Functional Analysis of Hydrology of Barrett Street Marsh 2000Functional Analysis
of the
Hydrology and Hydraulics
Barrett Street Marsh
Barrett Street Marsh, looking west
Prepared for
The City of Northampton
Office of Planning and Development
City Hall
Prepared by
Baystate Environmental Consultants, Inc.
296 North Main Street
East Longmeadow, Massachusetts
April, 2000
1.0 INTRODUCTION
On December 30, 1999, the City of Northampton's Office of Planning and Development selected
Baystate Environmental Consultants, Inc. (BEC) to conduct an analysis of the Barrett Street
Marsh Conservation Area, in response to concerns over the marsh's current condition and future
development relative to flood elevations. Recurring drainage issues in the form of increased
flooding, rising groundwater levels, and higher marsh (surface) water levels have garnered the
community's concern and have prompted city officials to develop a plan of action to ensure a
harmonious relationship between the Barrett Street Marsh and its developed surroundings. The
scope of this analysis was to include an overview of the historic and current hydrology of the
marsh and its watershed. Specific scope items from the November, 1999, Request for Proposals
include the following items:
Analysis of the marsh's hydrology
Determination of areas of harmful sedimentation
Determination of the rate of succession occurring in the marsh (natural and acceler-
ated)
Analysis of what opportunities there are to reduce the sediment load entering the
marsh
Analysis of what steps are necessary to bring the water levels within the marsh to sus-
tainable levels which will have minimum impact on upland abutting properties or on
culverts entering the marsh.
An analysis, given existing conditions of whether the water quality and water quantity
functions of the Carlon Drive detention basin meet current discharge requirements and
standards.
The Barrett Street Marsh is a 22±acre parcel owned by the City of Northampton and is located
west of King Street, between the rail trail embankment to the south and Barrett Street to the north
(Figure 1). The marsh has been significantly altered and manipulated over the last 150 years,
most recently evolving from agricultural fields to an emergent marsh. Its environs have grown
incrementally over the last several decades and now tightly encircle the marsh with a mix of
residential, commercial, and light industrial uses. Although valued for its habitat and conserva-
tion attributes, the wetland is increasingly at odds with the infrastructure needs of the surround-
ing constructed environment.
In a related issue, the detention basin constructed in 1997 at the Carlon Drive industrial subdivi-
sion has also been examined relative to the plans and designs approved by the Northampton
Planning Board and Conservation Commission. It has been perceived that rising water levels
within the adjacent Barrett Street Marsh have had a negative effect on the basin's usefulness as a
stormwater management tool. An analysis of the existing detention basin relative to current dis-
charge requirements and standards is made.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
lageLof35
VOttrts*strAhthttrAttrh 74'
err
Civil Engineers
196 North Nen Street
BAYSTATE ENVIRONMENTAL
CONSULTANTS INC.
Environmental Scienlists
East longmaaaon, 18 01018
SITE LOCUS
April 20, 1971
Scale: 1" 1000
Figure 1
In support of the analysis, BEC personnel conducted numerous field investigations and reviewed
the extensive records of the City of Northampton's Department of Public Works and Office of
Planning and Development. The entire King Street Brook channel was walked under flowing
conditions and again when partially frozen. Sediment samples were obtained from within the
King Street Brook channel and were analyzed for in situ density, total solids, and organic con-
tent. Elevational surveys of the brook and the Carlon Drive detention basin were performed to
better ascertain current conditions. With regard to potential capital improvements to maintain
and manage the marsh, various technologies and methods were investigated and discussed with
industry representatives and agencies.
The remainder of this report will present the following analyses:
Historical Considerations
Marsh Hydrology and Successional Stage
Biological Factors Potentially Affecting Marsh Hydrology
The Effects of Stream Channel Diversion on the Marsh Hydraulic Functions
Analysis of the Accumulated Sediments and Sediment Loading Analysis
Carlon Drive Detention Basin Functional Evaluation
Potential Corrective Actions and Recommended Measures.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 3 of 35
2.0 HISTORICAL CONSIDERATIONS
The history of the Barrett Street Marsh is well documented and shows that the entire area has
been highly altered since the early 1800s, when transportation corridors began to be established
nearby and development spread northward from the center of Northampton. The area now
known as the Barrett Street Marsh was originally part of a much larger wetland system that ex-
tended to the east, having been severed from the larger system by development. Reportedly, the
Barrett Street Marsh was used as agricultural land from the early 19 century, having been de-
watered by a system of drainage ditches that were dug throughout the low -lying area.
The main flowage into the marsh is a perennial stream known as King Street Brook that consists
of drainage from the Round Hill/Prospect Street area. The brook enters the southern-most point
of the marsh, through a culvert under the bike trail that runs along an abandoned railroad em-
bankment. Until the early 1900s, King Street Brook did not flow into the Barrett Street Marsh
but instead flowed in a more southeasterly direction towards State Street and the center of North-
ampton. As recorded at the Hampshire County Registry of Deeds (Book 596, Page 375), in 1905
the Northampton Sewer Commissioners voted to divert the flow of King Street Brook away from
"the mouth of the State Street sewer for the purposes of `public health and convenience". The
brook was to be diverted to the "center of an old ditch" which then existed northeast of the rail-
road embankment and presumably ran through what is now known as the Barrett Street Marsh.
The City proceeded with the taking of a strip of land almost 1,800 feet long and 15 to 25 feet in
width to encompass the old ditch and hence the brook along its diverted course to the Connecti-
cut River. The ditch was thereafter known as the King Street Brook Diversion. Also in 1905,
the City was granted an easement from the New York, New Haven, and Hartford Railroad Com-
pany to construct "a box culvert four feet deep by four feet wide suitable for carrying through
the waters now running in King Street Brook, so- called" (HCRD, Bk 597, pg 202), which is the
now existing culvert under the bike trail.
The character of the King Street Brook Diversion was thus established almost one hundred years
ago. The configuration of the ditches within the Barrett Street Marsh at the time of the diversion
is not known. Anecdotal information indicates that the marsh area was used for agricultural pur-
poses into at least the 1970s. Aerial photographs from the 1960s and `70s clearly show the on-
going agricultural use and the diversion channel in its original (1905) location with a geometric
array of ditches leading to the diversion from many areas of the marsh. In a photograph taken on
April 20, 1971 (Figure 2), the water within the diversion appears to be 8 -10 feet in width, and the
most upgradient half of the diversion channel within Barrett Street Marsh appears to have been
recently maintained prior to the photograph being taken.
Coincident with the advent of restrictive environmental regulations and changing attitudes re-
garding the value of wetland areas, maintenance of the diversion channel and system of ditches
waned in the 1970s, and use of the land for agriculture altogether ceased over twenty years ago.
The date of the last maintenance dredging of the King Street Brook Diversion is not known.
While records of ditch construction and effectiveness are not available, considerable evolution of
the marsh's hydrology has taken place in the recent past since the ditches were last maintained.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 4of35
ri
ft
Civil Engineers
296 North Nain Street
BAYSTATE ENVIRONMENTAL
CONSULTANTS INC.
