North Tunnel, an 18' (5.5m) Storm Sewer in Ellicott City, MD

West Portal: (Satellite, many of these trees have been removed to make way for the construction.)

East Portal: (Satellite, the parking lot will be closed during construction.)

I know of Ellicott City because of the B&O Depot.

Ellicott City Safe and Sound posted

During the past year, drill and blast operations have progressed the mining shaft, drop shaft, and caverns below grade to facilitate assembly of ‘Rocky,’ our Tunnel Boring Machine. Blasting operations are expected to continue through the months of January and February, generally between the hours of 8 AM and 8 PM, Monday through Saturday. Residents in the vicinity of Ellicott City’s West End may detect the blasts, which typically last just a few seconds.  No impact to vehicular traffic is anticipated.

The North Tunnel is a water conveyance project that, once complete, will carry flood waters from the West End of Ellicott City through an 18-foot-diameter tunnel to the Patapsco River. This project will reduce the risk of flash flooding by intercepting water from the western portions of town and diverting it underground and away from Main Street.

David Novak: Our tax dollars at work due to the overdevelopment above Ellicott City. Meanwhile the developers are laughing all the way to the bank. Thank you Ball, the county Council, and the planning board.

HowardCountyMD, cropped
Rocky will be boring through solid granite.

This is just one of several projects needed to deal with stormwater. It makes me glad that my local building codes require developers to include retention ponds or underground storage to handle storm surge.

Presentation, p2

Presentation, p12

"This crucial project was made possible through $27 million in state grants and $28.5 million in state loans." [TunnelingOnline]

I estimate the tunnel will be about a mile long. Since the TBM will dig itself out of a side of a cliff along the Patapsco River, will they be able to sell the TBM?

That raises the question, once the TBM head is out in the air, how do they push the rest of the 300' (91m) TBM out of the tunnel?

And that $50m state funding is just a third of the cost. At least it is a loan instead of a grant.

2:03 video @ 0:14
$75M federal loan to fund Ellicott City North Tunnel Project
[I skipped the rest of the video.]

It is interesting how they use heavy mats chained down to concrete anchors to contain the blast.

Ellicott City Safe and Sound posted 1:44 video

The transformational Ellicott City North Tunnel project is moving forward! Crews have completed site preparation and are now in the critical phase of rock blasting to create the mining shaft. This marks a giant leap in our efforts to significantly reduce flooding risks in Historic Ellicott City.

The North Tunnel will reroute floodwaters safely away from Main Street, protecting residents, businesses, and the community we love. Through this transformational project, we are continuing to build a safer Ellicott City.