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Home My WebLink AboutCDP 2017-0069; CIARMOLI RESIDENCE; SITE INSPECTION; 2018-01-30U U I I : January 30, 2018 P.O. Box 119 Lakeside, Califorrti 9204( (619) 443006( I I I Dino Ciarmoli 4205 Skyline Road Carlsbad, California 92008 SUBJECT: File No. 1106H6-17 SITE INSPECTION Proposed Residential Building Site 4205 Skyline Road City of Carlsbad Dear Mr. Ciarmoli: SCOPE R1FCEVEI MA'( 16 2019 LAND DEVELOPMENT ENGINEERING I In accordance with your request, a Site Inspection has been performed at the subject site. The purpose of this investigation was to examine existing site conditions and provide engineering recommendations for the proposed addition and 2nd story addition over the existing single I family residence and the proposed detached accessory unit. FIELD INSPECTION In order to accomplish this purpose, a representative of this firm visited the site, reviewed the topography and site conditions and visually and textually classified the surface and near surface soils. Representative samples of the on-site soils were obtained from 2 test explorations approximately 4 feet in depth and tested for density, shear strength and expansive characteristics. Existing footings, where exposed, were 16 inches in depth. SITE CONDITIONS The subject site is located on the west side of Skyline Road and south of MacArthur Avenue. The site descends at an approximate 6 to 9 degree inclination from the west to the east. The site is currently occupied by a single family split level residence with the garage level lower than the main floor. Other neighboring properties are occupied by residential structures. Fill materials were encountered to a depth of 2.5 to 3 feet during course of this inspection and native soils were loose and compressible to a depth of 12 inches. I 1 I I I fl fl I I I Dino Ciarmoli File No. 1106H6-17 January 30, 2018 SITE EROSION CONTROL I During the construction, surface water should be controlled via berms, gravel bags and/or sandbags, silt fence, straw wattles, siltation basins, while maintaining positive surface grades or other methods to avoid damage to the finish work or adjoining properties. All I site entrances and exits must have coarse gravel or steel shaker plates to minimize offsite sediment tracking. Best management Practices (BMP's) must be used to protect storm drains and minimize pollution. The contractor should take measures to prevent erosion of I graded areas until such time as permanent drainage and erosion control measures have been installed. After completion of grading, all excavated surfaces should exhibit positive I drainage and eliminate areas where water might pond. SOIL CONDITIONS I Soils encountered in the test exploration in the front of the existing house were fill soils consisting of firm to medium dense, tan brown, silty cemented sands with clay binder to approximately 2.5 to 3 in depth. These surface soils were underlain firm to medium dense, I tan, silly cemented sands with clay binder to the bottom of the exploration approximately 4 feet in depth. I The soils we encountered were not considered to be detrimentally expansive with respect to change in volume with change in moisture content. I CONCLUSIONS AND RECOMMENDATIONS 1. A representative sample of the foundation soil was remolded to 90% of maximum I dry density. Based on the following test results, a safe allowable bearing value of at least 2000 pounds per square foot for 12 inch deep footings may be used in designing the foundations and slab for the proposed structures. This value may be I increased by one third for wind and/or seismic loading. This value may be increased according to the CBC Table 1 8A-I-A by 20 percent for each additional foot of depth and or width to a maximum of 3 times the designated value. I Maximum Dry Density 123.2 pcf Optimum Moisture 9.0% I Angle of internal friction 34° Cohesion 148 psf Unit weight 110.7 pcf I Expansion Index 25 H I I I 1 Dino Ciarmoli File No. 1106H6-17 January 30, 2018 Lateral resistance to horizontal movement may be provided by the soil passive pressure and friction of concrete to soil. An allowable passive pressure of 250 I 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 I and seismic loading. The seismic parameters for the site coordinates 33.15266°N, 117.31917'W for I assumed Site Class D are as follows: USGS—Provided Output I S, = i,1iiQ S,, 1.173 g SL,= 0.782g = 0427 g S = 0.672 a SL = 0.448 For information on hovr the SS and Si values above have been calculated from probabilistic (risk-targeted) and I trnmntc ground motions in the direction of maximum horizontal repon5e, please returnto the application and select the '2DOY NEHRP building code reference document. MCE Reooic Strum fleqn Roic Spvn IH I I F' PdJ •) The existing single family residence appears to be located on a transition lot. The soils encountered along the west side of the house were native soils and fill materials were encountered in the front east side of the house to a depth of 1 to 3 