FINAL_Arlington_Memorial_UW_Bridge_Inspection_Report_2-26-13.pdf

UNDERWATER BRIDGE INSPECTION REPORT

ARLINGTON MEMORIAL BRIDGE

MEMORIAL AVENUE OVER GWMP (WB) & POTOMAC RIVER

GEORGE WASHINGTON MEMORIAL PARKWAY

STRUCTURE NO. 3300-016P

INSPECTION TYPE: UNDERWATER

INSPECTION DATE: 12/10/2012 – 12/13/2012

Report prepared for: Report prepared by:

Federal Highway Administration Collins Engineers, Inc.

Federal Lands Bridge Office 745 Bluecrab Road, Suite B Bridge Inspection and Management Program Newport News, VA 23606 21400 Ridgetop Circle Sterling, Virginia 20166

Engineer of Record

STRUCTURE SUMMARY STRUCTURE NO. 3300-016P

ARLINGTON MEMORIAL BRIDGE U/W INSPECTION DATE: 12/10/2012 – 12/13/2012

INSPECTION TEAM & METHOD

Bridge No. 3300-016P carries Memorial Avenue over the George Washington Memorial Parkway

(Westbound) and the Potomac River. The bridge is a nine-span concrete arch structure consisting of six concrete piers and four concrete abutments. A steel bascule span is present between Abutments #2 and #3, and Abutments #1 and #4 each have a landside underpass and a channel side. Based on available design drawings, each pier rests on a spread footing founded on bedrock.

At the time of inspection, water level and high water mark was 1.5 ft. above the top of the 1st footing step and 5 ft. above the top of the 2nd footing step.

The underwater inspection was performed from December 10 through December 13, 2012. The underwater inspection was conducted by a three-person team consisting of a professional engineer-diver and Team Leader (John Loftus, P.E.), and two engineer-divers (Gregory Desing E.I.T. and Thomas

Cross). All inspections were performed using surface-supplied air diving equipment with hardwired communications and all operations were conducted from a 21 ft. skiff.

The underwater inspection consisted of a Level I visual and tactile examination on the substructure units from the waterline to the channel bottom with particular attention given to any observed areas of excessive deterioration or apparent distress. Level II inspections, which consisted of a detailed inspection at the waterline, mid-depth, and at the channel bottom, were conducted on 10 to 20 percent of the surface area of Piers #1 through #6 and on Abutments #1 through #4. At each of these locations, a 12-in wide band of marine growth was removed so that the substrate condition could be more closely examined. In areas of observed, or suspected, deficiencies, the substructure surface was sufficiently cleaned to determine the extents of the deficiency. The type of channel bottom material, the presence or extent of riprap, the presence or extent of drift and debris, and observed scour conditions were noted. Underwater photographs of the various defects/deficiencies were attempted with various forms of equipment, but were met with mixed success due to the presence of suspended sediment.

SUMMARY OF FINDINGS

Overall, the inspected substructures were found to be in fair condition (NBI Condition Rating =

5). The following paragraphs present the inspection findings for each substructure unit inspected.

Abutment #1

Abutment #1 was observed to be in satisfactory condition with no significant structural deficiencies observed. The abutment exhibited no significant changes in the substructure condition when compared to the 2008 Underwater Inspection findings. Random cracks, up to 1/16 in. wide, were present throughout the abutment and footing faces. The abutment was protected on the downstream (south) side by 9 to 12 in. diameter riprap which extended from the north side of the abutment outward towards Pier

#1 approximately 50 ft. The specific minor deficiencies of note observed in Abutment #1, and its associated footing, are presented in the following table:

Abutment #1 Deficiencies

Deficiency Location Comment Vertical crack 25’ south of the north end Up to 1/16” wide from springline to mudline with efflorescence and exudation present.

Vertical crack Midpoint of the abutment Up to 1/16” wide from springline to mudline with efflorescence and exudation present.

Vertical crack 20’ north of the south end Up to 1/16” wide from springline to mudline with efflorescence and exudation present.

Refer to Page 16 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Abutment #1.

