US 278 East Bound and West Bound. MacKay Creek and Skull Creek. Cursory Above Water and Underwater Investigation Of. Over

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1 Cursory Above Water and Underwater Investigation Of US 278 East Bound and West Bound Over MacKay Creek and Skull Creek In Hilton Head, South Carolina Bridges over MacKay Creek Bridges over Skull Creek Prepared by: 1180 Sam Rittenberg Blvd, Suite 105 Charleston, South Carolina (843) phone (843) fax Collins Project No

2 Over MacKay Creek and Skull Creek Cursory Above Water and Underwater Investigation of US 278 West Bound and US 278 East Bound Bridges Over MacKay Creek and Skull Creek Prepared by: Collins Engineers, Inc Sam Rittenberg Blvd, Suite 105 Charleston, South Carolina SUMMARY OF SIGNIFICANT FINDINGS Inspection Date: February 11 and 12, 2010 Significant Conditions Observed: US 278 West Bound over MacKay Creek o Crack up to 3/4 in. wide and 10 ft long located on the bottom of the pile cap at Bent 2. o Spall measuring 18 in. by 1 ft with 1.5 in. of penetration was located on the bottom of the pile cap at Bent 2. o The southernmost pile at Bent 2 exhibited 1/8 in. wide cracks with rust stains around all faces of the pile. US 278 East Bound over MacKay Creek o Random cracks ranging in width from 1/8 in. up to 1/2 in. wide with rust stains located on the piles and pile jackets. o Minor cracks and spalls in the superstructure beams. o A spall measuring 3 ft long by 1 ft wide with exposed reinforcing steel was located on the bottom of Beam 6 at Span 29. US 278 West Bound over Skull Creek o Approximately 5 ft of vertical undermining of the pier at the east side of the navigation channel. o Footing and seal exposure of the upstream nose of the pier at the west side of the navigation channel. o Missing section of the timber fender system at the west side of the navigation channel. o Cracks up to 1/4 in. wide with rust stains located on the bottom of a majority of the pile cap footings for the approach piers. o Light to moderate corrosion of the cross bracing between the steel plate girders. o Spall measuring 2 ft long by 10 in. wide with three in. of penetration located on the top of the concrete barrier rail at east end of the bridge. Collins Project No Page 1

3 Over MacKay Creek and Skull Creek SUMMARY OF SIGNIFICANT FINDINGS (Cont.) US 278 East Bound over Skull Creek o Footing and seal exposure of the pier at the east side of the navigation channel. o A void between the footing and seal measuring 12 in. vertical with 18 in. penetration and one exposed H-pile on the pier at the east side of the navigation channel. o Cracks up to 1/4 in. wide with rust stains located on the bottom of a majority of the pile cap footings for the approach piers. o Light to moderate corrosion of the cross bracing between the steel plate girders. SUMMARY OF BRIDGE RATINGS Bridge Deck Superstructure Substructure MacKay Creek WBL MacKay Creek EBL Skull Creek WBL Skull Creek EBL Collins Project No Page 2

4 Over MacKay Creek and Skull Creek 1.0 INTRODUCTION SCDOT Bridge Inspection Program According to the Federal Highway Administration a bridge is defined as A structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more that 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes where the clear distance between openings is less than half of the smaller contiguous openings. In accordance with Federal Highway Administration guidelines, the South Carolina Department of Transportation inspects their bridges at intervals not to exceed 24 months for above water inspections and 60 months for underwater inspections. These inspections are based on the Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation s Bridges. This publication is governed by the National Bridge Inspection Standards (NBIS). The NBIS was created in the early 1970 s as a result of the Silver Bridge collapse in West Virginia. Before this time, there was very little public interest in the inspection and maintenance of our nation s bridges. After 46 people died as a result of this collapse, the U.S. Congress required the Secretary of Transportation to establish a National Bridge Inspection Standard and develop a program to train bridge inspectors. These inspections are necessary for having an effective bridge maintenance program. The SCDOT performs five main types of inspections. - Initial Inspections Inspections performed to document the condition of a bridge after construction has been completed and the inventoried. - Routine Inspections Inspections used to document the physical and functional elements of bridges. Collins Project No Page 3

