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Home My WebLink AboutCDP 2022-0008; MARTIN RESIDENCE; PRELIMINARY STORM WATER INFILTRATION FEASIBILITY STUDY; 2022-11-02 November 2, 2022 John Martin CWE 2210558.02 3301 Lincoln Street Carlsbad, California 92008 Subject: Preliminary Storm Water Infiltration Feasibility Study Proposed Martin Residence, Lot 5 of Buena Vista Circle, Carlsbad, California References: 1) Christian Wheeler Engineering, Report of Preliminary Geotechnical Investigation, Proposed Martin Residence, Lot 5 of Buena Vista Circle, Carlsbad, California, dated December 8, 2021, Job No. CWE 2210558.01 2) City of Carlsbad BMP Design Manual, dated September 1, 2021 3) Pasco Laret Suiter & Associates, DMA Exhibit, Martin Residence, Vacant Lot on Buena Vista Circle, Carlsbad, undated Dear Mr. Martin: At your request, we have prepared this feasibility study to address the potential for storm water infiltration at the subject site in accordance with the City of Carlsbad BMP Design Manual. In general, the purpose of our feasibility analysis is to provide design phase infiltration rates based on our borehole percolation tests and our subsurface explorations. SITE AND PROJECT DESCRIPTION The subject site is an undeveloped residential lot, identified as Assessor’s Parcel Number 155-221-05, which is located adjacent to and north of Buena Vista Circle in in the City of Carlsbad, California. Topographically, the southeast portion of the site is characterized by a relatively level building pad with an elevation of approximately 43 feet (PLSA). A natural bluff descends from the northwest side of the level pad area of the site to the northwest perimeter of the. Overall, the bluff displays a general inclination of about 3:1 (horizontal to vertical). The bottom of the bluff along the northwest portion of the site is at an approximate elevation of 6 to 8 feet (PLSA). CHRISTIAN WHEELER E N G I N E E R I N G 3 9 8 0 H o m e A v e nu e S a n Di e g o , C A 9 2 1 05 6 1 9 -5 5 0- 1 7 00 F A X 61 9 - 55 0 - 17 0 1 CWE 2210558.02 November 2, 2022 Page 2 We understand that a one- to two-story single-family residence with an attached garage, swimming pool, and other normally associated appurtenances are to be constructed within the upper, pad area of the lot. We anticipate that the proposed residence will be of conventional, wood frame construction with an on-grade concrete floor slab. We also anticipate that the proposed improvements will be supported by conventional shallow foundations and possibly drilled, cast-in-place concrete piers, depending upon the configuration of the proposed pool. Grading to accommodate the proposed improvements is expected to be limited to cuts and fills of less than 2 feet from existing site grades and creating the excavation for the proposed swimming pool. It is our understanding that the proposed BMPs at the site will consist of a biofiltration basin and a tree well. As part of the project’s required storm water permit processing (completed by others), a feasibility analysis for storm water infiltration has been requested. This report addresses feasibility and desirability of infiltration related to geotechnical conditions as described in the City of Encinitas BMP Design Manual, which may affect the potential for on-site storm water infiltration. To aid us in the preparation of this report, we were provided with an undated, DMA Exhibit prepared by Pasco Laret Suiter & Associates. A copy of the DMA Exhibit has been used as the base for our Site Plan and Geotechnical Map, and is included herein as Plate No. 1. FIELD INVESTIGATION Previous subsurface explorations at the site consisted of five, 8-inch-diameter hollow stem auger borings which extended up to approximately 41 feet below existing site grades. The approximate locations of the subsurface explorations are shown on Plate No. 1 of this report and logs of the explorations are presented in Appendix D of this report. The borings were logged in detail with emphasis on describing the soil profile. Low permeability and relatively impermeable materials were identified in the borings. No evidence of soil contamination was detected within the samples obtained. GEOLOGIC SOIL DESCRIPTION: Based upon the findings of our subsurface explorations and review of readily available, pertinent geologic and geotechnical literature, it was determined that the project area is generally underlain by Tertiary-age materials of the Santiago Formation which are mantled by Quaternary-age old paralic deposits and a thin veneer of topsoil. MAPPED HYDROLOGIC SOIL GROUP: According to the Natural Resources Conservation Service (NRCS) Web Soil Survey, the majority of the site is located in the map unit designated Terrace Escarpments CWE 2210558.02 November 2, 2022 Page 3 (TeF). Terrace Escarpments (TeF) are unclassified and do not have a hydrologic soil