Pier #1

Pier #1 was observed to be in satisfactory condition with no significant structural deficiencies observed. The pier exhibited no significant changes in the substructure condition when compared to the

2008 Underwater Inspection findings. Several areas of spall repairs (mortar patches) in the concrete footing faces were observed with several patches having failed. The concrete faces of the footing exhibited random, isolated 1 to 3 ft2 areas of poor consolidation with depths up to 1/8 in. Random cracks up to 1/16 in. wide were present throughout the concrete footing faces. The specific minor deficiencies of note observed in Pier #1 and its associated footing are presented in the following table:

Pier #1 Deficiencies

Impending mortar patch failure

South corner of pier on the east face 2 ft2 of impending patch failure, 8’ below top of 2nd footing step

Vertical crack 35’ north of the south nose on the east face

1/16” wide from top of 2nd footing step to mudline with efflorescence and exudation

Scour pocket 6’ north of north corner to north nose on west face

4’ max depth extends away from pier 4’

Horizontal/vertical crack

16’ north of south corner on the west face of pier

Up to 1/16” wide, from top of 2nd footing step extending horizontally for 6” to step edge and then 5” vertically down the face of the footing

Vertical crack 40’ north of south nose on west face 1/16” wide from top of 2nd footing step to mudline with efflorescence and exudation present

Vertical crack 35’ south of the north nose on west face Up to 1/16” wide from 14 ft. below high water mark to mudline with efflorescence and exudation

Area of Poor consolidation

3’ north of midpoint on the west face 5” horizontal by 3” vertical with up to 2” deep, 8’ below high water mark

Refer to Pages 17, 18 and 19 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Pier #1.

Pier #2

Overall, Pier #2 was found to be in fair condition with exposure and isolated undercutting of the tremie seal on the north nose and west face. A comparison with the 2008 Underwater Inspection findings revealed tremie seal exposure along the east and west pier faces where no previous exposure was reported. The seal exposure along the east face of the pier was 60 ft. horizontally by up to 5.25 ft.

vertically, and along the west face the seal exposure was 105 ft. horizontal by up to 4 ft. vertical.

The areas of undercutting were up to 3 ft. vertical (height) and extended under the seal up to 6 ft.

The surfaces of the tremie seal, within the areas of undercutting, exhibited moderate to heavy abrasion with moderate scaling up to 1/2 in. deep. Random, hairline to 1/8 in. wide cracks, were observed throughout the horizontal and vertical concrete faces of the footing. The concrete footing faces contained random formwork voids which varied in shape and size but were generally 4 to 5 ft. horizontal by 8 to 10

in. vertical by 1 to 3 in. deep. The specific minor deficiencies of note, including undercutting, observed in

Pier #2, its associated footing, and tremie seal, are presented in the following table:

Pier #2 Deficiencies

Vertical crack 6’ south of the north corner on the east face Up to 1/16” wide from 2nd footing step to mudline with efflorescence and exudation present

Vertical crack 30’ north of the south nose on the east face

Up to 1/16” wide from 2nd footing step to mudline

Area of poor consolidation

North corner of the east face 10” diameter area, up to 4” deep, 10’ below high water mark

Impending mortar patch failure

10’ north of the south corner on east face 8’ diameter area of impending patch failure, centered 10’ below high water mark

Tremie seal exposure North nose to 4’ north of midpoint on east face

Exposed horizontally up to 4’ from pier face with up to 5.25’ max vertical exposure

Scour pocket At north nose on east face 2.5’ max depth extends away from pier 10’

Vertical crack with spalling

Midpoint of west face Hairline to 1/16” wide, 6’ vertical with 12” with spalling around the edges up to 1” deep from top 2nd footing step to top of tremie seal

Vertical crack 4’ north of the south corner on west face Up to 1/8” wide, 13.5’ below high water mark to mudline

Void Midpoint of west face 1.5’ horizontal by 2.5’ vertical by 3’ deep with no exposed reinforcing

Tremie seal exposure North nose to 10’ north of south corner of pier on west face

Exposed horizontally up to 4’ from pier face with up to 4’ max vertical exposure

Tremie seal undercutting

Extending from north corner south 15’ on west face

Max. height of 1’ and max. depth of 2’ into seal

Tremie seal undercutting

Extending from midpoint of the north nose westward 15’

Max. height of 3’ and max. depth of 6’ into the seal

Refer to Pages 20, 21 and 22 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Pier #2.

