Green Stormwater Infrastructure Tools
July 7th, 2014 by annmarie
Trees, shrubs, perennials and grasses help manage rainwater, or stormwater, by diverting water and preventing it from becoming runoff via infiltration, evapotranspiration, and filtration. First, plant leaves, branches, and flowers catch the rain drops before the water hits the ground and becomes runoff. The stormwater collected on these surfaces can easily evaporate into the air and never have to be managed in traditional sewer and stormwater collection systems. Furthermore, plants help manage stormwater runoff by allowing water to infiltrate into the soil and by evapotranspiration, the process in which water is taken up by a plant’s roots and transpired through its leaves. Last, plants and soil also help by filtering stormwater runoff.
Stormwater Tree Trench
A stormwater tree trench is a system of trees that are connected by an underground infiltration structure. On the surface, a stormwater tree trench looks just like a series of street tree pits. However, under the sidewalk, there is an engineered system to manage the incoming runoff. This system is composed of a trench dug along the sidewalk, lined with a permeable geotextile fabric, filled with stone or gravel, and topped off with soil and trees. Stormwater runoff flows through a special inlet (storm drain) leading to the stormwater tree trench. The runoff is stored in the empty spaces between the stones, watering the trees and slowly infiltrating through the bottom. If the capacity of this system is exceeded, stormwater runoff can bypass it entirely and flow into an existing street inlet.
A stormwater bump-out is a vegetated curb extension that protrudes into the street either mid-block or at an intersection, creating a new curb some distance from the existing curb. A bump-out is composed of a layer of stone that is topped with soil and plants. An inlet or curb-cut directs runoff into the bump-out structure where it can be stored, infiltrated, and taken up by the plants (evapotranspiration). Excess runoff is permitted to leave the system and flow to an existing inlet. The vegetation of the bump-out will be short enough to allow for open sight lines of traffic. Aside from managing stormwater, bump-outs also help with traffic-calming, and when located at crosswalks, they provide a pedestrian safety benefit by reducing the street crossing distance.
A stormwater planter is a specialized planter installed in the sidewalk area that is designed to manage street and sidewalk runoff. It is normally rectangular, with four concrete sides providing structure and curbs for the planter. The planter is lined with a permeable fabric, filled with gravel or stone, and topped off with soil, plants, and sometimes trees. The top of the soil in the planter is lower in elevation than the sidewalk, allowing for runoff to flow into the planter through an inlet at street level. These planters manage stormwater by providing storage, infiltration, and evapotranspiration of runoff. Excess runoff is directed into an overflow pipe connected to the existing combined sewer pipe.
Pervious pavement is a specially designed pavement system that allows water to infiltrate through the pavement and never become runoff. This system provides the structural support of conventional pavement but is made up of a porous surface and an underground stone reservoir. The stone reservoir provides temporary storage before the water infiltrates the soil. There are many different types of porous surfaces, including pervious asphalt, pervious concrete, and interlocking pavers. Interlocking pavers function slightly differently than pervious concrete and asphalt. Rather than allowing the water to penetrate through the paving, pavers are spaced apart with gravel or grass in between to allow for infiltration.
A green roof is a roof or section of roof that is vegetated. A green roof system is composed of multiple layers including waterproofing, a drainage layer, an engineered planting media, and specially selected plants. Green roofs can be installed on many types of roofs, from small slanting roofs to large commercial flat roofs. Two basic types of green roofs have been developed: extensive and intensive. An extensive green roof system is a thin (usually less than 6 inches), lighter-weight system planted predominantly with drought-tolerant succulent plants and grasses. An intensive green roof is a deeper, heavier system designed to sustain more complex landscapes. A green roof is effective in reducing the volume and velocity of stormwater runoff from roofs by temporarily storing stormwater, slowing excess stormwater release into the combined sewer system, and promoting evapotranspiration.
A rain barrel or cistern is a structure that collects and stores stormwater runoff from rooftops. The collected rain water can be used for irrigation to water lawns, gardens, window boxes or street trees. By temporarily holding the stormwater runoff during a rain event, more capacity can be added to the city’s sewer system. However, rain barrels and cisterns only serve an effective stormwater control function if the stored water is used or emptied between most storms so that there is free storage volume for the next storm. Rain barrels are designed to overflow into the sewer system through the existing downspout connection in large storm events. Although these systems store only a small volume of stormwater, collectively they can be effective at preventing large volumes of runoff from entering the sewer system.