Environmental Scientists
East Longmeadow, WA 01028
April 20, 1971
Scale: 1" 200'±
Barrett Street Marsh
Figure 2
r
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L
3.0 MARSH HYDROLOGY AND SUCCESSIONAL STAGE
The watershed draining to the Barrett Street Marsh consists of approximately 290 acres of land
that is primarily residential in use. Portions of the watershed are steep and densely developed,
and most areas drain to the wetland through stormwater collection and conveyance (i.e. drainage)
systems installed and maintained by the City of Northampton. The main inflow to the area is
King Street Brook, diverted to flow through the marsh in 1905. Numerous other minor inlets to
the marsh convey runoff and drainage from the immediately adjacent land uses. Continued de-
velopment within the watershed within the last 200 years has created a significant percentage of
impervious surface contributing storm water runoff to the marsh. In general, the drainage infra-
structure is 50 -100 years old and has undergone few major changes in the recent past. Storm
drainage from the Hatfield St./N. Elm St./Prospect Avenue area was directed and discharged into
a wooded area near the end of Adare Place, in an open channel which has experienced consider-
able erosion. In 1997, improvements were made to the culvert at Barrett Street and the down-
stream channel in an attempt to reduce the frequency and severity of flooding in that area. The
marsh hydrology was considered in the design and permitting of that work.
From inspection of historical photography and mappings, it is evident that the water levels within
the marsh have increased significantly within the last 25 -30 years. While agricultural use was
practiced well into the 1970s, the land is currently too wet to be tilled or otherwise manipulated.
Many areas of the marsh that were clearly plowed in the past are now under water at certain
times of the year. The diversion channel has lost its geometrical form and definition so evident
in the 1960s and `70s aerial photographs. The current boundary between marsh and channel is
difficult to discern and in many areas the channel seems to altogether disappear.
During the inspections made by BEC in the winter of 1999 -2000, the water levels found within
the marsh were spatially variable and ranged from 0" to 6" above the soil surface. The observed
water levels corresponded with the water levels in the adjacent diversion channel; however, the
water depth in the channel was generally deeper than found in the bordering marsh areas, but
only marginally so (3" to 9 Movement (flow) within the channel was apparent although ex-
tremely sluggish <0.25 feet per second).
Vegetation within the marsh appears to have changed little over the past ten years. The 1993
study by Laurie Sanders of several City wetland systems indicated a marsh dominated by com-
mon cattail with fringing immature trees (primarily red maple) and shrubs (principally speckled
alder and silky dogwood). These conditions continue today, with little sign of significant
changes. All of these species can withstand a significant degree of flooding. They may have
initially developed while the marsh was in a less persistently flooded condition. Many of the
shrubs and trees are likely at about their tolerance level of maximal flooding, but year -round
monitoring would be required to further substantiate this conclusion. The cattails are still well
within their tolerance range. Further, the cattails can adjust to slow changes in water levels by
contributing to the build -up of organic soils. In fact, these annual organic contributions may be a
driving force in the marsh's development, contributing to the increasing marsh hydrology.
Without major decreases in marsh hydrology, future changes in the marsh vegetation are likely
to be limited. Purple loosestrife, already present as a sub dominant species, is also tolerant of
inundation and could spread in competition with the cattail. However, typically a significant
period of non flooding during the growing season is required for seed germination.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 6 of 35
7
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L I
4.1 Vegetation Clogging
4.0 BIOLOGICAL FACTORS POTENTIALLY AFFECTING MARSH HYDROLOGY
As part of the assessment of the Barrett Street Marsh, an evaluation was performed on the poten-
tial for vegetation and wildlife to have affected the marsh hydrology. Vegetation can potentially
cause changes in marsh hydrology by altering the drainage mechanisms for the marsh. Certain
types of wildlife can also alter hydrology (e.g., beavers). Therefore, the marsh was examined for
evidence of channel clogging by vegetation and the potential presence of beavers or other rele-
vant wildlife.
Examination of the marsh showed that the drainage channels (former agricultural ditches)
continued to be present in a recognizable form with generally open water with several areas
of blockage created by vegetative debris "dams" within the waterways. While only minimal
clogging of the channel by live vegetation was present, significant accumulation of organic
matter and debris was noted originating from the marsh cattails, leaving only extremely
shallow drainage channels within the marsh.
Several probings of the diversion channel showed a consistent water depth of three to six
inches with underlying soft organic sediments of 3 -4 feet in depth, underlain by fine sand.
Three core samples were examined, two of which were obtained from within the central part
of the marsh, and one upgradient, just below the bike trail (Figure 3). The physical charac-
teristics of the sediment samples are discussed more thoroughly in subsequent sections of this
report.
The two cores from the marsh area were relatively consistent, with an upper layer of 6 -12"
of very loose, unconsolidated cattail fragments and decomposed organic matter with minimal
fine sand and silt. The cattail fragments were relatively undecomposed, ranging in size from
0.5 to 3 inches. The remaining portions of the cores were primarily organic mucks with little
or no recognizable plant fragments. The accumulations of cattail fragments appear to be of
recent origin, given their undecomposed state. Further, there seemed to be no recognizable
differences between the deeper and shallower fragments that might indicate many years of
deposition and gradual decomposition. Studies have indicated that cattail fragments can ex-
pect a 50 80% degradation within the first year following deposition. Presumably, as true
with most organic decomposition within soils and sediments, degradation proceeds more
slowly under anaerobic conditions than in aerobic conditions. Therefore, an organic build -up
exceeding several inches in a wetland setting would likely ensure relatively slow degradation
of the material.
4.2 Wildlife Considerations
No active beavers were observed to be present within the Barrett Street Marsh. However,
there was minor evidence of some beaver activity at the southern end of the marsh, where
several beaver cut shrubs and small trees were noted. The beaver cuts appeared to be at least
3 to 5 years old.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 7 of 35
err
Civil Engineers
296 North Math S r.et
BAYSTATE ENVIRONMENTAL
CONSULTANTS INC.
Environmental Scientists
East langnsoadam, MA 01028
Location of Sediment Samples
Photo from March 4, 1992
Scale: 1" 200'±
Portions of the marsh contain abundant evidence of a significant population of muskrat (On-
datra zibethicus). Because the muskrat population is plainly evident and their activities in-
clude alteration of vegetation during their feeding and normal habitat modification behaviors,
it is possible they are influencing flow patterns throughout the marsh. The following narra-
tive describes the basic biological data and habitat requirements of the muskrat.
Life History Factors:
Breeding Period March through October, peaking from March through June
Age of Maturity from 6 weeks to 1 year
Gestation 28 to 30 days
Litter 3 to 4 kits (south of 37 degrees north latitude), with 3 or more litters per year;
young are altricial.
Weaning 4 weeks
Life Span up to 4 years in the wild
Preferred Habitat:
Muskrats prefer sloughs, marshes, oxbow lakes, streams, levees, dikes, and small lakes
and ponds. Muskrats build lodges in or near water, using marsh vegetation (e.g., cattails).
Alternatively, they construct elaborate bank burrows that may be up to 50 feet long. En-
trances to both lodges and burrows are usually under water, and both are multi-
chambered. During periods of low water, muskrats dig canals from lodges and burrows
to deeper water areas. They also build feeding platforms to get out of the water to eat or
feeding huts for protection from the elements and predators. Muskrats will usually stay
within 50 feet of their lodges while foraging, although they can range out to over 500
feet.
Barrett Street Marsh offers a good habitat for the muskrat, providing a ready building
material for their lodges and feeding platforms. Approximately 12 muskrat lodges were
observed in field visits in January, 2000, with more potentially present throughout the
marsh.
Cover Requirements:
Muskrat populations tend to be higher in areas with dense aquatic, emergent vegetation
that is surrounded by terrestrial herbaceous vegetation. Forested riverbanks usually do
not support muskrat populations. High quality habitat is characterized as an area of dense
emergent vegetation with fifty percent or less of the area being composed of open water.