rating; however, the City of Carlsbad BMP Design Manual considers urban/unclassified soils to have a hydrologic soil rating similar to group D soils. Group D soils are expected to have a very slow infiltration rate when thoroughly wet and a very slow rate of water transmission. The southeast portion of the site adjacent to Buena Vista Circle is mapped in the unit designated Marina loamy coarse sand (MIC) which has a Hydrologic Soil Group rating of B. Group B soils have moderate infiltration rates when thoroughly wetted and a moderate rate of water transmission. The NRCS Web Soil Survey map for the subject site and corresponding map unit description are presented in the Attached Appendix E. From our explorations and testing it is our opinion that the old paralic deposits underlying the site correlate with a Group A or Group B hydrologic soil group. GROUNDWATER The depth to seasonal high groundwater beneath the site is expected to fluctuate seasonally. Our previous subsurface exploration encountered groundwater at a depth of 35 feet below existing site grades. From our findings it is our opinion that the historic high groundwater level will be in excess of 30 feet below existing site grades. INFILTRATION RATE DETERMINATION FIELD MEASUREMENTS: Percolation testing was performed within 4 borings that were drilled within the proposed storm water infiltration areas at the site. The approximate locations of the percolation borings are shown on Plate No. 1. The 8-inch-diameter borings, which are labelled as PT-1 through PT-4, were drilled to depths ranging from approximately 3 feet to 5 feet in the areas of the proposed BMPs. Once cleaned of slough, a 3-inch diameter perforated pipe was set in the excavation and surrounded by ¾-inch gravel to prevent caving. After pipe installation, the percolation borings were presoaked. The field percolation rates were determined the following day by using the falling head test method. It should be noted that no water remained within the borings from presoaking on the previous day. The initial water level was established by refilling the test holes and percolation rates were monitored and recorded every 10 minutes over a period of approximately 3 hours until the infiltration rates stabilized. Measurements were taken using a water level meter (Solinst, Model 101) with an accuracy of measurement of 0.005 foot (0.06 inch). To account for the use of gravel placed around the perforated pipe, an adjustment factor of 0.44 was used in the calculations. CWE 2210558.02 November 2, 2022 Page 4 FACTOR OF SAFETY: A safety factor between 2.0 and 9.0 must be applied to the infiltration rate. The City of Carlsbad BMP Design Manual states that “If the propose BMP utilizes an underdrain a default safety factor of 2.0 may be applied or a more detailed safety factor may be determined per Table D2-3. If the proposed BMP does not utilize an underdrain, then a safety factor must be determined through the completion of Table D.2-3.” We have included design infiltration rates for BMPs which incorporate an underdrain and those which don’t. Table D.2-3 has been completed and is presented in Appendix B of this report. The completion of Table D.2- 3 has determined a safety factor of 3.13. The average field infiltration rates, safety factor, and the design infiltration rates are presented in Table I. TABLE I: INFILTRATION RATES Test No. Location Soil Underlying BMP Depth of Testing (Inches) Field Infiltration Rate (Inches per hour) Average Field Infiltration Rate Design Infiltration Rate with an Underdrain (Average Infiltration Rate with Default Safety Factor of 2 Applied) Design Infiltration Rate without an Underdrain (Average Infiltration Rate with Safety Factor of 3.13 Applied Per Table D2-3) PT-1 See Plate No.1 Old Paralic Deposits (Qop) 55 1.14 1.35 inches per hour 0.67 inches per hour 0.43 inches per hour PT-2 51 1.52 PT-3 52 1.77 PT-4 36 0.95 Infiltration and percolation are two related but different processes describing the movement of moisture through soil. Lateral and downward movement of water into soil and porous or fractured rock is called percolation, and the downward entry of water into the soil is called infiltration. The direct measurement yielded by a percolation test tends to overestimate the infiltration rate, except perhaps in cases where an infiltration basin is similarly dimensioned to the borehole. As such, adjustments of the measured percolation rates were converted into infiltration rates using the Porchet Method. The spreadsheet used for the conversion is included in Appendix C. POTENTIAL STORM WATER INFILTRATION HAZARDS Potential infiltration restrictions have been analyzed in accordance with Table D.1-1 of the City of Carlsbad BMP design Manual. Potential restriction elements and mitigation measures are discussed below. We have also CWE 2210558.02 November 2, 2022 Page 5 