Engineers' Society of Western Pennsylvania

Location

337 Fourth Avenue
Pittsburgh, PA 15222

Phone: (412) 261-0710 Email: eswp@eswp.com Get Directions

Tuesday, July 19, 2022

Technical Sessions

ABC, Part 2 Session

Time: 1:30 PM – 3:00 PM

Session Chair: Bill Detwiler, P.E., TYLin, Coral Gables, FL
Room: 301/302

IBC 22-28: Superstructure Modules at Bridges 3-155 N&S over Broadkill River, Sussex County, DE
Fred Ophardt, P.E., Whitman, Requardt & Associates, LLP, Baltimore, MD

Time: 1:30 PM

The “Rehabilitation of Bridges 3-155 N&S” project consists of the superstructure replacement of two parallel five span steel beam bridges owned by the Delaware Department of Transportation along the SR 1 corridor, Delaware’s main north-south highway used to access the Delaware beaches. To meet a six-month construction schedule dictated by traffic demands, this project featured the use of prefabricated superstructure modules, precast concrete approach slab components, ultra-high performance concrete, and a polyester polymer concrete overlay.

IBC 22-29: Prefabricated Bridge Decks – Speed and Durability
Lawrence Rolwes, Jr. and Joshua Phillips, HNTB, Arlington, VA; Bill Manuel, HNTB, Charleston, WV

Time: 2:00 PM

Prefabricated bridge decks offer the flexibility to meet challenging construction schedules in both new and existing applications while also providing durability equal or better than traditional cast-in-place decks through incorporation of modern materials and details. Three projects are presented to showcase the versatility of the prefabricated deck concept with corresponding details: Rte. 52 over the Mississippi River in Louisiana, MO; West Virginia Parkways Authority bridge deck replacements; Rte. 120 over Pimmit Run in Arlington, VA.

IBC 22-30: Exploring Fiber-Reinforced Polymer Concrete for Accelerated Bridge Construction Applications
Carolyn Donohoe and Travis Thonstad, University of Washington, Seattle, WA

Time: 2:30 PM

This paper explores the use of fiber-reinforced polymer concrete (FRPC) as a closure pour material to connect adjacent prefabricated bridge elements. FRPC displays bond and tension strength comparable to UHPC and gains this strength in several hours. The mechanical and bond properties of FRPC were experimentally determined at several temperatures and ages. Using the collected data, an example joint configuration was developed, enabling comparison of FRPC with other closure pour materials in future ABC projects.

3:00 PM – Coffee Break

Alternate Delivery Methods Session

Time: 3:30 PM – 5:30 PM

Session Chair: Bill Detwiler, P.E., TYLin, Coral Gables, FL
Room: 301/302

IBC 22-31: CMAR Delivery of I-15 Virgin River Bridge No. 1 – Longest Steel Girder Span in Arizona
Jason Nauman, P.E. and Greg Lingor, HDR, Phoenix, AZ

Time: 3:30 PM

This $57 million Construction Management at Risk (CMAR) project will replace an existing 5-span haunched steel girder bridge, which is classified as structurally deficient and scour vulnerable, with a 3-span huanched steel plate girder bridge consisting of the longest steel girder span (340 feet) in Arizona. The presentation will highlight the effectiveness of the CMAR delivery method by providing an overview of the bridge layout, phasing and design elements that were CMAR influenced.

IBC 22-32: Optimizing Bridge Design and Construction through Collaboration
Kumar Ghosh, Jeremy LaHaye, and Dan Fitzwilliam, TYLin, San Diego, CA

Time: 4:00 PM

The replacement of the San Elijo Lagoon Bridge on the Interstate-5 uses the Construction Manager/ General Contractor (CM/GC) delivery method. Schedule, traffic impacts, environmental impacts and risk reduction were major considerations in involving the CM early on to seek input on construction staging, public outreach and traffic handling. Collaboration with the CM resulted in cost savings through foundation optimization and design details vetted by the CM that helped to reduce Change Orders during construction.

