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Home My WebLink About1032 Cabrillo Avenue - Technical StudyBIOLOGICAL RESOURCE ASSESSMENT for the New Residence at 1036 Cabrillo Avenue - Lot 13 Burlingame, California prepared for City of Burlingame Planning Department 501 Primrose Road Burlingame, CA 94010 650/558-7250 prepared by ENVIRONMENTAL COLLABORATIVE 1268 64"' Street Emeryville, California 94608 510/654-4444 30 December 2002 TABLE OF CONTENTS Setting Background and Methods Vegetation Wildlife Special-Status Species Wetlands Relevant Local Plans and Policies Environmental Impacts and Mitigation Measures Significance Criteria Initial Study Checklist Questions 1 1 1 2 3 3 K3 3 4 APPENDIX A: References 6 BIOLOGICAL RESOURCES SETTING Background and Methods The project site consists of a portion (Lot 13) of a developed property located at 1036 Cabrillo Avenue in Burlingame, California. Most of the lot has been developed with landscaping, pool, patio, retaining walls and other improvements associated with the existing residence on Lot 14. Sanchez Creek flows through the eastern edge of the property. Biological resources associated with the site were identified through a review of available background information and a field reconnaissance survey. Available documentation was reviewed to provide information on general resources in the Burlingame area, presence of sensitive natural communities, and the distribution and habitat requirements of special-status species which have been recorded from or are suspected to occur in the project vicinity. A field reconnaissance survey was conducted by James Martin, principal of Environmental Collaborative, on 18 December 2002 to determine the vegetation and wildlife resources, presence of any sensitive natural communities, potential for jurisdictional wetlands, and suitability of the site to support populations of special-status species. The following provides a summary of the biological and wetland resources on the site, and an assessment of the significance of the potential impacts of project implementation. Vegetation The site consists of part of a developed lot which has been extensively landscaped with trees, shrubs, and groundcovers. No native vegetation remains on the property, with the exception of several small coast live oaks (Quercus agrifolia) which most likely have become naturally established in the yard area northeast of the existing pool. Nine coast redwood (Sequoia sempervirens) grow along the banks of Sanchez Creek through the eastern portion of the site. The creek has been completely channelized across the site. Approximately 45 feet of the creek remains open but channelized and bordered by rock retaining walls. The remainder of the creek is covered across the site by wood and concrete slabs. The entire yard area has been planted with non-native species, with the exception of the redwood and coast live oak trees. These include a groundcover of turf, ferns, periwinkle and ivy, shrubs such as tree fern, bamboo, camellia, juniper, Japanese maple, rhododendron, citrus and other fruit trees, and trees such as fan palm, holly, and English walnut. Wildlife The lack of natural habitat, sparse cover, and frequency of human activity limits the wildlife habitat value of the site. Wildlife associated with the site and surrounding area are common to suburban habitat, consisting of numerous species of birds, raccoon, and opossum. Bird species expected to frequent the site include: America robin, brown towhee, scrub jay, mourning dove, house finch, and several species of sparrow. No evidence of any bird nesting or large mammal denning activity was observed on the site. The creek may occasionally be used as a dispersal corridor for some species of wildlife, but the condition across the site limits its habitat value to wildlife. The entire creek segment across the site has been channelized, precluding establishment of any wetland vegetation. The steep-sided retaining walls limit the likelihood that even more mobile species such as racoon venture outside the open segment on the site. Special-Status Species Special-status species' are plants and animals that are legally protected under the state and/or federal Endangered Species Acts2 or other regulations, as well as other species that are considered rare enough by the scientific community and trustee agencies to warrant special consideration, particularly with regard to protection of isolated populations, nesting or denning locations, communal roosts and other essential habitat. Species with legal protection under the Endangered Species Acts often represent major constraints to development, particularly when they are wide ranging or highly sensitive to habitat disturbance and where proposed development would result in a"takei3 of these species. Records maintained by the California Natural Diversity Data Base (CNDDB) of the CDFG (2002) and other information sources indicate that several special-status plant and animal species have been reported from or are suspected to occur in the Burlingame vicinity. Two very general occurrences of rare plants extend over much of Burlingame, including the site. These are for Franciscan onion (Allium peninsulaYe var. franciscanum) and Hillsborough chocolate lily (FritillaYia biflora var. ineziana), both of which have no legal protective status under the Endangered Species Acts but are maintained on List 1 B of the CNPS Inventory. Both of these species are found in native woodland and grassland habitat typically on serpentine substrate. Suitable habitat for these and other special-status plant species does not occur on the site due to the extent of past and ongoing disturbance, and no special-status plant species are believe to occur on the property. A number of special-status animal species are lrnown from the San Mateo Peninsula. Most of these are associated with coastal salt marsh habitat along the bay and other specific habitat types not found on the site. There is a remote possibility that two special-status animal species may occasionally use Sanchez Creek for dispersal; the federally-threatened California red-legged frog (Rana aurora draytonii) and the federally threatened steelhead - Central California Coast Evolutionarily Significant Unit (Oncorhynchus mykiss). There are no CNDDB records for any 1 Special-status species include: designated rare, threatened, or endangered and candidate species for listing by the California Deparhnent of Fish and Game (CDFG); designated threatened or endangered and candidate species for listing by the U.S. Fish and Wildlife Service (USFWS); species considered rare or endangered under the conditions of Section 15380 of the California Environmental Quality Act Guidelines, such as those plant species identified on lists lA, 1B and 2 in the Inventory ofRare and Endangered Plants of California by the California Native Plant Society (CNPS); and possibly other species which are considered sensitive or of special concern due to limited distribution or lack of adequate information to permit listing or rejection for state or federal status, such as those included on list 3 in the CNPS Inventory or identified as animal "Species of Special Concern" by the CDFG. 2 The federal Endangered Species Act (FESA) of 1973 declares that all federal departments and agencies shall utilize their authority to conserve endangered and threatened plant and animal species. The California Endangered Species Act (CESA) of 1984 parallels the policies of FESA and pertains to native California species. 