2005 Winning Projects                                                                              

 Denver Water Recycling Plant
Commerce City, Colorado

  GRAND PRIZE — DESIGN

ENTRANT: CH2M Hill and Boyle Engineering
ENGINEER IN CHARGE: Lawrence J. Schimmoler, P.E./Thomas J. Roode, P.E.

Project Description
After 35 years of research and pilot studies, Denver Water commissioned Boyle Engineering and CH2M HILL to design its full-scale non-potable recycling plant and associated distribution facilities in 1997. The project’s first phase of a 30-million-gallon-per-day treatment plant, distribution, storage, pumping, and piping to initial customers was completed in February 2004. The treatment plant will be expanded to 45 mgd and the distribution system will be extended in subsequent phases to ultimately deliver approximately 17,700 acre-feet of recycled water.

Integrated Approach
Protecting the Environment: The system captures effluent water from the Metro Wastewater Plant before it is discharged to the South Platte River, which significantly reduces the river’s nutrient load and preserves its ecosystems. Wetlands impacted during construction were restored, and wildlife has returned.

Preventing Cross Contamination: No cross connections exist between the drinking water and the recycled water systems. Recycled water flows through a separate purple pipe system. Recycled water pipelines run at least one foot deeper than potable pipelines, so if a break occurs water will not enter the drinking water system. Additionally, warning notices and warning tape are installed a foot above recycled water piping. All operators of the recycled system received training in cross  contamination avoidance.

Reducing Environmental Impact: At full capacity of 45 million gallons a day, the recycled plant will save about the same amount of water held by a small mountain dam and reservoir. Building a dam and reservoir would be more costly and adversely impact the environment.

Reducing Facility Footprint: Using biological aerated filter (BAF) technology minimizes the footprint of the ammonia removal facility. Also, building the distribution pump station on top of the post-tensioned storage tank reduced the land area needed in the limited space site.

Quality
Vision to Reality: The Denver Water Recycling Plant realizes a vision first conceived more than 35 years ago. The project was completed on time, within budget, and, most importantly, with the extreme satisfaction of the plant operations staff.

Ahead of Regulations: When the project began Colorado had no recycled water regulations, so California Title 22 was adopted as a basis. Colorado ultimately established less-stringent regulations, thus enabling design and construction to continue without significant changes.

Owner Involvement: Design delivery involved the Owner’s construction manager, plant superintendent, and operations staff in every project phase. Consistent and relevant communications including 3D design helped staff visualize key features.

Model for Other Reuse Projects: Aspects of this project such as design, project delivery, public input, and education could serve as a model for other entities developing reuse projects.

Originality and Innovation
Cutting-Edge Technology: The Denver Water Recycling Plant is the only plant of its kind in the world using BAFs for recycled water, capturing interest from technologists as far away as Paris. Industrial water quality requirements (zero ammonia and low phosphorus) demanded complex solutions—BAFs in conjunction with breakpoint chlorination and ferric phosphate coagulation and settling. BAF technology uses polystyrene granules coated with bacteria to oxidize ammonia.

Innovative Pilot Testing: Although pilot testing expenditures totaled approximately $50,000, testing refined a treatment approach saving Denver Water millions by justifying inclusion of flocculation and sedimentation processes to significantly increase industry-standard filtration rates. Additionally, the plant can treat 2.5 to 45 mgd (at ultimate buildout), a significant range that reduces onsite storage requirements.

3D Design Reviews: The Consultants employed 3D design, allowing the Owner and stakeholders to view images and videos of the facilities prior to construction. 3D design resulted in accelerated reviews and approvals and minimized conflicts between various engineering disciplines, which can often lead to significant change orders during construction.

Pump Station Configuration: Building the distribution pump station on top of the post-tensioned storage tank is a unique application of existing technologies.

Complexity
Project Delivery: The Owner led project delivery using a General Contractor/Construction Management implementation approach. This non-traditional, design-build method has subsequently been used as a model by other municipalities throughout Colorado, including the Cities of Westminster and Thornton. The project ultimately included 15 separate construction packages to accelerate the schedule, many related to large equipment purchases, enabling design to be tailored to actual materials and equipment.

Maintaining Existing Operations During Construction: Two large 10 foot by 10 foot active effluent conduits were modified to connect to the new facility. Protecting adjacent facilities required extensive shoring.

Complex Sequence: A treatment sequence appropriate for a variety of water uses challenged the Consultants. The technologically complex and entirely new solution involves BAF, rapid mix, flocculation, sedimentation, deep-bed media filtration, breakpoint chlorination, and disinfection.

Tight Site: Especially remarkable was the fast-track design of a new process and associated ancillary components in a location completely surrounded by active industry and construction. The project site is tightly framed by railroad tracks and a road (both remained active), above- and below-ground structures, and a pond and wetlands.

Contribution to Social and Economic Advancement
Community Relations: Every audience integral to public acceptance was kept well-informed on issues and topics relevant to their relationship to the project. Communications spanned letters, web sites, brochures, news media, posters, tours, meetings, and other channels, as appropriate.

Conserving Water Benefits: Recycling water defers, and in some cases eliminates, the need to develop new raw water supplies, thus avoiding the environmental impacts associated with building reservoirs, distribution pipes, pump stations, and other infrastructures. At build-out, the plant will reduce the demand on the potable water system by conserving enough raw water to supply 35,000 households with drinking water.

Savings for Owner: Overexcavating and replacing an existing clay layer with structural fill eliminated caissons under the treatment complex, thereby saving $320,000 in foundation costs. Though the Owner usually places pumping systems below grade and adjacent to storage facilities, the Consultants saved both site space and nearly $4 million in construction costs by locating vertical turbine pumps on top of the distribution storage tank.

Meeting Customer Needs: The ammonia removal process was designed after construction began to meet the specific needs of Xcel Energy for Cherokee Power Plant cooling water.