Consultant's Corner: Progressive Design-Build Project In Texas Saves Time And Resources

By Gus Hrncir, DBIA, CH2M HILL Sales Manager and Dave Schoster, PE, CH2M HILL Project Manager

Public-private partnerships and alternative contracting approaches have picked up momentum in the U.S. water market as municipalities and utilities face challenges of funding capital improvement projects, while keeping rates low for their customers.

The City of Dallas Water Utilities (DWU) manages the largest water distribution system in the U.S., and its wastewater collection system consists of more than 4,200 miles of pipes (from 6” to 120” in diameter) and associated components, including more than 40,000 manholes, 15 lift stations, 10 customer city meters, 14 rain gauges, and 50 permanent flow meters. The collection system conveys wastewater to two treatment plants: Central Wastewater Treatment Plant (CWWTP) and Southside Wastewater Treatment Plant (SWWTP), both advanced activated sludge facilities. The CWWTP is permitted at 150 million gallons per day (mgd), and the SWWTP is a 110-mgd permitted flow plant.

As a part of DWU’s collection system, there are also several diversion structures. One of these structures is the Sunbeam Diversion Structure. The structure consisted of a receiving influent structure and two above ground concrete effluent structures, equipped with two 60” and 96” controlling gates. The Sunbeam Junction Structure receives approximately 66 million gallons of wastewater per day through a 60” wastewater main from the Upper White Rock sewer shed and a 78” wastewater main from the Lower White Rock sewer shed. Using gates inside the structure, flows are controlled and diverted to either CWWTP or SWWTP. The structure is a critical part of the collection system because it reliably diverts wastewater flows to one plant if capacity limitations arise due to construction, maintenance, and/or process upsets at the other plant.

The Sunbeam Junction Structure, built in the early 1980’s, began to deteriorate and had exceeded its service life. Due to the harsh environment, corrosion had eaten away at the concrete walls to the point where the aggregate was exposed. In 2008, a structural investigation was conducted to determine the severity of the corrosion, and it concluded that rehabilitation or replacement of the structure would be required within five years. To avoid system failure, DWU was faced with making a decision on how to proceed. Tackling this critical, time-sensitive project, DWU embarked on an innovative solution to reconstruct its Sunbeam Junction Structure and implement remote control capabilities for the gates.

For years, DWU had utilized the traditional, design-bid-build delivery method to build or repair its aging infrastructure, so undertaking a project under a Design-Build contract was a new approach for the utility — but one that promised faster, safer, cheaper results, with minimal risk. In 2012, the city contracted CH2M HILL to serve as the design-build delivery firm, using a progressive estimating model. The scope of work associated with the $3.8 million Sunbeam Junction Structure improvements project included designing, permitting, constructing, and commissioning a new diversion structure, along with flow measurement and remote monitoring and gate control, demolition of the existing diversion structure, and a new access road.

One of the biggest factors Dallas grappled with when making the decision to proceed under a design-build contract was the need to continue operating the Sunbeam Junction Structure without interrupting downstream flow through the interceptor and to both wastewater treatment plants. With flows ranging between 50 mgd in dry weather and 143 mgd passing through in wet weather, it was critical to ensure the facility remained operational throughout the construction phase while not encountering any spills. The project also required innovative construction solutions and planning, as the junction is located in an active flood zone. The site, inaccessible during floods, lacked remote control capabilities, making it difficult to operate in inclement weather. By adding remote control capabilities, operators would gain the ability to open and close the gates from an offsite location.

The Sunbeam project was the first design-build project undertaken by DWU. Placing responsibility on a single contractor not only made logistical sense, but it enabled DWU to achieve significant cost and time savings, while also ensuring no harm was done to the wastewater system operations, and the potential for wastewater spill into a sensitive environmental area was mitigated. The project served as a pilot for larger design-build projects, allowing DWU to test and learn from this delivery approach.   

CH2M HILL’s delivery approach mitigated all risks, delivered the work safely without any incidents, on time and below the guaranteed maximum price. In fact, CH2M HILL returned approximately five percent of the total project value back to DWU — some of which they used to add more features to the Sunbeam Diversion Structure. CH2M HILL exceeded DWU’s expectations in the design, permitting, preconstruction, construction, and startup of this critical diversion structure.

The entire project was completed in 21 months, from design phase to construction and commissioning.

