22B-113 Phase 2 2012 Berkshire Wetland Permit Comments.pdf
January 5, 2012 Sarah LaValley, Conservation, Preservation and Land Use Planner Office of Planning and Development 210 Main Street, Room 11 Northampton MA, 01060 RE: Berkshire Design’s
response to staff and DEP comments: Florence Recreation Fields Dear Sarah, Carlos Nieto-Mattei of Berkshire Design and Bruce Griffin of New England Environmental have submitted their
responses to both DEP and staff comments, as follows: DEP Comments (in order based on their review comments) 1. N/A 2. Clarifies to the Con Com to review table 4 to determine compliance
with flood calculations. No response required. (Mark Darnold had a long conversation with DEP to clarify any concerns on the methodology). 3. The report of June 10, 2011 contained an
editing error in discussing the extent of Bordering Land Subject to Flooding. As pointed out in the DEP letter the correct source is the local FEMA Flood Insurance Study. This is correctly
depicted and cited on the plan. 4. MAHW was generally flagged at the first observable break in slope. For much of the stretch of Mill River assessed, this was a very clear-cut, steep
slope breaking to nearly level. This reach of river did not have the characteristics associated with reaches where bankfull field indicators are located above the first break in slope,
as cited in 310 CMR 10.58(2)(a)2.b. 5. First part of the comment re-iterates the information about storm water structures that we explained in the Additional information for 10.58 Riverfront
Area Compliance Standards. Storm water measures may only be exempt if the alternative analysis shows that the work proposed is the only practicable alternative. We believe that the alternate
analysis shows that the proposed overflow outfall is the only practicable alternative. We believe that reducing the scope of the project would not be a practicable alternative because
it would go against the proposed use for multi use sports fields, also even if smaller in scope, we would still need to solve the same drainage issue as with the proposed concept, being
being that the natural drainage on the site has been interrupted by the farmers accumulating rocks and soil on the edge of the fields next to the mill river. The only practicable way
to drain the site is to breach this barrier, to restore natural flows. The second part of number 5 talks about the alternative of approaching the project as re-development to avoid the
alternative analysis. To allow redevelopment the site has to have been previously degraded. The area to be altered does not fit within DEP’s definition of degraded, the only area that
is
borderline is the farm road access, but the small amount of degraded area that comprises the road, would be too small to allow for the square footage of alterations that is proposed.
We would need to do alternative analysis for the rest of the area not covered by re-development. 6. This comment is in regard to the Grow Food Northampton parcel and the proposed work.
DEP is correct in asking for the signature of Grow food Northampton for the NOI permit, it will also require a maintenance easement to be compliant with storm water standard 9 and 10.
I know that we have informal permission to do the work, but we need written authorization and a signature for the NOI. 7. DEP would like to see storm water BMP’s be set as far away from
the BVW. In this case it is impossible to place it any farther because the work being done is to re-establish the natural drainage flow, which goes into the Mill River and its associated
wetlands. To re establish the natural flow the accumulated farm material at the edge of the river, that forms a virtual dam, will have to be removed all the way to the edge of the BVW.
The second part of the comment questions the placement of the BMP within the 10 year flood plain. First, the infiltration swale is for the most part outside of the 10 year flood plain.
The overflow of the BMP is located within the ten year flood plain, but no the BMP itself. Second, DEP suggests removing BMP’s from the 10 year flood plain. We don’t see any detrimental
effects in having the BMP within the 10 year flood area. The 10 Year flood event and designing a BMP for a ten year storm are two different things. The BMP is design for the 10 year
storm. In a 10 year rain event, the BMP will slow down peak flows to prevent erosion and pollutants to reach the resource area. This will control and slow down water runoff at its most
intense moment (peak flow), during intense rain. The 10 year flood plain will flood at a much slower rate, by the point the river hits flood elevation, peak flows have subsided. The
effect of flood flood water on the land is different than peak flows, the flood rises up slowly, and its effects are not erosion and contaminated runoff, but settlement of sediments
over a large area. The Mill River generally reaches floods level 12 to 24 hours after the storm event when the whole watershed has drained its runoff water into the river. 8. More infiltration
has not been proposed because of the very shallow ground water on the site, especially on the low areas where water naturally drains. 9. Rain gardens could not be used because of DEP’s
standard requiring separation of the bottom of the rain garden and ground water. As previously stated, we have high ground water throughout the site, in particular the lower areas where
water naturally drains and where drainage structure had the least amount of impact. The armored drainage overflow will be constructed with an open grid segmental concrete block that
will allow for re-vegetation and naturalization of the area. 10. The areal extent of work in BLSF is 982,782.37 SF Response to January 3, 2011 Staff Comments (numbering based on original
letter) 1. We will wait for response from NHESP. From the Mesa Request form we know the species of concern is Boyeria grafiana Dragonfly. Several management measures have been included
on the plans that take into consideration the occurrence of this dragonfly. a. From previous experience with dragonfly habitat, one of the main concerns for management is maintaining
a cool water source. The plan addresses this with the use articulated concrete armoring (detail and images attached), instead of the usual riprap for the bottom of the shallow overflow
swale. Because the armoring consists of concrete pavers with large void spaces, the pavers themselves have a light color and allow vegetation to grow through it. This helps maintain
cooler surface temperature. b. Erosion is another concern with dragonflies, as they need clear water for their habitat. The plan addresses this concern by providing a very shallow slope
for the overflow swale in in addition to armoring its bottom and re-vegetating the area.
c. Last, the area will be seeded with a native wildlife conservation mix. Most of the area where work is proposed has no existing vegetation because of it former agricultural use. 2.
