SUBJECT: Percolation Test Letter Report New Public

550 West Locust AvenueFresno CA 93650P 559.497.2880F 559.497.2886www.bskassociates.com

Environmental, Geotechnical, Construction Services, Analytical Testing - An Employee-Owned Company

Sent via email: [email protected] Project G20-134-10F

July 21, 2020

Mr. Jose Lemus, PELane Engineers, Inc.979 North Blackstone StreetTulare, CA 93274

SUBJECT: Percolation Test Letter ReportNew Public RestroomMefford Field AirportCity of TulareTulare, California

Dear Mr. Lemus:

This report presents the results of Percolation Testing conducted by BSK Associates (BSK), at theMefford Field Airport in Tulare, California on the Site Vicinity Map, Figure 1. BSK’s scope of servicesincluded a site reconnaissance, field exploration and preparation of this letter. The geotechnicalengineering investigation was conducted in accordance with BSK Proposal GF20-20209, dated May 29,2020.

PROJECT DESCRIPTIONBSK understands that the project consists of a new public restroom with a 1,000-gallon septic tank and a200-foot long leach line in Tulare, California.

In the event that significant changes occur in the design or location of the proposed improvements, thisreport’s conclusions and recommendations will not be considered valid unless the changes are reviewedwith BSK and the conclusions and recommendations are modified or verified in writing.

FIELD INVESTIGATION

The field exploration for this investigation was conducted under the oversight of a BSK geotechnicalengineer on July 15, 2020. Five (5) borings were drilled to depths of 5 to 10 feet bgs with hand augerequipment in which percolation test tubes were placed and surrounded by pea gravel and presoaked for24 hours before testing. The percolation test holes were backfilled with the gravel and soil cuttings aftertest completion.

Percolation Test Letter Report BSK Project G20-134-10FMefford Field Airport – New Restroom July 21, 2020Tulare, California Page 2

A total of three (3) percolation tests were conducted. The percolation test locations can be found onFigure 3, Percolation Test Location Map. The last three rates from the slowest percolation test areaveraged to calculate the percolation rates. The results of the percolation tests are presented on FiguresA-1 through A-3 and in Table 1 below.

BSK recommends a factor of safety of at least 3 when applying percolation rates to the design of thesystem.

SITE CONDITIONS

The following sections address the site descriptions and surface conditions, subsurface conditions, andgroundwater conditions at the Site. This information is based on BSK’s field exploration and publishedmaps and reports.

Site Description and Surface Conditions

At the time of the field exploration, the site was covered in dry vegetation. The project site was boundedby the airport on all sides and Leonard Noel Drive on the southwest side of the site. The site is located inthe southwest quarter of the southwest quarter of Section 25, Township 20 South, Range 24 East of theMount Diablo Meridian. WGS84 GPS coordinates for the center of the site are 36.1550 degrees Northlatitude and 119.3282 degrees West longitude.

Subsurface Conditions

Based on our soil boring data the site generally consisted of silty sand in the upper 3 feet bgs underlainby poorly graded sand with silt to the maximum explored depth of 5 to 10 feet bgs in the planned leachfield area and sandy lean clay to 10 feet bgs in the planned restroom area.

The boring logs in Appendix A provide a more detailed description of the materials encountered,including the applicable Unified Soil Classification System symbols.

Table 1: Summary of Percolation Test Results

TestLocation

Approximate Depth atBottom of Hole (ft)

Soil DescriptionPercolation Rate(minutes/inch)

PT-1 5 Poorly Graded Sand w/ Silt 3.75




Groundwater Conditions

Groundwater was not encountered in the borings. The California Department of Water Resourcesindicates the historical depth to groundwater is approximately 42 bgs in the vicinity of the site.However, fluctuations in the groundwater level or the presence of perched groundwater may occur dueto variations in rainfall, irrigation, seasonal factors, pumping from wells and other factors that were notevident at the time of our investigation. Groundwater is not anticipated to affect design or constructionof the proposed improvements.

LIMITATIONS

The analyses and recommendations submitted in this report are based upon the data obtained from theborings performed at the locations shown on the Boring & Perc Test Location Map, Figure 2. The reportdoes not reflect variations which may occur between or beyond the borings. The nature and extent ofsuch variations may not become evident until construction is initiated. If variations then appear, a re-evaluation of the recommendations of this report will be necessary after performing on-Siteobservations during the excavation period and noting the characteristics of the variations.