feet. Footing excavations, where exposed, were 16 inches in depth. The design engineer should take into account whether the proposed second story addition is compatible for the final structurally local demand. For the proposed addition to the footprint of the existing house, to prevent differential settlement, the footings excavations should extend an additional 18 inches below approved footing depth. A suitable backfill material such as Class II base should be compacted to a minimum of 95% relative compaction or a 2 1/2 sack slurry with 3/8" aggregate mix with 8" slump may be used to back fill the bottom of the footing excavations up the approved footing depth. I I 3 I I U I I I Dino Ciarmoli File No. 1106116-17 January 30, 2018 Footings for the proposed detached accessory structure may extend through the existing loose native soils a minimum of 12 inches into firm natural ground. Anticipated foundation depth is 24 to 30 inches. Footing excavations should be inspected by a representative of this firm prior to placement of forms and reinforcing steel in order to insure that adequate depth has been achieved and that all footings are founded a minimum of 12 inches into firm natural ground. Loose soils should be removed from excavations prior to our inspection. Proposed concrete slabs areas should be prepared according to the slab recommendation below. These recommendations are based entirely upon the soil types and do not take into consideration the requirements of the proposed structure. Reinforcing in footings should consist of at least one 94 steel bar placed continuously in the top and bottom of continuous footings regardless of structural requirements. Reinforcing for isolated footings is dictated by the structural requirements. These recommendations are based upon on the soil type encountered and do not take into consideration the proposed bearing load. Footings deeper than 24 inches should have an additional #4 steel bar for each additional foot of depth. Concrete Slab-On-Grade, SOG, should be designed by the project's structural engineer based on anticipated loading conditions. We recommend that conventional reinforced concrete SOG for this project be founded on 4 inches of Class II Virgin Aggregate Base (with approximately 2% +1- over optimum moisture content and 90% compaction, relative to the lab maximum dry density, ASTM D 1557), overlying a 12 inch thick zone of adequately placed and compacted structural fill. We recommend that a moisture barrier be provided by a membrane, visqueen 10 mils in minimum thickness or equivalent, be placed at top of well compacted Class II Aggregate Base, then covered with 2 inches of moist clean sand having a minimum sand equivalent of 30 when tested in accordance with the American Society of Testing and Materials test method 'ASTM D1555. Floor slabs, as a minimum, should be 5 inches thick with #4 reinforcing steel at 16" on-center each way. Reinforcement should be placed at mid-height of the slab. The final slab thickness and reinforcement should be determined by the structural design engineer. Control joints should be provided in accordance with the recommendations of the structural design engineer. SITE AND SURFACE DRAINAGE I Drainage at the site should be directed away from foundations, collected and tight lined to appropriate discharge points. Consideration may be given to collecting roof drainage by eave gutters and directing it away from foundations via non-erosive devices. Water, either I I 4 I I I Li I 'I I I I I I Li I I I Dino Ciarmoli File No. 1106H6-17 January 30, 2018 natural or from irrigation, should not be permitted to pond, saturate the surface soils or flow towards the foundation. Landscaping requiring a heavy irrigation schedule should not be planted adjacent to foundations or paved areas. The type of drainage issues found within the project and materials specified and used should be determined by the Engineer of Record. GROUNDWATER AND SURFACE WATERS I There was no indication of a near-surface groundwater table within our exploratory trench or perched groundwater. Although groundwater is not expected to be a significant constraint to the proposed development, our experience indicates that near-surface I groundwater conditions can develop in areas where no such groundwater conditions previously existed, especially in areas where a substantial increase in surface water infiltration results from landscape irrigation or unusually heavy precipitation. It is I anticipated that site development will include appropriate drainage provisions for control and discharge of surface water runoff. The type of drainage issues found within the project and materials specified and used should be determined by the Civil Engineer. The type of I plants and soil specified along with proper irrigation used should be determined by the Landscape Architect. I The following grading specifications should be utilized if grading is proposed. RECOMMENDED GRADING SPECIFICATIONS I For Proposed Residential Building Site 4205 Skyline