completed Table D.1-1 for proposed the proposed BMPs at the site which is included in Appendix A of this report. SETTLEMENT AND VOLUME CHANGE: Settlement and volume change can occur when water is introduced below grade. Settlement refers to a condition when soils decrease in volume (i.e. hydro collapse, calcareous soils, consolidation or liquefaction). Heave refers to expansion of soils or an increase in volume (i.e. expansive soils or frost heave). Based upon the soil conditions observed in our borings, the site is underlain by underlain by a thin veneer of topsoil, Quaternary-age old paralic deposits, and Tertiary-age materials of the Santiago Formation. In our opinion the underlying old paralic deposits and Santiago Formation will not be prone to heave or hydro collapse and the topsoils will be removed during the proposed grading operations. In our opinion, no settlement or volume change hazards due to infiltration will apply at the site. SLOPE STABILITY: Infiltration of water has the potential to increase the risk of failure to nearby slopes. The City of Carlsbad BMP Design Manual recommends that infiltration BMPs be set back a distance of at least 1.5 times the height of the adjacent steep slopes (≥25). The setbacks should be measured from the closest horizontal radial distance from the surface edge (at the overflow elevation) of the BMP. Provide this setback is implemented the infiltration of storm water will not contribute to slope instability. The proposed biofiltration basin designated within BMP 1 is located at the top of a steep descending slope, see Plate No. 1. Any BMPs that encroach into the slope setback area (1.5 times the height of the adjacent steep slopes) should be considered restricted for infiltration. In our opinion, infiltrating storm water into BMP 1 will result in slope instability and daylight water seepage. Due to these geotechnical concerns, we recommend that BMP 1 be restricted from infiltration and have an impermeable liner as discussed in the conclusions and recommendations section below. UTILITY CONSIDERATIONS: Utilities are either public or private infrastructure components that include underground pipelines, vaults, and wires/conduit, and above ground wiring and associated structures. Infiltration of water can pose a risk to subsurface utilities, or geotechnical hazards can occur within the utility trenches when water is introduced. Areas of the presently proposed permeable pavers are within existing utility easements. We recommend that infiltration not occur within 10 feet of existing or proposed utility trenches or easements. If the BMPs encroach into this setback distance, vertical cut-off walls or liners could be used to prevent groundwater infiltration into the utility trenches. Therefore, the risk of introducing water into a utility trench may be considered low. CWE 2210558.02 November 2, 2022 Page 6 GROUNDWATER MOUNDING: Groundwater mounding occurs when infiltrated water creates a rise in the groundwater table beneath the facility. Groundwater mounding can affect nearby subterranean structures and utilities. Based on the anticipated soil conditions below the proposed BMP devices, the risk of groundwater mounding below the BMP devices is anticipated to be low. RETAINING WALLS AND FOUNDATIONS: Infiltration of water can result in potential increases in lateral pressures and potential reduction in soil strength. Retaining walls and foundations can be negatively impacted by these changes in soil conditions. This should be taken into account when designing the storm water BMP devices, retaining walls and foundations for the site. The BMP manual recommends BMPs be setback at least 10 feet from foundations or settlement-sensitive improvements. This should be taken into account when designing the storm water BMP devices, retaining walls and foundations for the site. The setback must be measured from the closest horizontal radial distance from the surface edge (at the overflow elevation) of the BMP. If appropriate storm water control measures are implemented, the risk of increased lateral pressure and reduction in soil strength for retaining walls and foundations may be considered low. SOIL AND GROUNDWATER CONTAMINATION: Infiltration should be avoided in areas where infiltration could contribute to the movement or dispersion of soil or groundwater contamination or adversely affect ongoing clean-up efforts, either on site or down-gradient of the project. Based on the information found on http://geotracker.waterboards.ca.gov/, there are no sites with ongoing cleanup efforts located within 100 feet of the proposed BMPs. SEPARATION TO SEASONAL HIGH GROUNDWATER: The depth to seasonal high groundwater beneath the site is expected to fluctuate seasonally and is estimated to be 30 feet below the existing site grades. Based on this information we anticipate that seasonal high