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HomeMy WebLinkAboutPD 2019-0012; BLOCK RESIDENCE; GEOTECHNICAL INFILTRATION RECOMMENDATIONS; 2019-10-23I-] W-' CHRiSTiAN WHEELER ENGINEEftING RE( _7EPVED ov U W'U't 2U110 LANL D?VEIOPMENT ENGtNEERNG RECORD COPY L initial Date CWE 2190330.04 October 23, 2019 Brad Block 3512 Seagate Way, Suite 130 Oceanside, California 92056 Subject: Geotechnical Infiltration Recommendations, Pervious Payers Proposed Block Residence, 3291 Highland Drive, Carlsbad, California References: 1) Omega Engineering Consultants, Grading Plans, Block Residence, 3291 Highland Drive, Carlsbad, California, undated 2) Christian Wheeler Engineering, Report CWE 2190330.02, dated July 19, 2019 Dear Mr. Block: At the request of Jacqueline Sayler with Omega Engineering, we have prepared this report to provide infiltration recommendations for the proposed pervious payers to be constructed at the subject site. In reviewing the referenced grading plans pervious payers are proposed for a portion of the driveway located north of the residence and pedestrian walkways located east and west of the residence. Our previous subsurface explorations consisted of 8 hand-dug test pits which assessed the soil conditions at the subject site. The site was found to be underlain by Quaternary-age old paralic deposits which are overlain in areas by a relatively thin layer of topsoil and/or artificial fill. As observed within our test pits these materials consisted of silty sand (SM). These materials were found to be subject to collapse upon wetting. This can be mitigated by a combination of remedial grading, geo-fabric, and incorporating cut-off walls. 3980 Home Avenue + San Diego, CA 92105 4, 619-550-1700 + FAX 619-550-1701 S S CWE 2190330.04 October 23, 2019 Page No. 2 According to the Natural Resources Conservation Service (NRCS) Web Soil Survey, the Hydrologic Soil Group at the subject site is labeled as Marine loamy coarse sand (MIC) and has a hydrologic soil rating of B. Group B soils have moderate infiltration rates when thoroughly wet and a moderate rate of water transmission. Our subsurface explorations corroborate this classification and it is our opinion that the subject site is suitable for partial infiltration provided the recommendations provided in this report are adhered. The paver sections detailed on the referenced plans are suitable for the anticipated subgrade soil conditions and traffic loads provided the recommended remedial grading preparations (CWE 2190330.02) and are performed. The proposed payers should be installed per manufacture specifications. The suitability of the payers to support traffic loads should be confirmed by others. Prior to placing the crushed rock material, the subgrade soils should be scarified to a depth of 12 inches, moisture- conditioned and compacted to at least 95 percent of its maximum dry density as determined in accordance to ASTM D 1557. Geogrid material such as Tensar TX130S or equivalent is recommended under the crushed rock portion of the paver section within the driveway areas and is optional under the pedestrian areas. The bedding, base, and subbase layers should also extend the full detailed thickness to the perimeter concrete curbs. We also recommend that concrete curbs be poured along the edge, of the proposed payers and that the curbs extend at least 24 inches into the subgrade soil or 12 inches below the bottom of the subgrade rock storage section, whichever is greater. For pervious paver areas located adjacent to foundations, we recommend that the foundations extend at least 12 inches below the bottom of the subgrade rock storage section. The recommendations and opinions expressed in this report reflect our best estimate of the project requirements based on our evaluation of the subsurface soil conditions encountered within our explorations and the assumption that the soil conditions do not deviate appreciably from those encountered. It should be recognized that the performance of the BMPs may be influenced by undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unexplored areas. Any unusual conditions not covered in this report that may be encountered during site development should be brought to the attention of the soils engineer so that he may make modifications if necessary. In addition, this office should be advised of any changes in the project scope, 7EER/ MFLOWERS 0 rr c) co / CAY C'WE 2190330.04 October 23, 2019 Page No. 2 proposed site grading or storm water BMP design so that it may be determined if the recommendations contained herein are appropriate. This should be verified in writing or modified by a written addendum. If you have any questions after reviewing this report, please do not hesitate to contact our office. This opportunity to be of professional service is sincerely appreciated. Respectfully submitted, CHRISTIAN HEELER ENGINEERING 377 Daniel B. Adler, RCE # 36037 ec: brad@gcs-inc.com dant@noaainc.com jsayler@omega-consultants.com Daniel J. Flowers, CEG #2686