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Home My WebLink AboutCDP 2017-0064; SLOWIK ADU; RESPONSE TO THIRD PARTY GEOTECHNICAL REVIEW; 2019-07-23EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Sharon Slowik 3960 Sunnyhill Drive Carlsbad, California 92008 10925 HARTLEY ROAD SUITE I SANTEE CALIFORNIA 92071 619 258-7901 fax 619 258-7902 Subject: Response to Third Party Geotechnical Review Proposed Second Dwelling Unit 3960 Sunnyhill Drive City of Carlsbad, California 92008 References: See Attached Dear Ms. Slowik: July 23, 2019 Project No. 03-1106H6(A) In accordance with your request, we have prepared this report to address the third party geotechnical review from Heatherington Engineering, Inc. for the proposed single-family residence at the subject site. In addition, the proposed construction has been changed since the original investigation was performed. The development will now include a basement garage near the northeast comer along with a one-story second dwelling unit. Comment No. 1 We have reviewed the grading grading plan (Reference No. 1) for the proposed second dwelling unit. The grading plan was found to be in general accordance with the recommendations provided in the referenced geotechnical reports (Reference No. 2 and No. 3). The grading recommendations provided in the referenced geotechnical report (Reference No. 3) are still valid for the proposed second dwelling unit. We anticipate that the proposed detached basement garage will be founded into dense terrace deposits, therefore, no remedial grading will be required. Continuous and spread footings are suitable for use and should extend to a minimum depth of 12 inches below the lowest adjacent grade into properly compacted fill soils or dense terrace deposits. Continuous footings should be at least 12 inches in width and reinforced with a minimum of four #4 steel bars; two bars placed near the top of the footings and the other two bars placed near the bottom of the footings. Isolated or spread footings should have a minimum width of 24 inches. Their reinforcement should consist of a minimum of #4 bars spaced 12 inches on center ( each way) and placed horizontally near the bottom. These recommendations are based on geotechnical considerations and are not intended to supersede the structural engineer requirements. SHARON SLOWIK/ 3960 SUNNYHILL DRIVE PROJECT NO. 03-1 J06H6(A) An allowable soil bearing value of 2,000 pounds per square foot may be used for the design of continuous or spread footings at least 12 inches wide and founded a minimum of 12 inches into the dense, terrace deposits as set forth in the 2016 California Building Code, Table 1806.2. This value may be increased by 400 psf for each additional foot of depth or width to a maximum value of 6,000 lb/ft2. Another one-third is allowed for wind and seismic loads. Lateral resistance to horizontal movement may be provided by the soil passive pressure and the friction of concrete to soil. An allowable passive pressure of 250 pounds per square foot per foot of depth may be used. A coefficient of friction of 0.35 is recommended. The soils passive pressure may be increased by 1/3 for wind and seismic loading. Comment No. 2 We have reviewed the grading plan prepared by Engineering Design Group of San Marcos, California for the proposed second dwelling unit and detached garage at the subject site. The grading plan was found to be in accordance with the recommendations provided in the referenced geotechnical report and update (References No. 2 and No. 3). The foundation plans and details have not been provided to date. Comments No. 3 and No. 4 Please find attached an updated geologic/ geotechnical map with a representative cross-section. Comment No. 5 Please find attached a site location map. Comment No. 6 The site consists of a remodeled single-family residence located near the center of the parcel. The site slopes moderately to the west with an existing graded pad on the eastern portion of the site. The topogarphy indicates that elevations vary from approximately 256 feet on the western property line to 284 feet at the eastern property line. Vegetation consists of typical landscaping including grass, shrub and trees. Comment No. 7 The proposed construction will include a second dwelling unit with a detached basement garage. The new structures will be one-story, wood and masonry-framed. Associated improvements will include a new driveway, retaining walls, a turf block driveway, a patio, walkways and landscaping. The grading operation for the proposed second dwelling unit should consist of the removal and recompaction of the existing loose fill soils, topsoils and colluvium located within the proposed building area. The minimum depth of removals should be at least 3 feet below the proposed finished pad grade and a minimum of 5 feet beyond perimeter footings. It is anticipated that the proposed detached basement garage will be founded entirely into dense 2 SHARON SLOWIK/ 3960 SUNNYHJLL DRIVE PROJECT NO. 03-J 106H6(A) sanstone