3"Take" as defined by the FESA means "to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect" a threatened or endangered species. "Harm" is further defined by the USFWS to include the killing or harming of wildlife due to significant obstruction of essential behavior pattems (i.e., breeding, feeding, or sheltering) through significant habitat modification or degradation. The CDFG also considers the loss of listed species habitat as take, although this policy lacks statutory authority and case law support under the CESA. � occurrences of steelhead in Sanchez Creek, but this species may currently utilize accessible segments or could move up the stream in the future if downstream barriers do not preclude access. Similarly, there are no reported occurrences of California red-legged frog within the Sanchez Creek watershed. This species is typically associated with freshwater ponds and pools in riparian corridors with emergent vegetation and protective cover, which is absent from the site. The closest lrnown occurrence of California red-legged frog is approximately 1.5 miles southwest of the site reported in 1989 from an irrigation pond at the Crystal Springs golf course. In the remote instance that either California red-legged frog or steelhead were to utilize the Sanchez Creek corridor across the site, neither would be expected to leave the channel. Steelhead is a completely aquatic species, and although California red-legged frog are known to move considerable distances from aquatic habitat, the near vertical retaining walls and largely covered creek channel preclude dispersal onto the remainder of the site. Wetlands Although definitions vary to some degree, wetlands are generally considered to be areas that are periodically or permanently inundated by surface or ground water, and support vegetation adapted to life in saturated soil. Wetlands are recognized as important features on a regional and national level due to their high inherent value to fish and wildlife, use as storage areas for storm and flood waters, and water recharge, filtration and purification fiznctions. The CDFG, U.S. Army Corps of Engineers (Corps) and California Regional Water Quality Control Board have jurisdiction over modifications to wetlands and other "waters of the United States." Jurisdiction of the Corps is established through provisions of Section 404 of the Clean Water Act, which prohibits the discharge of dredged or fill material without a permit. Regional Water Quality Control Board jurisdiction is established through Section 401 of the Clean Water Act, which requires certification or waiver to control discharges in water quality. Jurisdictional authority of the CDFG over wetland areas is established under Sections 1601-1606 of the State Fish and Game Code, which pertains to activities that would disrupt the natural flow or alter the channel, bed or bank of any lake, river or stream. A preliminary wetland assessment of the site was conducted during the field reconnaissance. The Sanchez Creek channel on the site does not support any wetland vegetation, but would be considered jurisdictional "other waters" by the Corps below the Ordinary High Water Mark (OHWM) and fall under the jurisdiction of the CDFG within the bank and bed of the channel. Relevant Local Plans and Policies The City of Burlingame General Plan does not have any specific policies related to protection of biological and wetland resources which could be interpreted to encompass the site. There is no creek protection ordinance or tree preservation ordinance, other than the Heritage Tree Ordinance which defines a protected heritage tree as having at least a 54-inch circumference at 54 inches above grade. A review of the potential effects of the project on heritage trees was performed separately by Mayne Tree Expert Company (2002). ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES Significance Criteria Criteria have been established in determining the significance of potential impacts on biological resources. The CEQA Guidelines identify potentially significant environmental effects on biological resources to include: 3 • a substantial adverse effect, either directly or through habitat modifications, on any special-status species; • a substantial adverse effect on any riparian habitat or other sensitive natural community identified in local or regional plans, policies, or regulations, or by the CDFG or USFWS. • a substantial adverse effect on federally protected wetlands as defined by Section 404 of the Clean Water Act through direct removal, filling, hydrological interruption, or other means; • interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites; • conflict with any local policies or ordinances protecting biological resources, such as a creek preservation policy or ordinance. • conflict with the provisions of Community Conservation Plan, conservation plan. an adopted Habitat Conservation Plan, Natural or other approved local, regional, or state habitat Initial Study Checklist Questions a) Have a substantial adverse impact on a candidate, sensitive or special-status species? No Impact Essential habitat for special-status species is generally absent from the site, and no adverse impacts on special-status species are anticipated. The extent of past development and on-going maintenance of the property precludes the occurrence of any special-status plant species or essential habitat for special-status animal species on the site. In the remote instance that either steelhead or California red-legged frog were to disperse along the Sanchez Creek corridor on the property, neither of these species would be expected to move