A rain garden is a garden designed to collect runoff from impervious surfaces such as roofs, walkways, and parking lots, allowing water to infiltrate the ground. The garden is normally moderately depressed (lower than the surrounding ground level), with the bottom layer filled with stone so runoff can collect and pond within it. The site is graded appropriately to cause stormwater to flow into the rain garden area from the nearby impervious area. The water ponds on the surface, is used by the vegetation in evapotranspiration, and infiltrates into the subsurface stone storage and soil. Rain gardens can be connected to sewer systems through an overflow structure, but usually they are sized to infiltrate the collected stormwater runoff within 72 hours. Flexible and easy to incorporate into landscaped areas, rain gardens are suitable for many types and sizes of development and retrofits. Rain gardens are effective at removing pollutants and reducing stormwater runoff volume.
A flow-through planter is a structure that is designed to allow stormwater from roof gutters to flow through and be used by the plants. Flow-through planters are filled with gravel, soil, vegetation and a connection to the roof downspout to let water flow in. They temporarily store stormwater runoff on top of the soil and filter sediment and pollutants as water infiltrates down through the planter. They are typically waterproofed, and the bottom of the planter is normally impervious. As a result, planters do not infiltrate runoff into the ground; they rely on evapotranspiration and short-term storage to manage stormwater. Excess water can overflow into the existing downspout connection. Flow-through planters can be constructed in many sizes and shapes and with various materials, including concrete, brick, plastic lumber, or wood.
Saw Mill River Daylighting Project Breaks Ground (Water) at Larkin Plaza! Wednesday, Dec. 15, 12 noon
December 14th, 2010 by stormeditor
Bringing the Saw Mill River back into the “light of day” (hence the term “daylighting”) in downtown Yonkers was an idea shared by many people over the years and finally a plan made “shovel-ready” in the last five. On Wednesday, December 15, 2010, at 12 Noon, Mayor Amicone, the City of Yonkers Mayor, will officially hold groundbreaking ceremonies at Larkin Plaza for the new Saw Mill River park in Larkin Plaza. Groundwork Hudson Valley, a non-profit organization located in Yonkers, has been the City of Yonkers’ environmental partner on the daylighting, bringing in grant resources to provide a top-rate habitat restoration plan and involving the public in interpreting the history and ecology of the park. This will assure continuation and enhancement not only of Saw Mill River fisheries, but the central role the Saw Mill has played in the history and future of Yonkers.
“We are ecstatic that the City is going to bring this river back above ground,” commented Ann-Marie Mitroff, Director of River Programs for Groundwork, “it will become a jewel around which Yonkers will thrive.” Rick Magder, Groundwork’s Executive Director, who established the Saw Mill River program in 2001, agreed, “The newest asset for challenged urban communities is being able to use their rivers to spur rebirth and redevelopment. We are pleased the City is so forward thinking.”
A lot has happened to the piece of land now known as Larkin Plaza. It was a wide bay and mouth of the Saw Mill River in 1609 when Henry Hudson explored the river now bearing his name and was known as the “fishing trap” to Native Americans living in the vicinity. In the late 1640’s Adriaen Van der Donck received grant of land from the Dutch East India Company built one of the first saw mills in the New World at the junction of the Hudson and Nepperhan (Saw Mill) Rivers-at the top of Larkin Plaza. The bay was filled in for the railroad and a station was built in 1848. Industry was built alongside and over the river in the plaza area. In the 1920s, due to localized flooding and sanitary conditions of the river, the US Army Corps of Engineers banished the river underneath a 20-foot subterranean flume, built a parking lot over it, and it was named Larkin Plaza.
It will look much different after construction is finished in December of 2011. A new river park with two freshwater pools and one tidal pool will replace the paved parking lot. Meandering paths will be located on both sides of the “new” river, an area for public concerts will be constructed, ample benches for viewing will be installed, and educational interpretive signs will cover the ecology, history and engineering of the park. Groundwork received funding support from the New York-New Jersey Harbor Estuary Program to support the development of the habitat restoration plan for the park, additional funding from the US EPA also in support of the daylighting work, and grants from the Hudson River Foundation and the NY Department of Environmental Conservation to support the interpretive plan for the park.