5 Over MacKay Creek and Skull Creek - In-depth Inspections Close up (arms length or hands on) inspections used to document the condition of the structure. Underwater inspections are typically considered in-depth inspections. - Scour The channel is inspected below the waterline to determine the level or extent of scour or channel migration. - Fracture Critical Inspection of critical tension members on a bridge structure. Fracture critical members are considered a member in tension that if failure occurs could result in partial or total failure of the structure. - Special Inspections These inspections are performed after repair, rehabilitation, replacement or after significant natural events like flooding, storms or seismic events. Typically all of these inspection levels are coordinated through the SCDOT Bridge Maintenance Office. The responsibility of this office is to coordinate bridge maintenance and rehabilitation activities, as well as, overseeing the SCDOT Bridge Management System (BMS). The bridge management system is a means for managing state wide bridge data throughout their design life. This includes collecting bridge inventory data, performing inspections, maintenance and rehabilitation. SCDOT Bridge Inspection Report Forms The standard SCDOT Inspection Form used by the Office of Bridge Maintenance is used as the primary means for inventorying and assigning condition and appraisal ratings to bridges in South Carolina. This form lists several bridge characteristics and their corresponding codes as listed in the Recording and Coding Guide. Some aspects of the form will be presented in the following sections. For a complete view of the information contained in this form, please refer to Appendix C. - General Bridge Data: This section lists the Bridge Identification Number, and general location with respect to route or waterway crossed. It also lists the year Collins Project No Page 4

6 Over MacKay Creek and Skull Creek it was built or reconditioned, the overall length, number of spans, and the type of structure. - Geometric Data: This section lists all pertinent bridge geometry such as: waterway navigation clearance, under clearances, vertical clearances, structure width, horizontal clearances, number of lanes, and sidewalk dimensions. - Condition Ratings: This section lists the inventory and operating rating, the last paint application date (if applicable), and the condition ratings of the deck, superstructure, and substructure. - Critical Inspection Data: This section lists the last inspection date, the inspection frequency, and gives an indication if special, fracture critical, or underwater inspections have been or need to be performed. - Appraisal Ratings: This section lists the overall appraisal of the structure, the deck geometry, under clearance, bridge posting, and waterway adequacy. Many of these ratings are not assigned by the actual inspector but are calculated using FHWA Edit/Update computer program. Bridge Element Grout Textual Data forms are also used by the inspector during routine bridge inspection. This form evaluates the condition of: bridge abutments, bents, piers, bearings, girders and beams, truss members, expansion joints, decks, curbs, bridge railings or barriers, paint systems, waterway condition, fender system, alignment of the roadway, traffic signs, and encroachments. Under these headings in Textual Data form, the inspector can add general or specific comments about the items listed above and their corresponding NBIS rating. An example of this form is presented in Appendix C. NBI ratings typically cover the deck, superstructure, and substructure in the overall bridge rating. The PONTIS system described in the following paragraph is an element based inspection that inventories and rates every element on the bridge. This includes but is not limited to the deck, beams, piles, bearings, railing, joints, etc. The different elements rated are according to the material used. For instance, a bare concrete deck and a concrete deck with asphalt overlay are considered different elements. Collins Project No Page 5

7 Over MacKay Creek and Skull Creek The SCDOT PONTIS BMS Element Data Form is a form that lists the Commonly Recognized (CoRe) Structural Elements for bridges. PONTIS is owned by the American Association of State Highway and Transportation Officials. The system is used to store bridge inventory and inspection data using the NBIS guidelines and also assigns condition states to each bridge element. With this system, each element corresponds to an element number in the PONTIS System. The total quantity of each element is then calculated. This quantity is then recorded as percentage of distribution in each corresponding condition state. Condition states are listed from Condition 1 (little or no deterioration) to Condition 5 (advanced deterioration). Each condition state is described for each element and any feasible actions are also presented. For example: If a bridge has 120 reinforced concrete piles this corresponds to Element 205 according to the CoRe Elements, and 20 of these piles have deterioration, 17 percent of these piles would be listed under Condition State 4 and the remaining 83 percent would be listed under Condition State 1. For the Condition State 4 rating, there are three feasible actions that can be performed on the 20 piles showing deterioration: do nothing, rehabilitate the piles, or replace the piles. PONTIS BMS give a more quantitative assessment of every structural element versus the general assessment given for the deck, superstructure, and substructure given in the NBI. The SCDOT PONTIS BMS Element Data Form is presented in Appendix C. Bridge Inspector Certifications The training and qualifications of an NBIS bridge inspector are presented in the Code of Federal Regulations 650C. The following excerpt is from the FHWA Bridge Inspectors Reference Manual: A program manager must, at a minimum: - Be a registered professional engineer, or have ten years bridge inspection experience; and have successfully completed a Federal Highway Administration (FHWA) approved comprehensive bridge inspection training course. Collins Project No Page 6

