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Home My WebLink AboutSW4210301_SHWT_REPORT_SIGNED_20210316 AEV PARKING EXPANSION JEFFERSONil, NC SEASONAL HIGH WATER TABLE REPORT BREC ill Prepared By: Prepared For: Project Site: BREC, P.A. Kenneth Osborne 156 Northwest Drive 1526 Meadowview Drive Jefferson, NBC 28640 Wilkesboro, NC 28697 NCBELS 'Firm C-3448 (336) 844-4088 Max@brec.biz 4 March 2021 RR'EC, P.A. AEV PARKING EXPANSION 9 Table of Contents 1.0 General Information........................................................................................ 3 2.0 Methodology...................................................................................................3 3.0 Evaluation.......................................................................................................3 4.0 Results ...........................................................................................................8 5.0 Professional Certifications..............................................................................9 List of Figures Figure1 - Pit Locations.........................................................................................4 Figure2 Pit 1 Picture....................................................................... ................5 Figure 3 - Pit 1 Water Table Picture .....................................................................6 Figure4 - Pit 2 Picture ......................................................................................... 7 Figure 5 - Pit 2 Water Table Picture .....................................................................8 Figure 6 - SCM Water Table Profile......................................................................9 BREC, P.A. AEV PARKING EXPANSION 2 1.0 General Information This document contains information for determining the seasonal high water table (SHWT). This determination is needed to comply with state post-construction stormwater design requirements for stormwater control measures(SCM).The AEV Parking Expansion site is located at the intersection of Northwest Dr. and Gates Ln. in Jefferson, NC. Specifically, regulations for this area require SHWT to give 2 feet of clearance below the SCM. The subject site is composed of a vacant field with managed turf cover. Down grade of the site is a pond with water surface elevation at approximately 2974 feet in the forebay. Most of the site is composed of BrD soils which are hydrologic soil group B. Remaining portion of the site is CfE and BuC soils which are also in hydrologic soil group B. Post construction stormwater requirements will be satisfied with an above ground sand filter which is approved by NCDEQ as a primary SCM. 2.0 Methodology Pits are to be excavated in the near vicinity of the SCM to determine if water table is within the 2' limit of the SCM. Basin footprint is to be laid out and pit locations determined. Location chosen for Pit 1 was at the lower limit of the sand filter and Pit 2 at the upper limit of the sediment chamber. Pits are to be excavated and observed to determine current water table elevation. Date was chosen for excavation to be a minimum of 48 hours after a rainfall event. 