P R O T E C T I N G WAT E R Q U A L I T Y THROUGH BETTER SITE DESIGN A handbook for stormwater management in the Mid-Hudson Valley
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CASE STUDY
Conserve Natural Buffers & Open Land
Minimize Impervious Surfaces
Treat All Stormwater Runoff On Site
Reduce Erosion & Sedimentation
Kingston, New York
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Written and Illustrated by Danielle Allen and Ian Warner JUNE 2006 Conway School of Landscape Design Scenic Hudson
Limestone bedrock of the Helderberg Escarpment—Albany County, New York
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HE GREAT BEAUTY AND WONDER of the Hudson Valley has inspired Americans for centuries. From blue crabs in tidal shores to bobcats on forested peaks, the Hudson Valley hosts remarkable diversity. This unique landscape has been shaped in part by its underlying geology, a band of limestone bedrock that runs north-south, generally parallel to the Hudson River from Albany to northern New Jersey. The high calcium content of these shallow limestone soils supports very specialized plant communities and their associated wildlife species. This limestone bedrock also made the Mid-Hudson Valley attractive for mining and related industries. For decades, all along the Hudson River, limestone was extracted to make cement. Many of these resources have now been exhausted and quarries have been abandoned. 2
Shawpeneak Ridge—Ulster County, New York
Residential development under construction—Fishkill, New York
River view condominiums—Port Ewan, New York
Today some former industrial sites in the Mid-Hudson Valley are considered prime waterfront real estate. The Valley is attractive to developers not only because of the Hudson River and its scenic landscapes, but also due to the proximity to Albany and New York City and the commuting corridors of Interstate 87 and Interstate 84. As developers discover the area and make plans to redevelop abandoned industrial areas or old farmland, planning boards and communities will have to weigh the value of the new developments and the strain that they may have on the environment and public health. With the resurgence of development, the Mid-Hudson Valley may see a dramatic increase in impervious surfaces, the loss of forested river corridors and open space, and consequently, the degradation of local water quality.
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The artists of the Hudson River School depicted the dramatic rock formations, cliffs, vistas, streams, rivers, and lakes of the Mid-Hudson Valley, capturing these disappearing landscapes of the mid-1800s at the start of the Industrial Revolution.
John F. Kensett, “View on the Hudson”
However, if planned and designed properly, a development can maintain good water quality while providing more public access to natural resource areas, protecting and restoring natural and cultural resources, and allowing for economic growth. This progress is achieved when citizens, developers, planners, engineers, architects, biologists, contractors, inspectors, landscape architects, and elected officials all work towards the same goal. Success today needs to be measured not only in terms of economic and social development but in the protection of ecological resources as well. Integrating local planning strategies with region-wide conservation of scenic, natural, and cultural resources will help to ensure that water quality remains high in the Hudson Valley. The artists of the early nineteenth century Hudson River School were reacting to the dramatic changes of their time, painting landscapes that were quickly disappearing as the industrial age approached. Today, residents of the MidHudson Valley face a similar prospect with the possibility that forested waterfront land may be developed hastily and compromise valuable natural resources. Instead, the Hudson riverfront can be developed in ways that protect water quality, conserve natural lands, and provide healthy communities for families to live and work.
Asher B. Durand, “Rocks and Trees”
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THIS HANDBOOK OUTLINES model development principles to provide design guidance for water quality protection during each stage of development. The principles and their supporting techniques are designed to be used by developers, planners, and local ofďŹ cials to work toward reducing impervious cover, conserving natural areas, and preventing stormwater pollution. Finally, the handbook looks at a speciďŹ c proposal for waterfront development in Kingston, New York, to demonstrate how these key principles can be applied.
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Principle
1:
Conserve Natural Buffers and Open Land
Background Site planners have an excellent opportunity to reduce stormwater runoff and prevent the degradation of local waterways simply by changing the way they design new residential subdivisions. A thorough ecological analysis of a site can help determine the appropriate size and location of a future subdivision in order to protect vital natural areas from disturbance and control how much impervious surface is created in a watershed. While site design strategies that conserve open space go by various names, such as clustering or conservation design, they all incorporate similar techniques of
concentrating density on one portion of the site and protecting sensitive areas elsewhere on the site. Although open space subdivisions have been advocated by planners for many years, they are often prohibited or severely restricted by local zoning regulations. Few developers are willing to take risks with site plans that may take years to approve or that may never be approved at all. Communities should consider making open space subdivisions a by-right development option and not require special exceptions or zoning variances, which require more review time.
A sustainable approach to development is to strategically protect corridors of vegetation along waterways thereby maintaining vital links for wildlife habitat and protecting water quality.
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Principle
1
E f f e c t s o f D e v e l o p m e n t Pa t t e r n s i n t h e Wa t e r s h e d Forest cover and wetlands play a critical role in protecting waterways and maintaining balances within the hydrologic cycle. Vegetated corridors along rivers, streams, wetlands, and lakes provide critical habitat for important plant and animal communities. Buffers of vegetation also work to limit erosion and the inux of sediment into rivers and freshwater systems.
Predevelopment conditions
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Typically, developments only reserve open space on land that is unbuildable due to environmental constraints like oodplains, steep slopes, and wetlands, and so the resulting open space is often highly fragmented and isolated. Forest cover is dramatically reduced and impervious surfaces cover a considerable portion of the land area, compromising the overall health of waterways.
