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Home My WebLink AboutCD 2020-0003; PACIFIC RIM; FIELD PERCOLATION TESTING AND PROPOSED BASIN AREAS AT HOLES 1 AND 18; 2020-02-02. . LAND DEV··;_LO P~."r:::NT Leighton Consulting , Inc. ENGil\,_,.f .·,. .. '"._; A LEIGHTON GROUP COMPANY March 2, 2020 To: Xenia Hotels & Resort, Inc. 200 S. Orange Ave. Suite 2700 Orlando, FL 32801 Attention: Mr. Stephen Long RECORD COPY Qc(L.. Initial Project No. 12493.003 Subject: Field Percolation Testing for Proposed Basin Areas at Holes 1 and 18, Aviara Golf Course, Carlsbad, California As requested, Leighton Consulting, Inc. (Leighton) has performed field percolation testing at proposed basin areas for Holes 1 and 18 at the Aviara Golf Course in Carlsbad, California. The purpose of the field percolation testing is for determining the feasibility of on-site near surface storm water infiltration in general accordance with the County of San Diego Storm Water Standards (2019) using section D.2.1, Borehole Percolation Test Method. This letter provides our findings, including field exploration, testing procedures, measured percolation rates, and calculated infiltration rates for the test locations. In accordance with the County of San Diego Storm Water Standards, D.2.1, the Borehole Percolation Test Method was selected and performed between February 27 and 28, 2020. Specifically, we advanced two 3.25-inch diameter borings, P-1A and P-2A, to depths of approximately 2 feet below the existing ground surface (bgs). Approximate locations of the field percolation test locations are shown on the attached Exhibits A and B (Hole 1 and Hole 18, respectively). In summary, the boreholes were filled with water and allowed to pre-soak for at least 24 hours prior to performing the in-situ percolation testing. The water level in each test hole was measured at 30-minute intervals using a water meter, which is accurate to 0.01 feet. Refilling of the boreholes was done at 30-minute intervals, or as needed. The total testing period lasted approximately 6 hours or until consistent measurements were observed. 3934 Murphy Canyon Road, Suite B205 ■ San Diego, CA 921234425 858.569.6914 ■ Fax 858.292.0771 ■ www.leightongroup.com 12493.003 Field testing data is presented in Appendix A. After the conclusion of in-situ percolation testing, the boreholes were backfilled with soil cuttings. Based on our field percolation testing (P-1 A and P-2A), the in-situ percolation rates and calculated infiltration rates at tested locations and depths are summarized in Table 1. We have used the following equation based upon the Porchet Method to convert measured percolation rates to infiltration rates in accordance with the County of San Diego BMP Design Manual (2019). In addition, we have included a factor of safety of 2 for the evaluation of existing site conditions. The storm water design factor of safety, if applicable, should be determined by the civil engineer and reviewed by the geotechnical consultant. Test No. P-1A (Hole 1) P-2A (Hole 18) 1, =AH* 60 * r at(r+2HAvG) Where: It = calculated infiltration rate, inches/hour aH = change in head over the time interval, inches at = time interval, minutes r = radius of test hole HAvG = average head over the time interval, inches Table 1 Percolation and Infiltration Rates Measured Calculated Calculated Depth Soil Type Percolation Infiltration Infiltration (ft) Rate Rate Rate w/ FS of (min/in) (inch/hr) 2 (inch/hr) Light 2 Brown Silty 25.0 0.230 0.115 Sand (SM) Light 2 Brown Silty 83.3 0.054 0.027 Sand (SM) 2 Leighton 12493.003 It is important to note that percolation rates are not equal to infiltration rates. As a result, we have made a distinction between percolation rates where water movement is considered laterally and vertically versus infiltration rates where only the vertical direction is considered. It should also be noted that the above percolation test results are representative of the tested