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Home My WebLink AboutSW3231001_Soils/Geotechnical Report_20231219 November 15, 2022 SU NI NI IT Mr. Douglas Alles ENGINEERING • LABORATORY•TESTING DRB Group A Universal Engineering Sciences Company 227 West Trade Street, Suite 100 Charlotte, NC 28202 Email: Garrison@trunorthhomes.com Subject: Estimated Seasonal High Water Table (ESHWT) Determinations Hemby Bridge Site Hemby Bridge Road Union County, North Carolina SUMMIT Project No. 5879.G0012.CO1 Dear Mr. Alles: SUMMIT Engineering, Laboratory and Testing, Inc. (SUMMIT) is pleased to submit this letter summarizing our observations of the soil test borings as related to Estimated Seasonal High Water Table Elevation (ESHWT) determinations in the proposed stormwater BMP ponds to be constructed for the proposed project listed above. This report contains a brief description of the project information provided to us, general site and subsurface conditions revealed during this exploration. PURPOSE OF EXPLORATION The primary purpose of this exploration was to obtain information regarding the subsurface conditions in the proposed stormwater BMP pond, assess the engineering characteristics of the subsurface materials, and determination of the estimated seasonal high water table mark (if evident). This report contains the following items: • Site Vicinity Map and Boring Location Plan, • Summary of Test Boring Observations, visual soil classifications and descriptions, 3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com Summary of ESHWT Determinations SUMMIT Project No. 5879.00012.COI Hemby Bridge Site November 15,2022 • A general review of the subsurface soils and estimated seasonal high water table depth from existing ground surface (if evident), • Groundwater level measurements. EXPLORATION PROCEDURES SUMMIT visited the site on October 31, 2022 and performed two (2) soil test borings (identified as SW-1 and SW-2) in the proposed stormwater BMP pond. The approximate location of the borings is shown on Figure 2 — "Boring Location Plan" provided in Appendix 2. The client (DRB Group) provided SUMMIT an untitled plan sheet that indicated the approximate locations of the proposed stormwater BMP pond. The borings were staked by the client prior to drilling. The soil test borings were performed using a track 7822 DT Geoprobe drill rig. Borings SW-1 and SW-2 were extended to approximate depths of 9.7 and 14.6 feet below the existing ground surface, respectively. Hollow-stem, continuous flight auger drilling techniques were used to advance the boring into the ground. Standard Penetration Tests (SPT)were performed within the mechanical boring continuously to the termination depth in general accordance with ASTM D 1586. When properly evaluated, the SPT results can be used as an index for estimating soil strength and density. In conjunction with the penetration testing, representative soil samples were obtained from the test location and returned to our laboratory for visual classification and potential laboratory testing. The soil samples collected were visually examined and classified in general accordance with ASTM D-2488. The Munsell Soil Color Charts (2009 Revision) were used to identify the hue, value, and chroma of soil samples. Water level measurements were attempted at the termination of drilling. The classification symbols are depicted on the "Boring Log" provided in Appendix 2. GENERALIZED SUBSURFACE STRATIGRAPHY General subsurface conditions observed during our geotechnical exploration are described herein. For more detailed soil descriptions and stratifications at the test location, the respective "Boring Log" provided in Appendix 2 should be reviewed. The horizontal stratification lines designating the interface between various strata represents approximate boundaries. 