Combined Sewer System and the Long Term Control Plan Update

Stakeholder Group – Meeting Notes

Meeting #3 – January 10, 2018

Meeting Attendees
CSS Stakeholder Group / City of Alexandria
Skip Maginniss / Emily Baker
Agnes Artemel / Lalit Sharma
Liz Birnbaum / Erin Bevis-Carver
Yvonne Callahan / Junaid Malik
Andrew Duncan
Lauren Glose
John Hill / Alexandria Renew Enterprises
Kate Mackenzie / Karen Pallansch
Stephen Milone / Liliana Maldonado
Erik Olson
Dixie Sommers
Jack Sullivan / Engineering Consultants
Chuck Weber / Justin Carl – Brown and Caldwell
Ivy Whitlatch / John McGettigan – Greeley and Hansen
Dustin Dvorak – Greeley and Hansen
Clyde Wilber – Clyde Wilber LLC

The meeting convened at 7:00 pm with welcome comments by Emily Baker, Deputy City Manager. Citystaff then gave a presentation following the established agenda:

  • Ms. Baker explained the purpose of the stakeholder meetings, outlined the charge of the group and expected feedback,and described Alexandria’s goals for the CSO program.
  • Ms. Mitchell, then reviewed the evaluation criteria survey results. A discussion about the survey results was conducted in which stakeholders expressed their understanding and interpretation of the evaluation criteria weightings that resulted from the survey. Mr. Hill noted the group may was to revisit the survey once they more fully understand the various options relative to the evaluation criteria.
  • Mr. McGettigan then walked through the various CSO Program alternatives. This began with an overview of the major components: storage and conveyance tunnels, storage tanks, maximizing flow to the plant, and wet weather treatment. He then went on to explain how each of these major components work together in the three options:
  • Option A: CSO-003 and CSO-004 are diverted into a conveyance tunnel and CSO-001 and CSO-002 are diverted into a separate storage tunnel. As combined sewage enters both tunnels, the flow is immediately sent to the treatment plant until the plant reaches capacity. When the plant is at capacity, the CSO-003/004 flows are then sent through the wet weather treatment facility where the bacteria is killed or inactivated and flows from the CSO-001/002 tunnel will be stored. Once the treatment plant and wet weather facility are at their capacity, the CSO-003/004 tunnel will begin to fill. . CSOs will only occur during extreme storm events for CSO-003 and CSO-004 and no more than 4 times a year for CSO-001 and CSO-002 in an average rainfall year.
  • Option B: All CSOs are diverted into one large storage and conveyance tunnel. As flow enters the tunnel, it is immediately sent to the treatment plant until the plant reaches capacity. When the plant is at capacity, then the tunnel begin to fill. If flow is still trying to enter the tunnel when it is full, only then will there be a CSO, typically at CSO-001. CSOs will occur no more than 4 times per year on an average rainfall year.
  • Option C: CSO-003 and CSO-004 are diverted into a conveyance tunnel. As flow enters the tunnel, it is immediately sent to the treatment plant until the plant reaches capacity. When the plant is at capacity, the flows are then sent through the wet weather treatment facility where the bacteria is killed or inactivated. Once both facilities are at their capacity, then the tunnel begin to fill. If flow is still trying to enter the tunnel when it is full, only then will there be a CSO. CSO-001 and CSO-002 will be diverted into separate storage tanks. As flow enters the each tank it will be immediately sent to the treatment plant while it still has capacity. Once the plant reaches capacity, the tanks will begin to fill. If flow is still trying to enter the tanks once they are full, only then will there be a CSO.
  • CSOs will only occur during extreme storm events for CSO-003 and CSO-004 and no more than 4 times a year for CSO-001 and CSO-002 in an average rainfall year.
  • Potential alignments through the Old Town area were shown to give the group some perspective on the areas that may be impacted. Following this general explanation of the options, a line of questioning and discussion among the stakeholder group began. Some of the questions and suggestion can be found in the questions below.
  • Mr. McGettigan thenpresented a summary of CSO performance which detailed and compared each CSOs current performance with the predicted CSO performance if each of the Options were implemented. This included a major reduction in the frequency of overflows from 60-70 down to 4 or less for all CSOs. Similarly, the volume reduction and percent capture for the system showed high levels of control for each of the CSOs.
  • Finally, Mr. Sharma thenprovided an overview of the City’s previous Green Infrastructure (GI) Plan as part of the overall CSO program. The City is implementing GI throughout the City. The 2016 LTCPU included an initial commitment of $5 – $7.5 million for GI from 2018-2035. As a part of the City’s commitment for Green Infrastructure, $3.2 million was allocated for GI in the 2018 CIP. Following this the presentation, many questions and suggestions regarding GI were put forth by the stakeholder group. Some of the questions and suggestions can be found in the questions below. In general, the Group requested analysis be presented regarding the cost effectiveness and implementation of Green Infrastructure as a means to mitigate CSOs.
  • The meeting concluded with a brief overview of the upcoming CSS Stakeholder Group meetings.