IBC 22-33: Hurricane Ida Emergency Repairs at the Route 22 Bridge over Middle Brook Wall Washout
Melissa Dawson, P.E., Eli D. Lambert III, P.E., Rama Krishnagiri, P.E., and Kwang Ro, P.E., WSP USA, Lawrenceville, NJ; Mohab Hussein, New Jersey DOT, Ewing, NJ

Time: 4:30 PM

Hurricane Ida was a deadly and destructive tropical storm that impacted New Jersey with flooding and tornadoes on September 1, 2021. A single span bridge in Bridgewater Township, Somerset County, NJ experienced severe flooding well exceeding 100-year design storm levels. Flood water from the stream and the surrounding area and upstream flood control structure overtopped the bridge with 8’ of water and a stepped, precast modular retaining wall on the western downstream side of the bridge was undermined and washed away. In addition, a 24” force main sewer ruptured and a major utility pole carrying about 1 ton of wires was undermined and leaning against the failed parapet. The ramp from Chimney Rock Road to Route 22 Eastbound was closed to traffic. The NJDOT and WSP team inspected the damage and immediately mobilized over the Labor Day weekend to develop a repair scheme. A design build approach was necessary to expedite immediate Emergency construction and secure materials. The sewer main was temporarily bypassed for repair and the utility pole relocated in two days. Demolition of the failed wall, parapet and moment slab followed as soon as safe access was available. A permanent wire mesh reinforced earth wall with precast concrete facing panels and concrete closure pour was recommended and ultimately installed to open traffic on the ramp and limit impacts to main line Route 22 traffic. The existing bridge abutment foundation was protected by an invert slab that survived the storm, however the downstream end was undermined for about 6’. Phase two of the project will include reconstruction of the existing embankments including installation of large riprap protection along the stream bank and armoring of the existing bridge shallow foundations at both the east and west embankment corners.

IBC 22-34: Rehabilitation of I-95 using the CM/GC Delivery Method
William Geschrei and David Nizamoff, Whitman, Requardt & Associates, LLP, Baltimore, MD

Time: 5:00 PM

The Delaware Department of Transportation is using the CM/GC delivery method to rehabilitate a 6-mile long stretch of I-95 in downtown Wilmington, DE. The project goals are to extend the useful service life of the interstate for at least 30 years, including 19 bridges and 11 entrance and exit ramps, while minimizing schedule risk to ensure the project, and its impact on traffic, can be completed in 2 years or less.

Back to Top

Cable Stayed Bridges Session

Time: 1:30 PM – 4:30 PM

Session Chair: Brian Kozy, Ph.D., P.E., Michael Baker International, Linthicum, MD
Room: 304/305

IBC 22-35: Gordie Howe International Bridge: Project Overview and Design Features
Barry Chung, AECOM, Tampa, FL; Antonio Martínez and Juan Navarro, Carlos Fernández Casado, SL, Madrid Spain; Steve Stroh, Aecom, Tampa, FL; Hugo Corres and Borja Regúlez Pérez, Fhecor, Madrid, Spain

Time: 1:30 PM

The Gordie Howe International Bridge, crossing the Detroit river between Windsor (Canada) and Detroit (USA), will be the longest main span cable stayed bridge in North America with a 853 m / 2800 feet main span and the longest main span cable stayed composite deck in the world. This paper provides a general overview and design features including foundation, tower, and superstructure, and highlights design challenges including aerodynamics, stay cable design, redundancy and durability.

IBC 22-36: Replacement of the Kosciuszko Bridge over Newtown Creek Phase 2 – Construction and Erection Engineering
Preston Vineyard, COWI, New York, NY

Time: 2:00 PM

This presentation focuses on the erection engineering challenges of constructing the Kosciuszko Phase 2 Cable Stayed Bridge (K-Bridge). The K-Bridge is a complicated structure erected in a highly constrained environment on an aggressive schedule. Erection of the bridge presented numerous technical challenges, including dramatic proximity to the completed Phase 1 Bridge, limited right-of-way access; the location of underground remnants of the original 1931 bridge foundation, and the presence of Newtown Creek.

IBC 22-37: A record breaking prestressed concrete extradosed bridge
Miguel Astiz, Carlos Fernández Casado S.L., Madrid, Spain; Marcos Sánchez, Arup, Dublin, Ireland

Time: 2:30 PM

The Rose Fitzgerald Kennedy Bridge spans the river Barrow with two 230 m long main spans. It is an extradosed bridge with three towers, and four spans and several approach spans to complete the 887 m length of the whole bridge. The design is the consequence of a very careful attention to the preservation of the landscape as well as to the durability of the bridge while considering all the specific challenges due to the service loads, wind effects on traffic, ship collision and fire events analysis as well as construction issues related to the extreme slenderness of the deck. Most of the details of this bridge were designed in order to comply with these constraints leading to a non-standard design from a purely engineering point of view but to a structure which is more friendly with the society and with the environment.

