Loading...
HomeMy WebLinkAboutCUP 260D; PALOMAR TRANSFER STATION; RESPONSE TO THIRD PARTY GEOTECHNICAL REVIEW PALOMAR TRANSFER STATION PROJECT, DATED SEPTEMBER 27, 2019; 2019-11-14Converse Consultants Geotechnical Engineering, Environmental & Groundwater Science, Inspection & Testing Services November 14, 2019 Mr. DJ Dean Principal Architect KPG 3131 Elliott Avenue, Suite 400 Seattle, Washington 98121 RECORD COPY t>meja1l lnitrnl RECE VED LAND DEVELOPMENT ENGINEERING Subject: RESPONSE TO THIRD PARTY GEOTECHNICAL REVIEW, PALOMAR TRANSFER STATION PROJECT, DATED SEPTEMBER 27, 2019 Orion Street and Faraday Avenue Carlsbad, California Converse Project No. 06-32-110-05 References: Converse Consultants, Geotechnical Investigation Report, Improvements to Palomar Station, Orion Street and Faraday Avenue, Carlsbad, California, dated April 5, 2006, Converse Project No. 06-32-110-01. Third-Party Geotechnical Review (Second) -Palomar Station, Orion Street and Faraday Avenue; Carlsbad, California, by Hetherington Engineering, Inc., dated June 10, 2019. Third-Party Geotechnical Review (Second) -Palomar Station, Orion Street and Faraday Avenue, Carlsbad, California, by Hetherington Engineering, Inc., dated September 27, 2019. Dear Mr. Dean: Converse Consultants (Converse) has prepared this report to respond to third-party geotechnical review comments prepared by Hetherington Engineering, Inc. dated September 27, 2019 for the Palomar Transfer Station Project located on Orion Street and Faraday Avenue in Carlsbad, California. Third-party review comments prepared by Hetherington Engineering, Inc. dated September 27, 2019 for the Palomar Transfer Station Project are followed by our responses and are presented as follows: REVIEW COMMENTS AND RESPONSES Comment No. 1: The consultant should provide a detailed description of proposed site grading, structures/improvements, foundations type, etc. (Third request) Converse response: Acknowledged. A detailed description of proposed site grading, structures/improvements, foundations type are provided in Appendix A. 717 South Myrtle Avenue, Monrovia, Californi a 91016 Telephone: (626) 930-1200 • Facsimile: (626) 930-1212 • www converseconsultants.com CUP 260 (D) Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 Comment No. 2: The Consultant should provide a statement that the recommended foundation and slab design criteria for expansive soils are consistent with Section 1806.6 of the 2016 California Building Code or revise the foundation and slab design criteria accordingly. Converse response: Acknowledged. The recommended foundation and slab design criteria for expansive soils are consistent with Section 1806.6 of the 2016 California Building Code. Comment No. 3: The Consultant should provide hardscape recommendations (thickness, reinforcement, joints, etc.). (Third Request) Converse response: There is no hardscape in the project. Sincerely, CONVERSE CONSULTANTS ,✓ .-sls;v--;;-;~<J~-- Siva K. Sivathasan, PhD, PE, GE, DGE, QSD, F. ASCE Senior Vice President/ Principal Engineer Dist: 1/ Addressee via Email 3/ Addressee via USPS Mail Attached: Appendix A: Proposed Site Grading, Structures/Improvements, Foundations Type Appendix B: Third-Party Geotechnical Review (Second) (i) Copyright 2019 Converse Consultants 2 Appendix A Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 1.0 EARTHWORK/SITE GRADING RECOMMENDATIONS 1.1 General This section contains our general recommendations regarding earthwork and site grading for the proposed development. These recommendations are based on our experience with similar projects in the area and the results of our field exploration, laboratory testing, and data evaluation as presented in the preceding sections. Prior to the start of grading, utilities should be located in the field and either re-routed or protected. All debris, concrete foundations, surface vegetation, deleterious material, and surficial soils containing roots and perishable materials should initially be stripped and removed from the site. Any unsuitable materials uncovered by the stripping operation should be excavated to expose undisturbed bedrock. The excavations should not cause loss of bearing and/or lateral supports of the existing structures or utilities. 