groundwater will not encroach within 10 feet of the base of the proposed BMPs. WELLHEAD PROTECTION: Wellheads, natural and man-made, are water resources that may potentially be adversely impacted by storm water infiltration through the introduction of contaminants or alterations in water supply and levels. Infiltration BMP devices must be located at a minimum of 100 feet horizontally from any water supply well. CWE 2210558.02 November 2, 2022 Page 7 CONCLUSIONS AND RECOMMENDATIONS Design infiltration rates within the old paralic deposits which are to support the BMPs were relatively high. However, infiltration restrictions have been identified for BMP 1. The design infiltration rates, mitigation measures, and infiltration restrictions are discussed below.  Design infiltration rates were calculated to be 0.67 inches per hour and 0.43 inches per hour utilizing a default factor of safety (2) and calculated factor of safety (3.13), respectively. The default factor of safety (2) can only be used if the BMP utilizes an underdrain.  The area of the presently proposed tree well (BMP 2) is within the city right-of-way along Buena Vista Circle. BMP 2 will likely encroach within 10 feet of existing utility easements and will be adjacent to the existing street. We recommend that vertical cut-off walls or liners be used along the sidewalls of BMP 2 in order to prevent groundwater infiltration into the nearby pavement section and utility trenches.  The City of Carlsbad BMP Design Manual recommends that infiltration BMPs be set back a distance of at least 1.5 times the height of the adjacent steep slopes (≥25). The setbacks should be measured from the closest horizontal radial distance from the surface edge (at the overflow elevation) of the BMP. The proposed biofiltration basin designated BMP 1 is located at the top of a steep descending slope, see Plate 1. In our opinion, infiltrating storm water into BMP 1 will result in slope instability and daylight water seepage. Due to these geotechnical concerns, we recommend that BMP 1 be restricted from infiltration and have an impermeable liner.  In order to mitigate the risk to acceptable levels, liners and underdrains are recommended in the design and construction of biofiltration basin designated BMP 1. The liners should be impermeable (e.g. High- density polyethylene, HDPE, with a thickness of about 30 mil or equivalent Polyvinyl Chloride, PVC). The underdrains should be perforated within the liner area, installed at the base and above the liner, be at least 3 inches in diameter and consist of Schedule 40 PVC pipe. The underdrains outside of the liner should consist of solid pipe. The penetration of the liners at the underdrains should be properly waterproofed. The underdrains should be connected to a proper outlet. The devices should also be installed in accordance with the manufacturer’s recommendations.  Based on a review of our field study and our experience with similar projects, we anticipate that, as long as the recommendations contained herein are followed, infiltration of storm water utilizing the proposed onsite storm water infiltration BMPs will not result in soil piping, daylight water seepage, or slope instability for the property or project sites down-gradient of the site. CWE 2210558.02 November 2, 2022 Page 8 It should be recognized that routine inspection and maintenance of infiltration basins are necessary to prevent clogging and failure. A maintenance plan should be specified for each BMP by the designer and followed by the owner during the entire lifetime of the BMP device. LIMITATIONS The recommendations and opinions expressed in this report reflect our best estimate of the project requirements based on our limited percolation testing, an evaluation of the subsurface soil conditions encountered at our subsurface exploration locations and the assumption that the infiltration rates and 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, 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. It should be recognized that routine inspection and maintenance of infiltration basins are necessary to prevent clogging and failure. A maintenance plan should be specified for each basin by the designer and followed by the owner during the entire lifetime of the BMP device. It is not our intent to review the civil engineering plans, notes, details, or calculations, when prepared, to verify that the engineer has complied with any particular storm water design standards. It is the responsibility of the designer to properly prepare the storm water plan based on the municipal requirements considering the planned site development and infiltration rates. Respectfully submitted, CHRISTIAN WHEELER ENGINEERING Daniel B. Adler, RCE #36037 David R. Russell, CEG # 2215 DRR:djf:dba ec: jdmartin999@gmail.com; bknapp@plsaengineering.com B-2 B-1 B-4 B-3 B-1 Qop Tsa Tsa QopTsa