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HomeMy WebLinkAbout20170968 Ver 1_REDWOOD ROAD STUDY FINAL REPORT_20170804    DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 7/24/2017        Bridge Construction Feasibility Study Report | i Executive Summary   Located within the City of Durham’s jurisdiction, Redwood Road crosses a finger of Falls Lake that is fed by Panther Creek on the south side. Redwood Road provides a link to I-85 for the communities bordering Falls Lake, north and south of Cheek Road. Following Hurricane Matthew in October 2016, the NC Department of Transportation (NCDOT) identified two failed 10-foot diameter corrugated metal pipes that created a large sinkhole on the existing causeway, prompting NCDOT to close the road. The collapse produced an initial sinkhole approximately 3 feet in diameter in the middle of the roadway approximately halfway across the 920-foot long causeway. Continued storm water level rise contributed to the widening of the sinkhole to approximately 15 feet in diameter. Currently the road is closed and barricaded to pedestrian and vehicle traffic, and the size of the sinkhole has expanded to nearly the entire roadway width. NCDOT currently proposes to replace the failed pipes with a new bridge on the existing roadway alignment. Because the project is located on a causeway over a finger of Falls Lake, options for in-water bridge construction that minimize the impacts to Falls Lake to the extent practicable are needed. The objectives of this study are (1) to develop feasible bridge channel construction alternatives, (2) to study the cost effectiveness and impacts of the selected alternatives, and (3) to compare the alternatives and provide an engineering basis for NCDOT Division 5 to select a recommended alternative in consultation with the coordinating jurisdictional agencies for design and permitting purposes. This study assessed four construction options, including two options for dry excavation (inflatable dams and cellular cofferdams) and two options for wet excavation (turbidity curtains and sheet pile cofferdam). The following study report was presented to NCDOT and jurisdictional agencies on June 13, 2017, and the wet excavation alternative involving turbidity curtains (Alternative III) was selected for channel construction. A field scoping meeting was conducted on July 19, 2017 where it was determined from recent photographs that the sinkhole had further collapsed and widened to approximately 30 feet in diameter. This continued widening of the sinkhole, threatening to washout the embankment section completely at the location of the pipes, necessitates that channel construction proceed under emergency construction status. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report |ii Contents   Executive Summary .................................................................................................................................. i  I. OBJECTIVES ....................................................................................................................................... 1  II. DESCRIPTION ..................................................................................................................................... 1  A. Location ....................................................................................................................................... 1  B. Existing Conditions .................................................................................................................. 2  III. PROPOSED PROJECT ..................................................................................................................... 3  A. Roadway Alignment and Typical Section ........................................................................... 3  B. Bridge Type, Size, and Location ............................................................................................ 3  C. Utility Considerations ............................................................................................................... 4  D. Geotechnical Considerations ................................................................................................. 4  E. Lake Resource Considerations ............................................................................................. 4  F. Other Recreational Considerations ...................................................................................... 4  G. Seismic Considerations ........................................................................................................... 4  IV. CONSTRUCTION ALTERNATIVES ................................................................................................ 5  A. Dewatering Options .................................................................................................................. 5  B. Wet Excavation Options .......................................................................................................... 7  V. CONSTRUCTION ALTERNATIVES EVALUATION ..................................................................... 8  A. Dewatering Alternatives .......................................................................................................... 8  Alternative I: Inflatable Dams: ...................................................................................................... 8  B. Wet Excavation, Alternative III ............................................................................................. 12  C. Modified Wet Excavation, Alternative IV ........................................................................... 13  VI. COMPARATIVE ANALYSIS OF ALTERNATIVES ..................................................................... 15  VII. CONCLUSION ................................................................................................................................... 16  References ............................................................................................................................................... 19  Appendix A: Alternative Summary Table ........................................................................................ 20  Appendix B: Figures ............................................................................................................................. 21  Appendix C: Preliminary OPC ............................................................................................................ 34  Appendix D: Subsurface Investigation ............................................................................................ 36    DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 1 Redwood Road (SR 1637) Emergency Pipe Replacement Bridge Construction Feasibility Study I. OBJECTIVES The objectives of this study are: (1) To develop feasible bridge channel construction alternatives for replacement of two 10-foot diameter corrugated metal pipes with a new bridge. The pipes are located under Redwood Road (SR 1637) in Durham County, 1.0 mile south of the junction with SR 1670. The pipes failed during the Hurricane Matthew storm event of October 2016. Redwood Road crosses over a finger of Falls Lake fed from the flow of Panther Creek. (2) To study the cost effectiveness and impacts of the selected alternatives for removal of the existing pipes and construction of a new channel through the causeway in Falls Lake at the same location. (3) To compare the alternatives and provide an engineering basis for NCDOT Division 5 to select a recommended alternative with the concurrence of the coordinating jurisdictional agencies for design and permitting purposes. The Department will make the final selection and design determination. II. DESCRIPTION A. Location Redwood Road (SR 1637) crosses Falls Lake in the east-west direction where Panther Creek flows into a finger of Falls Lake from the southwest. Redwood Road starts from NW of I-85 and crosses under the interstate to run SW over the finger of Falls Lake and continues south to the intersection with Fletchers Chapel Road. Redwood Road provides a link to I-85 for the communities bordering Falls Lake, north and south of Cheek Road. The closure of Redwood Road cuts off boating ramp access located west of the project location. The segment of Redwood Road, in this feasibility study, contains two 10-foot diameter metal corrugated pipes located under the road at approximate Station 14+63.50 –L-. The purpose of the pipes is to discharge the flow from Panther Creek on the south side of the road into Falls Lake on the north side and equalize the water levels. The segment of Redwood Road across the finger is approximately 920 feet long and is located at approximately 36.052N latitude and 78.775W longitude. The project site is located within the jurisdiction of the City of Durham. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 2 Figure 1: Existing Roadway Alignment View B. Existing Conditions Redwood Road was constructed over the Falls Lake finger around 1980. At the time of construction, two 10-foot diameter corrugated metal pipes were placed at a depth of approximately 26’-0” and at a 120 degree skew to the roadway. The length of the pipes along the roadway and along the centerline of the pipes is 26’-5” and 119’-0”, respectively. The pipe extends past the shoulder with the inlet and outlet of the pipes cut off with the existing slope. The pipes are typically submerged or nearly submerged with the normal water surface elevation approximately 1’ -2’ below the crown on the pipes. The bed of Panther Creek is approximately 26’ below the crown of existing roadway at the project location with shallow bedrock located approximately 3’ below the creek bottom. The shallow bedrock prohibits the use of temporary cantilever sheet piles at the project site for construction dewatering. The post-Hurricane Matthew evaluation of Redwood Road showed that both pipes had failed from collapse producing a sinkhole approximately 3 feet in diameter in the roadway. One pipe had completely collapsed, while the other pipe was partially collapsed. An underwater inspection showed both pipes to be filled with sediment. Continued storm water level rise contributed to the widening of the sinkhole to approximately 15 feet diameter. Currently the road is closed and barricaded. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 3 Figure 2: View of Existing Sinkhole III. PROPOSED PROJECT A. Roadway Alignment and Typical Section The Redwood Road crossing of Falls Lake is approximately a 920 foot long tangent causeway generally running west to east with right-hand curves approaching and departing. See Appendix A for roadway alignment and typical section. This study is based on retaining approximately the same top width of the causeway from shoulder point to shoulder point as existing conditions. Other alternatives that may widen the causeway are not addressed, although similar construction alternatives may be applicable. B. Bridge Type, Size, and Location Although the preliminary hydraulic study is in progress and no recommendation is available at this time, it is understood that the site conditions are not suitable to replacing the existing pipes in kind. It is concluded that the existing pipes must be removed and replaced with a bridge. The proposed channel width, bridge length and span arrangement are to be determined by hydraulic analysis. The replacement structure is to be centered at the current location and at the current skew of 120 degrees to expedite the removal and replacement of the existing pipes and to align the new channel with the old submerged creek channel. For the purposes of this study the excavated earth channel is assumed to be 20 feet wide at the base with 2:1 slopes and 2 feet thickness of dumped rip rap stone on the slopes. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 4 C. Utility Considerations There are no existing or proposed utilities at the project location. The nearest overhead utility pole is located at the west side of the project location at the intersection of Redwood Road and the boat ramp access road, therefore, outside the project limits. D. Geotechnical Considerations The NCDOT Geotechnical Engineering Unit performed a Structure Subsurface Investigation (Ref. #310072) that included four borings at the project site. These boring were located 14 feet north and south of the roadway centerline at the proposed location of End Bent #1 and End Bent #2. At EB#1, red and brown, sandy clay alluvial was found at a depth of 16.5 feet below the roadway embankment, and at EB#2, gray, sandy clay alluvial was found at a depth of 16.5 feet below the roadway embankment. Borings were terminated with Standard Penetration Test (SPT) refusal in non-crystalline rock (siltstone) at 29.5 feet below the roadway embankment for EB#1A, 28.4 feet for EB#1B, 28.5 feet for EB#2A, and 28.4 feet for EB#2B. See Appendix D for the Subsurface Investigation Report. E. Lake Resource Considerations Panther Creek flows to Falls Lake, which provides drinking water to the City of Raleigh. The creek water surface elevations near the existing pipes are controlled by the lake elevations. The U.S. Army Corps of Engineers has confirmed that the water level in Falls Lake could not be lowered to accommodate working in the dry. The Lake is a significant recreational resource for the area and the causeway is frequently used for access for fishing in the lake. The most probable potential impact to the lake resulting from project activities would be disturbance of lake-bottom sediments and creation of additional turbidity in the water due to excavation of existing embankment soils and project related stormwater run-off. The use of Best Management Practices (BMPs) are required to minimize these potential impacts. Additionally, a recent assessment by NCDOT indicates that no threatened or endangered species are anticipated in the project area. F. Other Recreational Considerations The NC Mountains-to-Sea Trail and NC-2 Bicycle Trail are carried by the Redwood Road causeway. There are future plans for a Durham County greenway trail to be carried by the causeway. G. Seismic Considerations The project site is located in LRFD Bridge Design Specifications Seismic Zone 1. According to NCDOT Structures Management Design Manual, all bridges shall be designed in accordance with the AASHTO LRFD Bridge Design Specifications criteria for Seismic Zone 1. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 5 IV. CONSTRUCTION ALTERNATIVES A. Dewatering Options Available Types of Cofferdams: To construct an excavated channel through an existing earth causeway in a lake, the most common approach would be to build cofferdams on each side of the causeway and dewater the site of the excavation. This approach is referred to as a dewatering or “dry” option. The advantages of working in the “dry” are higher production rates for construction activities once the site is dewatered and complete confinement of the excavated materials and associated silt and sediments after the cofferdams are in place and until they are removed. Disadvantages can be the land disturbing activities to prepare the footprint and install the dams, the larger size of the site footprint to accommodate the dams, the increase in construction duration and the higher cost of construction. The typical types of cofferdams available for the dewatering approach and their applicability at this location are as follows: i. Earthen Cofferdam: This type of cofferdam is not an option for this project site due to the water level to be contained and the stream velocity. Earthen cofferdams are constructed in places where the depth of the water is 3m (10 feet) or less and the current velocity is very low. Due to the potential 12 to 14 ft. water depth at the project site, this system would not be able to accommodate dry working conditions. ii. Rock-fill Cofferdam: This type of cofferdam is not an option for this project site due to the water level to be contained and the availability of stone in the nearby areas. Rock-fill Cofferdams are constructed in areas where the depth of the water is 3m or less. Due to the potential 12 to 14 ft. water depth at the project site, this system would not be able to accommodate dry working conditions. iii. Single Sheet Pile Cofferdam: This type of cofferdam is not an option for this project site due to the water level to be contained and shallow bedrock depth preventing sufficient pile penetration for stability. Due to the potential 12 to 14 ft. water depth at the project site, this system would not be able to accommodate dry working conditions. iv. Double-wall Sheet Piling Cofferdam: This type of cofferdam consists of two straight, parallel vertical walls of sheet piling, tied to each other and the space between the walls is filled with soil or other granular material with a high coefficient of friction and unit weight. For this project site, the height of the cofferdam would be higher than 2.5m, therefore, it would need to be strutted at the top. Penetration of the sheet piling into the foundation is important for stability of the system. Due to the presence of shallow rock in the streambed, this option is not considered feasible for this project site. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 6 v. Braced (Crib) Cofferdam: This type of cofferdam is used in deep waters where it is difficult to penetrate the guide piles or sheet piles into the hard bed below. Braced Cofferdams are formed by driving two rows of vertical sheeting and bracing between them with wale and struts. Penetration of the sheet piling into the foundation is important for stability of the system. Due to the presence of shallow rock in the streambed, this option is not considered feasible for this project site. vi. Cellular Cofferdam: This type of cofferdam is mostly used for de-watering large areas with water depths between 18-21m (60-70ft.). Cellular cofferdams are mostly used during the construction of large scale marine structures like dams, locks, etc. A cellular cofferdam is made by driving or vibrating straight web steel sheet piles into the ground to form a series of inter-connected cells. The cells are constructed in various shapes and styles to suit the requirements of the project site. The cells are then filled with sand or gravel to make them stable against the various forces applied. There are two types of Cellular Cofferdams, Circular and Diaphragm. The Circular Cellular Cofferdam consists of a set of large diameter main circular cells interconnected by arcs of smaller cells. The walls of the connecting cells are perpendicular to the walls of the main circular cell of large diameter. The segmental arcs are joined by special T-piles to the main cells. The Diaphragm Cellular Cofferdam consists of circular arcs on the inner and outer sides, which are connected by straight diaphragm walls. The connection between the curved parts and the diaphragms are made by means of a specially fabricated Y-element. The cells are filled with coarse-grained soils for stability and reduction of leakage through the cofferdam. vii. Portable Wedge Dam (Portadam) Type: The portable wedge dam system is a lower cost, freestanding structure that has a skeletal steel framework and requires no ground penetration. The system is used primarily to divert floodwaters away from key infrastructure or for water storage. The skeletal steel framework can be pre-installed and the liner placed when the system is ready to operate. There is minimal environmental impact because of the freestanding nature of the system. The Army Corps of Engineers has tested and vetted the Portadam system. However, currently the equipment is only offered in various heights from 3 feet high to 12 feet high. Due to the potential 12 to 14 ft. water depth at the project site, this system would not be able to accommodate dry working conditions. Also, the steel frames are typically installed in the dry, which is not feasible at this site. viii. Inflatable Dam (AquaDam) Type: The inflatable dam concept combines multiple inner tubes within an outer tube to provide an effective portable dam to control water flow. The multiple impermeable inner tubes are filled with water to provide the mass needed for stability. For the AquaDam system a woven outer tube contains the inner tubes and provides the structural integrity of the system. