Embrey Dam

Embrey Dam, downstream of I-95 bridges across Rapahannock River, prior to its removal
Embrey Dam, downstream of I-95 bridges across Rapahannock River, prior to its removal
Source: US Fish and Wildlife Service, Dam Removal in Virginia: "Dammed If You Donít, Undammed If You Do"
blasting an opening in Embrey Dam allowed water to drain from the reservoir
blasting an opening in Embrey Dam allowed water to drain from the reservoir
Source: US Fish and Wildlife Service, Dam Removal in Virginia: "Dammed If You Donít, Undammed If You Do"

Construction of a canal on the Rappahannock River began in 1829. Construction of nearly 50 locks, 20 dams, and 15 miles of slackwater canal from the Fall Line at Fredericksburg upstream to Waterloo in Fauquier County was completed in 1849, 20 years later.

Within five years of completion, however, the Rappahannock Navigation Company was bankrupt, because operations and maintenance costs exceeded revenue from tolls. In the 1850's, traffic from the Piedmont region at the headwaters of the Rappahannock and Rapidan rivers, which could have floated downstream to Fredericksburg if the canal had been finished earlier, was carried instead by train on the Orange and Alexandria Railroad to the competing port at Alexandria.1

the 1855 dam diverted water into the Rappahannock Canal, which was used for hydropower in Fredericksburg
the 1855 dam diverted water into the Rappahannock Canal, which was used for hydropower in Fredericksburg
Source: Library of Congress, View of Fredericksburg, Va. Nov. 1862

The Fredericksburg Water Power Company purchased the Rappahannock Navigation Company rights on the Rappahannock and Rivanna River. The transportation rights were useless, but the power company wanted to use the transportation canal in Fredericksburg to distribute water to mills. The Fredericksburg Water Power Company built an 18' high dam at Fredericksburg in 1855, plus a canal through the countryside outside the town. Water from the canal, which was elevated above the river level, was released to turn waterwheels that powered machinery inside the mills on the southern bank of the Rappahannock River.

in December, 1862, the few crossings of the Rappahannock Canal forced Union troops to travel through narrow corridors before they could attack Marye's Heights, leading to an extraordinary slaughter by Confederate forces
in December, 1862, the few crossings of the Rappahannock Canal ("Drain Ditch") forced Union troops to travel through narrow corridors before they could attack Marye's Heights, leading to an extraordinary slaughter by Confederate forces
Source: Library of Congress, Map of Fredericksburg, Va., and vicinity

The Fredericksburg Water Power Company became part of the Spotsylvania Water Power Company in 1910, one year after it had built a concrete dam 4' higher than the wooden 1855 dam. The extra height allowed the new 22' tall dam to supply 8,000 horsepower, compared to the 5,000 horsepower provided by the earlier dam. The Virginia Electric and Power Company (VEPCO) acquired the Spotsylvania Water Power Company and built a hydropower plant to generate electricity from the falling water.2

The City of Fredericksburg acquired the Embrey Dam from VEPCO in 1968, after the utility closed the small hydropower plant because it was relatively inefficient (especially compared to the utility's nuclear power plants). The city also acquired the utility's riparian land upstream of the dam, anticipating possible construction of the Salem Church Dam.

Embrey Dam (yellow X) would have been submerged by a re-regulating dam (blue X) for the Salem Church Dam (red X)
Embrey Dam (yellow X) would have been submerged by a re-regulating dam (blue X) for the Salem Church Dam (red X)
Map Source: ESRI, ArcGIS Online

The Salem Church Dam was authorized in 1946, at a maximum height of 220 feet above sea level, in response to the floods of 1942. The Corps of Engineers calculated the Salem Church Dam would have a positive 2.1-1 benefit/cost ratio, assuming benefits for flood control, water supply, lake recreation, and hydropower. Rural electric cooperatives supported the project, expecting to get priority to purchase hydropower from the Federal government at times of peak demand. The dominant investor-owned utility, Virginia Electric Power Company (VEPCO), opposed the project as unfair government-subsidized competition.

A smaller re-regulating dam would have been constructed just below the Embrey Dam, to minimize the speed at which water levels changed downstream of Salem Church Dam itself. Tha re-regulating dam offered the opportunity to make Salem Church Dam into a pumped storage project, increase hydropower potential from 89MW to 200MW. Embrey Dam would have been submerged, and a flat-water reservoir would have stretched 25 miles upstream to Kellys Ford on the Rappahannock and to Raccoon Ford on the Rapidan.3

Congress authorized a 20-foot taller Salem Church Dam in 1968. A reservoir at 240 feet above sea level would have flooded more of the river valleys upstream, but generated more hydropower and stockpiled a larger water supply. Opposition by canoeists and other advocates of free-flowing rivers, together with concerns about cost estimates and environmental impacts, prompted a revision in 1971 to build a dam at he 230-foot level and eliminate the hydropower. The Army Corps of Engineers finally determined in 1974 that the dam was not a feasible project, after recalculation of the interest rate dropped the benefit/cost ratio to 0.09.4

current location of historic canal used for waterpower in Fredericksburg
current location of historic canal used for waterpower in Fredericksburg
Source: US Fish and Wildlife Service, Wetlands Mapper

Until 1999, the city maintained the VEPCO canal that runs through Fredericksburg in order to bring water to the municipal water treatment plant. After the city partnered with Spottsylvania County to build a new water treatment plant upstream on Motts Run, Embrey Dam no longer provided any beneficial use.