1.2 Subgrade Preparation The final bottom surfaces of all excavations should be observed and approved by the project geotechnical consultant prior to placing any fill and/or structures. Any over-excavations for the building should be observed by a Converse representative. Based on observations, removal of localized areas deeper than those documented may be required during grading. Therefore, some variations in the depth and lateral extent of over-excavation recommended in this report may be anticipated. Subgrade soil surfaces that will receive compacted fill shall be scarified to a depth of at least 12 inches and the scarified on site soils shall be moisture-conditioned to 120 percent of optimum moisture content and compacted to a minimum relative compaction of 90 percent. The fill materials placed on scarified and compacted soils should be compacted to 90 percent relative compaction. 1.3 Over-excavation/Removal for Addition to Existing Transfer Station Building and New Scale Building Based on our field investigation, the upper five (5) feet of the site soils encountered in our exploratory boring are undocumented fill soils in the vicinity of the building addition and the new scale building are not suitable to support the structure. Based on laboratory test results and exploration, the upper site soils have low expansion potential (El=40). The top two (2) feet of on-site soils are not suitable to support the slab-on-grade for these proposed buildings. These materials should be removed and replaced with compacted fill. The clayey fill soils should be brought to at least 120 percent of the optimum moisture and compacted to at least 90 percent relative compaction as per ASTM Standard D1557 test method. The depth of anticipated over-excavation is about 2 feet. Relative compaction is defined as the ratio of the in-place soil dry density to the laboratory maximum dry density as determined by the ASTM Standard D1557 test method. Conventional isolated spread footings for the addition to existing Transfer Building foundered all in compacted fill or bedrock may be used to support the building. The entire undocumented fill soils shall be removed and replaced as compacted fill, if the footings to be supported on properly ~ Copyright 2019 Converse Consultants A-1 Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 compacted fill. The footings for the addition to the existing building shall be setback from the descending slope to a distance equal to one third of the height of the slope. Conventional footings for the new Scale Building foundered all in compacted fill may be used to support the building and all the undocumented fill soils shall be removed and replaced as compacted fill. The anticipated depth of removal is about five (5) feet and the removal should extend at least five (5) feet laterally or to the extent possible. The subgrade soils need to be scarified at least 12 inches and recompacted according to the Section 8.2, Subgrade Preparation. 1.4 Over-excavation/Removal for New Truck Scale Based on our exploration, and the information given to our office, the site for the proposed new Truck Scale consists of minimum five (5) feet of fill. Over excavations need to be observed to verify the excavation bottomed to competent bedrock. The proposed Truck Scale may be supported on mat foundation founded on bedrock or at least two (2) feet of compacted fill. The subgrade soils need to be scarified at least 12 inches and recompacted according to the Section 1.2, Subgrade Preparation. 1.5 Over-excavation/Removal for Concrete Flat Work and Paving Areas As a minimum, 18 inches of compacted fill should be provided for any concrete flatwork, curbs and gutters and asphalt concrete paving areas. Such over-excavation should extend at least two (2) feet beyond the edges of concrete flatwork or to the extent possible. 1.6 Expansive Soil Mitigation The site soils have low expansion potential. There are several mitigation measures that can be utilized to improve expansive soils at the site. Some mitigation measures include: • Remove and replace with two (2) feet of non-expansive soils • Thicker concrete slabs with moisture barrier and grade beams • Post-tensioned slabs with moisture barrier It is very important to keep the site soils moisture content around or under the edge of foundation, concrete slab, and asphalt concrete pavement at approximately the same moisture content before, during and after construction. This will reduce greatly the expansion potential of the site soils. The site soils have low expansion potential. Slabs, foundations and pavement placed directly on expansive subgrade soil will likely crack over time. The impact of the expansive soil can be reduced by (a) removing about two (2) feet of the underlying soils below slabs and footings throughout the site, except landscape areas, and replacing with imported sandy material (Expansion Index less than 20), (b) deepen and reinforce footing and place thicker concrete slab with grade beam and moisture barrier, ( c) use post-tensioned slab, and ( d) lime treat the upper two (2) feet of the subgrade soils. E!) Copyright 2019 Converse Consultants A-2 1. 