outside the creek itself due to the near vertical retaining walls and culverting of most of the channel. The project would not have any direct impacts on the creek or channel banks and no adverse impacts would occur to either of these species, even in the remote instance that they were utilizing the creek corridor for dispersal. No mitigation is required. b) Have a substantial adverse impact on any riparian habitat or other sensitive natural community? No Impact. Sensitive natural community types are absent from the site, and no adverse impacts are anticipated. The only native species on the site, the redwood and oak trees, would be avoided as part of the project. These native trees do not comprise a sensitive natural community. No mitigation is required. c) Have a substantial adverse impact on federally protected wetlands? No Impact. No wetlands occur along the segment of Sanchez Creek which crosses the site, and the project would not affect the bank, bed or channel below the OHWM. No impacts on jurisdictional � wetlands or other waters are anticipated and no coordination with the Corps or CDFG is required assuming construction is restricted outside the creek channel. The following measure is recommended to ensure avoidance of potential impacts on jurisdictional waters: Mitigation Measure 1: The proposed project shall avoid any disturbance to the bed or bank of the Sanchez Creek channel across the site. Construction fencing shall be placed along the top of the retaining wall bank on the west side of the creek and shall extend along the west side of the redwoods to be protected. No construction activities or disturbance shall be allowed within this zone without prior approval of a qualified biologist and approval of jurisdictional agencies, if required. d) Interfere with movement of native fish or wildlife species or quality of native wildlife habitat? No Impact. Proposed improvements would have little effect on wildlife resources at the site due to the extent of past disturbance and avoidance of the Sanchez Creek channel. The mature redwood trees would all be avoided, with protective fencing installed around the trees as called for in the report by Mayne Tree Expert Company. Wildlife species common in suburban habitat would continue to frequent the site following completion of construction. New landscaping and the new residence would provide suitable habitat for species common in suburban areas, and no significant impacts are anticipated. No mitigation is required. e) Conflict with local policies or ordinances protecting biological resources? No Impact. The project would not conflict with any goals and policies of the City of Burlingame regarding protection of biological and wetland resources, and no adverse impacts are anticipated. No mitigation is required. fl Conflict with an adopted Habitat Conservation Plan orNatural Community Conservation Plan? No Impact. The proposed project would not conflict with any adopted Habitat Conservation Plan, Natural Community Conservation Plan or other approved conservation plan. No such conservation plans have been adopted encompassing the proj ect vicinity, and no impacts are therefore anticipated. No mitigation is required. 5 . REFERENCES California Department of Fish and Game, Natural Diversity Data Base, 2002, Recard Search of the San Mateo and Montara Mountain USGS Quadrangles, 12 April. California Depariment of Fish and Game, Natural Diversity Data Base, 2002, List of California Terrestrial Natural Communities Recognized by the California Natural Diversity Data Base. California Department of Fish and Game, 2002, Natural Diversity Data Base, Special Animals. California Department of Fish and Game, 2002, Natural Diversity Data Base, Special Plants. California Native Plant Society, 1988, Terrestrial Vegetation of California. California Native Plant Society, 2001, Inventory of Rare and Endangered Plants of California, Special Publication No. 1(6th Edition). Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe, 1979, Classification of wetlands and deepwater habitats of the United States, U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. Environmental Laboratory, 1987, Corps of Engineers wetlands delineation manual, Technical Report Y-87-1, U.S. Army Engineer Waterways Experiment Station, Vicksburg, Miss., dated January. Hall, E.R., 1981, The mammals of North America, University of California Press, Berkeley. Hickman, J.C. 1993, The Jepson manual: higher plants of California, University of California Press, Berkeley, California. Mayne Tree Expert Company, 2002, letter to Mr. Otto Miller regarding 1036 Cabrillo, Lot 13, from Richard L. Huntington, dated 20 December. Munz, P. and D. Keck, 1973, A California Flora and Supplement. Peterson, R.T., 1969, Field Guide to Western Birds, Houghton Mifflin Company, Boston. Stebbins, R.C., 1985, A Field Guide to Western Reptiles and Amphibians, 2nd Edition, Houghton Mifflin Co., Boston. Sawyer, J.O. and T. Keeler-Wolf, 1995, A Manual of California Vegetation, California Native Plant Society, Sacramento. 7 ��I°�� .�; r � � � � �, j c- �r i..l..� i �r i �� `. _. . � . t.f `� �'i; i.,. !� i_ F`. r'� 11 i'V I_,, ,_ )!` i� �. GEOTECHNICAL SITE INVESTIGATION 1032 Cabrilli Avenue Burlingame, California Y & A J02 - 1040 By Jae H. Yang - Project Engineer J. YANG AND ASSOCIATES � J. Yang and Associates GEOTECHNICAL / ENVIRONMENTAL CONSULTING ENGINEERS 2758 CANYON CREEK DR. • SAN RAMON, CA 94583 (925) 831-8678 � FAX (9�5) 831-3645 Project No. J02-1040 September 2, 2002 Mr. Otto Miller Subject: Proposed Residence at 1032 Cabrillo Ave Burlingame, California Geotechnical Site Investigation Dear Mr. Miller: In accordance with your authorization, J. Yang and Associates has investigated the geotechnical site conditions at the subject site of the proposed of housing development in Burlingame, California. The accompanying report presents our conclusions and recommendations based on our investigation. Our evaluations indicate that the site is physically suitable for the proposed construction provided the recommendations of this report are carefully followed and are incorporated into the plans and specifications. Should you information, convenience. have any questions or require additional please contact our office at (925)831-8678 your Very Truly Yours, J. Yang and � �� sociates Proj ect Gec�. �ngineer Project No.J02-1040 TABLE OF CONTENTS Page No. LETTER OF TRANSMITTAL GEOTECHNICAL ENGINEERING INVESTIGATION Site Location and Description Purpose and Scope FIELD EXPLORATION AND LABORATORY TESTING GEOTECHNICAL EVALUATION AND DISCUSSION Site