| Gwynn’s Run Culvert | Gywnn’s Falls Run Tunnel | Buried / Covered Gwynn’s Falls Run |Tucked away and forgotten in a wooded area of a park, lies a unique and quite rare tunnel outfall / culvert. With a build date of 1829,
this structure is listed in the Maryland Historical Trust Archives. This tunnel system was yet again discovered through research of historic maps. Gwynn’s run was a significant branch that emptied into the Gwynn Falls River. After the discovery of the M.J.MM Storm Sewer Outfall the writer began focusing more research on the West Side of Baltimore. The Gwynn’s Run branch is clearly seen in early historical maps. When researching old sewer and storm sewer maps, a large number of existing drains and planned construction drains were seen to dump into this open air branch. The branch does not appear on modern day maps and stop appearing in the early 1900’s. Where did all this volume go? There was only one way to find out and that was to go out and explore the area. To uncover what Google Satellite view and Bing Birds Eye view did not reveal.
So it turns out that this Sewer’s Tunnel Outfall was first a stone culvert. Basically a stone tunnel structure built to accommodate a railroad to pass over a stream body of water. That railroad being the B&O railroad. What makes things even more interesting is that this stone culvert was the first of its kind in the United States. This structure is old and in great shape. The writer presumes that this system was built in 2 phases. First the stone culvert and later the remainder of the stream was buried and covered over. Accessing this tunnel system has its hurdles and considerations. Your in a dangerous part of town. Or I should say an area of town that has elevated risks for violence and/or theft. So there is always the concern that you will come back from an explore and find your vehicle’s windows bashed out and on blocks. Then you have to figure out how to get there by not crossing private property. Once your enveloped inside an urban woods, hopefully you have good topographical sense and a little bit of luck or youll be wasting time chasing animal trails that lead to thorn bushes and poison ivy patches. Inside this woods suddenly the grade starts dropping and by this time you can hear a large volume of water done below. Ducking through natural holes found in poison ivy patches, unsure if all this trouble will pay a large reward the large creek is seen and heard below. By the time you reach a broken concrete embankment the smell of sewer fresh is strong and you realize that your trouble was well worth this reward.
A massive 6 meter high granite arch that has held up since 1829 towers over you with a very distinct keystone at the center top. The retaining wall soars even higher then this. The area around this outfall is like a waste land. Trash and debris like mangled metal, pieces of furniture, tires, railroad waste strewn everywhere covering the rocks. Debris stuck in the branches of the surrounding trees, this place must rip during storm surges. There is a convenient little 12 inch ledge that follows the base of the tunnel and takes a right angle into it. When you peer around the corner, air is just blasting out of there. Pushing further in about 10 meters, you quickly realize that this ledge drops off out of site into deep murky, cloudy water. Only God knows what lies at the bottom and its most likely quite deep after a 175+ years of storms ripping and eroding a trench through there. Further explorations will require a man raft or something to float you in there. The main outfall seems to continue about 50-70 meters or so and takes a sharp easterly bend. Its interesting that large boulders seems to be built or left in place at this bend. Which makes sense as its a sharp artificial turn in the river and those boulders must receive a brunt of the water pressure and friction as the creek obeys the tunnels command. In my writings, I seldom mention that I’ve really come to learn that water can produce strange acoustics in underground confined spaces. Sometimes its almost like the chattering of a crowd of people at times. I will highlight that the sound coming from inside this tunnel that bent out of sight was quite eerie to say the least. Its hard to describe, its almost like you could hear a group of men working back in there.
It is difficult to estimate the discharge volume during typical storm surges of this storm sewer’s outfall. When comparing the data of 3 USGS monitoring sites The rough calculation was done by taking the measured stream discharge volume, at the Villa Nova stream gauge which sits upstream and then adding the measured discharge volume of Dead Run, a tributary that dumps into the Gwynn Falls River proper. Subtracting the sum of the 2 measured discharge poitns, by the total measured discharge of the Gwynns Falls River discharge gauge at Washington BLVD with the difference being associated with buried portion of the Gwynn Falls Run system. The rough numbers seem to suggest that the Gwynn Falls Run Storm Sewer accounts for 20% of the over all final discharge of the Gwynn Falls River during periods of storm. The rough data seems to show that the drain would output 250-300 cubic foot a second during a typical 0.4″ of rainfall summer storm. More treacherous guesstimates were performed, trying to conclude the theoretical capacity of a arched culvert that is 5.7 meters wide and 6.1 meters high at the top of the arch. Not knowing the formulas for calculating the capacity of an arch, the length of this section and variables such as slope it wouldn’t be surprising if 1000+ cubic foot a second could discharge via the outfall.
USGS 01589330 DEAD RUN AT FRANKLINTOWN, MD
USGS 01589300 GWYNNS FALLS AT VILLA NOVA, MD
USGS 01589352 GWYNNS FALLS AT WASHINGTON BLVD AT BALTIMORE, MD