PT-3 PT-4 PT-1 PT-2 BMP slope setback line (1.5 x Height of adjacent slope) BMP slope setback line (1.5 x Height of adjacent slope) Approximate Boring Location(CWE 2021) Approximate Boring Location(SGC 2000) Approximate Percolation Test Location Old Paralic Deposits overSantiago Formation Santiago Formation Geologic Contact QopTsa CWE LEGEND B-1 B-4 Note: Topsoils Not Mapped Tsa PT-4 DATE: NOVEMBER 2022 BY: SD JOB NO.: 2210558.02 PLATE NO.: 1 SITE PLAN AND GEOTECHNICAL MAP PROPOSED SINGLE-FAMILY RESIDENCELOT 5 OF BUENA VISTA CIRCLECARLSBAD, CALIFORNIA CHRISTIAN WHEELER E N G I N E E R I N G 00 30'60' SCALE: 1" = 30' / • •••• i 449TG(r 1 ., -· :· ~~.: i =2,025SF 1 . (0.046 AC) 'I _ ... •• i···· :/·: • .. i i / ~+ 1· OMA -3 ' .; •• [ I / cJ .· 1{1~1/J:? •• F=,::.~~:•2:c7'...: ·{~i ' ~./ I ATTACHMENT 1A -OMA EXHIBIT MARTIN RESIDENCE -VACANT LOT ON BUENA VISTA CIRCLE CITY OF CARLSBAD PASCO LARET SUITER I ASSOC~A7rlES San Diego I Solana Beach I Orange Coun1y Phone 858.259.8212 lwww.plsaengineering.com • Appendix A Table D.1-1: Considerations for Geotechnical Analysis of Infiltration Restrictions BMP 1 (Biofiltration Basin) BMP 2 (Tree Well) Appendix D: Geotechnical Engineer Analysis Appendix D Geotechnical Engineer Analysis .1 Analysis of Infiltration Restrictions This section is only applicable if the analysis of infiltration restrictions is performed by a licensed engineer practicing in geotechnical engineering. The SWQMP Preparer and Geotechnical Engineer must work collaboratively to identify any infiltration restrictions identified in Table D.1-1 below. Upon completion of this section, the Geotechnical Engineer must characterize each DMA as Restricted or Unrestricted for infiltration and provide adequate support/ discussion in the geotechnical report. A DMA is considered restricted when one or more restrictions exist which cannot be reasonably resolved through site design changes. Table D.1-1: Considerations for Geotechnical Analysis oflnfiltration Restrictions Mandatory Considerations Optional Considerations Result Restriction Element BMP is within 100' of Contaminated Soils BMP is within 100' of Industrial Activities Lacking Source Control BMP is within 100' of Well/ Groundwater Basin BMP is within 50' of Septic Tanks/Leach Fields BMP is within 10' of Structures/Tanks/Walls BMP is within 1 O' of Sewer Utilities BMP is within 10' of Groundwater Table BMP is within Hydric Soils BMP is within Highly Liquefiable Soils and has Connectivity to Structures BMP is within 1.5 Times the Height of Adjacent Steep Slopes (~25%) County Staff has Assigned "Restricted" Infiltration Category BMP is within Predominantly Type D Soil BMP is within 1 O' of Property Line BMP is within Fill Depths of ~5' (Existing or Proposed) BMP is within 10' of Underground Utilities BMP is within 250' of Ephemeral Stream Other (Provide detailed geotechnical support) Based on examination of the best available information, Is Element Applicable? (Yes/No) □ I have not identified any restrictions above. Unrestricted Based on examination of the best available information, D I have identified one or more restrictions above. Restricted Table D.1-1 1s divided into Mandatory Considerations and Optional Considerations. Mandatory D-1 Sept. 2021 Appendix D: Geotechnical Engineer Analysis Appendix D Geotechnical Engineer Analysis .1 Analysis of Infiltration Restrictions This section is only applicable if the analysis of infiltration restrictions is performed by a licensed engineer practicing in geotechnical engineering. The SWQMP Preparer and Geotechnical Engineer must work collaboratively to identify any infiltration restrictions identified in Table D.1-1 below. Upon completion of this section, the Geotechnical Engineer must characterize each DMA as Restricted or Unrestricted for infiltration and provide adequate support/ discussion in the geotechnical report. A DMA is considered restricted when one or more restrictions exist which cannot be reasonably resolved through site design changes. Table D.1-1: Considerations for Geotechnical Analysis oflnfiltration Restrictions Mandatory Considerations Optional Considerations Result Restriction Element BMP is within 100' of Contaminated Soils BMP is within 100' of Industrial Activities Lacking Source Control BMP is within 100' of Well/ Groundwater Basin BMP is within 50' of Septic Tanks/Leach Fields BMP is within 10' of Structures/Tanks/Walls BMP is within 1 O' of Sewer Utilities BMP is within 10' of Groundwater Table BMP is within Hydric Soils BMP is within Highly Liquefiable Soils and has Connectivity to Structures BMP is within 1.5 Times the Height of Adjacent Steep Slopes (~25%) County Staff has Assigned "Restricted" Infiltration Category BMP is within Predominantly Type D Soil BMP is within 1 O' of Property Line BMP is within Fill Depths of ~5' (Existing or Proposed) BMP is within 10' of Underground