Silver Spring Transit Center - Construction Problems and Oversights
Silver Spring, Maryland
Stephanie Snider, B.S. Civil Engineering, Pennsylvania State University Architectural Engineering M. Eng. Student Fall 2015

Figure 1: Panoramic View of the SSTC (courtesy of Montgomery County DGS)


The Paul S. Sarbanes Silver Spring Transit Center, also referred to as SSTC, is a three level transit facility located adjacent to the Red Line Silver Spring station. The transit center was built by Montgomery County and then operated by Washington Metropolitan Area Transit Authority (WMATA or Metro) with the hope to integrate private and public transit. Plans for this state of the art transit center started in April 1996 and was projected to be completed in 1998. Many delays pushed the ground breaking of this project to September 2008 with completion expected in late 2010. At this point in time the SSTC was expected to cost $75 million of public funds. Problems soon began including utility relocation issues, contaminated soil and excavation hitting bedrock all of which created significant project delays. In 2010, concerns were raised about the concrete slab thicknesses and concrete cracking. By 2011 the county decided to fund a structural investigation which found additional concrete and structural problems. Many structural repairs had to be made before the SSTC could be safely operated. On September 20, 2015 the Paul S. Sarbanes Silver Spring Transit Center was finally opened; nearly 5 years after the project's original projected completion date and millions over budget.

The project team included Zimmer Gunsul Frasca Architects (architect), Parsons Brinckerhoff (project engineer), Foulger Pratt Contractor (general contractor), Robert B. Balter Company (project inspector), and Montgomery County Government Department of General Services (manager). The project team will be referred to by role.

Construction and Warning Signs
Excavation began for the main structure on September 26, 2008 and lasted for almost two years due to utility relocation difficulties and complications from contaminated soil and bedrock. During this two year delay, a county building inspector with the Department of Permitting Services (DPS) questioned if the post tensioning cables within the slabs and girders would cause cracking. During a meeting held to discuss the matter the project engineer stated that the movement from the post tensioning process was minimal and they did not anticipate cracking and added that the concrete contractors would be consulted. The concrete contractors were only able to give a qualitative review since they were not allowed access to the design data. In their response memo they said they had no previous experience with a project with this geometry to use as a guide but the project engineer’s analysis has the correct approach to the problem and should be acceptable (KCE 2013 b).
Figure 2: Concrete deck cracks (courtesy of KCE)

Finally, concrete pouring begins in August 2010. By late October, the project engineering notified the manager that concrete cracks had formed on the recent pours which were not consistent with typical concrete shrinkage. He did not believe they cracks were a major structural concern but a long term maintenance concern and full evaluation of the cracking should be conducted (KCE 2013 b). Figure 2 shows some of the deck cracks highlighted by recent rain water. The county was notified by workers on the project that they believe the concrete slabs were too thin but concrete pouring continued through the winter. Later the report from KCE would state that the concrete pours during these winter months were done without consideration of the cold weather curing requirements.

In January 2011, the county publicized that the transit center opening will be delayed until December of that year due to the initial excavation complications. It would take almost a year for the concrete problems to be shared with the public. The county funds a structural inspection of the transit center in June 2012. The inspection found many portions of concrete deck were either too thin or too thick. There were also a few locations where reinforcing steel was exposed. One of these locations is shown in Figure 3 below. When the general contractor was asked to comment on the investigation findings he stated “The frame itself is structurally sound, the question is does it satisfy what the county thought they were buying. Our contention right now is yes.” (Kraut 2012). In January 2013, the general contractor even files a claim against the county for the delay of the project (Action Committee for Transit). March 19, 2013, structural consultants, KCE, issues their report which concluded multiple parties were responsible for SSTC many failures.

Figure 3: Reinforcing steel exposed due to insufficient concrete cover (courtesy of KCE)

Structural Inspection & Repairs

Montgomery County retained KCE Structural Engineers to conduct a document review and structural evaluation of the SSTC. Walter P Moore, and Wiss, Janney, Elstner Associates were retained by KCE to assist with the process.