8 Over MacKay Creek and Skull Creek A NBIS bridge inspection team leader can qualify in five ways. - Have the qualifications for program manager as presented above. - Have five years bridge inspection experience and have successfully completed an FHWA approved comprehensive bridge inspection training course. - Be certified as a Level III or IV Bridge Safety Inspector under the National Society of Professional Engineer's program for National Certification in Engineering Technologies (NICET) and have successfully completed an FHWA approved comprehensive bridge inspection training course, or: - Have all of the following: - A bachelor's degree in engineering from a college or university accredited by or determined as substantially equivalent by the Accreditation Board for Engineering and Technology; - Successfully passed the National Council of Examiners for Engineering and Surveying Fundamentals of Engineering examination; - Two years of bridge inspection experience - Successfully completed an FHWA approved comprehensive bridge inspection training course. - Have all of the following: - An associate's degree in engineering or engineering technology from a college or university accredited by or determined as substantially equivalent by the Accreditation Board for Engineering and Technology; - Four years of bridge inspection experience; and - Successfully completed an FHWA approved comprehensive bridge inspection training course. - The individual charged with the overall responsibility for load rating bridges must be a registered professional engineer. - An underwater bridge inspection diver must complete an FHWA approved comprehensive bridge inspection training course or other FHWA approved underwater diver bridge inspection training course. Collins Project No Page 7

9 Over MacKay Creek and Skull Creek All of the inspectors for this cursory bridge inspection meet or exceed the requirements as presented above. Long Term Expectation of Bridge Life and Maintenance The current AASHTO LRFD code calls for bridges to be designed for a Design Life of 75 years (Section 1.2). What the actual in-service life of a structure may be is dependent on the owner s desires and expectations coupled with the effects of things like the bridge s exposure to environmental elements, quality of materials, construction type and practices used and the level of maintenance. The US 278 Bridges were built in the following years; 1982 for the two structures over Skull Creek, 1983 for the Westbound lane over MacKay Creek and 1956 for the one Eastbound lane over MacKay Creek. This means that they were most likely designed using a Design Life of 50 years, which was common at that time. Therefore, the Eastbound lane over MacKay Creek has already exceeded it s intended Design Life and the others are nearing year 30 of their Design Life. This does not mean that they are no longer functional or safe as the ability of a structure to survive and perform well beyond its Design Life has been well documented and is mostly dependent on the environment it resides in and the maintenance attention it has received. Many modern structures are now being designed with a Design Life of 100 years, such as the new Ravenel (Cooper River) Bridge in Charleston, SC. The new Oakland Bay Bridge in San Francisco has been designed for a Design Life of 150 years. Even though these structures are designed to last longer, whether they do or not will be greatly dependent on the factors already mentioned. Of the several factors that play a role in the reduction of a bridge s service life. Two of the harshest and one that is present at the US 278 bridges, are the coastal environment and heavy traffic use. In this location, these structures are subjected to high wave and wind forces as well as being constantly inundated in the corrosive salt Collins Project No Page 8

10 Over MacKay Creek and Skull Creek water environment. This applies to the superstructure as well as the substructure because of the chloride laden air, and our high humidity, transports that corrosive element to the bridges girders and concrete deck. The result of this long term exposure to a salt laden air and water environment is corrosion. Corrosion affects the life of both steel structures and reinforced concrete bridges. For steel structures, there are very visual signs of coating failure and accumulation of rust on the structural steel members. With concrete structures, the deterioration is usually not evident until it has reached advanced stages. This is because corrosion attacks the reinforcing steel buried within the concrete and only becomes visible once it has caused cracks and fractures (spalls) in the concrete surface and rust staining is then seen. The other factor mentioned was traffic volume. As the main bridges in and out of Hilton Head, these structures see not only large volumes of traffic, but heavy usage by truck traffic, which puts additional strain on the structure over time. Again, the maintenance of the structure plays the biggest role in preventing deterioration due to increase traffic volumes and loads. According to the Average Daily Traffic (ADT) volume obtained from the SCDOT for the 2008 period, US 278 traffic volumes within the area of investigation range from 44,300 to 57,800. A comparison of this ADT with other locations indicates that this volume is the highest in Beaufort County. For your reference, some other bridges that were constructed during the 1950 s and are located in similar coastal environments are listed below. These bridges are still open to traffic although we are not aware of the current condition of the structures. Little River Intracoastal Waterway Bridge (Horry County, South Carolina), Built 1935; rehabilitated 1980, Warren through truss swing bridge over Intracoastal Waterway on S (formerly US 17) in Little River Collins Project No Page 9