The project will meet the Northampton Wetlands Ordinance performance standards: a. Standard 337-10 E.(1)(a) – The proposed work within the 9,096 sf area between 100 ft and 50 ft of the
BVW will not affect wetland values. The area in question lacks any vegetation because of its agricultural use. The plan proposes the re-vegetation of the area with a native wildlife
conservation mix, improving it from current conditions. In addition the proposed work will re establish the natural drainage pattern of the project site and agricultural fields to the
north of the proposed project. The agricultural activities, in particular from the last several years of potato farming have accumulated a significant amount of top soil and rocks to
the west of the Mill River and associated wetlands. This has resulted in virtual dam that at present conditions prevents water from reaching the banks of the river. On storm events,
water accumulates along the farm road to the east of the project and inundates parts of the proposed project site and north, toward the remaining agricultural fields. Water keeps accumulating
until it overflows into Meadow Street, flowing to the east along the road, bypassing two overtaxed catch basins, and eventually, reaching the river on either side of the bridge, dragging
along contaminants and silt from the fields and causing erosion (see Figure 1-4). The proposed work would allow the drainage overflow of the sport and agricultural fields back into the
flood plain of the river, allowing the riparian zone to serve as filter and re establishing the natural drainage pattern. Two other alternatives were evaluated (see NOI Narrative Description
– Additional information for 10.58 Riverfront Area Compliance for details), and both would represent more alteration of the BVW buffer and to the BVW itself. b. Standard 337-10 E.(2)
– The proposed work within the area 50 ft from the BVW will be exempt because of (d) (e) i. Exception (d) the project will improve the natural capacity of a recourse area to protect
the interest identified in MGL c.131 § 40 by re establishing the natural drainage pattern of the project area and remaining agricultural fields to the north (see description of drainage
pattern in previous paragraph and Project Description). In essence, the shallow drainage overflow, removes the fill that was accumulated by the past agricultural activities that created
an earth and stone dam which prevented the natural drainage pattern of the area. Wild life habitat will be protected during construction by the installation of erosion control barriers
and after the work is finished by the use of concrete pavers with large void spaces to armor the bottom of the overflow swale, to prevent erosion and allow a quick re vegetation of the
area (see comment 1). ii. Exception (e) even though the drainage overflow swale is part of the Florence Fields project, the work will address three significant drainage challenges affecting
the agricultural fields to the north, managed by Grow Food Northampton: 1. The lowest area of GFN fields can be underwater for some time after major storm events, making this area unusable
for agriculture. This drainage improvement will end the annual formation of a lake here and provide GFN with more planting options. 2. The northeast corner of the field above the seasonal
lake often floods during storm events, preventing its use for productive agriculture and backing up water further up gradient. The drainage improvement will allow this land to be productively
used for agriculture. 3. The farm access that will provide key access to the easterly portion of the “main” field is unusable for many farm vehicles for some time after a rain event.
The drainage improvement will provide much better access.
Figure 1 – Flooded farm access road of off Meadow Street in late spring 2011. Figure 2 – Flooded fields along soil “dike”. The Mill River is to the left, beyond the narrow tree edge.
Figure 3 – 4’ to 5’ Soil “dike” along fields. Standing person for scale.
Figure 4 – Field drainage pattern. Larger arrows represent major flow and smaller arrows show drainage pattern. The hatch area along the tree line points out the area of the soil and
rock dike. The area surrounded by the grey line gets flooded in storms and throughout the spring season. In major storms the flood area fills up along the major drainage arrows. It is
clear on this aerial image that the original drainage pattern went into the river (crossed out arrow), but with the soil that was accumulated along the edge of the fields (see Figure
4) the water now backs up, flooding the access and some of the fields, and eventually overflowing into Meadow St. (see Figure 2, 3 & 4). 3. Detail of the overflow swale. The elevations
of the overflow are shown on the submitted plans Sheet L12 Grading Plan. The swale consists of very shallow grading and the armoring of the bottom to prevent erosion. Attached is a typical
section of the armoring. Several images showing examples of its use.
Figure 5 Armoring during installation
Figure 6 After installation, starting to re vegetate. Figure 7 Armor installed for bank stabilization. Partially vegetated.
Figure 8 Armor installed for bank stabilization. Fully vegetated. 4. Yes, the general performance standards for RFA 310 CMR 10.58(4) has been met for all parcels. 5. A full alternative
analysis was established, and all feasible alternatives had greater impact on the resources (see NOI Narrative Description – Additional information for 10.58 Riverfront Area Compliance
for details). One thing to consider is to create a steeper side slope on the overflow swale, even though not the ideal scenario because of its visual and functional impact (easier farm
vehicle access, slower water speed at the overflow, reduced potential erosion, etc), it would reduce the area of the RFA altered by 1/3. 6. The river front area where work is proposed
cannot be considered redevelopment because it does not fit the definition of previously developed area as established by 310 CMR 10.58 (5) “A previously developed riverfront area contains
areas degraded prior to August 7, 1996 by impervious surfaces from existing structures or pavement, absence of topsoil, junkyards, or abandoned dumping grounds”. Thanks for your consideration.
Sincerely, Wayne Feiden, FAICP Director of Planning and Development