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Home My WebLink AboutSW3230803_Soils/Geotechnical Report_20230829 SUMMIT ENGINEERING•LABORATORY•TESTING January 31, 2020 Mr. Steven Whitworth Kahuna Group 311 Unionville Indian Trail Rd W Indian Trail,North Carolina 28079 Email: swhitworth@kahuna-group.com Subject: Estimated Seasonal High-Water Table (ESHWT)Determinations Carolyn Farm Site—Additional Borings Wesley Chapel and Potter Road Wesley Chapel,North Carolina SUMMIT Project No. 3802.02 Dear Mr. Whitworth: SUMMIT Engineering, Laboratory and Testing, P. C. (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. This report contains a brief description of the project information provided to us, general site and subsurface conditions revealed during this study. PURPOSE OF STUDY The primary purpose of this study was to obtain information regarding the subsurface conditions near the proposed detention ponds, 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: ENGINEERING • LABORATORY • TESTING 3575 Centre Circle Drive I Fort Mill,South Carolina 29715 I (704)504- 1717 I (704)504- 1125(Fax) WWW.SUMMIT-COMPANIES.COM Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 • Photographic Logs, Site Vicinity Map and Boring Location Plan, • Summary of Test Boring Observations, visual soil classifications and descriptions, • 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 January 15, 2020 to perform Soil Test Borings BMP-1 and BMP-2. These borings were performed in the proposed detention ponds. The approximate location of the borings are shown on Figure 2 — "Boring Location Plan" provided in Appendix 1. The client (Kahuna Group), provided SUMMIT a "Sketch Plan" with boring locations and boring depths prepared by DPR Associates dated November 27, 2019 that indicated the configurations of the proposed construction planned for this project. The borings were located by professionals from our office using the provided plan,recreation-grade handheld GPS, existing topography, and aerial maps as reference. Therefore, the boring location should be considered approximate. We recommend the boring locations be surveyed to determine the actual boring locations and existing ground elevation. The soil test borings were performed using an ATV-mounted CME 550X drill rig, and extended to approximate depths ranging from 11.2 to 14.3 feet below the existing ground surface. 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 at designated intervals 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 each 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 2 Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 symbols are depicted in the "Boring Logs"provided in Appendix 2. GENERALIZED SUBSURFACE STRATIGRAPHY General subsurface conditions observed during our geotechnical study are described herein. For more detailed soil descriptions and stratifications at a particular test location, the respective "Boring Logs" provided in Appendix 2 should be reviewed. The horizontal stratification lines designating the interface between various strata represent approximate boundaries. 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 at the existing ground surface of the borings with a thickness of approximately 3 inches. Beneath the topsoil layer, existing fill soils (disturbed) were in encountered in Borings BMP-1 and BMP-2 to approximate depths of 4 feet and 2 feet below the existing ground surface, respectively. The fill soils consisted of sandy silts. Underlain the fill soils,residual(undisturbed)soils were encountered and extended to partially weathered rock (PWR). The residual soils consisted of sandy silts and lean clays. Partially Weathered Rock(PWR) conditions were encountered in Boring BMP-1 at an approximate depth of 10 feet and in Boring BMP-2 at an approximate depth of 6 feet below existing ground surface. PWR is defined as soil-like material exhibiting SPT N-values in excess of 100 