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 7 The local water supply provides the water for mass weight. A coupling collar, made from the same high-strength material as the outer tube, is available to join two or more of the inflatable dams together. The closed end is fitted with the collar and the system is filled from the open end. This option would be necessary to customize an Aquadam for this site. All materials used in the construction of the inflatable dams are flexible to allow them to conform to uneven terrain and provide an effective seal between the ground and the dam. In order to contain the estimated 12 to 14 feet of water depth in the channel plus typical water level fluctuation, wave heights and necessary freeboard, a minimum of 24 feet in height would be needed for the primary inflatable dam. At a 24 feet height the expected width would be approximately 47 feet. A secondary support dam is recommended by the manufacturers where warranted by site conditions to reduce risk of foundation seal failure and risk from water level fluctuation. For this site a secondary dam is recommend by the manufacturers and would be required by the Department for safety during construction. The secondary dam would be 16 feet tall by approximately 33 feet wide. The two inflatable dam systems are placed concentrically around the project site. It is important that adequate clearance between the work area and the dam be provided to reduce the potential threat of puncturing the dam if heavy equipment is used in the work area. An underwater survey would be required within the footprint and adjacent areas of the dams to identify water depths and any potential hazards such as debris or stumps that could penetrate the membranes or break the bottom seal of the foundation. It is estimated that considerable debris and stump removal would be needed to ensure that the seal between the ground and the inflatable dam system would be impervious, as well as, reduce the threat of puncture to the tubes. Turbidity curtains would be needed to work in the wet to remove the debris and stumps. The number of laborers and time required to install a portable dam system is related to the size of the dam needed, the worksite terrain, water depths, and water flows. B. Wet Excavation Options Excavation without dewatering is most frequently done in coastal or port construction environments using dredges and pad or barge-supported clam shells, draglines or track mounted excavators. Typically the work is contained within a floating turbidity curtain or silt containment curtain. The reasons for considering a wet excavation approach for removing the existing pipes and constructing the new channel for the Redwood Road replacement are the high cost, higher failure risk, longer construction time and larger impacts of working in the “dry” utilizing cofferdams in consideration of the shallow rock depths and variable water depth at the site. The “wet” excavation method offers the DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 8 advantages of smaller disturbed areas, shorter construction time, lower cost and lower failure risk. The general approach for wet excavation at the Redwood Road site is to first complete as much “dry” excavation above the water line by conventional methods as feasible before excavating the channel below the waterline within double turbidity curtains, one containment line of curtains at the boundary of the disturbed areas and another farther out to encircle any escaping turbidity. Excavation is performed by land-based excavators or mat or barge supported drag line and clamshell operations. Any proposed drilled piers for construction of the bridge are coordinated with the excavation operations and constructed in permanent casings. After the wet excavation is completed and the slopes are prepared, remaining loose material and debris is removed with a vacuum dredge pipe and the embankment stabilized with rip rap, stone mats and other permanent slope protection materials. The bridge is then constructed above the channel and the normal lake level in the “dry.” A modified approach for minimizing the amount of wet excavation at the Redwood Road site would be to excavate the channel in multiple stages utilizing a braced cofferdam system constructed within the roadway embankment for stability. The braced cofferdam system would contain as much excavation below the waterline within the limits of the proposed bridge channel as feasible. The final stage of excavation would take place in water and include the cofferdam removal, soil between the dams and the pipe removal within the double turbidity curtains. Excavation would be performed by track-mounted excavators until the wet excavation stage, when the clam shell and buckets are used. The disadvantages of introducing the braced cofferdams is substantial added expense, slower production rates, and extended project duration. The use of the braced cofferdams result in a comparatively small overall decrease in the amount of wet excavation. V. CONSTRUCTION ALTERNATIVES EVALUATION A. Dewatering Alternatives Alternative I: Inflatable Dams: (See Appendix B, Figure 1 for a plan view of Alternative I, Inflatable Dam Alternative) i. Advantages: Lightweight construction, environmentally safe and specifically engineered to provide rapid deployment. The on-site requirements are only a portable pump and the local water supply. The inflation water is fresh water with no additives and can be released into the lake at the end of the project. ii. Disadvantages: A large footprint that is dependent on water depth and the need for a relatively smooth foundation surface to avoid punctures of the rubber membranes. Also, relatively calm water conditions with low wind and current are necessary for installation, and dam stability is sensitive to water level fluctuations. The length and width of inflatable dam needed to provide adequate work area will depend upon the final bridge length and channel width DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 9 determination. The impacted area of the installation will be increased along with the cost of construction due to the necessary surveys and clearing, grubbing and smoothing of the installation footprint area to minimize the risk that the inflatable dam will be punctured by debris or stumps and too optimize the seal of the dam to the lake floor. iii. Impacts: For the inflatable membrane cofferdam system, the disturbed area includes the footprint of the cofferdam, the area inside the cofferdam, plus a buffer area of about 10 to 15 feet outside the dam for construction operations, setting and stabilizing the dam and containing sediment and turbidity from construction operations. iv. Risks: The predominant risk for inflatable dams in a lake location is the variability of the lake level and creek flow due to storm events that may overtop the dams. Potential puncture from hidden objects in the muck, from storm debris impact or vandalism are anticipated risk. Above average variability in the bedrock profile or the lake bottom strata may create a highly irregular bottom profile and inconsistent foundation materials that may prohibit the ability of the inflatable dam to obtain a foundation seal against the lake bottom. v. Construction Sequence: 1. Perform bathometric survey of disturbed area. 2. Install turbidity curtains at max. 15’ from inflatable dam. 3. Remove stumps, debris and sharp stones or objects that may puncture dams. 4. Assemble equipment and labor needed to install dams per manufacturer’s guidelines 5. Install inflatable dams following manufacturer’s procedures 6. Install creek flow bypass pumps. 7. Dewater the construction site within the inflatable dams. 8. Install erosion control measures within the construction site in preparation for excavation operations. 9. Perform excavation operations within the dewatered site. 10. Install slope/channel protection (rip rap). 11. Flood channel to remove inflatable dams. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 10 12. Remove inflatable dams. 13. Remove turbidity curtains. vi. Construction Time: The time needed to prepare the area for placement of the inflatable dams, install the dams, complete the channel construction, remove the inflatable dams and perform any necessary clean up, is approximately 3 months. Alternative II: Cellular Cofferdam: (See Appendix B, Figure 2 for a plan view of Alternative II, Cellular Cofferdam Alternative) i. Advantages: The cellular cofferdam system has an advantage with greater scalability for increased stability against larger fluctuations in water depth and wave heights. The system also has a reasonably controlled and more predictable level of risk through long established design and construction procedures. Compared to the Diaphragm Cellular Cofferdam, each circular cell functions as a self-stabilizing unit, independent of, but connected to the adjacent circular cell by connector walls. A cellular cofferdam can support the required water depth effectively and drilled piles or rock anchors can be added if required for improved stability. Berms can be added to reinforce the stability of cells and reduce the cell sizes in some cases. ii. Disadvantages: The high cost and potential complication of installation due to shallow rock depths. The use of cellular cofferdams is dependent on the availability of the large amount of “flat” steel sheet pile sections that are required for the system. Also, if the interlocking steel sheet piles that comprise the cells cannot be driven sufficiently deep to self-stabilize during installation, then a temporary steel template framework may be required to assemble the cells, adding to the already high cost of the system. The cellular cofferdam is a driven pile or vibrated pile system with characteristic noise and vibration impacts. The completed steel cells are typically filled with sand that provides the weight and stability of the system. The sand must be removed from the cells and disposed of at the end of the project, adding to the cost of the system. Setting the circular cells requires a high level of technical skills in setting and driving the piles in accordance with the template and the ability to bear solidly on the rock foundation without breaking the sheet pile interlock. Also, because the diameter of the circular cells is limited by interlock tension, their ability to resist lateral pressure due to high heads is limited. The availability of steel sheet piling, the extensive pile driving and stabilizing of the structure during construction, the sensitivity of the cell filling operations to avoid internally overstressing or destabilizing the system and the logistics of the site access and necessary barge and boat operations to install and fill the cells could extend the project schedule by several months in comparison to the other alternatives. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 11 iii. Impacts: The disturbed area for the cellular cofferdam system includes the footprint of the cofferdam, the area inside the cofferdam, plus a buffer area of about 10 to 15 feet outside the cells for construction operations, setting and stabilizing pile templates and containing sediment and turbidity from construction operations. vii. Risks: The predominant risk for cofferdams in a lake location is the variability of the lake level and creek flow due to storm events that may overtop the dams. Variability in the bedrock profile or the lake bottom strata may create a highly irregular bottom profile and inconsistent foundation materials that may interfere with the ability to obtain a foundation seal against the lake bottom. iv. Construction Sequence: 1. Perform bathometric survey of disturbed area. 2. Install turbidity curtains at max. 15’ from cofferdam installation location. 3. Remove stumps, debris and sharp stones and other underwater objects that may impede cofferdam construction. 4. Assemble equipment and labor needed to install cofferdams. 5. Preassemble cells outside of contained area. 6. Set cofferdam cells within 15’ of turbidity curtains. 7. Drive cells to required depth. 8. Remove water and debris from inside cells. 9. Fill cells with sand. 10. Install creek flow bypass pumps. 11. Dewater the construction site within the cellular cofferdams 12. Install erosion control measures within the construction site in preparation for excavation operations. 13. Perform excavation operations within the dewatered site. 14. Install slope/channel protection (rip rap). 15. Flood channel to remove cofferdams. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 12 14. Remove and dispose of sand inside cells. 15. Remove and salvage sheeting/steel. 16. Remove turbidity curtains. viii. Construction Time: The time needed to prepare the area for placement of the cellular cofferdams, install the dams, complete the channel construction, remove the cellular cofferdams and perform any necessary clean up, is approximately seven months. The additional construction time is associated with the required lead time to order and fabricate the sheet piles and brace frames and templates needed for the cofferdam installation, and to place, excavate, fill and remove them. B. Wet Excavation, Alternative III (See Appendix B, Figure 3 for a plan view of Alternative III, Wet Excavation Alternative) i. Advantages: The reduced area of primary impacts, reduced costs, and minimized construction time. The impacted area is reduced by the absence of the substantially large cofferdam footprints and the associated need to clear and remove stumps and debris from those footprints. The primary containment curtain will surround the disturbed area, while the secondary curtain contains the turbidity and silt load that may escape the primary curtain. The elimination of cofferdams drastically reduces the cost of construction by eliminating the cost of labor, materials and task duration to prepare and construct the cofferdams and dewater the site. ii. Disadvantages: The increased difficulty of achieving and monitoring the normal construction quality and tolerances required by the NCDOT standard specifications as compared to working in the dry is one disadvantage. There is a need for modified or non-standard procedures for excavation, loading, hauling, disposal and silt control procedures as compared to “dry” excavation procedures. Larger volumes of disturbed soil materials and silt in the water are expected using the wet excavation methods and potentially less control of those materials. The additional disadvantage of wet excavation methods is that the turbidity curtains do not completely isolate the work area as in a dry condition. The curtains do not prevent the loss or movement of streambed sediments within the stream, but only contain turbid water. Wet methods such as vacuum dredge pipe will be used to reclaim material disturbed during construction; however, there will be a certain amount of material (including turbid water) that cannot be retrieved or collected. Non-conventional excavation or cleanup methods such as vacuum dredge pipes may be required for clearing loose debris to prepare underwater areas for placing slope protection and for final cleanup before removing the primary turbidity curtains. These non-conventional excavation and DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 13 cleanup methods are anticipated to be more costly and time consuming than conventional dry methods. iii. Impacts: The disturbed area for the wet excavation method includes the footprint of the excavated area within the existing embankment footprint and pipe bed in the lake, plus a buffer area of about 20 feet beyond the toe of slope, which is the control area for the primary turbidity curtain. The secondary control area is located outside of and enclosing the primary curtain to control turbidity escaping the primary curtain. iv. Risks: Primary risks are from storm events overwhelming the turbidity curtains. Other risks include damage or disruption by floating debris or recreational boats. An irregular bottom profile can also make the curtains less effective. v. Construction Sequence: (See Appendix B, Figure 3a-3b) 1. Install turbidity curtains at max. 20’ from toe of pipe. 2. Install erosion control measures within construction site in preparation for excavation operations. 3. Perform wet excavation operations within the construction site. 4. Cleanup underwater debris and loose material. 5. Install slope/channel protection (rip rap) 6. Remove turbidity curtains. vi. Construction Time: The time needed to install the turbidity curtains, complete the wet excavation and channel construction, remove the turbidity curtains and perform any necessary clean up, is approximately two months. C. Modified Wet Excavation, Alternative IV (See Appendix B, Figure 4 for a plan layout of Alternative IV, Modified Wet Excavation Alternative) i. Advantages: The reduced area of primary impacts, reduced costs and minimized construction time. The impacted area is reduced by the absence of the substantially large cofferdam footprints and the associated need to clear and remove stumps and debris from those footprints. The primary turbidity curtain will surround the disturbed area while the secondary curtain is located to the outside and enclosing the primary curtain to control turbidity that may escape the primary. The limited used of braced cofferdams reduces the amount of excavation in water by containing some of the material below the waterline within the cofferdams for excavation by track-mounted excavators. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 14 ii. Disadvantages: The increased difficulty of achieving and monitoring the normal construction quality and tolerances required by the DOT standard specifications as compared to working in the dry is one disadvantage. There is a need for modified or non-standard procedures for excavation, loading, hauling, disposal and silt control procedures as compared to “dry” excavation procedures. Larger volumes of disturbed sediments and silt in the water are expected compared to the dry methods but less material compared to the wet method without the partial cofferdam. The additional disadvantage of wet excavation methods is that the turbidity curtains do not completely isolate the work area as in a dry condition. The curtains do not prevent the loss or movement of streambed sediments within the stream, but only contain turbid water. Wet methods such as vacuum dredge pipe will be used to reclaim material disturbed during construction; however, there will be a certain amount of material (including turbid water) that cannot be retrieved or collected. Non-conventional excavation or cleanup methods such as vacuum dredge pipes may be required for clearing loose debris to prepare underwater areas for placing slope protection and for final cleanup before removing the primary turbidity curtains. These non-conventional excavation and cleanup methods are anticipated to be more costly and time consuming than conventional dry methods. The use of braced cofferdams to contain some of the excavation below the waterline substantially increases the cost and duration and slows the production rates of construction. The resulting reduction in wet excavation is small by comparison to the increased cost. iii. Impacts: The disturbed area for the wet excavation method includes the footprint of the excavated area within the existing embankment footprint and pipe bed in the lake, plus a buffer area of about 20 feet beyond the toe of slope, which is the control area for the primary turbidity curtain. The secondary control area is located outside of and enclosing the primary curtain. iv. Risks: Primary risks are from storm events overwhelming the cofferdams or turbidity curtains. Other risks include damage or disruption to the curtains by floating debris or recreational boats. An irregular bottom profile can also make the curtains less effective. v. Construction Sequence: (See Appendix B, Figure 4a-4e) 1. Install turbidity curtains 20’ from toe of pipe. 2. Install erosion control measures within construction site in preparation for excavation operations. 3. Excavate to 15’ above the bottom of the pipes within the right of way boundary. 4. Install sheet pile cofferdam. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 15 5. Excavate material from within cofferdams. 6. Remove cofferdams, excavate remaining material in water and remove pipes. 7. Cleanup underwater debris and loose material. 