of the terrace deposits, therefore, no remedial grading will be required. Based upon the proposed construction and the information obtained during our field investigation, we anticipate that the proposed structure will be founded on continuous and/ or spread footings, which are supported by properly compacted fill soils or dense terrace deposits. Drainage recommendations in accordance with the 2016 California Building Code have been provided in the referenced geotechnical report update (Reference No. 2). The estimated structural loads should be provided by the project structural engineer. Based upon our experience, estimated loads for one-story structures should be less than 1,500 psf. Comment No. 8 The subject site is located within the southern portion of what is known as the Peninsular Ranges Geomorphic Province of California. The geologic map pertaining to the area (Reference No. 5) indicates that the site is underlain by Pleistocene terrace deposits (Qti). Comments No. 9 and No. 10 The proposed structures should be designed using a site seismic design category D based on the 2016 California Building Code. As discussed in the geotechnical report update (Reference No. 2), a peak ground acceleration, PGAM of 0.46g was provided. Comment No. 11 Based on the dense consistency of the terrace deposits underlying the site at shallow depths, the anticipated shoring system for the basement garage excavation and the minor depth of overexcavation recommended for the second dwelling unit, it is our opinion that the proposed grading and construction will not impact adjacent properties and improvements. Comment No. 12 Based on the subgrade soil conditions, the following soil parameters may be used for the design of the temporary shoring if temporary slopes cannot be met in accordamnce with OSHA guidelines: • Active Pressure • Passive Pressure • Coefficient of Friction Comment No. 13 30 psf/ft (30 pcf EFP) 300 psf/ft (300 pcf EFP) 0.35 The following soil parameters may be used for the design of the proposed maximum 8-foot high retaining walls: 3 SHARON SLOWIK/ 3960 SUNNYHILL DRIVE PROJECT NO. 03-1 !06H6(A) Cantilevered retaining walls should be designed for an "active" lateral earth pressure of 35 psf/ft (35 pcf EFP) for level backfill conditions. Where the walls support 2: 1 (hor:vert) sloping backfill, the equivalent active fluid pressure should be increased to 45 pcf. Walls subject to uniform surcharge loads should be designed for an additional uniform lateral pressure equal to one-third (1/3) the anticipated surcharge pressure. This pressure is based on the backfill soils being free draining and non-expansive. Backfill materials must be approved by the soils engineer prior to use. Restrained walls such as basement walls should be designed utilizing an "at-rest" earth pressure of 60 psf/ft (60 pcf EFP) for approved granular and level backfill. Restrained walls subject to uniform surcharge loads should be designed for an additional uniform lateral pressure equal to one-half (1/2) the anticipated surcharge. For earthquake motions, other additional lateral pressures of 27 and 40 pcf (EFP) may be applied for non restrained and restrained conditions respectively using an inverted triangular distribution if required. Soil design criteria, such as bearing capacity, passive earth pressure and sliding resistance as recommended under the Foundation and Slab recommendations section, may be incorporated into the retaining wall design. Footings should be reinforced as recommended by the structural engineer and appropriate back drainage provided to avoid excessive hydrostatic wall pressures. As a minimum, we recommend a fabric-wrapped crushed rock and perforated pipe system. At least 2 cubic feet per linear foot of free-drainage crushed rock should be provided. Comment No. 14 Settlement of compacted fill soils is normal and should be anticipated. Because of the type and minor thickness of the fill soils anticipated under the proposed footings, total and differential settlement should be within acceptable limits. For design purpose, a differential settlement up to one-quarter inch and a total settlement up to one-half inch across the structural span may be utilized. Comment No. 15 Soluble sulfate, chloride, pH and resistivity tests were performed on a representative sample of the colluvium to evaluate its degree of corrosivity with regard to concrete and normal grade steel. The attached test results generally indicate a low degree of corrosivity. Based upon the corrosion test results, we recommend Type I/ II Portland Cement for construction with a water-cement ratio no greater than 0.55 . For standard 6 sacks of cement per cubic yard and two inches of concrete cover over steel, the estimated time to corrosion of reinforced concrete substructures is 187 years based on California Test Method 532. In addition, the minimum estimated time to perforation of a 16 gauge steel culvert is 29 years based on California Test Method 64 3. 