Conservation Commission Meeting Agenda/Materials 109R and 131 Clark Lane Exhibit List (linked)

February 22, 2023
l (Dit f= TP)
Dear Conservation Commission | mul LY)
FEB 2 2 2023
| Planning & Development
Town of Wate for cl
'
The enclosed are documents in support of buffer zones the reports Carya Documents already submitted
on 01/26/23 and 02/09/23 and in support of oral testimony.
From: Sigrun Gadwa of Carya Ecological Services LLC
C-22-14
109R & 131 CLARK LANE
PUBLIC HEARING 01-26-23
EXHIBIT #60


THE SCIENTIFIC BASIS
FOR WETLAND & WATERCOURSE BUFFER ZONES
Prepared by Sigrun N. Gadwa, MS, PWS and George T. Logan, MS, PWS, CE
For The Berlin Land Trust,
Berlin, Connecticut
October 2006, Revised July & October 2011

The Scientific Basis for
Wetland and Watercourse Buffer Zones
THE SCIENTIFIC BASIS
TABLE OF CONTENTS
1.0 Introduction........
2.0 Buffer Functions
3.0 Determining Buffer Width: Pollutant Removal Mechanisms & Study Results
4.0 Resource Sensitivity and Buffer Needs...............:000064 es
4.1 Sensitivity of Aquatic Fauna and Flora to Toxins...
4.2 Variable Vulnerability to Sediment &Nutrients......
4.3 Comparing Nutrient Removal Efficiencies.........
4.4 Ecological Integrity and Productivity..........
4.5 Headwaters Wetlands............:ccccseeceeseeeeees
5.0 Toxin Movement & Degradation in Wetland buffers..............
SEL, PeSUCIIES visas. cssunsiewssanraainnaninnonmanaenes tyr eng nly ia sedeneeets
5.2 Septic Effluent... Mos
§)3) (CHOPNG xe sersenscxenie evs pel eetinn vcs asexe sense daamesers aes eeversim enna da Uae in tebe ange
6.0 Conclusion.... Ms
TE RTPI CS seascarectnccerentcearcerroetsoa tore 25019 eee eNO a Oe STO Te
1.0 INTRODUCTION
Buffer zones are natural or enhanced vegetated areas, upslope of a wetland or surface water
(i.e. ponds, lakes, streams, rivers). They are a land use management tool that can effectively
protect regulated resources from multiple “indirect” physical impacts associated with
Rema Ecological Services, LLC, July 2011 Page 2 of 23

’ The Scientific Basis for
Wetland and Watercourse Buffer Zones
development proposals,’ including hydrologic alterations, sedimentation, degradation by
excess nutrients and toxicants, and increases in light, temperature, and/or or ambient sound
levels.
Many scientific studies have been conducted on buffer performance, most focusing on a
particular narrow buffer function, such as removal of nitrogen or a particular pesticide. This
report cites such narrow studies, and also paints a broad picture. It explains how buffer zones
preserve and enhance the integrity of a wetland's or watercourse's water supply and quality.
Adjacent buffers also help maintain wetland vegetation structure and soil characteristics,
which are recognized physical wetland properties. Forested buffers, in particular, are an
important source of leaf litter, woody debris, and groundwater enriched with minerals (e.g.
calcium and magnesium) and dissolved organic matter (DOM). These buffer exports are all
key components of wetlands and stream ecosystems.
Buffers provide essential, complementary terrestrial habitat for many wildlife species that
forage and/or breed in wetlands and watercourses, that is, wetland-dependent and wetland-
associated species. Most widely known are the vernal pool species. Wood frogs and spotted
salamanders, two of the keystone species, are crucial players in the vernal pool and forest
food web, which is based on leaf litter, algae, and the assorted invertebrates that feed in forest
soil and vernal pools. Through the food chain, and the “production export”? wetland
function, wildlife is part of the physical cycling of carbon, nitrogen, phosphorus, etc., that
takes place in wetlands. However, if a buffer is severely degraded by invasive species and/or
other disturbance, certain buffer functions and/or values, such as wildlife support and
aesthetics, may be much diminished, while others remain intact (e.g. hydrologic and filtration
functions). Less-than-optimal buffer widths are often mitigated by buffer restoration and/or
enhancement, with the goal of a net gain in wetland functions and values.
2.0 BURFER FUNCTIONS
The functions of riparian and wetland buffer zones are succinctly described in the 1991
Policy Statement: Riparian Corridor Protection, issued by the Inland Fisheries Division of
1 Wetlands agencies in Connecticut must not make permitting decisions based on impacts to wildlife or plants,
unless accompanied by physical impacts to wetlands (2004 Amendment to the Wetlands Statute). The definition
of wetlands now inlcudes wildlife, vegetation, and habitat.
? “Production Export” is one of the thirteen functions and values of wetlands in the New England Army Corps
(USACOE) functional assessment methodology (1995). It includes the export of decaying vegetation from the
outlet stream of a marsh, and the export of biomass (includng carbon and nitrogen) from a wetland via the food
chain, in nectar, fruit, or decaying vegetation, or animal prey.
Rema Ecological Services, LLC, July 2011 Page 3 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
the Connecticut Department of Environmental Protection (CT DEP 1991). This document
recommends a 100-foot buffer to perennial streams, and a 50-foot buffer to intermittent
watercourses. These functions are also elucidated in the Guidelines: Upland Review Area
Regulations; Connecticut's Inland Wetlands & Watercourses Act, by the CT DEP’s Wetlands
Management Section (CT DEP 1997). A 100-foot upland review area (URA) is
recommended in this document. Avoiding degradation of water resources is also spelled out
as a guiding principal for environmental planning in Connecticut’s official Water Resources
Policy in Section 22a-380 of the Connecticut General Statutes.> The CT DEP OLISP (Office
of Long Island Sound Programs) Tidal Wetlands Buffer Guidance document (2003) also
describes buffer functions and calls for a 100-foot setback. It references am early version of
this present REMA document (i.e. 2003).
