The URL can be used to link to this page

Home My WebLink About20151309 Ver 1_Geotechnical Documentation - remaining site permitting 2015-07-15_20151216_ -, ; a � � II Date: July 15, 2015 Memorandum To: Attention: �� 6CSIG�N ANP FN�{N!#11l16 i�lRYIClS Mr. Jerry Parker, Division Environmental Supervisor — Division 7 Ms. Nikki Thomson, Environmental Specialist From: H. Andy Haymes, VP — Haymes Brothers, Inc. T. N. Parrott, PE — Summit, Infrastructure Engineering Branch Don Dewey, PE — Summit, Geotechnical Engineering Branch� ��,/y ! Subject: 17BP.7.R.63 Express Design Build, Year 2, Division 7 Set B Feasibility of Bottomless Culvert Construction — BR 000200 and BR 000085 The Request for Proposal for the referenced contract identified fourteen (14) existing bridges for replacement with bottomless culverts in Alamance and Orange Counties. In designing and constructing the affected bridge replacements, some sites have been found not conducive to bottomless culvert construction due to deep/low non-scourable rock elevations. To date, NCDOT has revised five (5) of the proposed structures (BR 000152, BR 000135, BR 000151, BR 000207, BR 000270) to four-sided culverts due to actual foundation conditions (deep/low non-scourable rock elevations) encountered. Two of the project sites (BR 000253 and BR 670101) exhibit rock elevations deemed appropriate for bottomless culvert applications and have been permitted accordingly. One project (BR 000154) was previously permitted and constructed as a bottomless culvert. For the remaining six project sites (BR 00248, BR 000200, BR 000085, BR 000146, BR 670042, and BR 670060), NCDOT has direct the Haymes Brothers Design Build Team to proceed with the culverts as bottomless structures. BR 000248 has been previously permitted as a bottomless culvert. Anticipated geotechnical conditions have been evaluated at all remaining sites. With the exception of BR 00248 (previously permitted), anticipated rock elevations at the remaining project sites are tabulated below: Page 1 of 4 SU� �11T D[SIGN AND lN61N!lRING SlIIVIClS BR 000200 - SR 1110 Mt. Zion Road, Alamance County NWS Geotechnical Data Min. Depth Proposed Culvert Footing Estimated Rock Depth Elev Boring / Rock to N/S Location Bottom of Ftg. Elev. at Footing to Key Sounding Elev. * Rock ** (ft) Elevation Key (ft) 601.8 Boring EB1-A 601.3 1.5 Inlet 600.93 596.7 (approach) 4.23 Boring E61-B 595.1 7.7 598.5 (trailing) 2.43 Boring EB2-A 597.7 5.1 Outlet 599.72 597.7 (approach) 2.02 Boring E62-B 597.0 5.8 594.5 (trailing) 5.22 Rod RS-1 596.5 6.3 Rod RS-2 599.6 3.2 Rod RS-3 600.4 2.4 Rod RS-4 598.5 4.3 * Weathered Rock Elevation ** N/5 Rock = Non-Scourable Rock (min. 1 foot below weathered rock) BR 000085 - SR 2158 Swepsonville Road, Alamance County NWS Geotechnical Data Min. Depth Proposed Culvert Footing Estimated Rock Depth Elev Boring / Rock to N/S Location Bottom of Ftg. Elev. at Footing to Key Sounding Elev. * Rock ** (ft) Elevation Key (ft) 510.5 Boring EB1-A 510.9 0.6 Inlet 509.86 506.4 (approach) 3.46 Boring EB1-B 509.9 1.6 508.4 (trailing) 1.46 Boring EB2-A 510.1 1.4 *** Outlet 509.62 506.5 (approach) 3.12 Boring EB2-A2 507.5 4.0 506.1 (trailing) 3.52 Boring EB2-B 505.4 6.1 Rod RS-1 507.8 3.7 Rod RS-2 508.3 3.2 * Weathered Rock Elevation ** N/S Rock = Non-Scourable Rock (min. 1 foot below weathered rock) ***Cobble/Boulder BR 000146 - SR 2363 Beale Road, Alamance County NWS Geotechnical Data Min. Depth Proposed Culvert Footing Estimated Rock Depth Elev Boring / Rock to N/S Location Bottom of Ftg. Elev. at Footing to Key Sounding Elev. * Rock ** (ft) Elevation Key (ft) 603.2 Boring E61-A 598.6 5.6 Inlet 602.24 601.3 (approach) 0.94 Boring E61-B 602.4 1.8 597.8 (trailing) 4.44 Boring E62-A 596.4 7.8 Outlet 602.18 598.2 (approach) 4.16 Boring E62-B 598.2 6.0 595.2 (trailing) 6.98 Rod RS-1 599.9 4.3 Page 2 of 4 Rod RS-2 603.2 1.0 Rod RS-3 599.5 4.7 * Weathered Rock Elevation ** N/S Rock = Non-Scourable Rock (min. 1 foot below weathered rock) SU� �IIT DlSIGN AND lN61N!lRIN6 SlRVIClf BR 670042 - SR 1007 Mebane Oaks Road, Orange County NWS Geotechnical Data Min. Depth Proposed Culvert Footing Estimated Rock Depth Elev Boring / Rock to N/S Location Bottom of Ftg. Elev. at Footing to Key Sounding Elev. * Rock ** (ft) Elevation Key (ft) 571.1 Boring EB1-A 570.8 1.3 Inlet 570.17 568.8 (approach) 1.37 Boring EB1-B 571.7 0.4 569 (trailing) 1.17 Boring EB2-A 571.0 1.1 Outlet 570.17 565.1 (approach) 5.07 Boring EB2-B 572.6 -0.5 564.8 (trailing) 5.37 Rod RSB1-B 567.1 5.0 Rod R562-B 566.5 5.6 * Weathered Rock Elevation ** N/S Rock = Non-Scourable Rock (min. 1 foot below weathered rock) BR 670060- SR 1002 St. Mar�s Road, Orange County NWS Geotechnical Data Min. Depth Proposed Culvert Footing Estimated Rock Depth Elev Boring / Rock to N/S Location Bottom of Ftg. Elev. at Footing to Key Sounding Elev. * Rock ** (ft) Elevation Key (ft) 485.5 Boring EB1-A 483.6 2.9 Inlet 484.57 481.5 (approach) 3.07 Boring EB1-B 484.8 1.7 480.7 (trailing) 3.87 Boring E62-A 483.5 3.0 Outlet 484.57 482.6 (approach) 1.97 Boring EB2-B 483.5 3.0 482.5 (trailing) 2.07 Rod RS-1 484.5 2.0 Rod RS-2 484.6 1.9 Rod RS-3 482.7 3.8 * Weathered Rock Elevation ** N/S Rock = Non-Scourable Rock (min. 1 foot below weathered rock) Enclosed with this memorandum are the geotechnical inventories for each project. The left side ofthe above tables provides a comparison of available geotechnical data (weathered rock elevations) to normal surface water (NWS) elevation. NCDOT requires bottomless culvert footings to be keyed one (1) foot into non-scourable (non-erosive) rock. NCDOT has generally defined non-scourable rock as being a minimum of one (1) foot below weathered rock, subject Page 3 of 4 �� hFSIGN FH6 iHGINEl�IkG flRVIClS to field verification. The minimum depth from NWS to non-scourable rock is calculated and tabulated accordingly. Depth from natural ground to non-scourable rock will be greater. Per NCDOT direction, the top of footing has been established at approximately one (1) foot above NWS. The right side of the tables provides a comparison of the proposed bottom of footing elevation (standard 1' 10" thick design) to the rock elevation estimated for the required one (1) foot deep key into non-scourable rock. The additional depth of excavation and footing construction required to achieve the required one (1) foot key into non-scourable rock is calculated accordingly. NCDOT Guidelines for Drainage Studies and Hydraulic Design stipulate "When a shallow (3-5 foot max. depthJ non-erosive rock foundation is found throughout the proposed site, the structure can be built on footings without a bottom allowing retention of the natural channel." The anticipated depth to non-erosive / non-scourable rock for projects BR 000200, BR 000085, BR 000146, BR 670042, and BR 670060 varies significantly and exceeds the aforementioned Guidelines at numerous locations. NCDOT has been apprised of these conditions and, as noted above, has directed the Haymes Brothers Design Build Team to proceed with the projects as bottomless culverts. Therefore, we request that projects BR 000200, BR 000085, BR 000146, BR 670042, and BR 670060 be permitted as bottomless culverts. Page 4 of 4