Former Albemarle County Water Manager discusses dredging of South Fork Rivanna Reservoir

(first of two posts)

Stephen Bowler

In 2003, hydrologist Stephen Bowler wrote a report that details the history of the watershed that supplies the South Fork Rivanna Reservoir. At the time, Bowler served as Watershed Manager for Albemarle County and the Rivanna Water and Sewer Authority (RWSA), and the report provided suggestions for how to further protect the watershed as the community began developing a 50-Year Community Water Supply plan.

Podcast produced by Charlottesville Tomorrow * Player by Odeo

Listen using player above or download the podcast: Download 20080929-SFR-Bowler

Five years later, Bowler is with  the Federal Energy Regulatory Commission (FERC) and works on permitting for new hydroelectric dams. Specifically, Bowler studies whether fish and other aquatic life will be impacted by such structures.

On September 29, 2008, Bowler addressed the South Fork Reservoir Stewardship Task Force with a brief update of his report. He began his comments by disclosing that he was not representing FERC, and had not received any compensation for appearing before the task force. He also disclaimed that he at one point worked for the Nature Conservancy, an organization that contributed to the community water plan.

“While working for TNC, I helped with some of the ideas about the pump-storage concept to Ragged Mountain Reservoir,” Bowler said.  Bowler added that he supports the adopted plan, but said there might be benefits to dredging.  His comments to the task force mostly dealt with the reasons for why sedimentation has occurred since the SFRR was first filled in 1966.

But first, Bowler asked each member of the task force to give a reason why sedimentation affects their interest in the South Fork Rivanna Reservoir, and he supplied several possible answers. The following are responses from the Task Force.

"Reliable water access/quantity/quality to fill Ragged Mountain Reservoir"

• Sally Thomas (League of Women Voters)
• Dennis Rooker (Board of Supervisors, Jack Jouett District) [selected two]
• Liz Palmer (Albemarle County Service Authority) [selected three]
• Chris Lee (Chamber of Commerce)
• Tom Jones (South Fork Rivanna Reservoir area landowners)*
• Mike Gaffney (RWSA)
• Holly Edwards (Charlottesville City Council) [selected three]

"Water quality/quality supporting native, riverine fauna"

• Ridge Schuyler (The Nature Conservancy)
• Liz Palmer (Albemarle County Service Authority) [selected three]
• Karen Joyner (Ivy Creek Foundation) [selected four]

"Healthy and diverse wetlands"

• Liz Palmer (Albemarle County Service Authority) [selected three]

"Water quality in general" (suggested by John Martin

• John Martin (Rivanna River Basin Commission)

"Diversity of habitat at Ivy Creek Natural Area"

• Karen Joyner (Ivy Creek Foundation) [selected four]

"Still water lake aesthetic"

• Karen Joyner (Ivy Creek Foundation) [selected four]

"Educational value of changing watershed"

• Karen Joyner (Ivy Creek Foundation) [selected four]

“Convenient access to recreational rowing”

• Mark Fletcher (University of Virginia)

"Restoration of SFRR capacity to contribute to water supply" (added by Dede Smith)

• Dede Smith (Citizens for a Sustainable Water Plan)
• Dennis Rooker (Board of Supervisors, Jack Jouett District) [selected two]
• Wren Olivier (Sierra Club)
• Holly Edwards (Charlottesville City Council) [selected three]

* Tom Jones also took issue with the way the options were phrased. “[The reservoir is] a unique riparian environment for recreation, for flora, fauna and there’s nothing like it with flowing water of this scale,” Jones said. He asked to check all the boxes.

Bowler said the feedback from the task force would help him address the technical issues. After tallying their responses, he discussed the many conceptual models that can be developed to depict how sedimentation happens. After providing intricate details of how stream flows can affect channels, Bowler then turned to answering the question – what will happen to the South Fork Rivanna Reservoir in 50 years if nothing is done to address sedimentation?

Bowler identified two options for gathering information to make a decisions on how to proceed with dredging. First, he suggested an inexpensive approach could be conducted using conceptual models by sifting through existing data (aerial photographs, previous bathymetric data). Second, he identified several ways in which the community could gather additional data. Bowler cautioned that if the community takes the second approach, they should determine the areas of the reservoir where various stakeholder interests overlap the most.

“That might help you restrict [the modeling] to the fewest number of cross-sections you need to get the information you need to get on with some decision-making, because if you model the whole reservoir, it’s going to cost a lot of money,” Bowler said.