7 Structural Backfill Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 All structural fill should be placed on competent, scarified and compacted materials as determined by a geotechnical consultant representative, and in accordance with the specifications presented in this section. Rocks larger than three (3) inches in the largest dimension should not be placed as fill. Rocks larger than one (1) inch should not be placed within the upper 12 inches of subgrade soils. Excavated site soils, free of deleterious materials and cobbles/boulders larger than six (6) inches in the largest dimension should be suitable for placement as compacted fill. Any import fill should be tested and approved by Converse prior to delivery to the site. The import fill should be free of organic matter and other deleterious material, non-expansive, with an expansion index less than 20. 1. 7. 1 Compaction This section contains our recommendations for compaction of fill placed in accordance with the specifications provided in Appendix C, Earthwork Specifications and in Section 8.2, Subgrade Preparation. • All clayey fill, if not noted otherwise, should be compacted to a relative compaction of at least 90 percent as per ASTM Standard D1557 test method at moisture content at least 120 percent of optimum. Relative compaction is defined as the ratio of the in-place soil dry density to the laboratory maximum dry density as determined by the ASTM Standard D1557 test method. • All sandy fill, if not noted otherwise, should be compacted to a relative compaction of at least 90 percent and moisture content about 2 percent within the optimum moisture. • All bases and subbase, if any, for pavement structures should be compacted to relative compaction of at least 95 .percent as per ASTM Standard D1557 test method. The project geotechnical consultant will observe the placement of compacted fill and conduct in- place field density tests on the compacted fill to check for adequate moisture content and relative compaction as required by the project specifications. Where less than the required relative compaction is indicated, additional compactive efforts shall be applied and the soil moisture- conditioned as necessary, until the required relative compaction is attained. The contractor shall provide level testing pads upon which the soils engineer may conduct field density tests. The contractor shall provide safe and timely access for the geotechnical testing personnel throughout the grading operation to allow continuous monitoring and testing. 1. 7 .2 Shrinkage The shrinkage would depend on, among other factors, the depth of cut and/or fill, and the grading method and equipment utilized. The average shrinkage factor for the near surface on site soils may be estimated to range from ten (10) to twenty (20) percent. Although these values are only approximate, they represent our best estimates of the factors to be used to calculate lost volume that may occur during grading. If more accurate shrinkage and subsidence factors are needed, it is recommended that field-testing using the actual equipment and grading techniques be conducted. ~ Copyright 2019 Converse Consultants A-3 1.8 Site Drainage Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 Adequate positive drainage should be provided away from building pad areas to prevent ponding and to reduce percolation of water into the foundation soils. Building pads should have a drainage gradient of at least two (2) percent towards drainage devices. Planters and landscaped areas adjacent to the building pad perimeter should be designed and irrigated to minimize water infiltration into the subgrade soils. Adequate drainage should also be provided for any cut/fill slopes, landscaped and paved areas. A desirable drainage gradient is one (1) percent for paved areas and two (2) percent in landscaped areas. 