3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com Summary of ESHWT Determinations SUMMIT Project No. 5879.G0012.CO1 Hemby Bridge Site November 15,2022 Transitions between different strata in the field may be gradual in both the horizontal and vertical directions. Beginning from the ground surface, a layer of topsoil (surficial organic soils) was observed with a thickness of approximately 3 inches. Beneath the topsoil layer, residual (undisturbed) soils were encountered that consisted of sandy silts (ML). Partially weathered rock (PWR) conditions were encountered in Borings SW-1 and SW-2 at approximate depths of 4 and 8 feet below the existing ground surface (bgs), respectively. Auger refusal conditions were in encountered in Borings SW- 1 and SW-1 at approximate depths of 9.7 and 14.6 feet bgs, respectively. GROUNDWATER LEVEL MEASUREMENTS At the time of drilling, groundwater was not observed in the borings. After waiting more than 24 hours, water was not observed in the borings. It should also be noted that groundwater levels tend to fluctuate with seasonal and climatic variations, as well as with some types of construction operations. Therefore, water may be encountered during construction at depths not indicated in the borings performed for this exploration. ESTIMATED SEASONAL HIGH WATER TABLE ESHWT is defined as the shallowest depth to a wet soil layer as a result of"true" or "permanent" groundwater at any time during the year. The ESHWT is typically identified with a change in the color of the soil layer due to water staining (typically, gray redoximorphic depletions and mottling). Spots or blotches of different color or shades of color interspersed with a dominant color in soil, commonly referred to as mottling. Mottling is a historic indication for the presence of groundwater caused by intermittent periods of saturation and drying, and may be indicative of poor aeration and impeded drainage. Mottling is a "general indication of groundwater" flow through this layer, but it is not known whether the groundwater flow was recent. 3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com Summary of ESHWT Determinations SUMMIT Project No. 5879.00012.COI Hemby Bridge Site November 15,2022 CONCLUSIONS Based on our observations, ESHWT indicators were not evident in soils sampled in Borings SW-1 and SW-2. Please note that even though ESHWT indicators were not evident in Borings SW-1 and SW-2, perched water conditions can develop above a low permeable material such as partially weathered rock (PWR). Perched water conditions differ from the "true" or "permanent" water table. A perched water table is water standing above an unsaturated zone and is often influenced by soil conditions, and occurrence of less permeable soils. Where the ESHWT is defined as the shallowest depth to a wet soil layer as a result of"true" or"permanent"groundwater at any time during the year. The BMP designer should take into consideration that perched water conditions may exist above the low permeable PWR stratum. The following table summarizes the results of the borings and our observations. Summary Table of the Boring Results and Our Observations Approx. GW Depth Approx. Auger Boring ESHWT GW Depth