8. Install slope/channel protection (rip rap) 9. Remove turbidity curtains. vii. Construction Time: The time needed to complete the dry excavation, install the turbidity curtains and cofferdam, complete the wet excavation and channel construction, remove the cofferdams and perform any necessary clean up, is approximately five months. The additional construction time is associated with the required lead time to order and fabricate the sheet piles, brace frames and templates needed for the cofferdam installation. VI. COMPARATIVE ANALYSIS OF ALTERNATIVES Dry Excavation: The two alternatives considered for dry excavation are inflatable dams (Alternative I) and cellular cofferdams (Alternative II). These alternatives were determined to have the least overall impact on the aquatic environment. The impacts of both alternatives would come from lake-bottom clearing, stump and debris removal needed to place the dams, and dewatering. These impacts would be mitigated by the Best Management Practices utilizing turbidity curtains for bottom clearing and silt bags for pumping of the site water. For both alternatives, the clearing of debris and excavation would be performed by barge or mat mounted clam shell excavators and track mounted excavators. The estimated temporarily disturbed and impacted area for the inflatable dams is 2.11 acres due to the large dam size needed to contain the channel depth. The construction time for the inflatable dams is estimated at 3 months. The estimated temporarily disturbed and impacted area for the cellular cofferdam is 0.75 acres, with a channel construction time of 7 months, due to the lead time needed to fabricate the necessary sheet piles. The risks and vulnerabilities for the inflatable dams include the potential for the dams to be punctured by foundation debris or vandalism. The shallow bedrock has a variable profile which may affect the foundation seal and stability of the dams. Another risk for the inflatable dams is the potential for the flood water level to overtop the temporary dam or for the flood velocity to overwhelm the turbidity curtains during the clearing phase of installation. The risks and vulnerabilities for the cellular cofferdams include the potential for the shallow bedrock variable profile to affect the foundation seal and dam stability. Another risk for the cellular cofferdams is the potential for overtopping of the dams and turbidity curtains by the flood level and velocity. The inflatable dam option has an approximate cost of $2,042,000. The cellular cofferdam option has the highest approximate cost of all the alternatives at $2,704,000. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 16 Wet Excavation: The two alternatives considered for wet excavation are to excavate in water working inside turbidity curtains (Alternative III), and to excavate in water while maximizing dry excavation methods using a sheet pile cofferdam (Alternative IV). There are primary and secondary impact areas associated with both wet excavation alternatives. The impacts for both alternatives include disturbance of embankment soils and lake-bottom sediments from debris removal and excavation in water resulting in silt and turbidity. The secondary (outer) turbidity curtain for both alternatives is intended to control turbidity escaping from the inner curtain. These impacts would be mitigated by the Best Management Practices utilizing turbidity curtains around the site for to control turbid water, silt bags or basins for dredging or pumping of site water, and silt fences and other conventional methods for the dry portion of the excavation. For both alternatives, the clearing of debris and excavation can be performed by barge or mat mounted clam shell excavators and track mounted excavators. The estimated temporarily disturbed and impacted area for both wet excavated alternatives is approximately 0.49 acres. The construction time for the wet excavation method within the turbidity curtains is approximately two months. The construction time for the wet excavation utilizing the maximum dry excavation possible with sheet pile cofferdams is approximately five months due to the lead time needed to fabricate the sheet piles for the cofferdam. The risks and vulnerabilities of both wet excavation alternatives include the potential for the flood velocity to overwhelm the turbidity curtains or for any recreation craft to damage or disrupt the curtains. The approximate cost for complete wet excavation is the least of the four alternatives at $420,000. The approximate cost for the wet excavation while maximizing the dry excavation with a sheet pile cofferdam is also one of the least expensive at $832,000. For all the presented alternatives, the cost and construction time include the channel excavation, construction, and clean-up. The cost and construction time for the bridge is not included in this study. See Appendix A: Alternatives Summary Table for a tabulated summary of the costs, construction time, and impacts for each alternative. See Appendix B, Figure 5 for a section view of the proposed completed bridge channel. VII. CONCLUSION The construction alternatives presented in this study report include two dewatering alternatives, Alternative I (inflatable dams) and Alternative II (cellular cofferdams), and two wet excavation construction alternatives, Alternative III (turbidity curtains) and Alternative IV (turbidity curtains and sheet pile cofferdam). All of the construction alternatives in this study generate impacts to the adjacent lake area due to the required debris removal and excavation of the causeway and the lake bottom necessary to install the required turbidity curtains and construct the new bridge channel. All alternatives will utilize track or barge mounted excavators, clam shell excavators or drag lines for the necessary excavation and clearing of debris. All of the construction alternatives studied are vulnerable to the risk of overwhelming the turbidity curtains and/or overtopping temporary dams by rising flood waters from storm events. Additional vulnerabilities for all construction alternatives include recreational craft or floating debris damage to the turbidity curtains, the potential for the temporary dams to be damaged, or difficulty with the foundation seal due to irregular bedrock profiles or bottom strata or debris. The wet excavation alternatives have less area of DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 17 impact and less disturbed area than the dry excavation alternatives. The construction time to excavate the channel with the wet excavation alternative is the least of all the alternatives examined. Finally, the cost for channel construction is less when performed with the wet excavation alternative than the modified wet excavation or the dry excavation alternatives. On June 13, 2017, Division 5 and Dewberry conducted a meeting with the jurisdictional permitting agencies to present the draft study alternatives and a summary of the alternatives analysis developed herein with the objective of reaching a consensus of opinion for selecting a preferred alternative for construction. The analysis summary included anticipated impacts, durations and concept level costs for constructing a channel through the existing causeway for a bridge to replace the existing pipes. Present at the Feasibility Study Coordination Meeting were: NCDOT Division 5, NCDOT Bicycle and Pedestrian Division, US Army Corps of Engineers, NC Wildlife Resources Commission, and NCDEQ – Division of Water Resources. After presentation of the study alternatives and analysis, the consensus of opinion among those present and participating by phone was that the wet excavation method (Alternate III) detailed in this report is the recommended alternative for development of the pipe replacement project for construction and permitting. The primary environmental issue of concern expressed by the permitting agencies present is control of additional turbidity potentially generated by construction activities. The method of control during construction is to be turbidity curtains and turbidity monitoring. The details of the turbidity monitoring are to be determined. (See Appendix B, Figure 3 and Figures 3a-3b). Emergency Repair – Pipe Removal Utilizing Alternate III – Wet Excavation Method The rapid and continuing deterioration of the site caused by substantial loss of embankment around the failed pipes into the lake has forced an emergency response by the NCDOT to remove the existing pipe and stabilize an open channel for the flow of Panther Creek through the embankment. Figure 3: Collapse of Roadway Section at Pipes (July 18, 2017) DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 18 The Department is implementing the recommended alternative using the wet excavation method (Alternative III) for this emergency work. The Department will commit to installing turbidity curtains up and downstream of the work area in an effort to contain all turbidity in the lake that results from excavation of the failed pipes. Project personnel will routinely observe the turbidity curtains to ensure that minimal turbidity escapes these containment devices. If significant turbidity generated from excavation is observed to escape the turbidity curtains so as to degrade the lake water quality, the project will be temporarily halted until corrective action can be made. Advance warning notifications will be installed around the turbidity curtains to alert boaters of the construction area. Figure4: Severe Erosion Condition (July 18, 2017) DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 19 References 1. Turbidity Barriers & Silt Curtain, N.p., n.d. Web. 20 July 2017. www.erosionpollution.com/turbidity- barriers.html. 2. Types of Cofferdams and Their Construction Details. N.p., n.d. Web. 20 July 2017. https://theconstructor.org/water-resources/types-of-cofferdams-construction-details/13807 3. Arora, K. R. Cofferdam. Web. 8 September 2015, http://www.civilblog.com/cofferdam 4. AquaDam. N.p., n.d. Web. 20 July 2017. http://aquadam.net 5. PortaDam. N.p., n.d. Web. 20 July 2017. http://portadam.com 6. North Carolina Department of Transportation Statewide Bid Tabulations. 2015 & 2016 7. US Steel Sheet Pile Design Manual 8. USACE. Silt Curtains as a Dredging Project Management Practice, ERDC TN-DOER-E21, September 2005. 9. Control of Suspended Solids in Dredging Projects, NR Francing and DW Thompson, 2006. Proceedings of WEDZ XXVI Annual Meeting and 38th TAMU Dredging Seminar. DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 20 Appendix A: Alternative Summary Table DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 Co s t (3 ) Ch a n n e l   Co n s t r u c t i o n  Ti m e   (M o n t h s ) Te m p o r a r i l y   Im p a c t e d / D i s t u r b e d   Ar e a  (A c r e s ) Ty p e s  of  Im p a c t s Ex c a v a t i o n  Eq u i p m e n t  /  Me t h o d s Be s t  Ma n a g e m e n t  Practices  (BMP)Risks/Vulnerabilites R e m a r k s Al t e r n a t i v e  II I              Ex c a v a t e   in  Wa t e r :                                (W o r k   In s i d e  Tu r b i d i t y  Cu r t a i n s ) $4 1 9 , 8 0 0   2. 