Conventional development patterns
Principle
1
Conserve Natural Buffers and Open Land A more sustainable approach to development is to strategically protect corridors of vegetation along waterways thereby maintaining vital links for wildlife habitat and protecting water quality. Concentrating houses and roads on portions of the development site can conserve valuable forested land and protect waterways. Conservation developments have been documented to reduce impervious cover, which sharply reduces stormwater and nutrient export from a new development. Furthermore, maintained and restored
river buffers and natural areas can enhance the beauty and environmental quality of a community, provide public access points to waterfronts, and increase property values (CWP, 1998). Protecting open space and clustering development can also save construction costs by reducing the amount of roads and stormwater infrastructure needed (CWP, 1998). On the next pages, some of the techniques of conservation planning are examined as they apply to residential subdivisions.
Open space or clustered development patterns conserve vegetated waterways. 9
Principle
1
techniques Identify areas most suitable for conservation
Identify and protect wildlife movement corridors and connections to significant waterbodies for upland species such as bobcat or deer. River systems are corridors of exceptional significance in the landscape. A continuously vegetated river corridor is essential to maintain desirable aquatic conditions, such as cool water temperature and high oxygen content. Without these, viable populations of sensitive fish and native aquatic plant species will not be maintained (Dramstad et al., 1996).
Create a variable width vegetated buffer system
Establish a buffer system to protect streams, shorelines, and wetlands at the development site. The buffer should encompass critical environmental features such as the 100-year floodplain, steep slopes, and freshwater wetlands in order to fully protect water quality and help treat stormwater. Buffer areas can also enhance the beauty and environmental quality of a community, provide space for recreation trails and public access points to waterfronts, and increase property values (Kwon, 2000).
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Principle
1
techniques
Group buildings
Open space development incorporates smaller lot sizes to minimize total impervious area, reduce total construction costs, conserve natural areas, and provide community recreational space. Housing can be detached single-family homes, as well as multi-family housing, or a mix of both.
Conserve and enhance vegetative buffers
Wide corridors of dense vegetation ďŹ lter pollutants and control erosion. Contact with plant stems and leaf litter slows water movement, and plant roots and soil organic matter absorb dissolved substances (nitrogen, phosphorus, toxins) before they reach surface waters (Dramstad et al., 1996). Native trees, shrubs, and grasses are very well adapted to local conditions and require minimal maintenance, while providing important wildlife habitat. Conserving native vegetation can save land owners between $270-$640 per acre in mowing and maintenance costs annually (CWP, 1998). 11
Principle
2:
Minimize Impervious Surfaces
Background Roads, parking lots, sidewalks, rooftops, and other impermeable surfaces have a direct impact on the hydrology, water quality, habitat structure, and biodiversity of aquatic systems. Research indicates that when the total amount of impervious area in a watershed reaches 10 percent, aquatic ecosystems begin to show evidence of degradation, and coverage greater than 30 percent results in severe, practically irreversible degradation (Metro, 2000).
These alternative designs can have significant economic benefits for developers, with savings achieved through reduced pavement and infrastructure costs. Moreover, flexible design standards can allow developers to create attractive, compact lots that are more livable and marketable and better suited to their sites.
Imperviousness is one of the few variables that can be explicitly quantified, managed, and controlled at each stage of land development. Communities have significant opportunities to reduce impervious cover by revising their street standards so that streets are no more than the minimum width to safely carry traffic and meet parking demand. For example, local regulations for development in New York State typically require wide streets in residential neighborhoods. These regulations were created by broad applications of high volume and high speed design criteria, the perception that on-street parking is needed on both sides of the street, and the perception that wide roads provide unobstructed access for emergency vehicles (Kwon, 2000). These perceptions can create large amounts of unneeded impervious surface in the landscape. Community planners and site designers should be encouraged to examine alternative street and lot layouts in order to determine the best options for reducing overall site imperviousness. 13
Principle
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Effects of Impervious Land on Runoff Quantity and Quality Stormwater is an important resource. In an undisturbed landscape, most rainfall soaks into the soil and recharges the groundwater. A very small volume of runoff makes its way into lakes and streams. Trees, shrubs, and herbaceous plants intercept, evaporate, and infiltrate precipitation.
In an undisturbed landscape, vegetation absorbs runoff and moderates water temperature.
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Land development often eliminates features that moderate stormwater runoff. Water flowing across impervious surfaces increases in temperature and speed. This intensified runoff carries sediment and other pollutants into streams, lakes, and rivers. Downstream bank erosion and flooding increase. Instead of a valuable resource, stormwater becomes a costly and sometimes dangerous problem.
Roads, parking lots and buildings increase runoff volume, pollutant load, and water temperature.
Principle
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Minimize and Disconnect Impervious Surfaces Minimizing impervious surfaces and retaining the natural landscape as much as possible are effective techniques for promoting inďŹ ltration, evaporation, and transpiration and maintaining a balanced hydrologic cycle. Breaking up areas of impervious surface into smaller units and restoring vegetation
in disturbed areas can signiďŹ cantly reduce runoff volume, temperature, and pollutant loads and promote groundwater recharge. The following pages explore speciďŹ c techniques for minimizing imperviousness in the suburban landscape.