If habitats become "choked" with vegetation, muskrat numbers will be low. Ideal ratios
for vegetation to open water are 75:25 to 80:20. The observed ratio of vegetation to open
water at Barrett Street marsh was estimated at 90:10.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 9 of 35
In riverine habitats, water levels and velocities affect muskrat habitat suitability. Typi-
cally, if levels are too low, food availability will also be low. This is most pronounced in
winter when low water levels allow freezing of the substrate, killing food and cover spe-
cies. Stream gradients and velocities have been studied in Massachusetts to determine
habitat selection by muskrats. Streams with gradients more than 47.5 feet per mile and
flows less than 4 cubic feet per second (cfs) did not support muskrats. However, musk-
rats were found in streams with gradients less than 32.2 feet per mile and flows greater
than 4 cfs. River habitats with flows greater than 1,000 cfs typically experience scouring
and water level fluctuations too great to support muskrat populations. In some cases,
fluctuating water levels of more than a 2 -foot rise force muskrats out of burrows and
lodges. Depths of between 18 inches and 4 feet may be ideal. Within Barrett Street
Marsh, the stream gradient is far less that 32.2 feet per mile, with average flow below 4
CFS. Water depths within the preferred range for the muskrat can be found.
Muskrats need emergent vegetation and a firm substrate for building lodges. They rarely
use submergent vegetation. Optimum sites for bank burrows are on slopes of 30 degrees
or more, with a minimum height of 18 inches. Maximum breeding density for muskrats
is about 2 pairs per acre.
Food Habits:
Muskrats eat the basal parts, rhizomes, and leaves of aquatic emergent vegetation. Al-
though they consume mostly plant material, they eat some fish, crustaceans, dead birds,
and frogs. Plant food species vary with muskrat distribution, but some of the major foods
include cattail, bulrush, and sedge, all of which are in abundance within the Barrett Street
Marsh. Other food species include arrowhead (Sagittaria spp.), waterlily (Nymphaea
spp.), wild rice (Zizania aquatica), sweetflag (Acorus calamus), pondweed (Potamogeton
spp.), pickerelweed (Pontederia cordata), spikerush (Eleocharis spp.), smartweed (Poly
gonum spp.), clover (Trifolium spp.), bluestem (Andropogon spp.), rice (Oryza spp.),
panicgrass (Panicum spp.), paspalum (Paspalum spp.), burreed (Sparganium spp.), millet
(Echinochloa spp.), willow (Salix spp.), poplar (Populus spp.), and some crops. They
also consume acorns and maple (Acer spp.) samaras.
Predators:
Within the Barrett Street Marsh, the likely muskrat predators include, raccoon (Procyon
lotor), bobcat (Felix rufus), house cat (F. domesticus), domestic dog (Canis familiaris),
and possibly snapping turtle (Chelydra serpentina). However, predation is likely a small
factor in the life history of the local population. Muskrats will kill the young of other
muskrats when populations are too dense. Other typical predators of muskrat can include
humans, mink (Mustella vison), coyote (C. latrans), red fox (Vulpes vulpes), barn owl
(Tyto alba), barred owl (Strix varia), great horned owl (Bubo virginianus), northern har-
rier (Circus cyaneus), bald eagle (Haliaeetus leucocephalus), eastern cottonmouth (Ag-
kistro piscivorus), and largemouth bass (Micropterus salmoides).
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 10of35
Management Considerations:
A variety of animals use muskrat lodges including snakes, turtles, toads, and Canada
geese (Branta canadensis). Muskrats can reduce cattail enough to allow purple loosestrife
(Lythrum salicaria), an undesirable weed, to replace cattail and degrade marsh quality.
Management of water levels can have a strong impact on muskrat habitat because of
fluctuation influences on certain food species. Drawdowns can have a negative impact
on muskrat populations. Low water levels may encourage undesirable species to take
over. Prolonged flooding can alter food plants distribution. Recommended water levels
(in the state of Maine) are between 6 and 20 inches.
In some cases, muskrat populations can have cyclic populations due to population
"booms" that lead to food source depletion "eat outs requiring vegetative recovery
prior to the regrowth of the muskrat population.
Biological Implications for Marsh Flooding
Based upon the observed conditions within the marsh, it seems reasonable to hypothesize
that cattail fragments have recently and rapidly contributed to a significant reduction in
the channel hydraulics, allowing an increase in the water level and alteration of the entire
marsh hydrology. Given that the cattails are a primary food and building material of the
muskrat, it also seems reasonable to presume that the muskrats have at least contributed
to the rapid and recent buildup of organic matter within the marsh and channel. How-
ever, it should be noted that a viable muskrat population has been present within the
marsh for quite some time. Their presence was noted in the 1993 Natural History report
by Laurie Sanders. It is unknown why the effects of cattail accumulation within the di-
version channel would appear to have occurred only in the past few years. However, it is
possible that the changes were initially more gradual, until the marsh water level reached
an optimum threshold that allowed the local muskrat and /or cattail population to rapidly
increase.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
PageIl of 35
5.0 MARSH AND DIVERSION HYDRAULICS
From a review of the available information, it is clear that at the time of the diversion of King
Street Brook, the Barrett Street Marsh area was ditched for drainage purposes and presumably
flowed northward similar to today's pattern. It is presumed that maintenance of the King Street
Brook Diversion has been a continued necessity due to the flat stream gradient and its inability to
maintain sediment transport and, thereby, self -clean the channel. The 36" pipe under Barrett
Street, which was replaced in 1997, had its invert at elevation 138.77. The invert at the bike trail
culvert, 1,740 feet upstream, is elevation 139.6 which represents a potential streambed gradient
of just 0.048 or 2.5 feet per mile.
An exact determination of the diversion channel's natural ability to maintain this potential gradi-
ent within the conditions of its current watershed and other channel characteristics would be dif-
ficult, if not impossible to obtain. Stream morphology and the processes of erosion and sediment
transport and deposition are complex subjects and are often broadly categorized from interpreta-
tion of observable and measurable phenomena. In geologic terms, a stream can be described as
either aggrading or degrading. In an aggrading stream, the slope or gradient is decreasing over
time, due to the stream's inability to transport the actual sediment load being delivered by the
watershed. A degrading stream has a gradient that is increasing over time, as the streambed is
eroded by flows which are capable of sediment transport greater than the amount of sediment
which the watershed actually delivers. For Barrett Street marsh and the King Street Brook Di-
version, observation of the mild stream gradient and the accumulated sediments within the chan-
nel lead one to conclude that the diversion is aggrading. An inspection of the stream/diversion
profile through the Barrett Street marsh can be helpful in analysis of the diversion channel's cur-
rent condition.
On February 4, 2000, BEC personnel performed a field topographical survey of the King Street
Brook Diversion. The marsh and channel were covered with a thin mantle of ice that facilitated
access to the diversion channel. Measurements were taken of the water surface elevation within
the channel from the Barrett Street crossing to the rail trail culvert. Observation points were
spaced at 50 -100 foot intervals. A plot of the data obtained has generated a profile of this entire
reach of the King Street Brook Diversion, which is shown on Figure 4. While the profile repre-
sents the diversion's hydraulic grade line (water surface), the water depth at each observation
point was consistently in the 3 -6" range; therefore, the profile is also representative of the
streambed gradient.
