Town of Carlisle
MASSACHUSETTS 01741
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Office of
PLANNING BOARD
66 Westford Street
Carlisle, Massachusetts 01741
Tel. (978) 369-9702
Fax (978) 369-4521
Minutes
Special Meeting
January 2, 2008
FY09 Budget Guidelines
Presentation on LID techniques – Sandra Brock, PE Nitsch Engineering
Presentation on proposed draft Sewage Disposal System Regulations – Jeffrey Brem, Chair, Carlisle Board of Health
Livable Carlisle Community – David Freedman
Chair Michael Epstein called the meeting to order at 7:40 pm in the Clark Room of Town Hall. Members Greg Peterson, Kent Gonzales, Ken Hoffman, Brian Larson, Marc Lamere, Carol Nathan, Associate Members Tom Lane and David Freedman, and Planning Administrator George Mansfield were present.
Gretchen Caywood, assistant to the Planning Administrator, Ed Rolfe (Maple Street), Sylvia Willard (Conservation Administrator), Jeffrey Brem (BOH Chair), Sandy Brock (Nitsch Engineering)and Bob Zielinski (Carlisle Mosquito) were also in attendance.
Budget
Chair Epstein reviewed the proposed changes to the FY09 budget that were forwarded by FinComm. The proposal involves an approximately 75% cut to the Planning and Professional budget line item, which enables the PB to fund the use of outside experts when necessary. He added that He had met with the Town Administrator and the FinComm Chair to discuss the budget, then subsequently with Planning Administrator Mansfield and with Larson (PB Treasurer). Chair Epstein, Larson, Freedman and Mansfield will assemble detailed information to support the retention of as much of the current budget as possible.
Presentation on LID techniques – Sandra Brock, PE Nitsch Engineering
Brock presented an introductory seminar on low impact design (LID), explaining that her firm had performed LID design work for developers for several university sites. One of the main tenets of LID site design is to identify the important natural features at a site, placing the buildings and roadways in areas less sensitive to disturbance, and to design a stormwater management system that ‘bridges’ the development and the natural hydrology of the site. The goal for managing stormwater is to mimic nature as much as possible. Brock referred to the Mass DEP’s new stormwater regulation changes which are now available on the internet. Ideally, when designing a site, home locations should first be chosen for minimal environmental impact, and then streets, trails are sited, followed by
drawing lot lines. Therefore, it is not possible to integrate the full LID concept into 2-acre zoning requirements. LID can be effectively incorporated into larger sites.
She indicated that while LID is more environmentally sound, overall it is also a more economically sustainable approach to addressing the adverse effects of urbanization. Since under LID techniques runoff is managed close to its source, LID enhances the local environment and can save money for the developer and the local government by avoiding building extensive infrastructure to redirect runoff. LID emphasizes controlling or at least minimizing the changes to the local hydrology, and therefore it can better protect water sources, public health and natural habitat. LID does not address the extreme one hundred year storm, but addresses all the frequent storms. This has the cumulative effect of lessening the need to design for high storm requirements since the low and moderate flow of stormwater has
been handled properly, infiltrating consistently all along.
Brock noted that when LID is used, landscape architects often lead the project, and hire the engineers. This is because the design of LID appropriate bioretention areas and other site components designed to mimic natural hydrology should be done by landscape architects. While regular maintenance of the bioretention systems is best, even unmaintained, a bioretention area will work better than a conventional system, since it better mimics nature.
Brock pointed out that many private driveways as well as entire sites are being retrofitted using LID principles. She explained that the Town must decide its goals for LID: will it be a required design approach or incentive based? Incentives may involve giving the developer an extra lot for an LID layout. She added that since altering the land alters the water balance, it is even more important for Carlisle to stress an LID approach, as the Town relies entirely on its groundwater for its water supply. She stressed that all Town departments as well as its citizens need to understand and support of the LID approach, as its use affects the issues before all departments (Planning, Conservation, Fire, DPW, etc.) as well as applicants and developers. It is best to get all participants
involved and build consensus early in a project. LID often takes more effort in the design phase, with environmental and economic payback down the line.
Brock suggested a few ways to incorporate LID into PB rules and regulations: make it required on all subdivisions, create an overlay district or make it part of the requirements for a Conservation Cluster, or make it a bylaw that would apply to all development in Town. She added that there are maintenance considerations with LID and an increased need for oversight during the construction phase. Education of developers, contractors and engineers on LID issues is important, as there is still a lack of understanding of the LID concepts.
Freedman suggested that the Town should address, perhaps through bylaw revisions, that clusters are a more environmental approach to design, as 2-acre zoning has the effect of breaking up the ecology. Brock provided the PB with a compilation of information on case studies, best development practices, stormwater management, as well as model bylaws.
