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
An existing roof vent arrangement was allowing rainwater to enter the Pot Room. Alden supported efforts to develop a roof vent geometry to eliminate the intrusion of rain water. The purpose of the CFD study was to ensure that the roof vent modification did not increase pot room temperature levels beyond specified limits for workers in the plant.
To evaluate the existing and proposed Pot Room arrangements, thermal and fluid flow profiles in the immediate vicinity of the pots were determined based on air flows through the plant floor and wall mounted vents. The detailed CFD model was developed from plant drawings to include all major basement, pot room and roof venting geometries. The surrounding ambient environment was included with quiescent atmospheric conditions and average ambient temperature. Thermal losses form the pots to the pot room air and from the pot room to the environment were included in the analysis. The results of the CFD modeling showed that the proposed modification to the roof venting arrangement was acceptable and would not increase the temperature in the worker-occupied spaces by more than 2 degrees F.
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Civil Infrastructure
Smelter Pot Room Roof Ventilation System
Read how a CFD study ensured that a roof vent modification did not increase pot room temperature levels beyond safe levels
Plant McDonough, owned and operated by Southern Company, has experienced excessive siltation at the makeup water intake. The intake uses cylindrical wedgewire screening within an intake originally designed for much larger, once-through cooling water flows. Flow modeling was performed to provide a viable passive solution to reducing the sediment accumulation at the intake. To model the geometric details of the system accurately, a field survey was performed prior to the flow modeling efforts. The flow study included both CFD modeling and scale physical modeling.
For this investigation, Alden developed a 1:20 scale live bed physical model. This model was extremely well tuned to reproduce the behavior of bed load sediment. Even with the very fine crushed walnut shell particles, however, it was challenging to reproduce the behavior of suspended load. The use of a high fidelity CFD model, therefore, proved extremely useful for this project, in that suspended load is generally very accurately tracked with CFD models, which are not well validated for bed load simulation. By using the two together, the two extremes of sediment transport are captured, and developing a solution that covers this range has a high likelihood of success.
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Civil Infrastructure | Hydrology Hydraulics and Fluids
Plant McDonough Intake Modification
CFD and physical model study to assist in the evaluation of a solution to reduce the sediment accumulation.