Stormwater runoff is moderated in volume and temperature by retaining vegetation and minimizing pavement. 15
Principle
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Narrow street widths
techniques
Residential streets are typically the largest single component of impervious cover in a subdivision. Many communities require that residential streets be excessively wide, often 36 feet wide or more, even when they serve developments that produce small volumes of traffic (CWP, 1998). Instead, streets can be carefully planned so that street width declines with decreasing average daily trips (Schueler, 2000). Creating a hierarchy of streets with smaller, narrower interconnected local roads also functions to disperse traffic and create more walkable communities.
trees in right of way 16’
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Incorporate street trees into the right of way
Street trees help break up impervious surface and absorb runoff between roads, sidewalks, and parking lots. Street trees can also increase safety and comfort for pedestrians and bicyclists, providing a barrier between cars and the sidewalk. Many studies indicate that narrow residential streets may be safer than wider streets. Narrower street widths tend to reduce the speed at which drivers travel, and slower vehicle speeds give drivers more time to react and prevent potential accidents (CWP, 1998).
low traffic volume narrow road 22’
16’
Principle
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techniques
Reduce street and driveway lengths
A longer street network produces more impervious cover and higher development costs than a shorter one. Total street length is a function of the distance between house lots and site layout. Smaller lots clustered together can reduce overall street length. Site designers should examine alternative street layouts in order to increase the number of homes directly accessible from the main streets. A savings of approximately $150 per linear foot can be achieved by shortening roads (CWP, 1998). This includes savings achieved through reduced pavement, curb and gutter, and storm sewer construction.
Typical low-density residential subdivision
Relax setbacks and frontages
Strict requirements for minimum setbacks and frontage distances can increase impervious cover of a site. Large front-yard setbacks extend driveway lengths, and large side-yard setbacks directly inuence the road length needed to serve individual lots (CWP, 1998). Generally, a more compact street network can be achieved by reducing frontage distances and side-yard setbacks.
Subdivision with reduced setbacks and smaller lot sizes
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Principle
2
techniques
Promote nontraditional lot designs
Flexible setback, lot shape, and frontage distances allow site designers to create attractive and unique lots that provide homeowners with enough space for personal recreation while still creating common open space areas (CWP, 1998).
7’
12’
7’
Satisfy on-street parking demands
It is possible to design relatively narrow, short streets even when housing densities require more on-street parking. Providing a continuous parking lane on both sides of the street is a very inefficient and expensive way to satisfy parking needs for residential communities. If one of the on-street parking lanes also serves as a traffic lane (called a queuing lane), both traffic movement and parking needs can be met by a street that is 26 feet rather than 38 feet wide (CWP, 1998). queuing lane
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traffic lane
parking lane
Principle
2
techniques
Plan street connectivity
A highly connected street system with many alternative routes ensures that travel is more direct and travel distances are shorter. Local trafďŹ c, which makes up 70 percent of all vehicular trafďŹ c, stays local and can be accommodated within a network of smaller roads rather than funneled into busy arterials (Metro, 2002). The interconnected street pattern better accommodates the development of town centers, reducing typical strip development along arterials.
Connect neighborhoods with greenways
Connecting neighborhoods does not necessarily entail building streets to accommodate automobiles. A vegetated network of streams, ridges, or other natural features can provide excellent opportunities for non-vehicular greenways and connections between neighborhoods (Metro, 2002).
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Principle
2
techniques
Use porous surface materials
The use of porous pavements is appropriate for parking lots, where travel speeds are signiďŹ cantly lower than roadways. Varying the surface materials between the travel lane and parking stall can also add visual interest to a parking lot.
Minimize parking requirements compact parking stalls take up 30% less space asdf standard parking stall dimensions are too large for most cars
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Reduce the overall imperviousness associated with parking lots by providing compact car spaces, minimizing stall dimensions, and setting appropriate parking ratios. For example, many parking codes require a standard parking stall dimension that is geared to larger vehicles, despite the fact that small cars constitute 40 to 50 percent of all cars on the road. Compact car stalls create up to 30 percent less impervious cover than stalls for larger cars (CWP, 1998).
Principle
2
techniques
Encourage mass transit
Mass transit can lower parking demand directly by reducing the number of vehicles driven, and therefore the number of vehicles parked and the amount of parking surface. Parking codes should be revised to lower parking requirements where mass transit is available at a site.
Provide shared parking
An overall strategy for reducing parking lot runoff is reducing the actual parking spaces needed by allowing adjacent land uses to share parking lots. For shared parking to operate successfully, the participating facilities should be in proximity to each other and should have different hours of peak operation. For example, banks, schools, and retail stores typically have daytime peak hours so they can share parking space with movie theaters, bars, or restaurants (CWP, 1998).
Excessive impervious surface is created without shared parking arrangements
Shared parking arrangements signiďŹ cantly reduce the area needed for parking
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Principle
3:
Treat All Stormwater Runoff On Site
Background The conventional approach to stormwater management in the Mid-Hudson Valley has focused on collecting and conveying stormwater runoff to a centralized stormwater facility and then directly into the Hudson River. When a site is developed, natural drainage paths and native vegetation in the watershed are typically replaced with paved gutters, storm drains, pipes or other elements of artificial drainage.
Stormwater treatment systems need to be designed to reflect the challenges specific to the Hudson Valley region. For example, in cold climates, design needs to deal with challenges such as winter snow melt and frost heave. Areas of karst topography present specific challenges, including a high risk of groundwater contamination and sinkhole formation.