11 Over MacKay Creek and Skull Creek Ben Sawyer Intracoastal Waterway Bridge (Charleston County, South Carolina), Built 1945, rehabilitated 2010, Swing bridge over Intracoastal Waterway on SC 703 in Charleston Intracoastal Waterway Bridge (New Hanover County, North Carolina), Built 1956, Bascule bridge over Intracoastal Waterway on US 74/US 76 in Wrightsville Beach Intracoastal Waterway Bridge (Carteret County, North Carolina), Built 1935, Swing bridge over Intracoastal Waterway on NC 101 Surf City Bridge (Pender County, North Carolina), Built 1955, Swing bridge over Intracoastal Waterway on NC50/NC210 in Surf City Intracoastal Waterway Bridge (Palm Beach County, Florida), Built 1938 Bascule bridge over Intracoastal Waterway on FL A1A in Palm Beach Southern Boulevard Bridge (Palm Beach County, Florida), Built 1950, Bascule bridge over Intracoastal Waterway on Southern Boulevard in West Palm Beach Oakland Park Blvd. Bridge (Broward County, Florida), Built 1955, Bascule bridge over Intracoastal Waterway on Oakland Park Blvd. in Fort Lauderdale General Description of the Structures Bridge carries the west bound lanes of US 278 over MacKay Creek in Hilton Head, South Carolina. The bridge consists of 54 prestressed concrete girder spans and one steel girder span supported by prestressed square concrete pile bents. The deck consists of stay-in-place forms and a reinforced concrete deck. Bridge carries the east bound lanes of US 278 over MacKay Creek in Hilton Head, South Carolina. The bridge consists of 54 reinforced concrete girder spans and one steel girder span supported by multiple reinforced concrete pile bents. The structure originally consisted of pile bents with five octagonal concrete piles Collins Project No Page 10

12 Over MacKay Creek and Skull Creek supporting the reinforced concrete girders. Several of the original piles had a reinforced concrete circular jacket. When the bridge was widened, two prestressed concrete piles were driven on each side of the bents and support two additional prestressed concrete girders on either side of the bridge. A retrofit cap connected the widened section to the original cap. The deck consists of reinforced concrete with an asphalt overlay. Bridge carries the west bound lanes of US 278 over Skull Creek in Hilton Head, South Carolina. The bridge consists of 21 approach spans and five main channel spans. The main channel piers are comprised of a reinforced concrete hammer head piers supported by a submerged footing/seal combination founded on multiple steel H-piles. The approach spans are supported by a reinforced concrete hammer head pier configuration founded on a waterline pile cap footing supported by multiple prestressed concrete piles or prestressed concrete pile bents. The substructure units support steel plate girders with transverse steel cross bracing and a reinforced concrete deck. Bridge carries the east bound lanes of US 278 over Skull Creek in Hilton Head, South Carolina. The bridge is of a similar configuration to the west bound bridge. A 22 ft research vessel was used to gain access to the superstructure and substructure elements. Due to heavy traffic the decks were visually inspected from the inspection vehicle. Methods of Investigation An inspection team consisting of engineer-divers led by a South Carolinaregistered Professional Engineer-diver conducted the above water and underwater investigation of the four bridges leading to Hilton Head Island on February 11 and 12, Access to the bridge site was obtained from C.C. Haig Boat Landing on Pinckney Island. Collins Project No Page 11

13 Over MacKay Creek and Skull Creek The investigation consisted of a cursory inspection of the accessible portions of the substructure and superstructure. The cursory inspection was performed on a representative sample of the bridge components to detect obvious and gross bridge conditions. Particular attention was given to any observed areas of excessive deterioration or apparent distress, and the condition of any repairs was noted. A cursory assessment of the waterway and channel bottom conditions in the vicinity of the bridge was also made. The type of channel bottom material was noted, as well as the location and extent of any observed scour, riprap, or debris. 2.0 OBSERVED CONDITIONS AND ASSESMENT The following criteria govern the assessment ratings of the structural components of the inspected bridges: These criteria are established from the Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation s Bridges. Report No. FHWA- PD These codes also follow the SCDOT Bridge Inspection Form Ratings. - Code 9 - Excellent Condition - Code 8 - Very Good Condition no problems noted. - Code 7 - Good Condition some minor problems but functioning as intended. - Code 6 - Satisfactory Condition structural elements show some minor deterioration but are still functioning as intended. - Code 5 - Fair Condition all primary structural elements are sound but may have minor section loss, cracking, or spalling. - Code 4 - Poor Condition advanced section loss, deterioration, or spalling. - Code 3 - Serious Condition loss of section, deterioration, or spalling has seriously affected primary structural components. Local failures are possible. - Code 2 - Critical Condition advanced deterioration of primary structural elements. Fatigue cracks in steel or shear cracks in concrete may be present or scour may have removed substructure support. Unless closely monitored it may be necessary to close the bridge until corrective action is taken. Collins Project No Page 12

