Planned one-day closure - NCAR Mesa Lab - 10/10/15  more info>

Outside maintenance


About a year and a half ago, we at the Mesa Lab were subjected to the
lengthy (and probably expensive) process of replacing the concrete in our
courtyard. Some of the new concrete is already disintegrating. This seems
to be of a piece with concrete work done in the past at the Mesa Lab
(buried heating cables that don't work, edges that don't quite meet in a
straight line, steps that collect and hold melt water, and so on). Overall,
my impression is that concrete work done for NCAR over the years has been
slipshod and arguably incompetent. My Delphi Questions, then, are as follows:

1. Do you agree with the above assessment?

2. How much was spent on the concrete work in the courtyard?

3. How much of that, if any, are we getting back, given that the new
concrete is, in part, disintegrating?

4. Has the contractor who did the work in the courtyard been told of the
problems with that work? What is the contractor's legal responsibility?

5. Are the disintegrating areas going to be fixed? If so, when and by whom?

6. What changes are contemplated to avoid problems of this sort in the
future (for example, if and when the concrete work on the tree plaza is

7. Is this problem in any way due to our attempting to make the new
concrete match the old by incorporating crushed sandstone from local
sources? If so, is any thought being given to achieving this match in a
different way? Or has that been attempted already?

Answered on May 21, 1997


1. I agree that often the concrete work at NCAR appears to be "slipshod."
We have deteriorating concrete all over the Mesa Lab. It turns out that
concrete work is not a science, and I'm not even sure it is an art. It is
quite unpredictable and there are few recourses to remedy work that is less
than desirable.

We worked very hard with a consultant to develop a concrete specification
for the fountain plaza to guarantee that the strength would be there and
the color would be correct. The warranty that is available for any concrete
work is very limited because the contractors know that its integrity varies
depending on temperature, humidity, how long it is rotated, how long it
sits in the truck before it is poured, and so on. The only guarantee is
with what is called a slump test. This test was performed to the
satisfaction of our project manager and was in agreement with the
specification. This test only verifies the strength of the concrete and not
the other features.

The fountain concrete work was complicated by the fact that it was laid
over a membrane which we needed for waterproofing. In fact, we think that
is why cracking has occurred. The spalling (concrete surface breakup) that
has occurred should have been caught in the slump test, but probably was
not evident in the batch that was tested.

Contracts tells us that the original contract does not have an option for
remedial action, so we have recently contacted a concrete expert to give us
an opinion about the best course of action to prevent further deterioration
and to help us with future projects. (The problems did not surface until
after the one-year limited warranty was up.)

2. The fountain plaza project was in excess of $125,000, but that included
the engineering, demolition, redesign, and rebuilding of the drain, etc.,
as well as the finished concrete work. I do not have a breakout of the cost
of the concrete alone.

3. and 4. Answered above. According to Contracts, there is no guarantee on
this concrete work beyond the one-year limited warranty.

5. We have found a possible fix with a new patching compound that we will
be using on the tree plaza. We do not want to use it on the fountain plaza
until our consultant finishes his evaluation and recommends a solution. We
hope to have something done this summer based on the recommendation. The
tree plaza work will probably begin in July.

6. We will rewrite the specification to include any recommendations from
the new consultant and we will have Contracts verify a reliable concrete
supplier. We will not be able to get any better warranty than we did last time.

7. We do not believe that the concrete was compromised by our color
specification. However, we hope the consultant will be able to tell us
more. We were unable to get a color match by specifying a quarry and so the
specification contained an added color formula which I hoped could be used
as a standard in the future. That will be revisited depending on the
consultant's recommendation.

I would encourage you to call either Julie Emo, engineering manager, or
John Pereira, maintenance manager, if you have other questions. We are
happy to share information like this, but most people tell us that
facilities work is boring so we tend to keep this information to ourselves.
However, we like to talk about it with anyone who is interested, so please
feel free to call any of us.

•Pat Harris, Manager, Facilities and Support Services