Conservation Commission - Dec 3rd, 2020

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These notes cover one item on the Conservation Commission's agenda -- a working session to discuss the Thorndike Place comprehensive permit. Attendees included BSC (Civil engineers for Thorndike Place), BETA Group (Arlington's peer review consultants), and representatives of Arlington Land Realty (the applicant). Meeting materials were available from

(Susan Chapnick, Conservation Commission Chair) Ms. Chapnick explains the conservation commission's role in this process. Under 40B, the Zoning board of appeals is responsible for administering Arlington's local wetlands regulations. The conservation commission's most recent comments to the ZBA were written on Nov 20th, and these are available on the ZBA section of the town website. Tonight's discussion is intended to be a free exchange of ideas, so that the commission can advise the ZBA, determine if additional information is needed, and so on. This discussion is not a hearing.

(John Hession, BSC) Mr. Hession describes Thorndike place as a 176-unit residential development, in a single building that's between three and four stories tall. There will be 239 parking spaces, 204 of which will be below grade, in a parking garage. There's a "grasscrete" emergency access route around the perimeter of the building. Paths in the rear will be constructed of porous asphalt, leading to playgrounds and facilitating bicycle transit. There are patio areas in the rear and a garden amenity area in the front.

BSC performed additional wetlands delineation work, which was submitted on Oct 19th. On Nov 3rd, they submitted a report on existing conditions, new 3D architectural drawings, an updated site plan, a stormwater report, a wildlife habitat and vegetation report, and updated waiver list, and a statement of compliance with Arlington's master plan.

The wetlands delineation was reviewed and confirmed by BETA Group, and it included an analysis of the floodplain. The project will provide 2:1 compensatory flood storage, and BETA has reviewed the volumetric calculations.

The wildlife report shows a significant amount of invasive plants in the area and limited wildlife habitat. BETA concurred with the findings in this report.

BSC is working to address BETA's comments on the stormwater report.

Three areas of the project have impacts on the Food plain, for a total of 3,614 square feet. The project will provide 7,228 square feet of compensatory storage with little disturbance to adjacent upland resource areas (AURAs).

After the latest delineation, there will be 2,200 square feet of work in the AURA. No work will take place in the wetlands or in the 25' no disturb zone.

During BSC's October site visit, they checked for isolated vegetated wetlands (IVWs) behind Dorothy road, and found none. BETA confirmed this finding.

(David Kaplan, Conservation Commission) Mr. Kaplan asks if floodplain calculations included the patio areas in the rear of the building.

Yes, they included the patio areas.

(Todd Undzis, BETA Group) Mr. Undzis says that BETA Group is providing peer review consultation for the project.

The stormwater management system contains two subsurface infiltration systems and a rooftop detention system. Runoff calculations from the roof have yet to be finalized, and there will be further review in this area. He believes the system will function up to a 25 or 50 year storm. The site will need to be graded such that additional flow doesn't run into the underground garage. Mr. Undzis sees the need for some additional minor grading adjustments.

A drainage trench is proposed in front, serviced by an infiltration area on the left of the site plan.

At the time of their last communication, BSC was planning to dig test pits to determine the seasonal high groundwater mark; Mr. Undzis thinks that will be an important consideration.

The site footprint has been greatly reduced, so the main issue is disposition of roof water.

Mr. Undzis feels comfortable with the 2:1 compensatory flood storage calculations, and believes that planting issues can be ironed out as the design progresses.

(Julia Stearns, BETA Group) Ms. Stearns confirmed the delineation boundary. She examined the area where there was concern about IVWs and found no hydrological evidence or wetland vegetation. They used historical aerial photographs to look for evidence of wetlands filling, and found none.

Ms. Stearns agrees with BSC's finding regarding habitat. The site contains numerous piles of asphalt, a lot of invasive plant species, and minimal habitat for wildlife. The homeless encampment deters wildlife from using the site. The site is semi-fragmented with paths leading to the greenway. She agrees with BSC's assessment of the site, and states that construction is completely outside the 25' no disturb zone.

(Susan Chapnick) Ms. Chapnick would like to discuss the salient areas of the conservation commissions letter to the ZBA: wetlands, stormwater management, the floodplain, wildlife, and a conservation restriction.