14 Over MacKay Creek and Skull Creek - Code 1 - Imminent Failure Condition major deterioration or section loss is present in critical structural components or obvious vertical or horizontal movement affecting structural stability. Bridge is closed to traffic but corrective action may be put back in light service. - Code 0 - out of service beyond corrective action. The following narrative will briefly describe the existing conditions encountered during the cursory inspections of US 278 WBL and EBL over MacKay and Skull Creek. The inspections were conducted over the course of two days. The weather was overcast with light rain and an air temperature of 40 ºF both days. The water under the bridge flowed between 0 and 2 ft/s during the inspection. Underwater visibility was approximately 2 ft. Item 61 Channel and Channel Protection The embankments at all four bridges were found to be in very good condition (Code 8). The banks along the waterways in the vicinity of the bridges were observed to be in stable condition. Embankment protection in the form of riprap was observed on the east and west banks of MacKay Creek and aquatic vegetation and oyster shells on the east and west banks of Skull Creek. There was no sign of active erosion. The channel bottom consisted of silty sand and oyster shells. There were no signs of heavy accumulation of debris or drift. US 278 West Bound over MacKay Creek Item 58 - Deck The concrete deck was found to be in good condition (Code 7). There were no noticeable spalls or significant cracks in the deck or the concrete barrier. In isolated areas, the expansion joint material had come loose along the shoulder of the roadway. Collins Project No Page 13

15 Over MacKay Creek and Skull Creek Item 59 Superstructure The superstructure was found to be in satisfactory condition (Code 6). Minor cracking was noted in isolated locations on the prestressed concrete girders. Several areas of concrete spall repair were noted in isolated locations. The steel girders supporting the main span showed signs of light to moderate corrosion with no signs of significant section loss. Item 60 - Substructure Overall, the substructure was also found to be in satisfactory condition (Code 6). Minor isolated cracks were noted on the piles above the high-water mark. Areas of minor isolated spall repair were noted in random locations. The most significant defects were located on Bent 2. On the east face of the reinforced concrete pile cap a crack measured up to 3/4 in. wide with rust stains. The crack measured approximately 10 ft long. The southernmost pile at Bent 2 had cracks up to 1/8 in. wide with rust stains around all faces of the pile and extended from the bottom of the pile cap down approximately 3 ft. A spall was located on the bottom of the pile cap at Bent 2. The spall measured approximately 1 ft by 18 in. with 1 in. of penetration. The piles at Bents 40 through 43 were inspected below water and were found to be in good condition. The piles exhibited a heavy layer of marine growth from the high-water mark to the channel bottom. No significant conditions were noted on the below water portions of these piles. Please refer to Photographs 1 to 12 for typical views of the conditions encountered on this bridge. US 278 East Bound over MacKay Creek Item 58 - Deck The deck was found to be in satisfactory condition (Code 6). The asphalt overlay showed minor signs of deterioration along the joints. Minor delamination of the asphalt Collins Project No Page 14

16 Over MacKay Creek and Skull Creek overlay up to 18 in. diameter was observed in isolated locations. There were no significant defects located on the concrete barrier. Item 59 Superstructure Overall, the superstructure was found to be in fair condition (Code 5). This condition was based on what the inspectors could visually assess from the boat. The bridge bearings were not accessible. The steel girders supporting the main span showed signs of light to moderate corrosion. Random minor cracks were noted on the bottom and sides of the reinforced concrete beams. Evidence of previous spall repairs were noted in several locations throughout the superstructure and appeared to be in good condition. One isolated spall measuring 3 ft horizontal by 1 ft vertical was located on the bottom of Beam 6 at Bent 29. The spall exposed one reinforcing which exhibited some corrosion but any loss of section could not be verified. Other random superficial spalls due to lack of sufficient cover over the reinforcing bars were noted on the reinforced concrete diaphragms. Item 60 - Substructure Several bents of different pile arrangements were inspected below water and were found to be in fair condition (Code 5). The piles exhibited a heavy layer of marine growth from the high-water mark to the channel bottom. Minor cracking with rust stains was observed within the tidal zone on several of the piles. Many of the octagonal piles have been retrofitted with concrete pile jackets. These jackets were typically located within the tidal zone. Several jackets exhibited minor cracking between 1/8 in. and 1/2 in. wide with rust stains; however, no significant deterioration such as: large spalls or section loss was noted on the inspected piles. Please refer to Photographs 13 to 26 for typical views of the conditions encountered on this bridge. Collins Project No Page 15