3.0 Evaluation On February 25, 2021 at 3:00 PM, Max Prestwood, P.E. and Danny Long, P.L.S. of BREC, P.A. meet on site with the contractor to excavate pits to evaluate water table elevation. The weather was sunny with temperatures in the upper 50s during the visit. The last recorded rain event was on the 23rd. Some puddles remained in low areas in the field, but not around the SCM. Danny laid out the proposed SCM location and excavations were made to depths 2' or more below the SCM. Once completed Danny located the corners of the pits and measurements were made to the bottoms of the pits. Time was given to see if water would infiltrate into the pits. The pits were observed until the water level in them stabilized. Measurements were then made to the water level. The location of pits are shown in Figure 1 and pictures of pits are shown in Figures 2-5 BREC, P.A. AEV PARKING EXPANSION 3 Figure 1 - Pit Locations ry PIT z a SHWT 2 s5.6$° rp s 4 i. I f� k 0 \ I r u i PIT 1 SHWT 47' r BRED, P.A. AEV PARKING EXPANSION 4 i ure 2 Pit 1 Picture '"/✓� /i rannt;m�i/TlrlllyGYY%�rY'�r� i r/r / ;.r F ,.. „ ,,,,, , � ��/�//,/%/�� r f/,�/ II,G IJi 'Gi/rf�!/r✓ri/o/✓��%//I /il! /r r�r%/r/r%l r G ,p ,// '';rr7/'�/////G,r. r /%%r/////,,ai,i'F % ;;/ a„��i/ / / r,,; -.r%/i%%�rl/��i�✓/�/rf/��i k✓ rY� J��J��/p(/f�r / // �� /�// ry �;� ��"� ,r�N,fi,YYvr/'I�A>�'�/%;�m,r/your�;p,✓,f,�ifll<!/�7, r/'Y//%/✓ GO//r r al!(�i��/r%�� / )V;�A r y Mr*,`�yrU � k P y� ��d'k r l��1✓ / /r�r °I 1 y � �? 7n a� f r r✓// /iii�/ / i tr ya/r r„r✓v,,,,D..,,,,,1'`, ;�, ( F.; ��(�Y�� i��.. r j/jii r �GI 11 „ 1� r I k i '!b r�lUA/�'� m %� / ri/ / i fV�pN h�. (++ ,"�r✓�ir; Vr r n i� � IP r s� � „✓�Y w�� r /„ ��is I I I �14 1�, �fr r�� .YkIN W r rlV'rm%� L' fid( i :!` �' r6G v Vf � i "' a R�✓'"�llirKD n' / ✓�. r f 7r r r I JI ��f %r,,.;" r /r � �/r"� � lea � d ar ��rro Nr�(,�iyi;'�✓rxwY�r� �%u r �� b+P r 1 GJl ✓J � ��,V� � ( if f Y/i �l" , F f rn"'1�Pr( rf!��,, �q%fl � r Y r- �.✓'�1 r rug 4 ,�k w i�fr�!��; vi r F 1 r�Ot r i r Yl a f � r✓Y�'�L✓r�„�'y ,it "f of✓ r Ya1Gi/,y„�ir i/V C r I r r ) i � ", '�� „ ✓ ti<�N� '� ,�YpI�wBYd. �Ni/t4nrv'��j"'�� nli i m� �' ;';;g ,Ulrl/ iv trnYV llW i � � � u��J �Y Y�f�f � � F r f�Y wr rr d � � ✓ I uI� iq�JY� � MHO r 'krk vulu i �{� Y ,rl irh VG i Y P h r , BREC, P.A. AEV PARKING EXPANSION 5 Fi ure 3 - Pit I Water Table Picture it 6� p� i � f DfN�V,.o Y r I t BREC, P.A. AEV PARKING EXPANSION 6 Figured Pit 2 Picture r 1� ro - r r � a �f/r � �� / rc/r✓r/�J ,fj 6 �i7V/Fig r P n^ jr r 1 um�"�, � ry rl0rrr//ri/ a�fi wti� � v, BREC, P.A. AEV PARKING EXPANSION 7' H are 5- Pit 2 Water Fable Picture qq I 4.0 Results The elevations measured on site gave an elevation for water table in Pit 1 at 2988.47 feet and for Pit 2 at 2985.68 feet. A profile drawing was created to ensure that the min. 2' separation from the SCM would be maintained across the entirety of the sand filter. See Figure 6. All areas of the SCM have 2' or greater clearance from,the current water table as observed. Based on the climate history for this area and the recent precipitation records available the observed water table is likely higher than average. The past three months rainfall totals have been at or above average. Recent rainfalls combined with melting snows have kept soils saturated DREG, P.A. AEV PARKING EXPANSION 8 .......... prior to the excavation of the pits. This combined with short cool winter days have prevented soils from drying out. used on this information, the water levels recorded are what were used as the seasonal high water table elevation for the design of this SC . Figure 6- SCM Water Table Profile SEMMENT CHAMBER BOTTOM ELEV=2988 00 SAND FILTER BOTTOM ELEV=298U0 - - - - 2983.47 INATER TABLE L GREATER7HAN 2 5.0 Professional Certifications Signing below certifies that the information included in this report is accurate based on observations made on February 25, 2021, Engineers Certification CA&O SEAL 043863 Max Prestwood III, P.E. I N 0 C)G..........- � Surveyor Certification yygwwwlrtrr CAR-oi, 10- 0 4, SEAL L-41374 Danny ong, P.L.S SU 0. ......... 0 BRED, P.A. AEV PARKING EXPANSION 9