The meeting adjourned at 9:15 pm.

The following is a summary of the types of questions asked by members of the CSS Stakeholder Groupand the answers provided by City staff and engineering consultants. This summary discusses the general concepts and not the individual questions verbatim.

Can the survey be re-administered once the stakeholder group is more informed about the CSO Program Alternatives? How will the evaluation criteria survey results be used going forward? Why did the survey have the respondents rate the criteria rather than rank them?

The results of the evaluation criteria survey will be used to formulate the weightings of each of the criteria and select an Option for further development. As stated by the Group, it may be helpful to re-administer the survey once the Group has more information about each of the options. This will be considered in the future. City staff considered whether to set up the survey to rate or rank each of the criteria. Ultimately it was decided that if the criteria were ranked, one criteria could have been ranked low by a majority of the Group and would have been viewed as not important. By rating each of the criteria it allowed the Group to assign importance to them so that one criteria wasn’t weighted artificially low.

Which of the evaluation criteria take into account the impacts on historic structures and areas?

Impacts to historic areas are included under the construction impact goal even through it is not specifically called out. As with any construction project in the City, and especially Old Town, particular attention is given to how the community will be impacted both during construction and in the long term.

For Option A, how many pump stations will this design require, will all tunnels be placed under the public right-a-way, and how deep will the tunnels be?

Option A will have 2 dewatering pump stations located at the AlexRenew facility. Currently several tunnel alignments are being considered and are within the public right-of-way as shown on the slides presented. Disruption during construction will mainly occur within the public right-of-way and City parks, however there may be some instances where relatively minor work will need to occur on private property. The tunnels will be approximately between 60-100 feet underground and there will only be ground disturbances where shafts need to be constructed.

In Option B, why isn’t there any additional treatment of overflow?

In Option B, wet weather treatment is not needed because the tunnel has a larger volume to store CSO as well as convey it away from the more environmentally sensitive Hunting Creek. Therefore, overflows will occur mainly exit the system out of CSO-001 which discharges to a much larger water body that is able to better assimilate the overflows and meet water quality standards. The tunnel will store a large number of rainfall events and flow in the tunnel will be pumped to the AlexRenew plant for a high level of treatment following the storm event. It is estimated that there will only be 4 overflows per year from CSO-001 if Option B is implemented, which is a significant reduction from the current number of overflows.

Could each of these options be updated post-construction to account for a trend of larger rain events over time or more strict water quality regulations in the future?

All options could be updated in the future to address climate change or future regulations, however it would cost significantly more to do that in the future after everything is built. The City and AlexRenew are evaluating different ways to make each option more adaptable and this information will be presented at future CSS Stakeholder Group meeting #4.

How does flow from other areas, for example Fairfax County, impact the overflows and the options presented?

While flows from elsewhere in the sewer system contribute to flows at the treatment plant; they do not get discharged from the CSOs. These flows will take up capacity at the treatment plant which could prevent the CSO flow from getting into the plant for treatment.

What is the 40 year time period of rainfall data that was analyzed for the CSO performance summary?

The time period of rainfall data analyzed for the CSO performance analysisincludes rainfall records for 1974 to 2013 for the City of Alexandria. While these 40 years were used to determine the typical year, all the performance slides in this presentation representperformance averages from rainfall occurring in years 2000-2016.

What do the values displayed on the slide for load into the Potomac River represent?

The chart shows the loads in the Potomac River from the Anacostia River to the Woodrow Wilson Bridge which includes the Virginia loads (Arlington and Alexandria) and other sources. Other sources are made up of upstream loads from Fairfax County, Maryland, and the District including stormwater, DC CSO loads, and loads from wastewater treatment plants such as DC Water’s Blue Plains. The Virginia loads make up only 3% of all the bacteria load already in the Potomac and CSO-001 is only a portion of the Virginia loads.

If a more strict set of regulations were to be approved in the future that includes more nutrient management, wouldn’t CSO-001 be the most impacted by this? Would the only option be to send the flows to AlexRenew?

