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HomeMy WebLinkAboutDEV 2016-0049; 7605 ROMERIA ST; FINAL SOILS REPORT; 2020-03-03K.F. Stephens, Inc. File No. 1098E2-19 February 4, 2019 The grading was perfo1med for the purpose of scarifying the surface and placing Class II Base material under the slab of the existing level building pad for the construction of the proposed residential structure. SECTION No. 2. SOIL CONDITIONS Soils used in the fill were those generated from the on-site grading operation and imported from off site. Soils encountered during grading were substantially the same as those encountered in the Preliminary Soils Investigation dated October 22, 1971, prepared by Benton Engineering, Inc., Project No. 71-10-18F, and in our Update to Preliminary Soils Investigation and Report of Compacted Filled Ground dated March 1, 2017, Addendum I dated July 31, 2017 and Addendum II dated May 1, 2018. EARTHWORK Preparation: Prior to placement of fill, the areas to receive fill were scarified, watered and compacted to 90 percent. Placing and compacting fill: Fill soil was placed, watered and mechanically densified in the areas indicated on attached Plate No. 1. A D-5 ripped each lot down 12", the soils were moisturized and the sub grade recompacted. A representative of our firm tested and recorded the results. Class II was brought in to each lot and compacted with D-5. Class II base material was verified to be a minimum of 12 inches in depth for each house pad. A representative of our firm tested and recorded the results. The sub grade passed all tests as required and the 12" section of Class II passed all tests as required. Field density test results: To verify compaction, field density tests were performed in accordance with applicable American Society of Testing and Materials (ASTM) test methods. Test method ASTM D1556-82 was used at the indicated locations. SECTION No. 3. SUMMARY AND RECOMMENDATIONS Based on the work and tests described hereinbefore and work description set forth in Section 1, 'Scope', we conclude: 1. The filled ground has been compacted to 90%. 2. The placement of fill has been accomplished in accordance with the grading specifications and with current standard practices. 2 K.F. Stephens, Inc. File No. 1098E2-19 February 4, 2019 3. Spread footings will have a minimum allowable beating value of at least 1500 pounds per square foot. The allowable bearing value will be considerably more for footings larger than 12 inches wide and/or 12 inches deep. If loads heavier than 1500 pounds per square foot for continuous footings are anticipated, we should be contacted for an increased bearing value. 4. The soils are considered to be highly to critically expansive as stated in the Benton Engineering repo1i dated April 2, 1973 . From our field observation and lab testing, we found the sites to be highly expansive with an expansion index of 104. Due to the possibility of critically expansive soils referenced in the Benton report, we are amending our recommendations to the following: 5. The following foundation depth is a minimum due to the expansive nature of the soil and must be used in order to prevent possible damage to the proposed structures from adverse effects of expansive soils. These recommendations for footings and slabs are based upon the soil type only and do not take into consideration the structural requirements. ■ Use continuous exterior perimeter foundations (including door openings). They should be founded a minimum of 30 inches below lowest adjacent grade with a minimum width of 12 inches. ■ Interior footing depth should exceed 24 inches below top of slab or 24 inches below lowest adjacent grade for raised floor construction with a minimum width of 12 inches. ■ Reinforce continuous concrete foundations as a beam with at least one #5 bar positioned 3 inches above the bottom of footing and one #5 bar positioned 1 inch below top of foundation or top of finish floor. 6. Concrete Slab-On-Grade should be designed by the project's structural engineer based on anticipated loading conditions. Soil Testers recommends that conventional reinforced concrete SOG for this project be founded on 6 inches of Class II Virgin Aggregate Base (With approximately 2% +/-of 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 also 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, and midway between 4 inches of moist clean sand. 3 K.F. Stephens, Inc. File No. 1098E2-19 February 4, 2019 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. As an alternative, post-tensioned, PIT, slabs designed by a qualified structural design engineer may be considered. Geotechnical recommendations for the design of PIT SOG will be provided upon request. 