Nelson-Flanders Water Treatment Plant

Sharing a picturesque rural site with a 19th century dairy farm, the Nelson-Flanders Water Treatment Plant in Longmont, CO, sits in harmony with history and nature. Designed to complement adjacent structures, the modern treatment plant resembles a historic barn and its dry chemical storage facilities look much like silos. The project, completed by the Black & Veatch / Western Summit Constructors joint venture team, earned a 2006 Design-Build Excellence Award from the Design-Build Institute of America.

The plant provides high quality drinking water to meet the increased demands of a growing population and economy. The City and design-build team worked closely with the community to preserve trees and wildlife corridors, devoting special attention to providing routes for migratory hawks and relocating prairie dog colonies.

Although the project required diverse permits from multiple entities, the plant began operating three months ahead of schedule at a cost that was $2.8 million under the $43 million budget. Many provisions were incorporated into the design to accommodate future upgrades that would allow the facility to meet enhanced regulatory standards and increased water demands.

 Conventional Water Treatment

Longmont follows a process of conventional water treatment, outlined below. More information about our drinking water can be found in the annual Water Quality Report.

1. Coagulation/Flocculation

Aluminum salts and other chemicals called “polymers” are slowly mixed with the raw water which neutralizes the electrical charge of fine, suspended particles, causing larger particles, known as “floc”, to form.

2. Sedimentation

The chemically treated water flows into large settling tanks which effectively reduce the velocity of the water below the point that it will transport suspended materials through the tank. This process allows the “floc” to settle and collect on the tank floor for removal.

3. Filtration

Deep bed filters made of sand and anthracite coal remove the remaining fine particles that carry over from the sedimentation process. As these particles are removed, turbidity diminishes until clear water emerges.

4. Disinfection

Water then passes into a contact tank where chlorine is added to kill any remaining bacteria or disease-causing organisms.

5.  Distribution

The finished water is closely monitored as it enters the distribution system to provide a stable pH, which minimizes scale and corrosion in pipes and plumbing. In addition, chlorine residual levels are routinely sampled throughout the system to ensure the quality of the water at all points of distribution.