A more effective approach to stormwater management is to utilize decentralized small-scale systems to treat and infiltrate stormwater runoff close to where it originates. Stormwater should be retained or absorbed on-site so that the rate and quality of runoff are not significantly different from what they were before the site was developed. In addition to protecting water quality and reducing the impacts of flooding, addressing runoff close to the source can also lower site infrastructure costs and reduce land clearing and grading costs. The general goals for good stormwater management are to maintain groundwater recharge quality and quantity and to reduce stormwater pollutant loads being conveyed directly into surface waters. Existing soil conditions, vegetation, and some engineered terrain are used to delay, capture, store, treat, or infiltrate runoff. These elements are all designed to replicate the pre-development hydrologic conditions of a site.
Design stormwater systems to reflect the specific ecological conditions of the Hudson Valley
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Principle
3
Effects of conventional stormwater management practices Vegetation in an undeveloped landscape absorbs large quantities of rainfall and snowmelt. Wetlands and ponds can retain significant volumes of water; forests and grasslands slow the rate of surface runoff and filter pollutants.
Predevelopment hydrologic conditions
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With a conventional approach to stormwater management, the natural flow paths of rainwater are dramatically altered. Water is conveyed off site as quickly as possible, which depletes groundwater supply and discharges excess pollutants and sediments into waterways.
Conventional “pipe and pond” stormwater management
Principle
3
Tr e a t A l l S t o r m w a t e r R u n o f f O n S i t e There are many cost-effective, environmentally beneficial, very localized modifications that can greatly enhance stormwater management systems. By using microscale, decentralized stormwater management
techniques, greenspaces in the landscape can treat stormwater and remove pollutants. The following pages outline specific techniques that can help support the natural hydrologic cycle of site to be developed.
Alternative stormwater management promotes filtration and groundwater recharge on site
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Principle
3
techniques
Filter pollutants
Bioswales and filter strips are very simple and effective off-line systems that are used to treat the first flush of runoff from impervious areas. Runoff is directed into a shallow, landscaped area and temporarily stored. The runoff then passes through a filter bed of sand, organic matter, soil or other media before it enters the groundwater. These engineered swales can cost two to three times less to install and maintain than a typical curb and gutter system (CWP, 1998).
Infiltrate runoff
Stormwater infiltration practices capture and temporarily store water before allowing it to infiltrate into the soil over an extended period. A simple trench can be backfilled with coarse aggregate layered with filter fabric in an area with low-runoff soils. Linear detention basins can provide temporary storage in areas with higher runoff rates (Metro, 2002). Pretreatment of stormwater using bioswales or filter strips is often necessary before infiltrating runoff into the soil.
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Principle
3
techniques
Reduce speed of runoff
Gently sloping vegetated open channels are designed to ďŹ lter rainwater and slow its velocity within dry or wet cells formed by check dams. Open channels can be an effective curb-and-gutter replacement (Metro, 2002).
Delay and store runoff in ponds
Stormwater ponds are common features for managing runoff in northern regions, though they are not always effective for treating pollutants and removing sediment. Several innovative design concepts can help improve the function of stormwater ponds. For example, locating sediment forbays at the primary stormwater inlets, using berms to extend the ow path, and using inundationtolerant plant species to ďŹ lter sediments and remove pollutants are all techniques that can improve pond performance (Schueler, 2000). 27
Principle
3
techniques
Replicate wetland functions
Undisturbed wetlands help to protect groundwater, control ooding, reduce storm damage, prevent water pollution, and provide aquatic wildlife habitat. Replicating the hydrology, plant communities, and soils of a wetland system can be an effective way to treat stormwater runoff. However, it is important to note that stormwater wetlands cannot legally be constructed within existing jurisdictional wetlands.
A constructed wetland ďŹ lters runoff through plant uptake and microzomes in the soil.
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Principle
3
techniques
Direct rooftop runoff to pervious areas
Building codes often require that downspouts from rooftops be directly connected to the stormwater conveyance system in order to minimize the danger of puddling and ice formation on driveways and sidewalks. Sending rooftop runoff over a pervious surface before it reaches an impervious surface can address these issues, as well as decrease the annual runoff volume from residential development sites by as much as 50 percent (CWP, 1998).
Use street tree wells as detention basins
Trees in developed areas can play an important role by preventing soil erosion, replenishing moisture in soil and groundwater, and absorbing and transpiring rainfall. Street tree wells can function as detention basins for sidewalk runoff and can be used in conjunction with other vegetated treatment systems, as long as some subsurface drains allow for eventual drainage from the tree well (Metro, 2002).
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Principle
3
techniques
Pe r f o ra t e c u r b s and gutters
curb inserts
perforated curb
Curbs concentrate runoff and direct it into the storm drainage system. Concentrated flow has more velocity and volume and can convey larger sediment loads into the storm system. Breaking up a continuous curb with inserts or installing prefabricated perforated curbs can effectively reduce water velocity and volume and allow water to flow into vegetated filtration areas (Metro, 2002).
Landscape curb extensions
Runoff from sidewalks and roadways can be directed into a curbside planting area to improve water quality, reduce stormwater flow, and improve the appearance of community streets. Planting strips that extend into neighborhood streets can slow traffic, define parking spaces, and reduce the impervious cover of a wide road (Viani, 2006).
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Principle
3
techniques
Integrate stormwater treatment systems
Using multiple integrated stormwater systems creates synergy, offers backup for any underperforming components in the series, and fits systems naturally into the landscape. A “treatment train” could include (1) a vegetated swale at the edge of a parking lot flowing into (2) a wetland detention system which overflows to (3) an extended treatment pond system.