Bowler than provided a summary of his 2003 report, which he said still accurately describes the nature of the watershed. The reservoir is silting in at a rate of about 15.6 million gallons a year, or 1% of its storage capacity. However, he added that rate can range widely depending on how many powerful storms hit the area in a given year. While the sedimentation does relate to current development in the watershed, Bowler’s report also describes how much of the sediment can be traced to agricultural practices of the 19th century.

“We logged and farmed very intensely to the point where we were down to single-digit numbers in terms of percentage of forest cover in many of the watersheds in this region, and we basically lost all of our topsoil in a short time,” Bowler said. He said much of this “legacy sediment” filled in many of the stream valleys creating large flood plains. To give a sense of scale, Bowler said archaeologists have found evidence native settlements from the 16th century that are as much as 14 feet below the existing flood plain. He claimed those geologic processes are still at work today and that efforts to reduce sedimentation by further restricting development will likely not do much to stop the sedimentation. Bowler said it might be possible to stop some of that sediment using ponds upstream from the reservoir, but that might cause other environmental problems. He did suggest that creating ad hoc fore-bays by mining sand before it enters the reservoir could be a cost-effective solution.

Bowler said if nothing is done, the future of the South Fork Rivanna Reservoir will continue to look more like a wetland in certain areas. The inner bends will fill in faster, and the reservoir will take on characteristics that are more like a river. “Parts of it are going to very attractive wetland habitats rather than a mud-hole,” Bowler said.

Bowler concluded his presentation by offering his views on dredging. He said inland dredging with disposal is rare, because most dredging done inland is done for navigational purposes and the dredged sediment is deposited at other places in the river or lake. He claimed most dredging done for capacity is done for “boutique” reasons and do not generate a large volume of sediment. Bowler did not comment directly on whether or not dredging the South Fork Rivanna Reservoir was a good idea.

John Martin asked Bowler what he would do if he were the watershed manager in 1962, and if he would recommend building a reservoir at South Fork Rivanna Reservoir given what is known now about legacy sediment. Bowler responded that the South Fork Rivanna Reservoir is unique because it has a very high “watershed to reservoir ratio” of 424  to 1. Most reservoirs are in the 30 to 60 to 1 range. He said this is one reason why sediment load is so high in the South Fork Rivanna Reservoir, but said there were too many variables to give a good answer to Martin’s question.

After Bowler’s presentation, the task force spent some time discussing how to receive public comment, and revisited the question of why the task force was created. Charlottesville Tomorrow will post that podcast and summary in a future story.

TIMELINE FOR PODCAST:

• 1:00 - Introduction of Stephen Bowler by Sally Thomas
• 2:20 - Stephen Bowler begins his introductions
• 6:20 - Bowler makes several disclaimers about his speech
• 14:30 - Bowler asks task force members to give reasons why they are interested in addressing sedimentation in SFRR
• 30:00 - Bowler gives a conceptual explanation for how erosion and deposition leads to the SFRR being filled in
• 39:40 - Bowler begins answering the question what will happen to the South Fork Rivanna Reservoir in 50 years if nothing is done to address sedimentation?
• 47:20 - Supervisor Rooker asks if there is a way to determine if models will be accurate
• 49:10 - Bowler reviews highlights of his 2003 study
• 55:40 - Bowler presents his "prognostications" on reducing sediment
• 59:30 - Bowler presents his "prognostications" on the future of the reservoir
• 1:05:55 - Rooker asks if Bowler has personally observed inland dredging
• 1:08:42 - John Martin asks a hypothetical question about what Bowler would do if he was in charge back in 1962
• 1:12:51 - Comments from Dede Smith and a question about modeling versus actual measurements to establish a baseline
• 1:19:00 - Question from Holly Edwards about what would happen to the health of the river if the dam would be breached
• 1:21:30 - Schuyler asked Bowler for his opinion on how the task force can establish a timeline for potential dredging without doing the quantitative analysis that Bowler recommended.
• 1:22:30 - Tom Jones asked if modeling could help determine if dredging would be cost-effective
• 1:25:00 - Rooker asks if modeling can be done just based on extrapolating sedimentation rates

Sean Tubbs

Comments

[Sean Tubbs]

An astute reader noticed that I had incorrectly stated that the reservoir is silting in at a rate of 15.6 million gallons a day. That should be 15.6 million gallons a year, and I've corrected the story accordingly.

[Leslie Middleton]

I attended the meeting on Monday night and, contrary to this reporter's description, it was my experience that that Stephen Bowler was leading the group through a process that he has seen helpful in other multi-party situations during his work at FERC.

He did not say it was conclusive, nor complete, but that it could serve as the basis for creating a hydrological model that, given the selected interests/goals that are input as desired results, would clarify if, when, and where dredging could take place to meet those goals.

