Specialty Applications of Detec Systems

FORWARD THINKING
FROM TOP TO BOTTOM

The new $500 million Bill & Melinda Gates Foundation headquarters is targeting LEED Gold status through various sustainable construction practices, with Detec assisting in several critical areas.

Just below the Gates Foundation campus sits a massive 900,000 gallon concrete cistern that will harvest rainwater from hardscape roofs and the campus plaza, itself a roof over occupied basement areas. The collected water is for non-potable uses such as irrigation, filling water gardens and supplying toilets; allowing the campus to reduce its city water use by as much as 70 percent.

The Foundation’s stewardship goals meant that the new headquarters must be built to withstand the test of time. By employing careful construction practices and utilizing robust building systems, they expect the campus to be their home for at least one hundred years.

To that end, Detec was commissioned by the Foundation to perform IntegriScan™ quality assurance tests to verify that above grade, the waterproof membranes for the campus plaza and several other living and hardscape surfaces were watertight, and below grade, the entire cistern including all vertical surfaces, would be watertight.

"Experience has shown us that no matter how well a membrane is installed, there are always unforeseen issues during construction that can compromise its integrity," said Detec Vice President Duncan Townsend. "For instance, our first pass through the cistern revealed several areas where the liquid-applied membrane was spread on a bit thin, leaving small pinholes that could not be seen by visual inspection. On a structure like this, any breach--no matter how small--is unacceptable."

Membrane material was then added to those areas immediately after identification. (IntegriScan testing is not hindered by the same time and accuracy limitations inherent in other testing methods.) Detec then retested to confirm absolute water-tightness, the contractor remained on schedule and the cistern was ready to begin it’s first century of service.

THE CHALLENGE
The City of Seattle embarks on an ambitious plan to cover six open-air water reservoirs with concrete lids and build new parks above them. But two of those reservoirs, the 50-million gallon Beacon Hill Reservoir, and the five-million gallon Myrtle Reservoir were each experiencing leaks in their waterproof membrane.

Water was spotted dripping from the underside of the new lid at the Beacon Hill site. Engineers suspected they might also have an issue with the Myrtle reservoir, but that project was already complete and had been covered with gravel, topsoil and grass. Electric conductance testing would be the only way to check for leaks.

Bob James from the Washington State Health Department said, "It’s vital to stop and do it right, now, because these facilities are expected to be in service for a least a century."

THE SOLUTION
Detec Systems was contracted to perform their patented IntegriScans™ during the installation of the replacement membranes for the Myrtle and Beacon Hill Reservoirs to verify that they were in fact watertight before being covered. This method of testing is far more precise and cost effective than the legacy flood test method. "This is our water supply. We don't want to mess around," said utility spokesman Cornell Amaya.

We also installed our LeakLocate™ System atop the new membranes: a combined 300,000 linear feet of electronic breach sensing tape laid out in a grid that continuously monitors for conductance through the membrane. It quickly and accurately locates any leaks, facilitates repairs and minimizes repair costs through early detection. "The Detec systems work as promised," said Project Manager Mark O’Leary.

The Contractor has since chosen to be proactive with the remaining two reservoirs by verifying membrane integrity during construction using IntegriScans, and installing Leak Locate Systems on the top side of the membranes.