Presentation on proposed draft Sewage Disposal System Regulations – Jeffrey Brem, Chair, Carlisle Board of Health
Brem began by providing a review of the structure and function of a conventional septic system, and a review of the evolution of the current Regulations, which were originally adopted in 1983, and revised significantly in 1987 and 1998. The BOH regulations supplement Title 5, which sets minimum requirements for subsurface sewage disposal systems. Brem noted that changes to these local health regulations require a legally noticed public hearing, but do not require Town meeting approval.
The goal in drafting the proposed revisions, a copy of which had been provided to the PB for their review, is to bring the current regulations into compliance with Title 5, to make certain they are based on the most up-to-date science, and to identify the local conditions which justify exceeding the minimum (Title 5) requirements. Several key areas under scrutiny are:
Setbacks to wetlands
Minimum design flow requirements
Review of large systems (greater than 2000 gallons per day)
High groundwater season (revised to 3/15 – 5/15)
Alternative technology
Concerning flow rates, currently every system is being designed based on an assumed generation of 165 gallons of wastewater per day per bedroom. Brem explained that in reality, most homes are not fully occupied based on their bedroom capacity, and that therefore, the gallons per day (GPD) assumption per bedroom should decrease as the number of bedrooms increases. Also, he believes that the requirement of a 50% increase in system capacity for homes of three or more bedrooms that have a garbage grinder is excessive. Therefore, he stated that it is his opinion that current septic systems are being overdesigned in Carlisle. He explained that this can lead to environmental failure of the system because with sporadically insufficient flow rates, the biomat layer (thick fibrous layer that forms at the
interface of the septic trench gravel and the soil) does not form uniformly. This layer contains microorganisms which, with a properly formed layer, assist in filtering and decontaminating the
wastewater. Since the sewage will follow the path of least resistance, with a non-uniform biomat, the water is not being filtered properly. Thus there is failure by improper treatment, but not by breakout, and this is not visibly evident.
Hoffman pointed out that Title 5 is designed for a more urban community, and agreed with Brem that most of the Carlisle homes are underutilized based on bedroom count. Also, when Gonzales mentioned the separation of ‘grey water’ (dehumidifier water, for example) from septic requirements, Brem said that the current and revised regulations encourage it. Brem added that for shared systems and condos, the required septic system capacity will be based on 165 GPD per bedroom.
Brem explained that the new regulations encourage the use of alternative technologies for system upgrades or new construction. These technologies often involve the use of sand filters, trickling filters, aerobic treatment units, and/or additional bioreactors to biologically decontaminate the effluent and to reduce the nitrogen load. Some systems also use an artificial biomat, which insures uniformity. The Presby system uses a corrugated, perforated plastic pipe, with a coarse plastic fiber mat surrounding the pipe, and a non-woven plastic layer containing the entirety. Effluent passes to the non-woven plastic layer, and grows a protective bacterial surface. The fabric and fibers provide a large bacterial surface to break down solids. Brem added that the state is encouraging use of these
alternative systems, and noted that many of the technologies are less expensive overall.
Concerning setbacks, Brem noted that the BOH is not changing its requirement of a minimum setback distance of 100 feet between a leaching area and wetlands, but noted that historically, the Board has granted waivers for repairs on old systems if it finds an environmental benefit. The Board does not grant waivers for new construction. For placement in a buffer zone (from 50-100 feet from a wetland), which may be allowed by waiver under certain rare circumstances, the Board may require the use of alternative technologies. Brem noted that they will address each case with Conditions and Findings for each lot.
With regard to the Hanover Hill, Brem expressed that there needs to be sufficient bioretention and percolation time of runoff, particularly uphill of a septic system, or the system will not work properly. He noted that two proposed lots at the site have infiltration systems uphill of their septic systems. Brem referred to a recent memo to the PB from the BOH that refers to a potential change in location of the septic system for Lot 4, and asked the PB to address this in their review. This illustrates the importance of the Boards and Commissions working together for best site design. Chair Epstein invited Brem to attend the PB meeting on January 14th, at which there will be an extensive hearing on this application.
Brem noted that the goal is to hold a hearing on the revised regulations in February. Draft regulations will be provided to the PB for their review. Chair Epstein set a time of 9:30 at the January 14th meeting for review and discussion of these draft regulations.
Livable Carlisle Community (LCC)
Freedman spoke briefly on this issue, reporting on recent meetings of the steering committee for this group of citizens and members of Town government. The BOS has endorsed their efforts, the goal of which is to assure that the Town government, volunteer groups and religious organizations work together to help address present and anticipated issues for Carlisle. Freedman invited the PB to take part in spring meetings of the LCC.
Respectfully Submitted,
Gretchen Caywood
Administrative Assistant
Carlisle Planning Board
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