From the Cripple Creek Railroads list:

A fire being investigated as arson heavily damaged historic railroad
Tunnel 3 on Gold Camp Road on Monday morning, restricting hiking and
biking in the popular foothills area.

Frank Landis of the Forest Service said it was too early to say how the
fire started or how much damage it caused. But he said a Forest Service
investigator is treating the fire as a crime, and more federal
investigators may be called in to help.

Until the investigation is complete and the agency can make sure the
tunnel is stable, there will be 24-hour security to prevent anyone from
approaching the tunnel on both sides of Gold Camp Road or from using a
popular walkway over the top of the tunnel.

That means hikers and bikers approaching the area from Colorado Springs
via High Drive cannot access the longclosed section of Gold Camp Road
beyond the tunnel. Hikers can still access the nearby Seven Bridges trail.

Landis said the fire apparently damaged or destroyed many if not all of
the centuryold, creosote-treated timbers that support two-thirds of the
tunnel. The other third of the 180-foot-long tunnel is solid granite.

The fire was reported at 9 a.m., and city firefighters worked for about
an hour and a half to extinguish the blaze.

Lt. James Eddy of the Colorado Springs Fire Department said firefighters
sprayed water into both sides of the tunnel but did not go in because
they heard timber and rock falling.

The tunnel partially collapsed in 1988, requiring 8½ miles of Gold Camp
Road to be closed to motorized traffic.

Since then, the tunnel has been blocked on the High Drive side by a berm
and chain-link fence and on the other side by a massive steel plate. The
plate is located on the solid-rock side of the tunnel, about 20 yards
inside the mouth.

Landis said foresters have discovered fire pits in that portion of the
tunnel in the past, and neighbors have worried that people have either
been sleeping or partying in the small section of the tunnel that was
accessible.

The fire comes at a critical time: At the end of March, the Forest
Service is expected to decide whether to reopen the tunnel and Gold Camp
Road to one-way motorized traffic. It's an idea embraced by some and
decried by others, including hikers and bicyclists who flock to the
closed road.

Landis said it is too early to say what effect the fire will have on
that decision.

The agency has said even if the road is not reopened, it has an
obligation to fund repairs to the tunnel to restore it to its historical
condition. The cost of those repairs was estimated at $710,000 before
Monday's fire.

http://groups.yahoo.com/group/CrippleCreekRailroads

Gold Camp Road is the old roadbed of the standard gauge Colorado Springs & Cripple Creek District line, which was abandoned about 1920. It was graded as an auto road after that, and in more recent years has been closed to cars, as a cycling/hiking trail.