Buffer zones offer a variety of ecological and social functions.* The most widely recognized
functions are:
1. Hydrologic Effects, Surface runoff and groundwater discharge from buffer areas provide
water to wetland vegetation and aquatic life, as well as to overhanging trees and shrubs.°
Buffers maximize groundwater recharge and store groundwater. In a developed setting, they
infiltrate runoff from impervious surfaces and lawns. Forested buffers also reduce evaporation
by reducing sunlight penetration. Buffer zones moderate stressful, seasonal “low flows” in
streams and rivers; they also moderate flooding by intercepting rain and snow melt, and storing
flood waters that overflow stream banks, lakes and wetlands.
2. Support for the Wetland Ecological Community. Buffer zones provide foraging and nesting
habitat and cover for a variety of upland, aquatic and wetland species, including vernal pool
amphibians, and most of the larger predators, such as barred owls and red-shouldered
hawks. Well-vegetated buffer zones support wetland plant diversity. Minerotrophic plant
species® are supported by groundwater that is enriched with minerals as it flows through a
3 Sec, 22a-380. Water resources policy: The following are declared to be the goals and policies of the state: (1)
To preserve _and_protect_water supply watershed lands and prevent degradation of surface _water_and
groundwaters;...
The following section, and portions of other sections draws heavily on prior riparian and wetland buffer zone
publications and research by George Logan of Rema Ecological Services, LLC, Manchester, CT. Roy Schiff,
working for the Quinnipiac River Watershed Partnership and Quinnipiac River Watershed Association also
assembled many of the references.
5 Vegetation rooted in upland soil on the wetland perimeter, often overhangs the wetland and
contributes to wetland function.
® Herbaceous species of mineral-rich, slope-base landscape position include many of the spring ephemeral
wildflowers, such as red trillium, blue cohosh, dolls’ eyes (Actaea spp.) and the laxiflorae sedges. They are
especially prevalent in traprock and shale areas and include uncommon species such as leatherwood (Dirca
palustris). Distributions of this group of species typically include the outer portion of the wetland and the lower
portion of the adjacent upland buffer. As a group, minerotrophic herbaceous plant species are important to
wetland vegetation structure and nutrient cycling because of their their phenology (active growth in spring) and the
Rema Ecological Services, LLC, July 2011 Page 4 of 23

* The Scientific Basis for
Wetland and Watercourse Buffer Zones
buffer toward a wetland.’ Buffer vegetation moderates light, wind and humidity levels in
wetlands. Leaf litter blown in from nearby forested buffers is also a parent material for
wetland organic soils. Buffers can also serve as travel routes for migratory and nomadic, as
well as for resident wildlife species. In Connecticut, river corridors are essential for the spring
bird migration. Large diameter trees and tall trees for platform nests are important buffer
habitat features for raptors, larger mammals, and bats.
3. Shade. In a developed setting, forested buffers help maintain cool stream temperatures and
wooded swamp vegetation by casting shade. Shade also prevents colonization of wetlands by
invasive plant species and leaf litter protects the soil.
4. Protection from harmful runoff and leachate constituents. Sediment, phosphorus, nitrogen,
herbicides, and insecticides can all be at least partly removed from runoff and leachate passing
through naturally vegetated setback zones. Through biological, chemical and physical
processes, setbacks can filter, transform and store significant quantities of pollutants carried by
surface runoff. These processes are more effective when runoff is spread out as sheet flow, than
when it is channelized. Forested buffers also contribute to neutralization of acid precipitation,
due to ion exchange that occurs as precipitation filters through the forest canopy. The
percentage of pollutant reduction depends on the pollutant load, nature of the material, amount
of runoff, extent of dilution by groundwater, and the character of the buffer area. Klapproth
and Johnson (2000) have compiled an excellent review of the science behind the water quality
renovation function of buffers.
5. Ecological Integrity. A well-buffered wetland with a range of different predators (e.g.
insectivorous songbirds, amphibians, bats, hawks, owls, otters, mink) has a more complex and
stable foodweb, and a more complex nitrogen and carbon cycle than a wetland with minimal
adjacent upland habitat.*.? Predators control population levels of mosquitoes, and also control
herbivores such as voles, rabbits, and foliage insects.'!° Buffers protect wildlife and aquatic
organisms from adverse physical changes to their environment (altered noise and light levels)
by screening excess illumination and noise. Dense plantings can enhance the screening
fact that most are perennials with underground storage organs, a winter food source for herbivores. They also
have high aesthetic value.
TM The extent to which soil minerals are released into groundwater and infiltrating precipitation depends on the type
of parent soil material (Gradey and Mullaney, USGS,1998) and the duration of contact time. Higher mineral
content (reflected in specific conductivity) was found to be associated with higher plant diversity in a study of
wetlands in St. Lawrence County, New York (1994). This is consistent with the widely accepted pattern of diverse,
slope-base plant communities in mineral-rich soils on wetland margins. A substantial buffer with intact soils is
needed to enrich seepage groundwater.
Sitisa widely accepted ecological principal that with more and different predators, more prey species can coexist,
applicable in ecosystems as different as coral reefs and vernal pools.
