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COMPTROLLER GENERAL'S
REPORT TO THE CONGRESS

SOLVING CORROSION PROBLEMS
OF BRIDGE SURFACES COULD
SAVE BILLIONS

DI GEST

Although bridge roadway surfaces (decks)
were expected to provide relatively
maintenance-free service for about 40 years,
the Federal Highway Administration has found
that some unprotected bridge decks require
major repair within 5 to 10 years, and often
must be replaced after 15 years of service.
The major cause of this early deterioration
is corrosion of the reinforcing steel bars
in the bridge deck, brought about by chloride
chemicals which are used to melt snow. (See
ch. 1.)

About $6.3 billion is needed to restore
the Nation's Federal-aid system bridge
decks. GAO's survey of the 50 States and
the District of Columbia identified 32
States with 162,622 Federal-aid system
bridges having a moderate to very major
bridge deck problem.

Most States have indicated that, if present
conditions are not improved, their currently
repairable bridge decks will continue to
deteriorate, and eventually require complete
replacement at a much higher cost. For ex-
ample, a Federal Highway Administration re-
port points out that, if 29,000 interstate
bridge decks continue to be neglected, an
additional $4.4 billion will be needed later
to repair these bridge decks. (See ch. 2.)

SLIGHTLY CONTAMINATED BRIDGE DECKS

A number of bridges in the Federal-aid system
do not have a protective system on their
decks. They contain either no areas or only
small areas where chloride levels are high
enough to cause bridge deck deterioration.
If these bridge decks were protected with
one of the systems now used for new bridge
construction, significant savings could be
realized by avoiding more expensive repairs

Tear Sheet. Upon removal, the report cove: date should be noted hereon.

PSAD-79-10

later. The potential benefit/cost ratio of repairing and protecting an existing bridge deck needing only minor repair versus completely replacing the deck at a later date is 2.75 to 1.

Lack of funds is the primary reason that States have not installed protective systems on existing bridges.

State officials GAO contacted indicated that funds available for bridge repair are generally budgeted for bridges so deteriorated that replacement of the deck is the only option. As a result, those bridge decks with little or no deterioration will continue to deteriorate, and eventually require repairs or replacements that are much more costly than the cost of the protective systems. (See ch. 3.)

GAO recommends that the Secretary of Transportation identify those bridge decks which can be economically restored, estimate the cost of restoring them, and develop a plan for repairing these decks as soon as possible.

HEAVILY CONTAMINATED BRIDGE DECKS

Many of the existing unprotected bridge decks in 32 States contain chloride levels above the corrosion threshold which will cause the bridge deck to deteriorate, and eventually to require replacement, unless a means is found to halt the deterioration. Numerous techniques are being investigated which may protect these bridge decks from further deterioration. However, the Federal Highway Administration has not yet developed proven, cost-effective techniques for stopping the deterioration.

Cost-effective solutions are needed quickly to avoid using billions of dollars for complete replacement of the bridge decks. (See ch. 4.)

GAO recommends that the Secretary of Trans-
portation reassess the progress being made
in finding proven, cost-effective methods
for protecting existing chloride-contaminated
bridge decks, and take appropriate action
to resolve any problems that are delaying
progress.

LONG-TERM EVALUATION PROCEDURES NEEDED

Weaknesses also exist in the Federal Highway Administration's evaluation process to assess the performance of the technologies in extending the service life of the bridge decks.

. For example, the Federal Highway Administration lacks a formal system to monitor and evaluate the long-term performance of protective systems which were approved for nationwide use on the basis of laboratory and short-term field performance data. (See ch. 5.)

To improve the technology evaluation process, GAO recommends that the Secretary of Transportation establish a formal long-term data collection and evaluation system for bridge deck protective systems.

AGENCY COMMENTS

The Department of Transportation agreed that
GAO had accurately assessed the bridge deck
problem and concurred with GAO's recommenda-
tions. In several cases, it has begun to
make the changes necessary to carry out GAO's
recommendations. For example, the Federal
Highway Administration:

--Will modify its data retrieval program to

better identify bridge deck conditions which
will enable more realistic cost estimates
of bridge repairs. This program is sched-
uled to begin in fiscal year 1980. Federal
Highway Administration officials also said
that the Surface Transportation Act of 1978
now authorizes adequate Federal funds for
bridge replacement and rehabilitation on an
80-20 ratio, but that the States remained
faced with the problem of providing match-
ing funds.

[blocks in formation]

--Plans to propose a new federally coordi

nated research and development project in fiscal year 1980 to search for a less expensive rehabilitation procedure which does not involve the removal of large quantities of concrete.

--Will institute in fiscal year 1979 a pro

gram to provide a long-term data collection system for protective systems. (See app. II.)

The Federal Highway Administration provided other more detailed comments that GAO included in the body of the report where appropriate.

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