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Principle
4:
Reduce Erosion and Sedimentation
Background The relatively short period when vegetation is cleared and a site is being graded for new construction is the most destructive phase of development (Schueler, 2000). Trees are removed and topsoil is stockpiled, soils are exposed to erosion, steep slopes are cut, and riparian areas are disturbed. Exposed soils are easily dislodged and transported by precipitation. These sediments are then carried downslope by stormwater runoff and discharged in a waterway. Uncontrolled construction sites can lose between 20 and 200 tons of sediment per acre (Claytor, 2000). Sediments can have adverse effects on aquatic life in streams, lakes and estuaries. Turbidity resulting from sedimentation can reduce light penetration for submerged aquatic vegetation and aquatic insects and fish that are critical to aquatic ecosystems. Sedimentation can physically alter habitat by destroying the riffle-pool structure in stream systems
and smothering organisms such as clams and mussels. Therefore, reducing sediment loss during construction is essential to maintaining water quality and aquatic ecosystems. Typically perimeter controls, such as silt fences and sediment basins, have only modest success in reducing sediment levels at construction sites (Schueler, 2000). Given such a limited ability to remove sediments once they have been eroded, the most effective approach is to prevent erosion from occurring in the first place. Limiting clearing and grading to small parcels (under five acres), protecting sensitive areas (steep slopes, drainage ways, and waterways), phasing construction, and establishing a vegetated or mulch cover on exposed soils will help to prevent erosion from taking place. In ecologically sensitive areas such as forests, river buffers, and stream channels, clearing should be precluded altogether.
Uncontrolled construction sites can lose between 20 and 200 tons of sediment per acre. 33
Principle
4
Effects of clearing and grading a construction site Vegetation stabilizes the steep slopes of a river bank and protects waterways and sensitive natural areas from sediment that comes from upland eroded areas.
Predevelopment conditions
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The hydrology of a site changes during the initial clearing and grading that occur during construction. Trees that had intercepted rainfall are removed and natural depressions that had temporarily ponded water are graded to a uniform slope. The spongy humus layer of forest oor that had absorbed rainfall is scraped off, eroded or severely compacted.
Clearing and grading of an entire site
Principle
4
Reduce Erosion and Sedimentation Clearing and grading is limited to the minimum amount needed for individual building footprints and construction access. Construction and clearing are phased to limit the amount of soil exposed at any one
time. As much of the site is conserved in as natural state as possible. The following pages outline techniques that work to retain the natural hydrology of a site and prevent erosion during construction.
Sediment and erosion controls are best implemented throughout the construction phase.
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Principle
4
techniques
Phase construction to limit soil exposure
To limit exposure of disturbed soil and protect waterways and sensitive areas, only a portion of a construction site should be disturbed at any one time. Other portions of the construction site are not cleared until the construction of the earlier phase is nearly completed and exposed soils have been stabilized (Claytor, 2000). Construction access should coincide with planned roadways whenever possible to avoid unnecessary soil compaction.
Protect existing vegetation
Vegetation to be protected must be clearly delineated in the field by posting signs, flagging, and fencing. Conserving existing vegetation is the best way to protect the soil, limit erosion, and retain the natural hydrology of a site during construction. Maintaining vegetation on sites can increase residential and commercial property values by 6 to 15 percent and a property’s selling price by 3.5 to 4.5 percent (CWP, 1998).
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Principle
4
techniques
Minimizing clearing and grading
Some portions of a development site should never be cleared or graded. Clearing and grading should be restricted to the minimum area required for building footprints and construction access in order to protect river and stream buffers, forest conservation areas, wetlands, springs, seeps, and highly erodible soils (Brown, 2000). Minimizing clearing can reduce off-site sedimentation up to 36 percent and save a developer up to $5000 per acre in earth movement and erosion control costs (CWP, 1998).
Stabilize soils quickly
Establishing a grass or mulch cover within two weeks after soils are exposed can reduce topsoil loss by 80 to 90 percent (Brown, 2000). Hydroseeding must occur within ďŹ ve days after grading. In northern climates, a straw, bark, or ďŹ ber mulch is needed to stabilize the soil during winter months. It is important to permanently stabilize disturbed soils with vegetation at the conclusion of each phase of construction.
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Principle
4
techniques
Establish perimeter controls
Even when the best erosion and sediment control methods are employed, construction sites will still discharge high concentrations of suspended sediments during large storms. As a last line of defense, silt fences and earth dikes are temporarily established at the edge of a construction site to retain sediment that has already been eroded. Even when they are properly installed, located and maintained, silt fences are still only moderately effective in filtering sediment (Caraco, 2000).
silt fence
straw bales
fabric-lined infiltration trench
Improve sediment basins
Floating skimmer outflow
Dual basins for increased storage
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inflow
In addition to establishing silt fences and earth dikes, it is common practice at construction sites to build a basin to capture sediments and allow time for them to settle out. But these basins are not always well designed and they often fail to capture the required amount of sediment (Schueler, 2000). By increasing detention times, sediment basins can be more effective at filtering pollutants. Increased detention times can be increased by providing greater storage volume and multiple basins with gentler side slopes, and installing floating skimmers or perforated risers.
Principle
4
techniques
Assess site immediately after storms
After a storm passes, it is very clear whether or not an erosion and sedimentation control plan actually worked at the construction site. For example, hydroseeding may wash away, silt fences over-top, earth dikes blow out, sediment basins ďŹ ll up or gullies form. Therefore the key element of an effective plan is a rapid response after a storm to assess the damage and quickly correct it. A good construction contract will also include a contingency line item for maintaining and repairing erosion and sediment control systems (Brown, 2001). More than any other tool, the success of erosion and sediment control relies on the judgement and diligence of the contractor, inspector, and engineer (Schueler, 2000).