°’A shortage of predators may have undesirable public health ramifications, e.g., excessive densities of
mosquitoes, tick-carrying white-footed mice, or an outbreak of a foliage insect.
10 Because herbivory significantly impacts vegetation structure and composition (Howe and Lane 2004), wetland
function improves, if the wetland supports predator populations.
Rema Ecological Services, LLC, July 2011 Page 5 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
function of buffers, a form of mitigation, compensating for sub-optimal buffer width.
Scientific research has shown that buffer zones are an integral component of the landscape and
can protect significant wetland and watercourse functions (Chase et al. 1995, Castelle et al.
1992, Welch 1991, Brown et al. 1987).
3.0 DETERMINATION OF BUFFER WIDTH:
POLLUTANT REMOVAL MECHANISMS AND STUDY RESULTS
The width of wetland/watercourse buffer zone needed to prevent significant adverse
impacts to the wetland and/or watercourse is related to three factors: (1) the intrinsic
properties of the buffer zone and setbacks (e.g. habitat quality, steepness, soil
permeability, depth to water table, and vegetation density (Brinson 1993); (2) the intensity
of the development, and (3) the sensitivity of the receiving wetland or watercourses.
As runoff moves across a naturally vegetated buffer as sheet flow or as shallow groundwater,
it gradually infiltrates into the soil, sediment is filtered, and nutrients are utilized by
vegetation or converted into nitrogen gas by denitrification. Processes such as volatilization,
photo-degradation, biodegradation, bio-uptake, and adsorption work to break down or
reduce toxicity of potential pollutants found in runoff (Hemmond and Fechner, 1994;
Klapproth et al, 2000), operating more effectively in natural soils with high organic matter
content and microbial activity.
Dilution by groundwater is also important. Hemmond and Fechner emphasize the importance
of the duration of travel time, in determining how much toxin actually reaches a sensitive
wetland community or a sensitive receiving water body. A longer travel time provides more
opportunity for these various processes to eliminate pollutants or make them less harmful.
Research has shown the importance of deep roots of woody plants, in extraction of nitrates
and other constituents from shallow groundwater in subsoil (Hefting and Klein, 1998 and
Correl 1997). These constituents are incorporated into wood and also leaf litter, which is
eventually incorporated into surface soil horizons where denitrification and other breakdown
processes are much more active than in the subsoil.
Travel time is a function of setback distance, moderated by factors such as slope, soil
infiltration capability and permeability, water storage capacity, and vegetative cover. A
Stormwater runoff that has passed through and treated by a treatment train of a stormwater management
system still contains suspended fine sediment that is effectively polished by sheet flow over permeable buffer soils.
Rema Ecological Services, LLC, July 2011 Page 6 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
number of independent investigators have reviewed the technical literature [e.g., Diamond &
Nilson (RGH, Inc), 1988; Schueler, 1995, Welch, 1991] and have concluded that a minimum
of 75 feet to 100 feet to the sensitive receiving wetland and/or watercourse is needed for
water quality renovation; larger distances are needed if soils are very pervious (sandy) or
shallow, or if slopes are steep. A guidance document produced by the NRCS-USDA (March
2000) also recommends buffer widths of at least 100 feet for removal of soluble pollutants
such as soluble triazine herbicides. This document points out that “It takes more surface
area and longer flow paths to adsorb and infiltrate soluble material than to entrap solid
material. Climate conditions and storm events... influence the effectiveness of the buffer to
retard flow and remove pollutants.”
A guidance document produced by the USDA Forest Service, Riparian Forest Buffers,
Function and Design for Protection and Enhancement of Water Resources (NA PR 0791)
recommends streamside buffers ranging from 75 feet to 150 feet in width depending on soil
capability classes. This document emphasizes that certain uses such as trails and selective
logging may be compatible with buffer effectiveness, with stricter restriction needed in the
zone closest to a stream.
Diamond (1988) and Tom Schueler (1995) (among others) recommend adjusting wetland
buffer width based on slope steepness. Various formulas have been devised. One frequent
element is to subtract the sections with slopes steeper than a certain threshold (e.g. 15%),
when calculating buffer widths for regulatory purposes. Steep slopes exacerbate the natural
tendency of flows to concentrate, converging into larger and larger channels, which erode rills
and gullies, becoming a sediment source rather than a sediment filter.
A buffer review paper by Barling and Moore (1994) also emphasizes that the pollutant
removal capacity of a given buffer width varies with site conditions. Barling and Moore cite
a study by Philips (1989) of the distances needed to remove nitrate in agricultural runoff,
finding that fifty meters (150 feet) was not wide enough in some cases, but 15 meters (45
feet) was sufficient under other site conditions. Hefting and Klein (1998) found greater
nitrate removal by forested than non-forested buffer zones. In the absence of detailed
investigations of buffer characteristics, a conservative buffer width — at least 100 feet - is
desirable. Of course, the types and concentrations of nutrients and toxicants to be treated or
diluted also influenced the setback width needed. Note that nitrogen and phosphorus levels in
groundwater discharging from forested buffers — and in streams and wetlands with
undeveloped watersheds — are very low, typically under 0.2 micrograms/liter for total
Rema Ecological Services, LLC, July 2011 Page 7 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
phosphorus and under 1.5 milligrams/liter for nitrate-nitrogen, based on an extensive data set
developed by USEPA.
4.0 RESOURCE SENSITIVITY AND BUFFER NEEDS
Several characteristics of waterbodies and wetlands make them more sensitive to human
disturbance, and increase the need for generous setbacks. This is especially so, if these are
high-functioning wetlands or support valuable and/or unique ecological communities.