Success Factors

• Communication and Collaboration – Given their previous design-bid-build experience, DWU expected the Sunbeam project to cost more than the contracted value, while having to constantly “police” the contractor’s performance. DWU soon realized that their preliminary expectations were far from the reality. Early in the project, DWU learned the progressively-estimated, open-book approach was extremely valuable in decision-making. Their involvement in design reviews allowed them to evaluate potential deviations to the baseline scope and understand the cost and schedule implications of their decisions. Another value was the use of contingency dollars within the established guaranteed maximum price (GMP) to pay for unanticipated changes, risk items, and added features that were not included in the baseline scope.
• Safety/Environmental Considerations: Achieving Target Zero Goals –To create a safe working environment for the Sunbeam project (that was highlighted by no incidents or accidents during construction), CH2M HILL focused on project specific training, open communication, and early and frequent planning. CH2M HILL created a culture of safety that started during the design phase and provided project and task specific training for subcontractors throughout the project and during the construction phase. Daily pre-task planning and “toolbox” meetings were held with field personnel to provide insight into the safety procedures for upcoming construction activities. These meetings provided an opportunity to review safety hazards and requirements and safely plan daily work. Due to the remote location, CH2M HILL also hired a standby rescue team to provide onsite emergency rescue during ‘Permit Required Confined Space Entries’ in critical tie in events.
• No Spills Through Innovative Construction Approach – The Sunbeam Junction Structure infrastructure was nearly 30 years old and some piping was older than 60 years.  With the fragile conditions of existing structure, unknown condition of the existing piping, depth of the pipe, and location in an active flood plain and environmentally sensitive wetland, the risk of a spill was high and its impacts extremely high if it were to occur. CH2M HILL developed an innovative approach to temporarily support the influent and effluent piping while building the new diversion structure around it. This allowed CH2M HILL to mitigate the risk and costs of bypass pumping and allowed for a simple tie in and decommissioning of the existing structure once the new work was completed.
• Time – To eliminate constant alignment challenges typified by maintaining multiple schedules, CH2M HILL produced a single, critical path method (CPM) schedule that incorporated all design, preconstruction, permitting, construction, startup, subcontractor and vendor activities. This resource and cost loaded, CPM schedule featured detailed activities for all phases of work, and included schedule logic to identify predecessors, successors, and dependencies to each task. The total project, delivered in 21 months, would have taken an estimated 30 months under a traditional design-bid-build delivery method.   
• Confidence in Project Costs – As DWU performed periodic design reviews and discussed owner-driven deviations to the baseline scope, CH2M HILL determined the cost and schedule impacts of the changes to support DWU’s decision making process. Timely information on impacts of changes helped to identify potential tradeoffs to offset costs, schedule impacts, or reveal opportunities for enhancements. The process gave DWU the confidence in actual project costs so they could make informed decisions prior to adding scope to the project. To rapidly facilitate changes in scope, DWU allotted themselves a contingency within the original GMP for anything out of scope or additions above the endorsed baseline scope and budget. At the conclusion of the project, CH2M HILL saved and returned $161,000 back to DWU, not to mention the approximate $76,000 that DWU utilized for value added items not included in the initial baseline scope.
• Improved Junction Structure – The Sunbeam Junction Structure was designed as a state-of-the-art diversion structure. Flows can now be remotely monitored utilizing the three new flow meters and split to divert flows to one of two wastewater plants as conditions change. These features, along with a robust protective coatings system, 316 SST gates, and improved security features, improve durability and reliability, as well as make it less maintenance intensive.

The Sunbeam Junction Structure is a good example of how alternate project delivery benefitted a forward-thinking Utility to successfully deliver a critical, time- and cost-sensitive project. DWU decided to use a progressive design-build approach to complete the project more rapidly, encourage innovation, gain efficiencies by leveraging its ongoing collaboration with CH2M HILL, better allocate project risks, and control project costs. With the successful completion of the Sunbeam Junction Structure project, DWU continues to improve and evolve its application of the design-build delivery approach and is beginning to look for other opportunities where this delivery approach will benefit them and their customers.

Gus Hrncir is a Business Development Manager at CH2M HILL, focused on alternative project delivery. He brings 9 years of experience in providing development phase leadership and capture management of large infrastructure projects, focused on design-build, design-build-operate, construction manager at risk, and Public-Private Partnership (P3) delivery models. His attention has been on water and wastewater treatment, water quality, water resources, watershed management, groundwater management, capital improvements planning, water legislation and regulation, highway and transportation, and nuclear site decommissioning. He currently resides in Denver with his wife Janice, their kids, Garrett and Shelby, and their dogs, Major and Tuco. He can be contacted at Gustav.Hrncir@ch2m.com.

Dave Schoster is a registered Professional Engineer and Project Manager at CH2M HILL in the Corporate Construction Group, focused on the delivery of at-risk water projects. He brings 13 years of experience in providing design, preconstruction and project management leadership to the delivery of water projects utilizing the progressive design build delivery model. His attention has been on the successful delivery of at-risk water projects and developing trust and confidence with the clients with whom he serves.  He currently resides in Gainesville, Fl with his wife Rachelle, and their children, Hayden, Hailey and Harry. He can be contacted at Dave.Schoster@ch2m.com.