Geology and Slope Stability Subsurface Soil Condition 1 1 � 3 5 5 CONCLUSIONS AND RECOMMENDATIONS 6 General 6 Site Preparation and Grading 7 Surface and Subsurface Drainage 8 Foundations 8 Retaining Walls 9 Slab-on-Grade Floors 10 Flexible Pavement 11 Trench Backfill/Observation and Testing 12 PLAN REVIEW, CONSTRUCTION OBSERVATION GUIDELINES FOR REQUIRED SERVICES 14 15 LIMITATIONS AND UNIFORMITY OF CONDITIONS 17 APPENDIX AA Site Plan, Boring Location and Boring Logs J. YANG AND ASSOCIATES Project No. J02-1040 I. INTRODUCTION A. Location and Description of Site This report presents the results of a site investigation performed by J. Yang and Associates for the property of 1032 Cabrillo Ave., Burlingame, California. (See PLATE 1-Location Map). The site was investigated by J. Yang and Associates on August 26, 2002. The property is located at south-east corner of Carmelita Ave and Cabrillo Ave. The ground slopes down to the existing creek from the site. The site is currently well developed flat lot with swimming pool and facilities. Most of the site is covered with grassland, concrete slab and pool. Development plans call for construction of a new single family residence. B. Purpose and Scope of Work The purpose of our site Investigation for the proposed family dwelling house at 1032 Cabrillo Ave, Burlingame, California was to determine surface and subsurface soil conditions at the subject site. Based on the results of the investigation, criteria were established for the grading of the site, the design of foundations for the proposed structures, and the construction of other related facilities on the property. Our investigation included the following: 1. Field reconnaissance by the Soil Engineer 2. Drilling and sampling of the subsurface soil. 3. Laboratory Testing. 4. Analysis of the data and formulation of conclusion and recommendations. 5. Preparation of this written report. 1 J. YANG AND ASSOCIATES Project No. J02-1040 II. FIELD EXPLORATION AND LABORATORY TESTING Subsurface conditions were explored on August 26, 2002 by drilling two borings. The boring location were chosen to provide subsurface information at the major structure areas. The boring locations are shown on PLATE 3. The.boring were drilled with Mobile B-29 Flight Auger. Our soil engineer logged the boring and obtained bulk and relatively undisturbed drive samples for visual classification and subsequent laboratory testing. Drive samples were obtained with the Spraque and Henwood(S&H) split barrel sampler ( 2-inch I.D.) equipped with brass liner tubes. The samplers were driven with a 140-pound hammer falling 30- inches. Standard penetration test N-values obtained with the SPT sampler and approximate "Equivalent" N-value obtained with the S&H split-barrel sampler. Results are shown on the boring logs in PLATE 4. The soils encountered were described in accordance with the Unified Soils Classification System outlined in PLATE A1. 2 J. YANG AND ASSOCIATES -��{:7 --"MILLBR E ' `� S�c �� 8 Zj,W 1y0 N�04 � i -�� 9 E. µ,�, MUP S P� C� � j y � n j78 . DR y QQ � Sti. S �< I -. 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Po' ''� _� � El PD. � _ 'HN G7" tON PD. G WY PE�� y p'�-,p� t� o pP .- s1P c,t __ - 9_ _ GiM� OP Q}� ' .� _ W S�FP ' BURUNGAME. � � �� - EPN11T n i I ��. .- '�' f : F F" _ � i � .� uam�-se , EO,IlMRY . �p . . ;'� aQ � HILLSBOROUGH" 'OLUB 000�1. ��p�ACE . ,RD:-�; `,� - " `SjoN �ai� 9 RP CEDPP �,19 '�� '_ � t G < CT. ��" �ce ■5]�5 BPVBEPAY 9'tJ'�OE �� P�' � Q P�. ,`BpWPN1PEE N' � ,1�,1� �29 BPRROITH�u �� LOCATION MAP i,., � qL . �� q,, V� M'i( l- R�N� G NEN�: fl0. 51 p ' y, 5 �c �Py.OPE PV. ^ ��p11N i �Q tuo _ 6t ' Py. B�yEVUE \ A�. S�N M41E0 PERFMM1u1IG AIiTS CFIlIEA i�s ..�.: PLATE 1 Project No. J02-1040 III. GEOTECHNICAL EVALUATION AND DISCUSSION A. Assessment of Seismic Hazards This site could be affected by an earthquake with its epicenter of the active faults in the Bay Area. At present, it is not possible to predict when or where movement will occur on these faults. It must be assumed, however, that movement along one or more of these faults will result in a moderate earthquake during the lifetime of any improvements at this site. Three active fault systems are known to exist within a vicinity of the site. The approximate location of these faults are as shown on PLATE lA. In the event of an earthquake, seismic risk to a structure will depend on the distance of the structure from the epicenter and source fault, the character and magnitude of the earthquake, the groundwater and soil conditions underlying the structure and its immediate vicinity, and the nature of the construction. The potential seismic hazards in the tests area are the affects of ground shaking resulting from earthquakes on nearby faults. Regional subsidence or uplift caused by a differential vertical movement along a fault takes place over large areas. In the event of such movement on the San Andreas Fault, the site would probably respond as a unit, resulting damage from this phenomenon is unlikely. Structural damage due to ground shaking is caused by the transmission of earthquake vibrations from the ground into a structure. The variables which determine the extent of damage are: the characteristics of the underlying earth materials, the design of the structure, the quality of materials and workmanship used in construction, the location and magnitude 3 J. YANG AND ASSOCIATES Project No. J02-1040 of the earthquake, and the duration and intensity of shaking. The most destructive effects of an earthquake are usually seen where the ground is unstable and the structures are poorly designed and constructed. Preliminary estimates of ground response characteristics at this site indicate that high accelerations can be expected during a moderate to major earthquake on the San Andreas Fault or a major earthquake on the Hayward fault or Canada Faults. Any of these events could cause strong ground shaking at this site. The duration of shaking and the frequency components of the vibrational waves will depend upon the magnitude and location of the earthquake. Structures should be designed to accommodate earthquake vibrations. If quality design and construction criteria are met, as set forth in the latest edition of the Uniform Building Code. B. Site Geologic and Site Stability The natural slopes on and near the site are relatively flat and show generally good site stability. In accordance with Geotechnical Hazards Synthesis Map(12/76) San Mateo County (Hazard Area Zone 8) that geologic materials are Santa Clara Formation. the Santa clara formation is principally a coarse-grained, fluvial deposit of conglomerate, sandstone, and claystone. these members of Purisima formationvary in composition from fine grained sandstone, silty mudstone ans procellaneous shale. The near-surface soils at the site are cohesive and are relatively resistant to erosion. However, clay material may be exposed locally, and fill may be composed of granular material. The granular material would be susceptible to erosion in unprotected. Additionally, the cohesive material could erode if grounds are left unplanted and subjected to fast flowing runoff. Recommendations are presented in this report which are intended to mitigate problems associated with erosion. 