41 Sensitivity of Aquatic Fauna and Flora to Toxins
Numerous studies have shown close correlation between stream health as measured by
biotic indices (measuring the diversity and composition of aquatic invertebrate
communities) and the percent of developed land in its watershed. A recent major study by
Morley et al (2002) is set in the Portland area. Healthy, diverse, aquatic communities with
pollution-intolerant macroinvertebrate organisms such as stoneflies, mayflies, and case-
bearing caddisflies are an important food source for trout and are very sensitive even to
relatively low concentrations of stormwater pollutants, especially PAHs (Polyaromatic
hydrocarbons and heavy metals). The classic study by Plafkin (1989) classified stream
organisms based on sensitivity to stream pollution, and is still the basis for the USEPA
Stream Bioassessment methodology. In Connecticut the CT DEP Pesticide Division has
been studying the effects of toxic organophosphate insecticides on stream insects. Vernal
pool breeding amphibians, such as the mole salamanders and wood frogs are also known
to be intolerant of water pollution, more so than amphibians of permanent ponds, such as
green frogs and bullfrogs.
Toxicity screening has shown that widely used landscaping and agricultural pesticides and
partially degraded toxic compounds will adversely impact wetland plants’, fungi,
pollinators", soil invertebrates, and frogs", both individually and via foodweb
alterations. One hundred (100) foot setbacks between wetlands and areas of pesticide
application are recommended in several federal guidance documents, and on the labels of
® Seed germination and seedling development in many plant species is inhibited by hydrocarbon breakdown
products. Runoff containing glyphosate, the widely used and highly souble herbicide in RoundUp, may cause
marsh vegetation kills. The authors have observed this personally in a wetland downgradient of an Ellington utility
corridor.
*3 Neonicotinoid insecticides (widespread lawn and farm pesticides) are neurotoxins that disorient honeybees and
other insects, at low concentrations (less than 30 ppb) - sublethal adverse impacts.
"4 Atrazine, a widely used farm herbicide, is an endocrine disrupter of frogs, at very low concentrations (less than
20 ppb based on studies with leopard frog and other frog species.
Rema Ecological Services, LLC, July 2011 Page 8 of 23

’ The Scientific Basis for
Wetland and Watercourse Buffer Zones
many individual pesticide products, used for landscaping as well as farming,'* Note that
pesticide labels calling for wide setbacks to wetlands are often ignored, especially if
thickets visually obscure the nearby wetland; this is less of a problem if an ecologically
conservative Integrated Pest Management (IPM) program is in place.
Toxins may reach wetlands and streams via shallow groundwater flows, via drift, or via
surface runoff. Indirect adverse impacts occur through consumption of contaminated
worms and other soil invertebrates, or a diminished prey supply. Headwaters streams and
wetlands with little throughflow are most vulnerable to toxins. Flushing and dilution of
pollutants is minimal in still pools and slow-moving channels, and low water volumes.
Roadway pollutants such as polycyclic aromatic hydrocarbons (PAHs) tend to build up in
these areas. Periods of low dissolved oxygen (DO) may heighten the biological impact of
toxic pollutants such as heavy metals by bringing them into solution.
Generous setbacks between wetlands and stormwater outfalls, lawns or farm fields protect
sensitive wetland organisms. They also prevent incidental harm because pollinators, birds,
and other larger wetland creatures often wander into treated upland areas near wetlands.
A wetland buffer of at least 100 feet is especially important where the resource has been
designated a critical habitat or is known to have exceptional functional value.
4.2 Variable Vulnerability to Sediment &Nutrients, for Different Wetland Types
Wetland and stream sensitivities to sediment and nutrients vary widely. Nutrient and
sediment sources include partly treated stormwater runoff, excess fertilizers from farm
fields and lawns, .and partly treated septic leachate!® in shallow groundwater flow.
Less vulnerable wetland types include emergent marshes and wet meadows, and also
floodplains of larger streams and rivers, which already have a relatively high nutrient
status, and are subject to natural sediment deposition. The majority of wetland types are
somewhat vulnerable to nutrient and sediment inputs.
‘5 400-foot buffers are recommended in Conservation Buffers to Reduce Pesticide Losses and the USDA March
2000 and the US District Court (Coughgenour) pesticide buffer ruling 1/27/2004.
‘8 See further discussion in Sections 4.3 and 5.2 of this report, explaining how a fully compliant, per CT Heath
Code, septic system can still pose a singificant threat to the water quality of certain streams and wetlands.
Rema Ecological Services, LLC, July 2011 Page 9 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
Some types of wetlands are highly sensitive. The unusual plant communities and wetland
soils in oligotrophic (low nutrient) wetlands such as bogs, fens, and headwaters seeps will
be irreversibly degraded by nutrients in sediment and partially treated stormwater runoff,
especially phosphorus. These wetland types are often valuable, due to high functions
and/or values. Some headwaters ecological communities, like bogs, are uncommon in the
Connecticut landscape.
In mesotrophic (moderate nutrient status) ponds and lakes, excessive nutrient inputs
typically cause algal growth and eutrophication. If buffers are inadequate, they also cause
adverse changes to mesotrophic wooded swamps; the cinnamon fern - high bush blueberry-
red maple community; organic and mossy substrates in wetlands; and populations of
perennial wildflowers or ferns are all significantly altered by deposition of sediment, and
changing hydrology and nutrient status. Sediment deposits in wetlands form a seedbed for
weedy, annual, nutrient-demanding colonizers like jewelweed and invasive plants such as
Phragmites (i.e. common reed) and purple loosestrife, and may eliminate rare and
uncommon species. A wetland’s physical structure is altered when non-persistent,
nutrient-loving annuals like false nettle and jewelweed become dominant rather than ferns
and sedge tussocks, which provide year-round cover.