0 0 0 . 4 9 Pr i m a r y :  La k e  bo t t o m  de b r i s  re m o v a l   an d  ex c a v a t i o n .  Se c o n d a r y :  Se d i m e n t   an d  tu r b i d i t y  es c a p i n g  th e  in n e r   cu r t a i n  an d  co n t a i n e d  wi t h i n  th e   ou t e r  cu r t a i n . Tr a c k  or  ba r g e  mo u n t e d   ex c a v a t o r s ,  cl a m  sh e l l  or  dr a g   li n e . Tu r b i d i t y  Cu r t a i n s  (Primary  &  Se c o n d a r y ) .  Silt  bags  for  pumped   si t e  water.Flood  velocity  overwhelms  curtains. Recreation  craft  damage/disrupt  curtains Al t e r n a t i v e  IV              Ex c a v a t e   in  Wa t e r :                                (M a x i m i z e  Dr y  Ex c a v .  w/   Co f f e r d a m ) $8 3 2 , 2 0 0 5 . 0 0 0 . 4 9 Pr i m a r y :  La k e  bo t t o m  de b r i s  re m o v a l   an d  ex c a v a t i o n .  Se c o n d a r y :  Se d i m e n t   an d  tu r b i d i t y  es c a p i n g  th e  in n e r   cu r t a i n  an d  co n t a i n e d  wi t h i n  th e   ou t e r  cu r t a i n . Tr a c k  or  ba r g e  mo u n t e d   ex c a v a t o r s ,  cl a m  sh e l l  or  dr a g   li n e s . Tu r b i d i t y  Cu r t a i n s  (Primary  &  Se c o n d a r y ) .  Silt  bags  for  pumped   si t e  water.Flood  velocity  overwhelms  curtains. Recreation  craft  damage/disrupt  curtains Al t e r n a t i v e  I                In f l a t a b l e   Da m s :          (D e w a t e r e d )            $2 , 0 4 1 , 6 0 0   3. 0 0 2 . 1 1 La k e  bo t t o m  cl e a r i n g ,  st u m p  an d   de b r i s  re m o v a l  fo l l o w e d  by   de w a t e r i n g Tr a c k  mo u n t e d  ex c a v a t o r s .   Ba r g e  (o r  ma t )  mo u n t e d  cl a m   sh e l l  fo r  cl e a r i n g  de b r i s Tu r b i d i t y  Cu r t a i n s  for  bottom   cl e a r i n g .    Si l t  bags  for  pumped   si t e  water.Potential  for  inflatable  dams  to  be  punctured  by  foundation  debris  or  vandalism.  Shallow  bedrock  with  variable  profile  may  affect  foundation  seal  and  stability. Flood  level  overtops  temporary  dam. Flood  velocity  overwhelms  curtains  during  clearing  phase. Al t e r n a t i v e  II                Ce l l u l a r   Co f f e r d a m s :                        (D e w a t e r e d ) $2 , 7 0 4 , 2 0 0 7 . 0 0 0 . 7 5 La k e  bo t t o m  cl e a r i n g ,  st u m p  an d   de b r i s  re m o v a l  fo r  co f f e r d a m   co n s t r u c t i o n ,  fo l l o w e d  by  de w a t e r i n g Tr a c k  mo u n t e d  ex c a v a t o r s .   Ba r g e  (o r  ma t )  mo u n t e d  cl a m   sh e l l  fo r  cl e a r i n g  de b r i s Tu r b i d i t y  Cu r t a i n s  for  bottom   cl e a r i n g .    Si l t  bags  for  pumped   si t e  water.Shallow  bedrock  with  variable  profile  may  affect  foundation  seal  and  stability. Flood  level  overtops  temporary  dam. Flood  velocity  overwhelms  curtains  during  clearing  phase. (1 )  We t  Ex c a v a t i o n :  Ex c a v a t i o n  in  wa t e r  wi t h i n  tu r b i d i t y  cu r t a i n s  (n o  de w a t e r i n g ) .    Ex c a v a t i o n  ab o v e  th e  wa t e r  su r f a c e  wi l l  us e  co n v e n t i o n a l  me t h o d s . (2 )  Dr y  Ex c a v a t i o n :  Ex c a v a t i o n  ar e a  de w a t e r e d  us i n g  in f l a t a b l e  or  ce l l u l a r  co f f e r d a m s .  Cl e a r i n g  an d  co n s t r u c t i o n  of  co f f e r d a m s  wi t h i n  tu r b i d i t y  cu r t a i n s . Nu m e r i c a l  Va l u e s  Su b j e c t  to  Ch a n g e  as  Co n c e p t s  Ar e  Re f i n e d . (3 )  Th e  co s t  sh o w n  is  ap p r o x i m a t e  an d  is  an  Op i n i o n  of  Pr o b a b l e  Co s t  ba s e d  on  a  co n c e p t  le v e l  an a l y s i s  an d  is  su b j e c t  to  ch a n g e .    Th i s  is  th e  co s t  of   ch a n n e l  co n s t r u c t i o n  on l y .    Br i d g e  st r u c t u r e  co n s t r u c t i o n  is  no t  in c l u d e d  in  th i s  co s t  es t i m a t e . PI P E  RE M O V A L / B R I D G E  CH A N N E L  CO N S T R U C T I O N   SU M M A R Y  OF  CO S T S ,  CO N S T R U C T I O N  TI M E  AN D  IM P A C T S Ex c a v a t i o n  Co n d i t i o n We t   Ex c a v a t i o n (1 ) Dr y   Ex c a v a t i o n (2 ) Do c u S i g n E n v e l o p e I D : 3 A 4 B 1 3 0 D - D E 0 A - 4 E 0 4 - 8 5 F 4 - A A 2 1 3 3 5 0 D 6 E 4        Bridge Construction Feasibility Study Report | 21 Appendix B: Figures    DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 22   Figure 1: Inflatable Dam Alternative I Plan View DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 23 Figure 2: Cellular Cofferdam Alternative II Plan View DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 24 Figure 3: Wet Excavation Alternative III Plan View  DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 25   Figure 3a: Stage 1 - Wet Excavation Alternative III Construction Sequence DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 26   Figure 3b: Stage 2 - Wet Excavation Alternative III Construction Sequence   DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 27             Figure 4: Modified Wet Excavation Alternative IV Plan View DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 28                                                     Figure 4a: Stage 1 – Modified Wet Excavation Alternative IV Construction Sequence    DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 29                                                       Figure 4b: Stage 2 – Modified Wet Excavation Alternative IV Construction Sequence DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 30 Figure 4c: Stage 3 – Modified Wet Excavation Alternative IV Construction Sequence DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 31 Figure 4d: Stage 4 – Modified Wet Excavation Alternative IV Construction Sequence DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 32 Figure 4e: Stage 5 – Modified Wet Excavation Alternative IV Construction Sequence DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 33 Figure 5: Proposed Bridge Channel Section DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 34 Appendix C: Preliminary OPC    DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 35 DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4        Bridge Construction Feasibility Study Report | 36 Appendix D: Subsurface Investigation   DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 YELTRAWS T T E RAJ LICEN S E D G E O LOG IS N ORTH CARO LINA T2296 SEAL THE SITE DIFFERING FROM THOSE INDICATED IN THE SUBSURFACE INFORMATION. EXTENSION OF TIME FOR ANY REASON RESULTING FROM THE ACTUAL CONDITIONS ENCOUNTERED AT PROJECT. THE CONTRACTOR SHALL HAVE NO CLAIM FOR ADDITIONAL COMPENSATION OR FOR AN AS HE DEEMS NECESSARY TO SATISFY HIMSELF AS TO CONDITIONS TO BE ENCOUNTERED ON THE THE BIDDER OR CONTRACTOR IS CAUTIONED TO MAKE SUCH INDEPENDENT SUBSURFACE INVESTIGATIONS OPINION OF THE DEPARTMENT AS TO THE TYPE OF MATERIALS AND CONDITIONS TO BE ENCOUNTERED. SUFFICIENCY OR ACCURACY OF THE INVESTIGATION MADE, NOR THE INTERPRETATIONS MADE, OR DESIGN INFORMATION ON THIS PROJECT. THE DEPARTMENT DOES NOT WARRANT OR GUARANTEE THE AND CONSTRUCTION PURPOSES, REFER TO THE CONSTRUCTION PLANS AND DOCUMENTS FOR FINAL PRELIMINARY ONLY AND IN MANY CASES THE FINAL DESIGN DETAILS ARE DIFFERENT. FOR BIDDING THE BIDDER OR CONTRACTOR IS CAUTIONED THAT DETAILS SHOWN ON THE SUBSURFACE PLANS ARE PRECIPITATION AND WIND, AS WELL AS OTHER NON-CLIMATIC FACTORS. CONSIDERABLY WITH TIME ACCORDING TO CLIMATIC CONDITIONS INCLUDING TEMPERATURES, TIME OF THE INVESTIGATION. THESE WATER LEVELS OR SOIL MOISTURE CONDITIONS MAY VARY MOISTURE CONDITIONS INDICATED IN THE SUBSURFACE INVESTIGATIONS ARE AS RECORDED AT THE OF RELIABILITY INHERENT IN THE STANDARD TEST METHOD. THE OBSERVED WATER LEVELS OR SOIL SAMPLE DATA AND THE IN SITU (IN-PLACE) TEST DATA CAN BE RELIED ON ONLY TO THE DEGREE NECESSARILY REFLECT ACTUAL SUBSURFACE CONDITIONS BETWEEN BORINGS. THE LABORATORY ACTUAL SUBSURFACE CONDITIONS BETWEEN SAMPLED STRATA AND BOREHOLE INFORMATION MAY NOT UNLESS ENCOUNTERED IN A SAMPLE. INTERPRETED BOUNDARIES MAY NOT NECESSARILY REFLECT SOIL AND ROCK BOUNDARIES WITHIN A BOREHOLE ARE BASED ON GEOTECHNICAL INTERPRETATION BORING LOGS, ROCK CORES AND SOIL TEST DATA ARE NOT PART OF THE CONTRACT. GEOTECHNICAL ENGINEERING UNIT AT (919) 707-6850. THE SUBSURFACE PLANS AND REPORTS, FIELD BE REVIEWED OR INSPECTED IN RALEIGH BY CONTACTING THE N. C. DEPARTMENT OF TRANSPORTATION, PROPOSAL. THE VARIOUS FIELD BORING LOGS, ROCK CORES AND SOIL TEST DATA AVAILABLE MAY MADE FOR THE PURPOSE OF PREPARING THE SCOPE OF WORK TO BE INCLUDED IN THE REQUEST FOR THE SUBSURFACE INFORMATION AND THE SUBSURFACE INVESTIGATION ON WHICH IT IS BASED WERE R E F E R E N C E : 1 5 0 0 5 . 1 0 3 2 0 1 1 P R O J E C T : COUNTY PROJECT DESCRIPTION STATE OF NORTH CAROLINA D EPARTM ENT OF TRANSPORTATION D IVISION OF H IGH W AYS GEOTECH NICAL ENGINEERING U NIT STR U CTU R E SU BSU R FACE IN VESTIG ATIO N CAU TION NOTICE D ESCRIPTIONSHEET NO. CONTENTS CONDITIONS INDICATED HEREIN AND THE ACTUAL CONDITIONS AT THE PROJECT SITE. FOR INCREASED COMPENSATION OR EXTENSION OF TIME BASED ON DIFFERENCES BETWEEN THE BY HAVING REQUESTED THIS INFORMATION, THE CONTRACTOR SPECIFICALLY WAIVES ANY CLAIMS2. OR CONTRACT FOR THE PROJECT. OF TRANSPORTATION AS ACCURATE NOR IS IT CONSIDERED PART OF THE PLANS, SPECIFICATIONS THE INFORMATION CONTAINED HEREIN IS NOT IMPLIED OR GUARANTEED BY THE N. C. DEPARTMENT1. NOTES: 1 4-7 TITLE SHEET BORE LOG(S) 1310072 STATE PROJECT REFERENCE NO.STATE NO. SHEET SHEETS TOTAL N.C. 2, 2A 7 CHECKED BY SUBMITTED BY DATE INVESTIGATED BY DRAWN BY PERSONNEL D .G. PINTER J.R. SW ARTLEY O.B. OTI J.R. SW ARTLEY J.R. SW ARTLEY N.T. ROBERSON N.T. ROBERSON D ECEM BER 2016 DATESIGNATURE D O CU M EN T N O T C O N SID ER ED FIN A L U N LESS A LL SIG N A TU R ES CO M PLETED 3 SITE PLAN LEGEND (SOIL & ROCK) D U RH AM 3 1 0 0 7 2 REPLACE STRU CTU RE NO. 72 ON SR 1637 OVER FINGER TO FALLS LAK E DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 SOIL DESCRIPTION SOIL LEGEND AND AASHTO CLASSIFICATION CONSISTENCY OR DENSENESS TEXTURE OR GRAIN SIZE SOIL M OISTURE - CORRELATION OF TERM S PLASTICITY COLOR ORGANIC MATERIALS A-1 A-3 A-2 A-4 A-5 A-6 A-7 A-1-a A-1-b A-2-4 A-2-5 A-2-6 A-2-7 15 MX 30 MX 50 MX 25 MX 50 MX 10 MX 51 MN 35 MX 35 MX 36 MN 10 MX 40 MX 10 MX 41 MN 11 MN 40 MX 11 MN 41 MN 10 MX 41 MN 11 MN 41 M N 11 MN 40 MX 10 MX 40 MX 0 0 0 4 MX 8 MX 12 MX 16 MX SOILS CLAYEY MATTER ORGANIC AMOUNTS OF MODERATE LITTLE OR SOILS WITH SOILS ORGANIC HIGHLY EXCELLENT TO GOOD FAIR TO POOR POOR UNSUITABLE 2 N/A OPENING (MM) U.S. STD. SIEVE SIZE SAND FINE SAND COARSE BOULDER COBBLE GRAVEL SILT CLAY SIZE GRAIN IN. MM 0.25 (PI) RANGE PLASTIC LL PL OM SL LIQUID LIMIT PLASTIC LIMIT OPTIMUM MOISTURE SHRINKAGE LIM IT (SAT.) - SATURATED - - W ET - (W) - M OIST - (M) - DRY - (D) FROM BELOW THE GROUND W ATER TABLE USUALLY LIQUID; VERY W ET, USUALLY ATTAIN OPTIMUM M OISTURE SEMISOLID; REQUIRES DRYING TO SOLID; AT OR NEAR OPTIMUM M OISTURE ATTAIN OPTIMUM M OISTURE REQUIRES ADDITIONAL WATER TO GRADATION ANGULARITY OF GRAINS M INERALOGICAL COM POSITION COM PRESSIBILITY HIGHLY COMPRESSIBLE MODERATELY COMPRESSIBLE SLIGHTLY COM PRESSIBLE GROUND W ATER 0.005 40 0.42 0.25 4.76 10 2.00 0.075 0.053 0.052.0 MODIFIERS SUCH AS LIGHT, DARK, STREAKED, ETC. ARE USED TO DESCRIBE APPEARANCE. (BLDR.)