17 Over MacKay Creek and Skull Creek US 278 West Bound over Skull Creek Item 58 - Deck Overall the concrete deck was found to be in good condition (Code 7). There were no noticeable spalls or significant cracks in the deck. In areas, the expansion joint material had come loose in isolated locations along the shoulder of the roadway. A spall measuring approximately 2 ft long by 10 in. wide with no exposed reinforcing steel was found on the top of the concrete barrier rail at the east end of the bridge. Item 59 Superstructure The superstructure was visually inspected from the ground and the inspection boat and was found to be in satisfactory condition (Code 6). The steel plate girders exhibited minor loss of protective coating and showed no appreciable corrosion. Most of the transverse steel cross bracing had more moderate loss of protective coating with some minor corrosion. The corrosion was more pronounced where the steel cross bracing was connected to the steel plate girders. Due to the height of the structure any loss of section could not be verified. Item 60 - Substructure The inspections of the selected substructure elements revealed the most significant deterioration and were rated as fair condition (Code 5). The inspected substructure units exhibited a heavy layer of marine growth from the high-water mark to the channel bottom. The east channel pier exhibited complete footing and seal exposure with undermining of the seal at the upstream nose of the pier. The area of undermining measured up to 5 ft vertical. The footing of the pier located at the west side of the navigation channel was completely exposed and had approximately 4 ft of seal exposure. No undermining of the seal was detected at this pier. Cracks up to 1/4 in. wide with rust stains were located on the bottom of a majority of the pile cap footings for Collins Project No Page 16

18 Over MacKay Creek and Skull Creek the approach piers. These cracks were typically located 6 to 8 in. above the bottom of the pile cap footings and were likely caused by corrosion of the internal reinforcing steel due to chloride interaction from the saltwater environment. The timber fender system on the west side of the navigation channel beneath the west bound lane was partially missing. US 278 East Bound over Skull Creek Item 58 - Deck Overall the concrete deck was found to be in good condition (Code 7). There were no noticeable spalls or significant cracks in the deck. In areas, the expansion joint material had come loose in isolated locations along the shoulder of the roadway. Item 59 Superstructure The superstructure was visually inspected from the ground and the inspection boat and was found to be in satisfactory condition (Code 6). The steel plate girders exhibited minor loss of protective coating and showed no appreciable corrosion. Most of the transverse steel cross bracing had more moderate loss of protective coating with some minor corrosion. The corrosion was more pronounced where the steel cross bracing was connected to the steel plate girders. Due to the height of the structure any loss of section could not be verified. Item 60 - Substructure The inspections of the selected substructure elements revealed the most deterioration and were found to be in fair condition (Code 5). The inspected substructure units exhibited a heavy layer of marine growth from the high-water mark to the channel bottom. The east channel pier was found to have up to 5 ft of vertical seal exposure along the upstream nose. In addition, a void was detected at the footing and seal Collins Project No Page 17

19 Over MacKay Creek and Skull Creek interface. The void measured approximately 12 in. vertical with up to 18 in. of penetration. A steel H-pile was located in this void and exhibited moderate corrosion with no appreciable loss of section. Cracks up to 1/4 in. wide with rust stains were located on the bottom of a majority of the pile cap footings for the approach piers. These cracks were typically located 6 to 8 in. above the bottom of the pile cap footings and were likely caused by corrosion of the internal reinforcing steel due to chloride interaction from the saltwater environment. 3.0 RECOMMENDATIONS US 278 West Bound over MacKay Creek Item 58 - Deck There are no repair recommendations at this time; however, the expansion joint material should be monitored for future deterioration and may require replacement in the near future. Item 59 Superstructure It is recommended that the minor cracking of the concrete girders and the condition of any repairs be closely monitored during future inspections. The steel girders supporting the main span showed signs of light to moderate corrosion and should be cleaned and coated with a protective coating suitable for marine environments. Item 60 - Substructure The minor cracks located within the tidal zone should be monitored for continued deterioration during future inspections. The 3/4 in. wide crack with rust stains located on Bent 2 should be repaired by routing the crack and filling it with a flexible mastic sealant. In addition, the southernmost pile at Bent 2 showed more extensive cracking and should be repaired using a similar method. Collins Project No Page 18

