Unique Design-Build Engineering Partnership Helps Launch Southern Delivery System Construction

Major construction of the Southern Delivery System (SDS) has now commenced. The project?s initiation marks the culmination of more than a decade of planning, studies, public discussion and regulatory review that found SDS to be the most cost-effective, environmentally responsible and dependable solution to deliver a long-term water supply to the growing populations in the Colorado Springs region.

SDS is a collaborative regional pipeline project that will transport water from the Arkansas River to four SDS partner communities ? Colorado Springs, Fountain, Security and Pueblo West ? through a 62-mile underground pipeline with the ultimate capacity to deliver up to 96 million gallons per day (mgd).

Construction of SDS is divided in two phases. The first phase began in August 2011 and will conclude in 2016. Phase I comprises four main components needed to transport water through a connection to Pueblo Dam to serve the SDS pipeline. These components include 62 miles of raw and finished water pipeline, three raw water pump stations, a 50-mgd water treatment plant and finished water pump station, and a comprehensive project instrumentation and control system.

A ?Value Engineering? Approach

Carollo Engineers formed a unique engineer/contractor partnership with McCarthy Building Companies to design and construct the 50-mgd SDS water treatment plant and finished water pump station ? the largest and most complex component of the SDS project. The team combined several of its key ?value engineering? concepts to project costs savings to Colorado Springs Utilities. Carollo/McCarthy identified more than $25 million in potential construction costs savings and anticipate $3 million in operational life-cycle cost savings that preserve the treatment process and improve maintainability and operability.

A joint proposal to Colorado Springs Utilities outlined a strategy for the water treatment plant design that is estimated to be 25 percent more cost efficient based on an in-depth cost analysis.?

How is this cost-savings realized? In a design-build value engineering approach, the client benefits most from the design firm and the contractor partnering together from the beginning and throughout all phases of the project. This includes the conceptual design, detailed design, construction and operations (see chart).

During the proposal phase, the McCarthy/Carollo team evaluated the initial design plans and identified more than 25 value engineering concepts that could improve upon the constructability and operability of the facility while preserving the overall treatment process design criteria and design intent. This value engineering approach will be much easier to operate and maintain without sacrificing performance
Carollo/McCarthy proposed a new orientation to eliminate more than four miles of large diameter piping (12 inches or greater), 5,000 cubic yards of concrete, and 1,670,000 cubic yards of excavation, resulting in significant savings. In addition, the proposed orientation and site configuration improves maintainability and accessibility by keeping all facilities within a smaller footprint but with more usable in-building space.
The inlet piping was relocated below the hydraulic grade line, making operation much simpler. In addition, the lower elevation decreases the pumping energy to the site, resulting in an operational energy reduction.

Also, Carollo/McCarthy suggested a modified ozone feed system in its proposed design to allow for the large turndown required for the plant. The 30 percent design used fine bubble ozone diffusers, but with flows as low as 5 mgd, supplemental oxygen would be needed for mixing, significantly increasing operational costs. The approach uses a side-stream injection system that accommodates the required turndown. In addition, this approach eliminates the in-contactor maintenance issues associated with a confined space entry, as the contactors would not have any equipment to maintain inside them. The benefits of this approach are operability and maintainability.

Filters, backwash system and solids handling modifications also will result in a construction cost savings and improve the reliability and operability of the filtration system while maintaining all the design criteria selected by Colorado Springs Utilities.

The revisions to the master plan provided the opportunity to re-examine the power supply voltage for the switchgear and the finished water pump motors. The recommendation to pump water to the Highland pressure zone in lieu of the Templeton pressure range greatly reduced the discharge pressure of these pumps. Switching from medium voltage (4,160 V) to 480 V service reduces the costs of switchgear and variable frequency drives. This change requires more Northfield pumps but the increase in number of Northfield pumps provides improved overall efficiency and more operational flexibility. Cost savings are realized from the lower cost electrical equipment. In addition, the consolidated facility greatly reduces the amount of buried ductbank and correspondingly reduces the overall cost of the project The Colorado Springs Utilities-McCarty-Carollo team has adopted a ?continuous value engineering? approach as the plant is being designed that will also continue through construction to assure the best value water treatment plant for the Southern Delivery System.

Future SDS Components

SDS is a long-term solution. Phase II of the project will include the construction of a terminal storage reservoir at Upper Williams Creek and an exchange reservoir, including return flow diversion and conveyance, at Lower Williams Creek.

Once the core components of SDS are completed and as more capacity is needed, Colorado Springs Utilities will add the two reservoirs and complete the build out of the water treatment plant and pump stations. The water treatment plant can be expanded to more than 100 million gallons per day. These enhancements will be built as demand requires, likely in the 2020-2025 timeframe.

For more information on the Southern Delivery System, visit www.SDSWater.org.

Dr. Marco Aieta, P.E., director of Water Practice for Carollo Engineers, leads Carollo in the planning and implementation of water projects, including developing strategies to help clients achieve cost effective solutions, realize water quality goals, comply with current and future regulations and gain public acceptance.

Bob Knochenhauer is project director/construction manager for McCarthy Building Companies Inc., the nation?s 10th largest domestic general contractor. The company has a diverse roster of heavy/civil projects across the country. The Water Services team offers general contracting, construction management, program management and design-build services for wastewater and water treatment projects in Arizona, California, Colorado, New Mexico and Texas.

SDS Core Components

The components in the illustration below are the backbone of SDS. The core project consists of:
A connection to the North Outlet Works of Pueblo Dam

62 miles of underground raw and treated water pipeline

3 pump stations ? the Juniper Pump Station near Pueblo Dam and the Bradley and Williams Creek
pump stations in El Paso County

A 50-mgd water treatment plant.

Colorado Springs Utilities and the other project partners can deliver water to our customers after building these components.

Carollo/McCarthy Project Highlights

  • RFP included a 30 percent design document that was the basis for the treatment plant
  • Carollo and McCarthy did a value engineering analysis of the 30percent as part of the proposal process and identified an alternative plant layout that would save Colorado Springs Utilities more than $25 million on the plant construction
  • The value added was so compelling that the client decided to select the McCarthy/Carollo team based on the proposal alone.
  • The project is fast-tracked to take advantage of favorable construction climate. ?
  • The design is schedule to be completed in 12 months.
  • The concept of designing to a budget is foremost in the project.
  • All construction components will be bid out to stimulate Colorado Springs economy.
  • The design is using continuous value engineering and continuous costs estimating to be sure to meet the schedule and provide the highest value for the costs incurred.

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