Benthic (stream-bottom) macroinvertebrate communities are highly sensitive. Sediment
deposits on gravelly or cobbly substrate or woody debris smothers gravelly fish-spawning
habitat and habitat used by stream-bottom invertebrates: crevices, stones, twigs, and leaf
litter. It may degrade habitat needed by rare state-listed species such as wood turtles and
certain freshwater mussels (e.g., eastern pearly shell). Suspended sediment abrades the
gills of fish, being most harmful to juveniles, and clogs the gills of certain sensitive
macroinvertebrates (e.g. case bearing caddisflies, stoneflies, and mayflies). Sediment and
algal proliferation (triggered by excess nutrients) also smothers key aquatic food sources:
decomposing leaves and microscopic plants (diatoms). Nutrient-stimulated green algae
proliferate at the expense of diatoms.'’ Large, slow-flowing streams or rivers with
naturally sandy bottoms are less vulnerable than smaller, rocky streams. Larger
watercourses are better able dilute turbid water (or other pollutants) that may reach them.
4.3 Comparing Nutrient Removal Efficiencies
‘7 The multiple adverse impacts of sediment on aquatic habitat are thoroughly covered in Impacts of Suspended
and Deposited Sediment by Wood amd Armitage (1997) and Crowe (2004). Periphyton is the scientific term for
the thin film of microscopic plants that coats the substrate of a healthy stream, and is a major food supply.
Rema Ecological Services, LLC, July 2011 Page 10 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
A supplemental buffer is usually needed to protect wetlands from nutrients and sediment
because other best management practices BMP’s) are not sufficient. This generalization
applies to septic systems, stormwater basins/treatment trains, perimeter silt fence, and
perimeter silt socks.
Properly functioning septic systems remove only 40-50% of the nitrogen that enters the
system, though they do filter most of the phosphorus. With a 100-foot buffer, the roots of
trees and shrubs, and dilution by groundwater will substantially reduce nitrate
concentrations reaching the wetland." Similarly, correctly designed stormwater
management system will still discharge a substantial percentage of the nutrients that enter
the system. Large data sets on performance of water quality basins (e.g. EPA NURP data,
UNH-SC 2010'°) show that average phosphorus and nitrogen removal rates in excess of
80% are rare, and expensive to achieve, and 40-60% removal is common.
None of the alternative, sophisticated erosion and sediment or stormwater management
control practices match natural wetland buffers as a sediment filtering tool. Tom Schueler
principal scientist at the Center for Watershed Protection (1995) focused on sediment
removal, in formulating his recommendation of an 80-foot minimum buffer.
Regardless of how well sediment barriers are installed, fine sediment (fine sand or finer)
passes through the mesh of silt fence or between hay strands in hay bales; these perimeter
controls are not complete sediment barriers. In fact they depend on through-flow to
function.”” The 2002 CT DEP Erosion and Sedimentation Guidelines specify only 75%
removal efficiency for geotextile silt fencing. This is less of an issue for a large
construction site that depends primarily on earthen berms, rather than barrier fencing.
Compost berms (silt socks) can remove a high percentage of sediment. However, they
release dissolved phosphorus unless specialized additives are inserted into the medium, at
additional cost (rarely done). Long-term, a narrow setback behind a compost tube will also
be unable to perform multiple other buffer functions post-construction (see Section 3.0).
18 To accurately model the setback needed from the septic leachfield to the wetland, use the latest CTDEP Dilution
model (2003), which takes soil type and watershed area into consideration. It is usually used for community septic
systems but is applicable to any setting, per CTDEP staff. Also consider resource senstivity.
18 UNH-SC, 2010. University of New Hampshire Stormwater Center. 2009 Biannual Report.
29 The mesh size in AMOCO silt fence (when stretched by water under pressure) according to specifications
provided by the vendor is between 850 and 710 microns, the size of a medium to coarse sand grain particle.
Rema Ecological Services, LLC, July 2011 Page 11 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
By contrast, overland sheet flow through a forested wetland buffer, over forest leaf litter or
through meadow vegetation, will achieve nearly complete sediment filtration and nutrient
uptake, if the buffer is over 80 feet wide with a gentle to moderate slope, and flow volumes
are low and dispersed. Groundwater discharge into the wetland will contain minerals and
dissolved organic matter. Especially where proposed grading is extensive, with steep cut
slopes, buffers are an important supplementary best management practice (BMP). If the
project includes on-site sewage disposal, excess nitrogen in septic effluent will also be
removed. Dissolved phosphorus in lawn runoff will be removed by a buffer with a
minimum width of roughly 50 feet”! (Woodard and Rock, 1995”), provided the wetland or
watercourse is not oligotrophic already (i.e. low nutrient) and, therefore, more sensitive
than most other resources.
44 Ecological Integrity and Productivity
Leaving a vegetated buffer increases the likelihood that disturbance- or area-sensitive
wildlife will remain in a wetland, as a part of the food web, adding to the wetland’s overall
function. Many wildlife species of wetlands and stream corridors, such as wood duck,
green heron, barred owl, and veery, are sensitive to human disturbance and/or have
specific habitat area requirements. Buffer vegetation also absorbs sound, enhancing avian
habitat quality and wetland value for human users. A study by Reijnen and Foppen
(1997) showed significantly decreased bird density and diversity closer to major highway
noise sources, with measurable impacts extending out as far as 300 feet. Longcore and
Rich (2004) recently reviewed the available research, and found multiple studies showing
disruption of predator-prey relationships and foraging behavior by elevated light
levels. An approximately 100 foot wide buffer has been found to be sufficient for
general avian use, although wider setback needs (over 300 feet) were demonstrated for
forest interior birds (Milligan, D.A, 1985), such as veery, a wetland-dependent species.