1.9 Paving All areas to be paved should be graded in accordance with the general recommendations for site grading presented under the Section 1.0, Earthwork/Site Grading Recommendation. If the proposed pavement subgrade areas have become disturbed or desiccated after the site grading and prior to placing the base course, the subgrade may have to be re-scarified to a depth of at least 12 inches, be moisture conditioned as required to obtain optimum moisture conditions, and be recompacted to at least 90 percent of the maximum dry density. This decision will be made at the time of construction by our field representative. One R-value test was performed on a bulk sample of the on-site surface soils from boring BH-9. The results of this test indicate an R-value of 11 . Based on this R-value and the selected traffic index values indicated below, the following minimum flexible pavement sections were computed for budget purposes. Our computations were based on the Ca/trans Highway Design Manual, fourth edition: PAVEMENT COMPONENT THICKNESS (Inches) Tl= 5.5 Tl= 6.5 Tl= 7.5 Tl= 8.5 Tl= 9.5 Asphalt Concrete (AC) 3.0 4.0 4.5 5.0 6.0 Aggregate Base (AB) 11 .0 12.5 15.0 18.0 20.0 Total Pavement Thickness 14.0 16.5 19.5 23.0 26.0 The actual R-value will depend on the compacted fill at the subgrade level. We recommend that R-value tests be performed during grading to confirm design pavement section indicated above. Additional pavement sections can be presented upon request for imported fill subbase or for different traffic index values. Selection of the traffic indices should be made by your civil engineer based on his knowledge of traffic flow and loading. The base course should be crushed aggregate base or processed natural material conforming to Section 200-2.2 or 200-2.4, Standard Specifications for Public Works Construction (Green Book latest). The aggregate base and asphalt concrete should be compacted to at least 95 percent of the maximum dry density in accordance with ASTM 01557-00. 1.10 Utilities The on-site soils are suitable for backfill of utility trenches from one foot above the top of the pipe to the finished grade, provided the material is free of organic matter and deleterious substances. {!) Copyright 2019 Converse Consultants A-4 Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 It is anticipated that the compacted fill will provide a firm foundation for site utilities. Any soft and/or unstable material encountered at the pipe invert should be removed and replaced with an adequate bedding material. The on-site soils are not considered suitable for bedding or shading of utilities. Therefore, we recommend that non-expansive granular soils with a Sand Equivalent (SE) greater than 30 as determined by ASTM Test Method D2419 be imported for that purpose. Trench backfill soils should be compacted to at least 90 percent of the maximum dry density as determined by ASTM Test Method D1557. @) Copyright 2019 Converse Consultants A-5 Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-11 0-05 November 14, 2019 2.0 DESIGN AND CONSTRUCTION RECOMMENDATIONS 2.1 General Evaluation Based on our field exploration, laboratory testing and analyses of subsurface conditions at the site, remedial grading is required to prepare the site for support of the various structures. Shallow footings such as conventional isolated spread footings for the proposed Transfer Station addition and Truck Scale Building founded on bedrock or compacted fills shall be setback from the descending slope to a distance equal to one third of the height of the slope. If the drilled cast- in-place piles are used to support the building, then the upper five (5) feet of soils should not be considered for the vertical and the lateral capacities. The new Truck Scale may be supported on mat foundation founded all on undisturbed bedrock or at least two (2) feet of properly compacted fill below the bottom of foundations. The compacted fill should extend at least five (5) feet laterally or to the maximum extent possible. The various design recommendations provided in this section are based on the assumption that in preparing the site, the above earthwork and grading recommendations will be implemented. 2.2 Spread Footing Design Parameters Spread footings for the Transfer Station addition, founded on bedrock or properly compacted fill may be designed based on an allowable net bearing capacity of 4,000 pounds per square foot (psf). All undocumented fill soils at the new Scale Building and the new Truck Scale area should be removed and replaced as compacted fill. Subgrade soil surfaces that will receive compacted fill shall be s'carified to a depth of at least 12 inches and the scarified on site soils shall be moisture- conditioned to 120 percent of optimum moisture content and compacted to a minimum relative compaction of 90 percent. The fill materials placed on scarified and compacted soils should be compacted to 