Embrey Dam diverted water to power numerous mills in Fredericksburg, and a separate canal further downstream powered a series of mills between Thornton's Mill and Knox Mill
Embrey Dam diverted water to power numerous mills in Fredericksburg, and a separate canal further downstream powered a series of mills between Thornton's Mill and Knox Mill
Source: City of Fredericksburg, Historic Resources along the Rappahannock and Rapidan Rivers

The dam did create environmental harm. For almost a century, until 2004, the tall Embrey Dam blocked passage of anadromous fish such as American shad and striped bass. They could not spawn in the main stems of the Rappahannock and Rapidan and in tributaries to those rivers upstream of Fredericksburg. Fish could swim through the natural rapids at the Fall Line, but once the dam was constructed fish could not jump over a 22' high wall.

the 1910 version of Embrey Dam was 22 feet high, blocking shad from migrating upstream
the 1910 version of Embrey Dam was 22 feet high, blocking shad from migrating upstream
Source: US Fish and Wildlife Service, National Digital Library

Recovery of native species is essential to restoring the health of the Chesapeake Bay. Estimates of suitable habitat blocked by the dam ranged from 100-900 miles, depending upon expectations of the size of small tributaries that would be used for breeding.5

Striped Bass
Striped bass
Source: US Fish and Wildlife Service, Image Library)

Fredericksburg found a creative way to get the dam removed at Federal, rather than local expense. It recruited the US military, under its Innovative Readiness Training program, to treat the dam removal as a training exercise. Thanks to the efforts of Senator John Warner, the US Congress provided $10 million to fund the dam removal. The initial blast to remove a section of the dam failed when only 10% of the charges exploded (it was a training exercise...), but the engineers quickly fixed the problem. A second blast breached the dam, and the remnants were removed by standard equipment after the spring fish migration season was over.6

Eight years later, scientists were delighted to discover that the project benefited more than shadd and striped bass - there was a significant increase in breeding American eels in small streams at the headwaters in Shenandoah National Park.7

habitat opened by removal of Embrey Dam
100 miles of habitat opened by removal of Embrey Dam (marked by purple lines on map)
Source: US Army Corps of Engineers Embrey Open Miles

One challenge from dam removal - what to do with the sediment that had been trapped by the dam? The dam was 22 feet high when first built, but by 1998 perhaps 500,000 cubic feet of sediment had acummulated and water depth behind the dam was only 6-8 feet.8

There has been little industry in the Rappahnnock River watershed upstream of Fredericksburg, so the level of toxic chemicals in the sediments was very low. They did not need to be handled as hazardous waste, but removing the dam and allowing a slug of sediments to wash downstream would have caused a substantial short-term impact on the aquatic vegetation and fish.

The developer of the Celebrate Virginia project offered to use the sediments as fill material, reducing the cost of transport for the Corps of Engineers and increasing the amount of flat land that the real estate developer can create. The City of Fredericksburg finally purchased the disposal site, so the city would own the valuable real estate that would be created.

Estimates of the volume of sediment ranged from 270,000 cubic feet to over 500,000 cubic feet. The Corps of Engineers decided to dredge about half of the estimated volune for disposal on land. The hard-to-access remainder was spread out in a thin sheet on the river bottom, so that half was left behind the dam for natural river flows to disperse downstream towards the Chesapeake Bay. In the end, the Corps was unable to dredge all the planned sediment before the deadline for dam removal, which had to occur before the springtime fish runs.9

As a result of incomplete removal or miscalculate volume, excess sediment plagued the Rappahannock River for years after removal of the Embrey Dam. In 2011, the chair of the local Economic Development Authority called for the Corps to return and complete the job. The presumed requirement was flood control, to remove the barrier of sediments still remaining in the Rappahannock River. The worst case scenario is another rainfall like October 1942, when the Rappahannock River rose past the 18' flood stage and crested at over 42' high.10

Embrey Dam was removed in 2004 at no cost to Fredericksburg, but there is no Innovative Readiness Training program for removing the remaining sediment at no expense to Fredericksburg. One unsolicited proposal in 2012 proposed to dredge the silt and sell 1 million cubic yards as construction material. Though the individual making the proposal did not have experience in such projects and did not have any permits for such activities, the potential exists for re-purposing the silt rather than just wait for it to wash down to the Chesapeake Bay.. hopefully in a gradual fashion, without causing the city to flood.11

old location of Embrey Dam
old location of Embrey Dam (note I-95 in upper left)
Source: US Geological Survey Fredericksburg 7.5 minute topo map (1994)
Rappahannock River, flowing free (now) between I-95 and old location of Embrey Dam
Rappahannock River, flowing free (now)
between I-95 and old location of Embrey Dam

in 2004, the first attempt to blow up Embrey Dam failed
in 2004, the first attempt to blow up Embrey Dam failed
Source: US Fish and Wildlife Service, National Digital Library