Design Review & Analysis

The construction documents showed a lack of communication and coordination of construction phases and design elements during the design process. This deficiency in project organization is highlighted by numerous interference issues including:
  • Electrical and other embedded items interfering with reinforcing bars and posttensioning
  • Mild reinforcing steel interfering with posttensioning and posttensioning tendons interfering with mild reinforcing steel
  • Slab geometry and drainage slope
(KCE 2013a)
The original design had various errors in the design of post tension members. The induced post tension forces were greater than the total weight of the concrete members. This equilibrium discrepancy overbalanced the structure and caused cracking. Stresses from the initial post-tensioning process and the restraint forces were not accounted for in the design. Numerous elements were under designed and therefor unable to resist shear and torsion forces. The design also did not follow the stringent WMATA standards required by the building permits and contract. The structure as-built did not meet the 2003 edition of the International Building Code or the WMATA Manual of Design Criteria (KCE 2013a).

Testing & Results

A structural analysis was performed using both the as-designed and the as-built conditions. Field investigation testing was used to determine the structural integrity of the SSTC superstructure.

Nondestructive Testing

Ground Penetrating Radar (GPR)

GPR sends a pulse of radio frequency to the steel reinforcement placement. This test showed that in several typical slabs tendons had less than 2” of concrete cover and in one instance on level 330 the tendon was missing. Both pour strips located on Level 330 did not have post-tensioning tendons and the West Pour strip of Level 330 was missing reinforcing steel in the N-S direction. The original contract drawings contained these tendons and reinforcement steel. However, the subcontractor shop drawings were missing these elements but were still approved by the project engineer. Of the surveyed members, GPR found 60 beams where the tendon location differed from the design location by more than the ACI placement tolerance. Each of the surveyed girders had tendon segments that located outside the ACI placement tolerance from the original profiles. A number of columns were also investigated with GPR to determine the amount of concrete cover of the reinforcing steel. The test showed concrete cover ranging from 0.3” to >3” with an average of 0.9”. The minimum concrete cover according to ACI is 2 inches (KCE 2013a).

Impulse Response Testing
Impulse response testing is used to determine condition of the concrete qualitatively by hitting the concrete with a hammer and measuring the impulse applied to the surface and then elements response. This testing was performed on sections of decking on levels 330 and 350. Locations were chosen based on surface cracks and exposed tendons. The purpose was to determine if delaminations (separation of concrete layers) occurred in these locations under the surface. The test did not detect any internal delaminations in the tested areas (KCE 2013a).

Impact Echo Testing

Impact echo testing uses low-strain stress waves to determine the width and depth of cracks in the concrete that are so small they almost cannot be seen with the naked eye. These cracks must be measured because they will have a large impact on the long-term durability of the structure. Tested cracks had widths that varied from 1/200th of an inch to 1/64th of an inch and depths ranging from 0.5 inches from the top to cracks through the full slab depth. The average depth of these cracks was 5 inches (KCE 2013a).

Destructive Testing

Inspection Openings

Openings are cut in to the concrete to observe the condition and location of post-tension sheathing and tendons. These openings are also used to confirm data given by GPR. The average size of the openings was 12x12 with varying depths depending on depth of the steel. Grout samples were taken and then the holes were repaired. Of the 49 total inspection openings, nine locations had less than the minimum level of concrete cover and one location had a minor grout void in the tendon sheathing (KCE 2013a).

Concrete Cores

Concrete cylinders were removed from the slabs and sent to labs for strength testing, full petrographic examination and material testing for the purpose of calibrating a service life model. The first round of coring consisted of 68 samples. Once the initial compressive strength tests showed values lower than the design values, a second assessment of concrete strength needed to be performed. The second group had a total of 78 core samples. Compressive strength results varied from 3,850psi to 9,550psi. The design compressive strength was 6,000psi. Testing also reviled the water/cement ration was considerably higher than the approved design mix ratio. This is usually caused when water is added to the mixture on site. Petrographic examinations indicated high percentages of unhydrated Portland cement. This happens when concrete is poured in temperatures lower than 32 degrees. The hydration reaction is slowed by the cold to the point where water evaporates before cement has a chance to hydrate. The values found using these tests were compared to the concrete inspection values gathered by the project inspector. The concrete inspections completed during construction were not in accordance with any of the contract requirements. These subpar inspection procedures may have led to the test cylinders providing inflated situ materials strength values. Sampling and testing performed by the investigating engineers resulted in concrete compressive strength lower than the design requirements and sampling values stated during the construction phase (KCE 2013a).