Utilities BMP is within 250' of Ephemeral Stream Other (Provide detailed geotechnical support) Based on examination of the best available information, Is Element Applicable? (Yes/No) □ I have not identified any restrictions above. Unrestricted Based on examination of the best available information, D I have identified one or more restrictions above. Restricted Table D.1-1 1s divided into Mandatory Considerations and Optional Considerations. Mandatory D-1 Sept. 2021 Appendix B Table D.2-3: Determination of Safety Factor Suitability Assessment (A) Design (B) Appendix D: Approved Infiltration Rate Assessment Methods Table D.2-3: Determination of Safety Factor Infiltration Testing Method 0.25 Soil Texture Class 0.25 Refer to Soil Variability 0.25 Table D.2-4 Depth to Groundwater/Obstruction 0.25 Pretreatment Resiliency Compaction Suitability Assessment Safety Factor, SA = I.p 0.50 0.25 0.25 Refer to Table D.2-4 Design Safety Factor, SB = I.p Safety Factor, S = SAx SB (Must be always greater than or equal to 2) The geotechnical engineer should reference Table D.2-4 below in order to determine appropriate factor values for use in the table above. The values in the table below are subjective in nature and the geotechnical engineer may use professional discretion in how the points are assigned. Table D.2-4: Guidance for Determining Individual Factor Values Infiltration At least 4 tests within BMP Testing Any At least 2 tests of any kind footprint, OR Large/Small Scale Method within 50' ofBMP. Pilot Infiltration Testing over at least 5% of BMP footprint. Soil Texture Unknown, Silty, or Granular/Slightly Loamy Class Clayey Loamy Soil Variability Unknown or High Moderately Homogeneous Significantly Homogeneous Depth to Groundwater/ <5' below BMP 5-15' below BMP > 15' below BMP Obstruction Provides good pretreatment OR Provides excellent pretreatment Pretreatment None/Minimal does not receive significant OR only receives runoff from runoff from unpaved areas rooftops and road surfaces. Includes underdrain/backup Includes underdrain/backup Resiliency None/Minimal drainage that ensures ponding drainage AND supports easy draws down in <96 hours restoration of impacted infiltration rates. Compaction Moderate Likelihood Low Likelihood Very Low Likelihood www.sandiegocounty.gov/ stormwater D-9 Effective September 15, 2020 Appendix C Porchet Method- Percolation to Infiltration Conversion Test # Gravel Adjustment Factor Effective Radius (inches) r Depth of Hole Below Existing Grade (inches) Time Interval (min.) ∆t Height of pipe above surface (feet) Initial Water Depth without correction (feet) Final Water Depth without correction (feet) Initial Water Height with correction (inches) Ho Final Water Height with correction (inches) Hf Change in head (inches) ∆H Average Head Height (inches) Havg Gravel Adjusted Percolation Rate (inch/hour) Tested Infiltration Rate (inch/hour) It PT-1 0.44 4 55 10 0.42 3.53 3.85 17.64 13.80 3.84 15.72 10.14 1.14 PT-2 0.44 4 51 10 0.58 3.77 4.08 12.76 9.04 3.72 10.90 9.82 1.52 PT-3 0.44 4 52 10 0.67 3.74 4.15 15.16 10.24 4.92 12.70 12.99 1.77 PT-4 0.44 4 36 10 2.00 3.96 4.16 12.48 10.08 2.40 11.28 6.34 0.95 1.35 "Initial and final water depth without correction" are measurements taken from top of pipe if pipe is sticking out of ground (most cases) "Initial and final water height with correction" factors in the height of pipe above surface, and provides measurement of water above bottom of pipe If measurements are taken from grade "Height of pipe above surface" = 0 Gravel Adjustment Factor: 4-inch Diameter Pipe: 1.00 - No Gravel Used (No Caving) 3-inch Diameter Pipe: 1.00 - No Gravel Used (No Caving) 0.51 - 3/4 inch gravel with 8 inch diameter hole 0.44 - 3/4 inch gravel with 8 inch diameter hole 0.56 - 3/4 inch gravel with 7 inch diameter hole 0.47 - 3/4 inch gravel with 7 inch diameter hole 0.64 - 3/4 inch gravel with 6 inch diameter hole 0.51 - 3/4 inch gravel with 6 inch diameter hole Porchet Method - Tested Percolation Rate Conversion to Tested Infiltration Rate It = tested infiltration rate, inches per hour ∆H = change in head over the time interval, inches ∆t = time interval, minutes r = effective radius of test hole Havg = average head over the time interval, inches Percolation to Infiltration Rate Conversion (Porchet Method) It = ∆H 60 r ∆t (r+2Havg ) CWE 2210558.02 PROPOSED MARTIN RESIDENCE Average Filed Infiltration Rate Appendix D Subsurface Explorations 0 -- -- -- -- 5-- -- -- -- -- -- -- -- -- 15-- -- -- -- -- -20-- -- -- -- -- 25-- -- -- -- -- 30-- LOG OF TEST BORING B-1 Date Logged: Logged By: Existing Elevation: Proposed Elevation: rJ'J u rJ'J :;:i SM -·: SM : .. ·., .. :,-,•;-~ "l, ~ .... -. :·: .. •-,ti:· m-tr.