7. We observed the placement of the subdrains, the fabric around the pipe and the waterproofing behind the retaining walls. SECTION No. 4. LIMITATIONS UNIFORMITY OF SOIL CONDITIONS: The values presented in this report are based on our evaluation of the observed, exposed soil conditions. We have assumed that the soil conditions in the remaining portions of the site can be interpolated without significant deviation in physical properties. We have made a conscientious effort to select representative test locations and to provide enough tests for a statistically adequate population in excess of current standard practices. However, parameter values may be substantially different in other areas due to unforeseeable variations in the soils. Also, the parameters are affected in time by the moisture-expansion (volume)-pressure changes that seriously affect the tested values. ENGINEERING INTERPRETATION: We are available for consultation and should be made aware of any pertinent condition or problem. Our conclusions will be re-evaluated and any problem or potential problem solved with a minimum effort and cost before it gets out-of-hand. TIME LIMITS: This report presents conclusions and findings that are valid as of this date. Changes on this site and adjacent property including grading, improvements, drainage, erosion, etc. may directly affect the findings, conclusions and recommendations presented herein. Subsequent alterations or conditions may invalidate these recommendations and values. The values in this report will probably remain applicable for one year provided the site conditions remain unaltered. After this period, we should be contacted to inspect the site and review this report so that we may verify its validity. 4 K.F. Stephens, Inc. File No. 1098E2-19 February 4, 2019 WARRANTY: Certain risks are involved with geotechnical and soil engineering work, which should be recognized by those involved. We have performed our services in accordance with current standard practices and procedures. These practices and procedures are those presently utilized by members of our profession in this region. We do not express or imply a warranty or guarantee regarding these services. OUTSIDE RESPONSIBILITY: It is the responsibility of the client (firm or person to whom this report is submitted) to ensure that the information presented herein is made available to the concerned parties. In addition, it is the client's responsibility to make certain that any construction reflects any applicable requirements and conforms with the current codes of jurisdictive governmental agencies. PROJECT CONCEPT: We should be notified of any changes in the proposed structures, construction, or site grading, or project concept so that any addendum or modifications to this report may be provided as necessary. SOIL TEST METHODS: Summary of the GRADING SPECIFICATIONS USED for Proposed Residential Building Site 7605 Romeria Street City of Carlsbad Maximum Density & Opt Moisture Density of Soil In-Place ASTM D1557-78 ASTM D1556-82 Soil Expansion Shear Strength Gradation & Grain Size Capillary Moisture Tension LIMITING SOIL CONDITIONS: Minimum Compaction Expansive Soils Insufficient Fines Oversized Particles UBC STANDARD 29-2 ASTM D3080-72 ASTM D1140-71 ASTM D2325-68 90% for "disturbed" soils. (Existing fill, newly placed fill, plowed ground, etc.) 85% 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. 5 K.F. Stephens, Inc. File No. 1098E2-19 February 4, 2019 Page L-1 LABORATORY TEST RESULTS The maximum dry densities and optimum moisture contents of the fill materials as determined by the A.S.T.M., D1557-78, Method A, which uses 25 blows of a 10 pound rammer falling from a height of 18 inches on each of 5 layers in a 4 inch diameter 1/30 cubic foot compaction cylinder, are presented as follows: Soil Type 1 Grey, silty, clayey, fine sand 2 Grey, silty, fine to coarse sand with gravel (Class II Virgin Base) Maximum Dry Density lb./cu.ft. 121.8 138.6 Optimum Moisture Content dry wt. 14.4 6.4 K.F. Stephens, Inc. Page T-1 TEST SOIL NO. TYPE 1 1 2 2 3 2 4 2 5 2 6 2 7 * f.g. = finish grade DEPTH OFFILL ATTEST IN FEET f.g. base base base base base base File No. 1098E2-19 TABLE OF TEST RESULTS A.S.T.M., D1556-82 FIELD MOISTURE % 17.8 4.2 5.4 4.7 3.9 4.9 3.0 DRY DENSITY P.C.F. 111.6 129.4 132.8 129.4 135.5 130.6 140.9 *Maximum density provided by material supplier MAXIMUM DRY February 4, 2019 DENSITY PERCENT P.C.F. COMPACTION 121.8 91.6 138.6 93.4 138.6 95.8 138.6 93.4 138.6 97.8 138.6 94.2 142.9 98.6