The project inspectors were quick to respond to the KCE report. In a memo sent to the director of DGS they pointed out that they have records showing they acted in accordance with their contract and were not liable for the concrete problems. They also believed that the KCE report was not using all of the information provided by them to draw their conclusions. The memo addressed many statements made in the KCE report and attempted to highlight the report's inaccuracies (Balter 2013).


Necessary repairs include:
  • Remove and replace pour strip slabs on level 330 with properly designed pour strips
  • Increase combined shear and torsional capacity of noted post-tension beams and girders on levels 330 and 350
  • Provide a concrete overlay for the surface of the slabs on levels 330 and 350 to ensure long-term durability

(KCE 2013a)

This short list of repairs are the major problems and are generally stated. Each of these repairs encompasses many components and steps. This remediation process lasted close to 3 years and cost of $ 10.6 million (Office of the Inspector General 2014). The project designer was approached to design the repairs but when they failed to cooperate, KCE was asked to design the final repairs. The original general contractor performed the repair work under the watchful eyes of the KCE engineers (Markovs 2015). The project was finally completed and opened to the public on September 20, 2015 and cost a grand total of $141 million.



Project Timeline

11/26/2006 - Ceremony celebrates start of work on $75 million transit center and names it for Sen. Paul Sarbanes.
09/26/2008 - Groundbreaking for the main transit center structure.
10/21/2009 - Completion delayed from December 2010 to February 2011 due to utility relocation problems.
03/10/2010 - Cost of SSTC increases to $95 million to pay for excavation problems and completion is delayed till June 2011.
04/07/2010 - County building inspector asks whether design will cause concrete to crack on the bus deck.
05/11/2010 - Design engineer says cracking is not expected, but concrete contractors should be consulted before proceeding.
06/03/2010 - Concrete contractor says unique design means that past experience is no guide.
08/01/2010 - Concrete pouring begins.
10/28/2010 – First cracks reported to county.
01/26/2011 – County says excavation problems will delay the opening of SSTC till December 2011.
01/30/2012 - County-funded structural inspection finds more concrete problems.
10/04/2012 – Concrete problems need to be repaired increasing the cost of the project to $110 million and delays the project completion till August 2013.
01/18/2013 – General contractor files claim against county blaming them for the delay.
03/19/2013 - KCE Structural Engineers issue their report finding many parties at fault.
04/02/2013 - County appropriates an additional $7.5 million for legal and consulting expenses bringing the total cost to date to $117.5 million.
04/30/2014 - A new report warns of risk from falling concrete chunks unless interior beams and girders are reinforced. Opening is delayed till late 2014.
08/06/2014 - Structural repairs begin. Completion date pushed to 2015.
12/04/2014 – Repair costs increase the project cost to $141 million.
07/27/2015 - Structural repairs completed.
08/24/2015 - Montgomery County and WMATA sue design engineer, general contractor, and project inspector for $166 million in damages.
09/20/2015 – Paul S. Sarbanes Transit Center opens!

(Action Committee for Transit 2015)


Problems plagued the Paul S. Sarbanes Transit Center during every phase of the design and construction process. Some of these problems were unavoidable but most could have been corrected or avoided if the project team worked together and monitored the work appropriately.

The problems began during the design phase when critical forces within the structure were either overdesigned or overlooked. The design also did not meet the permitted WMATA standards which were required if WMATA was going to accept the final project. Poor coordination of project components caused many elements to interfere with each other. When concerns were raised about the design geometry causing concrete cracking, parities passed responsibility off on to others but the matter was not fully investigated at that time. Shop drawings were approved by the engineer of record without critical reinforcing steel. If these omissions and errors were caught during the design phase, millions of dollars could have been saved.