(COB.)(GR.) (CSE. SD.) (SL.)(CL.) PERCENTAGE OF M ATERIAL HIGHLY SOME LITTLE TRACE 35% AND ABOVE 20 - 35% 10 - 20% 1 - 10% HIGHLY ORGANIC MODERATELY ORGANIC LITTLE ORGANIC MATTER TRACE OF ORGANIC M ATTER W ATER LEVEL IN BORE HOLE IM MEDIATELY AFTER DRILLING PW 24 SPRING OR SEEP STATIC W ATER LEVEL AFTER HOURS PERCHED WATER, SATURATED ZONE, OR W ATER BEARING STRATA DESCRIPTIONS M AY INCLUDE COLOR OR COLOR COMBINATIONS (TAN, RED, YELLOW -BROW N, BLUE-GRAY). THE ANGULARITY OR ROUNDNESS OF SOIL GRAINS IS DESIGNATED BY THE TERM S: 36 MN36 MN36 MN35 MX35 MX NO MX (NON-COHESIVE) M ATERIAL GRANULAR GENERALLY (COHESIVE) M ATERIAL SILT-CLAY GENERALLY 4 60 200 270 12 305 3 75 (ATTERBERG LIM ITS) SOIL M OISTURE SCALE DESCRIPTION FIELD MOISTURE GUIDE FOR FIELD MOISTURE DESCRIPTION (F SD.) CLASS. GENERAL CLASS. GROUP SYMBOL GROUP INDEX MATERIALS OF MAJOR USUAL TYPES #200 #40 #10 % PASSING ( 35% PASSING #200) GRANULAR MATERIALS ( 35% PASSING #200) SILT-CLAY MATERIALS PI OF A-7-5 SUBGROUP IS LL - 30 ; PI OF A-7-6 SUBGROUP IS LL - 30 A-3 A-1, A-2 A-6, A-7 A-4, A-5 SAND GRAVEL, AND STONE FRAGS. SAND FINE GRAVEL AND SAND SILTY OR CLAYEY SOILS SILTY POOR FAIR TO (N-VALUE) PENETRATION RESISTENCE RANGE OF STANDARD (TONS/FT ) COMPRESSIVE STRENGTH RANGE OF UNCONFINED CONSISTENCY COMPACTNESS OR PRIMARY SOIL TYPE VERY DENSE DENSE MEDIUM DENSE LOOSE VERY LOOSE HARD VERY STIFF STIFF MEDIUM STIFF SOFT VERY SOFT > 4 2 TO 4 1 TO 2 0.5 TO 1.0 0.25 TO 0.5 < 0.25 > 30 15 TO 30 8 TO 15 4 TO 8 2 TO 4 < 2 > 50 30 TO 50 10 TO 30 4 TO 10 < 4 26 OR MORE 16-25 6-15 0-5 HIGH MEDIUM SLIGHT VERY LOW > 10% 5 - 10% 3 - 5% 2 - 3% SOILS GRANULAR SOILS SILT - CLAY > 20% 12 - 20% 5 - 12% 3 - 5% A-7-6 A-7-5, LL > 50 LL = 31 - 50 LL < 31 AS SUBGRADE GEN. RATING PI LL PASSING #4O MATERIAL 6 MX NP SOILS GRANULAR SOILS CLAY SILT- PEAT MUCK, VERY STIFF, GRAY, SILTY CLAY, MOIST WITH INTERBEDDED FINE SAND LAYERS, HIGHLY PLASTIC, A-7-6 ANGULAR, SUBANGULAR, SUBROUNDED, OR ROUNDED. HIGHLY PLASTIC M ODERATELY PLASTIC SLIGHTLY PLASTIC NON PLASTIC AS MINERALOGICAL COMPOSITION, ANGULARITY, STRUCTURE, PLASTICITY, ETC. FOR EXAMPLE, CONSISTENCY, COLOR, TEXTURE, MOISTURE, AASHTO CLASSIFICATION, AND OTHER PERTINENT FACTORS SUCH IS BASED ON THE AASHTO SYSTEM. BASIC DESCRIPTIONS GENERALLY INCLUDE THE FOLLOWING: ACCORDING TO THE STANDARD PENETRATION TEST (AASHTO T 206, ASTM D1586). SOIL CLASSIFICATION BE PENETRATED WITH A CONTINUOUS FLIGHT POWER AUGER AND YIELD LESS THAN 100 BLOWS PER FOOT SOIL IS CONSIDERED UNCONSOLIDATED, SEMI-CONSOLIDATED, OR WEATHERED EARTH MATERIALS THAT CAN UNIFORMLY GRADED - INDICATES THAT SOIL PARTICLES ARE ALL APPROXIM ATELY THE SAM E SIZE. GAP-GRADED - INDICATES A MIXTURE OF UNIFORM PARTICLE SIZES OF TWO OR MORE SIZES. WELL GRADED - INDICATES A GOOD REPRESENTATION OF PARTICLE SIZES FROM FINE TO COARSE. PLASTICITY INDEX (PI)DRY STRENGTH ORGANIC MATERIAL OTHER MATERIAL M INERAL NAMES SUCH AS QUARTZ, FELDSPAR, MICA, TALC, KAOLIN, ETC. ARE USED IN DESCRIPTIONS WHEN THEY ARE CONSIDERED OF SIGNIFICANCE. SOIL AND ROCK LEGEND , TERM S, SYM BOLS, AND ABBREVIATIONS D IVISION OF H IGH W AYS GEOTECH NICAL ENGINEERING U NIT SU BSU R FACE IN VESTIG ATIO N (PAGE 1 OF 2) NORTH CAROLINA D EPARTM ENT OF TRANSPORTATION M ISCELLANEOUS SYM BOLS ABBREVIATIONS CL. - CLAY CSE. - COARSE FOSS. - FOSSILIFEROUS M ED. - M EDIUM SL. - SILT, SILTY SLI. - SLIGHTLY TCR - TRICONE REFUSAL BT - BORING TERMINATED FRAGS. - FRAGMENTS VST - VANE SHEAR TEST DPT - DYNAMIC PENETRATION TEST CPT - CONE PENETRATION TEST DMT - DILATOM ETER TEST SD. - SAND, SANDY M ICA. - MICACEOUS M OD. - M ODERATELY NP - NON PLASTIC SAP. - SAPROLITIC d - DRY UNIT W EIGHT - UNIT W EIGHT AR - AUGER REFUSAL w HI. - HIGHLY SOIL SYMBOL INFERRED SOIL BOUNDARY TEST BORING AUGER BORING CORE BORING INSTALLATION SLOPE INDICATOR L L L MW SPT DPT VST DMT PMT ALLUVIAL SOIL BOUNDARY INFERRED ROCK LINE SPT N-VALUE SOUNDING ROD 25/025 TEST CONE PENETROM ETER ADVANCING TOOLS: HAND TOOLS: POST HOLE DIGGER HAND AUGER SOUNDING ROD VANE SHEAR TEST PORTABLE HOIST CME-550 CLAY BITS 6" CONTINUOUS FLIGHT AUGER 8" HOLLOW AUGERS HARD FACED FINGER BITS TUNG.-CARBIDE INSERTS CASING W/ ADVANCER TRICONE TRICONE " TUNG.-CARB. CORE BIT CORE SIZE: -B -N HAMMER TYPE: AUTOMATIC EQUIPM ENT USED ON SUBJECT PROJECT RECOM M ENDATION SYM BOLS -H MANUAL " STEEL TEETH DRILL UNITS: VANE SHEAR TEST CBR - CALIFORNIA BEARING RATIO M ONITORING WELL OF ROCK STRUCTURES DIP & DIP DIRECTION SAMPLE ABBREVIATIONS F - FINE FRAC. - FRACTURED, FRACTURES ORG. - ORGANIC PMT - PRESSUREM ETER TEST - M OISTURE CONTENT V - VERY RT - RECOMPACTED TRIAXIAL RS - ROCK ST - SHELBY TUBE SS - SPLIT SPOON S - BULK WEA. - W EATHERED W ITH CORE TEST BORING - VOID RATIOe X X CME-55 CME-45C INSTALLATION PIEZOMETER WITH SOIL DESCRIPTION ROADWAY EMBANKMENT (RE) THAN ROADW AY EMBANKMENT ARTIFICIAL FILL (AF) OTHER 310072 SHEET NO.PROJECT REFERENCE NO. 2 UNCLASSIFIED EXCAVATION - UNSUITABLE WASTE UNCLASSIFIED EXCAVATION - ACCEPTABLE DEGRADABLE ROCK UNCLASSIFIED EXCAVATION - ACCEPTABLE, BUT NOT TO BE EMBANKMENT OR BACKFILL USED IN THE TOP 3 FEET OFSHALLOW UNDERCUT UNDERCUT DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 ROCK DESCRIPTION ROCK (W R) WEATHERED ROCK (CR) CRYSTALLINE ROCK (NCR) NON-CRYSTALLINE (CP) SEDIMENTARY ROCK COASTAL PLAIN VERY HARD HARD SOFT ROCK HARDNESS FRACTURE SPACING BEDDING THINLY LAM INATED THICKLY LAMINATED VERY THINLY BEDDED THINLY BEDDED THICKLY BEDDED VERY THICKLY BEDDED INDURATION FRIABLE MODERATELY INDURATED INDURATED EXTREMELY INDURATED COMPLETE SHELL BEDS, ETC. SPT REFUSAL. ROCK TYPE INCLUDES LIMESTONE, SANDSTONE, CEMENTED COASTAL PLAIN SEDIMENTS CEM ENTED INTO ROCK, BUT M AY NOT YIELD (SEV.) SEVERE (MOD. SEV.) SEVERE MODERATELY (MOD.) MODERATE WITH FRESH ROCK. DULL SOUND UNDER HAM MER BLOWS AND SHOWS SIGNIFICANT LOSS OF STRENGTH AS COMPARED GRANITOID ROCKS, MOST FELDSPARS ARE DULL AND DISCOLORED, SOME SHOW CLAY. ROCK HAS SIGNIFICANT PORTIONS OF ROCK SHOW DISCOLORATION AND W EATHERING EFFECTS. IN (SLI.) SLIGHT CRYSTALS ARE DULL AND DISCOLORED. CRYSTALLINE ROCKS RING UNDER HAMMER BLOWS. 1 INCH. OPEN JOINTS M AY CONTAIN CLAY. IN GRANITOID ROCKS SOME OCCASIONAL FELDSPAR ROCK GENERALLY FRESH, JOINTS STAINED AND DISCOLORATION EXTENDS INTO ROCK UP TO FRESH VERY CLOSE CLOSE MODERATELY CLOSE WIDE VERY WIDE HARD MODERATELY HARD MEDIUM SOFT VERY TO DETACH HAND SPECIM EN. CAN BE SCRATCHED BY KNIFE OR PICK ONLY WITH DIFFICULTY. HARD HAMMER BLOWS REQUIRED FINGERNAIL. OR M ORE IN THICKNESS CAN BE BROKEN BY FINGER PRESSURE. CAN BE SCRATCHED READILY BY CAN BE CARVED W ITH KNIFE. CAN BE EXCAVATED READILY W ITH POINT OF PICK. PIECES 1 INCH GENTLE BLOW BY HAMMER DISINTEGRATES SAM PLE. RUBBING WITH FINGER FREES NUMEROUS GRAINS; DIFFICULT TO BREAK WITH HAMM ER. GRAINS ARE DIFFICULT TO SEPARATE WITH STEEL PROBE; SAMPLE BREAKS ACROSS GRAINS. SHARP HAM MER BLOWS REQUIRED TO BREAK SAMPLE; W EATHERING ALSO AN EXAMPLE. SCATTERED CONCENTRATIONS. QUARTZ M AY BE PRESENT AS DIKES OR STRINGERS. SAPROLITE IS ROCK REDUCED TO SOIL. ROCK FABRIC NOT DISCERNIBLE, OR DISCERNIBLE ONLY IN SMALL AND TERM S AND DEFINITIONS LENS - A BODY OF SOIL OR ROCK THAT THINS OUT IN ONE OR MORE DIRECTIONS. JOINT - FRACTURE IN ROCK ALONG WHICH NO APPRECIABLE MOVEM ENT HAS OCCURRED. FISSILE - A PROPERTY OF SPLITTING ALONG CLOSELY SPACED PARALLEL PLANES. ARENACEOUS - APPLIED TO ROCKS THAT HAVE BEEN DERIVED FROM SAND OR THAT CONTAIN SAND. AQUIFER - A WATER BEARING FORMATION OR STRATA. OF SLOPE. COLLUVIUM - ROCK FRAGMENTS MIXED WITH SOIL DEPOSITED BY GRAVITY ON SLOPE OR AT BOTTOM ROCK LINE INDICATES THE LEVEL AT WHICH NON-COASTAL PLAIN MATERIAL W OULD YIELD SPT REFUSAL. TOPSOIL (TS.) - SURFACE SOILS USUALLY CONTAINING ORGANIC MATTER. ALLUVIUM (ALLUV.) - SOILS THAT HAVE BEEN TRANSPORTED BY W ATER. RESIDUAL (RES.) SOIL - SOIL FORM ED IN PLACE BY THE W EATHERING OF ROCK. (V SLI.) VERY SLIGHT OF A CRYSTALLINE NATURE. CRYSTALS ON A BROKEN SPECIMEN FACE SHINE BRIGHTLY. ROCK RINGS UNDER HAM MER BLOWS IF ROCK GENERALLY FRESH, JOINTS STAINED, SOME JOINTS M AY SHOW THIN CLAY COATINGS IF OPEN, SEVERAL HARD BLOWS OF THE GEOLOGIST'S PICK. CANNOT BE SCRATCHED BY KNIFE OR SHARP PICK. BREAKING OF HAND SPECIMENS REQUIRES BY M ODERATE BLOW S. EXCAVATED BY HARD BLOW OF A GEOLOGIST'S PICK. HAND SPECIMENS CAN BE DETACHED CAN BE SCRATCHED BY KNIFE OR PICK. GOUGES OR GROOVES TO 0.25 INCHES DEEP CAN BE POINT OF A GEOLOGIST'S PICK. CAN BE EXCAVATED IN SMALL CHIPS TO PEICES 1 INCH MAXIMUM SIZE BY HARD BLOW S OF THE CAN BE GROOVED OR GOUGED 0.05 INCHES DEEP BY FIRM PRESSURE OF KNIFE OR PICK POINT. LESS THAN 0.16 FEET 0.16 TO 1 FOOT 1 TO 3 FEET 3 TO 10 FEET MORE THAN 10 FEET < 0.008 FEET 0.008 - 0.03 FEET 0.03 - 0.16 FEET 0.16 - 1.5 FEET 1.5 - 4 FEET 4 FEET GNEISS, GABBRO, SCHIST, ETC. W OULD YIELD SPT REFUSAL IF TESTED. ROCK TYPE INCLUDES GRANITE, FINE TO COARSE GRAIN IGNEOUS AND METAM ORPHIC ROCK THAT ROCK TYPE INCLUDES PHYLLITE, SLATE, SANDSTONE, ETC. SEDIMENTARY ROCK THAT WOULD YEILD SPT REFUSAL IF TESTED. FINE TO COARSE GRAIN METAM ORPHIC AND NON-COASTAL PLAIN HAMMER IF CRYSTALLINE. ROCK FRESH, CRYSTALS BRIGHT, FEW JOINTS MAY SHOW SLIGHT STAINING. ROCK RINGS UNDER TO SOME EXTENT. SOME FRAGMENTS OF STRONG ROCK USUALLY REMAIN. REDUCED IN STRENGTH TO STRONG SOIL. IN GRANITOID ROCKS ALL FELDSPARS ARE KAOLINIZED ALL ROCK EXCEPT QUARTZ DISCOLORED OR STAINED. ROCK FABRIC CLEAR AND EVIDENT BUT CALCAREOUS (CALC.) - SOILS THAT CONTAIN APPRECIABLE AMOUNTS OF CALCIUM CARBONATE. FLOOD PLAIN (FP) - LAND BORDERING A STREAM, BUILT OF SEDIMENTS