Wetland/watercourse buffers widths of 96 to 117 feet encompass home ranges of 12 New
England mammals (DeGraaf, et al. 1987).
71 In this study a 15 meter buffer strip was adequate to return total phosphorus levels to background levels (i.e.,
<1.5 mg/l).
aa Wossword S.E., and C.A. Rock. 1995. Control of Residential Stormwater by Natural Buffer Strips. Lake and
Reservoir Management. 11(1):37-35. ,
23 Light inhibited foraging by smaller nocturnal wildlife species (e.g. small mammals, amphibians, and slow-flying
bats). Similarly, one study showed that fewer zooplankton migrated to the water surface at night to feed on algae
under well-lit conditions, a behavior presumably related to avoidance of fish predation. Night lighting inhibited
reproductive behavior in frogs.
Rema Ecological Services, LLC, July 2011 Page 12 of 23

’ The Scientific Basis for
Wetland and Watercourse Buffer Zones
The wildlife habitat value of a buffer, in terms of ecosystem productivityTM, is affected by
the width of the zone adjacent to the wetland with high humidy and dense vegetation. The
high insect densities and thick vegetation in wetlands and in moist upland buffers make
them less desirable for human residential use, but very valuable for wildife, more so than
typical well-drained upland oak forest. A large scale study in Massachusetts of bird
distribution in relation to habitat components (Swift et al. 1983) demonstrated signficantly
higher bird densities within and adjacent to forested wetlands, than in well-drained upland
forest, even for faculative birds that use both uplands and wetlands. Densities of treefrog,
woodfrog, bats, shrews, and predaceous invertebrates are also assumed to be higher, than
in well-drained upland habitat. The larger combined area of a wetland and its adjacent
moist upland buffer can support more wetland-associated wildlife, than a wetland closely
flanked by development.
Because mosquitoes are intolerant of dry air, they are active in humid, low-lying upland
buffer habitat, in the vicinity of wetlands with standing water, but not in drier upland
buffer areas. Because high mosquito densities may be associated with health concerns,
pesticide application is more likely, with potential adverse impacts on aquatic habitat,
when homes are built in moist, low-elevation, upland areas, near wetlands. In a nutshell,
generous wetland and watercourse buffers provide a margin of safety for public health —
and protect the wetlands from pesticides. Note that if the wetland or stream is bordered by
well-drained uplands, these particular concerns regarding health and quality-of-life are
reduced, for a setback less than 100 feet wide.
4.5 Headwaters Wetlands
Generous protective buffers are especially important for low order streams and headwater
wetlands. Mark Brinson emphasized the vulnerability of headwater wetlands in his 1993
landmark paper. He pointed out that a given area of adjacent soil disturbance would affect
lower order, headwaters streams proportionately more than large, higher order streams.
Biodiversity, including rare species, is especially high in headwaters seeps and streams
(Meyer et al 2003). Because significant denitrification takes place in the microbe-rich
substrate of healthy streams and stream banks, maintaining the integrity of lower order
24 The carrying capacity of the habitat unit (wetland and adjacent moist buffer) is the total number of songbirds,
insectivorous amphibians and bats and other small mammals that it supports. A wide body of research has shown
that larger populations of plants and animals are genetically healthier (more genetic diversity and less prone to
inbreeding depression, infertility, and loss of alleles from genetic drift). If buffer habitat is moist enough to support
wetland-associated species, the wetland ecosystem benefits from the larger population sizes, and greater
production export.
Rema Ecological Services, LLC, July 2011 Page 13 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
streams has a significant role in protecting downgradient waterbodies, including Long Island
Sound from excess nitrogen inputs (Meyer et al. 1997).
Buffer areas and level spreaders between stormwater outfalls and streams help reduce
concentrations of roadway pollutants, but headwaters open space preserves and “soft”
drainage systems (without catchbasins and stormdrains) provide the best protection for
headwater streams. Note that headwaters streams in urbanized watershed may already be
so degraded that their value and functional level is low, reducing the impact of activities
within buffers, although downstream impacts remain an issue.
5.0 TOXINMOVEMENT AND DEGRADATION IN WETLAND BUFFERS
5.1 Pesticides
The NRCS-USDA document, Conservation Buffers to Reduce Pesticide Losses (March 2000),
recommends a 100-foot setback from farm fields to streams, as noted in Section 3.1 (Footnote
15)°. The stated rationale is to allow sufficient dilution and degradation, on average, to
protect aquatic resources. This paper also emphasizes the need to protect intermittent streams,
pointing out that smaller streams combine to provide the water source for perennial streams
with fish populations — the watershed perspective. The impacts to wetland biota of toxins such
as pesticides and PAHs have already been discussed in Section 4.1. This section provides
more detail in support of the buffer needs to protect wetland resources.
Because soluble pollutants move readily through saturated soil, it is important that setback
distances be measured from the wetland boundary, not the bank of the watercourse. In
evaluating a proposed setback to regulated activities, the perennial question is as follows:
Will fertilizers and pesticides from the lawn or farm field reach the downgradient aquatic
resources in sufficient concentrations to harm aquatic organisms or plants? Will they harm
invertebrates in wetland soils? Sub-lethal effects of neurotoxins should also be considered.