The profile sheet and channel alignment plan (Figure 5) reveal many of the diversion's physical
and hydraulic characteristics. The water level immediately downstream of the bike trail is about
9" higher than the crown of the 4' x 4' culvert under the bike trail embankment. A buildup of
organic debris and sandy sediment has created a 1 /4 -acre impounded area immediately below the
rail trail culvert, where the water surface elevation is as much as 12" higher than the adjacent
downstream areas (Area I, Figure 5). Water flows over the matted sediment and debris in small
rippling cascades at numerous points along the perimeter of this higher area. The water level
within the Stop Shop detention basin is at or just slightly lower than the elevation of the higher
area. At the time of observation, a portion of the diversion's flow was actually passing through
the detention basin itself.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
-P- age -12 -of 3
Clef'
OBSERVED
W.S.E. AT STOP SHOP
DETENTION BASIN, 3/1/00
CROWN OF BOX CULVERT,
EL. 145.59
W.S.E. 142.77, 12/11/89
(Stop Shop Plans)
INV. 4X4 BOX CULVERT
AT RAIL TRAIL 139.6±
BAYSTATE ENVIRONMENTAL
CONSULTANTS INC.
Civil Engineers Environmental Scientists
296 Hart Main Street East Langmaadaw, IA 01025
145
144
143
BIKE BARRETT
TRAIL STREET
142
141
140
139
0+72
kz EL. 143.41
DEBRIS DAM
TOTAL DROP FROM RAIL TRAIL TO BARRETT ST. WEIR 3.85'
TOTAL LENGTH 1,741 LF
AVERAGE SLOPE 0.22%
1.08' DROP/1,400 LF
WATER SUR
MEASURED
0.077% SLOPE
FACE AS
ON 2/4/00
SCALE
H: 1" 200'
V: 1" 1'
S 0.048%
Potential Gradient Prjor t Iflst of rett
Installed in 19.9.7
S —0.05%
ial it if Channel
Potent Graden Excavated to ved of 4' X4' Box Culvert
EL.
17+41
W.EI R
140.50
(1997)
1.83' DR()P/269 LF
0.68% SLOPE
14
EL.
72
14-2:33
145
144
143
142
141
0+00 2+00 4+00 6+00 8+00 10+00 12+00 14+00 16-1-00 18+00
HYDRAULIC GRADE LINE OF THE KING STREET BROOK DIVERSION CHANNEL
AS OBSERVED ON_ FEBRUARY 4, 2000
INVERT EXISTING
24" CULVERT
139.80
INVERT EXISTING
24" CULVERT
138.8
INV. ORIGINAL
36" CULVERT UNDER
BARRETT ST. 138.77
Figure 4
After this initial abrupt drop in elevation, the diversion channel gradient decreases and enters
what appears to currently be the wettest portion of the Barrett Street Marsh (Area II, Figure 5).
Over the next 1,400 feet, the stream drops just 1.09 feet, at an average gradient of 0.077 or 4
feet per mile. As opposed to a constant slope over this length, this area is characterized by a se-
ries of steps, with stretches of tranquil low- gradient flow located between quick drops of more
rapid and steep flow into the next quiescent reach. The steps appeared to be formed by channel
obstructions of organic debris composed almost entirely of cattail litter. Photo 1 clearly shows a
recent high water mark just upgradient of a representative step in gradient, and Photo 2 shows
the typical short, rapid flow from one quiescent area to another. Flow within the low gradient
areas is so slow as to be almost imperceptible, while obviously evident at the transitions.
At least two of the gradient transitions occurred at or near substantial woody growth presumably
contributing to obstructing the flow (Photo 3). The last of these transition areas is located ap-
proximately 270 feet upstream of Barrett Street. At this point, the diversion channel completely
changes character and becomes a rapidly flowing brook with numerous steps and small shallow
pools (Photo 4). The average gradient in this last 270 -foot section (Area III, Figure 5) of the
diversion is almost an entire magnitude greater than that of the previous 1,400 feet. The stream
channel here is typical of a natural brook of moderate gradient in an alluvial, wooded setting.
Although small areas of accumulated debris could be found at various intervals along this reach,
these appeared to have little influence in the overall character of this last section of the diversion
channel prior to its passing under Barrett Street.
At the time of these field investigations, water flow over the new weir at Barrett Street was ap-
proximately' /4 -inch deep representing a flow rate of about 0.1 cubic feet per second (50± gallons
per minute). The weir was apparently having no influence on the water levels within the marsh.
In fact, under the observed hydraulic condition of the diversion channel, it is difficult to imagine
the weir functioning as the hydraulic control for the marsh under any flow scenario.
Probings of the accumulated sediments were performed at numerous points along the diversion
channel. The depth of accumulated sediments within the channel was consistently in the range
of 3 to 4 feet. The deposition of sediments within the diversion channel has undoubtedly de-
creased the channel's hydraulic capacity and the flood carrying capacity, leading to higher ele-
vations of both baseflow and flood waters in and adjacent to the marsh. Additionally, ground-
water levels in the area have been influenced by sedimentation of the diversion channel, as rising
water levels within the channel have led to increases in adjacent groundwater levels.
The weir at Barrett Street was constructed at an elevation approximately 0.9 feet higher than the
invert of the 4x4 box culvert under the bike trail. Excavating the diversion channel down to the
weir's elevation of 140.5 could lower the water levels in the middle third of Barrett Street Marsh
by as much as 2.5 feet, and could lower water elevations near the Stop and Shop detention basin
by as much as 3.5 feet. If such excavation were to be performed, the weir would likely then
function as the hydraulic control for the marsh. The channel slope from the box culvert to the
weir at Barrett Street would have an adverse (uphill) gradient, as shown on Figure 4. The box
culvert at the bike trail embankment would still be at least 0.9 feet underwater, and the channel
and this lower part of the box culvert would quickly be filled in with accumulating sediments.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 15 of 35
Photo 1: Choked diversion channel note debris along recent high water mark
Photo 2: Typical short, rapid flow from one quiescent area to the next
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 16 of 35
Photo 3: Woody growth present in some areas of the diversion channel
Photo 4: Rapidly flowing final reach of the diversion channel immediately upstream of Barrett St.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 17 of 35
6.0 SEDIMENT COMPOSITION AND LOADING ESTIMATES
6.1 Sediment Composition
Sediment samples were obtained from the King Street Brook Diversion channel in February,
2000, for physical inspection and analysis. The samples were obtained by 2" corer forced
into and through the sediment column followed by extraction. A total of three (3) represen-
tative samples were retained from the locations shown on Figure 3.
The retained samples were transported to the offices of BEC for inspection and composi-
tional analysis. The two samples obtained from within the central marsh area were very
similar in composition and are characterized by an upper layer of low- density organic debris
composed primarily of cattail litter with relatively small amounts of mineral sediments (silt
and fine sand) within the matrix of decomposing vegetative matter. Below this upper layer
was found a distinctly different material of higher density and increasing mineral content.
The boundary between the two sediment types was distinct and abrupt. Free water above the
upper layer was in most locations limited to a depth of 3 -6 The flow of water in the diver-
sion channel was noted to be sluggish and capable of transporting only the smallest organic
particles. The flow was estimated at 0.10 0.25 cubic feet per second. No precipitation
events had occurred within the previous 72 hours.
The sediment sample collected from immediately below the bike trail culvert was composed
of medium to coarse sands with very little organic matter. This composition indicates that
flow from upstream areas is capable of significant sediment transport within the King Street
Brook channel that is deposited immediately below the bike trail culvert due to the diversion
channel's flat gradient and inability to transport the sediment further downstream.
Physical characteristics of the marsh sediments are noted in the following Tables 1 and 2.
An estimate of the total volume and dry weight of sediments within the King Street Brook
Diversion channel is made below.
Channel top width 15 feet (all dimensions estimated)
Channel bottom width 4 feet
Channel depth 3.5 feet Cross sectional area 33 square feet
Channel length within the Barrett Street Marsh 1,740 linear feet
Channel Volume 57,000 cubic feet (2,100 cubic yards)
Total Water Content at 49.5 lb /cu.ft.