90 percent relative compaction. Footings founded on compacted fill, and placed at a depth 24 inches below lowest adjacent grade with at least 18 inches wide, may be designed based on an allowable net bearing capacity of 2,500 psf. The allowable bearing capacity may be increased by 500 psf for each foot of additional embedment depth and 250 psf for each foot of additional width, but should not exceed 4,000 psf. The footing reinforcement should be based on structural design. The allowable net bearing capacity is defined as the maximum allowable net bearing pressure on the ground. It is obtained by dividing the net ultimate bearing capacity by a safety factor. The ultimate bearing capacity is the bearing stress at which ground fails by shear or experiences a limiting amount of settlement at the foundation. The net ultimate bearing capacity is obtained by subtracting the total overburden pressure on a horizontal plane at the foundation level from the ultimate bearing capacity. The net allowable bearing values indicated above are for the dead loads and frequently applied live loads and are obtained by applying a factor of safety of 3.0 to the net ultimate bearing capacity. If normal code requirements are applied for design, the above vertical bearing value may be increased by 33 percent for short duration loadings, which will include loadings induced by wind or seismic forces. The maximum anticipated settlement of a square footing founded on (tl Copyright 2019 Converse Consultants A-6 Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 compacted fill is estimated to be less than ½-inch for a five (5) foot square footing and the differential settlements are expected to be on the order of ¼-inch between adjacent footings. 2.3 Drilled Cast in Place Piles Drilled cast in place piles are another alternative foundation system and the piles deriving their capacities primarily from the bedrock about five (5) feet below the existing grade. We recommend that the grade beam, footings, and slab be supported on the piles if piling is the selected alternate. The allowable design allowable skin friction of 300 psf driving from the bedrock may be used for the design. The capacity was computed by using a safety factor of two (2) for skin friction. The settlement of a single pile is expected to be about one-fourth (¼) inch. The vertical capacities above may be increased by 33 percent to resist transient downward vertical loads, such as wind forces or seismic shaking. Pile uplift design capacities may be taken as 50 percent of the vertical downward pile design values shown. The drill cast in place pile should have a minimum diameter of 14 inches and the spacing between piles should not be less than three (3) times the pile diameter. Allowable axial loads of pile groups with center-to-center pile spacing of less than three (3) pile diameters should be determined by incorporating an efficiency reduction factor to the allowable axial loads for single piles. Based on the subsurface conditions, the piers can be drilled without casing. However, if caving or an unstable hole is encountered, a temporary casing may be required. Drilled pile excavations should be filled with concrete on the same day they are drilled. The drilling for piles should not be performed adjacent to recently excavated or recently poured piles until the concrete in the completed piles has been allowed to set for several hours. In addition, the piles should also be poured in a manner that will not result in concrete flowing into adjacent open pile excavations. Piles in groups should be drilled and poured in an alternating sequence to minimize the potential for fresh concrete flowing into adjacent open pile excavations. The placement of reinforcement and concreting operations should conform to ACI and other applicable code requirements. Concrete placement should be continuous from the bottom to the top of the drilled pile. Concrete placement should continue after the borehole is filled until good quality concrete is evident at the top of the shaft. Concrete should be placed through a tremie or pump system and the discharge end of the tremie/orifice should be immersed at least 5 feet in concrete at all times after the start of the concrete flow. In addition, the level of concrete in the tremie should be maintained above the level of slurry in the borehole at all times to prevent slurry intrusion into the shaft concrete. We recommend that the installation of the drilled piles be performed with the observation of Converse Consultants. 