Although highly persistent organochlorine pesticides (e.g. DDT) are no longer available in
the USA, numerous products are still in use with high aquatic toxicity, rapid mobility in
soil, high solubility in runoff, and/or long persistence (half lives over 60 days). Even
pesticides with a “rapid” breakdown rating have half-lives of several days to a week.
Based on their physical properties, several commonly used turf chemicals can be expected
to pass too rapidly through narrow setbacks, for breakdown to occur. For example, the
25 available on the internet from the USDA web site
Rema Ecological Services, LLC, July 2011 Page 14 of 23

' The Scientific Basis for
Wetland and Watercourse Buffer Zones
time needed for 75% to 100% breakdown of the herbicide 2,4-D is four weeks. The
popular, soluble grub pesticide Imidacloprid (Merit), linked to honeybee decline, takes 48
to 190 days to break down. A study evaluating herbicide removal by a 20-meter (i.e. 66-
foot) wide grassed buffer strip under natural rainfall, showed reduction of Atrazine by only
9% to 12%, of Metolachlor by 15% to 27%, and of Cyanazine by 7% to 21% (Arora et al.
1993). Moreover, initial breakdown products of pesticides and herbicides may still be
toxic if the biologically active functional groups are still intact”®.
In assessing the need for buffers to attenuate pesticides, consider the intensity of the threat:
total upgradient areas of lawn, fairway, or farm field; anticipated rates of application; whether
an Integrated Pest Management Plan will be in place; soil permeability, and the details of that
plan. A highly conservative IPM plans might make substantial use of cultural practices and
choose pest control products with minimal impacts to non-target organisms (Carlisle 2006).
With a small project, land use commissions simply cannot enforce permit stipulations that
restrict fertilizer or pesticide use, e.g. allowing only products with low aquatic toxicity or low
mobility in soil. Product-based regulation is not practical, due to the number of available
products. Pesticide monitoring (enforcement of IPM plans) by a golf course or a planned
community is hampered by the large number of chemicals & breakdown products requiring
different assay techniques. The solution, however, is fairly straightforward: the provision of
generous buffer zones to wetlands and watercourses, based on the scientific literature and the
best site-specific information available.
5.2 Septic Effluent
As noted in Section 4.3, properly functioning septic systems unavoidably release effluent
with high concentrations of soluble nitrate. When permitting any site plan with a septic
system upgradient of a wetland, a question to be asked is whether distance will be
sufficient to adequately dilute nutrients in septic leachate? Many officials are unaware that
the existing standards determining septic system placement (50 foot setback to waterbodies
and 10 mg/L nitrate per liter in groundwater leaving the site) are based solely on human
health criteria.
The CTDEP is in the process of developing a new set of criteria based on ecological
considerations, under a directive from USEPA (2000). Draft EPA nutrient standards for
6 Judy Singer, CTDEP Pesticide Division, personal communication, December 2000.
Rema Ecological Services, LLC, July 2011 Page 15 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
Ecoregion 1V, which includes Connecticut, are based on levels in non-impaired streams:
total phosphorus — 31.25 g/l, and total nitrogen — 0.71 mg/l. Although nitrate-nitrogen is
soluble in groundwater, substantial plant uptake, denitrification, and dilution can be
expected to occur in a watercourse buffer, particularly if it has a high proportion of
moderately well drained soils and an intact topsoil layer with at least a moderate amount of
organic carbon (e.g. 4-5% or more).
As discussed above in Section 4.2, the ecological communities in bogs, fens, and
headwater seeps and streams are all vulnerable to nutrient pollution, far more so than
cattail emergent marshes and hayfield wet meadows, although there is a lack of available
data on the exact thresholds of nutrient inputs that cause degradation of different types of
wetlands. Dilution and diffusion — within wetland setbacks - are relied upon to bring
nitrogen concentrations in septic system leachate down to levels that do not present a
human health risk. Wider setbacks to septic systems than mandated by the Connecticut
health code (e.g. at least 100 feet to wetland boundaries) are typically needed to maintain
concentrations in receiving water bodies that are close to the USEPA draft standards.
Large nutrient inputs into lakes and ponds, as well as the Long Island Sound, usually
triggers adverse impacts via eutrophication/hypoxia.
5.3 Chlorine
If an above ground pool were emptied prematurely in the fall, would chlorine reach the
resource? Chlorine is highly toxic to aquatic life at extremely low concentrations; the acute
toxicity standard is 19 ppb (i.e. parts per billion) and the chronic toxicity standard is 11 ppb.
Generous buffers in residential areas prevent the accidental release from swimming pools into
wetlands and watercourses.
5.4 Fertilizers
Severe eutrophication often occurs in watercourses receiving lawn runoff, especially from
up-scale residential neighborhoods. Excessive nutrient inputs can also dramatically change
the composition of a natural wetland plant community, as discussed above. Releases of
lawn chemicals vary widely, depending on the practices of the individual homeowner or
lawn care service. Several no-phosphorus and low-phosphorus fertilizers are produced, but
are not readily available in the retail market, or often selected. Unfortunately, lawn care
services may profit from applying fertilizers, pesticides, and herbicides more often and
Rema Ecological Services, LLC, July 2011 Page 16 of 23

' The Scientific Basis for
Wetland and Watercourse Buffer Zones
more heavily than necessary. However, naturally vegetated buffers are very effective at
preventing excess nutrients from reaching watercourses, ponds, and lakes.