For more information about the ecology of the new park and the habitat plan, contact Ann-Marie Mitroff at Groundwork Hudson Valley, (914) 375-2151.
Additional information will be posted on the Groundwork Hudson Valley (www.groundworkhv.org), Saw Mill River Coalition (www.sawmillrivercoalition.org), and on www.daylightyonkers.com.
Thank-you for Attending the Roundtable and Making It a Success!
October 24th, 2010 by stormeditor
Saturday’s roundtable was quite a success. Thomas Madden, Commissioner, Department of Community Development and Conservation, Town of Greenburgh, presented a detailed and thoughtful presentation on how to make LID/BSD practical in local government. An enthusiastic question & answer session followed. (His presentation will be available here for download sometime this week.)
During the break, County Legislator Tom Abinanti spoke to attendees about the proposed Stormwate / Flooding Management legislation under consideration by the County. The current draft is under review this Monday, October 25 by the Environment & Energy Committees. (Please see right side-bar Special Events listing with details.)
The two breakout sessions, one on LID/BSD Principles and the other on a LID/BSD Checklist, generated lots of discussion and valuable feedback. Updates to the draft handouts will be available here for download soon. (Session drafts are still available in the right side-bar Downloads section.)
Special thanks to Anne Jaffe-Holmes of the Greenburgh Nature Center for her support and help in organizing this roundtable.
Stormwater Roundtable #3: Local Communities Working Together on Stormwater
October 20th, 2010 by stormeditor
Low-Impact Development & Better Site Design
in Our Municipal Ordinances & Processes
Held Saturday, October 23, 2010 at the Greenburgh Public Library, 300 Tarrytown Road, Elmsford, NY.
KEYNOTE: Thomas Madden, Commissioner, Department of Community Development and Conservation, Town of Greenburgh will talk about the “practical” side of incorporating LID/BSD principals in an comprehensive plan, ordinances, and processes.
Breakout Session at Workshop #2
– Watershed-Wide Principles On Which We Can Agree
– Defining an Effective Stormwater Implementation Worksheet
Download draft versions of the Principles and the LID/BSD Checklist for your review and discussion. (See right sidebar file list).
Sponsored by: Groundwork Hudson Valley / Saw Mill River Coalition, Greenburgh Nature Center, Greenburgh Environmental Forum, Federated Conservationists of Westchester County.
Funding provided by: US EPA, NYS DEC/Hudson River Estuary Program, and Westchester Community Foundation.
StormwaterTools Content Survey
October 20th, 2010 by stormeditor
Please help us to determine the most useful information and resources to include in our upcoming Toolkit site by taking a short online survey.
Click here to take survey.
The survey is also available as a .pdf file in the right sidebar under Downloads & Resources.
About Our Previous Workshops
October 19th, 2010 by stormeditor
First roundtable May 9, 2009 at the Irvington Library
Peter Q. Eschweiller, Chair of the Westchester County Flood Action Task force and former Westchester County Planning Commissioner, talked about “A Watershed Approach for Greenburgh & Its Villages” – which included maps of watersheds in each village and in the unincorporated areas. He also spoke about Westchester County’s Flood Action Task force and the need for a comprehensive county-wide flood action plan. Download it here (.pdf).
Second roundtable January 23, 2010 at the Irvington Library
Low Impact Development/Better Site Design Roundtable
During this roundtable Sandeep Mehrotra, Vice President, Hazen & Sawyer P.C., and past Chair of the Hastings Environmental Commission, made a presentation on LID/BSD Principles and Practices with a focus on those appropriate for our area. As part of the break-out sessions, groups worked together on re-engineering sample site plans according to Better Site Design principles. Mark Gilliland, landscape designer, Principle of Garden Artistry and a member of the Irvington Environmental Conservation Board, and two local engineers, Paul J. Petretti, Principle of PJP Engineering, and Shannon Rooney, Principle of SR-Engineers, helped facilitate the breakout sessions.
Handouts from workshop:
All About Water – keynote presentation by Sandeep Mehrotra. Download it here (.pdf).
Low Impact Development / Better Site Design Pros, Cons and Planning Considerations – handout by Shannon Rooney. Download it here (.pdf).
Rain Garden Maintenance Guide by Low Impact Development Center. Download it here (.pdf).