4 J. YANG AND ASSOCIATES Project No. J02-1040 C. SUBSURFACE SOIL CONDITIONS Based upon examination of the exploratory boring (See PLATE 4: Boring Logs). materials encountered in the two borings, at locations shown on PLATE 3. The subsurface soils consist generally of well consolidated clay and well consolidated silty clay layers. These materials generally grade from dense in relative density near the ground surface and hard at below 15 feet to greater depths. Our observation of the soil on the core samples indicated that the materials encountered in the two exploratory boring are generally two different layers with the materials observed on the core samples. Groundwater was not encountered at the time of our investigation at average depth of 15 feet. Detailed descriptions of materials encountered in each of the test boring are presented on the logs in Plate 4. Changes in the condition of the property may occur with the passage of time due to natural processes and on the subject site of adjacent properties. Thus, the drilled boring logs and related information depict subsurface conditions only at the locations indicated and on the particular date designated on the logs. Soil conditions at other locations may differ from conditions at these locations. 5 J. YANG AND ASSOCIATES �x ``°m �S. �`°'°�'' �""`, PLATE lA� �s-minuts awannysa u ina;caua Phoiorcviiion u of 197! MAP OF PART OF CENTRAL CALIFORNIA SHOWING LOCATION OF STRIP MAP SEGMENTS Project No. J02-1040 IV. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based on the investigation and evaluations described in this report. The recommendations and specifications presented herein should be incorporated into the project plans and documents during design and construction. A. General Conclusions l. The site is considered suitable from a geotechnical aspect for the proposed a family dwelling houses. 2. There were no soil or geologic conditions encountered during the investigation of the site which would preclude the planned construction. 3. The site, as is all the San Francisco Region, is in a seismically active area. Ground shaking is expected to have the following characteristics at the site and parameters are recommended: a. Seismic zone factor (Z) = 0.4 b. Seismic coefficient (Ca)= 0.45Na c. Seismic coefficient (Cv)= 0.64Nv d. Soil profile type = Sd e. Near-Source factor (Na)= 1.5, (Nv)=2.0 f. Seismic source type= A 4. The potentials for the secondary seismic effects of liquefaction is considered to be low at the site. 5. The potential for seismically-induced landsliding to occur is not considered at this site. 6. The recommendations in this report are based on the assumption grading will minimal. When final development plans and detailed grading plans are available, the conclusions and recommendations of this report should be reviewed and modified if necessary, to suit those plans. 6 J. YANG AND ASSOCIATES Project No. J02-1040 Site Preparation and Gradinq 7. All grading operations associated with the planned development should be carried out as described in the following paragraphs. 8. Remove all organically contaminated soil, root systems and loose or soft soil in the areas of the planned development. Buried structures such as pipelines, other underground facilities should be removed from the areas of planned development. The existing swimming pool shell should be removed and compacted backfill with 95% minimu of relative compaction per County Environmental-Health requirements. 9. Al1 compaction requirements are based on maximum dry densities and optimum moisture determined by ASTM Test Procedure D1557-90. 10. After stripping, areas to receive fill should be stripped to firm natural ground, scarified, moisture-conditioned to 3 to 5% above optimum moisture content, and compacted to at least 90% relative compaction. If soils are too wet, considerable drying time and discing may be required to reduce their moisture content to near optimum. Where cut natural ground is exposed beneath slabs-on-grade, the soil should be scarified to a depth of 5 inches, moisture conditioned as above, and compacted between 90% to 95% relative compaction. 11. Existing natural dark clay top soils may not be used as compacted fill in building and street areas, provided it is free of organic or other deleterious material. All fill should be compacted to at least 90% relative compaction at moisture contents 3 to 5% above optimum. The upper 24 inches of fill within pavement right-of-way should be compacted to at least 95% relative compaction. 0 � J. YANG AND ASSOCIATES Project No. J02-1040 12. Import fill, if used, should be approved by the Soil Engineer, and should have soil properties equivalent to or better than the natural soil. Import fill should not contain rocks larger than 4 inches in diameter. Surface and Subsurface Drainaqe 13. All grading at the site should be done in such a manner as to prevent ponding of water during or after construction. Positive surface drainage should be provided adjacent to any structures and pavements such that all surface waters are directed away from the foundations. Water should be directed into drop inlets and closed pipes that lead to suitable discharge facilities. Rainwater collected on the roof of the building should be transported through gutters, downspouts and closed pipes to suitable discharge facilities. In general, the soils at the site are cohesive and are not prone to erosion. 14. If there are any swales or draws which will be filled should be provided with subdrains to collect and discharge and subsurface seepage flow. Typically, subdrains will be perforated plastic pipe surrounded with select import filter material. The subdrains should be connected at their low points to a storm drainage system or to other approved discharge points. Subdrain outlets should be protected from erosion and siltation and be noted on "as-built" plans by the project Civil Engineer for future reference. Foundations 15. Top 2 ft. of soil is dark clay which is potential expansive. The proposed building structures should be founded on the firm soil. Recommendation for pier and grade beams are presented in this report. 