Rates of nitrate removal are a primary consideration for the approximately 100 foot
wetland and watercourse setback recommendations by USDA and other researches
discussed above. Since nitrate is highly soluble and does not adsorb to soil particles,
generous setbacks are necessary, especially in areas with sandy outwash soils, to allow for
sufficient dilution, such that groundwater—fed streams and ponds will not be impaired.
Septic system spacing, per the Public Health Code, is intended to allow sufficient dilution
to keep nitrate levels in the water table (and wells) at safe levels. Reduction of nitrate
inputs into watercourses is a high priority for CT DEP because nitrogen has been identified
as the primary cause of Long Island Sound’s serious water quality problems.
Dissolved phosphorus is effectively removed by adsorption to soil particles in naturally
vegetated buffer areas, with low available phosphorus levels, provided soils are suited to
infiltration, and loading rates are not excessive (e.g. from a farm field), such that the soils
in the buffer become saturated with phosphorus. This is a key buffer function because
phosphorus is a major cause of algal blooms in ponds and impoundments of streams and
rivers. Phosphorus also degrades wetlands with low to moderate natural nutrient levels.
Because surface soils of most lawns are saturated with phosphorus, sheet runoff across
lawns picks up significant concentrations of dissolved phosphorus, often sufficient to
impair water quality if discharged directly into a watercourse or drainage ditch.
Decomposing wood chip mulch and compost-filled silt sock sedimentation barriers also
release phosphorus.
6.0 CONCLUSION
In summary, based on the scientific literature, a minimum 100 - foot wide upland review
area (URA) is prudent, from a regulatory perspective. However, the width of buffer needed
to protect and maintain the functions of a particular wetland and/or watercourse depends on
three principal, site-specific factors: (1) the sensitivity and functional value of the resource;
(2) the intensity of the proposed activity; and (3) the characteristics of the proposed buffer or
setback, including its effectiveness at attenuating or buffering anticipated impacts, and its
habitat value to the adjacent wetland ecosystem.
Examples of highly sensitive resources needing wider setbacks are a nutrient-sensitive bog or
fen, a perennial headwaters seep, a productive vernal pool wetland, and a wildlife sanctuary;
Rema Ecological Services, LLC, July 2011 Page 17 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
the New Jersey buffer determination method (Diamond and Nilson 1988) recommends 300-
foot setbacks adjacent to valuable nature sanctuaries. An example of a low-sensitivity
resource would be an urban stream that briefly daylights in a vacant lot, or a small, isolated,
fertile wetland surrounded by active agriculture.
Although the scientific literature supports a setback of 80 to 100 feet to protect wetland
resources, there are exceptions. The effectiveness of a particular setback area generally
depends on soils, slope, and vegetation properties; buffer areas with very steep slopes,
shallow ledge or hardpan, highly erodible soils, and/or a sparse groundcover and litter have
impaired effectiveness, so that wider setbacks are needed to protect the downgradient
resources. The significance of loss of a given buffer area also depends on its intrinsic habitat
and wildlife value to adjacent wildlife and vegetation. Adverse impacts from development
somewhat closer than 100 fect from a regulated resource are less significant, if buffer habitat
in the buffer area to be lost is degraded.
Each application before a municipal Inland Wetlands and Watercourses Agency (IWWA)
must be considered on a site-specific basis, considering the three aforementioned factors:
buffer quality, activity intensity (both short-term and long-term), and resource sensitivity and
value. For example, impact to the resource from the proposed parking lot of a self-storage
facility with a 40-foot buffer to a seasonal drainage swale, may be lower than impacts from
the proposed parking lot of a busy supermarket with a 100-foot buffer to a natural stream
corridor. This is because of the low sensitivity and value of the first receiving resource, and
because the supermarket is a much higher intensity land use, generating higher concentrations
of roadway pollutants and with a greater proportion of impervious surface in the wetland
watershed, as well as higher noise and illumination levels. Additional protective measures
will be needed for the supermarket application. The adverse impacts from a long, narrow
private driveway (20 foot cleared swath and a 25-foot buffer to the wetland), passing through
invasives-infested habitat at the edge of a large wetland system, would be low: 1) due to low
buffer quality, 2) because the wetland is not being fragmented, and 3) due to the low intensity
of the proposed activity. The formal New Jersey (Diamond and Nilson) buffer determination
methodology (1988) explicitly requires wider buffers, for more intense landuses.
Buffer width determination methodologies, such as those of Diamond and Nilson (1988) and
Pawlak and Logan (1995) (a.k.a., The Town of Cromwell Wetland Buffer Zone Designation
Methodology) depend on data that document wetland sensitivity, buffer habitat quality, and
the filtering/screening capacity of a given wetland setback. In the absence of detailed
baseline information on wetland and buffer resources that would justify a narrower buffer in a
Rema Ecological Services, LLC, July 2011 Page 18 of 23

’ The Scientific Basis for
Wetland and Watercourse Buffer Zones
particular area, the scientific literature supports site plans with buffers of at least 80 to 100
feet.
Authors’ Note: We consider this to be a “living document,” that is, a document that will
periodically be revised and updated as the relevant science base and understanding increases.
Acknowledgement: The original version of this document was produced for the Quinnipiac
River Watershed Association (QRWA 2001)
Rema Ecological Services, LLC, July 2011 Page 19 of 23

The Scientific Basis for
Wetland and Watercourse Buffer Zones
7.0 REFERENCES
Allan, J. David. 1995. Stream Ecology: Structure and Function of Running Waters. Chapm,an & Hall,
London. 388 pp.
Arora, K., J.L. Baker, S.K. Mickelson, and D.P.