· SP- SM SC 10/13/21 DJF ±43' ±43' Equipment: Auger Type: Drive Type: Depth to Water: IRA-300 8 inch Hollow Stem 140lbs/30 inches 35' SUMMARY OF SUBSURFACE CONDITIONS (based on Unified Soil Classification System) Topsoil: Dark grayi~h-brown, dry, ve!!Y loose, very fine-to medium-grained, SICTY SAND with rootlFts O1d Paralic Deposits (Qop): Orangish-brown, damp, very dense,vety fine-to medium-grained, SILTY SANp. Orangish-brown to light gray, damp, very dense, very fine-to coarse-grained, SAND with silt and trace gravels, mottled. I J Gravel bed at 10' top•. Santiago Formation (Tsa): White to light yellowish-brown, moist, very dense, fine-to very coarse-grained, CLAYEY SAND with reddish iron staining. Sample Type and Laboratory Test Legend Cal Modified California Sampler SPT Standard Penetration Test ST Shdby Tube MD Max Density S04 Soluble Sulfates SA Sieve Analysis HA Hydrometer SE Sand Equivalent PI Plasticity Index CP Collapse Potential 50/4" Cal 50/6" Cal - 50/5" Cal 50/5" Cal - 50/4" SPT 50/3" Cal 50/3" Cal - 5.2 4.1 8.7 9.3 9.1 CK Chunk DR Drive Ring DS Direct Shear Con Consolidation El Expansion Index R-Val Resistance Value Ch1 Soluble Ch1orides Res pH & Resistivity SD Sample Density l_ll.4 99.8 ~18.4 118.8 114:-3 ISA MD 1S04 OS OS SA Notes: Continues on A-2 * ** Symbol Legend Groundwater Level During Drilling Groundwater Level After Drilling Apparent Seepage No Sample Recovery Non-Representative Blow Count (rocks present) DATE: BY: PROPOSED SINGLE-FAMILY RESIDENCE LOT 5 OF BUENA VISTA CIRCLE CARLSBAD, CALIFORNIA DECEMBER 2021 JOB NO.: 2210558.01 SRO APPENDIX: A-1 " CHRISTIAN WHEELER. ENGINEEIUNG LOG OF TEST BORING B-1 (Cont.) SamI!le Tree and Laborato!)'. Test Legend Date Logged: Logged By: Existing Elevation: Proposed Elevation: g ~ ~ z s 0 g 0 i:Q .... u ~ ::c: E-s 5= E-s ~ ~ rJ'J ~ ~ u ~ rJ'J A ~ ~ 0 30 SC - - . -~ - - - - -- ---35--!' -- -- -- -- 40-- -- -- -- -- 45-- -- -- -- -- so-- -- -- -- -- 55-- -- -- -- -- 60-- Notes: 10/13/21 Equipment: IRA-300 DJF Auger Type: 8 inch Hollow Stem ±43' Drive Type: 140lbs/30 inches ±43' Depth to Water: 35' SUMMARY OF SUBSURFACE CONDITIONS (based on Unified Soil Classification System) Santiago Formation (Tsa): White to light yellowish-brown, moist, very dense, fine-to very coarse-grained, CLAYEY SAND with reddish iron staining. Saturated. GroundJater at 35'. Boring terminated at~:1 eet. Groundwater encountered at 35 J eet. Cal SPT ST MD S04 SA HA SE Pl CP Z-::-0 0 i::.s ~[ tl ; ZS ~ ,tl ~ '-' 50/3" 50/4" 50/3" Symbol Legend PROPOSED SINGLE-FAMILY RESIDENCE LOT 5 OF BUENA VISTA CIRCLE CARLSBAD, CALIFORNIA Modified California Sampler CK Chunk Standard Penetration Test DR Drive Ring ShdbyTube Max Density DS Direct Shear Soluble Sulfates Con Consolidation Sieve Analysis El Expansion Index Hydrometer R-Val Resistance Value Sand Equivalent Chi Soluble Ch1orides Plasticity Index Res pH & Resistivity Collapse Potential SD Sample Density ~ ,-.. z ~ ~ ~ ~~ 0 ;;,.t~ ~~ 0 ~ oZ ~ ~ ~ ii,:: rJ'J (J ~ ~ A~,e, E-s:J~ 0~ ~ .... z A ~,-.. 3~ 0 Oo ~o~ i:Q ~u us:.., Cal 9.6 ~16.0 SD - Cal 13.4 110.~ OS Cal p.7 a 17.4 " Groundwater Level During Drilling Groundwater Level After Drilling Apparent Seepage DATE: DECEMBER 2021 JOB NO.: 2210558.01 CHRISTIAN WHEELER. * ** No Sample Recovery Non-Representative Blow Count (rocks present) BY: ENGINEEIUNG SRO APPENDIX: A-2 I I I I I I I. I. I: 1: l I I Scholl/Buena Vista Circle Project No. 106041 December 21, 1 999 Depth Graphic Sample Blows in Log No. Per Feet Foot 0 ~ -------------------- -I DS-1 63 -I -Bulk 1 I- 5-_L DS·2 I 87 - -I- ~ - -I- 10- -Bs-Y I t--------40/6'' -50/4.5' -I- -I- -L- 15-I- -~ -~ -'- -~ 20-,__ -L- -L- -,__ -~ 25-~ -I- -L- -~ -~ 30 GEOTECHNICAL BORING LOG Dry Water Density Content (pcl) (%) ------·---- 104.9 5.2 108.6 4.4 ---------- F & C Drilling Boring No. 1 Logged by GAR Sampled by GRR 8-inch Hollow Stem Auger Sampler 140 lbs., 30-inch drop uses Soil Geotechnical Description Type TOPSOIL SM @ 0 -18" -Dark brown, dry, medium dense to dense, ---silty fine to medium sand --------------------~--------------------------- SM TERRACE DEPOSITS @ 18" -Dark orange-brown, moist, dense, silty fine to medium sand; with occasional gravel I- I- - I- I- .... .... - 1-- I- --------------------------------------------------- SM SANTIAGO FORMATION I- @ 10.5' -Yellow-brown, moist, dense, silty medium to ~ coarse sand .... I- Total depth = 11 . 