More strict regulations are always a concern and could be implemented at any of the City’s CSOs. For CSO-001 specifically, depending on which Option is ultimately constructed, there are various ways to address future regulations including additional storage infrastructure, conveyance to the AlexRenew facility, sewer separation, more aggressive green infrastructure, and disinfection at the CSO. The City believes that all of the options under consideration will provide significant water quality improvements for all the receiving water bodies. The City is confident the infrastructure being proposed provides far more control of CSO’s than most other CSO communities in Virginia and around the country.

How will the options presented and the wet weather treatment facility impact other nutrient loads?

This topic as well as the impact to the Chesapeake Bay TMDL will be covered at a future meeting.

When observing the information presented showing that CSO has the fewest number of overflows per year, CSO-001 has seemed to have been discussed in the past as having overflowed the most;how could it have least overflowed the fewest number of times?

The number of overflows vary with every year. Some years there are more overflows than others and these values in the slides are just the averages. CSO-001 has a lower number of overflow events, but the events themselves at CSO-001 tend to be longer and have more overflow volume compared to the other CSOs.

In option B, the majority of overflows happened at CSO-001. Data presented in the CSO performance show that CSO-001 has the largest volume of overflow, so why isn’t CSO-001 being addressed as much as the other outfalls in this option?

CSO-003 and 004 impact the Hunting Creek which has the Total Maximum Daily Load limits while there is no TMDL requirement in the Potomac. The 99% reduction is required at Hunting Creek, not at the Potomac River and Oronoco Bay.

Won’t additional overflows at CSO-001 impact the quality of water at Oronoco Bay?

Oronoco Bay is essentially a part of the Potomac River as it is flushed out twice a day due to the tide cycles. Based on work done by the District Depart of the Environment, all of the Virginia loads (this includes flows from Fairfax County, Arlington, and Alexandria) only account for about 3% of the total bacteria in the Potomac River. CSO-001 is only a portion of that 3%, so it has minimal impact on the water quality of the receiving water.

As displayed in the “why not zero overflows” graphic, is the trend line shown of significantly increasing cost with minimal increase in tunnel size similar for other CSO systems that have implemented similar projects?

Yes, this is a common “knee of the curve” analysis recommended in EPA’s National CSO Policy and has been done for other CSO communities.

Was the previously submitted CSS Long Term Control Plan Update that the Stakeholder Group reviewed in 2016 submitted to the Virginia Department of Environmental Quality, and if so, was the CSS plan approved? Why does the 2016 Plan need to be changed?

The 2016 LTCPU was submitted to VDEQ in August of 2016. VDEQ provided comments and requested some additional clarification. The 2016 LTCPU was revised to address those comments and resubmitted to VDEQ for approval in December of 2016. The plan was awaiting VDEQ approval when the legislation was enacted requiring significant revisions to the LTCPU. The way the legislation is written, there is a much shorter timeframe (completed by July 1, 2025) and the 2016 plan had a much longer duration to complete construction and allowed the use of the complementary strategies to help to meet the requirements of the TMDL in addition to the gray infrastructure. However, with the shorter timeframe the focus is on gray infrastructure to meet the CSO reduction requirements. Therefore, the City must look at implementing larger and/or additional gray infrastructure in order to meet the legislative deadline.

What are the costs for each of the options and what does it include? In order to properly evaluate the options and provide a recommendation we need to see the costs.

The cost for each option will be presented at the next CSS Stakeholder meeting. These costs will include the capital costs required to construct the infrastructure as well as 20 years of operation and maintenance costs. This information as well as the performance of each of the options should provide enough information to adequately evaluate each of the options.

Many questions about Green Infrastructure were asked regarding the City’s commitment GI in the LTCPU: how it will be implemented as a complementary strategy, if GI on private property has been considered, and if it is a cost effective measure to reduce the size of tunnels or tanks?

The City is taking all these questions under consideration and is pulling together more information and strategies specific to the LTCPU. This information will take some time to gather and will be presented at future CSS Stakeholder Group meeting #5 in late February.

What is the plan to deal with the potential “rate shock” from the community as the project begins to be fundedthrough citizens’ sewer service bills, especially in the low income communities in our City? How will be this be made affordable?

Information on costs and rate impacts will be presented at the CSS Stakeholder Group meeting #5 at a date to be determined.

The next CSS Stakeholder Group meeting will occur in February 1, 2018in the Sister City’s Conference Room (room 1101) at City Hall.

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