3:00 PM – Coffee Break

IBC 22-38: Collapse of the Chirajara Cable Stayed Bridge in Colombia
Thomas Murphy, Ph.D., P.E., S.E., Nohemy Galindez, Ph.D., P.E., Frank Artmont, Ph.D., P.E., Andrew Adams, P.E., and Maria Lopez, Ph.D., P.E., FACI, Modjeski and Masters, Inc., Mechanicsburg, PA

Time: 3:30 PM

On January 15, 2018, while under construction and with only 164’ left to connect the floorsystem at midspan, one of the towers of the Chirajara Bridge suddenly collapsed, destroying that part of the structure. The other tower remained standing, approximately in the same
construction stage as the collapsed tower. The Chirajara Bridge was located about 40 miles to the southeast of Bogota, Colombia. It was a cable-stayed bridge consisting of two diamond-shaped towers, with a main span length of 940’ and two 262’ long side spans.

Modjeski and Masters was engaged to conduct a forensic investigation into the collapse. The investigation included an in-situ inspection of the collapsed structure, analytical studies of the bridge and its capacity for the conditions immediately prior to the collapse and for the final condition of service, an evaluation of the original design, a review of the construction documentation and testing of the critical component materials. Based on all of the available data resulting from the investigation, the cause of the Chirajara tower collapse was determined to be a deficiency in the strength of the tower due to an incorrect design assumption regarding the resistance provided by its cross beam and the diaphragm between the tower lower legs. While the investigation identified several other issues with the design and construction of the bridge, no other factor was found to contribute significantly to the cause of the collapse.

IBC 22-39: Varvsbron: a Unique Cable-Stayed Pedestrian Bridge
Stephen James, BSc DipArch, Stephen James Architects, London, United Kingdom; Kilian Karius, Leonhardt, Andrä und Partner, Stuttgart, Germany

Time: 4:00 PM

‘Varvsbron’, an innovative cable-stayed structure represents state-of-the-art design in a location that is rich in industrial history.
Our paper charts the development of the bridge’s design, focusing particularly on how the team utilised advanced parametric modelling techniques, primarily used in the aircraft and automotive industry, to simultaneously confirm the final aesthetic form, address complex structural and buildability issues, and ultimately make this distinctive bridge both structurally efficient and buildable.

Lesson Learned Session

Time: 4:30 PM – 5:30 PM

Session Chair: Brian Kozy, Ph.D., P.E., Michael Baker International, Linthicum, MD
Room: 304/305

IBC 22-40: Route 6/10 Interchange Reconstruction: Design & Construction of an Urban Interchange using Design/Build
Brian Guzas, P.E., AECOM, Providence, RI; Daniel Deacon, Barletta Heavy Division, Canton, MA; Katie Scancarello, P.E., and Megan McMorris, P.E., AECOM, Boston, MA; Matthew Sprague, P.E., AECOM, Providence, RI

Time: 4:30 PM

Reconstruction of the Route 6 and Route 10 Interchange is the largest Design/Build Project in RIDOT history. Built in the 1950’s the interchange serves as a critical East-West regional link and was both structurally and functionally obsolete. The design and construction teams had to overcome many challenges with innovative solutions, including: challenging soils, bridge erection in a congested site, construction over/adjacent to AMTRAK, bridge constructability, and schedule flexibility during a global pandemic.

IBC 22-41: Fully Joint-less Continuous Steel Girder Structure – Update and improvements after 7 years in service
Michael Liona, P.E. and Rasmin Kharva, P.E., Hardesty and Hanover, LLC, New York, NY; Craig Ruyle, P.E., New York State DOT Region 11, Long Island City, NY

Time: 5:00 PM

This is a follow up to IBC Paper 13-15 presented in 2013. We will present an overview of the jointless details and how they have performed based on their real-world use over 7 years.