Pier #3

Pier #3 was observed to be in fair condition with exposure and undercutting of the tremie seal along the north nose, and east and west faces. A comparison with the 2008 Underwater Inspection findings revealed tremie seal exposure along the east and west pier faces where no previous exposure was reported. The seal exposure along the east face of the pier was 78 ft. horizontally by up to 3.25 ft.

vertically, and along the west face the seal exposure was 20 ft. horizontal by up to 2 ft. vertical.

The undercutting was up to 3 ft. vertical (height) and extended under the seal up to 6 ft. The surfaces of the tremie seal, within the limits of the undercutting, exhibited moderate to heavy abrasion with moderate scaling up to 1/2 in. deep. Areas of poor consolidation and light scaling were noted around several of the vertical construction joints within the footing face. The concrete footing faces contained random formwork voids which varied in shape and size but were generally 4 to 5 ft. horizontal by 8 to 10

in. vertical by 1 to 3 in. deep. The specific minor deficiencies of note, including undercutting, observed in

Pier #3, its associated footing, and tremie seal, are presented in the following table:

Pier #3 Deficiencies

Tremie seal undercutting

North nose to 13’ south of north corner of pier

Max. height of 3’ and max depth of 6’ into the seal

Vertical crack with spalling

15’ north of south edge on east face Up to 1/8” wide with spalling along length up to 4” wide and 1” deep from top of 2nd footing step to mudline

Vertical crack 8’ south of the north corner on east face Up to 1/8” wide, from the top of the 2nd footing step to mudline with efflorescence and exudation

Vertical crack 5’ north of the south nose on east face Up to 1/16” wide, 20’ below high water mark to mudline with efflorescence and exudation

Vertical Crack with section loss at vertical construction joint

Midpoint of the east face Crack is up to 1/8” wide with efflorescence and exudation, section losses are 2” wide with up to 1” max. depth, from the 2nd course of stone from bottom to top of tremie seal

Section loss at vertical construction joint

6’ south of north corner on east face Up to 7” wide, up to 1” deep, top of 2nd footing step to 20’ below high water mark

Tremie seal exposure North nose to 14’ south of midpoint on east face

Exposed horizontally up to 4’ from pier face with up to 3.25’ max vertical exposure

Tremie seal exposure North nose to north corner of pier on west face

Exposed horizontally up to 3’ from pier face with up to 2’ max vertical exposure

Tremie seal undercutting

North nose to north corner of pier Max. height of 2.5’ and max depth of 4’ into the seal

Vertical Crack with section loss at vertical construction joint

5’ north of midpoint on west face Crack is up to 1/16” wide, with section losses of 4” wide with up to 1” max. depth 8.5’ below high water mark to the mudline

Vertical crack 30’ south of the north corner on west face 1/8” wide, from 2nd footing step to the mudline

Area of light scaling 13’ north of south corner on west face 6’ diameter area with up to 1/8” deep, 7.5’ below high water mark

Section loss around vertical construction joint

30’ north of south corner on west face Up to 5” wide, up to 1” deep, 5.5’ below high water mark to 19.5’ below high water mark

Areas of severe scaling Midpoint of west face Two areas, 4’ horizontal by 2’ vertical by 1”-2” deep, centered 8.5’ below, high water mark

Refer to Pages 23, 24 and 25 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Pier #3.

Abutment #2

Abutment #2 was observed to be in satisfactory overall condition with no significant structural deficiencies observed. The abutment exhibited no significant changes in substructure condition when compared to the 2008 Underwater Inspection findings. The vertical face of the 2nd footing step on the west face of the abutment footing was chamfered and extended at an angle downward towards east face of

Abutment #3. A pipe and cable well void was located in the angled face of the footing on the west side of the abutment, 20 ft. south of the north corner. The void was located approximately 1 to 2 ft. above the channel bottom and measured approximately 6 ft. horizontal by 4 ft. vertical with over 6 ft. of depth. In addition to the void, the concrete footing faces contained random formwork voids which varied in shape and size but were generally 4 to 5 ft. horizontal by 8 to 10 in. vertical by 1 to 3 in. deep

Eleven, 16 in. square concrete piles were present approximately 7 ft. west of the west face of the abutment and projected above the mudline 6 to 7 ft. Refer to Page 26 and 27 of 46, in the Substructure

Drawings Section, for detailed underwater inspection notes pertaining to Abutment #2.