2.4 Mat Foundation A mat foundation may be used to support the proposed new Truck Scale. An allowable net bearing capacity of 3,000 pounds per square foot (psf) may be used to support the Truck Scale on competent bedrock or at least two feet of compacted fill. A total settlement within ½-inch with a differential settlement of ¼-iinch is anticipated for a mat foundation placed on competent bedrock or on two feet of properly compacted fill. A modulus of €!} Copyright 2019 Converse Consultants A-7 Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 subgrade reaction of 175 pounds per square inch per inch can be used for design of the mat foundation for the tank and booster pump station. This value is based on a unit square foot area and must be adjusted to mats of various widths. The following equation may be used to calculate k for use in mat foundation design: k= 175[(8+1 )/28] 2 k= Modulus of subgrade reaction, pounds per square inch per inch 8= Mat foundation width, feet 2.5 Resistance to Lateral Loads Resistance to lateral loads can be assumed to be provided by friction acting at the base of foundations and by passive earth pressure. A coefficient of friction of 0.35 between concrete and soil may be used with the dead load forces. An allowable passive earth pressure of 300 psf per foot of depth may be used for the sides of footings poured against recompacted soils. A factor of safety of 1.5 was applied in calculating passive earth pressure. The maximum value of the passive earth pressure should be limited to 2,500 psf. Vertical and lateral bearing values indicated above are for the total dead loads and frequently applied live loads. If normal code requirements are applied for design, the above vertical bearing and lateral resistance values may be increased by 33 percent for short duration loading, which will include the effect of wind or seismic forces. Due to the low overburden stress of the soil at shallow depth, the upper one foot of passive resistance should be neglected unless the soil is confined by pavement or slab. 2.6 Slabs-on-Grade Structural design elements such as thickness, reinforcement, joint spacing, etc., for the slab-on- grade should be selected based on the analysis performed by the project structural engineer considering anticipated loading conditions and the modulus of subgrade reaction of the supporting materials. The site soils will be substantially mixed during site grading and the Expansion Index (El) values of the final subgrade soils are likely to be different. At the completion of grading, the expansion index of the subgrade soils should be determined and recommendations should be re-evaluated. For upper the two (2) feet of subgrade soils replaced with compacted imported soils: Slab-on- grade should have a minimum thickness of four ( 4) inches for support of nominal ground-floor live loads. Minimum reinforcement for slab-on-grade will be No. 4 reinforcing bars, spaced at 16 inches on-center each way. The thickness and reinforcement of more heavily loaded slabs will be dependent upon the anticipated loads and shall be designed by a structural engineer. A static modulus of subgrade reaction equal to 200 pounds per square inch (psi) may be used in structural design of concrete slab-on-grade. For upper the two (2) feet of subgrade soils, replaced with compacted on-site soils: Slab-on- grade should have a minimum thickness of six (6) inches for support of nominal ground-floor live loads. Minimum reinforcement for slab-on-grade will be No. 4 reinforcing bars, spaced at 16 inches on-center each way. The thickness and reinforcement of more heavily loaded slabs will {!) Copyright 2019 Converse Consultants A-8 Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 be dependent upon the anticipated loads and shall be designed by a structural engineer. A static modulus of subgrade reaction equal to 150 psi may be used in structural design of concrete slab- on-grade. Our recommended parameters for the design of post-tension slab-on-grade are based on the CBC, 2016 Edition, Section 1816, listed below: • Edge Moisture Variation Distance (Em, Center Lift): 6 feet • Edge Moisture Variation Distance (Em, Edge Lift): 3 feet • Estimated Differential Swell (Ym, Center Lift): 0.9 to 1.3 inches • Estimated Differential Swell (Ym, Edge Lift): 0.18 to 0.32 inches Actual design method for post-tensioned slab-on-grade should be selected by the project structural engineer. All slab-on-grade should be underlain by a ten-mil Visqueen (or equivalent) moisture barrier. The moisture barrier should be