5 feet No groundwater encountered I- No refusal I- Backfilled on 12/21 /99 I- I- ~ .... ~ I- ~ .... I- ,__ .... .... I- .... SGC I I I I I I I .I I. I I I. I I I I I I I Scholl/Buena Vista Circle Pro ject No.106D41 December 21 , 1999 Depth Graphic Sample Blows in Per Feet Log No. Foot 0 -- -------DST ■ -50/4'' -I - Bulk 1 -I ,_ 5 -I DS-2 33/6" -43/4" -- -- -- 10--~~-~-1 45/6" --------~3J1"_ -- -I- 15-,_ -- -,-- -- -- 20 -,_ -,_ -,_ -I- -,-- 25 -,.._ -,_ -,_ -,-- -- 30 GEOTECHNICAL BORING LO G Dry Water Density Content (pct) (%) -------4-:a -92.4 108.3 3.8 ---------- F & C Drilling Boring No. 2 Logged by GRR Sampled by GRR 8-inch Hollow Stem Auger Sampler 140 lbs ., 30-inch drop uses Soil Geotechnical De scription Type ' SM TOPSOIL @ 0 - 2 ' -Dark brown, dry, loose, silty fine to medium - sand; with rootlets ---------------------------------------------------- SM-SP TERRACE DEPOSITS @ 2' -Orange-brown, dry to moist , dense, slightly silty - f ine to medium sand; micaceous; with occasional - gravel ~ '-- - - - - ---------------------------------------------------- SM-SP SANTIAGO FORMATION @ 11' -Yellow-brown, moist, very dense, silty medium '-- to coarse sand '-- Total depth = 13 feet - No groundw ater encountered No refusal - Backfilled on 12/21/99 - - - '-- ,_ ~ '-- - - - '-- '-- - - SGC I I I I I I I I I I I 1: Scholl/Buena Vista Circle Project No. 106D41 December 21, 1 999 Depth Graphic Sample Blows in Log No. Per Feet Foo t 0 ------------------ -- -- -- 5-I DS-1 36 - -- -- -- 10- -155.2-1 -------2-576"--50/5.5" -,- -- 15-..... -- -- -- -..... 20-- -..... -- -- -- 25 -..... -..... -..... -- -- 30 GEOTECHNICAL BORING LOG Dry Water Density Content (pcf) (%) ---------- 109.8 3.7 -,-2ci:-o--11.4- F & C Drilling Boring No. 3 Logged by GRR Sampled by GRR 3-inch Hollow Stem Auger Sampler 140 lbs., 30-inch drop uses Soil Geotechnical Description Type SM TOPSOIL ' @ 0 -8" -Dark brown, dry, medium dense, silty fine to ' - ' ' ' medium sand; with rootlets ' ----------------------------------------------- SM-SP TERRACE DEPOSITS @ 8" -Orange-brown, moist to wet, medium dense, - slightly silty fine to medium sand; micaceous - ~ ~ @ 7' -Gravel layer ... ... @ 9' -Gravel layer ... - --------------------------------------------------- SC SANTIAGO FORMATION - @ 10.5' -Yellow-green, moist, very dense, clayey fine to coarse sand ... Tot al depth = 13 feet No groundwater encountered ... No refusal L- Backfilled on 12/21 /99 ... ... - ... ..... ~ ... ... - - ... ... ... - SGC I I I I I I I I: ll Scholl/Buena Vista Circle Project No. 106 D4 1 December 21, 1999 Depth Graphic Sample Blows in Log No. Per feet Foot 0 -- ------------------ -- --- 5-I -DS-1 49 -- -- -- 10-I DS-2 64 - -- -- ------I------I 15-Bur 1 I -DS-3 94 -- -- 20-- -- -- -- -- 25-- -I- -- -I- -- 30 GEOTECHNICAL BORING LOG Dry Water Density Content lpcf) (%) ---------- 105.6 3.9 108.2 6.7 ---------- 110. 5 11.2 F & C Drilling Boring No. 4 Logged by GRR Sampled by GRR 8-inch Hollow Stem Auger Sampler 140 lbs., 30-inch drop -uses Soil Geotechnical Description Type SM TOPSOIL @ 0 -2' -Dark brown, dry, medium dense, silty fine to - medium sand; with rootlets ---------------------------------------------------- SM-SP TERRACE DEPOSITS @ 2' -Orange-b.rown, inoist, medium dense, silty fine to - medium sand; micaceous - L- ~ '- >-- - - - - @ 13' -Gravel layer '- ---------------------------------------------------- SC SANTIAGO FORMATION @ 14' -Yellow-green, moist, very dense, clayey fine to - coarse sand - Total depth = 17 feet -No groundwater encountered No refusal >-- Backfilled on 12/21/99 ~ ~ - >-- - - ~ - - SGC Appendix E Natural Resources Conservation Service (NRCS) Web Soil Survey Hydrologic Soil Group Map Hydrologic Soil Group—San Diego County Area, California (Buena Vista Circle) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/12/2022 Page 1 of 4 36 6 9 7 3 0 36 6 9 7 9 0 36 6 9 8 5 0 36 6 9 9 1 0 36 6 9 9 7 0 36 7 0 0 3 0 36 6 9 6 7 0 36 6 9 7 3 0 36 6 9 7 9 0 36 6 9 8 5 0 36 6 9 9 1 0 36 6 9 9 7 0 36 7 0 0 3 0 466990 467050 467110 467170 467230 467290 467350 467410 467470 467530 466990 467050 467110 467170 467230 467290 467350 467410 467470 467530 33° 10' 7'' N 11 7 ° 2 1 ' 1 4 ' ' W 33° 10' 7'' N 11 7 ° 2 0 ' 5 3 ' ' W 33° 9' 55'' N 11 7 ° 2 1 ' 1 4 ' ' W 33° 9' 55'' N 11 7 ° 2 0 ' 5 3 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84 0 100 200 400 600Feet 0 35 70 140 210Meters Map Scale: 1:2,590 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. USDA = MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: San Diego County Area, California Survey Area Data: Version 16, Sep 13, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Mar 14, 2022—Mar 17, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—San Diego County Area, California (Buena Vista Circle) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/12/2022 Page 2 of 4USDA = □ D D D D D D D D ,,..,,,. ,,..,,,. □ ■ ■ □ □ ,,..._., t-+-t ~ tllWI ,..,,. ~ • Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI LG-W Lagoon water 14.1 43.9% MlC Marina loamy coarse sand, 2 to 9 percent slopes B 14.7 45.6% TeF Terrace escarpments 3.4 10.5% Totals for Area of Interest 32.2 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—San Diego County Area, California Buena Vista Circle Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/12/2022 Page 3 of 4USDA = Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—San Diego County Area, California Buena Vista Circle Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/12/2022 Page 4 of 4~