances, as well as a The following table lists the knovsn active faults that would have the most significant impact on the site: Fault Maximuin Probable Earthquake (Moment Magnitude) SUp Rate (mm/year) Fault Type Newport-lnglewood/Rose Canyon 7.5-kilometers SW 7.2 1.5 B Coronado Bank 38-kilometers SW 7.6 3 B Elsinore (Julian Segment) 38-kilometers NE 7.1 5 A SEISMIC EFFECTS 1. Ground Accelerations The most significant probable earthquake to affect the site would be a 7.2 magnitude earthquake on the Rose Canyon fauh zone. Depiction of probabilistic seismic hazard analysis utilizing a consensus of historical seismic data and the respective regional geologic conditions that are shown on the "The Revised 2002 Califomia Probabilistic HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 5 Seismic-Hazard Maps" and the "Probabilistic Seismic Hazards Assessment Model (April 2003)" indicate that peak ground accelerations of about 0.28 to 0.30g are possible with a 10% probabiUty of being exceeded in 50-years (References 2 and 4). 2. Ground Cracks The risk of fauh surface mpture due to active fauhing is considered low due to the absence of known active faulting on site. Ground cracks due to shaking from seismic events in the region are possible, as with all of southem Califomia. 3. Landsliding Due to the absence of slopes in the immediate vicinity. IIK- risk f f l.iii^sliding is considered negligible. 4. Liquefaction The risk of seismically induced liquef.ictioii is considered low due to the lack of shallow ground water and the densSe't^idcrlying i,jiiace deposhs. 5. Tsunamis Due to the relatively low elevation of the property and hs proximity to the coast, the potential fo« -Wlmically generated ocean waves impacting the she is considered moderate. CONCLUSIONS AND RECOMMENDATIONS 1. General The proposed development is considered feasible from a geotechnical standpoint. Grading and foundation plans should take into account the appropriate geotechnical features ofthe site. The proposed constmction is not anticipated to adversely impact the adjacent properties from a geotechnical standpoint, provided the recommendations presented in this report and good constmction practices are implemented during design and constmction. 2. Seismic Parameters for Stmctural Design Seismic considerations that should be used for stmchiral design at the she include the following: HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 6 a. Ground Motion - The proposed stmcture should be designed and constmcted to resist the effects of seismic ground motions as provided in Chapter 16, Division IV-Earthquake Design ofthe 2001 Califomia Building Code (CBC). The basis for the design is dependent on and considers seismic zoning, site characteristics, occupancy, configuration, stmctural system and building height. b. Soil Profile Tvpe - In accordance with CBC Secfion 1629.3.1, Table 16-J, and the underlying geologic condhions, a she Soil Profile of Type SD is considered appropriate for the subject property. c. Seismic Zone - In accordance with CBC Section 1629.4.1 ami Figure 16-2, the subject site is situated within Seismic Zone 4. d. Seismic Zone Factor (z) - A Seismic Zone ^ctor pf ,0,.4O is assigned based on CBC Table 16-1. Since the she is within^i^i^S'?^e"4, CBC Section 1629.4.2 requires a Seismic Source Type and Near ^iel^Factor. e. Near-Source Factors (Na aad Nv) - Based on the known active fauhs in the region and distance of the fjanilW from the site, a Seismic Source Type of B per CBC Table 16-U, and Near Source Factors of Na = 1.0 per Table 16-S and Nv = 1.1 per Table 16-T ard provided. f Seisaaac Coefficients (Ca and Cv) - Using the Soil Profile Type and Seismic Zone Factor along with CBC Tables 16-Q and 16-R, the Seismic Coefficients Ca = 0.44 (Na) and Cv = 0.64 (Nv) are provided, or Ca = 0.44 and Cv = 0.71. 3. Slope Stabilitv The site is relatively level and no permanent cut and/or fill slopes are anticipated. 