TOWN OF ARLINGTON VISION 2020 ENVIRONMENT TASK GROUP
RESERVOIR COMMITTEE
December 10, 2001  Meeting Notes

Some of the major points were:

• A review of a 1999 consultation between the Reservoir Committee and Karen Pelto of the Mass Marine Fisheries and Wildlife Riverways Program. Back then, Karen presented a nascent program that has not substantially progressed. This consultation did not develop into a proposal or further contacts.
  
• There is little experience in Massachusetts with dam removal, and a lack of confident process. A large "triage team" of interested bureaus (EPA, DEP, Dept MFW, etc.) is assembled for site assessment.
  
• One dam removal project in Massachusetts (Crane Paper Dam) exceeded initial cost estimates ten fold, because of the discovery of contaminated sediment
  
• Dam removal would require extensive physical modification of existing berm. There might be negative or no aesthetic benefit.
  
• There would still be the need for a design storm flow analysis, that might impact feasibility
  
• Recreational uses would be impacted or eliminated. For example, the earthen liner of the Town Beach is highly permeable, and loss of the Reservoir would require it to be fortified somehow.
  
• Intuitively, existing flood control benefits of the Reservoir would be diminished. This could impact down stream flooding around Mill Brook.
  
• The resulting habitat and water level change would trigger a MEPA review process. This could be a lengthy and expensive process.
  
• Study costs simply to understand preliminary uncertainties could be high (> $100K)
  

Cathy mentioned that the US ACE might pay for a study. She cited an aborted project - the Dorchester Lower Falls on the Neponsett River.  There was some discussion of its relevance to the Reservoir. For instance, a major interest in this project was that it was involved in a coastal fish hatchery area, and this gave it special consideration for funding.

The dam removal discussion tailed into a number of digressions - property boundary issues with Lexington, ACE guidelines for tree management on levies, the size of beavers in Ayer (c. 80 lbs.), permeability and soil characteristics of the Town Beach, conduit maintenance issues down stream from the Reservoir on Mill Brook. Finally, Rich declared an informal consensus that dam removal would not be pursued. There was no objection or call to extend the question. Discussion moved to the summary of the preliminary dam rehabilitation report.

Dam Rehabilitation Preliminary Report and Discussion

Mark lead the overview presentation of the preliminary W&S proposal, and fielded questions on technical details and costs that came up in discussion. Readers of these notes are referred to the draft copy of the W&S preliminary report. Readers are reminded that some of the specifications in the 12/10/01 draft are already obsolete (e.g. the need for a low water outlet, major rehab of the Beach berm.).

The estimated project cost is around $2 million. Mark described the proposed highlights as:

1) A new 65 ft emergency spillway, grassed in, spanned by a pedestrian bridge
2) A new control gate. The control level would be 153'-158'. This would preserve the current operational characteristics and have "least regulatory impact".
3) Upstream face of the Res berm all cleared of trees. Some tree clearing on downstream side. "Rip rap" all restored.
4) "stump dump fill" gets major regrading. Containment with "Gabian wall". (4:1 gentle slope down to Mill Brook. Some fill is disposed off site.
5) Wide area of berm gets some existing trees saved.

The dominant theme during discussions was how to contain the cost of the project, and also how to get reliable estimates for different line items of the project. There was a brief review of the history of the DEM's involvement and the rationale for the high standard for safety mitigation (that is, regarding why this is considered a "high hazard" dam). There appeared to be agreement that the repair project should be done.

The two main focuses for cost control were first, the delineation of the extent of the berm that would require repair. And second, the specifications for stump dump restructuring that are required to meet DEM's safety requirement, ( for instance those modifications to enable monitoring of the "toe" of the dam) as opposed to those restructured elements that are either aesthetic, or bear only on Mill Brook hydrological issues that are outside the scope of DEM's concern. The thought being that it was important to understand what specifications were desirable but were not necessarily required.

The stump dump discussion came first. Mark described the quality of the fill - structurally flimsy, not toxic, but not playground material. (It's coal ash and wood chip material, mostly.) An important, and expensive, line item in the budget is the proposal to regrade this "stump dump fill", cap it, shore up its structural integrity, and secure the back side, above the Mill Brook, with a gentle grade slope (4:1) and contain it with a "Gabian wall". This plan offers numerous opportunities for attractive landscape, and solves the problem that stump dump fill can wash into Mill Brook, blocking the channel. There was uncertainty about whether or how much rework was actually required by the DEM. Rich didn't seem to think that DEM required that anything be done with the fill. Mark thought some minimal work would be necessary to enable monitoring of the berm. The Mill Brook issue is certainly not part of the DEM's dam concern. Phil thought it likely that the stump dump part of project could be scrutinized for its essential elements, and the rest dealt with independently.

On the topic of trees and rip rap repair, there is still no fixed, confident, delineation of the section of the berm that will require repair. This would certainly be discovered in the final plan, but Mark was encouraged to get a fix on this early on. There is a potential cost savings, and aesthetic benefit, to keeping the extent of berm repair to a minimum. Mark thought this would have to be negotiated with DEM. He also thought there could be cost savings by reusing some existing material for rip rap repair.

Mark described the specification for the emergency spillway - 65 feet with a foot bridge. The surface (face) will be structurally solid, but "grassed in", so the appearance should not be unattractive. Mark mentioned that it is feasible to split the spillway into two or more sections, but this did not generate much interest. Two factors enabled the spillway to be smaller than initially thought. First, DEM has agreed to a 500 year storm event for the design target, rather than a stricter 1/2 PMF standard. Second, a site survey revealed more shallow depths than those of some historic records, and this relaxed the requirements on the dam design. The description of the spillway was received favorably. Likewise, there was no issue with the description
of the new control gate. Mark mentioned he hoped to get cost savings in the specification of the control structure by foregoing a low level outlet.

Regarding the spillway width, it was noted that the DEM's consent for the 500 year storm event design target was given to Mark in email. Casual prodding has not produced a paper document from DEM, but Phil speculated that email is okay.

Scheduling, Project Phasing

There was a general discussion of project schedule. Weston & Sampson has to write a final plan, that can be used for bid documents. Rich thought we need 14-16 months for "permitting". There has been an informal goal held by Rich, Mark and the Res Committee, to try to stagger the project over 2 or 3 seasons so that the Beach operations (and revenues) would not be interrupted in any season. Originally, the project dates were hoped to run from fall '03 to '05, but upon discussion people thought that it's more realistic to plan to start in '04. The idea to stagger the project got a lot of scrutiny from Tony and Phil. Their concern was first how that would affect the contract. That is, would anyone want to bid on a staggered project. Rich thought so. Second, there were some speculations, pro and con, of how staggering the project would affect the funding. For instance, would the added cost of a staggered project be offset by the savings of pushing out the funding? Or is it cheaper to try to pack it all into one construction season. One assumption is that a contractor might prefer to control his schedule and do the job in one season.

There was a lengthy discussion about finance and project authorization which was frankly over my head, so I am not able to report it accurately here. No decision was made, and my notes in this matter are intended to give the flavor of the discussion and some of the issues at stake. The discussions focused on the source of funds (capital budget and/or Water and Sewer Enterprise Fund, or some combination). Whether a prop 2 1/2 override, or a water and sewer rate increase were at stake. Whether this expenditure, might deplete the Water and Sewer fund, thereby impacting the roll out of other water and sewer projects already slated. (Rich thought not.) Whether and how the staggering of the project would make it easier to finance. Phil repeated his interest that the stump dump phase be stretched out. The assumption was that the project could be authorized by a vote of the Board of Selectmen.

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