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Case Study- Kingston, New York Background The Landing and Sailor’s Cove are two proposals for development along 600 acres of riverfront property in Kingston, New York. This site is highly attractive for development because of its open river views and its location near Interstate 87, between Albany and New York City. The plans for development would reclaim parts of an abandoned limestone quarry and build approximately 2,500 residential units and 300,000 square feet of office, retail, and restaurant space, as well as a public
waterfront promenade along 1.5 miles of the Hudson River. At total build-out, the developer’s plan would create approximately 100 acres of new impervious surface and disturb approximately 270 acres of land (Pritchard, 2004). This case study examines some of the consequences of these levels of disturbance and offers specific suggestions for better managing stormwater on the site, preserving sensitive aquatic ecosystems, and protecting local water quality into the future.
The proposed development site (foreground) is predominantly wooded, including an area of secondary old growth forest. Open abandoned quarry areas cover about 15 percent of the site. 41
Case Study Because of the site’s location directly adjacent to the Hudson River, regulations allow the developer to pipe stormwater directly into the river with minimal treatment. The proposed stormwater management plan presented in the Draft Environmental Impact Statement has outfalls at various locations along the Hudson River, as well as into existing quarry excavations and jurisdictional wetlands on site. This conventional system of stormwater management could pose a threat to a number of significant wildlife species currently on site. For example, a large bed of submerged aquatic vegetation is located directly offshore of the Landing and Sailor’s Cove. These submerged aquatic vegetation beds are critical nursery areas for several native species of concern, including the short-nose sturgeon and the American shad. Increased sediment loads and excess nutrient runoff from the proposed development may damage this important aquatic habitat. The proposed development could also inadvertently compromise the water quality of a large untapped aquifer that is a significant potential future water source for the city of Kingston and Ulster County. This aquifer was formed in the highly soluble limestone karst bedrock and is highly pollutable due to the strong surface to groundwater relationship of this formation (Rubin, 2006). Portions of the new development are proposed over the aquifer in abandoned limestone quarry areas and as infill of existing wetlands. Development-related contaminants pose a significant threat to water quality in this sensitive hydro-geologic system. 42
Submerged aquatic vegetation beds (above) are critical nursery areas for the American shad (below) and the short-nosed sturgeon.
Abandoned Quarries
Karst Limestone Aquifer
Forested Wetlands
Case Study
The following pages examine speciďŹ c alternatives for better protecting the sensitive water resources of this site.
x mp le nds
Co
Aquifer Recharge Zone
Submerged Aquatic Vegetation Beds
Hudson River
It is appropriate for these sensitive areas to be used for recreational trails and natural park areas if clearing is limited and wide buffers of vegetation are protected and even restored on disturbed quarry land. Protected and restored river buffers and natural areas can greatly enhance the beauty and environmental quality of a community, provide public access points to the waterfront, and increase property values. Protecting sensitive natural resources and clustering development can also save money in construction costs by reducing the amount of roads and stormwater infrastructure needed to be built.
Approximate area of proposed development
We tla
The karst aquifer recharge zone, the freshwater wetland complex, and the submerged aquatic vegetation beds just offshore are three areas on this project that should be protected from severe disturbance in order to protect water quality. Restricting the amount of vegetation that is cleared and replaced by impervious surface in the aquifer recharge zone and the wetlands complex would help protect sensitive aquatic systems from development-related contamination. Houses and roads should be concentrated only on less sensitive portions of the site and there should be careful treatment of water running off newly created impervious surfaces.
Critical resources on the site should be protected from severe disturbance in order to preserve water quality.
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Case Study North Cove Existing View
THE PROPOSED DEVELOPMENT would create a grassy waterfront access area which would require extensive clearing and grading down to the water’s edge. This landscape does not offer diverse experiences to visitors, it has very little ecological value, and it is very costly to maintain. Clearing this area of vegetation may cause an increase in water temperature and sediment loads which would make the water uninhabitable for some native plant and fish species. AN ALTERNATIVE DESIGN maintains much more of the existing vegetation on the riverbanks while still allowing selective clearing to open up more dramatic views of the water. The parking area and recreation pathway are pushed back from the waters edge. Conserving native vegetation can save landowners between $270 and $640 per acre in mowing and maintenance costs. Maintaining a diverse mix of native trees, shrubs and grasses along the river’s edge will provide seasonal color and texture as well as wildlife observation opportunities. 44
Case Study Waterfront Promenade Existing View
A CONTINUOUS PROMENADE is proposed for 1.5 miles along the river’s edge. Again, the proposed design will require clearing and grading down to the river’s edge, and will replace native vegetation with mown lawn that is costly to maintain. The construction of this landscape may threaten the submerged aquatic vegetation that is directly offshore, and the large expanses of open lawn have very little wildlife habitat value and do not reduce speed, volume and temperature of stormwater runoff. AN ALTERNATIVE DESIGN retains existing vegetation along the bank and restores areas that have been disturbed. These measures protect aquatic wildlife and filter stormwater running off from the development above. Rather than clearing land for open lawn along the entire length of the promenade, the alternative path leads through areas of more dense forest and approaches the river only for special views and sitting areas. The promenade is also narrowed and has a pervious surface to limit runoff and minimize the amount of clearing. 45
Case Study Stormwater Management Plan
A DETENTION BASIN approach to stormwater is proposed. These centralized collection basins are designed to control a storm’s first flush and generally detain the water for up to 48 hours before it moves out of the system and into local waterways. Because of the short detention period, the characteristic mown steep slopes, and the lack of diverse vegetation, opportunities for further treating the water are missed. Moreover, these systems are costly to maintain and are often not very attractive in a neighborhood setting. AN ALTERNATIVE to the detention basin is a constructed wetland system that has an undulating form and vegetation planted along the banks and in the shallow water. The undulating shape slows water and allows groundwater to infiltrate and vegetation filters pollutants from the runoff. These landscaped areas enhance biodiversity and wildlife, require less maintenance, and enhance the aesthetics of a neighborhood.