Abutment #3

Abutment #3 was observed to be in overall fair condition with tremie seal exposure along the east and west faces and undercutting along the west face of the seal. A comparison with the 2008 Underwater

Inspection findings revealed tremie seal exposure along the east pier face where no previous exposure was reported. The seal exposure along the east face of the pier was 65 ft. horizontal by up to 4ft. vertical.

Similarly, the comparison revealed the tremie seal along the west face of the abutment to have a horizontal exposure increase of 20 ft. in (75 ft. in 2008 to 95 ft. in 2012) with the previously reported vertical exposure of 4 ft. remaining consistent with the 2008 inspection. In addition, the exposed seal along the north nose of the abutment was observed to have incurred undercutting since the 2008

Underwater Inspection. This previously unobserved area of undercutting was 6 in vertical (height) and extended under the seal up to 18 in. The surfaces of the tremie seal within the limits of the undercutting exhibited moderate to heavy abrasion with moderate scaling up to 1/2 in. deep. The vertical face of the 2nd footing step on the east face of the abutment was chamfered and extended at an angle downward towards the west face of Abutment #2. Random cracks, up to 1/8 in. wide, were present throughout the concrete and masonry faces. An additional step was observed extending outward on the north side of the abutment.

The top of the step was approximately 38 ft. below the high water mark and extended outward (north) from the north abutment face, 7 ft. and 4 ft. on the northeast and northwest corners of the footing, respectively.

As previously stated, tremie seal exposure was present along the east and west faces of the abutment with the seal being located below the 2nd footing step. The exposed surfaces of the tremie seal, outside the limits of the above-reported undercutting, exhibited moderate to heavy abrasion with moderate scaling up to 1/2 in. deep. Random areas of scaling and section loss were observed in the concrete surfaces of the abutment. The concrete footing faces contained random formwork voids which varied in shape and size but were generally 4 to 5 ft. horizontal by 8 to 10 in. vertical by 1 to 3 in. deep.

Eleven, 16 in. square concrete piles were present approximately 7 ft. east of the east face of the abutment and projected above the mudline 6 to 7 ft. The specific minor deficiencies of note, including undercutting, observed in Abutment #3, its associated footing, and tremie seal, are presented in the following table:

Abutment #3 Deficiencies

Tremie seal exposure

15’ south of north corner to 20’ north of south corner on east face

Exposed horizontally up to 7’ from pier face into the channel with up to 4’ max. vertical exposure

Vertical crack 27’ south of north corner on the east face Up to 1/16” wide, from the top of the 1st course of stone above the 1st footing step to 19’ below high water mark

Vertical crack 15’ south of the midpoint on the east face Up to 1/8” wide, from the top of the 2nd footing step to 18’ below high water mark with efflorescence and exudation.

Vertical crack 20’ north of south corner on the east face 1/16” wide, from the top of the 2nd footing step to 12’ below high water mark

Loosely formed concrete

North corner on the east face 6’ horizontal by 5’ vertical by 2’ deep, six 1” diameter reinforcing bars exposed up to 1.5’ with heavy corrosion and 10% section loss, at top of 2nd footing step

Scaling 30’ south of the north corner on east face 5’ diameter area, up to 1/2” deep, centered 5’ below high water mark

Tremie seal exposure

North nose to 20’ north of south corner on the west face

Exposed horizontally up to 4’ from pier face with up to 4’ max.

vertical exposure

Tremie seal undercutting

North corner of pier on west face and extends north 6’

Max. height of 6” and max. depth of 18” into the seal

Vertical crack 12’ south of north nose on west face Up to 1/16” wide, from the top of the 2nd footing step to 18’ below high water mark with efflorescence and exudation

Vertical crack 6’ south of the north corner on the west face 1/8” wide, from the top of the 2nd footing step to mudline with

Vertical crack 20’ south of north corner on west face 1/16” wide, from the top of the 1st footing step to 28’ below high water mark

Vertical crack 26’ south of north corner on west face 1/16” wide, from 25’ below high water mark to mudline with efflorescence and exudation.

