Coles Meadow Wetland Replication plan-6-3-19.pdf1
Environmental Planning Associates
Specializing in Land Use & Zoning, Wetland Permitting, Septic System Design
P.O. Box 351 413-665-7903
South Deerfield, MA 01373-0351 (866) 318-2770 (fax)
e-mail: enplan@comcast.net
Wetland Replication Plan
Narrative
Parcel 08-070
Coles Meadow Road
Northampton, MA
(Revised 6/3/19)
The proposed driveway is located adjacent to the north property line. The proposed driveway construction,
combined with the associated limit of work, will disturb 4,406 s.f. of vegetated wetland. The proposed
wetland disturbance is minimized by use of a straight, single lane driveway, located in an area where the
vegetated wetland does not occupy 100% of the driveway path. Wetland fill is also minimized by
mechanized earth stabilization (concrete blocks) on the north and south sides of the driveway. By
eliminating the need for 2:1 earthen side slopes, concrete blocks significantly reduce the amount of wetland
fill.
Narrative description of existing wetland:
The existing wetland is a forested wetland system. Some areas have a greater density of mature trees
than others. The western part of the proposed driveway [WF 1 — WF 5 and WF 32 — WF 35] has the
greatest density of mature trees, and then, moving east, progressively fewer mature trees. There are two
relatively small parts of this wetland where the low density of mature trees allows canopy openings which
receive full sun part of the day. One such area is approximately 400 s.f., located approximately 80 feet
southeast of WF 14. The other is approximately 400 s.f., located 60 feet north of WF 28 — WF 29. This
latter area is the only part of the system where standing water is frequently evident during the growing
season. Standing water at the surface is evident in other locations for a day or two after precipitation
events.
Overall, the plant community indicates acidic to circumneutral soil conditions (Table 1). These plant species
are frequently found in intermittently saturated systems, with few areas of standing water.
Functions of Bordering Vegetated Wetlands:
310 CMR 10.55: Bordering Vegetated Wetlands (Wet Meadows, Marshes, Swamps and Bogs)
(1) Preamble. Bordering Vegetated Wetlands are likely to be significant to
▪ public or private water supply
▪ to ground water supply
▪ to flood control
▪ to storm damage prevention
▪ to prevention of pollution
▪ to the protection of fisheries and to wildlife habitat
Narrative description of proposed wetland replication — Hydrology and Soils
The proposed wetland replication area is adjacent to the existing vegetated wetland. The replication is
designed to serve the same ecologic and hydrologic functions as the existing wetland. This wetland system
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provides five of the six functions of bordering vegetated wetlands listed in the abovereferenced subsection
of the Massachusetts Wetlands Protection Act regulations. The one function which is not present here, is
groundwater recharge, and is not significant to ground water supply. The groundwater recharge function is
absent here because the silt loam in the A soil horizon largely prevents percolation of stormwater into the
highly permeable loamy sand and sand lying just beneath that upper 6 — 10" of silt loam. This condition is
commonly referred to as a "perched water table."
This wetland is located in a topographic depression containing silt loam and silt clay loam soils where storm
water percolates very slowly into the ground. Slow percolation detains water in the upper soil stratum. This
detention helps protect downstream parts of the wetland resource system from pollution and flooding.
Downstream pollution would ultimately damage fisheries and wildlife habitat values of the overall wetland
system.