4 SHARON SLOWIK/ 3960 SUNNYH/LL DRIVE PROJECT NO. 03-1 !06H6(A) Comment No. 16 Exterior slabs for walkways and patios should be a minimum of 4 inches in nominal thickness. For exterior slabs such as driveways or parking areas (carports), a slab thickness of at least 6 inches may be used and reinforcement sould consist of #3 bars placed at 16 inches on center each way within the middle third of the slabs by supporting the steel on chairs or concrete blocks "dobies". Placement of concrete, control/ expansion joints, and reinforcement should be m conformance with ACI specifications and the Structural Engineer's design. Comment No. 17 During site preparation for the proposed second dwelling unit and detached basement garage, East County Soil Consultation and Engineering should be notified when site grading is to begin, and a representative of our firm should observe the bottom of keyways and other recommended removals for approval prior to the placement of fill. Field density testing should then be performed so that there is at least one test in each 2-foot thick lens of compacted fill. All foundation excavations should be observed prior the placement of form boards and rebar to ensure proper depth and width in accordance with the approved plans and specifications. In addition, backfill of the proposed retaining walls should be tested and inspected as presented above. Compaction and observation reports will be issued as needed throughout the building process. If we can be of further assistance, please do not hesitate to contact our office. Respectfully submitted, Mamadou Saliou Diallo, P .E. RCE 54071 , GE 2704 MSD\md 5 ,F)</>lflif!A-m~Y i:t?,e£#oL£ VNtJ0:2J~ PU. &vf' j CaL-VJ//V#/ {¢co) ll:l(,4_A<:£ J;fft).Sll3 { t?l) EAST COUNTY SOIL CONSULTATION & ENGINEERING, INC. 10925 HARTI.EY RD .. SUITE I. SANTEE. CA 9207 1 (619) 258-7901 Fax (619) 258 -7902 I Mi" 1-1 20 2-0/'J i?3-/IObj/4G(,V : R:,f-rc /VO I ~------2.:,,_-=• ~/•;,J..!°~~-I ~ VIACLAREZ -~-; t ! ~~~~JBAL -------i • 'IIASA~W.S ~ ~ ~~?£t~..:. 7 VIA CA.ADEL 8 VIA SOiSRA (Ii,~ ~ I ~~~ .\1 \ ~\Be+ I~ \ -a(e.. '-.JiU--=-:::1. ~ ! ,~~;/ir AVi' I ' I .. ,!,; ..,I E I \ <:a : \\ t~ ~""~~ \I <11,,\ " ,.: <f.. \ \: ,"' u ¢' ~ s,,f I <!I ~ S,MYf ~ I .• I ·-~-i.. I MAC RAV r,._,.·¼ , : ~ ,. ~ c;. ~ :) """'I i fs i I.. I \ ~ ~ ~... '"' E ~. §f <1/ ~;.!'!.._GLJ.s,c,; EAV J~"#»\_, 'f~ i Cr ri i! al i; ~~:WESTPOMw~- <2. ~. -~ •• .cs \ , , ,'t-.f:. ~~#1 ~...._""-OAI! ~\~ ' ~. , '" SCltJ'l,;;\lln.. .. ~.,. .~ •r EAST COUNTY SOIL CONSULTATION & ENGINEERING, INC. I 0925 HARTLEY RD. SUITE I. SANTEE. CA 92071 (619) 258-7901 Fax (6 I 9) 258-7902 /1/G'//tl ITY MA-P 5#~0/1.J s"LO#I~ 3160 5tJl1/AIY ///LL.-J:,zy)/E C/4()L:515,;f-D LABORATORY REPORT Telephone (619) 425-1993 Fax 425-7917 Established 1928 CLARKSON LABORATORY AND SUPPLY INC. 350 Trousdale Dr. Chula Vista, Ca. 91910 www.clarksonlab.com A N A L Y T I C A L A N D C O N S U L T I N G C H E M I S T S Date: July 8, 2019 Purchase Order Number: NONE Sales Order Number: 44845 Account Number: EASCS To: *-------------------------------------------------* East County Soil Consultation and Engineering Inc. 10925 Hartley Road Suite I Santee, Ca 92071 Attention: Michael Duncan Laboratory Number: SO7400 Customers Phone: 619-258-7901 Fax: 619-258-7902 Sample Designation: *-------------------------------------------------* One soil sample received on 07/01/19 at 2:40pm, from Slowik Sunnyhill Carlsbad. Analysis By California Test 643, 1999, Department of Transportation Division of Construction, Method for Estimating the Service Life of Steel Culverts. pH 7.1 Water Added (ml) 10 5 5 5 5 5 29 years to perforation for a 16 gauge 38 years to perforation for a 14 gauge 53 years to perforation for a 12 gauge 67 years to perforation for a 10 gauge 82 years to perforation for a 8 gauge Water Soluble Sulfate Calif. Test 417 Water Soluble Chloride Calif. Test 422 Laura Torres LT/ilv metal metal metal metal metal Resistivity (ohm-cm) culvert. culvert. culvert. culvert. culvert. 5500 2700 2000 2000 2200 2300 0.005% 0.002% SHARON SLOWIK/ 3960 SUNNYHILL DRIVE PROJECT NO. 03-l 106H6(A) REFERENCES I. "Minor Grading Plan for Slowik Property" by Engineering Design Group, Dated May 2, 2019. 2. "Geotechnical Report Update, Proposed New Primary Residence, 3960 Sunnyhill Drive, City of Carlsbad, California", Project No. 03-1106H6(A), Prepared by East County Soil Consultation and Engineering, Inc., Dated August 8, 2017. 3. "Limited Site Investigation, Proposed New Primary Residence, 3960 Sunnyhill Drive, City of Carlsbad, California", Project No. 03-1106H6(A), Prepared by East County Soil Consultation and Engineering, Inc., Dated April 21, 2004. 4. "Soil Bearing Value Recommendation, Proposed Second Story Addition, 3960 Sunnyhill Drive, City of Carlsbad, California", Project No. 03-l 106H6(A), Prepared by East County Soil Consultation and Engineering, Inc., Dated July 16, 2003. 5. "Geologic Maps of the Northwestern Part of San Diego County, California", Department of Conservation, Division of Mines and Geology, by Siang S. Tan and Michael P. Kennedy, 1996. 6