The validity of the recommendations contained in this report is also dependent upon an adequatetesting and observation program during the construction phase. BSK assumes no responsibility forconstruction compliance with the design concepts or recommendations unless it has been retained toperform the testing and observation services during construction as described above.

The findings of this report are valid as of the present. However, changes in the conditions of the Site canoccur with the passage of time, whether caused by natural processes or the work of man, on thisproperty or adjacent property. In addition, changes in applicable or appropriate standards may occur,whether they result from legislation, governmental policy or the broadening of knowledge.

BSK has prepared this report for the exclusive use of the Client and members of the project design team.The report has been prepared in accordance with generally accepted geotechnical engineering practiceswhich existed in Tulare County at the time the report was written. No other warranties either expressedor implied are made as to the professional advice provided under the terms of BSK’s agreement withClient and included in this report.


CLOSINGBSK appreciates the opportunity to be of service to you on this project. If you have any questions, orwould like additional information, please call us at (559) 497-2880.

Respectfully submitted,BSK ASSOCIATES

Corinne Goodwin, PE On Man Lau, PE, GEProject Engineer South Valley Regional Manager

Attachments:

FiguresFigure 1: Site Vicinity MapFigure 2: Boring & Perc Test Location Map

Appendix A: Field ExplorationFigure A-1: Soil Classification Chart and Log KeyBoring Logs: Borings B-1, B-2, PT-1, PT-2, and PT-3Figure A-1: Percolation Test P-1Figure A-2: Percolation Test P-2Figure A-3: Percolation Test P-3

FIGURES

REFERENCE IMAGE: USGS Topo

550 W Locust AvenueFresno, CA 93650

Tel. (559) 497-2880

SITE VICINITY MAP

Mefford Field Airport—New RestroomTulare, California

FIGURE 1JOB NO. G20-120-10F_____DATE _July 2020 ___

DR. BY CG___ CH. BY __OML__SCALE AS SHOWN

SHEET NO. _1__OF _2__ SHEETS

SITE

0 0.37 mi 0.74 miScale: 1” = 0.74 mi(APPROXIMATE)

REFERENCE IMAGE: Coldwell & Google Earth 2020

550 W Locust AveFresno, CA 93650

Tel. (559) 497-2880

BORING AND PERC TEST LOCATION MAP

Mefford Field Airport New RestroomTulare, California

FIGURE 2JOB NO. G20-134-10F___DATE _July 2020 ____

DR. BY CG___ CH. BY __OML__SCALE AS SHOWN

SHEET NO. _2__OF _2__ SHEETS

0 16’ 28’Scale: 1” = 28’

(APPROXIMATE)

LEGEND:

APPROXIMATE BORING OR PERCOLATION TEST LOCATIONSB-1

B-2

PT-3B-1

PT-1PT-2

APPENDIX A

FIELD EXPLORATION

APPENDIX AFIELD EXPLORATION

The field exploration for this investigation was conducted under the oversight of a BSK Engineer. Two(2) borings were drilled at the Site on July 14, 2020, using a hand auger equipment. The borings werecompleted to depths of approximately 6 to 12.5 feet beneath the existing ground surface (bgs).

The soil materials encountered in the test borings were visually classified in the field, and the logs wererecorded during the drilling and sampling operations. Visual classification of the materials encounteredin the test borings was made in general accordance with the Unified Soil Classification System (ASTM D2488). A soil classification chart is presented herein. Boring logs are presented herein and should beconsulted for more details concerning subsurface conditions. Stratification lines were approximated bythe field staff based on observations made at the time of drilling, while the actual boundaries betweensoil types may be gradual and soil conditions may vary at other locations.

Subsurface samples were obtained at the successive depths shown on the boring logs by drivingsamplers which consisted of a 2.5-inch inside diameter (I.D.) California Sampler. The relativelyundisturbed soil core samples were capped at both ends to preserve the samples at their naturalmoisture content. At the completion of the field exploration, the test borings were backfilled with theexcavated soil cuttings.