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Case Study Planting Recommendations Many conventional detention basins have steep slopes that require regular mowing and maintenance and they have few benefits for stormwater treatment. Alternatively, wet pond treatment systems support a diversity of vegetation that function to stabilize steep slopes, filter pollutants and sediments, slow runoff speed, and shade permanent pools of water; they can also provide valuable wildlife habitat. Native trees,
shrubs, and groundcovers are well-suited to local conditions and so they require minimal maintenance. The native plants recommended in the following lists have significant value for the region’s wildlife, they are able to cope with the variable hydrologic conditions found in a stormwater management area, and they are generally available at nurseries in the Hudson Valley.
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Case Study
A maintenance road 1 deep water pool
6 5 upland floodplain 4 slopes riparian terrace 3 shoreline fringe 2 fringe shallow water bench
A1
Constructed wetlands have six hydrologic zones 1) Deep water pool: This pool is typically one to six feet deep and planted with submergent plants capable of taking up pollutants and ďŹ ltering sediments. 2) Shallow water bench: This area is frequently inundated with six inches to one foot of water and is planted with emergent plants that provide pollutant uptake, possible food source and habitat for waterfowl. 3) Shoreline fringe: The shoreline of the wetland has plants that are capable of periodic drought and inundation, require no maintenance, uptake pollutants, stabilize wetland slopes, block access to pond for safety.
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4) Riparian fringe: The area is one to four feet above pool level, is periodically saturated, and is an area of extended detention for the wetland. Plants shade the pool to keep temperature low, provide pollutant uptake, and require little to no maintenance. 5) Floodplain terrace: The area that is occassionally inundated by 10- to 100-year storms. Plants protect slopes and provide shade and visual interest. Using a cover of dense trees will help to reduce maintenance. 6) Upland slopes: Uplands are rarely inundated and plants function as a transition zone into other adjacent land uses. Maintenance access for drainage structures is allowed in this zone
Case Study TREES
Plant lists Hydrologic Zones
SHRUBS Hydrologic Zones Arrowwood Viburnum (Viburnum dentatum) 3, 4
American Elm (Ulmus americana) 4, 5, 6 Bald Cypress (Taxodium distichum) 3, 4
Bayberry (Myrica pennsylvanica) 4, 5, 6
Black Ash (Fraxinus nigra) 3, 4, 5 Black Cherry (Prunus serotina) 5, 6 Blackgum or Sourgum (Nyssa sylvatica) 4, 5, 6
Buttonbush (Cepahlanthus occidentalis) 2, 3, 4, 5
Sambucus canadensis
Black Willow (Salix nigra) 3, 4, 5
Shadbush (Amelanchier canadensis) 4, 5, 6
River Birch (Betula nigra) 3, 4, 5
Swamp White Oak (Quercus bicolor) 3, 4, 5
Elderberry (Sambucus canadensis) 3, 4, 5, 6 Red Chokeberry (Aronia arbutifolia) 3, 4, 5
Hackberry (Celtis occidentalis) 5, 6
Smooth Alder (Alnus serrulata) 3, 4, 5
Common Spice Bush (Lindera benzoin) 3, 4, 5
Silky Dogwood (Cornus amomum) 3, 4, 5 Betula nigra
Speckled Alder (Alnus rugosa) 3, 4 Winterberry (Ilex verticillata) 3, 4, 5
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Case Study HERBACEOUS PLANTS
HERBACEOUS PLANTS
Hydrologic Zones
Hydrologic Zones
Arrow arum (Peltandra virginica)
2, 3
Marsh Hibiscus (Hibiscus moscheutos)
2, 3
Arrowhead (Sagitaria latifolia)
2, 3
Pickerelweed (Pontederia cordata)
2, 3
Big Bluestem (Andropogon gerardi)
4, 5
Pond Weed, Sago (Potamogeton pectintus)
2, 3
Sedges (Carex spp.)
Blue Flag Iris (Iris versicolor) Broomsedge (Andropogon virginicus) Common Three-Square (Scirpus pungens) Duckweed (Lemma sp.)
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Plant lists
2, 3
Hibiscus moscheutos
Soft Rush (Juncus effusus) Switchgrass (Panicum virgatum)
2
Sweet Flag (Acorus calamus)
1, 2
Hardstem Bulrush (Scirpus acutus)
2
Wild Celery (Valisneria americana)
Lizard’s Tail (Saururus cernuus)
2
Wool Grass (Scirpus cyperinus)
pontederia cordata
1 2, 3 2, 3, 4 2, 3, 4, 5, 6 2, 3 1 2, 3
Key Resources Arendt, R., Brabec, E., Dodson, H., Reid, C., Yaro, R. (1994). Rural by Design: Maintaining Small Town Character. Chicago, IL: Planners Press American Planning Association.
