Talk:Quabbin Aqueduct

Copyvio?
The Physical Characteristics section seems to be a too-close-for-comfort paraphrase of part of this document. Then again, this is a government document. Are state government documents also public domains? There are some great facts in there, so someone should rewrite this. — m a k o ๛  04:55, 11 March 2009 (UTC)

Comparative length
The Quabbin is impressive, but it's not near the top of the list for tunnel length. Even among water tunnels, it's behind the Delaware Aqueduct, Catskill Aqueduct, and West Delaware Tunnel in the New York City system. The comment about it being 1/2 a mile shorter than the Hetch Hetchy is lifted straight from the pdf linked in the above note, and the Hetch Hetchy isn't mentioned in the list of longest tunnels article. --Grano (talk) 20:36, 28 September 2009 (UTC)--Grano (talk) 20:35, 28 September 2009 (UTC)Grano 21:30 28 September 2009 (UTC)

Correction on nature of water flow
The high point of the Quabbin Aqueduct tunnel is not under the Ware River as described in this page, but at the Quabbin Reservoir. It does not flow by siphon as stated, but by gravity from Quabbin Reservoir to Wachusett Reservoir. See Massachusetts Water Resource Authority document Figure 1-2 at http://www.lowimpacthydro.org/assets/files/lihi-cert-app-files/OakdaleDescriptiona.pdf.

The interesting engineering feat is actually that the water can be made to flow "uphill" (up the tunnel) from the Ware River intake back to the Quabbin Reservoir. This flow is accomplished by closing the tunnel on the downhill - Wachusett Reservoir - side and opening the intake from the Ware River. The Ware River at this intake is higher than the Quabbin Reservoir (see Figure 1-2 again), and the pressure - also known as hydraulic head - of the column of water filling the shaft (Shaft 8), forces the water in the aqueduct tunnel itself uphill (up-gradient) to the Quabbin Reservoir.

This technique is used to augment the supply of water in the Quabbin Reservoir to the Wachusett Reservoir, and to improve the quality of the river water by detaining it in the Quabbin Reservoir. It is for this last reason that Ware River water from this shaft is only sent to the Quabbin Reservoir, and not "downhill" via the Quabbin Aqueduct directly to Wachusett Reservoir.

At the Quabbin Reservoir the river water is not released at the aqueduct's main intake, Gate 12, but instead at Gate 11. Here, two islands (the summits of Mount Zion and Walker Hill, flooded by construction of the reservoir) have been connected by a "baffle dam" to each other and by another baffle dam to the shore between Gate 12 and Gate 11. So before the discharged river water can reach Gate 12, the main intake for the aqueduct, it must travel around both of these islands.

During this journey, which was estimated by the designers to take up to four years (or is it four miles and takes two years?), impurities in the river water settle out, and the water is exposed to oxygen from the air and to sunlight, This exposure further purifies the river water through oxidation and ultraviolet light sterilization. And I imagine algae, plankton, fish and other organisms also consume the material brought in the water from the river. — Preceding unsigned comment added by Boston Mapmaker (talk • contribs) 19:15, 8 January 2014 (UTC)