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1877 Map
Balancing Reservoir location
Balancing Reservoir Plan
Balancing Reservoir Stand Pipe
Tunnel end near Lake Montebello in Waste Water Lagoon
Waste Water Lagoon Stand Pipe
In the early days drinking water was not treated, The main concern was making sure there was enough supply to meet the demand. Originally Baltimore City water was distributed by privately owned companies. However, by 1808 Baltimore City began to purchase the Baltimore Water Company and its wooden pipes.

By 1812 Baltimore City completed construction of a dam across Jones Falls and created Lake Roland. However, concern for adequacy caused the city to build a 36 inch diameter cast iron pipe from Gunpowder Falls to a tributary of Jones Falls to supplement the water from Jones Falls. City drinking water from this source continued to fail, and was discontinued by 1915 after the creation of the Montebello Filtration Plant #1.

By 1864 Baltimore City completed construction of the Lower Loch Raven Dam (LLRD) with Ravens Rock (RR) at the western end, a suspension bridge for pedestrian use above the dam, and a public picnic area in cleared land on the eastern end. The picnic area and suspension bridge have disappeared, but the dam remains. This LLRD dam has a spillway crest of 170 feet above MSL (Mean Sea Level), and created the Lower Loch Raven Reservoir (LLRR). At this time work also began to build a 7 mile long, 12 foot diameter, brick lined tunnel to supply Lake Montebello as a more permanent water supply for Baltimore City.

By 1881 Lake Montebello and the tunnel connecting it to the Lower Loch Raven Reservoir was in service. Initially Lake Montebello was used as a reservoir for distribution of water to Baltimore city. At this time there were no settlement basins. or filtration beds. to remove physical pollutants, but by 1910 chemicals such as chlorine began to be added to the water being distributed to the city to disinfect it.

By 1915 Montebello Filtration Plant #1 (MFP#1) was completed, and construction was completed for a new Upper Loch Raven Dam (ULRD) across Gunpowder falls with a spillway crest elevation of 188 feet above MSL. This new dam created the initial Upper Loch Raven Reservoir (ULRR) which continued to supply water to Montebello via a 10 foot diameter steel pipe that connected it to the 1881 tunnel at Raven's Rock. The Momntebello Filtration Plant #1 includes an underground reservoir as the source of treated water for public distribution, thus Lake Montebello was no longer used as a reservoir for distribution of drinking water.

By 1923 the Upper Loch Raven Dam was modified to raise its spillway crest elevation to 240 feet above MSL. At this time it was considered a requirement to limit the water pressure on the brick lining of the 1881 tunnel and enable a static flow condition (Gates closed and no pumping) using a standpipe and each end that balanced, and limited, the water level at each end of the tunnel to between 195 to 200 feet above MSL. The standpipe at the Montebello end was located in the Montebello Waste water Lagoon, and the standpipe at the Raven's Rock end was located in a limestone quarry what was converted to a small reservoir named the "Balancing Reservoir".

By 1928 construction that began in 1918 was completed for the Montebello Filtration Plant #2.

By 1932 Prettyboy Dam was completed which provided additional storage capacity for water that could be released to the Gunpowder Falls to feed Loch Raven Reservoir. This year a conduit was built between Druid Lake and Lake Montebello.

By 1941 construction that began n 1936 was completed on on a new 12 foot diameter concrete lined tunnel from the head end near Gunpowder Falls (actually near the intersection of Loch Raven Drive and Cromwell Bridge Road) to the Montebello Filtration Plant #1. The head end of this 1940 tunnel was connected to the Upper Loch Raven Reservoir(ULRR) by two pipes. The first was a new 10 foot diameter Pre-stressed Cylindrical Pipe (PCCP), and the second by extension of the old 10 foot diameter steel pipe at Ravens Rock. This new tunnel enabled discontinuing use of the 1881 tunnel.

By 1950 a conduit was built from The Patapsco River to Montebello.

By 1956 construction was completed for Lake Ashburton, the Ashburton Filtration Plant (AFP) near Mondamin and Liberty Dam was completed across the Patapsco River with a spillway crest of 420 feet above MSL to create Liberty Reservoir. Water from Liberty Reservoir flows by gravity through a 12.7 mile long, 10 foot diameter tunnel to the Ashburton Filtration Plant for treatment. There is also a pipe that connects Liberty Reservoir to the Montebello Filtration Plant #1.

By 1966 a 38 mile long,10 foot diameter pipe was constructed from the Susquehanna River near a pumping station at Deer Creek to the Montebello Filtration Plant #1.

By 1971 construction of a the Cromwell Bridge Pumping Station (CBPS) connected to the 1881 tunnel where it passes under Cromwell Bridge Road enabled reuse of the 1881 tunnel to bring pumped water from the Motebello Filtration Plant #1 to be re-pumped to Towson Reservoir. Many citizens of Baltimore County are surprised to learn that within the Baltimore County URDL (Urban Rural Demarcation Line) are eligible for public water from Baltimore City.

By 2005 construction was completed that started in 2003 to modify the Upper Loch Raven Dam to withstand a predicted 100 year rainfall event without increasing the spillway elevation. The Army Corps of Engineers defined a 100 year rainfall event as 3.2 inches of rainfall for 72 hours. To withstand that predicted 100 year event, the sidewall height was increased by 20 feet, and a manually operated gate extended the western sidewall across Loch Raven Drive when the gate was closed.
A glossary of acronyms and more detailed information follows:

LLRD = Lower Loch Raven Dam build by 1864 across Gunpowder Falls with a spillway crest elevation of 170 feet above MSL.

LLRR = Lower Loch Raven Reservoir created by the lower Loch Raven Dam across Gunpowder Falls.

MSL = Mean Sea Level

RR = Ravens Rock. The location of the western end of the Lower Loch Raven Dam at Loch Raven Drive.