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HomeMy WebLinkAboutRP 15-16; 4 + 1 LUXURY LIVING; SITE INSPECTION PROPOSED COMMERCIAL BUILDING SITE 3050 MADISON STREET CITY OF CARLSBAD; 2016-07-07July 7, 2016 Dr. Bruce Sabba First BMS Properties, LLC 1010 Pearl Street #12 La Jolla, California 92037 SUBJECT: Dear Dr. Sabba: SCOPE File No. 1106E5A-16 SITE INSPECTION Proposed Commercial Building Site 3050 Madison Street City of Carlsbad P.O. Box 119::i Lakeside, California 92040 (619) 443-0060 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 3 story commercial structure with underground parking. 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 a test exploration approximately IO feet in depth and tested for density, shear strength and expansive characteristics. SITE CONDITIONS The subject site is located on east side of Madison Street. The property is relatively level with a 2 to 3 degree slope from east to west. The site is currently occupied by a commercial structure with a 2 foot high retaining wall along the front. The existing structure will be removed to make way for the proposed development. Adjacent properties are commercial and residential. Manmade fill soils were encountered to a depth of 12 to 18 inches and loose native soils to depth of2 feet during the course of our inspection. 1 Dr. Bruce Sabha File No. 1106E5A-l 6 July 7, 2016 SITE EROSION CONTROL 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 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 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 drainage and eliminate areas where water might pond. SOIL CONDITIONS Soils encountered in the test explorations were fill soils consisting of firm, grey, silty fine sands (base material) with filter fabric to approximately 10 inches in depth. These surface soils were underlain by native soils consisting of firm to medium dense, light red brown with pockets of grey, silty, sands with a light clay binder to the bottom of the excavations approximately 10 feet in depth. These native soils became denser with depth. The soils we encountered were not considered to be detrimentally expansive with respect to change in volume with change in moisture content. CONCLUSIONS AND RECOMMENDATIONS I. Representative samples of the foundation soils were remolded to 90% of maximum dry density. Based on the following test results, a safe allowable bearing value of at least 2000 pounds per square foot may be used in designing the foundations and slab for the proposed structure. This value may be increased by one third for wind and/or seismic loading. Description Expansion Index Angle of internal friction Cohesion Unit weight Maximum Dry Density Optimum Moisture Content 2 Light red brown silty sands 24 31° 205 psf 109.9 pcf 122.1 pcf 9.8% Dr. Bruce Sabba File No. 1106E5A-16 July 7, 2016 2. The seismic parameters for the site coordinates 33. I 6029°N, 117.34622°W for assumed Site Class D are as follows: USGS-Provided output 5 5 = 1.150g S, = 0.4-.+l g SMS = 1.196 g s,.,, = 0.688 g S05 = 0.797 g so, = 0.458 g :Jeten"11lnisti:: grcund n-icticns in the dii-ecbc:n cf n1a>:in-1urn h::;r-izGrta! resoGnse. please ,.·etun"' t::: tr.= .3~:c:ii::,3I!:::::-s .3rd select the ·,,2001; NE~-n=:_p··' building code reference dccument. MCER Response Spectrum Design Response Spectrum 0.88 c,.1 s 0.08 0. ,}!) ..... -+---+--+---+---,,---;----;--+----+- 0.1)(1 (1.:w 0.40 O.bO 0.80 1.00 1.20 1.40 1 i;o 1.80 2.00 Period, T (sec) Period, T ( sec) 3. The existing fill soils and compressible native are not suitable for supporting the proposed structure. In addition, removal of footings, slabs, irrigation lines, etc. will further loosen the soil. We anticipate that these soils will be removed during the excavation of the basement parking; if any shoring is required, OSHA standards should be used. This should be confirmed during or after the basement excavation. If any fill or loose soils remain, in order to provide uniform support for the proposed structures, the soils in proposed building areas should be excavated to firm natural ground, approximately three feet in depth, replaced and recompacted to 90 percent compaction in accordance with the following Grading Specifications. The recompaction should extend at least 5 feet outside the proposed building footprints. Any organics or other deleterious material that may be encountered should be removed prior to recompaction. 4. Conventional spread footings founded a minimum of 12 inches below lowest adjacent grade and having a width determined by the allowable soil bearing value as detailed above are recommended for foundation support. Footing widths should be at least 12 inches for continuous footings and 24 inches for square footings due to practical considerations as well as Building Code requirements. These recommendations are 3 Dr. Bruce Sabba File No. 1106E5A-16 July 7, 2016 based upon the soil type encountered and do not take into consideration the proposed bearing load. 5. Reinforcing in footings should consist of at least one #4 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. 6. For concrete consideration, the maximum water-cementitious material ratio, by mass: 0.50. The Minimum design compressive strength, MPa (psi): 28 (4000). The type(s) of concrete specified and used should be determined by the Structural Engineer. 7. 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% +/-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 4 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. 8. Resistance to horizontal movement may be provided by allowable soil passive pressure and/or coefficient of friction of concrete to soil. The allowable passive pressure may be assumed to be 500 psf at the surface and increasing at the rate of 400 psf per foot of depth. These pressures assume a frictionless vertical element, no surcharge and level adjacent grade. If these assumptions are incorrect, we should be contacted for values that reflect the true conditions. The values are for static conditions and may be increased 1/3 for wind and/or seismic loading. The coefficient of friction of concrete to soil may be safely assumed to be 0.4. 