Vertical crack 2’ north of midpoint on west face 1/8” wide, from top of 2nd footing step down to top of tremie seal

Vertical crack 10’ south of midpoint on west face 1/16” wide, from top of 2nd footing step to 19’ below high water mark with efflorescence and exudation

Vertical crack 25’ north of south corner point on west face 1/16” wide, from top of 2nd footing step to 31’ below high water mark with efflorescence and exudation

Refer to Pages 28, 29 and 30 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Abutment #3.

Pier #4

Pier #4 was found to be in satisfactory condition with no significant structural deficiencies observed. A comparison with the 2008 Underwater Inspection findings revealed the tremie seal along the east face of the pier to have 28 ft. of intermittent, horizontal exposure which was not observed during the

2008 inspection. The exposed surfaces of the seal exhibited moderate to heavy abrasion with moderate scaling up to 1/2 in. deep. Although horizontal exposure was present, no measureable vertical exposure of the tremie seal was observed.

Isolated vertical cracks, up to 1/16 in. wide, were present throughout the concrete footing faces.

One vertical construction joint on the east face was observed to be open 1/8 to 3/16 in. and another on the west face was observed to have a 4 in. wide by up to 1 in. deep area of section loss along its length. The specific minor deficiencies of note observed in Pier #4, its associated footing, and tremie seal, are presented in the following table:

Pier #4 Deficiencies

Vertical crack South nose 1/16” wide, from top of 2nd footing step to 11.5’ below high water mark with efflorescence and exudation

Vertical crack with spalling

35’ north of the south corner on east face 1/16” wide, spalls are 3” vertical by 1” deep, from 2nd footing step to mudline with exudation and efflorescence

Vertical crack 10’ north of midpoint on east face 1/16” wide from 18.5’ below high water mark to mudline with efflorescence and exudation

Vertical crack 10’ north of the north corner on east face 1/16” wide, from top of 2nd footing step to mudline with efflorescence and exudation

Vertical crack 2’ south of the north corner on east face 1/16” wide, from top of 2nd footing step to 18.5’ below high water mark

Opening in vertical construction joint

5’ north of midpoint on east face 1”-2” long areas within the upper 4’ of joints with openings 1/8”- 3/16 “ wide, from top of 2nd footing step to mudline

Tremie seal exposure North nose to 28’ south of north nose on east face

Top of seal intermittently exposed

Vertical crack 12’ north of midpoint on east face Hairline wide, from top of 2nd footing step and extending downward 16”

Vertical crack 10’ south of midpoint on east face Hairline wide from top of 2nd footing step to mudline

Vertical crack 14’ north of south corner on east face Hairline to 1/16” wide from top of 2nd footing step to mudline with efflorescence and exudation

Void Centered 12.5’ south of north nose on east face

5’ horizontal by 12”-14” vertical by 4”- 6” deep, 30’ below high water mark with no exposed reinforcing

Impending mortar patch failure

North nose 20” horizontal by 24” vertical, centered 16” below 2nd footing step

Section loss along vertical construction joint

3’ north of midpoint on west face 4” wide by 9’ vertical by up to 1” deep from top of 2nd footing step to 15’ below high water mark

Vertical crack 10’ south of south corner on west face 1/16” wide, from 15’ below high water mark to mudline with

Vertical crack 10’ south of north corner on west face 1/16” wide, from 15’ below high water mark to mudline with efflorescence and exudation

Vertical crack 12’ south of the midpoint on west face 1/16” – 1/8” wide, from top of 2nd footing step to 24.5’ below high water mark

Vertical crack through construction joint with section loss

28’ south of north corner on west face Up to 1/16” wide, loss up to 4’ long, 1” deep, from top of 1st footing step to mudline

Refer to Pages 31 and 32 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Pier #4.