4. Site Grading Prior to grading, the she should be cleared of existing improvements to be demolished, vegetation and debris; all of which should be disposed of at an approved location off-she. Grading will consist primarily of cut of approximately 15-feet for the subterranean parking garage. In areas where unprovements are planned at existing site grades, any existmg fill and terrace deposhs disturbed by demoUtion of existing improvements should be removed and replaced as compacted fill. The recommended remedial grading should extend to a distance equal to the removal HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 7 depth outside the limhs of proposed site improvements where practical. Any existing underground improvements to be removed should be completely removed and replaced with properly compacted fill. Those improvements not to be removed should have associated fill soils removed and recompacted to at least 90-percent relative compaction. Actual removal depths should be determined in the field by the Geotechnical Consultant based on condhions exposed during grading. Following overexcavation of unsuitable materials, all areas of the site to receive fill should be scarified to a depth of 8 to 12-inches, brought to near optimum moisUare condifions and compacted to at least 90-percent relative compaction. Fill should be compacted by mechanical means in uniform horiz^^^fts of 6 to 8- inches in thickness. AU fill should be compacted to a minimi^ relative (l^ompaction of 90 percent based upon ASTM: D 1557-02 at about optonfa moishire content. Rock fragments over 6-inches in dimension a4d;^ptil|i^pteishable or unsuhable materials should be excluded from the fill gradmg and compaction should be observed and tested as necessary by the (icnli.'chnic.il Consultant. 5. Foundation and Slab Recommendations The proposed stnu-luie may be supported on conventional continuous/spread footings founded at least 24-inches below lowest adjacent grade and bearing enthely into approvd^*l«ii^^ deposhs and/or compacted fill. Continuous footings should be at least 18^^es wide and reinforced with a minimum of four #4 bars, two top and two bottom. Foundations located adjacent to utility trenches should extend to below a 1:1 plane projected upward from the bottom of the trench. Foundations bearing as recommended may be designed for a dead plus live load bearing value of 3000-pounds-per-square-foot. This value may be increased by one- third for loads including wind and seismic forces. A lateral bearing value of 250- pounds-per-square-foot per foot of depth and a coefficient of friction between foundation soil and concrete of 0.35 may be assumed. These values assume that footings will be poured neat against the foundafion soils. Footing excavations should be observed by the Geotechnical Consultant prior to the placement of reinforcing steel in order to verify that they are founded in suhable bearing materials. The subterranean parking garage subgrade should be compacted to at least 95-percent relative compaction (ASTM: D 1557-02). The garage slab-on-grade floors should have a minimum thickness of 5-inches (actual) and should be reinforced with #4 bars spaced at 18-inches, center-to-center, in two directions, and supported on chairs so HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 8 that the reinforcement is at mid-height in the slab. Floor slabs should be underlain by a 4-inch layer of clean sand with at least a 10-mil visqueen vapor barrier placed in the middle of the sand layer. Consideration should be given to providing contraction joints to control shrinkage cracking. Total and differential settlement of the proposed stmcture due to foundation loads is considered to be less than 3/4 and 3/8 inches, respectively, for footings founded as recommended. 6. Shoring We anticipate that shoring will be necessary along the north^s^nd southeast property boundaries to protect Walnut Street and the adja«.-iil puiperliies during excavation of the parking garage. Shoring may consist of ten^^ry shoring or the shoring may be incorporated into the permanent jefiairijjl|i^#a^. If the shoring is incorporated into the permanent retaining waU^ tii^^^temg/retaining walls should be supported by drilled piers founded in tcrrace^^^jMs. Drilled piers associated with the proposed shoring/retaining shouiW Extend at least 5-feet into approved terrace deposits and should have a/minimum diameter of 18-inches. Drilled piers founded as recommend^ mav lie* designed for a dead-plus-live-load end bearing capacity of 3000^^pfcer-^are-foot. This value may be increased by one-third for wind ami seismic f^es. A skin friction value of 200-pounds-per-square-foot may be^fci«pa^ m terrace deposhs. Piers may resist lateral loads by a passive pressur^^^50-pounds-per-square foot per foot of depth into terrace deposhs to a maximum value of 3000-pounds-per-square-foot. The passive resistance may be calculated over two pier diameters. The point of fixity for drilled piers may be considered to be 3-feet below the subterranean parking garage finished grade. Lagging will likely be necessary between drilled piers. Shoring plans should be reviewed by the Geotechnical Consultant. The shoring system should be designed by a Civil Engineer familiar with shoring design. The design, installation and performance of the shoring system are considered the responsibility of the contractor and designer. Temporary cuts are anticipated for the southwest and northeast property boundaries. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL E^VESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 9 7. Retaining Walls Retaining wall foundafions should be designed in accordance with the previous building/shoring foundation recommendations. Retaining walls free to rotate (cantilevered walls) should be designed for an active pressure of 35-pounds-per- cubic-foot (equivalent fluid pressure) assuming level backflll consisting of the granular on-she soils. Walls restrained from movement at the top should be designed for an additional uniform soils pressure of 8xH pounds-per-square-foot where H is the height ofthe wall in feet. Any addhional surcharge pressures behind the wall should be added to these values. Retaining walls should be provided with adequate drainage to prevent buildup of hydrostatic pressure and should be adequately waterproofed. The subdrain system behind retaining walls should consist at a minium of 4-inch diameter Schedule 40 (or equivalent) perforated (perforafions '"down") ^PVC pipe embedded in at least one-cubic-foot of 3/4 inch cmshed rocl|^ Hneal foot of pipe, all wrapped in approved filter fabric. Other subdiaiii '.ystems that may be contemplated for use behind the retaining walj» dvp^to the ultimate wall design and constmction methodology will be ;,a^^l^^ed^ on a case-by-case basis. Recommendations for wall waterproofing should be provided by the Project Archhect and/or Stmctural Engineer. 8. Temporarv Slopes Temporiaty slopes exposing terrace deposhs should be inclined at a slope ratio no steeper tfeh 1:1 (horizontal to vertical) or shoring will be required. No unshored vertical cuts should be made in the on-site sandy materials. Field observations by the Engineering Geologist during excavation of these slopes are recommended and considered necessary to confirm anticipated conditions and provide revised recommendations if warranted. 9. Soluble Sulfate Representative samples of the on-site soils were submitted for sulfate analyses and the resuhs are pending. We will provide a letter including the test resuhs and any attendant recommendations when the testing is complete. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 10 10. Concrete Flatwork Concrete flatwork should be at least 4-inches thick (actual) and reinforced with #3 bars spaced at 18-inches on center (two directions) and placed on chairs so that the reinforcement is in the center of the slab. Slab subgrade should be thoroughly moistened prior to placement of concrete. Contraction joints should be provided at 10-feet spacing (maximum). 11. Trench and Retaining Wall Backfill All utility trench and retaining wall backfill should be compacted to at least 90 percent relative compaction (ASTM: Dl557-02) and tcsk-d b> ihc Geotechnical Consultant. 12. She Drainage The following recommendations are nilcndcd l«i Ininimize the potential adverse effects of water on the stmcttires-and appanenances. Surface drainage should be designed by the project Archi icci .indoor Civil Engineer. a. Consideration ^u^^ be given to providing the stmctures with roof gutters and downspoirt^ t& discharge to an area drain system and/or to suhable locations away,,froA t&e sfructure. b. All site drainage should be directed away from the stmctures. The on-she soils are generally sandy in nature and considered erodible if exposed to concentrated drainage. c. No landscaping should be allowed agamst the stmcture. Moisture accumulation or watering adjacent to foundations can resuh in deterioration of wood/stucco and may affect foundation performance. d. Irrigated areas should not be over-watered. Irrigation should be limhed to that required to maintain the vegetation. Addhionally, automatic systems must be seasonally adjusted to minimize over-saturation potential particularly in the winter (rainy) season. e. All yard and roof drains should be periodically checked to verify they are clear and flow properly. This may be accomplished either visually or, in the case of subsurface drains, by placing a hose at the inlet and checking the outlet for flow. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 11 13. Recommended Observation and Testing During Constmction The following tests and/or observations by the Geotechnical Consultant are recommended: a. Observation and testing of grading. b. Observation of shoring installation and of all temporary excavations. c. Observation of footing and drilled pier excavations prior to placement of forms and reinforcing steel. d. Observation of Interior and exterior utility trench b.ickli II e. Observation and testing of concrete U.irA«•! k and pa vfiiicnt subgrade. f Observation and testing of ret^gg wall backfill and drain placement. 14. Grading, Foundation and^horing Plan Review Grading, founiliilion and shoring plans should be reviewed by the Geotechnical Consultant t^gpfmn conformance with the recommendations presented herein or to modify Ute tfecbmmendations as necessary. LIMITATIONS The analyses, conclusions and recommendations contained in this report are based on site condhions, as they existed at the time of our investigation and further assume the excavations to be representative of the subsurface condhions throughout the site. If different subsurface condhions from those encountered during our exploration are observed or appear to be present in excavations, the Geotechnical Consuhant should be prompfiy notified for review and reconsiderafion of the recommendations. Our investigation was performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable Geotechnical Consuhants practicing in this or similar locaUties. No other warranty, express or implied, is made as to the conclusions and professional advice included in this report. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION ProjectNo. 5956.1 Log No. 11029 July 26, 2007 Page 12 This opportunity to be of service is sincerely appreciated. If you have any questions, please call this office. Sincerely, Hetherington Engineering, Inc. Michel A. Vasconcellos Professional Geologist 7934 Certified Engineering Geologist 2411 (expires 1/31/09) Mark D. Hethermgton Registered Civil Engineer 30488 Geotechnical Engineet 397 (expires 3/31/Q^) MV/MDH/dkw Distribution: 4-Addressee Attachments: Locatiott^^tp Pli>t Flan Hot uii togs Laboratory Test Results Figure I Figure 2 Figures 3 and 4 Figure 5 HETHERINGTON ENGINEERING, INC. REFERENCES 1. BHA, Inc. Plot Plan, undated. 2. Califomia Geological Survey "Probabilistic Seismic Hazards Assessment Model," 2002 (Revised April 2003). 3. Califomia Division of Mines and Geology, "Planning Scenario for a Major Earthquake, San Diego - Tijuana MetropoUtan Area," Special Publication 100, dated 1990. 4. Cao, Tianging, et al "The Revised 2002 Califomia Probabilistic Seismic Hazard Maps," dated June 2003. 5. ICBO, "Califomia Building Code," 2001 Edition. 6. ICBO, "Maps of Known Active Fauhs Near-Source Zones in Califomia and Adjacent Portions of Nevada," dated Febmary 1998. 7. Jennings, Charles W., "Fault Activity Map of Califomia and Adjacent Areas," CaUfomia Data Map Series, Map No. 6, dated 1994. 8. Kennedy, Michael P., "Geology of the San Diego MetropoM|*u Area, Califomia," CaUfomia Division of Mines and Geology, Bulletijti 20i;date^l975. 9. Kennedy, Michael P., "Geologic Maps of the \\<rthwestem Part of San Diego County, Califomia" Califomia Division of \liife"and Geology, Open File Report 96- 02, dated 1996. 10. Kennedy, Michael P., et al., "Ch;iracter and Recency of Faulting, San Diego MetropoUtan Area, CaMfiB|nia,""Special Report 123, dated 1975 11. Peterson, M^'^^'^y, W., Bryant, W., et al., "Seismic Shaking Hazard Maps of CaUfon^?^&#omia Division of Mines and Geology, Map Sheet 48, dated 1999. 12. Tan, Sia^S., "Landslide Hazards in the Northem Part of the San Diego Metropolitan Area, San Diego County, Califomia, Landslide Hazard Identification Map No. 35", dated 1995. 13. Weber, F. Harold, "Recent Slope Failures, Ancient Landslides and Related Geology ofthe North-Central Coastal Area, San Diego County, Califomia" CaUfomia Division of Mines and Geology, Open File Report 82-12, dated 1982. ProjectNo. 