8 J. YANG AND ASSOCIATES Project No. J02-1040 16. The following general foundation type may be used at this site. Final selection of appropriate foundation systems will depend on the building structural engineer's preference within this report. Drilled Cast-In-Place Concrete Piers and Grade Beams The diameter of the piers should be a minimum of 16 inches and a minimum depth of 13 feet from bottom of the grade beam. The actual depths of piers will be � determined at the time of drilling by soil engineer. The piers for these foundation systems should be transit structural loads to the subsurface soils. The drilled piers will derive their load carrying capacity from peripheral skin friction between the pier shaft and the surrounding soil. An allowable skin friction value of 500 pounds per square foot (psf) of embedment may be used for design purposes for combined dead plus live loads. This value is applicable to both downward and for uplift resistance. Friction resistance in the upper portion of the pier within 18 inches of the ground surface should be neglected when determining the load carrying capacity of the piers. The pier should be reinforced their entire length and spaced at least three pier diameters. 7. If retaining walls are required as part of the building, the design criteria recommended for the building foundations are to be used. A combination of spread footings with key or pier foundation system may be combined for retaining wall footings. The retaining wall should be designed to resist lateral pressures exerted from a media having an equivalent fluid weight as follows: Gradient Equivalent Passive Coefficient Angle of of Back Fluid Weight Resistance of friction Internal Slope pcf pcf Friction Flat 50 350 0.25 30 2: 1 65 350 0.25 30 9 J. YANG AND ASSOCIATES Project No. J02-1040 Drainage behind retaining walls should consist of a 4-inch diameter perforated pipe surrounded by permeable drain material described below. b.1. Concrete Slab-on-Grade Floors All concrete slab-on-grade floors should be supported on a minimum of 6 inches of Class 2 aggregates fill. Slab subgrades should be rolled smooth prior to slab construction to provide a uniformly dense non-yielding surface. This material should be compacted with a vibratory roller and conform to the gradation criteria presented as following: Sieve Size Percentage �U.S. Series) Passinq 1 inch 100 3/4 inch 90-100 No.8 0-10 No.16 0-5 No. 200 0-3 Moisture vapor is likely to condense on the under side of slab-on-grade floors. If the moisture vapor is desirable, a synthetic membrane can be placed over the capillary break. b.l) Permeable Drain Material Sieve Size Percentage (U.S. Series) Passinq 1 inch 100 3/4 inch 90-100 3/8 inch 40-100 The zone of drain material should be at least 12 inches wide and should extend to the bottom of the walls. Unless pavements or concrete slabs extend to the back of the wall, the upper 12 inches of backfill should consist of clay to minimize 10 J. YANG AND ASSOCIATES Project No. J02-1040 infiltration of surface water. The perforated pipe along the base of the wall should be placed with the perforations down and should have a minimum 2 percent slope to drain by gravity to a suitable discharge location. Clean-out pipes that extend to the ground surface should be provided at every bends to allow for cleaning, should the pipe become clogged. Drainacre All ground surfaces, including pavements and sidewalks, should slope away from the structures at a gradient of at least 2 percent. Surface runoff should be controlled by a system of swales and catch basins, and then conveyed off the property to suitable discharge facility. Surface water should not be allowed to pond on the site. In addition, roof downspouts should be connected to closed collector pipes which discharge into the storm water system or onto paved parking areas or dispose through lined ditch. Flexible Pavement Thicknesses Based on an assumed R-value of 20 (typical clayey sand and clay mixtures), Assumed Traffic Indexes (T. I. ) and the CALTRANS design procedure for asphaltic concrete pavement, we recommend the following preliminary asphaltic concrete pavement thicknesses: Thickness (inches) Asphaltic Class 2 Location T.I. Concrete AggregateBase* Automobile 4 2 5 Parking Driveways and 5 3 6 Service Areas 11 J. YANG AND ASSOCIATES Project No. J02-1040 R-Value -70 minimum the subgrade soil may vary in quality and contain local areas of low shear strengths. We should observe the completed subgrade to check that the preliminary pavement design is applicable. Subgrade soils to receive pavement should be rolled to provide a smooth, unyielding surface compacted to at least 95% relative compaction. On site subgrade soils should be maintained in a moist condition until covered the completed pavement section. The Class 2 Aggregate Base should be placed in a manner to prevent segregation, uniformly moisture conditioned to near optimum and compacted to at least 95% relative compaction with a smooth and unyielding surface. Trench Backfill 18. Underground utility trenches may be backfilled with on- site brown silty clay soils, provided they are moisture- conditioned to near optimum and are not in "chunks". Bedding and initial backfilling should be done in accordance with local requirements and specifications. Subsequent backfilling should be done in accordance with local requirements and specifications. Subsequent backfill (generally one foot and higher above the utility) should be placed in layers and mechanically compacted as follows: Trench Location Natural ground, outside street and lot areas. Lot areas and streets, below upper 24 inches. Street areas, upper 24 inches. Minimum Relative Compaction 85% 90% 95% 12 J. YANG AND ASSOCIATES Project No. J02-1040 Observation and Testinq 19. All work connected with site grading, drainage and erosion control should be observed and tested by the Soil Engineer and Engineering Geologist. The purpose of these services will be to confirm that the conditions exposed during grading are as anticipated and provide supplemental recommendations if required; and to determine that the site work is being done in general conformance with the recommendations of this report and the city of Burlingame requirements. Additional Soil Engineering Service 20. We should review the final design and specifications in order that earthwork and foundation recommendations may be properly interpreted and implemented in the design and specifications. We should provide engineering services during site preparation, grading, foundation and pavement construction phases of the work. This would allow us to observe compliance with the design concepts, specifications and to allow design changes in the event that surface conditions differ from those anticipated prior to the start of construction. 