A recent blasting and coating project for the San Clemente Pier in San Clemente, CA, was no simple walk on the dock of the bay. It offered significant challenges that dictated the design of a contained environment underneath the pier dock and a precisely controlled environment. Thanks in part to sophisticated climate control system from Polygon (formerly the Moisture Control Services Division of Munters), the operation proceeded as planned and the pier re-opened on schedule.
The 1,296-foot San Clemente Pier offers locals and tourists sweeping Pacific Ocean panoramas, fishing, dining and views of surfing competitions and beach activities.
City officials determined the pier, last renovated in 2005, needed a major makeover including timber decking replacement, new guard rails and stringers, steel pile cap maintenance, repairs to protective coating on steel piling, beams and pile caps, installation of an active corrosion protection system, new light fixtures and poles, and electrical upgrades.
Corrosion of the steel pylons and metal support columns underneath the pier was the result of years of exposure to saltwater and humidity. Houston-based The Brock Group, a contractor specializing in such maintenance activities and work, was hired to oversee the blasting and coating portion of the project.
Brock decided to divide the work into four pier sections of approximately 50,000 cubic feet each. After sandblasting the metal, a three-coat painting system consisting of a zinc coating, epoxy primer and polyurethane finish would provide corrosion control and prevention.
The project began in January 2010 and required completion by that Memorial Day weekend so the refurbished pier could be unveiled at the start of the busy summer season.
Project Offers Challenges
The blasting and coating needed to take place underneath the pier, which created a unique challenge for the project because it required development of a complex scaffolding containment area to allow workers access to that area.“This was the first time I oversaw a pier project in which we conducted the work underneath the metal support pylons that support the structure,” said Tim Johnson, Project Superintendent with Brock Services, Ltd., a division of The Brock Group.
Johnson hired a specialty contractor to design and build scaffolding to hang underneath and be supported by the pier so that workers could conduct the restoration operation.
With the project taking place over open water, another challenge was ensuring a contained working space to prevent materials from polluting the ocean.
“During blasting projects, debris grit is displaced and applied coatings can become airborne,” said Johnson. “We had to be very careful that we did not contaminate the ocean below us, so such debris was carefully managed.”
Another major concern was moisture levels from the ocean and how this moisture would delay and negatively impact the curing of coating materials. “Condensation and temperature extremes lead to flash rusting, inter-coat adhesion problems and curing issues, and create expensive delays, rework and warranty repair costs that can affect the overall service life of the project,” said Johnson.
Dehumidification Speeds Completion
Based on these conditions and concerns, completing the blast and coat operation in a timely manner required a temporary climate-control system to create an environment conducive to curing the coating materials. The contractor specified that the relative humidity in each containment area remain at or below 30 percent.Johnson, who in the past utilized the Moisture Control Services (MCS) division of Munters (now an independent company called Polygon) in other temporary humidity control applications, called Kerry Saulet, Account Manager, to design a system to control moisture and temperature during the blasting and coating process.
“Desiccant dehumidification technology is used in the coatings industry as a method to help control flash rusting, enabling the applicator to provide a superior finish even in the harshest environments,” said Saulet. “This particular project required a unit to maintain conditions as each section of the pier was sandblasted so all three coatings could be applied in a period of days.”
Saulet selected Polygon’s DHi35 PowerPurge unit to provide humidity control for the project. “The energy-efficient PowerPurge reduces both reactivation and postcooling energy,” said Saulet. “The system acts as an energy-recovery system, collecting waste heat off of the hottest section of the desiccant wheel and using it to help with the regeneration. This reduces the energy required for reactivation while lowering the discharge temperature of the process air, decreasing energy costs for post cooling.”
The dehumidification unit was placed on top of the pier over the blasting and coating area and powered by a temporary portable electric power generator. Flexible duct was tunneled into the containment to vent conditioned air into the space. The space was contained with a heavy plastic shrink-wrap to maintain indoor conditions.
As work began, Johnson utilized an inspection company to document each project phase and record humidity levels in the air, temperature within the containment area and the type of equipment used.
“We took manual readings of the relative humidity on a daily basis to make sure conditions were maintained,” said Johnson.
Major Winter Storm Wreaks Havoc
The project faced one last major hurdle when a major winter storm hit San Clemente and destroyed part of the scaffolding on the pier.“We had to shut the job down on an emergency basis for over a month due to the storm,” said Johnson. “We evacuated all the equipment including the dehumidifiers and cranes.”
Due to lost scaffolding and other materials, Johnson was forced to hire divers to retrieve materials that fell into the water. The setback initially pushed back the timeline, but workers’ shifts were extended to make up time.
Work continued a month after the storm, and the project was completed just before Memorial Day as scheduled.
“Without the Polygon unit to control the climate in the containment area, and the guidance of the Munters team, we never would have met our deadline,” Johnson said.