Wetlands delineations.

(Susan Chapnick) Ms. Chapnick says the commission has concerns about isolated wetlands. She says the commission received a letter from the town engineer, which states he's observed standing water in the area. She suggests digging test pits to check for evidence if IVWs.


(Susan Chapnick) Ms. Chapnick is pleased to see a 2:1 compensatory flood storage plan, and BETA's verification of it. She's concerned about the location (lower right area in the site plan). She asks why it can't go where the homeless camp is currently located. She suggests looking at updated storm models and considering a higher base flood elevation. She'd also like to hear about how the floodplain will be restored after the work.

(Todd Undzis) Mr. Undzis says that BETA looked at the Massachusetts coastal flooding model, and Cambridge's flood elevation viewer. Cambridge's 2030 projections correlate with current models; the 2070 projections are higher. A 100-year storm surge in 2070 would have a flood elevation of about 11 feet, which would completely cover Dorothy road and the surrounding neighborhood.

(Pam Heidell, Conservation Commission) Ms. Heidell asks about the Woods Hole Model and increased precipitation. She says this is a vulnerable area, and the building will be there for a while.

(Todd Undzis) Mr. Undzis says he hasn't looked at the Wood's Hole model.

(Susan Chapnick) Ms. Chapnick asks Mr. Undzis if he has comments about the area chosen for flood storage.

(Todd Undzis) Mr. Undzis agrees with the location. It's upland, provides suitable volume, and the vegetation can be improved.

(John Hession) Mr. Hession says they've demonstrated that 2:1 volumes can be achieved. The storage area could be moved to a different part of the site; that might require work in AURAs or the 25' no disturb zone. The proposed storage area is hydraulically connected to the flood plan. He suggests a site walk with a GPS to assess other locations.

(Susan Chapnick) Ms. Chapnick thinks a site walk would be a great idea.

Floodplain Restoration.

(Susan Chapnick) Ms. Chapnick says the commission expects the area to be improved and restored with native vegetation.

(John Hession) Mr. Hession says the landscape plan includes wetland species and native trees. He understands the vegetation mitigation requirements and will work with the commission on that plan. They can include habitat restoration as part of that effort.

(Susan Chapnick) Ms. Chapnick notes that BETA didn't take soil samples, but the commission has observed standing water in portions of the site, and would like test pit data.

(Nathaniel Stevens) Mr. Stevens was unclear as to whether the site had been treated as a disturbed site for the purpose of wetlands delineation, and if the proper methodology had been followed.

(Julia Stearns) Ms. Stearns believes these are low depression areas which don't hold water long enough to form IVWs. She says they can go back and look at the soil.

(Nathaniel Stevens) Mr. Stevens says that BSC identified wetlands in this area 20 years ago, and urges another look.

(John Hession) Mr. Hession says BSC did a peer review study 20 years ago. He says that wetlands can move, and conditions may have changed over the last two decades. BSC will have to respond to that question.


(Susan Chapnick) Ms. Chapnick recommends looking at the NOAA+ precipitation estimates and removal of 90% TSS (Total Suspended Solids). She agrees on the need to verify groundwater elevation.

(Pam Heidell) Ms. Heidell asks how one would determine the high groundwater level in December, and if they way they built infiltration basins would make a big difference in the site layout.

(John Hession) Mr. Hession says that BSC did test pits in the infiltration area just before Thanksgiving. Regarding the time of year question, they'd look for evidence of high water marks in the test pits. Preliminary work was based on a set of 2015 test pits and confirmed by more recent studies. The soil is more pervious than they originally suspected. He's confident that with updated information and BETA's review, they'll be able to meet DEP stormwater regulations. He says the baseline is to meet regulations. They'll consider higher TSS removal if that can be done without making the project uneconomic. He says there seem to be a lot of requests to go well beyond current standards and regulations. He's hesitant to commit to meeting standards which regulatory bodies have not adopted.

(Pam Heidell) Ms. Heidell says the state has signaled its intent to adopt NOAA+. She suggests that one has to design to standards that people feel comfortable with.