DEPOSITED BY THE STREAM. USUALLY INDICATES POOR AERATION AND LACK OF GOOD DRAINAGE. MOTTLED (MOT.) - IRREGULARLY MARKED W ITH SPOTS OF DIFFERENT COLORS. MOTTLING IN SOILS THE TOTAL LENGTH OF STRATA AND EXPRESSED AS A PERCENTAGE. LENGTH OF ROCK SEGM ENTS WITHIN A STRATUM EQUAL TO OR GREATER THAN 4 INCHES DIVIDED BY STRATA ROCK QUALITY DESIGNATION (SRQD) - A M EASURE OF ROCK QUALITY DESCRIBED BY TOTAL ITS LATERAL EXTENT. LEDGE - A SHELF-LIKE RIDGE OR PROJECTION OF ROCK W HOSE THICKNESS IS SMALL COMPARED TO ROCK. SAPROLITE (SAP.) - RESIDUAL SOIL THAT RETAINS THE RELIC STRUCTURE OR FABRIC OF THE PARENT A NOTABLE PROPORTION OF CLAY IN THEIR COM POSITION, SUCH AS SHALE, SLATE, ETC. ARGILLACEOUS - APPLIED TO ALL ROCKS OR SUBSTANCES COMPOSED OF CLAY MINERALS, OR HAVING SURFACE. WHICH IT IS ENCOUNTERED, BUT WHICH DOES NOT NECESSARILY RISE TO OR ABOVE THE GROUND ARTESIAN - GROUND W ATER THAT IS UNDER SUFFICIENT PRESSURE TO RISE ABOVE THE LEVEL AT BY TOTAL LENGTH OF CORE RUN AND EXPRESSED AS A PERCENTAGE. CORE RECOVERY (REC.) - TOTAL LENGTH OF ALL MATERIAL RECOVERED IN THE CORE BARREL DIVIDED ROCKS OR CUTS MASSIVE ROCK. DIKE - A TABULAR BODY OF IGNEOUS ROCK THAT CUTS ACROSS THE STRUCTURE OF ADJACENT HORIZONTAL. DIP - THE ANGLE AT WHICH A STRATUM OR ANY PLANAR FEATURE IS INCLINED FROM THE LINE OF DIP, MEASURED CLOCKWISE FROM NORTH. DIP DIRECTION (DIP AZIM UTH) - THE DIRECTION OR BEARING OF THE HORIZONTAL TRACE OF THE SIDES RELATIVE TO ONE ANOTHER PARALLEL TO THE FRACTURE. FAULT - A FRACTURE OR FRACTURE ZONE ALONG W HICH THERE HAS BEEN DISPLACEMENT OF THE PARENT MATERIAL. FLOAT - ROCK FRAGMENTS ON SURFACE NEAR THEIR ORIGiNAL POSITION AND DISLODGED FROM FIELD. FORMATION (FM.) - A M APPABLE GEOLOGIC UNIT THAT CAN BE RECOGNIZED AND TRACED IN THE OF AN INTERVENING IMPERVIOUS STRATUM. PERCHED W ATER - WATER MAINTAINED ABOVE THE NORMAL GROUND WATER LEVEL BY THE PRESENCE RUN AND EXPRESSED AS A PERCENTAGE. ROCK SEGMENTS EQUAL TO OR GREATER THAN 4 INCHES DIVIDED BY THE TOTAL LENGTH OF CORE ROCK QUALITY DESIGNATION (RQD) - A M EASURE OF ROCK QUALITY DESCRIBED BY TOTAL LENGTH OF THE BEDDING OR SCHISTOSITY OF THE INTRUDED ROCKS. RELATIVELY THIN COMPARED WITH ITS LATERAL EXTENT, THAT HAS BEEN EMPLACED PARALLEL TO SILL - AN INTRUSIVE BODY OF IGNEOUS ROCK OF APPROXIMATELY UNIFORM THICKNESS AND OR SLIP PLANE. SLICKENSIDE - POLISHED AND STRIATED SURFACE THAT RESULTS FROM FRICTION ALONG A FAULT TOTAL LENGTH OF STRATUM AND EXPRESSED AS A PERCENTAGE. STRATA CORE RECOVERY (SREC.) - TOTAL LENGTH OF STRATA MATERIAL RECOVERED DIVIDED BY TO OR LESS THAN 0.1 FOOT PER 60 BLOWS. WITH A 2 INCH OUTSIDE DIAM ETER SPLIT SPOON SAM PLER. SPT REFUSAL IS PENETRATION EQUAL A 140 LB. HAM MER FALLING 30 INCHES REQUIRED TO PRODUCE A PENETRATION OF 1 FOOT INTO SOIL STANDARD PENETRATION TEST (PENETRATION RESISTANCE) (SPT) - NUMBER OF BLOWS (N OR BPF) OF THICKNESSTERMSPACINGTERM FOR SEDIMENTARY ROCKS, INDURATION IS THE HARDENING OF M ATERIAL BY CEMENTING, HEAT, PRESSURE, ETC. BREAKS EASILY WHEN HIT WITH HAM MER. GRAINS CAN BE SEPARATED FROM SAMPLE W ITH STEEL PROBE; (V SEV.) SEVERE VERY ROCK MATERIALS ARE TYPICALLY DIVIDED AS FOLLOWS: SPT REFUSAL IS PENETRATION BY A SPLIT SPOON SAM PLER EQUAL TO OR LESS THAN 0.1 FOOT PER 60 BLOWS IN NON-COASTAL PLAIN MATERIAL, THE TRANSITION BETWEEN SOIL AND ROCK IS OFTEN REPRESENTED BY A ZONE OF WEATHERED ROCK. 100 BLOWS PER FOOT IF TESTED. NON-COASTAL PLAIN M ATERIAL THAT W OULD YIELD SPT N VALUES > HARD ROCK IS NON-COASTAL PLAIN M ATERIAL THAT W OULD YIELD SPT REFUSAL IF TESTED. AN INFERRED IF TESTED, W OULD YIELD SPT REFUSAL IF TESTED, W OULD YIELD SPT N VALUES > 100 BPF IF TESTED, WOULD YIELD SPT N VALUES < 100 BPF PIECES CAN BE BROKEN BY FINGER PRESSURE. FROM CHIPS TO SEVERAL INCHES IN SIZE BY M ODERATE BLOW S OF A PICK POINT. SMALL, THIN CAN BE GROVED OR GOUGED READILY BY KNIFE OR PICK. CAN BE EXCAVATED IN FRAGMENTS AND CAN BE EXCAVATED WITH A GEOLOGIST'S PICK. ROCK GIVES "CLUNK" SOUND WHEN STRUCK. AND DISCOLORED AND A MAJORITY SHOW KAOLINIZATION. ROCK SHOWS SEVERE LOSS OF STRENGTH ALL ROCK EXCEPT QUARTZ DISCOLORED OR STAINED. IN GRANITOID ROCKS, ALL FELDSPARS DULL VESTIGES OF ORIGINAL ROCK FABRIC REMAIN. REMAINING. SAPROLITE IS AN EXAMPLE OF ROCK WEATHERED TO A DEGREE THAT ONLY MINOR BUT MASS IS EFFECTIVELY REDUCED TO SOIL STATUS, WITH ONLY FRAGMENTS OF STRONG ROCK ALL ROCK EXCEPT QUARTZ DISCOLORED OR STAINED. ROCK FABRIC ELEMENTS ARE DISCERNIBLE ELEVATION: FEET NOTES: BENCH M ARK: SOIL AND ROCK LEGEND , TERM S, SYM BOLS, AND ABBREVIATIONS D IVISION OF H IGH W AYS GEOTECH NICAL ENGINEERING U NIT SU BSU R FACE IN VESTIG ATIO N (PAGE 2 OF 2) NORTH CAROLINA D EPARTM ENT OF TRANSPORTATION DATE: 8-15-14 310072 SHEET NO.PROJECT REFERENCE NO. 2A DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 S I T E P L A N P R O J E C T R E F E R E N C E N O . S H E E T N O . F E E T 0 1 0 0 2 0 0 F A L L S L A K E F A L L S L A K E W O O D S W O O D S W O O D S E B 1 - A E B 1 - B E B 2 - B E B 2 - A S R 1 6 3 7 ( R E D W O O D R D . ) S R 1 6 3 7 ( R E D W O O D R D . ) T O I - 8 5 3 3 1 0 0 7 2 - E L - N AD 83 DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 3.4 8.4 13.4 18.4 23.4 28.4 29.4 0.0 12.0 16.5 24.4 28.0 29.4 29.5 ROADWAY EMBANKMENT RED AND BROWN, SANDY SILT AND SANDY CLAY ALLUVIAL RED AND BROWN, SANDY CLAY RESIDUAL RED AND GRAY, SANDY CLAY WEATHERED ROCK (SILTSTONE) NON-CRYSTALLINE ROCK (SILTSTONE) Boring Terminated with Standard Penetration Test Refusal at Depth 29.5 ft IN NON-CRYSTALLINE ROCK (SILTSTONE) 7 6 4 3 5 8 7 6 5 13 7 5 4 2 4 100/0.2 60/0.1 SHEET 4 DRIVE ELEV (ft) DEPTH (ft)DEPTH (ft) SOIL AND ROCK DESCRIPTION L O G SAMP. NO.MOI ELEV. (ft) BLOW COUNT 0.5ft 0.5ft0.5ft BLOWS PER FOOT 25 50 750 100 BORE LOG OFFSET 13 ft LT ALIGNMENT -EL- EASTING 2,066,462 19.0 17.0 SITE DESCRIPTION SINK HOLE NEAR PIPE NO. 72 ON SR 1637 OVER FINGER TO FALLS LAKE BORING NO.EB1-A GROUND WTR (ft) TOTAL DEPTH 29.5 ft SURFACE WATER DEPTH N/ACOMP. DATE 12/20/16START DATE 12/20/16 GEOLOGIST Swartley, J. R. STATION N/A COLLAR ELEV.N/A 0 HR. 24 HR.NORTHING 837,801 DRILLER Pinter, D. G. DRILL RIG/HAMMER EFF./DATE RFO0074 CME-55 90% 07/12/2016 DRILL METHOD H.S. Augers HAMMER TYPE Automatic TIP 310072WBS15005.1032011 COUNTY DURHAM ELEV (ft) GEOTECHNICAL BORING REPORT NC D O T B O R E S I N G L E 3 1 0 0 7 2 _ G E O _ P I P E 0 0 7 2 _ S I N K _ H O L E _ S P T _ B O R I N G S . G P J N C _ D O T . G D T 1 2 / 2 2 / 1 6 GROUND SURFACE 15 13 10 8 18 100/0.2 60/0.1 DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 3.4 8.4 13.4 18.4 23.4 28.4 0.0 12.0 17.0 22.0 24.4 27.0 28.4 ROADWAY EMBANKMENT RED AND BROWN, SANDY SILT AND SANDY CLAY ALLUVIAL RED AND BROWN, SANDY CLAY GRAY, SILTY SAND RESIDUAL GRAY, SANDY SILT WEATHERED ROCK (SILTSTONE) Boring Terminated with Standard Penetration Test Refusal at Depth 28.4 ft ON NON-CRYSTALLINE ROCK (SILTSTONE) 5 6 4 2 6 5 8 4 2 8 4 6 3 2 4 60/0.0 SHEET 5 DRIVE ELEV (ft) DEPTH (ft)DEPTH (ft) SOIL AND ROCK DESCRIPTION L O G SAMP. NO.MOI ELEV. (ft) BLOW COUNT 0.5ft 0.5ft0.5ft BLOWS PER FOOT 25 50 750 100 BORE LOG OFFSET 14 ft RT ALIGNMENT -EL- EASTING 2,066,451 19.1 18.6 SITE DESCRIPTION SINK HOLE NEAR PIPE NO. 72 ON SR 1637 OVER FINGER TO FALLS LAKE BORING NO.EB1-B GROUND WTR (ft) TOTAL DEPTH 28.4 ft SURFACE WATER DEPTH N/ACOMP. DATE 12/20/16START DATE 12/20/16 GEOLOGIST Swartley, J. R. STATION N/A COLLAR ELEV.N/A 0 HR. 24 HR.NORTHING 837,773 DRILLER Pinter, D. G. DRILL RIG/HAMMER EFF./DATE RFO0074 CME-55 90% 07/12/2016 DRILL METHOD H.S. Augers HAMMER TYPE Automatic TIP 310072WBS15005.1032011 COUNTY DURHAM ELEV (ft) GEOTECHNICAL BORING REPORT NC D O T B O R E S I N G L E 3 1 0 0 7 2 _ G E O _ P I P E 0 0 7 2 _ S I N K _ H O L E _ S P T _ B O R I N G S . G P J N C _ D O T . G D T 1 2 / 2 2 / 1 6 GROUND SURFACE 10 14 8 4 14 60/0.0 DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 3.4 8.4 13.4 18.4 23.4 28.4 0.0 12.0 16.5 22.0 27.4 28.4 28.5 ROADWAY EMBANKMENT RED AND BROWN, SANDY SILT AND SANDY CLAY ALLUVIAL GRAY, SANDY CLAY GRAY, SILTY SAND WEATHERED ROCK (SILTSTONE) NON-CRYSTALLINE ROCK (SILTSTONE) Boring Terminated with Standard Penetration Test Refusal at Depth 28.5 ft IN NON-CRYSTALLINE ROCK (SILTSTONE) 6 6 6 3 5 7 9 7 3 6 8 6 3 2 3 60/0.1 SHEET 6 DRIVE ELEV (ft) DEPTH (ft)DEPTH (ft) SOIL AND ROCK DESCRIPTION L O G SAMP. NO.MOI ELEV. (ft) BLOW COUNT 0.5ft 0.5ft0.5ft BLOWS PER FOOT 25 50 750 100 BORE LOG OFFSET 14 ft LT ALIGNMENT -EL- EASTING 2,066,553 19.2 16.8 SITE DESCRIPTION SINK HOLE NEAR PIPE NO. 72 ON SR 1637 OVER FINGER TO FALLS LAKE BORING NO.EB2-A GROUND WTR (ft) TOTAL DEPTH 28.5 ft SURFACE WATER DEPTH N/ACOMP. DATE 12/20/16START DATE 12/20/16 GEOLOGIST Swartley, J. R. STATION N/A COLLAR ELEV.N/A 0 HR. 24 HR.NORTHING 837,756 DRILLER Pinter, D. G. DRILL RIG/HAMMER EFF./DATE RFO0074 CME-55 90% 07/12/2016 DRILL METHOD H.S. Augers HAMMER TYPE Automatic TIP 310072WBS15005.1032011 COUNTY DURHAM ELEV (ft) GEOTECHNICAL BORING REPORT NC D O T B O R E S I N G L E 3 1 0 0 7 2 _ G E O _ P I P E 0 0 7 2 _ S I N K _ H O L E _ S P T _ B O R I N G S . G P J N C _ D O T . G D T 1 2 / 2 2 / 1 6 GROUND SURFACE 13 15 13 6 11 60/0.1 DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4 3.4 8.4 13.4 18.4 23.4 28.4 0.0 12.0 16.5 24.4 27.0 28.4 ROADWAY EMBANKMENT RED AND BROWN, SANDY SILT AND SANDY CLAY ALLUVIAL GRAY, SANDY CLAY GRAY, SILTY SAND WEATHERED ROCK (SILTSTONE) Boring Terminated with Standard Penetration Test Refusal at Depth 28.4 ft ON NON-CRYSTALLINE ROCK (SILTSTONE) 4 6 5 2 2 8 7 6 4 4 4 7 4 3 3 60/0.0 SHEET 7 DRIVE ELEV (ft) DEPTH (ft)DEPTH (ft) SOIL AND ROCK DESCRIPTION L O G SAMP. NO.MOI ELEV. (ft) BLOW COUNT 0.5ft 0.5ft0.5ft BLOWS PER FOOT 25 50 750 100 BORE LOG OFFSET 14 ft RT ALIGNMENT -EL- EASTING 2,066,542 18.7 17.6 SITE DESCRIPTION SINK HOLE NEAR PIPE NO. 72 ON SR 1637 OVER FINGER TO FALLS LAKE BORING NO.EB2-B GROUND WTR (ft) TOTAL DEPTH 28.4 ft SURFACE WATER DEPTH N/ACOMP. DATE 12/20/16START DATE 12/20/16 GEOLOGIST Swartley, J. R. STATION N/A COLLAR ELEV.N/A 0 HR. 24 HR.NORTHING 837,730 DRILLER Pinter, D. G. DRILL RIG/HAMMER EFF./DATE RFO0074 CME-55 90% 07/12/2016 DRILL METHOD H.S. Augers HAMMER TYPE Automatic TIP 310072WBS15005.1032011 COUNTY DURHAM ELEV (ft) GEOTECHNICAL BORING REPORT NC D O T B O R E S I N G L E 3 1 0 0 7 2 _ G E O _ P I P E 0 0 7 2 _ S I N K _ H O L E _ S P T _ B O R I N G S . G P J N C _ D O T . G D T 1 2 / 2 2 / 1 6 GROUND SURFACE 12 13 11 6 6 60/0.0 DocuSign Envelope ID: 3A4B130D-DE0A-4E04-85F4-AA213350D6E4