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The 240 foot above MSL elevation of Loch Raven Reservoir eliminated the town of Warren, but worked well as a water source. but, the need to deliver more treated water to Baltimore County required a new tunnel to the Lake Montebello Reservoir.
1940 Map showing the routes for the 1881 and 1940 tunnels
Timeline - Selecting this link provides a 7 page summary of general history from 1712, when the community of individuals known as Baltimore occupied a site on the banks of the Bush River, than the Gunpowder River, then the Patapsco River where it remains today.
The image above is a picture of the renovated upper Loch Raven Dam competed in 1922 with a spillway elevation of 240 feet above MSL where it remains today despite a later renovation that added 20 feet to the height of the wing walls to accommodate the Army Corps of Engineer requirements to withstand a 100 year floodplain prediction.
The image above is a picture of Water Treatment Plants #1 & #2 plus the Waste Water Lagoon which is still the termination point for the 1881 and 1940 tunnels from Loch Raven Reservoir. Plant #2 was completed n 1926. This Google image was created in 2011.