The Kew Gardens Interchange in Queens, NY is a complex urban interchange with four major highways, several at-grade roadways and multiple inter-roadway ramp connections. NYSDOT Region 11 has implemented a four Phase safety and operational improvement plan at this
complex interchange. As part of Phase 2 of that plan, the existing Northbound Van Wyck Expressway Viaduct was replaced as part of the proposed improvement and structural upgrade. This critical piece of New York City infrastructure is a major north-south travel route between NYC and the tri-state region leading to the JFK and La Guardia airports, carrying over 90,000 vehicles per day.

The structure was designed to be fully joint-less as opposed to the use of typical deck joints that would be used along the structure and/or at the abutments. The joints were eliminated with the development of special joint-less deck and approach slab details with the use of pressure relief joints. The new bridge is the longest joint-less, continuous steel curved structure in NY State: 800’ length, 4-spans: 191.6’/213.3’/213.3’/178.8’.

The bridge was completed and put into service in November 2014. Lessons learned from design through installation and how the joint-less details have performed after 5 years of high traffic volumes and heavy truck traffic. Detail improvements installed in 2020 and their 2-year performance will be reviewed.

Back to Top

Pedestrian/Special Purpose Bridges Session

Time: 1:30 PM – 5:30 PM

Session Chair: Jonathan McHugh, Gannett Fleming, Inc., Pittsburgh, PA
Room: 306/307

IBC 22-42: Steel Erection for the Margaret McDermott Pedestrian Bridges
Nicola (Nick) Greco, P.E., P.Eng., American Bridge Company, Coraopolis, PA; John Boschert, Steve Eads, and Dave Byers, Genesis Structures, Inc., Kansas City, MO

Time: 1:30 PM

Two 1,125 foot long arch pedestrian bridges were constructed in Dallas, Texas as part of the Trinity River Corridor improvement project. These bridges provide pedestrian access across the Trinity River at IH-30 and I-35E near downtown Dallas’ Central Business District. The intricate geometry of the arch, while visually dramatic, added significant complexity to the erection engineering. The paper will highlight the construction engineering and the means and methods developed for the project.

IBC 22-43: Designing the Pittsburgh Airport Terminal Front Bridge
Kevin O’Connor, HDR, Pittsburgh, PA; Michael Fitzpatrick, HDR, Irvine, CA

Time: 2:00 PM

The Pittsburgh International Airport is executing a $1.39 billion terminal modernization program to update and right-size the airport’s facilities. The new airport terminal will host 12-18 million travelers each year. On the front of that terminal will be a new two-level, 1,300-foot bridge. Most bridges are designed to carry travelers from point to point, this structure is designed to Improve the user experience for travelers beginning or ending their journeys and will serve as the entryway to both the departure and the arrival levels at the new terminal. The two-level stacked bridge over a commercial curb level at grade features through lanes for drivers, parking lanes for passengers arriving and departing, a sidewalk curb with bollards for protection as well as benches and planters designed as crash-worthy protective elements, ADA access ramps, and a suspended and lighted ceiling at the vestibules that provide entry points to the terminal.

Aspects of the design that will be covered in this presentation include, the design of shallow in-plane rectangular steel cross-girders supporting trapezoidal box-girders due to the requirement to match the height of the terminal floors, foundation restrictions due to underground tunnels, and vibration limits due to automated people mover trains in the tunnels, the use of round multi-column steel jacketed concrete piers as a threat protective measure with short struts between the columns, bollards within the bridge deck, benches and planters designed for crash protection, wayfinding signage within the bridge deck, and the incorporation of art onto the bridge abutments and barriers.

IBC 22-44: Changeable Wind Conditions Affecting Pedestrian Bridges
Pierre-Olivier Dallaire, Mark Istvan (presenter), RWDI Consulting Engineers & Scientists, Guelph, Ontario, Canada

Time: 2:30 PM

Tintagel Castle is among the most popular tourist destinations in England. Built in the 13th century it is a unique historical site on the windswept north coast of Cornwall. The castle’s location makes it difficult to access. Up until now it has been reached via an arduous approach involving many stairs which was difficult or impossible for people with mobility challenges. To improve accessibility to this historic site, an elegant cantilevered bridge was designed and constructed. The Tintagel Castle Bridge is unlike most pedestrian crossings as its design has two cantilevers that don’t quite meet, creating a small gap in the middle. Situated on a site that is prone to extreme weather, this presented an engineering challenge to ensure maximum stability.