Total Mineral Content at 22.5 lb /cu.ft.
Total Organic Content at 4.8lb /cu.ft.
1,400 tons
640 tons
140 tons
Assuming that the dry sediments would have a density on the order of 90-100 lb /cu.ft., the
total dry volume of the sediments within the channel is approximately 650 -700 cubic yards.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 18 of 35
Table 6.1. Sediment Composition Within Diversion Channel
Sample
Depth from
Surface
Compositional Description
A
B
0 3"
Water
3" 8"
Loose fibric organic sediments recognizable cattail litter
8" 15"
Sapric muck decreasingly fibric; holds shape out of core tube
15" 19"
0 3
Sapric muck decreasingly fibric; increasing v.f. sand content
Water
3" 101/2"
Loose fibric organic sediments visible fibers 100%
101 /2" 12"
Slightly consolidated fibric organic sediments v.f. 50%
12" 19"
Consolidated sapric organic sediment visible fibers <5%
19" —10 -1 /8"
'747'
Consolidated sapric organic with more gritty texture
s ?SF23F.s a. .a�.., r gsE'
7 _K
C
v' s.
0 6"
.:L ,.u.x..
Water
6" 6 -1/4"
Loose organic material
6 -1/4" 10"
Coarse sand
10" 11.5"
Medium coarse sand with organic matter
11.5" 14"
Coarse sand
14" 19"
Medium sand
Table 6.2. Physical Descri
Incremental
Sediment Depth below
Sample Water Surface
tion Of Sediment Samples
Water
Content
In -situ
Density,
lbs /cu.ft.
lbs /cu.ft.
Mineral
Content
lbs /cu.ft.
Organic
Content
lbs /cu.ft.
10 -12
16 -18"
A
B
10" 12"
68
16 -18"
91
67
81
Avg. 76.8
77
52
68
55
49.5
17
48
19
26
12
44
13
21
22.5
6
6
6
4
4
5
4.8
Overall, it appears that the bulk of sediment (by volume) accumulated within all but the up-
permost portions of the diversion channel is principally organic in composition, comprised
mostly of cattail fragments. The upper sediment layers are highly fibric, with undecomposed
fragments, whereas, the lower layers are sapric (composted) organics with fine mineral con-
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
—Page 19 of 35
tent. The implications of this conclusion are that control of mineral sedimentation within the
channels will not be sufficient to prevent the formation of drainage blockages.
6.2 Sediment Loading Analysis
The watershed contributing to the Barrett Street Marsh is primarily composed of developed
areas characterized by narrow residential neighborhood streets with a few larger collector
streets. The topography is rather variable characterized by grades ranging from 1% in the
area north of Prospect Street, located in the lower reaches of the watershed, to 8% on Round
Hill, located in the upper reaches of the watershed. Other land uses in the watershed include
the Rail Trail Bikeway and its margins, composed of a paved strip atop an abandoned,
wooded railroad embankment; a portion of Child's Park, composed of open lawn, gardens,
and woods; a few small areas of meadow along Jackson and Barrett Streets, and the Stop
Shop and Carlon Drive developments. The watershed does not contain any large areas un-
dergoing significant construction or alteration and, therefore, is considered to be relatively
"mature The 36" CMP culvert that discharges near the end of Adare Place has caused sig-
nificant erosion in the past which is ongoing although at a much reduced rate, as the gradient
here has been reduced such that erosion is now primarily occurring at the pipe end. While
some naturally occurring soil erosion may be contributing to sediment generation, it is as-
sumed that the primary source of any significant sediment loading to the Barrett Street Marsh
is derived from winter road sand application within the watershed.
Analysis of sediment loading due to winter road sanding within the watershed is based upon
Northampton Department of Public Works (DPW) records indicating city -wide use of an av-
erage of 6000± lbs. of sand annually over the past twenty years. Applied over a total of 156±
miles of roads within the City, this usage equates to an average application rate of 38 tons per
mile per year (t/m/y). Consideration of this average must include the wide variation in sand
use from one year to any other, which, in extreme, varies as much as 50 Also, not all City
streets receive equal applications of sand. Major roads, which comprise 20% of total road
miles within the watershed, receive heavier than average applications. Steeply graded streets
make up approximately 2% of total road miles and also receive heavier applications of road
sand. The majority of watershed road miles within the Barrett Street Marsh watershed are
minor residential streets, which may receive less than average applications.
For the purposes of this analysis, the watershed has been divided into three areas of road sand
use (Figure 6). Subarea 1 (A1) is the largest, encompassing the densely populated residential
areas to the south of the Barrett Street Marsh, Subarea 2 (A2) contains a smaller pocket of
residential area to the southwest of the marsh, and Subarea 3 (A3) includes the area west of
the marsh along Jackson Street and east of the marsh including Carlon Drive and the Stop
Shop property. Attempting to account for the non uniform application of sand from road to
road, the rate of sand application has been adjusted for different street uses and types. Roads
within the watershed are divided into three categories: major roads, minor roads, and steeply
graded streets. The following assumptions weigh the distribution of road sand application
across the three categories: major roads receive 30% more than average, minor roads receive
10% less than average, and steeply graded streets receive 20% more than average. Applying
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 20 of 35
these assumptions results in adjusted application rates of 49 t/m/y, 34 t/m/y, and46 th-niy; re-
spectively, for each road category.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 21 of 35
U
n
r
nre
Civil Engineers
296 North Main Sire
BAYSTATE ENVIRONMENTAL
CONSULTANTS INC.
Environmental Scientists
Eat Langmeodow, MA 01028
Road Sand Use Areas
Scale: 1" 1000'±
Figure 6
The estimated annual sand usage in the watershed is realized by applying the adjusted appli-
cation rates to the road miles in each road category. The following table summarizes the es-
timated road sand usage in the watershed.
Table 6.3. Estimated Annual Sand Usage Within the Barrett Street Marsh Watershed
Subarea
Al
Road Type
Major
Minor
Steeply Graded
1.25
Major
Subarea Total:
49
Minor
0.82
34
Road Miles
(miles)
1.40
6.65
0.20
Adjusted
Application Rate
(tons /mi /yr)
49
34
46
Subarea Total:
49
Minor
0.15
34
Subarea Total:
Total Estimated Sand Usage:
Say:
Estimated
Sand Usage
(tons /yr)
69
226
9
304
61
28
89
5
69
462
460
Assuming the density of sand to be approximately 1.35 tons per cubic yard, the estimated
sand usage equates to around 340 cubic yards.
To estimate the sediment loading to the Barrett Street Marsh, assumptions have been made
regarding the extent of stormwater management within the watershed. Most of the streets in
the watershed have stormwater catch basins, many of which have deep sumps that are
cleaned out on an annual basis. It is assumed, therefore, that roughly 50% of the road sand
materials will be removed by the existing catch basin system. Annual street sweeping in the
watershed may account for an additional 25% removal, resulting in an overall sediment de-
livery rate or yield of approximately 25 The resulting annual sediment loading potentially
reaching the marsh is, therefore, approximately 115 tons, or 85 cubic yards.
The described methodology for developing this approximation has obvious limitations.
However, the resulting value is a useful tool in estimating the magnitude of sediment loading
to the Barrett Street Marsh. In addition to the road s analysis, the
of sediment load
gated for the presence of any actively eroding areas
No other significant sources were noted in our investigations.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 23 of 35
For a submerged weir, a relationship exists between upstream and downstream heads and the
discharge over the weir. A published plot of these relationships developed from experimen-
tal data was used to determine the discharge through the system under submerged conditions.
For head elevations above the top of the weir, the outlet was modeled as two orifices. The
stage- discharge model provides a more accurate representation of the flow capacity of the
outlet structure under the current high water conditions.