MAJOR DIVISIONS TYPICAL NAMESCO

ARSE

GRAI

NED

SOIL

SM

ore

than

Hal

f>#2

00GRAVELS

MORE THAN HALFCOARSE FRACTION

IS LARGER THANNO. 4 SIEVE

CLEAN GRAVELSWITH LITTLE ORNO FINES

GW WELL GRADED GRAVELS, GRAVEL-SAND MIXTURES

GP POORLY GRADED GRAVELS, GRAVEL- SAND MIXTURES

GRAVELS WITHOVER 15% FINES

GM SILTY GRAVELS, POORLY GRADED GRAVEL-SAND-SILT MIXTURES

GC CLAYEY GRAVELS, POORLY GRADED GRAVEL-SAND-CLAY MIXTURES

SANDS

MORE THAN HALFCOARSE FRACTIONIS SMALLER THAN

NO. 4 SIEVE

CLEAN SANDSWITH LITTLEOR NO FINES

SW WELL GRADED SANDS, GRAVELLY SANDS

SP POORLY GRADED SANDS, GRAVELLY SANDS

SANDS WITHOVER 15% FINES

SM SILTY SANDS, POORLY GRADED SAND-SILT MIXTURES

SC CLAYEY SANDS, POORLY GRADED SAND-CLAY MIXTURES

FINE

GRAI

NED

SOIL

SM

ore

than

Hal

f<#2

00si

eve SILTS AND CLAYS

LIQUID LIMIT LESS THAN 50

ML INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY ORCLAYEY FINE SANDS, OR CLAYEY SILTS WITH SLIGHT PLASTICITY

CLINORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS,SANDY CLAYS, SILTY CLAYS,LEAN CLAYS

OL ORGANIC CLAYS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY

SILTS AND CLAYS

LIQUID LIMIT GREATER THAN 50

MH INORGANIC SILTS , MICACEOUS OR DIATOMACIOUS FINE SANDY ORSILTY SOILS, ELASTIC SILTS

CH INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS

OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS

HIGHLY ORGANIC SOILS Pt PEAT AND OTHER HIGHLY ORGANIC SOILS

Note: Dual symbols are used to indicate borderline soil classifications.

Pushed Shelby Tube Water Level measured at time of Drilling(with date noted)

Standard Penetration Test(2-inch outside diameter)

Water Level measured after Drilling(with date noted)

Modified California(3-inch outside diameter) Hand Auger Cuttings

Split Barrel Sampler(2 ½-inch outside diameter) Grab Sample

Undisturbed Sample Sample Attempt with No Recovery

Continuous Core Sample

SOIL CLASSIFICATION CHART AND LOG KEYUnified Soil Classification System (ASTM D 2487)

Figure A1

easy augering

easy augering

Silty SAND: brown, moist, fine to medium grained sand

Poorly Graded SAND w/ SILT: brown, moist, fine tocoarse grained sand

Boring terminated at approximately 10 feet bgs.Groundwater was not encountered.Boring backfilled with soil cuttings.

SM

SP-SM

Project: Mefford Field Airport New Restroom

Location: Tulare, CA

Project No.: G2013410F

Logged By: J. Leu

Checked By: O. Lau

Page 1 of 1S

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REMARKSMATERIAL DESCRIPTION

Boring: B-1In

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BSK Associates550 W Locust AveFresno, CA 93650Telephone: 559.497.2880Fax: 559.497.2886

US

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* See key sheet for symbols and abbreviations used above.

Drilling Contractor: BSKDrilling Method: Hand AugerDrilling Equipment: Hand AugerDate Started: 7/15/20Date Completed: 7/15/20

Surface Elevation: Sample Method: 2.5" I.D. Cal ModGroundwater Depth: Not EncounteredCompletion Depth: 10 FeetBorehole Diameter: 4"

Sandy CLAY: brown, moist, fine to medium grained sand

Lean CLAY: brown, moist, trace fine to medium grainedsand

Boring terminated at approximately 10 feet bgs.Groundwater was not encountered.Boring backfilled with soil cuttings.

CL

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Logged By: J. Leu

Checked By: O. Lau

Page 1 of 1S

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Boring: B-2In

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Boring terminated at approximately 5 feet bgs.Groundwater was not encountered.Boring backfilled with soil cuttings and gravel.