This presentation will provide an overview of the engineering approach taken to overcome the climate and topographical conditions influencing design to ensure a safe and comfortable structure. Wind tunnel testing assessed numerous aspects of the bridge’s aerodynamic and
aeroelastic performance such as the susceptibility to flutter and vortex shedding. Through the example case study, participants will gain a better understanding of optimizing bridge designs to withstand wind and other environmental influences without developing undesirable
dynamic responses.

3:00 PM – Coffee Break

IBC 22-45: Outside of the Comfort Zone – When the Best Solution Makes a Client Uncomfortable
Jeremy LaHaye, P.E., Dan Fitzwilliam, P.E., and Robert Sokolowski, TYLin, San Diego, CA

Time: 3:30 PM

Pedestrian bridges provide vital links for society and allow for design expressions not readily adapted by vehicular bridges. The San Elijo Pedestrian Bridge is an example of a such a bridge. This pedestrian bridge in Encinitas California is a part of the $6 Billion Caltrans I-5 North Coast Corridor Project. Suspended from the newly constructed I-5/San Elijo Lagoon Bridge, this elegant structure provides a vital link between the bicycle and pedestrian trails in and around the San Elijo Lagoon and creates more travel choices for the community.

This presentation examines how the opportunities and constraints influenced the aesthetics and design of this unique cable supported structure. The architecturally striking design was developed with input from multiple stakeholders and resource agencies while keeping the design and site constraints in mind. This bridge is the first of its kind in California and required the application of key client management and design tools to allow for acceptance by Caltrans. These tools can be readily applied to a myriad of other project challenges that designers will
encounter on non-standard and complex bridge projects.

As designers continue to push the envelope on what is possible, it is imperative that we are prepared to present our ideas to clients in a manner that facilitates their approval of the design. Utilizing the San Elijo Pedestrian Bridge as an example, we will review the novel
engineering solutions required, the comments and concerns presented by Caltrans reviewers, and the tools used to obtain approval.

IBC 22-46: Design and Construction of the Robert L.B. Tobin Land Bridge
Matt Carter and Eric Brunning, P.E., Arup, New York, NY; Greg Tuzzolo, Stephen Stimson Associates, Boston, MA

Time: 4:00 PM

The Robert L.B. Tobin Land Bridge is a unique bridge that connects together two halves of the Phil Hardberger Park in San Antonio, Texas. The bridge provides a safe passage for animals to cross the six lane highway which bisects this important 330 acre nature reserve in the
suburbs of the city. The bridge is a unique saddle shape steel girder bridge with the form providing a natural path. This presentation will describe the development of the design and how it responds to the unique requirements of being an animal crossing. The presentation will also describe the construction and operation.

IBC 22-47: A Bascule Bridge Within a Bascule Bridge
Patrick Laux, P.E., S.E., WSP USA, Chicago, IL; Jamal Grainawi, P.E., S.E., WSP USA, Chicago, IL

Time: 4:30 PM

The Lake Shore Drive Bascule Bridge stands apart in Chicago for many reasons. Not only is it colossal in size, its location at the mouth of the Chicago River requires it to carry fourteen (14) total lanes of DuSable Lake Shore Drive traffic on two levels along with the Lakefront Trail. The originally constructed bridge was modifying in the 1980s to carry this trail on the bridge’s lower level in part by creating an opening in the eastern bridge houses. Consequently, trails users must navigate a narrow opening, approximately eight feet. Now with the Lakefront Trail more popular than ever, the City embarked on a plan to widen the trail to 20 feet to improve safety and accessibility for people walking, biking, and using assistive devices. The new bridge modification features a second opening through the bridge houses, new movable sidewalk pieces at each end, and 20-foot-wide cantilever brackets on the bascule bridge itself. The unique structure-type of these movable sidewalks made for a challenging design. Using a passive opening system facilitated by a linkage arm to the main bascule bridge, the movable sidewalk pieces serve as a bridge between the trail on the fixed structure to the bascule structure. The presentation will focus on the design of these ‘bascules within a bascule bridge’ as well as the various other movable bridge rehabilitation aspects of the project.

IBC 22-48: A Twist on Station Footbridge Design
Victoria Richardson, Arup, Pittsburgh, PA; Tom Osborne, Knight Architects, United Kingdom

Time: 5:00 PM

Seeking to improve both the passenger experience and the aesthetic quality of new station footbridges, the UK’s national rail operator have produced a catalogue of signature station footbridge designs. The catalogue contains the Ribbon footbridge, which is the focus of this paper.

