Climate Change Is Upon Us — How Will You Plan For Its Impacts?

Believe it or not, municipalities are seeing changes in the environment, and are moved to act accordingly.

By Paul Birkel, PE, senior VP, Wright-Pierce

We’ve heard the national debate on global warming and climate change. Many challenge the impacts of greenhouse gas emissions on changes in our planet and our climate. One could easily point to recent cold winters as evidence that the planet is “not warming.” How could it be after one of the coldest, snowiest winters in years?

Reality Check
Consider that the world’s population is steadily increasing and that large populations in developing countries are continuing to advance toward a higher standard of living. This leads to the combustion of more fossil fuels and may further increase greenhouse gas emissions. Scientific evidence of impacts is mounting, and previously developed predictions of changes in sea level and water temperature are being eclipsed by actual observations. Storm characterizations such as 25-year storms are occurring not 25 years apart, as the categorization would suggest, but much more frequently. Not only are they more frequent, but these storms are increasingly more intense, often accompanied by powerful storm surges. As a utility manager, how will you prepare for the future? What legacy will you leave your community with regard to planning for the future to address the impact of climate change on your facilities?

Forecasting The Future
Wastewater facility plans, comprehensive plans, and the like have, traditionally been our tools to take a complete look at our wastewater facilities, consider replacement of antiquated equipment with modern, more efficient equipment, rehabilitate structures and buildings, and consider more energy-efficient processes. Sewered growth projections are made and the impact of growth on the ability of the facility to consistently meet discharge permit requirements is evaluated. Potential future regulatory requirements are assessed, and likely order-of-magnitude costs developed to address these possible distant effluent discharge limits. One ingredient missing in many of these plans is the impact of climate change.

Wastewater facility planning represents a logical opportunity to address climate change impacts and allow for capital cost projections to address potential issues. But what are these issues and what impacts might they have? As you would expect, they are different for each facility based on location, elevation, the particular characteristics of each treatment facility, and (perhaps) air and water temperature increases and sea level rise.

The South Portland Plan

A recently developed facility plan for the city of South Portland, ME, attempted to address the impacts of climate change on the wastewater treatment facility. City management had the foresight to invest in the necessary evaluations and assessments to quantify what the future may hold, as well as what would be needed to meet those challenges. This is the first step in their process to address climate change at all of their city-owned facilities.

Clarifier at the South Portland wastewater treatment facility.

The city’s treatment facility is located adjacent to the Fore River and Portland Harbor. While the facility has no direct ocean exposure, the Fore River drains to Casco Bay and the Atlantic Ocean. Changes in sea level/storm surge and increases in air/water temperatures present the primary concerns to the facility from a climate change standpoint. Future estimates for sea level and air temperature increases were taken from a 2009 report, titled Climate Change in the Casco Bay Watershed, by a team of scientists from the University of New Hampshire, the University of Massachusetts Amherst, and ATMOS Research and Consulting. For sea level rise, the low-to-high range of possibilities suggests an increase of water level by 2050 of between 0.7’ and 1.4’, and a range between 1.4’ and 5.4’ by 2100. The recently published Fifth Assessment Report from the Intergovernmental Panel on Climate Change (IPCC) confirms the likelihood of sea level rise of this magnitude. Likewise, increases in air temperatures are estimated, with the magnitude of peak daily temperatures projected to rise by 4°F to 12°F by 2050, and by 6°F to 20°F by 2100. The air temperature increases will also result in increases in wastewater and water body temperatures.

The air and water temperature impacts are fairly straightforward to assess, since they reflect requirements at more southerly regions. At activated sludge facilities with fine bubble aeration, like South Portland, increased air temperatures may increase the required size of blowers to provide sufficient air. Rising water temperatures could be a good or bad thing depending on the treatment process and the need to avoid nitrification or nitrify, as nitrification will be accelerated with warmer temperatures. For the South Portland facility, the blowers are sufficiently sized to handle the increased air temperature for the current 20-year planning period. A future total nitrogen limit is considered likely as the Maine DEP develops ambient water quality criteria for Casco Bay. In this regard, the anticipated increase in wastewater temperatures might be considered beneficial.

The facility is currently able to discharge by gravity to its receiving waters under current peak flows and a 100-year storm event, including the storm surge effect. However, rising sea levels present two significant challenges at the South Portland facility:

• Increasing sea level will correspondingly increase the 100-year flood elevation and require effluent pumping, affecting both capital and O&M costs.
• Higher sea levels will flood much of the treatment facility grounds, requiring a dike to protect certain facilities.

In all, the city is faced with future construction of a 66-MGD effluent pump station and construction of a perimeter dike to protect the treatment facility. Projected costs, in today’s dollars, are expected to be in excess of $16 million.

While it is not expected that these improvements will be needed within the next 20-year planning period, they establish a benchmark for future consideration. Water levels can now be monitored over the upcoming years and compared to the study projections. Will conditions be better than estimated or will they be worse?

Conclusion
There is plenty of uncertainty in what will happen. Our global environment is extremely complex. We may, as a planet, significantly lower emissions with major changes in energy use. We may continue at the current rate with conservation measures offsetting population growth. Or we may see increasing emissions due to the growth in Earth’s population and an increased standard of living in developing countries. Each of these scenarios has corresponding impacts on the magnitude of temperature and sea rise that will occur. These scenarios bracket the range of possibilities, and your facility planning efforts should include an assessment of this range to allow a dialogue to begin — a dialogue about how and when changes need to be incorporated in our facilities to safeguard their operation and the environment.

Paul Birkel, PE, is a senior VP at Wright-Pierce and manages the company’s wastewater engineering division. Birkel has more than 26 years of experience, largely focused on municipal wastewater engineering activities including studies, evaluations, facilities planning, design, construction administration, and start-up.

About The Author

Paul Birkel, PE, is a senior VP at Wright-Pierce and manages the company’s wastewater engineering division. Birkel has more than 26 years of experience, largely focused on municipal wastewater engineering activities, including studies, evaluations, facilities planning, design, construction administration, and start-up.