(Susan Chapnick) Ms. Chapnick says that ZBA Comprehensive Permit regulations mention climate change as a consideration. She believes it's appropriate to consider MS-4 and higher precipitation rates that Mass DEP is moving towards. She says that small tweaks to their design might allow them to meet the higher standards.

(Stephanie Kiefer, Attorney for Arlington Land Realty) Ms. Kiefer says they've been designing to existing standards, but can consider newer ones. She says there's a tension, but a baseline needs to exist.

Wildlife and Habitat.

(Susan Chapnick) Ms. Chapnick says that BSC's report is complete and supplemented by survey notes. She understands that BETA concurred with their findings. She's concerned about the number and type of trees impacted. Local regulations have specific requirements for tree placement.

Conservation Restriction.

(Susan Chapnick) Ms. Chapnick would recommend a conservation stewardship for land not developed. She'd also like to see a proposal for a conservation easement.

(John Hession) Mr. Hession asks if the commission has any specific questions about the site plan.

(Chuck Tirone, Conservation Commission) Mr. Tirone has a question about the parking area (on the left side of the site plan). An abutter said the parking area was close to his house. He asks why it wasn't changed.

(John Hession) Mr. Hession says they've increased the setback in that area and added screening. They've also looked at the grading to make sure that water doesn't run onto the abutter's property. He says the number of parking spaces they're providing is the number required under zoning.

(Chuck Tirone) Mr. Tirone asks about lights spilling on to the abutter's property.

(John Hession) Mr. Hession says the lighting design will have to take that into consideration. He believes that they are meeting the zoning setbacks required for the parking spaces.

(Chuck Tirone) Mr. Tirone asks if they'll be able to build the driveway entrance over a sewer easement.

(John Hession) Mr. Hession says yes, and they'll have to protect that sewer line during construction.

(Chuck Tirone) Mr. Tirone asks a question about stormwater and driveway grading.

(John Hession) Mr. Hession says the driveway is a structural ramp with a trench drain at the bottom. They're still nailing down the size of the trench and discharge area.

(Chuck Tirone) Mr. Tirone says the conservation would like to join BSC and BETA when they go out to look for isolated vegetated wetlands.

(Mike Gildesgame, Conservation Commission) Mr. Gildesgame asked if they'd calculated the water runoff from the roof.

(John Hession) Mr. Hession says they've done worst case modeling, but haven't done the calculations for routing the water through outlet structures. He talks through several options for discharge areas.

There are no further questions from the commission, and the chair opens public comment.

(Nancy) Nancy would like to walk through the site, but found the Dorothy street perimeter a bit of a tangle. She asks how she can get through.

(Stephanie Kiefer) Ms. Kiefer states that this is private property, and that there's a homeless encampment on the site. She can discuss Nancy's request with the property owner and report back to the ZBA.

(Susan Chapnick) Ms. Chapnick thinks it would be nice to schedule a site walk at some point.

(Stephanie Kiefer) Ms. Kiefer points out that we're in a pandemic, and have to be concerned with COVID. We don't want to create a health hazard by bringing a group of people together.

(Brian Rehrig) Mr. Rehrig says the discussion about future risks was good, but there wasn't much discussion about current conditions. A lot of residents think the actual flood elevation is higher than FEMAs. He urges further investigation.

(Chris V) Ms. V says she just learned about the project. She's wondering if all parties can provide to her, in writing, a list of projects that are exactly the same, and show that they were completely successful in protecting the environment. She would like to see three examples. Ms. V says she's looked at the plans, and believes that 50% of the wetlands will be gone. She says this is a total desecration of nature, and completely opposes it.

(Susan Chapnick) Ms. Chapnick says the conservation commission has worked on a number of projects, and that no two large projects are exactly the same. Ms. Chapnick says that the Symmes redevelopment was a large project with a conservation area.

(Chris V) Ms. V says that Symmes was on a hill, and it's not the same thing.

(Nathaniel Stevens) Mr. Stevens says that he'll speak with Emily Sullivan and attempt to put together a project list for Ms. V.

(Christian Klein, ZBA Chair) Mr. Klein thanks the commission for hosting this working session. The ZBA appreciates getting the benefit of their knowledge.