Final routing of storm discharges through the new model in HydroCAD was performed for
the 2 10 and 100 -year rainfall events; however, changes in the configuration of outlet de-
vices were made to allow for the stage- discharge model. The new model included the stage
discharge model, specified as the primary outlet, and the 10 -foot wide emergency spillway as
the secondary outlet. Also, the starting elevation was changed to the existing water surface
of 144.0. The culvert was eliminated as an outlet device as it was determined to have suffi-
cient capacity to easily convey these flows even under the existing tailwater (submerged
outlet) conditions. Table 7.2 compares the results of the current conditions against the origi-
nal model with respect to peak elevations and discharges.
Table 7.2 Peak Elevations and Discharges, Original Model vs. Current Conditions
Current Conditions
Rainfall
Event
2 -year
10 -year
Original Post Development Model
Peak Discharge
(cfs)
Peak Elevation
(ft.)
143.8
144.6
145.4
1.5
4.0
5.7
Peak Elevation
(ft.)
144.7
145.3
145.8
Peak Discharge
(cfs)
2.92
4.66
11.19
100 -year
Note: Flood elevation at top of berm 146.0
Emerg. Spillway at elev. 145.5
Analysis of current conditions indicates that, although the storage capacity within the deten-
tion basin is adequate to prevent overtopping of the basin embankment, the peak flows from
the basin are in excess of those from the original design and also exceed pre development
discharge rates as analyzed previously.
7.2 Water Quality Design Aspects
The detention basin was designed to treat water quality as well as water quantity. Although
the application pre -dated the MADEP storm water requirements that are currently in force,
the basin design incorporated several features that would be consistent with current regula-
tions. The basin included a vegetated forebay followed by a much larger elongated shallow
marsh detention basin with a small amount of permanent open water near the outlet. Ap-
proximately 15,000 plants were incorporated into the basin design with 11,750 herbaceous
plants associated with the shallow marsh system. Ts were hundred
d with l tha wet meadow
sociated with the open water area and 2,000 plants
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 25 of 35
area. Herbaceous plantings included cattail, picklerweed, sweet flag, burweed, bulrush duck
potato, water lily, pond weed, wild celery, sedge, and soft rush.
The constructed detention basin generally appears to be as designed in terms of its overall
morphometry, although there appears to be some problems with the outlet structure (see dis-
cussion under Water Quantity Design). The water levels within the detention basin are far in
excess of the original design levels which were predicated on the invert out of the basin and
potential infiltration within the pool area. Recent water accumulation within the basin at
higher than expected levels appears to be in large part a result of higher average water levels
within the marsh. This has resulted in average water levels at or near the top of the outlet
pipe to the detention basin. The water levels within the basin appear to be set by the water
levels within the outlet discharge pool which in turn are determined by water elevations
within the marsh.
As a result of the changed marsh hydrology, the area of permanent open water within the
detention basin incorporates much of the area originally depicted as shallow marsh. A re-
view of the basin was conducted during winter months and, therefore, an accurate determi-
nation of surviving vegetation could not be made. However, based on this examination, there
appears to be little evidence that the nearly 12,000 shallow marsh plants had any significant
survival. However, some of the species of the 211 aquatic plants were observed to be present.
Of the shallow marsh species, only the cattails were noted to be in moderate abundance
fee the periphery of the of er m extending
anent pool achieves sa 1.5 foot depth within 50 feet of the outlet.
feet. The depth o the per pool
within the permanent pool exceed 2.5 feet. It is possible that during summer low
rainfall period that the elevations within the basin may be significantly diminished. How
ever, it can be expected that the average elevation of water within the basin will be signifi-
cantly above the invert out at the outlet structure if the marsh water elevations persist outside
the basin.
Relative to water quality function, the stormwater management system offered water quality
improvement through the following items:
Catch basin sumps;
Forebay;
Shallow marsh;
Open Water;
D -Basin Maintenance program.
The catch basin sumps are unaffected and still likely provide the level of water quality im-
provement as designed and approved. Within the detention basin the forebay, shallow marsh,
and open water all provide a sequential series of potential water quality treatments by allow-
ing opportunity for sedimentation to occur and biological uptake by plants. While the fore
bay and marsh areas are still present, they are submerged. Nevertheless, sediment trapping
can continue to occur within the sediment forebay and marsh portions of the basin. The
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 26 of 35
Examining current MADEP storm water management policy and the total suspended solids
J removal predicted for various types of storm water management features, the TSS removal
for the approved and existing basins would be as shown in the table below:
r
L
L
vegetation originally planted within the open marsh area as well as vegetation with the open
water was provided to improve water quality by the biological uptake of nutrients by plants
as well as sequestration other contaminants on living or decaying organic matter. Despite the
probable loss of most of the 12,000 shallow marsh plants, it is likely that the 211 open water
plants are rapidly multiplying to overtake the additional habitat provided due to the elevated
water elevations. While the literature is quite poor relative to the abilities of different vege-
tative species to remove and sequester storm water associated contaminants, there is no rea-
son at this point to believe that the open water vegetation will be less effective at removal of
storm water contaminants than the originally proposed shallow marsh plants. Therefore, it is
quite likely that for normal rainfall events that the basin will continue to provide the same or
similar water quality treatment as originally proposed. However, as noted in the water quan-
tity section, the post development flow rates out of the basin are higher than originally ap-
proved, and therefore, there will be a shorter duration during which storm flows will have the
opportunity to receive treatment.
Table 7.3 Stormwater Management System Removal of Total Suspended Solids
Cumulative TSS Removal
Best Management Prac-
tice
Catch Basin Sumps
(2 ft. deep)
Sediment Forebay
Constructed Wetland
Wet Pond
Totals
DEP allowed TSS
Removal Rates
10
25
80
70
NA
Detention Basin as
Approved
10
32.5
86.5
NA
86.5
Existing Detention
Basin
10
32.5
NA
79.75
79.75
Overall, the predicted removal of TSS according to MADEP criteria is slightly higher for the
originally approved basin. It could be argued that the originally designed forebay, which is
now entirely submerged, has been merged into the larger detention basin, thereby eliminating
the 25% credit for the existing detention basin. As a practical matter, the volume of the sedi-
ment forebay is still present and most likely provides an equivalent level of treatment. Over-
all, the changes are minor with respect to water quality treatment and probably not signifi-
cant.
7.3 Detention Basin Setting and Construction
The observed setting of the existing detention basin is not as was described in the plans and
documents approved by the City of Northampton during the 1996 -97 review of the proposed
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 27 of 35
r--,
L
Carlon Drive subdivision. Most noticeable, the water level within the detention basin is at
elevation 144.0, which is 1.5 feet higher than originally presented by the project proponent.
The reasons for this appear twofold. Firstly, the groundwater levels in the area of the deten-
tion basin are high enough to limit infiltration through the basin bottom. Apparently, the
groundwater elevation at the detention basin is equivalent to the water surface elevation at
144.0. Note that in the fall of 1996 during the subdivision proposal review, the static water
level in an existing groundwater monitoring well near the site of the detention basin was ob-
served at elevation 143.2 This height was explained by the proponent as a "perched" or
temporary groundwater condition. At this time it appears that the levels observed in 1996
probably were reflective of the actual water table in the area of the detention pond.
The proponent also indicated that groundwater elevations within the area of the detention ba-
sin would not rise above the design level of the permanent pool within the basin (elev.