covered by approximately two (2) inches of sand to minimize punctures and to aid in concrete curing. Subgrade soils must be firm and nonyielding prior to placement of concrete. In hot weather, the contractor should take appropriate curing precautions after placement of concrete to minimize cracking of the slabs. The potential for slab cracking may be lessened by the addition of fiber mesh to the concrete and/or control of water/cement ratio. Joints for concrete slabs-on-grade must be carefully designed. Joint spacing is dependent upon slab thickness and concrete properties and should be selected by the structural engineer. Concrete should be cured by protecting it against loss of moisture and rapid temperature change for at least seven days after placement. Moist curing, waterproof paper, white polyethylene sheeting, white liquid membrane compound, or a combination thereof, may be used after finishing operations have been completed. The edges of concrete slabs exposed after removal of forms should be immediately protected to provide continuous curing. After the subgrade soils have been compacted to at least 90 percent of compaction and moisture- conditioned to at least 120 percent above optimum moisture, at least 24 inches of the subgrade soil below the bottom of the footings shall be presoaked to 20 percent above optimum moisture content prior to concrete pour. For example, the optimum moisture content of the subgrade soil is 8.0 percent, presoaking to 20 percent above optimum moisture content will bring the moisture content to 9.6 percent (20 percent increase). This moisture content should be maintained at the time of concrete pour. The above recommendations are based on the results of tests performed on representative site soils. If soils other than those presently encountered within the project site are placed as structural fill within the building pads, the modulus of subgrade reaction should be reevaluated. The final slab design should be based on this value of the modulus of subgrade reaction. ~ Copyright 2019 Converse Consultants A-9 2.7 Temporary Sloped Excavations Palomar Transfer Station Project Responses to Third-Party Review Comments Converse Project No. 06-32-110-05 November 14, 2019 The following recommendations are provided for use by the engineer during the design of the project to determine shoring requirements and estimate construction costs. Based on the materials encountered in the exploratory borings temporary excavations may be supported by shoring or constructed according to the slope ratios presented in the table below. Temporary cuts encountering loose fill or loose dry sand, excavated near existing structures may require shoring or have to be constructed at a flatter gradient than presented in the following table. -• --,, -•r l' • • -~ -pc-~*,-. . . . .. :-. . ~ 0-4 Vertical 4-10 1:1 'Slope ratio assumed to be uniform from top to toe of slope. For steeper temporary construction slopes or deeper excavations, shoring should be provided by the contractor as necessary, to protect the workers in the excavation. Surfaces exposed in slope excavations should be kept moist but not saturated to retard raveling and sloughing during construction. Adequate provisions should be made to protect the slopes from erosion during periods of rainfall. Surcharge loads, including construction materials, should not be placed within five (5) feet of the unsupported slope edge. Stockpiled soils with a height larger than six (6) feet will require greater distance from trench edges. If the excavation occurs near existing structures, special construction considerations would be required during excavation to protect these existing structures during construction. The proposed excavation should not cause loss of bearing and/or lateral supports of the existing structures. Due to close proximity of the existing building, the sloped over-excavation for the transfer station addition building may not be feasible. The excavation may consist of vertical cut exceeding five (5) feet or more should be adequately supported by temporary shoring to protect existing adjacent structures. Recommendations of shoring will be provided upon requested. @ Copyright 2019 Converse Consultants A-10 Appendix B ETHERING O ENG EERI G, IN . SOIL & FOUNDATION ENGINEERING• ENGINEERING GEOLOGY• HYDROGEOLOGY City of Carlsbad Land Development Engineering 1635 Faraday A venue Carlsbad, California 92008-7314 Attention: Mr. David Rick September 27, 2019 Project No. 8770. l Log No. 20675 P1. 