If I were on the task force, I would have had -- as some did -- difficulty with the categories and the lack of clarity in the process that one could vote once or many times. Listing the record in your report of the meeting of who voted for what does not accurately reflect either the "votes" of the various people (some voted for one/top choice thinking that was the "rules" and others voted for everything, after they expressed difficulty with the "one person/one vote" situation).

Stephen said that this type of feedback could be used to craft a technical model that could provide some insight in to how, when, and where sedimentation was likely to occur in the future in the SFRR.

Stephen Bowler's second option for gathering information was a more rigorous (and expensive) version of the first. The first option was to collect much of the information and existing data and build a conceptual model. The second option was to get expert help to craft a (analytic) hydrologic model that could be used to explore different scenarios BASED ON OUTCOMES IDENTIFIED BY THE TASK FORCE.

This second approach is a more sophisticated -- and costly -- version of the first approach, which would be cheaper and necessarily cruder, but possibly yield some good information.] Bowler cautioned that if the community takes the second approach, they should determine the areas of the reservoir where various stakeholder interests overlap the most [in order to make sure that the inputs to the analytic model best reflects Task Force goals and has greatest opportunity to predict outcomes based on these goals, for the least cost -- i.e. rather than analyzing 25 scenarios - costly!! -- only analyze 2 to 5.]

The latter part of the meeting consisted of revisited the question of why the task force was created. This bears repeating: the Task Force was created by the City and County to look at the present and future expected conditions of the SFRR and make recommendations about next steps.

Some people think that the task force was created to examine DREDGING as a full or partial solution to meeting our water supply needs -- and that attempts to redirect the conversation about dredging by the task force leader or other participants are obstructing free discussion of a necessary issue.

My experience as a careful observer of the process is that the Chair of Task Force continues to remind people that the charge of the Task Force is NOT to evaluate dredging, nor re-evaluate the water supply "plan" that is currently approved and permitted. It is to augment the understanding of what is happening to the SFRR, especially since it is a component of that plan. The Task Force is specifically being asked to answer this question (among others): Given the approved fifty year water supply plan, and the fact that the South Fork Rivanna Reservoir is part of that plan, what will be the impact of the projected life cycle of the reservoir?

The Task Force has taken a methodical approach to trying to understand the current state of the reservoir from the point of view of a variety of uses so that it can get to the point of making a recommendation back to elected officials.

If it WERE tasked with re-visiting whether dredging should be considered in order to change or amend the current plan, then I would say that we do not have the right people at the table. It is a subtle point that, unfortunately, seems lost on those who see the Task Force (and the upcoming public comment period) as a referendum on the permitted water supply plan.

Stephen Bowler's presentation was another piece of information regarding HOW you MIGHT determine life cycle of the reservoir and, if dredging is to be done, when, where and how do you do it? Without being able to converge on the answers to these questions (the "why dredge?" that Gahagen-Bryant said was a necessary first step in the process), you can't even craft a suitable RFP that might provide the kind of answers regarding the cost of dredging that are needed.

Leslie Middleton
URL to SFRR Task Force "tasks" - or see below

www.rivanna.org/documents/steward/task_force_outline.pdf

Outline of Work for the
South Fork Reservoir Stewardship Task Force1


1. Utilizing historical, scientific and survey data, and current expert testimony,
establish a timeline spanning at least fifty years of the expected disposition of the
South Fork Rivanna Reservoir if no maintenance is performed.

2. Using this anticipated life cycle identify the impact on the ecological, recreational,
aesthetic, and water quality of the South Fork Rivanna Reservoir.

3. Receive public input on the community expectations for the future of the South
Fork Rivanna Reservoir.

4. Given the approved fifty year water supply plan, and the fact that the South Fork
Rivanna Reservoir is part of that plan, what will be the impact of the projected life
cycle of the reservoir?

5. Given the collected data, define several expected outcomes relative to the
community expectations, starting with doing nothing and including other potential
maintenance initiatives.

6. Present results and make a majority recommendation, including an outline of
needed future data/analysis if applicable, to a joint meeting of the Rivanna Water
& Sewer Authority, Albemarle County Service Authority, City Council and
Albemarle County Board of Supervisors before the end of the year.



_______
1
From the Four Board Chairmen:
Dave Norris – Mayor, City of Charlottesville
Kenneth Boyd – Chairman, Albemarle County Board of Supervisors
Donald Wagner – Chairman, Albemarle County Service Authority Board of Directors
Mike Gaffney – Chairman, Rivanna Water & Sewer Authority Board of Directors

You could provide a link to that charge.