The proposed wetland replication area is 4,406 s.f., located east of Coles Meadow Road. As with the
wetland adjacent to it, the replication area is semi-forested, and consists of Ridgebury soils (ReB). The
Ridgebury soil class is characterized by a dense silt loam layer in the upper horizon. The NRCS Soil
Survey describes Ridgebury soil as including the following characteristic:
• Depth to restrictive feature: 10 to 25 inches to densic material
Soil borings in the area show that the densic material encountered ranges between silt loams and silt clay
loams. Both are very poorly drained. Across the landscape of this lot, some parts of this Ridgebury soil
deposit contain upland conditions, and other parts exhibit hydric soil conditions. Stones and cobbles are not
unusual in Ridgebury soil deposits. In the western 100 feet, nearest to the road, the soil substratum
consists of a dense silt loam from a depth ranging from 2" to at least 20". Deeper than 6" in the profile, the
silt clay loam becomes progressively more compact. Underlying the silt loam, is a highly permeable loamy
sand. The typical soil profile of the replication area is depicted in Cross Section detail C — C'. The coarse
grained loamy sands are also typical of the upland areas at the eastern section of the lot. Soil borings
conducted on October 2, 2018 showed that further east of the road, between WF 14 and WF 22 the dense
substratum is vertically 5 feet thick, underlain by loamy sand.
Both the wetland and the proposed replication area are situated in a relatively flat area, where the slope
ranges between 1.4% and 2.1%.
Hand augured soil borings were conducted in the replication area. Soils consist of less than 2" depth of
organic O horizon material, then followed by 15 – 20" of silt clay loam, then underlain by highly porous
loamy sand.
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Augur Hole 5R Date: 5/3/19
Depth Horizon Color Texture Mottling Other
No appreciable organic layer
0 — 15" A 10YR/3/2 silt loam Ø
15" — 17" AB 10YR/3/2 silt loam 5YR/5/8
(high chroma
mottles)
17" — 22" + C 10YR/4/3 sandy loam 5YR/5/8 high
chroma mottles
transition from silt
loam to sandy loam
Augur Hole 6R Date: 5/3/19
Depth Horizon Color Texture Mottling Other
1.5" — 0" O 10YR/2/2 sandy loam Ø
0 — 18" A 10YR/4/4 silt loam 5YR/5/8
(high chroma
mottles)
low chroma
concretions @ 16"
The silt loam soil layer creates a perched water table condition. This is critical to the water detention
provided at this part of the wetland system. In the absence of an adequate silt loam confining soil layer,
stormwater would rapidly percolate into the ground and will not be retained at the surface. The absence of
silt loam in the upper soil horizon is typical of the eastern part of the lot, where the house and septic system
would be situated. And that area is a very dry forest, also lacking the diversity of herbaceous plants found
within the wetland.
Failure to maintain a horizontally uniform silt loam confining soil layer in the replication area, would mean
that water would likely not be detained near the surface. The preservation and enhancement of the silt clay
loam soil layer is the critical factor for surface retention of accumulated precipitation and runoff. Any attempt
to retain existing trees in the replication area, and to disturb the soil around the tree root system could
introduce vertical perforations in this soil layer. This could disrupt the perching effects caused by the dense
silt loam soil in the upper soil horizon. Vertical perforations would allow water to drain into the underlying
loamy sand. This could then reduce the capacity of the replication area to retain surface water.
Consequently, saturation periods would be brief, or non-existent. The MA DEP Wetland Replication
guidance advises retention of mature trees when the trees are facultative or wetter. 14 of the 21 trees in the
replication area are upland species (Table 3). The DEP Guidance contemplates tree retention specifically
with reference to pit and mound wetlands. While there are a few instances of trees hummocked up, overall
this is not a "pit and mound" wetland.
The mature trees in the replication area significantly contribute to it being an upland. Each Eastern hemlock
tree removes 50-80 gallons of water from the system per day. (Arboriculture & Urban Forestry 33(6):
November 2007, Page 423, Figure 3) Removal of trees from the replication area is necessary for two
reasons:
▪ to reduce the amount of water that would otherwise be removed from that area via
evapotranspiration;
▪ to assure that a sufficient depth of relatively impermeable silt loam is established uniformly across
the replication area; Any attempt to cut around roots of existing trees will likely result in sporadic
and uneven deposition of silt loam as a confining layer. In any event, significant disturbance of the
root systems is likely to cause the premature demise of the trees.