211J~-_op,J/~JJ l,sjvJIY'<-J ;-"( -D. tJ..,c k Subject: THIRD-PARTY GEOTECHNICAL REVIEW (THlRD) Palomar Transfer Station Orion Street and Faraday A venue Carlsbad, California Project ID: GR2018-0049 (CUP260D) References: Attached Dear Mr. Rick: In accordance with yom request, Hetherington Engineering, Inc. has provided third-party geotechnical review of References 9 and 10. The following conuuents are provided for analyses and/or response by the Geotechn.ical Consultant. 1. The Consultant should provide a detailed description of proposed site grading, structures/improvements, foundation type, etc. (Third Request). 2. The Consultant should provide a statement that the recommended foundation and slab design criteria for expansive soils are consistent with Section 1808.6 of the 2016 California Building Code or revise the foundation and slab design criteria accordingly. 3. The Consultant should provide hardscape reconunendations (thiclmess, reinforcement, joints, etc.). (Third Request) 5365 Avenida Encinas, Suite A• Carlsbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545 333 Third Street, Suite 2 • Laguna Beacl1, CA 92651-2306 • (949) 715-5440 • Fax (760) 931-0545 www.hetheringtonengineering.com THIRD-PARTY GEOTECHN1CAL REVIEW (THIRD) Project No. 8770.1 Log No. 20675 September 27, 2019 Page 2 Please call ifthere are any questions. Sincerely, HETHERINGTON ENGINEERING, INC ) // Paul A. Bogseth Professional Geologist 3772 Certified Engineering Ge Certified Hydrogeologis ( expires 3/31 /20) ,,.,,,-~ -·· . .,. /I .... ., I M~(i·ft D~i'(~;:<i;(g10/ ~ / Civil Engineer 30488 Geotechnical Engineer 397 (expires 3/31/20) Distribution: 1-via e-mail David Rick (David.rick@cadsbadca.gov) 1-via e-mail Scott Carl wright (Scartwrighl@mbakerintl.com) I-via e-mail Miguel Avalos (Miguel.Avalos@mbakerintl.com) HETHERINGTON ENGINEERING, INC. REFERENCES 1. "Geotechnical Investigation Rep01t, Improvements to Palomar Transfer Station, Orion Street and Faraday Avenue, Carlsbad, California", by Converse Consultants, dated April 5, 2006. 2. "Updated Seismic Design Parameters Based on 2016 CBC for "Geotech.nical Investigation Report, Improvements to the Palomar Transfer Station", by Converse Consultants dated April 5, 2006, Palomar Transfer Station Expansion Project, Orion Street and Faraday Avenue, Carlsbad, California", by Converse Consultants, dated September 19, 2018. 3. "Transfer Station Addition for Palomar Transfer Station, 5960 El Camino Real, Carlsbad, California", by XA Architecture Company, (Sheets G0.0, S1.0, S1.1, S1.2, S2.0), print dated December 7, 2018. 4. "Grading Plans for: Palomar Transfer Station, 5960 El Camino Real, Carlsbad, California", by David Evans and Associates, Inc., print dated December 5, 2018 (Sheets Cl.0, Cl.I, C2.l, C3.l, C4.1, C4.2, CS.I, C5,2). 5. "Third-Party Geotechnical Review (First), Palomar Transfer Station, Orion Street and Faraday Avenue, Carlsbad, Califomia, Project ID: GR2018-0049 (CUP260D)", by Hetherington Engineering, Inc., dated December 27, 2018. 6. "Updated Retaining Wall Design Parameters, 2016 California Building Code (CBC), Palomar Transfer Station Expansion Project, O1i.on Street and Faraday A venue, Carlsbad, California", by Converse Consultants, dated October 16, 2018. 7. Response Letter by KPG; dated April 25, 2019 (2-pages). 8. "Third-Party Geotechnical Review (Second), Palomar Transfer Station, Orion Street and Faraday Avenue, Carlsbad, California, Project ID: GR1018-0049 (CUP260D)", by Hetherington Engineering, Inc., dated June 10, 2019. 9. "Response to Third-Patty Geotechnical Review, Palomar Transfer Station Project, dated June 10, 2019, Orion Street and Faraday Avenue, Carlsbad, California, Converse Project No. 06-32-100-05", by Converse Consultants, dated August 26, 2019. 10, "Plan Review, Proposed Palomar Transfer Station Project, Orion Street and Faraday Avenue, Carlsbad, California, Converse Project No. 06-32-100-05", by Converse Consultants, dated August 26, 2019. 11. "Grading Plans For: Palomar Transfer Station", by David Evans and Associates, received September 16, 2019 (Sheets 1 through 11 ), HETHERINGTON ENGINEERING, INC. Project No. 8770. I Log No. 20675 REFERENCES 12. "Palomar Transfer Station Addition, 5960 El Camino Real, Carlsbad, CA 92008, Earthwork Exhibit", by David Evans and Associates, Inc., dated September 5, 2019 (Sheet EX). 13. "Palomar Transfer Station Addition, 5960 El Camino Real, Cal'lsbad, CA 92008, First Access Plan", by David Evans and Associates, Inc., dated September 5, 2019 (Sheet C-FA). HETHERINGTON ENGINEERING, INC. Project No. 8770.1 Log No. 20675