The McCormack Building in Boston, Massachusetts contains several State of Massachusetts administrative offices. The building has a four-level below grade parking garage constructed with a cast-in-place waffle slab. In 1992-93 an impressed current cathodic protection (ICCP) overlay system was installed. Over the years the rectifiers became inoperable due to poor maintenance and substantial corrosion damage developed in the slab. In 2016 Simpson Gumpertz and Heger conducted an evaluation of the garage and identified significant areas of corrosion distress, so a repair strategy was developed that included rehabilitation of the existing ICCP overlay system.
In 2020 Contracting Specialists, Inc. was awarded the garage repair contract. Vector Construction, Inc. was awarded the ICCP rehabilitation repair subcontract, and VCS Engineering was selected to provide ICCP rehabilitation design and quality control services. As a part of the QA/QC process VCS participated in the activation and commissioning of the ICCP system and installed a remote monitoring unit (RMU).
VCS designed an ICCP system for the top three elevated waffle slabs, while the fourth level being on grade was excluded from the system. The ICCP system is comprised of mixed metal oxide (MMO) mesh within an overlay of latex-modified concrete. Each level is broken into multiple zones that are used to control and monitor the ICCP system. Each level has its own rectifier and monitoring unit (RMU). The RMU monitors and logs the reference electrode data along with each individual circuit’s voltage and current. VCS can access the RMU remotely to collect the data and also interrupt the circuit to collect necessary measurements and verify if the criteria for cathodic protection are being met. This data is also housed on VCS Structureview website, which allows the client to understand the system condition on an easy-to-use interface.
The project was a successful implementation of an ICCP system in the parking garage to protect the structure from any further corrosion. VCS worked with the other contractors to carry out the rehabilitation work in stages so that the garage could be operational throughout the duration of the work. VCS used rugged and reliable technology for the rectifier and RMU, which is far easier to maintain, and is also involved in a long-term contract to monitor the ICCP system.