In this case, retention of mature trees would undermine the success of the wetland replication. Mature trees
are removing water from the ground via evapotranspiration. The replacement of the mature trees with
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herbaceous plants and woody saplings will reduce the evapotranspiration rate, and facilitate water retention
within the upper soil stratum. Soil saturation slows down the process of leaf litter decay. The slow organic
decay elevates the organic content within the upper soil stratum. Soil with higher organic content retains
more water and for longer duration, than mineral soil. The accumulation of organic matter within the soil
profile is the key feature of any vegetated wetland. The organic matter sequesters pollutants.
The terrain generally directs runoff flow from east and northeast toward the low point in the northwest
corner of the property. The existing culvert was placed in the existing swale fed via this low topographic
area. The proposed replication area is adjacent to this low point. The replication area is a little bit higher
than the adjacent wetland.
The grade in the replication area will be lowered by one foot. This will allow saturated conditions within 3
inches of the surface. Saturation will be caused by a combination of:
• runoff from the surrounding higher terrain
• groundwater level fluctuations
• the relatively impermeable silt clay loam already in place
• removal of trees which are evapotranspiring water out of the system
Open water is not persistently present anywhere within 100 feet of the proposed replication area. Within
the wetland, soil moisture is prevalent at or near the surface during and after sustained rain events. In the
replication area, soil borings showed standing water at depths ranging between 18" and 22". Silt clay
loams were saturated at depths as shallow as 15" in the Fall and Winter. High chroma mottling, an
indicator of intermittent and/or partial saturation, is also present as high as 15". With the exception of
prolonged dry spells, the standing water was typically observed at a depth of 22 — 24" in the proposed
replication area. During prolonged rain events, water ponding was observed at the surface in parts of the
adjacent wetland. The silt clay loam becomes progressively more dense and compact with depth.
Removal of the upper 12— 18" will create conditions where the more dense silt loam would be closer to the
surface. To the extent that excavation encounters the very permeable loamy sand higher than 17" in the
soil profile, the loamy sand can be removed and replaced with silt loam recovered elsewhere within the
replication area, when the upper 12 — 18" is excavated. The overall intent is to create a uniform and
predictable perched surface water condition.
Vegetation
The wetland system as a whole, is populated with facultative plants, which can survive in less saturated
wetlands, as well as in uplands. Most of this wetland system does not contain significant communities of
obligate wetland plants. The vegetation in the wetland disturbance area indicates that it is more acidic than
alkaline.
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Table 1
Inventory of Existing Plant Species
Proposed Wetland Disturbance Area
Common Name Scientific Name Wetland Indicator Status Habit/pH range
Sensitive Fern Onoclea sensibilis FACW 5.0 — 7.0
Sweet Birch Betula lenta FACU 4.0 — 6.8
Green Ash Fraxinus pennsylvanica FACW 6.1— 7.5
Red Oak Quercus rubra FACU-
usually acidic; can tolerate slightly
alkaline environments
Eastern Hemlock Tsuga canadensis FACU 5.0 — 6.5
Poison Ivy Toxicodendron radicans FAC
Sweet Birch Betula lenta FACU < 6.8
Virginia Creeper Parthenocissus
quinquefolia
FACU 5.1 — 7.5
Red Maple Acer rubrum FAC usually acidic; can tolerate slightly
alkaline environments
Spotted Touch Me
Not
Impatiens capensis FACW 5.6 — 6.5
Northern Arrowood Viburnum recognitum FACW- 5.1 — 6.5
Clinton's Woodfern Dryopteris clintoniana FACW+ < 6.8
Mousntain laurel Kalmia latifolia FACU 5.0 — 7.0
Jumpseed Persicaria virginiana NI 4.4 — 6.6
Table 2
Inventory of mature trees within proposed driveway area
(reported in inches in diameter at breast height "dbh") (Reporting only specimens at least 5" dbh)
Red
Maple
Eastern Hemlock* Oak Shagbark
Hickory
Green Ash
8" many of the
hemlocks in this part
of the property are
dead or in severely
compromised health
14" 10"
8" 6" 18" 18"
12" 20" 18"
12" 20" 20"
14" 20"
16" 22"
16" & 16"
coppis
24"
16" 26"
24"
28"
Subtotal of Tree
Species
10 1 8 4 0
Total Mature
Trees
23
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The proposed wetland replication area also contains the plant species found in the wetland area, as well as
White oak, Red Oak, Shagbark Hickory, Dogwood, Christmas fern, and Painted trillium. There are also
numerous mature trees standing in the wetland area which are dead or in an advanced state of decline.