13 J. YANG AND ASSOCIATES Project No. J02-1040 V PLAN REVIEW CONSTRUCTION OBSERVATION AND TESTING We should be retained to review the earthwork and foundation plans and specifications for conformance with the intent of our recommendations. The review would enable us to modify our recommendations if final design conditions are not as we now understand them to be. During construction, we should observe and test the earthwork and foundation installation. As needed during construction, we should be retained to consult on geotechnical questions, construction problems, and unanticipated conditions. This will allow us to develop supplemental recommendations as appropriate for the actual soil conditions encountered and the specific construction techniques employed by contractor. 14 J. YANG AND ASSOCIATES Project No. J02-1040 VI. GUIDELINES FOR REQUIRED SERVICES The following list of services are the services required and must be provided by Yang and Associates, during the project development. These services are presented in check list format as a convenience to those entrusted with their implementation. The items listed are included in the body of the report in detail. This list is intended only as an outlined of the required services and does not replace specific recommendations and, therefore, must be used with reference to the total report. The importance of careful adherence to the report recommendations cannot be overemphasized. It should be noted, however, that this report is issued with the understanding that each step of the project development will be performed under the direct observation of Yang and Associates. The use of this report by others presumes that they have verified all information and assume full responsibility for the total project. 15 J. YANG AND ASSOCIATES Project No. J02-1040 ITEM DESCRIPTION REQUIRED NOT REQUIRED 1. Provide foundation design parameters X 2. Review grading plans & specifications X 3. Review foundation plans & specs. X 4. Observe & provide demolition recommendation X 5. Observe & provide site stripping X recommendations 6. Observe and provide recommendations on moisture conditioning, removal and/or X precompaction of unsuitable existing soils 7. Observe and provide recommendations on X installation of subdrain facilities 8. Observe and provide testing services on X fill areas and/or imported fill materials 9. Review as-graded plans and provide additional X foundation recommendations, if necessary 10. Observe and provide compaction tests on sanitary sewers, storm drain, water lines X and PG&E trenches 11. Observe foundation excavations and provide supplemental recommendations, if necessary, X prior to placing concrete 12. Observe and provide moisture conditioning recommendations for foundation areas prior X to placing concrete 13. Provide design parameters for retaining walls X 14. Provide geologic observations and recommendations for keyway excavations and X cut slopes during grading 15. Excavate and recompact all geologic trenches X and/or test pits. 16 J. YANG AND ASSOCIATES Project No. J02-1040 VII. LIMITATIONS AND UNIFORMITY OF CONDITIONS A. The recommendations of this report are based upon the assumption that the soil conditions do not deviate from those disclosed in the borings and test pits. If and variations or undesirable conditions are encountered during construction, or if the actual construction will differ from that planned at the present time, J. Yang and Associates should be notified so that supplemental recommendations can be given. B. This report is issued the understanding that it is responsibility of the owner or of his representatives to ensure that the information and recommendations contained herein are called to the attention of the other members of the design team (architect and engineers) for the project and are incorporated into the plans, and that the necessary steps are taken to see that the contractors and subcontractors carry out such recommendations in the field. C. The findings of this report are valid as of the present date. However, changes in the conditions can occur with the passage of time, whether they be due to natural processes or to the works of man, on this or adj acent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated, wholly or in part, by changes outside of our control. Therefore, this report is subject to review by J. i�ang and Associates after a period of three(3) years has elapsed from date of issuance of this report. D. The body of the report specifically recommends that J. Yang and Associates be provided the opportunity for general review of the project plans and specifications, and that J. Yang and Associates be retained to provide observation and testing services during construction. The validity of this report assumes that J. Yang and Associates will be retained to provide these services. 0 1� J. YANG AND ASSOCIATES Project No. J02-1040 E. This report was prepared at your request for our services, and in accordance with the currently accepted geotechnical engineering practice. No warranty based on the contents of this report is intended, and none shall be inferred from the statements or opinions expressed herein. 18 J. YANG AND ASSOCIATES �1PPENDIX AA M W � J � C7 z � 0 �a w 0 z 0 � H � U O � � . J , ..-... ... .. ...r..., . .9..� ..4..--... �..... _i.-... " .... __ _ - a_.. MAJOR DIVISIONS TYPICAL NAMES GW ' � WEII�GRADED GRAvELS. GRAVEL SAND �::%.