St. Vrain Diversion Structure Replacement
The Highland Ditch Company services more than 40,000 acres of farmland. Its primary diversion infrastructure is located near Lyons, Colorado, along the St. Vrain River in Boulder County.
In September 2013, a five-day rainfall exceeded the annual average in Boulder County. The resulting flood destroyed Highland's diversion dam and headgate structure, which were built in 1870.
A design-build team was contracted to replace the hydraulic structures as quickly as possible so the system would be operational before spring runoff. The accelerated schedule was implemented so that water would be available for the 2014 irrigation season.
Alden's role included:
- Hydrologic analysis
- Hydraulic design
- Structural engineering
- Field inspections and engineering services during construction
The project design accommodated short lead times and readily available materials. Our team also developed rebar and steel shop drawings, which saved several weeks in the schedule.
The project features include:
- 350 cfs diversion structure with 5 headgates
- Sluice structure with 2 sluice gates
- 70’ long diversion dam, including a grout curtain below
- 60’ long trash rack
- More than 100’ of concrete retaining walls and wing walls
- Scour protection
- 800’ long trapezoidal channel
This project started only weeks after the historic flood event in September 2013. Alden worked closely with the contractor to meet the aggressive schedule; construction was completed on February 5, 2014.
What does an accelerated timeline look like?
- September 12 - 15, 2013: Peak of flooding; St. Vrain diversion structures fail
- September 17, 2013: Engineering team, contractor, and owner meet at the site; design begins
- October 5, 2013: Contractor begins reconstruction of the canal
- October 30, 2013: First concrete placement for the new diversion structure
- December 15, 2013: St. Vrain Creek is first diverted to Highland Ditch
- February 5, 2014: Construction completed
Capability
Civil InfrastructureRelated Projects
Between 1932 and 2010 the state of Louisiana has lost about 2006 square miles of land due to a combination of subsidence, sea level rise, and management of the Mississippi River. Computer models predict a further loss of 1800 to 4200 square miles in the next 50 years, amounting to 55% of the land in Plaquemines Parish and resulting in $300 million in annual economic damage. Following hurricanes Katrina and Rita, the Coastal Protection and Restoration Authority (CPRA) was formed as a single state entity with the authority to protect and restore the lands of coastal Louisiana.
The $50 billion coastal master plan includes restoration and risk reduction projects. The restoration projects include barrier island restoration, hydrologic restoration, marsh creation, ridge restoration, sediment diversion, and shoreline protection. The Barataria and Breton Basins have experienced some of the largest land loss—almost 700 square miles. Two sediment diversions are being designed, one for each basin. The sediment diversions connect the Mississippi River to the basins, allowing for the controlled diversion of up to 75,000 cfs of water and sediment to the Barataria basin and 30,000 cfs to the Breton basin.
The design and construction of sediment diversions on the scale proposed for Barataria and Breton is unprecedented, the results of which will rely heavily on the numeric and physical modeling required to design the major diversion features, including the inlet, conveyance, and outlet structures. Alden is constructing two 1:65-scale, live-bed physical models to test performance and effectiveness of the diversions.
Discover more:
- Making Mississippi Mud In Massachusetts To Restore Wetlands | Here & Now [wbur.org]
- A Mini Mississippi In Mass. May Help Save New Orleans From Rising Seas [90.9 Boston NPR]
- Rerouting the Mississippi River could build new land—and save a retreating coast [Science Magazine]
- Find the Mississippi River in Massachusetts [Chronicle 5 WCVB]
- To Save Louisiana’s Vanishing Coast, Build a Mini Mississippi Near Boston [The New York Times nytimes.com]
- Louisiana researchers tackle a changing Mississippi Delta [PBS News Hour Weekend pbs.org]
- Mid-Barataria Sediment Diversion could create, save 47 square miles of land over 50 years [nola.com]
- CPRA Using Giant Model to Test Mid-Barataria Diversion
- Mississippi River Diversions Could Save Louisiana's Drowning Coast [enr.com]
- Louisiana Coastal Protection and Restoration Authority [Official Website]
- A Mini-Diversion in Boston is Paving the Way for Louisiana’s Boldest Coastal Project [mississippiriverdelta.org]

Civil Infrastructure
Mid-Barataria Sediment Diversion
Alden constructed two 1:65-scale, live-bed physical models to test performance and effectiveness of the proposed land rebuilding diversions on the Mississippi River.
The Cedar Cliff dam and hydropower project is located approximately six miles from Cullowhee, in Jackson Country, North Carolina. The dam and hydroelectric facility is owned by Duke Energy and is located downstream of three other hydroelectric projects that are operated as a system.
The primary spillway includes a Tainter gate and the existing auxiliary spillway system includes two fuse plug sections (with different crest/activation elevations). It was determined that the combination of the primary and auxiliary spillway systems were not adequate to safely pass the regulatory-increased Inflow Design Flood (IDF). The construction of a Hydroplus Fusegate system with six semi-labyrinth Fusegates in an enlarged auxiliary spillway channel was selected to increase spillway capacity to safely pass the new IDF which is now the full Probable Maximum Flood (PMF).
Two reduced scale physical models were constructed to determine the required size of a ventilation system for the proposed Cedar Cliff Fusegates and headpond and tailwater levels at each Fusegate for flows up to the sixth Fusegate activating. The tailwater levels were required for design of the Fusegate ballast system.
}', 9='{type=string, value=https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Cedar-Cliff/Cedar-Cliff-Model-Testing.mp4?t=1641419157050}', 13='{type=image, value=Image{width=4608,height=3456,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Cedar-Cliff/Cedar-Cliff-Model-Test-Chute-Looking-Upstream.jpg',altText=''}}', 14='{type=string, value=Model testing looking upstream}', 15='{type=image, value=Image{width=4608,height=3456,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Cedar-Cliff/Cedar-Cliff-Model-Test-Looking-Downstream.jpg',altText=''}}', 16='{type=string, value=Model tesing looking downstream}', 17='{type=image, value=Image{width=4608,height=3456,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Cedar-Cliff/Cedar-Cliff-Model-Final-Construction-tailwater.jpg',altText=''}}', 18='{type=string, value=Cedar Cliff modeling during final construction}', 19='{type=image, value=Image{width=4608,height=3456,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Cedar-Cliff/Cedar-Cliff-Model-Final-Construction.jpg',altText=''}}', 20='{type=string, value=Cedar Cliff model at final construction}', 21='{type=image, value=Image{width=4608,height=3456,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Cedar-Cliff/Cedar-Cliff-Model-Construction-Piping.jpg',altText=''}}', 22='{type=string, value=View of the piping structures used to supply water to the Cedar Cliff model}', 25='{type=number, value=0}', 27='{type=number, value=1}', 28='{type=number, value=1633353243000}', 29='{type=number, value=20}'}
Civil Infrastructure
Cedar Cliff Spillway
Physical model study to determine hydraulic performance of a proposed auxiliary spillway system during flooding events