Table 3 contains an inventory of the healthy mature trees in the proposed replication area.
Table 3
Inventory of mature trees within wetland replication area
(reported in inches in diameter at breast height "dbh")
(Reporting only specimens at least 5" dbh)
Red
Maple
(FAC)
Eastern Hemlock*
(FACU)
Red Oak
(FACU-)
Shagbark
Hickory
(FACU-)
Green Ash
(FACW)
8" many of the hemlocks in this
part of the property are dead
or in severely compromised
health
10" 12" 10"
9" &
10"
coppis 4"
22" 15"
10" 6"
22" &
10"
coppis
10" 8"
12" 8"
15" 8"
8"
10"
10"
15"
Subtotal of
Tree Species
6 9 3 2 1
Total Mature
Trees 21
Replication Construction Sequence
The proposed replication site is between Wetland Flags 4 through 8. The replication area will be staked out
on the ground by Environmental Planning Associates prior to the commencement of work. All mature trees,
saplings and stumps in the replication area will be cut and removed from the property. The meager depth
of organic topsoil makes any effort to remove and stockpile it separately from the A horizon silt clay loam,
futile.
1. Remove and stockpile 12 inches of A horizon soil, separately stockpile any sandy loam
encountered from silt loam and silt clay loam present in the A Horizon.
2. Cover soil stockpiles with straw to facilitate moisture retention
3. Call Environmental Planning Associates to evaluate and survey elevations of the new finished
grade
4. Identify any areas where the silt clay loam left in place is less than 6" deep;
5. Use stockpiled silt clay loam as needed to establish uniform depth of this impermeable material
across replication area
6. Use 24" wide hand roller across the entire replication area to increase soil compaction
7. Hand rake upper 2" of finished grade
8. Spread 1 — 2" depth of imported topsoil (free of stones and gravel)
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9. Spread 6 — 8 pounds of specified seed over replication area
10. Hand rake to work seed mix into soil
11. Plant 18 + specimens of Silky dogwood (Cornus amomum) along northern edge of replication area,
in accordance with plan view and detail
12. Cover the entire replication area with straw
Replication Planting Plan
This planting schedule is available locally (New England Wetland Plants, Amherst, MA) as a seed mix
called " New England Wetmix (Wetland Seed Mix). This replication site is subject to intermittent, storm
related inundation. The mix of herbaceous wetland plant species is specified for this rainfall pattern.
On this 4,406 s.f. replication site, 6 lbs. of seed mix should be more than adequate. Chemical fertilizers
inhibit seed germination and will not be used.
Additionally, 18 specimens of the woody shrub Silky dogwood (Cornus amomum) (FACW) will be planted
along the northern edge of the replication area.
The proposed replication work would be from a point 21 feet north of WF 4, extending 115 feet southeast to
WF 8.
Replication Construction Monitoring
• Pre-construction meeting on site with contractor and Environmental Planning Associates to review
replication area layout, construction sequence, and to verify silt fence installation;
• Environmental Planning Associates to notify Conservation Commission;
• Inspections at preparation of subgrade, and after placement of wetland seed mix, and every 3
weeks through remainder of the growing season;
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