Facility Planning in a Dynamic Regulatory Framework: The Rockaway WWTP
- Norman Bradley - Hazen and Sawyer
The Rockaway WWTP is the New York City Department of Environmental Protection (DEP’s) smallest, most underloaded, least energy efficient, and most vulnerable wastewater treatment plant. The plant has not received a major rehabilitation since the 1970s, and the aged infrastructure was further compromised by Hurricane Sandy in 2012, which left all critical plant systems submerged. DEP noted low influent flow rates – the plant typically receives 35-40 percent of its 45 mgd rated capacity – and the potential to consolidate treatment at the 26th Ward WWTP without having to increase the receiving facility’s capacity. Separating the two plants is 5-mile wide Jamaica Bay, a National Park and critical environmental resource. DEP engaged in detailed facility planning to study the costs, risks, liabilities, and benefits to consolidation versus maintenance of treatment.
Over 100 facility planning alternatives were developed to capture a wide range of future treatment paradigms for Rockaway flow. A series of workshops were used to vet, scrutinize, and evaluate treatment concepts from a variety of stakeholder perspectives. This feedback helped DEP shortlist 12 and ultimately three concepts for detailed facility planning.
Alternative #1 is maintaining the existing treatment paradigm and reinvesting in Rockaway as a viable long-term wastewater treatment plant. The team performed facility inspections and interviewed key staff to define the scope and timing of necessary upgrades. A key finding was the extent of short-term infrastructure liabilities; a $180M to $220M investment is needed within a 10-year window to maintain operations and meet short term regulatory and climate change requirements.
Alternative #2 involves constructing a 7.5 mile conveyance via Horizontal Directional Drilling and Open Cut construction along a combination land and water route. This option involves pressurized flow and the construction of a pumping station on the Rockaway site. A key consideration for this alternative is risk tolerance for non-redundant critical infrastructure, as the favorability of the economics is dependent on single-pipe construction.
Alternative #3 involves the construction of a 5-mile long, 12’ foot finished tunnel underneath Jamaica Bay via tunnel boring machine (TBM). This alternative includes a pumping station on the 26th Ward side, which is preferable from an energy efficiency (less headloss/energy consumption) and cost (energy on the Rockaway peninsula is 36% more expensive) perspective.
To capture the scope, cost, and timing of various elements that comprise these three alternatives, the team built an economic model to analyze the Net Present Value of these three alternatives. The NPV analysis includes a regression analysis of treatment plant expenses, as DEP’s operating data indicates 26th Ward will operate more efficiently in a consolidation scenario, as pumps, blowers, and other key equipment would be operating closer to its design conditions. This economic analysis was evaluated over a 100-year horizon to account for the differing anticipated lifespans of tunnels, shallow conveyance, and aboveground structures and process equipment. Accounting for known liabilities, regulatory commitments, and risks, the payback period for consolidation via TBM is on the order of 25-25 years, with HDD paying for itself on the order of 15 years.
A challenge for Rockaway facility planning was the dynamic nature of the underlying regulatory and climatic environment. For example:
- Maintaining treatment at Rockaway would leave critical treatment infrastructure on a barrier island susceptible to extreme weather event, while consolidation would relocate treatment to an inland treatment plant at a higher elevation. While some assets at Rockaway will be hardened, the majority of assets would remain at risk.
- Maintaining treatment at Rockaway leaves DEP with the regulatory risk of being required to upgrade this facility to higher levels of treatment. DEP has already invested in additional Biological Nutrient Removal upgrades at 26th Ward.
- Consolidation via TBM offers the potential for partitioning the tunnel for alternative use. For example, up to 18 million gallons of the tunnel could be used for in-line storage of Combined Sewer Overflow (CSO) flow, improving the percent capture of CSOs under the City’s Long Term Control Plan.
- Alternatively, the partitioned space could be used for relocating the 26th Ward plant outfall, which would proactively resolve other regulatory risks for the 26th Ward WWTP.
These synergies were proactively included within the economic analysis and facility planning process. The scope, cost, and most probable timing of each were added in a transparent fashion, allowing for quick recalibration of the facility planning “answer” depending on the width of the facility planning question being asked.
Through the workshop process, it became apparent that nonmonetary attributes would drive decisionmaking in parallel with project economics. Which nonmonetary variables are critical is dependent upon the alternative in question as well as the perspective of the stakeholder being asked for feedback. The team utilized the Envision framework to quantify the nonmonetary long term environmental value of the shortlisted alternatives in a credible, transparent, and concise fashion. Envision supported consolidation via TBM tunnel as the most environmentally friendly long-term solution. The analysis is driven by the improved Quality of Life for Rockaway citizens through the potential decommissioning of the Rockaway WWTP and repurposing of the 17 acre site for alternate use. Also, the tunnel presents potential long term synergies with regulatory programs, reduces climate change risk, and provides the minimum long term energy consumption treatment paradigm. Consolidation via HDD scored moderately well due to Quality of Life improvements for Rockaway citizens, but lost points due to the relative lack of synergies with regulatory programs and the disruption for residents and commercial establishments along the 7.5 mile route.
DEP is not the first utility to study treatment plant consolidation, but what makes this project unique is the scale and scope of the planning study. Decommissioning a 45 mgd plant and construction of a tunnel underneath a National Park would be unprecedented domestically, and each option carries at least $300 million of potential investment over a 25-year period. The economic analysis, Envision screening, and the fundamentals of this facility planning process to look at both current and future liabilities and risks will inform the ultimate decision, which is anticipated 1Q 2015 and will be shared at WEFTEC 2015.
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