Siena Reservoir Pump Station and Pipeline

Beginning on Wednesday, January 15, 2025 the trail along Community Ditch/Broomfield Trail will be temporarily detoured from the hard surface to crushed rock for several hundred feet to allow for vault construction as part of the pipeline construction. Chain link fencing will be installed along the concrete trail diverting users to the crushed rock path.

The Construction Team has remobilized to area along the Siena pipeline route the week of December 30, 2024, bringing in necessary materials and equipment including a large crane. Active construction began the week of January 6, 2025.

In late 2023 through the summer of 2024, the City and County of Broomfield, Moltz Construction, and the pipeline subcontractor Ironwoman initiated work along the pipeline corridor as part of the Siena Reservoir Pump Station and Pipeline Project.

As the final phase of pipeline construction necessitates a shutdown of Broomfield's raw water supply line and the Water Treatment Facility, the work has been scheduled to occur during periods of low water demand, ensuring coordination with other ongoing activities within Broomfield.

Construction is now at a point where staff can start to fill Siena when raw water is available. Currently, community water demands are using Broomfield's maximum water delivery capacity. Once water demands slow, staff will redirect part of the water to fill Siena Reservoir. Staff is expecting to start filling in late September 2024.

In August, the Siena trail along the dam face will be impacted by construction. The community will experience intermittent trail closures for 5 to 10 minutes as the construction team moves material and equipment to the existing gate for the Siena outlet (along the dam) and for crews to install a conduit to the gate. Construction crew team members will assist with pedestrian access during these short closures for the community’s safety.

The Siena Reservoir Pump Station and Pipeline Project includes a new pump station and pipeline to convey water from Siena Reservoir to Broomfield's water treatment plant to assist in meeting water demands during peak summer months.

The Siena Pump Station and Pipeline Project will transfer raw water from Siena Reservoir to Glasser Reservoir (raw water storage) or directly to Broomfield’s Water Treatment Facility (WTF) on 144th Avenue. Broomfield’s water demands continue to increase with growth and Broomfield needs additional raw water storage to feed into the treatment facility. A pumping station at Siena and a pipeline will deliver water to the WTF. The facilities would assist in meeting peak summer demands for potable water.

The pump station building work continues. The building has been dried in to allow for exterior work to begin.

The Late Work Package (LWP) for the remaining construction was presented to Council at the April 25, 2023 meeting and approved. The contractor moved on-site in late May 2023 and began site grading work. The wet well foundation (caissons and footers) and floor slab for the building have been completed and the structural building walls are in process. The extensions and rebuilding of the stormwater and Northern water discharge rundowns into Siena Reservoir were completed in early summer of 2024.

The conduit for the control gate on Siena has been installed and the new gate tested. The gate is located on the northern dam side of Siena. The refilling has started and will continue depending on raw water availability. Construction is expected to take 18-24 months from May 2023 (finishing between January 2025 and May 2025).

Work for the pipeline began in December 2023 and has been waiting delivery of remaining equipment. The final installation and tie-in requires a shut down of the Water Treatment Facility for several weeks. The shutdown has been scheduled to occur for January and requires coordination with Northern Water and Denver Water. Final restoration along the pipeline will occur in the spring.

The fenced construction area and trailer at the northwest corner of Sheridan and Lowell are associated with the Siena Project and not related to oil and gas operations.

Additional information regarding oil and gas in Broomfield can be found on the oil and gas dashboard.

The Water Resources Division of Public Works is responsible for maintaining and monitoring Siena Reservoir. Siena has never been drained since it was constructed. After consulting with a dam and reservoir specialist, it was determined Siena would need to be drained in a slow manner over a longer time period. The draining process began in early March 2022 and was completed to a level (approximately 12 inches remaining) to allow for construction. Staff met with the Colorado Parks and Wildlife (CPW). CPW agreed to attempt to salvage fish in late April 2023 when the water level had receded to a manageable level and when water temperatures were warmer. Unfortunately due to the steep and wet slopes, CPW could not safely attempt a fish salvage.

If you have any questions about the project please contact Broomfield’s CIP Project Manager Ronda Jo Ackerman Alford at ralford@broomfield.org.

Background

The anticipated capacity of the Siena Reservoir facility would be 10 to 15 cubic feet per second (CFS) and 14,200 feet of pipeline expected to be 20 to 30 inches in diameter.

Broomfield has two major water supply sources: treated water purchased from Denver Water, and raw water from both the Colorado-Big Thompson (C-BT) and Windy Gap Projects. One of the City Council’s ongoing priorities is water resource acquisition and development. This includes efforts to continue moving the Windy Gap Firming Project (WGFP) forward, acquiring water rights, and constructing new capital facilities.

To provide a sufficient water supply to the Water Treatment Plant (WTP) during summer when water demands are highest, additional raw water storage is needed in Broomfield. Siena Reservoir is an asset of the Water Fund and is filled by a connection to the Carter Lake pipeline. Stored water cannot be drained except through the spillway and a new pump station and pipeline is required to deliver the water from Siena Reservoir to Glasser Reservoir or directly to the WTP. The improvements will provide seasonal summer storage for the next 10 to 15 years until the Broomfield Reservoir is needed. A map showing the location of Siena Reservoir and proposed pipeline alignment is shown below.

Timeline

Fall 2020

Broomfield’s Water Treatment Facility (WTF), located at 4395 West 144th Avenue, treats the raw water supplies from the C-BT and Windy Gap Projects. A CIP project to expand the WTF by 6 MGD to its current 26 MGD was completed in fall 2020.

Nov. 10, 2020

The City and County of Broomfield (Broomfield) at the November 10, 2020 Council Meeting retained Muller Engineering Company to complete a Preliminary Design Report for the design of a pump station and associated pipeline from Siena Reservoir (Siena) to the Broomfield Water Treatment Facility (WTF). Siena is located northeast of the intersection of Lowell Boulevard and Sheridan Parkway and south of the Northwest Parkway in Broomfield with a normal storage capacity of 450 acre-feet. The WTF is located at 4395 West 144th Avenue, Broomfield, Colorado.

May 11, 2021

Broomfield City Council approved a design consulting agreement with Muller Engineering for design and construction documents on May 11, 2021.

Early 2022

Moltz Construction was selected in early 2022 as the Construction Manager/General Contractor (CM/GC). The CM/GC assisted with reviewing constructability, analyzing potential cost savings and scheduling of the project. The early work on-site began March 2022.

Dec. 13, 2022

Council approved an early work package (EWP) with Moltz at the December 13, 2022 council meeting. The work includes procurement of long lead items (pumps and controllers), tree mitigation and trail improvements to allow for trail detours.

February 2023

Since the size of the pump station building exceeds ten percent from the original Site Development Plan (SDP), the project required an SDP amendment. The Amendment was completed and approved by Broomfield's Planning Department in February 2023.