Pritchard, R. (2004). Stormwater Management Report for The Landing at Kingston and Ulster: City of Kingston and Town of Ulster Ulster County, NY. Kingston, NY.
Brown, W., Caraco, D. (2000) “Muddy Water In, Muddy Water Out?” In Schueler, T., Holland, H. (Eds.), The Practice of Watershed Protection: Techniques for Protecting Our Nation’s Streams, Lakes, Rivers, and Estuaries. Ellicot City, MD: Center for Watershed Protection.
Rubin, P., Burmeister, K., Folsom, M. Karst Resource Management: Groundwater Protection and Developmental Considerations in the Kingston-Rosendale Aquifer System. Ulster County, NY.
Caraco, D. (2000) “Strengthening Silt Fences.” In Schueler, T., Holland, H. (Eds.), The Practice of Watershed Protection: Techniques for Protecting Our Nation’s Streams, Lakes, Rivers, and Estuaries. Ellicot City, MD: Center for Watershed Protection.
Schueler, T. (2000) “Improving the Trapping Efficiency of Sediment Basins.” In Schueler, T., Holland, H. (Eds.), The Practice of Watershed Protection: Techniques for Protecting Our Nation’s Streams, Lakes, Rivers, and Estuaries. Ellicot City, MD: Center for Watershed Protection.
Center for Watershed Protection. (2003). New York State Stormwater Mangement Design Manual. Albany, NY: New York State Department of Environmental Conservation.
Schueler, T. (2000) “Performance of Stormwater Ponds in New England.” In Schueler, T., Holland, H. (Eds.), The Practice of Watershed Protection: Techniques for Protecting Our Nation’s Streams, Lakes, Rivers, and Estuaries. Ellicot City, MD: Center for Watershed Protection.
Center for Watershed Protection (CWP). (1998). Better Site Design: A Handbook for Changing Development Rules in Your Community. Ellicott City, MD.
Schueler, T., Holland, H. (Eds.) (2000). The Practice of Watershed Protection: Techniques for Protecting Our Nation’s Streams, Lakes, Rivers, and Estuaries. Ellicot City, MD: Center for Watershed Protection.
Claytor, R. (2000) “Practical Tips for Construction Site Phasing.” In Schueler, T., Holland, H. (Eds.), The Practice of Watershed Protection: Techniques for Protecting Our Nation’s Streams, Lakes, Rivers, and Estuaries. Ellicot City, MD: Center for Watershed Protection.
Thunhorst, G. (1993). Wetland Planting Guide for the Northeastern United States: Plants for Wetland Creation, Restoration, and Enhancement. St. Michaels, MD: Environmental Concern Inc.
Kwon, H. Y. (2000) “An Introduction to Better Site Design.” In Schueler, T., Holland, H. (Eds.), The Practice of Watershed Protection: Techniques for Protecting Our Nation’s Streams, Lakes, Rivers, and Estuaries. Ellicot City, MD: Center for Watershed Protection. Dramstad, W., Olson, J., Forman, R. (1996). Landscape Ecology Principles in Landscape Architecture and Land-Use Planning. Washington, DC: Island Press. Friends of Kingston Waterfront. (2006). Comments on the Draft Generic Environmental Impact Statement for the Landing. Greene, M. J. (2006). Public Comment on AVR Proposal, The Landing at Kingston and Ulster. Poughkeepsie, NY. New York State Department of Environmental Conservation. (2003). New York Standards and Specifications for Erosion and Sediment Control. Albany, NY: Empire State Chapter Soil and Water Conservation Society. Metro. (2002). Green Streets: Innovative Designs for Stormwater and Stream Crossings. Portland, OR.
Viani, L. O. (2006). “Thinking Outside the Pipe: Portland points the way to reconnecting citizens with the watersheds they live in.” Landscape Architecture. pp. 54- 63.
Image Credits 2) Helderberg Escarpment: http://people.hofstra.edu/faculty/j_b_benning 2) Shawpeneak Ridge: www.scenichudson.org 3) Residential development: www.scenichudson.org 3) Riverview condominiums: www.scenichudson.org 4) Kensett, John F. “View on the Hudson”: http://artchive.com/ftp_site.htm 4) Durand, Asher B. “Study from Nature: Rocks and Trees”: http://artchive. com/ftp_site.htm 33)Construction site: larscapes.com/frankfurt 41) Landing Aerial: www.scenichudson.org 42) Submerged Aquatic Vegetation: www.epa.gov/maia/images/es18aqua. jpg 42) American Shad: www.newsday.com/media/photo/2003-03/6956598. 43) Existing Conditions: Google Earth and Scenic Hudson 44) North Cove existing/ rendering: www.avrrealty.com 45) Promenade exisiting/ Promenade rendering: www.avrrealty.com
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This handbook resulted from a collaboration between the Conway School of Landscape Design and its graduate program in sustainable landscape planning and design, and Scenic Hudson, an environmental organization and land trust working to protect, preserve and restore the Hudson River and its riverfront as a public and natural resource. We would like to acknowledge and give a special thanks to our professors, Paul Cawood Hellmund, Jean Akers, and Ken Byrne, as well as administrators Nancy Braxton and Ilze Meijers. Special thanks to Scenic Hudson: Alix Gerosa, Ned Sullivan, Jeanne Gural, Josh Clague, Warren Reiss, Ray Curran, and Jeff Anzevino. Thanks also to Barbara Kendall of the New York State Department of Environmental Conservation Hudson River Estuary Program for her help and guidance.