142.5), as the waters would drain out of the outlet structure to downstream areas. As con-
structed, the waters within the basin cannot exit the pond at levels lower than elev. 144.0, due
to the presence of high ground at the pond outlet. The outlet was intended to be free drain-
ing, but is instead located approximately 1.8 feet below the surrounding grade. In our Febru-
ary, 2000, survey of the detention pond, the entire area near and within 100 feet of the pond
outlet was found to be at least 18" higher than the pond outlet.
The most topographically- direct route from the detention basin outlet to the King Street
Brook Diversion channel is approximately 500 feet in length, along a broad depression across
an area once used for agricultural purposes. The observed water level in the diversion chan-
nel where this route intersects was found to be at elevation 143.0, which is 0.8 feet higher
than the pond outlet. For the pond to drain as designed, a channel or ditch would need to be
constructed from the pond outlet to the diversion channel, and the water, level in the diversion
channel must be lowered by at least one foot below current levels.
If the sediments are excavated from the King Street Brook Diversion channel, it is antici-
pated that groundwater levels in the area will drop. Full excavation of the diversion channel
to the elevation of the weir at Barrett Street could lower groundwater levels near the Carlon
Drive detention pond to the pond's design elevation (142.5) but probably not below this
level.
7.4 Summary
Although the Carlon Drive detention basin was designed and permitted prior to the Massa-
chusetts Department of Environmental Protection's Storm Water Management Policy, the ba-
sin compares favorably with these published guidelines. The attenuation of post
development peak runoff rates has been somewhat compromised by actual hydrogeologic
conditions causing the basin to continually hold water at a level higher than originally antic
pated. Given that the basin is so hydraulically distant from the Barrett Street Marsh, per i-
these differences are most probably insignificant. As demonstrated elsewhere within this re-
port, the diversion channel could actually benefit from clean higher flowrates which would
act to scour the accumulating sediment and debris from within the channel and flush these
downstream. In this particular setting where gradients are extremely flat and erosion be-
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 28 of 35
tween the detention basin and the channel is riot problematic the dominant stormwa er man-
agement issue then becomes water quality. The Carlon Drive detention basin performs well
at removal of suspended solids and for all practical purposes complies with the TSS removal
rates of the MADEP's Stormwater Management Policy. In consideration of the data and
suggestions presented within this report, it is likely that the Carlon Drive detention basin, as
observed during the preparation of this report, could be permitted under the current regula-
tory framework.
U
`.J
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 29 of 35
8.0 POTENTIAL CORRECTIVE ACTIONS AND RECOMMENDATIONS
8.1 Potential Corrective Actions
In simplest terms, an aggrading channel such as the King Street Brook Diversion is one that
tends to fill with sediment. The problem with the diversion is essentially one of imbalance
between the sediment load contributed to the channel and the ability of the flow to transport
the sediment load through the channel. It is arguable that for the King Street Brook Diver-
sion, a balance may have never existed, but establishment of a quasi balance may be possible
by either reducing the sediment inflow, increasing the transport capacity, or a combination of
the two.
Measures to reduce sediment loading can take many forms. Since the watershed contributing
to the Barrett Street Marsh is relatively mature and not actively eroding, general non -point
source soil conservation measures would probably not significantly reduce sediment loading.
Correction of any actively eroding areas should be a priority, including the storm drain dis-
charge opposite Adare Place. Limitations on the use of winter road sand within the Barrett
Street Marsh watershed would most likely have significant and beneficial impact on the
sediment loading. An expanded program of street sweeping and catch basin cleanout within
the watershed may also provide appreciable sediment reductions. Additional sediment trap-
ping structures such as traps and open basins would provide significant and immediate re-
ductions in sediment loading and may be the most effective tools available to the City. In
evaluating the use of such structures, the potential effects on flow control must also be con-
sidered, as reduction of wet weather or flood The sediment control basins decrease
ust not be so large
sediment carrying capacity of the ch a�
as to significantly attenuate peak flow rates entering the marsh.
Increasing the sediment carrying capacity of the channel can be performed by changing its
cross sectional geometry to maximize the transport capacity of the available flow. In effect,
this was the methodology utilized in the recent channel improvements downstream of Barrett
Street.
Because such an extended period of time has elapsed since the diversion was last maintained,
the accumulated sediments within the channel must be removed in order to arrest or reverse
the hydrological changes which have occurred at and around the Barrett Street Marsh. How-
ever, under today's wetland protection regulations, alteration of the channel hydrology will
need to be balanced with protection of the marsh hydrology. Several methodologies to re-
store the channel and lower the hydraulic grade line by excavation are described below.
Hand Excavation
Although this method may not be practical if it is desired to excavate the entire diversion
channel within Barrett Street Marsh, selected areas may be cleared of obstructions and
debris by hand tools and labor using no mechanized equipment. Cables and winches may
be used to drag vegetation across the marsh to access points along the perimeter. Most of
the removed material would likely remain within the marsh, cast alongside the diversion
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 30 of 35
channel. Costs for hand excavation are anticipated to. be relatively low, and the total
amount of work can be kept to the minimum necessary to achieve the desired results.
Mechanical Excavation
The channel could be excavated using heavy motorized equipment such as excavator or
dragline that would access the work by travelling alongside the channel, most likely atop
portable mats for ground pressure distribution. Unless a temporary road is constructed to
allow access by dump truck to the work area, the excavated spoils would have to be
spread alongside the channel. These could be leveled by the excavating equipment to
avoid establishing an unsightly windrow of material. The spoils will be saturated when
removed and will not be capable of supporting steep slopes; thus, some creep of the mate-
rials back into the channel could be expected. Following the initial excavation effort,
future maintenance could be performed without the use of mats, as the water table would
be below the ground surface and soil bearing strengths could likely support tracked vehi-
cles.
Hydraulic Dredging
A small, remotely controlled hydraulic dredge could be floated within the diversion
channel, with the accumulated sediments being removed by pumping as a slurry. This
methodology would require the use of a temporary containment area to dewater the sedi-
ments prior to their final disposal. Alternately, mechanical dewatering in the form of belt
filter press or centrifuge could be done. While generally recognized as a relatively be-
nign form of aquatic excavation, hydraulic dredging would be costly and would require
specialized equipment and expertise. Additionally, since the sediments would have to be
pumped as a slurry, the marsh would have to supply the water necessary to mix with the
sediments. While this water would be returned to the marsh as the sediments are dewa-
tered, it is possible that production levels would be very low due to a lack of suitable
quantities of water within the marsh except during wet weather.
Rotary Ditching
A technique very common in other parts of the country, rotary ditching involves the use
of mechanical equipment which simultaneously excavates the sediments and sprays them
across the land in much the same fashion as a snowblower removes snow from a drive-
way. The equipment is typically towed behind a tractor, excavator, or amphibious vehi-
cle and is used extensively in the mosquito control industry. The ditcher wheel has dig-
ging cups mounted on it and as it excavates it throws the finely tilled earth as far as 100
feet or more, thus eliminating the need for spoils leveling or removal. Rotary ditching is
well suited to cleanout of existing channels. Several passes might be necessary to
achieve the desired depth of channel.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 31 of 35
As mentioned earlier in this report, excavation of the diversion channel-to- the elevation -o of e
Barrett Street weir would immediately lower both surface and ground water levels through-
the Barrett Street Marsh and its vicinity. To prevent flooding and restore the prior hy-
d ro 0 1 gic regime within the Barrett Street Marsh and its vicinity, lowering the hydraulic grade
line y, the lowest practical partial excavation of the elevation
channel should also be considered in the interest of main-
nately, excavation
taining the habitat and diversity which the existing open marsh areas represent.