bpf. Auger refusal conditions were not encountered in the soils test borings. GROUNDWATER LEVEL MEASUREMENTS At the time of drilling, groundwater was not observed in either of the borings. After waiting more than 24 hours, groundwater was observed at approximate depths of 10 feet in BMP-1 and 0.8 feet in BMP-2; however, the level in BMP-2 was influenced by rainwater entering the boring through surface flow. Please note moisture conditions of the soil samples were noted within some of the borings and moisture conditions within the soils may be an indication of the presence of groundwater. 3 Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 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 boring performed for this study. 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 ground water 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. CONCLUSIONS Based on our observations, Estimated Seasonal High-Water Table (ESHWT) indicators (water stained soils) were evident in soils sampled in Borings BMP-1 and BMP-2. As previously mentioned,the groundwater level was observed at a depth of 10 feet and 0.8 feet below the existing ground surface after waiting more than 24 hours in Borings BMP-1 and BMP-2,respectively. The elevated water levels could be perched water on top of a low impermeable soil strata (i.e. 50 bpf and greater material). 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. We recommend the BMP designer take consideration that the groundwater level will be above the soil's ESHWT indicators when designing the BMP pond and sand filter. 4 Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 The following table summarizes the results of the boring and our observations. Summary Table of the Boring Results and Our Observations GW Depth Boring GW Depth After PWR Test Depth ESHWT ATD 24 Hours Depth Location (Feet)' Depth(Feet)1 (Feet)1 (Feet)1 (Feet)' ELEV.: 610.0 BMP-1 11.2 7 NE 10 10 ELEV.: 688.0 BMP-2 14.3 5 NE 0.8 6 1 Depths from existing ground surface. NE—Not Encountered in Boring. The analyses and recommendations submitted in this report were based, in part, on data obtained from this study. 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. 5 Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 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 how l i1111///�/ 7,141111,,,,,/ �111. SUMMIT• :�.9 .•��OQ'QpFES31pN9` /�.,; Engineering, ;Z;�Q '.� n Laboratory ;w _ SEAL m Testing, P.C. c : I :'g , oaa3 , ��\ G.4361 A.% I \' \\ - (2:57 C) -';?0.--45-'''' f_AI I NE;t:%_'6'„(.1 e l„ IIIIrl1\ ..''.uuu,n..�``., Kerry C. Cooper, P.E. Ricky O. Coker, P.E. Geotechnical Department Manager Senior Project Manager LIST OF APPENDICES 1 Figure No. 1 —Site Location Map Figure No. 2—Boring Location Plan 2 Boring Logs 3 Photographic Log 6 Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 SUMMIT ENGINEERING • LABORATORY• TESTING APPENDIX 1 Figures -,e. 7! ', �,:;- Cornerstone 0 _n iii, .,,-1 , investment Services f 6 * T •WOr IhillIr SITE Church of '' a redeemer Y 1346 f+4 hh ' opt,tip �u IA kcj \it, Lai c.r.ki- . Wit„„....re tar CIAll S CL Elatos Park %,pia Wesley Chapel Ae R. Oa° - Wesley Chapel Elementary School .O} w " F Carolyn Farm Site lit Figure 1 Wesley Chapel and Potter Road Site Location Map Wesley Chapel, North Carolina SUMMIT 3575 Centre Circle SUMMIT Project No.: 3802.02 Fort Mill,South Carol4-1717 29715 ro SCALE: NTS � (803)so4-ln7 4 10 . _ g � ,` _ _-_ d'e rjed,11, al 1 1S6 • • _ _ -- '- - * \ • - • 1 - - ' l \ , t H i )\. • t„ N•P \ 1 6 1 I1 - k 4 ' - )1)1 ph'l '-e.-...''