Drive I City of Carlsbad GENERAL: Soil Testers and 'Engineer' are synonymous hereinafter and shall be employed I to inspect and test earthwork in accordance with these specifications, the accepted plans, and the requirements of any jurisdictive governmental agencies. They are to be allowed adequate access so that the inspections and tests may be performed. The Engineer shall be apprised of I schedules and any unforeseen soil conditions. Substandard conditions or workmanship, inadequate compaction, adverse weather, or I deviation from the lines and grades shown on the plans, etc., shall be cause for the engineer to either stop construction until the conditions are corrected or recommend rejection of the work. Refusal to comply with these specifications or the recommendations and/or I interpretations of the engineer will be cause for the engineer and/or his representative to immediately terminate his services. Deviations from the recommendations of the Soil Report, from the plans, or from these I I 5 I n I Dino Ciarmoli File No. 1106H6-17 January 30, 2018 I Specifications must be approved in writing by the owner and the contractor and endorsed by the engineer. SOIL TEST METHODS: Maximum Density & Opt Moisture Density of Soil In-Place Soil Expansion Shear Strength Gradation & Grain Size Capillary Moisture Tension Organic Content -- ASTM D1557-70 -- ASTM D1556, D2922 and D3017 -- UBC STANDARD 29-2 -- ASTM D3080-72 I [I F I -- ASTM D114O-71 -- ASTM D2325-68 -- % Weight loss after heating for 24 hours at 300° F and after deducting soil moisture. LIMITING SOIL CONDITIONS: I Minimum Compaction 90% for 'disturbed' soils. (Existing fill, newly placed fill, plowed ground, etc.) 84% for natural, undisturbed soils. 95% for pavement subgrade within 2' of I finish grade and pavement base course. Expansive Soils Expansion index exceeding 20 Insufficient fines Less than 40% passing the #4 sieve. I Oversized Particles Rocks over 10" in diameter. I PREPARATION OF AREAS TO RECEIVE FILL: Brush, trash, debris and detrimental soils shall be cleared from the areas to receive fill. Detrimental soils shall be removed to firm competent soil. Slopes exceeding 20% should be I stepped uphill with benches 10' or greater in width. Scarify area to receive fill to 6" depth and compact. I FILL MATERIAL shall not contain insufficient fines, oversized particles, or excessive organics. On-site disposition of oversized rock or expansive soils is to be at the written direction of the Engineer. Select fill shall be as specified by the engineer. All fills shall be I compacted and tested. SUBDRAINS shall be installed if required by and as directed by and detailed by the I engineer and shall be left operable and unobstructed. They shall consist of 3" plastic perforated pipe set in a minimum cover of 4" of filter rock in a 'vee' ditch to intercept and drain free ground from the mass fills. Perforated pipe shall be schedule 40, I Poly-Vinyl-Chloride or Acrylonitrile Butadienne Styrene plastic. Rock filter material shall conform to the following gradation: I I [.1 I Li I Dino Ciarmoli File No. 1106H6-17 January 30, 2018 Sieve size: 3/4" #4 #30 #200 I %Passing: 90-100 25-50 5-20 0-7 Subdrains shall be set at a minimum gradient of 0.2% to drain by gravity and shall be tested I by dye flushing before acceptance. Drains found inoperable shall be excavated and replaced. CAPPING EXPANSIVE SOILS: If capping expansive soils with non-expansive soil to mitigate the expansive potential is used, the cap should be compacted, non-expansive, select I soil placed for a minimum thickness 3' over the expansive soil and for a minimum distance of 8' beyond the exterior perimeter of the structure. Special precautions should be taken to ensure that the non-expansive soil remains uncontaminated and the minimum thickness and I dimensions around the structure are maintained. The expansive soils underlying the cap of non-expansive cap should be pre-saturated to a depth of 3' to obtain a degree saturation I exceeding 90% before any construction supported by the compacted cap. The non-expansive soil comprising the cap should conform to the following: I Minimum Compaction 90% Maximum Expansion Index 30 Minimum Angle of Internal Friction 33 Deg I Cohesion Intercept 100 psf UNFORESEEN CONDITIONS: Soil Testers assume no responsibility for conditions, I which differ from those, described in the applicable current reports and documents for this property. Upon termination of the engineer's services for any reason, his fees up to the time of termination become due and payable. If it is necessary for the engineer to issue an I unfavorable report concerning the work that he has been hired to test and inspect, the engineer shall not be held liable for any damages that might result from his 'unfavorable report'. I If we can be of any further assistance, please do not hesitate to contact our office. This opportunity to be of service is sincerely appreciated. I Respectfully submitted, ESS/ Chin C. Chen, RPE C34442 0 No. C 034442 C10- I 7 I