SM

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Logged By: J. Leu

Checked By: O. Lau

Page 1 of 1S

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1

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Logged By: J. Leu

Checked By: O. Lau

Page 1 of 1S

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Logged By: J. Leu

Checked By: O. Lau

Page 1 of 1S

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Boring: PT-3In

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Mefford Field Airport - New Restroom Project No.: G20-134-10FTulare, CA Pit No.: PT-1

A. Gravel Layer Depth, in. 3B. Total Gravel Thickness, in. 10

C. Distance from Shelf, ft. N/AD. Hole Diameter, in. 4E. Case Diameter, in. 2.5F. Reference Depth, in. 67G Hole Depth, in. 58

Depth to Groundwater N/ASoil Type:

Date & Time Saturated:Depth of Water after 24-hour Saturation: No water remaining

7:03:00 3.33 40.0 X 7:06:00 4.83 58.0 3.00 18.0 0.287:44:00 3.94 47.3 X 7:47:00 4.32 51.8 3.00 4.6 1.097:56:00 3.94 47.3 X 7:59:00 5.27 63.2 3.00 16.0 0.318:00:00 3.92 47.0 X 8:03:00 4.16 49.9 3.00 2.9 1.728:06:00 0.70 8.4 X 8:09:00 0.88 10.6 3.00 2.2 2.308:12:00 0.70 8.4 X 8:27:00 1.29 15.5 15.00 7.1 3.518:28:00 0.70 8.4 X 8:43:00 1.24 14.9 15.00 6.5 3.838:44:00 0.70 8.4 X 8:59:00 1.24 14.9 15.00 6.5 3.519:00:00 0.70 8.4 X 9:15:00 1.20 14.4 15.00 6.0 3.839:16:00 0.70 8.4 X 9:31:00 1.19 14.3 15.00 5.9 3.839:32:00 0.70 8.4 X 10:02:00 1.64 19.7 30.00 11.3 3.83

Average (last 4 readings) = 3.75*Depth below reference datum**Corrected for full depth gravel in annulus

Final Depth toWater*, in.

Test Duration,min.

Initial Depthto Water (ft)

7/15/20 10:20 AM

Project Name:Project Location:

Begin Test Initial Depth toWater*, in. Refilled End Test

FinalDepth toWater (ft)

550 W. Locust Ave.FIGURE A-1

Water Drop, in. Drop Ratemin./in.**

Fax: (559) 497-2886Ph: (559) 497-2868Fresno, CA 93650PERCOLATION TEST DATA SHEET

Poorly Graded SAND w/ SILT (SP-SM)C D

AB

F

G

E

550 W. Locust Ave.Fresno, CA 93650

Ph: (559) 497-2868Fax: (559) 497-2886






10:12 3.50 42.0 X 10:13 5.09 61.1 1.0 19.1 0.0910:16 4.20 50.4 X 10:17 4.55 54.6 1.0 4.2 0.3910:21 4.13 49.6 X 10:22 5.06 60.7 1.0 11.2 0.1510:24 3.80 45.6 X 10:25 5.04 60.5 1.0 14.9 0.1110:27 4.62 55.4 X 10:28 5.02 60.2 1.0 4.8 0.3410:35 4.40 52.8 X 10:36 5.21 62.5 1.0 9.7 0.17


Initial Depthto Water (ft)

Final Depthto Water (ft)


PERCOLATION TEST DATA SHEET

Drop Ratemin./in.**Begin Test Initial Depth to

Water*, in. Refilled End Test Final Depth toWater*, in.

Test Duration,min. Water Drop, in.

FIGURE A-2

Poorly Graded SAND w/ SILT (SP-SM)

7/15/20 10:55 AM

C D

AB

F

G

E

550 W. Locust Ave.Fresno, CA 93650

Ph: (559) 497-2868Fax: (559) 497-2886






10:42 4.19 50.3 X 10:43:00 5.00 60.0 1.00 9.7 0.1710:46 3.80 45.6 X 10:47:00 5.14 61.7 1.00 16.1 0.1010:50 2.81 33.7 X 10:51:00 4.05 48.6 1.00 14.9 0.1110:52 3.82 45.8 X 10:53:00 4.96 59.5 1.00 13.7 0.1210:57 3.70 44.4 X 10:58:00 4.8 57.6 1.00 13.2 0.1311:00 2.43 29.2 X 11:01:00 3.97 47.6 1.00 18.5 0.0911:05 3.68 44.2 X 11:06:00 4.48 53.8 1.00 9.6 0.1711:08 2.26 27.1 X 11:09:00 3.60 43.2 1.00 16.1 0.10


Test Duration,min. Water Drop, in. Drop Rate

min./in.**

PERCOLATION TEST DATA SHEETFIGURE A-3


Poorly Graded SAND w/ SILT (SP-SM)

Begin Test Initial Depth toWater*, in. Refilled End Test Final Depth to

Water*, in.Initial Depth to

Water (ft)Final Depth to

Water (ft)

7/15/20 11:30 AM

C D

AB

F

G

E

Documents

SUBJECT: Percolation Test Letter Report New Public