5956.1 Log No 11029 HETHERINGTON ENGINEERING, INC. DRILLING COMPANY: South Coast Drilling RIG: Tri-Pod DATE: 07/20/07 BORING DIAMETER: 6 Inch DRIVE WEIGHT: 140 Ibs DROP: 30" ELEVATION: 55' +- H W b-l t-l H Q 0.0 5.0- 10.0- 15.0- 20.0- 25.0- 30.0- o o CO s o ij m 31 20 33 49 42 48 56 46 M 2 W Q PS Q o 111 109 111 112 102 104 w D E-l W H o s EH H EH 2 O u 106. ^11 .Jir CO < cn J • u o hJ CO M O D CO — SM 3.4 4.0 6.5 7.5 4.4 3.4 f-2:'3 '-v 4.6 BORING NO. B-1 SOIL DESCRIPTION TERRACE DEPOSITS: Light red brown, silty fine to medium sand, damp, upper 2 feet loose and porous, abundant rodent burrows; below two feet becomes medium dense to dense @ 6' - 8': Light brown silty fine to medium sand, damp to moist, dense @ 8' -10': Color change to orangish red brown @ 10' -19: Orangish red brown fine to medium sand, damp, dense, cohesionless 16' -19': Becomes very dense Total depth 19 feet No groundwater No caving BORING LOG HETHERINGTON ENGINEERING, INC. GEOTECHNICAL CONSULTANTS 3335-45 Lincoln Street Carlsbad, California PROJECT NO. 5956.1 FIGURE NO. DRILLING COMPANY: South Coast Drilling BORING DIAMETER: 6 Inch DRIVE WEIGHT 140 Ibs DROP: RIG: Tri-Pod DATE: 07/20/07 30" ELEVATION: 58' EH H W X EH DJ H a 0.0 5.0- 10.0- 15.0- 20.0- 25.0- EH o o b-l CO S o ^^ m 31 20 33 49 42 48 56 46 >H EH H CO 2 a a >H a o 111 109 111 112 102 104 106 112 u a; D EH CO HH o s EH 2 W EH 2 O o 2.2 4.5 5.5 5.3 4.8 3.4 2.4 2.2 CO ^ CO < CO u o H^ CO H O D CO — SM BORING NO. B-2 SOIL DESCRIPTION TERRACE DEPOSITS: Light red brown, silty fine to medium sand, damp, upper 3 feet loose and porous, abundant rodent burrows; below three feet becomes medium dense to dense @ 3' - 8': Dark red brown slightly silty fine to medium sand, damp, dense to very dense 8' -10': Color change to medium brown @ 10' -16: Orangish red brtftwii fine to medium sand, damp, dense, cohesionless @ 16' -19': Buff, slightly silty fine to medium sand, damp, dense to very dense Total depth 19 feet No groundwater No caving 30.0^ ^ ' ' • • BORING LOG HETHERINGTON ENGINEERING, INC. GEOTECHNICAL CONSULTANTS 3335-45 Lincoln Street Carlsbad, California HETHERINGTON ENGINEERING, INC. GEOTECHNICAL CONSULTANTS PROJECTNO. 5956.1 FIGURE NO. 4 LABORATORY TEST RESULTS DIRECT SHEAR (ASTM: D 3080) Sample Location Angle of Internal Friction C) Cohesion (psf) Remarks B-l @ 13-16' 33 25 Remolded to in-situ dry density and moisture content, consolidated, saturated, drained EXPANSION INDEX (ASTM: D 4829) Sample Location Initial Moisture (%) Compacted Dry Density (pcf) Final Moisture (%) Expansion Index Expansion Potential B-l (a), 0-2' 7.5 111.5v^'-'}j, •\' -19.8 0 Very low B-l m 13-16' 12.6 21.5 0 Very low Figure 5 ProjectNo. 5956.1 Log No 11029 HETHERINGTON ENGINEERING, INC. SOIL & FOUNDATION ENGINEERING • ENGINEERING GEOLOGY • HYDROGEOLOGY August 2, 2007 ProjectNo. 5956.1 Log No. 11043 Barron Investment Group, LLC 1135 Camino del Mar Del Mar, Califomia 92014 Attention: Mr. Jim Schmitz Subject: RESULTS OF SOIL SULFATE TESTING Proposed Condominium Development 3335-45 Lincoln Street Carlsbad, Califomia APN 204-131 -01 through 04 References: Hetherington Engineering, Inc, "Geotechnical Investigation, ProposcPCondominium Development, 3335-45 Lincoln Street, Carlsbad,f:Cj^loniiii \PN 204-131-01 through 04" dated July 26, 2007. Dear Mr. Schmitz: In accordance with your request, Hetheiingiuu I imin..ering, Inc. has completed the laboratory soil sulfate testing. Representative samples of tiif on-site soils were submitted for sulfate analyses. The results ofthe soluble sulfate te^ per H|*A ^038 methods are presented on the attached Laboratory Test Results, Figure I.^^^''^mate content of the on-site soils is consistent with a severe sulfate exposure classificaJtieil^w^TabK 19-A-4 of the 2001 Califomia Building Code. Consequently, a sulfate resistant nti^ie dfesigned per Table 19-A-4 will be necessary for concrete in contact with the on-site soils. This opportunity to be of service is sincerely appreciated. If you have any questions, please call this office. Sincerely, Hetherington Engineering, Inc. Michel A. Vasconcellos Professional Geologist 7934 Certified Engineering Geologist 2411 (expires 1/31/09) MV/MDH/dkw Mark D. Hetherington Registered Civil Engineer 30488 Geotechnical Engineer 397 (expires 3/31/08) Attachments: Distribution: Laboratory Test Results Figure 1 1-Addressee 4-Bha, Inc. Attn: Mr. Steve Bundy 5365 Avenida Encinas, Suite A • Carisbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 327 Third Street • Laguna Beach, CA 92651 • (949) 715-5440 • Fax (949) 715-5442 www.hetheringtonengineering.com LABORATORY TEST RESULTS SULFATE TEST RESULTS (EPA 9038) Sample Location Soluble Sulfate in SoU (%) B-l @0'-2' 0.821 B-l (% 11'- 13' 1.11 B-l (fl), 13'- 16' 0.7780 Figure 1 ProjectNo. 5956.1 Log No. 11043