It hasn't been easy finishing Silver Spring's new Paul S. Sarbanes Transit Center, under construction at Colesville Road and Wayne Avenue.

The more than $95 million transit hub is expected to be the busiest Metro station in Maryland when it is completed, but the estimated completion date keeps drifting further away as utility lines and record snowstorms delay construction and residents grow restless.

But since late February, and continuing through the end of the month, transit center planners do get a fun, daily respite from the pressures of building a massive, highly-anticipated public project: big, loud, cool explosions.

Every day between 11 a.m. and 2 p.m. a foghorn signals the underground excavation blast to come. Then 30 seconds later, a loud bang sending enormous ripples through a grey patch of the construction grounds, leaving a cloud of dust and a large plot of piled rocks where smooth ground once was. The blast is contained underground and lasts only a few seconds but the force of several hundred pounds of dynamite is noticeable.

"Whoa, that's pretty cool," exclaims Tim O'Gwin, a capital projects manager with the Montgomery County Department of General Services, from the rooftop of a nearby office building as his colleagues in dress shirts and ties react giddily to the blast.

The daily blasts are a sharp contrast to the weeks of seeming inactivity at the site during underground utility work and snowstorms. Sarcastic time-lapse YouTube videos showing the lack of progress at the construction site that made the blog rounds last year have been replaced with videos of the blasts distributed on online forums.

The blasts move thick slabs of rock and concrete underground to allow for quicker excavation and installation of stormwater management vaults. The impact is contained within the construction site and police monitor the area during every blast.

The construction site itself is muddy with remnants of February's record snowfall still evident despite the recent warm weather. Large embankments at first appear to be the early stages of building foundation but turn out to be nothing more than they are: towering mounds of moved dirt.

Once the blasting is done, likely within a month, a foundation for the three-tiered transit center can be formed, then columns to support the upper levels and by mid-fall, canopies, escalators, and final touches can be completed. By then the current 20- to 25-man construction team from Rockville-based general contractor Foulger-Pratt will have expanded to more than 100, said Don Scheuerman, acting section chief of the project management section of the county's Department of General Services

Despite an original opening date of late 2010, the newest opening date for the transit center is June 20, 2011. As always, that date is tentative, Scheuerman said.

"We've had to deal with a fair amount of contaminated soil and utility work so far," Scheuerman said. "When you work in an urban area that kind of stuff happens."

To account for the delays and a reduction in state aid, about $6.6 million in additional transit center funding for fiscal 2012 was recommended last week by the county council in Capital Improvements Program deliberations.

The first level, with an entrance off Colesville Road, and the second level, with entry from Ramsey Avenue, will hold a total of 34 bus bays serving various local and inter-city services. The top level, accessed by Bonifant Street, will include 54 parking spaces for Kiss and Ride users and taxi cabs.

Other transit options will include the existing Metro station and MARC lines and a future Purple Line stop. The hiker-biker Capital Crescent Trail will link up with the Metropolitan Branch Trail at the transit center.

A future residential building and hotel will be privately developed on the north end of the construction site along Wayne Avenue between Colesville and Ramsey.

More than 100,000 users per day are eventually expected to travel through the new transit center.

"It's going to be the ultimate of cool," Scheuerman said.