Pier #5

Pier #5 was observed to be in satisfactory condition with no significant structural deficiencies observed. The pier exhibited no significant changes in substructure condition when compared to the 2008

Underwater Inspection findings. Isolated vertical cracks, up to 1/8 in. wide, were observed through the concrete footing faces. The concrete footing faces exhibited random formwork voids varying in size from

4 to 5 ft. horizontal by 8 to 10 in. vertical by 1 to 3 in. deep. The specific minor deficiencies found in Pier

#5 and its associated footing is presented in the following table:

Pier #5 Deficiencies

Vertical crack 20’ south of the north corner on east face Up to 1/16” wide, from top of 2nd footing step to mudline Vertical crack 6’ south of midpoint on east face 1/16” wide, from 3’ above mudline to mudline Vertical crack 10’ north of south corner on east face 1/16” wide, from top of 1st footing step to top of 2nd footing step Vertical crack 30’ south of north corner on west face 1/8” wide, from top of 2nd footing step to mudline with efflorescence and exudation present

Refer to Pages 33 and 34 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Pier #5.

Pier #6

Pier #6 was observed to be in satisfactory condition with no significant structural deficiencies observed. The pier exhibited no significant changes in substructure condition when compared to the 2008

Underwater Inspection findings. The concrete pier and footing faces exhibited random formwork voids varying in shape and size but were generally 4 to 5 ft. horizontal by 8 to 10 in. vertical by 1 to 3 in. deep.

Refer to Pages 35 and 36 of 46, in the Substructure Drawings Section, for detailed underwater inspection notes pertaining to Pier #6.

Abutment #4

Abutment #4 was observed to be in satisfactory condition with no significant deficiencies observed. The abutment exhibited no significant changes in the substructure condition when compared to the 2008 Underwater Inspection findings. The abutment was protected along the face of the abutment and on the upstream and downstream ends by 6 to 9 in. diameter riprap which extended from the north and south ends approximately 10 ft. The footing step was exposed along the full length abutment with a maximum vertical exposure of approximately 1 to 2 ft. Refer to Page 37 of 46, in the Substructure

Drawings Section, for detailed underwater inspection notes pertaining to Abutment #4.

Channel Bottom

The channel bottom varied in consistency between the abutments and the piers. The faces of

Abutments #1 and #4 were lined with 6 to 9 in. diameter riprap along the channel bottom. Piers #1 through #6, and Abutments #2 and #3, were observed to have river bottom material consisting of exposed bedrock around the upstream noses and silty clay, having probe rods penetrations of up to 2 ft., primarily around the east and west footing faces and the downstream noses. Random pockets of small diameter gravel and 6 to 12 in. diameter riprap were observed around the piers and Abutments #2 and #3.

Timber debris, up to 12 in. diameter, was scattered across the river bottom between the piers and

Abutments #2 and #3. Timbers are randomly located along the piers and abutments, within the channels, and at the upstream and downstream noses of the piers and abutments, and appear to be the remnants of an abandon fendering system.

Due to the lack of complete sounding data along the bridge and around the piers (previous soundings were incomplete and dated to the early 1990’s), no adequate comparison could be made to ascertain any changes in the river bottom profile. However, a comparison of soundings conducted during this inspection to those of the previous 2008 inspection show evidence of scour around the upstream

(north) nose of the piers and infill around the downstream noses of the piers. The water depths at the pier noses as compared to the 2008 soundings were found to have increased up to 9.8 ft., possibly due to occurrences of various storm events between 2008 and December 2012.

Evaluations and Recommendations

The substructure units of the Arlington Memorial Bridge were observed to be in fair to satisfactory condition with tremie seal exposure and isolated undercutting, construction-related structural defects and age-related structural deficiencies including cracks, spalls, failing patches, voids, poor consolidation, scaling, and isolated section loss along joints. Based on a comparison with the 2008 report, these conditions have remained virtually unchanged since that time and currently exhibit no signs of movement or further degradation. There were a few defects and deficiencies which were not reported in the 2008 Underwater Inspection Report; however, the scope of the 2012 Underwater Inspection required a higher percentage of Level II inspection and, consequently, more surface coverage during the inspection. In light of the inspection findings and comparisons with previous underwater inspection findings, no structural repairs are recommended at this time. It is, however, recommended that the structural conditions of the substructure be monitored at intervals not exceeding 60 months.