locations and depths where they were performed, and that percolation test field measurements are accurate to 0.01 feet. Varying subsurface conditions may exist outside of the test locations, which could alter the calculated percolation rate indicated below. It is also possible that the long-term rate of transmissivity of permeable soil strata may be lower than the values obtained by testing. Infiltration may be influenced by a combination of factors including but not limited to: a highly variable vertical permeability and limited lateral extent of permeable soil strata; a reduction of permeability rates over time due to silting of the soil pore spaces; and other unknown factors. Accordingly, the possibility of future surface ponding of water, as well as, shallow groundwater impacts on subterranean structures such as basements, underground utilities, etc. should be anticipated as possible future conditions in all design aspects of the site. The findings and conclusions contained within this letter are based on data obtained from limited number of observations, site visits, soil excavations, samples, and tests. Such information is, by necessity, incomplete. The nature of many sites is such that differing soil or geologic conditions can be present within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time. In addition, changes made during design development and construction should be reviewed by Leighton to determine if recommendations are still applicable. Please also note that the evaluation in this letter report was limited to assessment of the geotechnical aspects of the project and did not include evaluation of structural design. 3 Leighton 12493.003 If you have any questions regarding our letter, please do not hesitate to contact this office. We appreciate this opportunity to be of service. Respectfully submitted, LEIGHTON CONSUL TING, INC. William D. Olson, RCE 45283 Associate Engineer Attachments Exhibit A-Hole 1 Field Percolation Test Location Exhibit B -Hole 18 Field Percolation Test Location Appendix A -Field Percolation Test Results Distribution: E-mail 4 Leighton 12493.003 EXHIBITS Ca!o'fomt. 92011 .c· .:,_g~ :>11 ♦ Exhibit A -Hofe 1 Field Percolation Test Location ,4~ ,,;., ..... .J~ ~ [Exhibit a -Hole 18 IField Percolation Test Location 12493.003 APPENDIX A FIELD PERCOLATION TEST RESULTS FIELD PERCOLATION TEST DATA SHEET Project Name: XHR Aviara Golf Proiect No.: 12493.003 Proi. Address: 7447 Batiquitos Drive, Carlsbad, Ca SOIL TYPE / TEST LOCATION / BOREHOLE Soil Type: Light Brown Silty sand Location: Hole 1A Hole Dia: 3.25" De th 2' Tested by:SLR/TAS Pre-Saturation Date:2-27-20 Test Date:2-28-20 Notes: Measurements in 100ths offoot Time of Day Interval / Notes Water Level Time of Day Interval / Notes Water Level 7:59 Start 0.9 1:03 29Min 1.2 8:27 28 Min 1.14 1:33 30 Min 1.31 8:29 add water 0.95 2:03 30Min 1.41 9:00 31 min 1.08 9:30 30 min 1.2 10:00 30 Min 1.29 10:01 add water 1 10:32 31 Min 1.21 10:33 add water 0.97 11:03 30 Min 1.2 11:33 30 Min 1.3 11:34 add water 1.01 12:03 30 Min 1.26 12:33 30 Min 1.35 12:34 add water 0.9 I ~OR OFFICE USE ONL y DATE RECEIVED: By: Notes: 25 min per inch or 2.4 inches per hour Leighton FIELD PERCOLATION TEST DATA SHEET Project Name: XHR Aviara Golf Proiect No.: 12493.003 Proj. Address: 7447 Batiauitos Drive, Carlsbad, Ca SOIL TYPE / TEST LOCATION / BOREHOLE Soil Type: Light Brown Silty sand Location: Hole 18A Hole Dia: 3.25" De th 2' Tested by:SLR/TAS Pre-Saturation Date:2-27-20 Test Date:2-28-20 Notes: Measurements in 1 00ths of foot Time of Day Interval / Notes Water Level h"imeofDay Interval / Notes Water Level 7:37 Start 0.9 8:10 33 Min 0.96 8:40 30 Min 1.01 9:10 30 min 1.04 9:40 30 min 1.08 10:12 32 Min 1.11 10:13 add water 0.95 10:48 35 Min 1 11 :14 26 Min 1.03 11:44 30 Min 1.05 12:16 32 Min 1.08 12:47 31 Min 1.12 1 :17 30 Min 1.15 1:47 30 Min 1.18 I ~OR OFFICE USE ONL y DATE RECEIVED: By: Notes: 83.3 min per inch or . 72 inches per hour