Letters

As the mechanical/electrical engineer for the MasterCard Operations Center, O'Fallon, Mo. ("Charging ahead," BD&C, March 2002, page 32), I'd like to clarify a few points surrounding the M/E design. The reliability and capabilities of the installed M/E systems are far greater than your article stated.

The electrical systems are actually a 2(N+1) system and can be considered fault-tolerant. There are separate utility services and completely redundant controls and monitoring systems. Moreover, the mechanical system is not N+1, but is a hybrid of two topologies that exceed N+1.

Several significant designs were implemented, and the major story here is the plant's ability to conserve energy and free-cool, while maintaining the critical computing environments. In fact, MasterCard's utility bills dropped by more than $35,000 a month once the systems were installed.

While the topologies differ, they all offer maintenance and system operation that is concurrent and transparent to the IT loads installed in the data center, with some form of failure recovery at every level.

Also, in the sidebar on the Internet (page 36) are several notions that don't hold water for mission-critical facilities today:

• A 200 watts per square foot power density is restricted to enterprise-level data centers operating an open platform system;
• Web hosting facilities and Internet data centers are not the highest powered facilities in the marketplace. In fact, hosting facilities typically have a demand power density below 50 watts per square foot and a service demand of less than 30 watts.

William P. Mazzetti Jr., Mazzetti and Associates, San Francisco

I find the example used in the sidebar to "Charging ahead" (BD&C, March 2002, page 36) simplistic and somewhat flawed. I am a strong advocate of "business risk assessment" in the determination of high availability design and assume that the "balance sheet" approach described addresses that as well. But to conclude that "dual-cording" does not improve reliability because the external power source has no redundancy ignores other factors internally that provide the second source, such as: on-site generation and redundancy in the infrastructure; double-ended substations; dual/redundant uninterruptible power supply, etc.

Howard Levison, Harrison, N.Y.

I was surprised to see that the people of Wisconsin were without stone cladding on their capitol ("Capitol Idea," BD&C, March 2002, page 38). According to your photo caption on page 40, the white granite cladding of the Wisconsin State Capitol has apparently been returned to Vermont.

I suspect the stone had to be returned because it was taken from the bethel (i.e. hallowed or holy place) in Vermont. I am sure that the people of Bethel, Vt., left no stone unturned in the search for their missing granite. I was always told never to take stone for granite, but I now know that one should neither take anyone else's granite for stone cladding.

Michael J. Byle, Gannett Fleming Inc., Audubon, Pa.

Editor's note: The clever reader caught us in some sloppy word play. The granite was restored to its former condition, not "state."

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"Letters to the Editor"

c/o Rob McManamy

Building Design & Construction

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Oak Brook IL 60523

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The word "million" was inadvertently omitted from last month's lead news story, "Ground Zero draws brief tribute, long-term study" (BD&C, April 2002, page 7). The total of debris removed from that site at press time was "1.28 million tons."

Also in the same issue, Michael O'Callahan, San Francisco, should have been credited for the photo atop page 33.