The Ribbon footbridge is characterized through a simple but innovative approach to rotate the lift shaft through-30 degrees. In doing so the design offers significantly improved visibility of the lift from views along the platform, presenting an equal experience for all users of the station. Introducing rotation into the lift shaft design brought structural challenges to balance the connection design with facilitating quick construction during track closures.

As a truly parametric design, the Ribbon footbridge design can accommodate a variety of station layouts including single span options and larger multi-span arrangements. Station capacities vary so the design choice also includes stair width, deck width and lift capacities. This was achieved through an integrated design and analysis grasshopper script to quickly assess multiple configurations. To accommodate the matrix of options, the main deck consists of a U-frame through girder steel deck with inclined webs. The canopy and deck are separated into two independent ‘ribbons’. This provides shelter while passengers remain in the open air to move seamlessly between platforms.

The Ribbon footbridge is part of an innovative change to enhance the passenger experience and apply an adaptable, enduring and high-quality design to suit the diverse of local contexts across the rail network.

Back to Top

Workshops

W05: Delivering Under Pressure – Lessons Learned from Major Bridge Emergency Response and Rehabilitation Projects
John Dietrick, Michael Baker International, Cleveland, OH; Francesco Russo, PH.D., Russo Structural Services, Philadelphia, PA; Aaron Stover, Michael Baker International, Louisville, KY; Alicia McConnell, P.E., Michael Baker International, Chicago, IL; John Zuleger, P.E., SPRAT 3,  Michael Baker International, Cincinnati, OH; Rich Schoedel, Michael Baker International, Pittsburgh, PA

Time: 1:30 PM – 5:30 PM

This workshop will describe the efforts undertaken, under extreme pressure and public scrutiny, to successfully re-open major bridges that experienced a failure or deficiency significant enough to take the bridge out of service. The workshop will concentrate on the recent emergency repair of the I-40 Hernando de Soto Bridge over the Mississippi River between Tennessee and Arkansas. A major fracture in one of the tie girders of this steel tied arch bridge, found during a routine inspection, led to the closure of the bridge, after which emergency repairs were carried out under an extremely aggressive schedule. The workshop will describe efforts undertaken by Michael Baker inspection staff to quickly remove traffic from the bridge once the problem was detected, and the efforts subsequently undertaken to design and implement a repair to quickly allow traffic back on the bridge.

The successful repair and reopening of the Hernando de Soto bridge was assisted in part by lessons learned through similar emergency rehabilitation projects that Michael Baker staff participated on, including the I-71/I-75 Brent Spence Bridge fire, the I-64 Sherman Minton Bridge closure, and the I-43 Leo Frigo Bridge, which was closed after the dramatic settlement of several piers. This workshop will discuss these and other emergency repair projects and illustrate how experiences on these projects helped produce positive results under challenging circumstances on the Hernando de Soto emergency repair.

W06: How to Effectively Work With a DOT
Rachel Stiffler, Vector Corrosion Technologies, Canonsburg, PA; Lynnette Stevens, Ohio DOT, Columbus, OH; Matthew R. Weaver, P.E., and Michele Harter, P.E., Pennsylvania DOT, Harrisburg, PA; Chad Robinson, West Virginia DOT, Charleston, WV

The objective is to help the consultant and contractor community work with the DOT more effectively and efficiently. 3 DOTs will be presenting their best practices in working with the DOT. If time allows, we hope to also hear from the featured agency.

W11: Bridge Coating Contracts – Quality Control vs Quality Assurance
Tony Serdenes, Greenman-Pedersen, Inc., Columbia, MD; Sarah Olthof, Greenman-Pedersen, Inc., Grand Rapids, MI

Time: 4:30 PM – 5:30 PM

This workshop will discuss the requirements for both the contractor’s Quality Control (QC) inspection and the owner’s Quality Assurance (QA) inspection. It will detail the responsibilities of each inspector on a bridge painting project. This will include what types of inspections are required to be performed by each inspector based on their role. What type of documentation each inspector is required to generate. How they should work together to achieve a successful project while conducting themselves professionally without crossing lines. This will also include communication between the QC and the QA.