4 Dr. Bruce Sabha File No. 1106E5A-16 July 7, 2016 9. Active pressures for the design of unrestrained, cantilevered, individually supported retaining walls, capable of slight movement away from load may be considered to be equivalent to the pressures developed by a fluid with a density of 35 pcf. This value assumes a vertical, smooth wall and level drained backfill. We should be contacted for new pressures if these assumptions are incorrect. Restrained walls, incapable of movement away from load without damage such as basement walls, should be designed for the additional equivalent fluid of 28 pcf applied triangularly for cohesionless type soils and trapezoidally for cohesive type soils. 10. The above design values and foundation design assume that retaining wall excavations will expose soils similar to those we tested during our site inspection. SEISMIC LOADING FOR RETAINING WALLS The seismic event induced dynamic load should be added to the lateral static pressures on basement, foundation and retaining walls for projects located in seismic design categories D, E or F. The following is the calculation for the dynamic load, which should be applied 111 addition to the static loads. • References: USGS and IBC 2012 • Site Address: 3050 Madison Street, City of Carlsbad • Site Soil Classification: Site Class "D" • Ss = 1.150 g • Si =0.441g Sms = 1.196 g Sm1 = 0.688 g Sds = 0.797 g Sdl = 0.458 g • Kh =Peak Ground Acceleration= Sds / 2.5 = 0.797 / 2.5 = 0.3188 • Backfill Density (Assumed 90% compaction) = 122.1 * (0.90) = 109.9 PCF • H =The height of the level backfill behind the wall in FT • Dynamic Load, for Yielding Wall= (.375) (0.3188) (109.9 PCF) (H2) = 13 .1 lbs/ft (H2) • Dynamic Load, for Non-Yielding Wall= (0.3188) (109.9 PCF) (H2) = 35.0 lbs/ft (H2) 5 Dr. Bruce Sabba File No. l 106E5A-16 July7,2016 • The resultant dynamic load acts at a height of 0.6H above the base of the wall. The dynamic load is represented as an inverted trapezoidal pressure distribution. These lateral earth pressures assume the walls are totally drained with no water behind them and assume there is no surcharge applied. If there 1s any surcharge applied, it should be considered accordingly. See Figure below: SITE AND SURFACE DRAINAGE 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 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 detennined by the Engineer of Record. 6 Dr. Bruce Sabba File No. 1106E5A-16 July 7, 2016 GROUNDWATER AND SURF ACE WATERS During our site inspection, we installed an observation pipe to depth of 10 feet. We revisited the site after 72 hours and determined 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 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 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 plants and soil specified along with proper irrigation used should be determined by the Landscape Architect. If any grading is proposed or contemplated for this project, the following grading specifications should be utilized. RECOMMENDED GRADING SPECIFICATIONS Proposed Commercial Building Site 3050 Madison Street City of Carlsbad GENERAL: Soil Testers and 'Engineer' are synonymous hereinafter and shall be employed 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 schedules and any unforeseen soil conditions. Substandard conditions or workmanship, inadequate compaction, adverse weather, or 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 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 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 --ASTM D1557-70 --ASTM D1556, D2922 and D3017 --UBC ST AND ARD 29-2 --ASTM D3080-72 7 Dr. Bruce Sabha Gradation & Grain Size Capillary Moisture Tension Organic Content File No. 1106E5A-l 6 July 7, 2016 --ASTM DI 140-71 --ASTM D2325-68 --% Weight loss after heating for 24 hours at 300° F and after deducting soil moisture. LIMITING SOIL CONDITIONS: Minimum Compaction Expansive Soils Insufficient fines Oversized Particles 90% for 'disturbed' soils. (Existing fill, newly placed fill, plowed ground, etc.) 84% for natural, undisturbed soils. 95% for pavement subgrade within 2' of finish grade and pavement base course. Expansion index exceeding 20 Less than 40% passing the #4 sieve. Rocks over 1 O" in diameter. 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 stepped uphill with benches 1 O' or greater in width. Scarify area to receive fill to 6" depth and compact. 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 compacted and tested. SUBDRAINS shall be installed if required by and as directed by and detailed by the 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 SDR-35, Poly-Vinyl-Chloride or Acrylonitrile Butadienne Styrene plastic. Rock filter material shall conform to the following gradation: Sieve size: %Passing: 3/4" 90-100 #4 25-50 #30 5-20 #200 0-7 Subdrains shall be set at a minimum gradient of 0.2% to drain by gravity and shall be tested 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 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 8 Dr. Bruce Sabha File No. 1106E5A-16 July 7, 2016 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 exceeding 90% before any construction supported by the compacted cap. The non-expansive soil comprising the cap should conform to the following: Minimum Compaction Maximum Expansion Index Minimum Angle of Internal Friction Cohesion Intercept 90% 30 33 Deg 100 psf UNFORESEEN CONDITIONS: Soil Testers assume no responsibility for conditions, 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 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'. 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. Plates I through II are parts of this report. Respectfully submitted, e~ eek Chin C. Chen, RPE C 34442 CCC/mlj 9 E>:JSTIN9' .J-jOl/SE --~--=-~----·-----~=-----~·····=·. -= f'1ADISOA/ ST/2..E'E• Ci EXPLORATION TRENCH JOB NO. LOCATION OF / !Oto£5/t-Jw BY EXPLORATION TRENCHES 11\1 L v DATE PLATE: I 0(;; -2-OJ -l(p 11421 Woodside Ave .. Suite C Santee. California 92071 (619) 562-0500 Dr. Bruce Sabha File No. 1106E5A-16 Plate No. II EXPLORATION NUMBER 1 Date Logged: Date Reported: 06/14/16 07/07/16 Equipment Used: Groundwater: Depth Unified Classifications Soil Description 0 to l' SM Grey, slightly moist firm Base material 1 to 1 O' SM Light orange brown with pockets of grey, firm to medium dense, with light clay binder bottom of excavation July 7, 2016 Excavator Not Encountered Soil Type SILTY SAND (Fill) moist, 1 SILTY SAND (Native)