Once construction began, the focus seemed to be on the completion date not the quality of the work. Testing of the water/cement ratios of the concrete show that additional water was added, possibly to increase the workability of the concrete, even though this addition would put the final ratio over the acceptable level stated in the construction documents. As pouring continued though the cold winter months little attention was paid to the ACI cold weather curing requirements. These actions reduced the strength of the concrete and they could have been avoided if an outside authority was present to oversee the construction process.

Finally, when the structure was evaluated and found to be unsafe many of the parties involved either denied the problems existed or passed the responsibility off to someone else. The general contractor was adamant that the structure was structurally sound and that the project satisfied the contract with the county. The report from KCE stated the structure could continue to support construction loads but was too unsafe to be opened to the public. The project inspector insisted that they did everything that was required of them in the contract and nothing more.

In conclusion, many parties were responsible for the SSTC structural problems. The responsibility is shared by those who made the mistakes and by those who allowed mistakes to continue. The design was flawed, shop drawings and change orders were approved without analysis, and construction was allowed to continue when the concrete was compromised. Montgomery County and WMATA have filed a lawsuit against the project designer, general contractor and the project inspector for damages. These companies received a considerable amount of public funds to for their roles in this project, roles which they failed to complete.


Action Committee for Transit. (September 16, 2015). “The Silver Spring Transit Center – A History of Delay.” < **** > (October 2, 2015).
  • The action committee for transit for Montgomery County compiled a time line of SSTC project starting in 1993 when the idea for the project was first presented to the day it finally opened in 2015.

Balter, Lori. (April 22,2013). "Response to KCE Report Date March 15, 2013." < > (October 15, 2015).

KCE Structural Engineers, PC, Walter P Moore and Wiss, Janney, Elstner Associates, Inc. (March 15, 2013a). “Silver Spring Transit Center Structural Evaluation of Superstructure.” < **** > (September 17, 2015).
  • Prepared for Montgomery County. This report shows the results of the testing and analysis of the SSTC. Major problems included excessive concrete cracks, varying slab thicknesses and exposed post-tensioned ducts.

KCE Structural Engineers, PC, Walter P Moore and Wiss, Janney, Elstner Associates, Inc. (March 15, 2013b). “Silver Spring Transit Center Structural Evaluation of Superstructure - Attachments Volume II.” < > (September 17, 2015).

Kraut, Aaron (March 28, 2012)."Contractor claims Silver Spring Transit Center meets concrete specifications". < >(October 22, 2015)

Markovs, John P., Ashbarry, Trevor and Nussbaum, William D. (August 24, 2015). “Civil Action No. 408239 – V.” Circuit Court for Montgomery County, Maryland. < **** > (September 17, 2015).
  • This is the lawsuit filed with the Maryland court system. The defendants are charged with breach of contract and professional negligence. They are seeking compensatory damages.

Office of the Inspector General. (April 15, 2014). “Final Report of Inspection: Project Management Deficiencies in Constructing the Paul S. Sarbanes Silver Spring Transit Center.” Report # OIG-14-007. < **** >(October 2, 2015).
  • This report describes the analysis and recommendations presented in KCE’s analysis and Alpha Corp.

Orlin, Glenn. (March 29, 2013). Supplemental Appropriation and CIP Amendment. < **** > (October 4, 2015).
  • Council memorandums discussing the cost break down of the project and repairs.

Additional Resources

Alpha Corporation. (March 14, 2014). “Analysis of Project Controls.”< **** > (October 2, 2015).
  • This report highlights the project controls that should have identified the problems during construction but were not implemented properly.

Department of General Services (2015). "Paul S. Sarbanes Silver Spring Transit Center". Montgomery County Maryland.< > ( December 1, 2015).

Independent Advisory Committee. (April 21, 2014). “Status of the Silver Spring Transit Center.” < **** > (September 17, 2015).
  • The final report by the Independent Advisory Committee discusses the various problems that arose during construction, repair plans, scheduling and cost moving forward.

Whitlock Dalrymple Poston & Associates, Inc. (May 2, 2013). “Evaluation of Silver Spring Transit Center.” < **** > (September 17, 2015).
  • Prepared for Washington Metropolitan Area Transit Authority. WDP’s analysis of the SSTC’s deficiencies.