Links

the second attempt to blow a hole in Embrey Dam was successful
the second attempt to blow a hole in Embrey Dam was successful
Source: US Fish and Wildlife Service, National Digital Library

References

1. "I-95 of the 1800's," The Free Lance-Star, May 25, 2003, http://news.google.com/newspapers?nid=1298&dat=20030525&id=jfAyAAAAIBAJ&sjid=mwgGAAAAIBAJ&pg=3685,7125013; "The Story of the Rappahannock Canal," Central Rappahannock Regional Library, February 23, 2009, http://history.librarypoint.org/rappahannock_canal (last checked November 8, 2013)
2. "Embrey Dam," Off the Beaten Path, Volume 1, http://www.simplyfredericksburg.com/offpath/embreydam.shtml (last visited November 8, 2013)
3. "Salem Church Dam and How the Idea Grew," The Free Lance-Star, September 20, 1967, http://news.google.com/newspapers?nid=1298&dat=19670920&id=idRNAAAAIBAJ&sjid=ZIoDAAAAIBAJ&pg=7354,4524845 (last checked November 8, 2013)
4. "Engineer's report is death blow to dam" and "Dam's fortunes rose, fell," The Free Lance-Star, October 4, 1974, http://news.google.com/newspapers?nid=1298&dat=19741004&id=O_ZNAAAAIBAJ&sjid=FIsDAAAAIBAJ&pg=5401,482872 (last checked November 8, 2013)
5. "Embrey Dam Removal," Virginia Department of Game and Inland Fisheries, 2005, http://www.dgif.virginia.gov/fishing/embrey_dam.html; "Embrey Dam removal opens 100s of miles of river to fish," Bay Journal, April 1, 2004, http://www.bayjournal.com/article/embrey_dam_removal_opens_100s_of_miles_of_river_to_fish (last visited November 8, 2013)
6. "Boom time at Embrey dam," Water Power and Dam Construction, April 2004, http://www.waterpowermagazine.com/features/featureboom-time-at-embrey-dam; "River Marker," Fredericksburg Free Lance-Star, September 23, 2008, http://fredericksburg.com/News/FLS/2008/092008/09232008/412067/index_html?page=1 (last visited November 8, 2013)
7. Nathaniel P. Hitt, Sheila Eyler, John E. B. Wofford, "Dam Removal Increases American Eel Abundance in Distant Headwater Streams," Transactions of the American Fisheries Society, Volume 141, Issue 5 (2012), http://dx.doi.org/10.1080/00028487.2012.675918 (last visited November 8, 2013)
8. "Technical alternatives analysis to provide fish passage at Embrey Dam," Virginia State Senate Document No. 18, TIMMONS, Inc. for the Virginia Department of Game and Inland Fisheries, 1998, p.17 http://leg2.state.va.us/dls/h&sdocs.nsf/fc86c2b17a1cf388852570f9006f1299/49284552667b687a8525658b006e9b72/$FILE/SD18_1998.pdf (last checked November 12, 2011)
9. Mary Katharin Pritchard, "The Influence Of Fine Sediment Introduced To An Armored Bed Downstream From A Dam," Masters Thesis, Texas State University-San Marcos, May 2007, p. 14, https://digital.library.txstate.edu/handle/10877/3366; "Suctioning up a century of sediment," Fredericksburg free-Lance Star, August 27, 2003 http://www.fredericksburg.com/News/FLS/2003/082003/08272003/1082643/index_html (last checked November 8, 2013)
10. "Sandy river," Fredericksburg Free-Lance Star, August 16, 2011, http://fredericksburg.com/News/FLS/2011/082011/08162011/645613; "River Silt Gets Economic Attention," Fredericksburg Patch, February 15, 2011, http://fredericksburg.patch.com/groups/politics-and-elections/p/river-silt-gets-economic-attention; "Virginia Floods," National Weather Service, http://www.erh.noaa.gov/er/lwx/Historic_Events/va-floods.html (last checked November 8, 2013)
11. "Stafford man revives plan to dredge Rappahannock," Fredericksburg Free-Lance Star, April 20, 2012, http://news.fredericksburg.com/newsdesk/2012/04/20/stafford-man-revives-plan-to-dredge-rappahannock/ (last checked November 8, 2013)
removal of Embrey Dam opened 106 miles of spawning habitat upstream on mainstem Rappahannock/Rapidan rivers
removal of Embrey Dam opened 106 miles of spawning habitat upstream on mainstem Rappahannock/Rapidan rivers
Source: Virginia Department of Game and Inland Fisheries, Embrey Dam Removal

commemorative plaque at site of former Embrey Dam, honoring Senator John Warner for his support of efforts to remove Embrey Dam
commemorative plaque at site of former Embrey Dam, honoring Senator John Warner for his support of efforts to remove Embrey Dam


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