20 Over MacKay Creek and Skull Creek The spall at the bottom of the pile cap at Bent 2 should also be repaired. This would include removing all unsound concrete and reforming the area to its original dimensions using a non-shrink grout suitable for marine environments. US 278 East Bound over MacKay Creek Item 58 Deck There are no repair recommendations at this time; however, the expansion joint material should be monitored for future deterioration and may require replacement in the near future. Item 59 Superstructure It is recommended that the minor cracking of the concrete girders and the condition of any repairs be closely monitored during future inspections. The steel girders supporting the main span showed signs of light to moderate corrosion and should be cleaned and coated with a protective coating suitable for marine environments. The spall located on Beam 6 of Bent 29 should be repaired. This would include removing all unsound concrete, cleaning and coating any reinforcing steel and reforming the area to its original dimensions using a non-shrink grout suitable for marine environments. Item 60 - Substructure There are no pile repair recommendations at this time; however, the piles and pile jackets should be monitored for increased deterioration during subsequent inspections. Collins Project No Page 19

21 Over MacKay Creek and Skull Creek US 278 West Bound over Skull Creek Item 58 Deck The expansion joint material should be monitored for future deterioration. The 2 ft long by 10 in. wide spall at the top of the barrier parapet is primarily cosmetic. It is also protected from impact from the median crash barrier. Item 59 Superstructure The loss of protective coating is relatively minor and should be monitored for further deterioration. Item 60 - Substructure The footing/seal exposure and undermining at the channel piers should be monitored closely during future underwater inspections. In addition, it is recommended to perform or review a scour analysis of these piers to determine the anticipated depth of scour and design countermeasures as necessary. The cracks located at the bottom of the pile cap footings that are larger that 1/4 in. wide should be routed and sealed with a flexible mastic sealant. The portion of the missing fender system on the west side of the navigation channel should be replaced. US 278 East Bound over Skull Creek Item 58 - Deck The expansion joint material should be monitored for future deterioration. Collins Project No Page 20

22 Over MacKay Creek and Skull Creek Item 59 Superstructure The loss of protective coating is relatively minor and should be monitored for further deterioration. Item 60 - Substructure The footing/seal exposure, as well as voids in the seal, at the channel piers should be monitored closely during future underwater inspections. In addition, it is recommended to perform or review a scour analysis of these piers to determine the anticipated depth of scour and design countermeasures as necessary. The cracks located at the bottom of the pile cap footings that are larger that 1/4 in. wide should be routed and sealed with a flexible mastic sealant. Overall, the four bridges are in satisfactory to fair condition. The type and amount of deterioration observed during the cursory inspection are indicative of structures of this age. Because the EBL Bridge over MacKay creek is older, (built in 1956), we saw more deterioration in the superstructure and substructure. This deterioration has potentially reduced some of the structures capacity but does not pose an immediate risk of failure. The structure should however be scheduled for significant rehabilitation and/or replacement in the near future. Respectfully submitted, COLLINS ENGINEERS, INC. James K. O Connor, P.E. Project Manager Originated by: William Barna, P.E. Collins Project No Page 21

23 Appendix A References

24 References: Bridge Inspector s Reference Manual, Publication No. FHWA NHI , Operation and Maintenance of Waterfront Facilities, Publication No. UFC , Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation s Bridges. Publication No. FHWA-PD , SCDOT Bridge Design Manual, Underwater Inspection of Bridges, Publication No. FHWA-DP-80-1, AASHTO Guide for Commonly Recognized (CoRe) Structural Elements, 1997.

25 Appendix B Photographs

26 Over MacKay and Skull Creek Photograph 1. View of Downstream Fascia, US 278 WBL over MacKay Creek. Photograph 2. View of Upstream Fascia, US 278 WBL over MacKay Creek. Collins Project No Appendix B

27 Over MacKay and Skull Creek Photograph 3. View of the Main Steel Girder Span, US 278 WBL over MacKay Creek. Photograph 4. Typical Underdeck and Prestressed Concrete Girder Condition, US 278 WBL over MacKay Creek. Collins Project No Appendix B

28 Over MacKay and Skull Creek Photograph 5. View of Crack Located on the East Face of Bent 2, US 278 WBL over MacKay Creek. Photograph 6. Close Up View of the Crack Located on the East Face of Bent 2, US 278 WBL over MacKay Creek. Collins Project No Appendix B

29 Over MacKay and Skull Creek Photograph 7. View of Spall Located on the Bottom of Bent 2, US 278 WBL over MacKay Creek. Photograph 8. View of Cracks with Rust Stains Located on the Southernmost Pile of Bent 2, US 278 WBL over MacKay Creek. Collins Project No Appendix B

30 Over MacKay and Skull Creek Photograph 9. View of West Embankment, US 278 WBL over MacKay Creek. Photograph 10. Typical Above Water Pile and Prestressed Concrete Girder Condition, US 278 WBL over MacKay Creek. Collins Project No Appendix B