Simple removal of the most offending snags in the diversion channel by hand labor would
likely have significant benefit and would be the simplest and least expensive methodology
for improving the channel hydraulics and lowering the hydraulic grade line. This work could
be done at any time and would be non disruptive, straightforward, and quick. The use of
herbicides to control the growth of emergent vegetation in and around the channel could be
considered as a way to avoid future channel obstruction, although such practice would likely
be met with overriding public opposition.
Sediment traps could consist of closed, manhole -like structures located underground or could
be constructed in the form of open pools similar to detention basins. The structures could be
offline from the main channel inflow or could be installed inline with the channel. Ideally,
the structures would have little effect on flow rates within the King Street Brook Diversion
so that scouring flows are maintained to the maximum extent possible. The need for ease-
1 ments and access for cleaning should also be considered in evaluation of structural sediment
trapping measures, as should their aesthetic appearance and compatibility with their sur-
roundings.
i
fl
r
L
8.2 Recommended Actions
The City of Northampton should take action to lower the hydraulic grade line within the
King Street Brook Diversion in order to alleviate the flooding and the increasing surface and
ground water levels in the Barrett Street Marsh and its surrounding area. While it is possible
to lower the hydraulic grade line to the level of the Barrett Street weir, decreasing the water
levels by 12 -18" throughout the diversion channel would likely recreate the Barrett Street
Marsh hydrology as it was d adjacent wetland 1980s,
and aareas.Thefo following steps should be instituted
without overly draining the tut d
to achieve this goal.
Remove the accumulated debris and sediment in the area immediately downstream of the
bike trail culvert and adjacent to the Stop and Shop detention basin
Water levels here have increased over the last twenty years and have recently risen to
such levels that the efficacy of the Stop and Shop detention basin has been compromised.
Removal of the accumulated debris would immediately lower the water surface in this
area by approximately one foot and would improve flow through the 4'x4' box culvert
and alleviate the tailwater conditions on the Stop and Shop area. Access could be from
the bike trail embankment. The work would require the excavation and disposal of 500
700 cubic yards of sediment and organic debris.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 32 of 35
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Clean out the remaining of the King Street Brook Diversion
From the Barrett Street crossing to the bike trail, the diversion channel should be exca-
vated using one or more of the previously- described methods. Initial cleanings using
hand labor and resources could be undertaken to gauge the effectiveness of these methods
and to evaluate the need for more intrusive excavation activities. If the removal of the
snags and obstructions does not produce the desired lowering of the Barrett Street Marsh
water levels, a study should be undertaken to evaluate the optimum channel configura-
tion, the limits of excavation, and the preferred mechanical technique.
If the channel were completely excavated to the level of the Barrett Street weir, a possible
configuration would include the installation of a series of adjustable step weirs located at
intervals along the diversion channel. Regulation of the weirs would control the water
levels within the diversion channel and thus the ground water levels in adjacent areas.
Access to the weirs could be gained by a system of boardwalks or nature trails Annu-
ally, the weirs could all be fully lowered to allow the diversion channel to flow unencum-
bered during the wet season, allowing any accumulated sediments to pass downstream.
The access walks could be used as a means of egress into the marsh to monitor the water
levels and to evaluate the need for maintenance removal of accumulated snags or ob-
structions.
Whether the channel is excavated or not, sediment transport through the King Street Brook
Diversion will likely be an ongoing issue for the City. It is unlikely that the King Street
Brook Diversion sediment loading can be balanced with the channel's sediment transport ca-
pacity without instituting significant physical alterations to the channel geometry, similar to
the work completed downstream of Barrett Street. If sediment balance is not achieved, the
system will not be self maintaining, and intervention will be required to preserve the desired
hydrology in the area. The following actions will significantly reduce the sediment loading
and thus extend the effectiveness of the in- channel work.
Institute watershed management techniques aimed at reducing the sediment loading to the
Barrett Street Marsh
The simplest measure could be a reduction of the amount of winter road sand used within
the watershed. As a compliment to this effort, increasing the frequency of street sweep-
ings and catch basin cleanings would also serve to reduce sediment loadings.
Repair the storm drain outlet at Adare Place and establish an open -basin sediment trap
immediately below outlet
Repair of this 36" storm drain would significantly reduce erosion in this area and would
also serve to protect the rail trail embankment which could eventually be compromised
by the continued loss of soil materials. The scoured materials have traveled downstream,
with areas of significant deposition found near the Coachlight Apartments, where the
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 33 of 35
transported soils have been deposited choking the channel and leading-- to -a braided and
confused stream pattern. This area is well- vegetated and the bulk of the soils were pre-
sumably deposited years ago. It appears that the stream bed for first 400 feet of down-
stream of the drain outlet has eroded as much as three vertical feet since the time when
the drain was initially installed, which appears to have been in the period of 20 -30 years
prior to the time of observation. The stream gradient along this reach is now mild, the
bulk of erosion having already taken place.
Repairs to the storm drain outlet could include an open sedimentation basin to allow for
removal of sediments transported from the watershed. Access from the rail trail to peri-
odically remove the collected sediments would be straightforward and would consist of a
ramp to the pipe end. The sediment basin would also serve as a stilling pool for the ero-
sive flows which obviously can emanate from this storm drain. Sediment capacity of the
basin should be approximately 35 cubic yards which equates to twice the estimated an-
nual road sand loading for this particular portion of the Barrett Street Marsh watershed.
Conceptual dimensions of the basin are 25' x 15' with a total depth of three feet when
emptied of sediment.
Establish an open -basin sediment trap within the King Street Brook diversion channel
immediately below the bike trail embankment
Excavation of an open -water basin in this location would allow for removal of sediments
contributed by the vast majority of the watershed and would replace open water habitat
which may be disrupted if the water level in the channel is reduced. A sediment trap in
this location could be designed to function cooperatively with the Stop and Shop deten-
tion basin and would compliment its effectiveness. The land is already owned by the City
of Northampton and thus no takings would be required.
Access to the basin for regular maintenance and removal of sediments would be from the
bike trail, or possibly from an easement across the Stop and Shop lot. The basin could be
an attractive amenity to the area and would provide an area of open water habitat in close
proximity to the patrons of the bike trail. Sediment capacity of the basin should be ap-
proximately 120 cubic yards which equates to twice the estimated annual road sand
loading for this particular portion of the Barrett Street Marsh watershed. Conceptual di-
mensions of the basin are 50' x 20' with a total water depth of four feet when emptied of
sediment.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 34 of 35
8.3 Cost Estimates
The following estimates of costs for the conceptual action components are provided for
planning purposes. These are reflective of prevailing wage rates and the public bidding
process. Design and permitting are not included in the following costs. Backup data are
included in Appendix A.
Potential Corrective Actions, Channel Cleanout
Hand Excavation:
Mechanical Excavation,
Leave Castings:
Remove Castings
Hydraulic Excavation with Mechanical Dewatering:
Rotary Ditching:
Recommended Actions
Remove accumulated debris in area near Stop Shop:
Clean out diversion channel
Optional Step Weirs:
Optional Boardwalk:
Watershed management:
Sediment trap drain repair at Adare Place:
Sediment trap on King Street Brook Diversion:
5,000
10 15,000
25 30,000
60 75,000
15 20,000
15 20,000
see above
20 25,000
110 120,000
Departmental
30 35,000
65 70,000
Design and permitting costs would be best determined after a plan of action is developed.
For the smaller efforts, design and permitting could exceed 100% of the construction
costs. Design and permitting for the larger project components would likely be in the
20 25% range, depending on the technical and environmental complexity of the com-
bined project components.
Functional Analysis of the Hydrology and Hydraulics of Barrett Street Marsh
April, 2000
Page 35 of 35
Appendix A
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