Dewatering At St. Regis Bal Harbour

By Steve Hudson | September 28, 2010

Those who talk about downturns in the construction economy have not seen the level of activity in the Miami area. New high-rise projects can be seen all across the area, and one of them is St. Regis Bal Harbour-Resort and Residences.

The new project, being constructed on what was formerly the site of the Sheraton Bal Harbour Beach Resort, includes construction of three 27-story buildings on a 9-acre site – a hotel tower plus two condo towers. The project is a development of Starwood Hotels Worldwide, Inc., and is being managed by The Related Group. The architect is Sieger Suarez Architectural Partnership. Coastal Construction Company is construction manager on the project, with Eric Cohen serves as Coastal’s senior project manager and John Mills as general superintendent.

The project is located just yards from the Atlantic Ocean, so it’s no surprise that water is a major issue. The concrete footings for the three buildings as well as for some 13 different podium areas (and six tower cranes) must all be constructed below the water table – and that adds significantly to the complexity of the project.

"The water table is only one to three feet below the surface," notes Cohen, "but the lowest concrete construction is 18 feet below the water level."

Before any of the concrete work could begin, something had to be done about the water.

Devising a Dewatering Scheme

To handle the dewatering challenge, the Coastal and Related team worked with Roger Freeman of Water Control Systems to develop a multifaceted plan to dewater the site and allow that foundation work to move ahead. Water Control Systems has handled many dewatering projects in Miami/Dade County and southern Broward County over the years, and Freeman has more than three decades of experience in the dewatering business. But he says he knew right away that this project would be a special challenge.

Bryan Brisebois, West Palm Beach branch manager for Thompson Pump, worked with Freeman to develop the final dewatering plan. It called for the use of a large fleet of pumps, including a variety of rotary, hydraulic, jet and vacuum-assisted models, to handle the overall efforts.

"At one point," notes Chris Thompson, vice president of branch operations for Thompson Pump, "we had more than 50 pumps working on the site at one time."

To locate the necessary pumps, Thompson Pump went as far away as Delaware, Maryland and Kansas City. The job of locating suitable pumps was further complicated by the requirement that pump operation had to meet strict sound level guidelines; that meant that the team had to acquire a large number of Thompson’s Silent Knight sound-attenuated pumps as well.

Without a doubt, Thompson says, it was definitely a "dewatering challenge."

"Normally," adds Freeman, "we only have to focus on two or maybe three dewatering locations at a time. But on this one the norm is 10 to 12." He continues, "It’s one of the toughest dewatering jobs I’ve ever seen."

A Multifaceted Dewatering Challenge

The first pumps were activated on March 14, 2008. The water table in the area of those pumps immediately began to drop, and excavation started three days later.

The deepest dewatering was in the area of the hotel. There, it was necessary to dry things out to a point 18 feet below the water table.

"We had as many as 16 or 17 pumps operating just in that one part of the project," Brisebois says.

Another challenge stemmed from the fact that the configuration of the pumps was constantly changing – typically on a daily basis. As the construction team focused first on one area and then another, the team relocated pumps as necessary to make sure that key areas were dewatered and ready to go as the schedule demanded.

The team also faced work hour restrictions. To avoid disturbing residents of neighboring buildings, work hours are restricted to 8:30 a.m. until 5:30 p.m. But the pumps had to operate around the clock, so regular checks were required to make sure that the ongoing dewatering operation did in fact meet specified decibel limits.

The team also had to be aware of environmental considerations. These ranged from the challenges of pumping saltwater, which is very corrosive and requires special maintenance attention, to the need to use biodegradable hydraulic fluids in all pumps.

For Thompson Pump’s Brisebois and his West Palm Beach branch crew, this project has been a 24-hour-a-day, seven-day-a-week undertaking.

"We have had Thompson representatives on the site 24 hours a day for months," notes Chris Thompson, adding that the four field service mechanics assigned to the project have been able to complete all maintenance without disrupting the dewatering operation.

Handling Hose and Water

With the large number of pumps on the project, it’s no surprise that there is a lot of pipe and hose on site too. The wellpoint installations, for example, have required more than 5,000 feet of header pipe. Elsewhere, some 12,000 feet of sock drain is used to dewater some shallower areas.

But those numbers pale in comparison to the length of discharge hose that’s been used on the site – a length, notes Brisebois, that’s measured not so much in feet as in miles.

"We have 31,700 feet of discharge hose out here," he says. In round numbers, that’s just over six miles.

In operation, the pump network has handled as much as 35,000 gallons of water every minute around the clock. What becomes of the huge volumes of water that must be handled in the course of such an ambitious dewatering project?

"South Florida Water Management requires that all water be pumped through a multistage filter system before being discharged," Brisebois says. On this site, the team utilized eight Baker tanks to meet the sedimentation and filtering requirements.

A portion of the filtered water was gravity fed into the nearby stormwater system. But most was discharged into some 14 wells through 12-inch high-pressure jet pumps.

Despite the scope of this dewatering operation, the dewatering system has operated smoothly. But as Freeman notes, that’s not an accident. He points out that planning, scheduling and attention to logistics and maintenance are of tremendous importance on any dewatering project, but especially on one of this magnitude.

"One thing you have to remember in dewatering," Freeman says, "is that the water never takes a break."