° \'\ _fleyc. ....,..,..., ILEM • -_2 -. ,,, B , qui it a a . Figure 3 Carolyn Farm Site ESHWT Boring Location Wesley Chapel and Potter Road Plan Wesley Chapel, North Carolina Approx. Soil Test Boring Location SUMMIT 3575 Centre Circle SUMMIT Project No.: 3802.02 Fort Mill,South Carolina 29715 SCALE: NTS (803)504-1717 Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 SUMMIT ENGINEERING • LABORATORY• TESTING APPENDIX 2 Boring Logs //- SUMMIT ENGINEERING,LABORATORY&TESTING,P.C. BORING NUMBER BMP-1 3575 CENTRE CIRCLE FORT MILL,SOUTH CAROLINA 29715 PAGE 1 OF 1 SUMMIT 704-504,1717 ., .. SUMMIT-COMPANIES.COM CLIENT Kahuna Group PROJECT NAME Carolyn Farm Site-Additional Bores PROJECT NUMBER 3802.02 PROJECT LOCATION Wesley Chapel, North Carolina DATE STARTED 1/15/20 COMPLETED GROUND ELEVATION 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 D. Robles CHECKED BY A.Jordan Y AT END OF DRILLING 10.00 ft NOTES Refer to Figure 2"Boring Location Plan"for Approx.Boring Location AFTER DRILLING --- w o A SPT N VALUE A z O U >ct >- cow 0 20 40 60 80 100 _ 1—w EC^ Hn Q O MATERIAL DESCRIPTION J CO >OU' 9O n Q 1 It i " J o O. m O> 0 20 40 60 80 100 (0 2Z U UZ w < W ❑FINES CONTENT(%)❑ co 0 20 40 60 80 100 ' ' ^`\ Approx.3"of Topsoil (ML)FILL: SPT 2-1-3-4 — - Soft Dark Brown(10YR,3/3)and Light Olive Brown(2.5Y, 5/6) 1 (4) Slightly Clayey Sandy SILT (ML)FILL: Very Stiff Moist Light Olive Brown(2.5Y, 5/6)and Light Brownish SPT 5 9 12-6 Gray(2.5Y,6/2)Slightly Clayey Sandy SILT 2 (21) (CL)RESIDUUM: s.o Stiff Moist Light Olive Brown(2.5Y, 5/6),Yellowish Brown(10YR, SPT 3-4-5-5 5/8)and Light Brownish Gray(2.5Y,6/2)Sandy Lean CLAY 3 (9) — (ML)Very Stiff Moist Light Yellowish Brown(2.5Y,6/4), Brownish Yellow(10YR,6/8)and Gray(2.5Y,5/1)Sandy SILT with SPT 3 5 14 28 Manganese Stains 4 (19) • (ML)Hard Pale Brown(2.5Y,7/4)and Gray(5Y,6/1)Sandy SILT with Rock Fragments with Rock Fragments and High Plastic Clay SPT 8-20-28-50 Seams » 5 (28) i 0.0 ii• (ML)Partially Weathered Rock(PWR)when sampled becomePft SPT 8-22-5) Light Yellowish Brown(2.5Y,6/4)and Light Gray(2.5Y, 7/2) >>A — - ; Sandy SILT Z 6 (50__ Bottom of Boring at 11.2 feet bgs, Boring Terminated 15.0 20.0 //- SUMMIT ENGINEERING,LABORATORY&TESTING,P.C. BORING NUMBER BMP-2 3575 CENTRE CIRCLE FORT MILL,SOUTH CAROLINA 29715 PAGE 1 OF 1 SUMMIT 704-504-1717 ., .. SUMMIT-COMPANIES.COM CLIENT Kahuna Group PROJECT NAME Carolyn Farm Site-Additional Bores PROJECT NUMBER 3802.02 PROJECT LOCATION Wesley Chapel, North Carolina DATE STARTED 1/15/20 COMPLETED GROUND ELEVATION 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 D. Robles CHECKED BY A.Jordan 1 AT END OF DRILLING 0.80 ft NOTES Refer to 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 EC^ Hn LIL Q 11 0 MATERIAL DESCRIPTION J CO >OU' 9O n Q I i " J o O. m O> 0 20 40 60 80 100 (3 2z () oz w < ❑FINES CONTENT(%)❑ co 0 20 40 60 80 100 ' l ^`\ Approx.3"of Topsoil (ML)FILL: t SPT 2-3-3-3 Firm Moist Olive(5Y,5/4)and Strong Brown(7.5YR,5/8)SligRt 1 (6) A Clayey Sandy SILT (ML)RESIDUUM: Firm Moist Olive Yellow(2.5Y,6/6)and Yellowish Red(5YR,5/8) SPT 3-3-4-8 — Slightly Clayey Sandy SILT with Manganese Stains 2 (7) (ML)Hard Pale Olive(5Y,6/3)Sandy SILT with Rock Fragments 5.0 and Manganese Stains SPT 4-18-24-28 3 (42) '" (ML)Partially Weathered Rock(PWR)when sampled becomes SPT 28-50 Pale Olive(5Y,6/3)Sandy SILT with Rock Fragments and 4 (50/5") >> — Manganese Stains Jz- '�, SPT 24-50 (50/3") >>A _ _: , — _t:::::-. — /SPT 14-50 Bottom of Boring at 14.3 feet bgs, Boring Terminated 15.0 20.0 Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 /1' 41=11k SUMMIT ENGINEERING • LABORATORY• TESTING APPENDIX 3 Photographic Log Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 Carolyn Farm —Additional Borings BMP-1 2 ' w = 4 4 - 6 6 8 I 8 10 Boring BMP-1 Samples (Approximate Depth = 0 to 10 feet below existing ground surface) Carolyn Farm —Additional Borings BMP-1 12 14 -_ - _ t 12 16 14 `- 16 18 W . 18 20 Boring SW-2 Samples (Approximate Depth = 10 to 11.2 feet below existing ground surface) Summary of ESHWT Determination SUMMIT Project No. 3802.02 Carolyn Farm Site—Additional Borings January 31,2020 Carolyn Farm —Additional Borings BMP-2 0 - 2 2 - — 4 4 -.- ` '�r 'v:' r�ro + 6 f67 - ., •6 E 8 S , = 10 Boring BMP-2 Samples (Approximate Depth = 0 to 14.3 feet below existing ground surface)