The scour and tremie seal exposures observed around Pier #1, #2, #3, Abutment #3, and Pier #4 has increased since the 2008 Underwater Inspection; however, available design drawings define the substructure footings as being founded on bedrock. Adding to the scour and tremie seal exposure at Pier

#2 and #3 was undercutting of the tremie seal at the bedrock interface. The areas of undercutting were not visible during the 2008 Underwater Inspection; however, water depths have increased around these substructures since that time due to scour from storm events and have exposed the seal to bedrock interface. The scour, tremie seal exposure, and undercutting, although appreciably changed since the

2008 Underwater Inspection, does not adversely affect the stability of the footings as they are founded on bedrock. In light of the inspection findings and available design drawings, no additional investigation or analysis is required at this time, however, it is recommended that scour countermeasures be installed around Piers #2 and #3 and Abutment #3 to prevent further scour, exposure, and undercutting of the tremie seal.

Regarding recommendations for the abandoned concrete piles along Abutment #2 and #3, navigational charts obtained from NOAA’s Office of Coast Survey show that amount of vessel traffic, and consequently the vessel sizes, would be limited due to the vertical clearances of bridges immediately upstream and downstream of the Arlington Memorial Bridge. Furthermore, the Mean Low Water depth around the piles is approximately 22 ft., resulting in an unobstructed water depth of 15 to 16 ft. above the top of the piles, which would most likely be adequate draft for the limited vessel sizes navigating the

Potomac within the immediate reaches of the Arlington Memorial Bridge. Based upon the inspection findings, and available NOAA information presented above, removal of the piles is not warranted or recommended at this time.

Lastly, the timber present along the channel bottom between the piers and/or abutments is relatively scattered and does not appear to be contributing to channel bottom scour at this time. Although the timber debris is not a significant impact with regards to scour at this time, leaving the debris untouched could increase future scour potential by providing a mechanism, or starting point, for the accumulation of debris during flood events. In light of the potential for timber debris accumulation during flood events, it is recommended that the existing, scattered timber debris be removed from the channel bottom.

Inspection Team Leader: QA/QC Review:

2/25/2013 2/25/2013

John Loftus, P.E. Date Charles H. Conrad, P.E. Date

SUBSTRUCTURE DRAWINGS

PHOTOGRAPHS

PHOTOGRAPHS STRUCTURE NO. 3300-016P

PHOTO #1 – GENERAL VIEW OF SOUTH (DOWNSTREAM) SIDE, LOOKING

NORTHWEST

PHOTO #2 – WEST ELEVATION OF ABUTMENT #1 (EAST ABUTMENT)

PHOTO #3 – WEST ELEVATION OF PIER #1

PHOTO #4 – WEST ELEVATION OF PIER #2

PHOTO #5 – WEST ELEVATION OF PIER #3

PHOTO #6 – WEST ELEVATION OF ABUTMENT #2

PHOTO #7 – WEST ELEVATION OF ABUTMENT #3

PHOTO #8 – WEST ELEVATION OF PIER #4

PHOTO #9 – WEST ELEVATION OF PIER #5

PHOTO #10 – WEST ELEVATION OF PIER #6

PHOTO #11 – EAST ELEVATION OF ABUTMENT #4 (WEST ABUTMENT)

PHOTO #12 – TYPICAL VIEW OF A CRACK UP TO 1/8” WIDE, WEST FACE OF PIER

#2 AT 4 FT. FROM SOUTH CORNER

PHOTO #13 – TYPICAL VIEW OF A CRACK UP TO 1/16” WIDE WITH

EFFLORESCENCE AND EXUDATION, THE EAST FACE OF PIER #3 AT 5 FT.

NORTH OF SOUTH NOSE

PHOTO #14 – TYPICAL VIEW OF MARINE GROWTH ON SUBMERGED SURFACES,

EAST FACE OF PIER #3

PHOTO #15 – TYPICAL VIEW OF THE CONDITION OF SUBMERGED CONCRETE

SURFACES AFTER LEVEL II CLEANING, EAST FACE OF PIER #3

PHOTO #16 – VIEW OF TREMIE SEAL UNDERCUTTING AT THE NORTH NOSE OF

PIER #2