__. MIXTURES w CLEAN GRAVELS WITH > LITTLE OR NO FINES � GRAVELS GP ,'�� pppRLY GRADED GRAvELS. GRAVEL SArvD • _.;,�; MIxTURES J � MORE THAN HAIF � O CAARSE FRACTION GM S�ITY GRAVEIS. POORLY GRADED GRAVEL- � IS LARGEH 7HAN SAND SILT MIXTURES z No. 4 StEVE S�ZE GRAVELS w�TH OvER wF 12%. FINES GC ��qYEY GRAVEIS. POOR�Y GRADED GRAVEL Z W SAND CLAY MIXTURES Q � Q • • � g SW �� WELL-GRADED SANUS. GRAVEILY SANDS 'n • • � CLEAN SANOS WITH w Q SANDS LITfIE OR NO FINES ��'� (n = SP �� POORLY GRADED SANOS. GHAVELLY SANDS Q Q • . . O � MORE THAN HALF . U w ��SE FRACT�ON SM • • SILTY SANOS. POORLY GRADEO IS SMALLEH THAN • SANO SILT MIXTURES O NO 4 SIEVE SIZE SANDS WITH OVER • • � 12% FINES • • • SC CLAYEY SANDS. POORLY GRADED ' ' ' SAND-CIAY MIXTURES . . • INORGANIC SILTS AND VERY FIIvE SANDS. ML ROCK FLOUR, SILTY OR CLAYEY ftNE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY �% ¢ INORGANIG CLAYS OF LOW TO t�tEnIUM J � SILTS AND CLAYS CL PLASTICITY, GRAVELLY CLAYS. SANDY CIAYS. J � a"' LIOUID LIMIT 50°/s OR LESS SILTY CIAYS. LEAN CIAYS ��w Q N'� �L � �( ORGANIC CLAYS AND ORGANIC S1�7Y CLAYS W LL g ' i i i i Of LOW PLASTICITY Z JQ N �_ � INORGANIC SILTS. MICACEOUS OR Q Z MH DIATOMACEOUS FiNE SANDY OR SIITY �. F Q SpILS. ELASTIC SILTS x W¢~ SILTS AND CLAYS CH INORGANIC GLAYS Of HIGH PLASTICITY. FAT � CIAYS z� LIOUID LIMIT GREATER THAN 50°/. LL �/ ORGANIC CLAYS OF MEDIUM TO HIGH OH �//� p�STiC17Y, ORG�NIC SILTS / HIGHLY ORGANIC SOILS Pi PEAT AND OTHER HIGH�Y OR('ANIC SOILS UNIFIED SOIL CLASSIFICATION SYSTEM Perm — Consol — LL — PI — GS — MA — � — � — -200 — Permeability Consolidation Liquid Limit ( %) Plaslic Index (%) Specilic Gravity Parbcle Size Analysis "Undisturbed" Sample Bulk or Classilication Sample % Finer No. 200 Sieve Consislcncy N(Stnndv�d Sqerare Jootings Conrinuous joorings oJsoil penetration AIIoK•ablt b�nring rons/sq ft resislance) pr�ssure Very soft Q-2 0.00-0.30 OZ2 Soft 2-d 0.30-0.60 0.22-0.45 Medium 4-8 0.60-1.20 0.45-0.90 Stiff 8-15 1.20-2.40 0.9a1.80 Vcry stiff 15-30 2.40-4.80 1.80-3.60 Hard 3U 4.80 3.60- KEY TO TEST DATA IL CLASSIFICATION CHART PLATE 8 KEY TO TEST DATA A1 ! DRAWN . ,IpB NUMBER _ AVCROVED WTE REV�SED WTE PROJECT 1032 Cabrillo �Ve BORING NO. Burlingame, CA EB - 1 BORlNG SUPERVtSOR J. Yang E��NG �� DATE OF BORIP}G - Power Minuteman, 4 8-26-02 HAMMER WEIGHT 140#/30" drop W „_ � W � U Z SURFACE ELEVATION � � � � � Z a ¢ ATD D � z o �w z o �v�fz-- �F-�- GROUND WATER ELEVATION z w W � a w � �� c� cn � a a ?� � � w O� DESCRIPTION OF MATERIALS w a Q� o � —Q �� p � f A � a] � 2 �� t n Silty clay/clayey sand, dark brown. Silty sand, dark brown, moist, some EB1 weathered coarse sand. 5 4 2" 25 105 25 1.9ksf Silty clay, clayey sand, brown, moist, �� EBO 2" 20 100 18 2.5ksf stiff . 15 Bottom of hole 20 25 30 JOB NO. J02-1040 �• YANG AND ASSOCIATES F��' Consulting Engineers PLATE 4 PROJECT 1032 Cabrillo Ave BORtNG NO. Burlingame, CA EB - 2 BORING SUPERVISOR .T . Yang ��NG t� DATE OF BORING - Power Minuteman, 4 8-26-02 HAMMER WEIGHT 140#/30" drop � W ,� z U � U SURFACE ELEVAT}ON ~ �' a � � � �'� '� g , `�Z= �n ¢ ATD D r` z o a� w z , ��►- � F-- GROUND WATER ELEVATION z W W � a w � �� c� v� � a a ?� � � w O� w a � aZc � � � � DESCRIPTION OF MATERIALS o�, �, o m o � �� Silty clay/clayey sand, (topsoil) Silty clay, damp, dark brown. EB2 5 5 2" 14 104 27 1.2ksf Silty clay, brown, moist, stiff. EB2 �� 1D 2" 16 100 25 1.4ksf 15 Bottom of hole 20 25 30 �°B No. J. YANG AND ASSOCIATES F��O' J02-1040 Consu/ting Engineers PLATE 4 i2i31izee2 es:5s 6503408435 MILLERDEVELOPMENT PAGE 02 Mayne Tree Expert Company, Inc. ESTABLISHEU 1931 STATE CONTRACTOR"S LICENSE N0. 27F793 GRADUATF FORF.STER • CL:RTIFII.iU ARHORISTS • PEST CONTROt • AnVISORS AND OPERA�I�OR:S RIC'IiARD I.. HUN'I"INCiTUN 535 dRAGA'1�0 RQAU. $TFi, A PRk:Sir)IaN'r 5AN CAKLQS, C:A 94070-6228 K►�viN R. Kir•,�1'v December 20, 2002 TTI.F:pNUNF:: (6501 593-4400 UPI{R.ATIVNS MANAGER FACSIMII_E: (65U1 593-4443 EMAfL: ml'o(u)maynctrte.com Mr. Otto Miller Miller Development P.O. Box ] 2l Burlingame, CA 94010 Re: ]036 Cabrillo, Lot 13, Burlingame Dear Mr. Miller: On December 16, 2002, we met at the above referenced site. This lot is to be developed with the pier and grade beam foundation staying at least 10 feet from any redwood. The purpose of this visit was to: 1. �nspect only the Heritage Trees with at least a 48 inch Circumference at 5� inches above gradc. 2. Determine individua) tree condition which is a combination of general health and structure per the #ollowin� tablc. U-29 ... Very poor 30-49 ... Poor 50-69 ... Fair 70-89 . . . Good 90-700 .. Excellent 3. Determine potential cc�nstruction impacts. 4. Mitigation of impactc if they occur. ,3i2e02 15:51 6593408435 MILLERDEUELOPMENT PAGE 03 Miller 12-20-02 5. Outline tree protertion. There are only � Heritage Trees which would poter►tially be impacted by tlte proposed construrtion. They are the 4 redwoods along the north side of the stream. The redwoods on the south side will not be impacfied by the pxoposed construction. Regarding any other important tn�es: the small tzees southeast of the proposed home are to zemain. The following is the re�tnarks on the individual trees: Tree No. l is the 86.� inch circumferenre �ed�d This tree is in good condition with a 7596 rating. Proposed conshvction is planned to be 10 feet away with only minimal impact expected. No mitigation is needed. Ttee No. 2 is s 156.1 inch circumferetue redwood and is in good condition (80% rating). The �roposed constructivn is to be 14 feet away and there are no expected i�pacts. No xnitigation needed. Tree No. 3 is � 93.3 inch circumference ndwood and is ixt good condition (7596 raHng). Proposed construction is planned ta be 14 feet away and �no impacts are expected. There is no mitigallon needed. Tree No. 4 ie a 73.5 iach circumferei►ce redwood. It is i�n good condition (7096 zating). The proposed construction is plaruted tv be 12 feet away. O�t�ce again, there are no expeMed impacfis and no mitigation is needed. To conclude, the pcoposed structuire will not it�tpact the 4 redwoods alo�tg the streamt. To help insure tree pxotection, install fencing alo�tg the south side of the lowest rock wall north Of the trees to separate the trees hom the constiuCtion site. A further piOtective measure is that all work will be done on the upper area north of the z+edwoods. I be�ieve this report is ac�urate and based on sound aboricultuzal principles and practices. Sincerely, S, / r � � �,ry�� ' �,, NUNr,� � �`o s Np, WC,0119 � . *, Richard L. Huntington Certified Arborist WC +�0119 RLH:dcr '?3;2602 15:51 6503408435 MILLERDEVELOPMENT PAGE 04 IC/ �'WL GK�. s►�Ep io eE r4.16 � .�n 13b1 IikT10VED — — �� — _ _ 20m.m0' _ _ — 100.mm' � (Eb'BOTTLE�J91a � � f�OP�,�ED �-CAR -- � CsAI?AC# � `"� EL. 45� % 1' _0 � / 99. � I � � � � !EK"�4'OMC / ! � o� I �r � �" � � /, �, � r� uea . . 1 I ' ' � .� � � I , � T � . % — �EJ6`0 p I I � � � �.�,\ ., . � p � ! � -� �. . �� .� � ��` �� — --� � I � � ~ � ^ _� �~ I �� M = � ` � > .cr ��'.' � : FT — - —. --1-- -- � � �Zr — — — — _ -�_..� ._ _ , _.l_ —�— -_ ..-- -- .. � i l 11 _. .� � � . . -----7 � l� �-�- . �_� � -__ �-- � � � ��- _-�-- :o:=.__ -. .- -_ -r.�==�__ _;__� i � � � � � �� x��, T� � �� :� , � . . . � '� � � I _ _ c� a�pu�oo j I I i � \I� I -------- I � I ! / / . I � �. 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