After PWR Refusal Test Depth Depth ATD 24 Hours Depth Depth Location (Feet)1 (Feet)1 (Feet)1 (Feet)1 (Feet)1 (Feet)1 SW-1 9.7 NE NE NE 4 9.7 SW-2 14.6 NE NE NE 8 14.6 1 Depths from existing ground surface. NE — Not Encountered in boring The analyses submitted in this report were based, in part, on data obtained from this exploration. If the above-described project conditions are incorrect or changed after the issuing of this report, or subsurface conditions encountered during construction are different from those reported, SUMMIT should be notified and these recommendations should be re-evaluated based on the changed conditions to make appropriate revisions. We have prepared this report according to generally accepted geotechnical engineering practices. No warranty, express or implied, is made as to the professional advice included in this report. 3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com Summary of ESHWT Determinations SUMMIT Project No. 5879.G0012.CO1 Hemby Bridge Site November 15,2022 CLOSING SUMMIT appreciates the opportunity to provide our professional services for you on this project. If you have any questions concerning the information in this proposal or if we may be of further service, please contact us at 704.504.1717. Sincerely, SUMMIT ENGINEERING, LABORATORY&TESTING, INC. QUO �iq•.9• �� rsQ. • �/� SEAL = ; 052284 E SUMMIT ▪ a c� e =m : Engineering,Laboratory : oz ▪ tL/L5/2o22 _ • &Testing,Inc. l FHGINE�� ., � • i • No.F-1454 • ^Q- 13,t%�rL CaQQ L. Brian Cantrell, P.E. Christian Payne Geotechnical Dept. Manager Assistant Project Manager LIST OF APPENDICES Appendix 1 Figure No. 1—Site Vicinity Map Figure No. 2— Boring Location Plan Appendix 2 Boring Logs 3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com Summary of ESHWT Determinations SUMMIT Project No. 5879.G0012.CO1 Hemby Bridge Site November 15,2022 SUMMIT ENGINEERING • LABORATORY • TESTING A Universal Engineering Sciences Company APPENDIX 1 Figures 3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com gra Hair Original Salon Studio 9 Gie Alcon Painting9 SITE 1522 { Hemby Bridge Site Figure 1 Hemby Bridge Road Site Location Plan Union County, North Carolina SUMRMIT •TESTING A Univ.rsai Engineering Sciences Company 3575 Centre Circle SUMMIT Project No.: 5879.G0012.CO1 Fortivtil(803) 0 a1717a29715 SCALE: NTS �Ao3>so4-1717 % At ''' - � ' • • . - ....5 i II i i N 0 r A. k 171 i t -ii ; it,1?4,.: '1.1.1111114641/21...rill.-*- API - 4. 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TOP SAND = 636. 00 ia BOTTOM OF SAND=633. 5O , s, 0 i END BORING A T 630. 00 1 Figure 2 Hemby Bridge Site /A Boring Location Plan Hemby Bridge Road SUMMIT Union County, North Carolina 4 Approx. Soil Test Boring Location A, ,,an,, „ 3575 Centre Circle SUMMIT Project No.: 5879.G0012.CO1 Fort Mill,South Carolina 29715 SCALE: NTS 1 (803)504-1717 Summary of ESHWT Determinations SUMMIT Project No. 5879.G0012.CO1 Hemby Bridge Site November 15,2022 SUMMIT ENGINEERING • LABORATORY • TESTING A Universal Engineering Sciences Company APPENDIX 2 Boring Logs 3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com SUMMIT ENGINEERING KEY TO SYMBOLS /MEL 3575 CENTRE CIRCLE FORT MILL,SC 29715 SUMMIT 704-504-1717 CPAYNE@SUMMIT-COMPANIES.COM CLIENT DRB Group PROJECT NAME Hemby Bridge Site PROJECT NUMBER 5879.G0012 PROJECT LOCATION Union County, North Carolina LITHOLOGIC SYMBOLS SAMPLER SYMBOLS (Unified Soil Classification System) Standard Penetration Test BLANK CH: USCS High Plasticity Clay j� CL: USCS Low Plasticity Clay