31 Over MacKay and Skull Creek Photograph 11. Typical Prestressed Concrete Girder and Pile Cap Condition, US 278 WBL over MacKay Creek. Photograph 12. Typical Below Water Pile Condition Showing Heavy Marine Growth, US 278 WBL over Skull Creek. Collins Project No Appendix B

32 Over MacKay and Skull Creek Photograph 13. View of the Downstream Fascia, US 278 EBL over MacKay Creek. Photograph 14. Typical View of Superficial Spalls due to Lack of Sufficient Concrete Cover over the Reinforcing Steel in the Diaphragm, US 278 EBL over MacKay Creek. Collins Project No Appendix B

33 Over MacKay and Skull Creek Photograph 15. Typical Spall Repair Located on Bottom of Reinforced Concrete Beam, US 278 EBL over MacKay Creek. Photograph 16. Typical Bent with Longitudinally Battered Piles and Concrete Pile Jacket, US 278 EBL over MacKay Creek. Collins Project No Appendix B

34 Over MacKay and Skull Creek Photograph 17. Typical Bent with Transversely Battered Piles and Concrete Pile Jacket, US 278 EBL over MacKay Creek. Photograph 18. View of the Upstream Fascia, US 278 EBL over MacKay Creek. Collins Project No Appendix B

35 Over MacKay and Skull Creek Photograph 19. Typical Above Water Reinforced Concrete Pile Condition, US 278 EBL over MacKay Creek. Prestressed Concrete Girder Beam Saddle Reinforced Concrete Beam Photograph 20. View of a Typical Retrofit Pile Cap, US 278 EBL over McKay Creek. Collins Project No Appendix B

36 Over MacKay and Skull Creek Photograph 21. Typical Concrete Encasement Condition, US 278 EBL over MacKay Creek. Photograph 22. Typical Underdeck and Reinforced Concrete Girder Condition, US 278 EBL over MacKay Creek. Collins Project No Appendix B

37 Over MacKay and Skull Creek Photograph 23. Typical Main Span Steel Girder Condition, US 278 EBL over MacKay Creek. Photograph 24. Typical Cracks with Rust Stains on Reinforced Concrete Pile, US 278 EBL over MacKay Creek. Collins Project No Appendix B

38 Over MacKay and Skull Creek Photograph ft by 1 ft Spall on the Bottom of the Beam 6, Span 29, US 278 EBL over MacKay Creek. Photograph ft by 1 ft Spall on the Bottom of the Beam 6, Span 29, US 278 EBL over MacKay Creek. Collins Project No Appendix B

39 Over MacKay and Skull Creek Photograph 27. View of the Upstream Fascia, US 278 WBL over Skull Creek. Photograph 28. View of Typical Exterior Girder Condition, US 278 WBL over Skull Creek. Collins Project No Appendix B

40 Over MacKay and Skull Creek Photograph 29. View of Typical Interior Girder and Steel Cross Bracing Condition, US 278 WBL and EBL over Skull Creek. Photograph 30. View of Typical Main Channel Pier Configuration, US 278 WBL over Skull Creek. Collins Project No Appendix B

41 Over MacKay and Skull Creek Photograph 31. View of 2 ft long by 10 in Wide Spall Located on the East End of the Concrete Barrier, US 278 WBL over Skull Creek. Photograph 32. Typical Deck Joint Condition, US 278 WBL over Skull Creek. Collins Project No Appendix B

42 Over MacKay and Skull Creek Photograph 33. Typical Condition of the Intermediate Piers with Cracks at the Bottom, US 278 WBL over Skull Creek. Photograph 34. View of the Downstream Fascia, US 278 EBL over Skull Creek. Collins Project No Appendix B

43 Over MacKay and Skull Creek Photograph 35. Typical Crack With Rust Stains Located on the Bottom of the Pile Cap Footing for the Intermediate Piers, US 278 WBL over Skull Creek. Photograph 36. Typical Interior Girder and Steel Cross Bracing Condition, US 278 EBL over Skull Creek. Collins Project No Appendix B

44 Over MacKay and Skull Creek Photograph 37. Typical Deck Condition, US 278 EBL over Skull Creek. Photograph 38. Typical Deck Joint Condition, US 278 EBL over Skull Creek. Collins Project No Appendix B

45 Over MacKay and Skull Creek Photograph 39. Typical View of Intermediate Bents, US 278 EBL over Skull Creek. Photograph 40. Typical Shoreline Condition, US 278 WBL over Skull Creek. Collins Project No Appendix B

46 Appendix C SCDOT Reference Forms

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