[Journal of the House of Delegates of the Commonwealth of Virginia… (Richmond, 1820), Appendix, Documents, p. vi:]
THE SOUTHANNA RIVER.
…Mumford's bridge [future site of the Poindexter Road/Louisa Route 613 bridge over the South Anna River in the Green Springs National Historic Landmark District]…. is believed to be as high as a stream navigation [on the South Anna River] ought to be attempted at present, but it might be continued higher by means of dams and locks. From Mumford's bridge to Hanover town, by estimation from place to place, is 95 miles [by the South Anna and Pamunkey rivers, and just over 50 miles in a direct line; Hanovertown situated 3 ½ direct-line miles west of the future U.S. Route 360 bridge over the Pamunkey River in Hanover County]. In this distance [along the rivers between Mumford’s Bridge and Hanovertown] there are 15 mills, factories, &c. which will require 16 locks, averaging about 8 1/2 feet each. Supposing these to be of the same description as those…in the estimate for the Northanna, the expense will be for lockage $16,000, for improvements between the locks $2,800, making the whole cost of procuring a batteaux navigation on the Southanna to Mumford's bridge, $18,800 [about $412,000 in 2019 dollars]. This stream appears to discharge about the same quantity of water as the Northanna, and, from information, does not fail more from drought. It is therefore to be presumed, that the navigation may be useful about the same proportion of the year. I am of opinion that sluice dams with gates, might be constructed on a plan that would answer an excellent purpose on small streams, where the fall is moderate, as in the Northanna, Southanna, Willis' river and many others. I am told that on Willis' river, sluice dams furnished with a single gate are in use.
[proposal for sluice-dam gates for the recommended navigation systems on the Mumford’s Bridge-Hanovertown segment of the South Anna and Pamunkey and certain other Virginia rivers:] These [existing, single] gates [on Willis River] are attached to the sill by hinges, and open downwards; of course, when the dam is full, and the gate is let fall, the weight of the water passing over it, with a strong current, will render it very difficult to raise it again, until the water is nearly out of the dam, and even then must he hard to raise against the stream. When a boat passes through, it must either be detained until the water is nearly run down, or leave the gate open and suffer the water to waste, so that a succeeding boat cannot pass, until a person or two are sent forward to raise all the gates, and this so long before hand as to give time for the dams to fill; and what is still worse, returning boats with their hands, must be delayed from the same cause. I would propose [for the recommended navigation systems on the South Anna and other rivers], that instead of one gate only, to open downwards, there should be another attached in the same way, to the upper edge of the sill, to open upwards. This, when shut, will be pressed against the posts, and will not be so liable to leak as w hen shut from below, and pressed by the water from the posts. Suppose the upper gates all shut, and the dams full; when a boat arrives, the lower gate is raised, and fastened up, then by a small opening in the upper gate, let in the water between them; when the space is lull, the pressure will be taken off the upper gate, and it may be easily pushed down to the bottom; the fastenings of the lower gate being loosened, it will fall outwards and the boat may pass; the upper gate may then be raised a little from the bottom and it will close itself, and the boat may go on. This contrivance would certainly give a perfect command of the water, so that it might always be economised to the very best advantage. The dams may be from 2 to 2 1/2 feet high, according to circumstances, and where the ripples arc short, something may be saved by placing them near the head, and making a sluice to the foot of the ripple. This sluice will always be filled by the first water discharged from the dam, and of course will cause no delay. In this way, it may sometimes happen, that a foot may be gained exclusive of the height of the dam. When the natural stream is sufficient, both gates will always be down.
Principal Engineer [,Virginia Board of Public Works]
[Abstract selection and notation by Noel G. Harrison, NPS]