I FILL: Fill (made ground) Iffi MH: USCS Elastic Silt ML: USCS Silt MLS: USCS Sandy Silt WELL CONSTRUCTION SYMBOLS SM: USCS Silty Sand TOPSOIL: Topsoil PWR: Partially Weathered Rock ABBREVIATIONS LL -LIQUID LIMIT(%) TV -TORVANE PI -PLASTIC INDEX(%) PID -PHOTOIONIZATION DETECTOR W -MOISTURE CONTENT(%) UC -UNCONFINED COMPRESSION DD -DRY DENSITY(PCF) ppm -PARTS PER MILLION NP -NON PLASTIC v, Water Level at Time -200 -PERCENT PASSING NO. 200 SIEVE Drilling, or as Shown PP -POCKET PENETROMETER(TSF) Water Level at End of 1 Drilling, or as Shown w Water Level After 24 Hours, or as Shown / SUMMIT ENGINEERING, LABORATORY 8c TESTING,INC. BORING NUMBER SW-1 3575 CENTRE CIRCLE - FORT MILL,SOUTH CAROLINA PAGE 1 OF 1 SUMMIT TELEPHONE: 704-504-1717 A..".e,e..�a„n=..=amp. SUMMIT-COMPANIES.COM CLIENT DRB Group PROJECT NAME Hemby Bridge ESHWT PROJECT NUMBER 5879.G0012 PROJECT LOCATION Union County, North Carolina DATE STARTED 10/31/22 COMPLETED 10/31/22 GROUND ELEVATION 639.31 ft HOLE SIZE 6 inches DRILLING CONTRACTOR SUMMIT GROUND WATER/CAVE-IN: DRILLING METHOD Hollow Stem Auger AT TIME OF DRILLING ---GW NE ATD LOGGED BY A. Boer CHECKED BY C.Payne AT END OF DRILLING ---GW NE>24 hrs NOTES See Figure 2"Boring Location Plan"for Approx. Boring Location AFTER DRILLING --- w o A SPT N VALUE A 0 U >-ct >- cow 0 20 40 60 80 100 _ I—w CC^ Hn It Q ,..,1- O MATERIAL DESCRIPTION in 2 >0 9O n Q 1 M " J o O. m O> 0 20 40 60 80 100 w < ❑FINES CONTENT(%)❑ co 0 20 40 60 80 100 639.3 1'i:s.L\ Approx.3"of Topsoil (ML)RESIDUUM: 1 SPT 4-5-5-6 — — Stiff Yellow(2.5Y,8/6)Slightly Clayey Sandy SILT with 1 (10) Manganese Stains (ML)Very Stiff Pale Brown(2.5Y, 7/4)and Yellow(2.5Y,7/8) Slightly Clayey Sandy SILT with Manganese Stains SPT 5-9-9-10 2 (18) `1 (ML)Partially Weathered Rock when sampled becomes Light 5.0 ,- -'' Gray(5y,7/1)and Pale Brown(2.5Y,8/3)Sandy SILT SPT 7-11-13-14 634.3 yl%I/ 3 (24) SPT 25-34-39-50 4 (73) — I Vim ? /SPT 36-34-50 y> 5 (50/2") 10.o Bottom of Boring at 9.7 feet bgs.Auger Refusal 629.3 15.0 624.3 20.0 619.3 / SUMMIT ENGINEERING, LABORATORY 8c TESTING,INC. BORING NUMBER SW-2 3575 CENTRE CIRCLE - FORT MILL,SOUTH CAROLINA PAGE 1 OF 1 SUMMIT TELEPHONE: 704-504-1717 A..".e,e..�a„n=..=amp. SUMMIT-COMPANIES.COM CLIENT DRB Group PROJECT NAME Hemby Bridge ESHWT PROJECT NUMBER 5879.G0012 PROJECT LOCATION Union County, North Carolina DATE STARTED 10/31/22 COMPLETED 10/31/22 GROUND ELEVATION 638.65 ft HOLE SIZE 6 inches DRILLING CONTRACTOR SUMMIT GROUND WATER/CAVE-IN: DRILLING METHOD Hollow Stem Auger AT TIME OF DRILLING ---GW NE ATD LOGGED BY A. Boer CHECKED BY C.Payne AT END OF DRILLING ---GW NE>24 hrs NOTES See Figure 2"Boring Location Plan"for Approx. Boring Location AFTER DRILLING --- w o A SPT N VALUE A 0 U >-ct >- cow 0 20 40 60 80 100 _ I—w CC^ Hn It Q ,..,1- O MATERIAL DESCRIPTION J 2 >0 9O n Q 1 M " J o O. m O> 0 20 40 60 80 100 (3 2z () oz w < ❑FINES CONTENT(%)❑ co 0 20 40 60 80 100 638.7 1'i:s.L\ Approx.3"of Topsoil (ML)RESIDUUM: SPT 5-7-10-7 — — Very Stiff Yellow(2.5Y,8/6)and Light Gray(5Y,7/1)Sandy SILT 1 (17) A (ML)Very Stiff Yellow(2.5Y,8/6)Sandy SILT SPT 9-9-10-12 2 (19) • (ML)Stiff Pale Brown(2.5Y, 7/4)and Yellow(10YR,7/6)Sandy s.o SILT SPT 10-7-7-8 633.7 • • 3 (14) (ML)Very Hard Light Gray(2.5Y, 7/1)Sandy SILT SPT 8-25-42-50 4 (67) .. .... • 1-'��,f�,�',�, (ML)Partially Weathered Rock when sampled becomes Yellow �SPT 11-50 ,_','-'' (2.5Y,8/6)and Light Gray(2.5Y, 7/1)Sandy SILT _ 5 (50/4") » Ii — I SPT 39 50 15.0 Bottom of Boring at 14.6 feet bgs.Auger Refusal 623.7 20.0 618.7