An Introduction to Low Impact Development

Transcription

1 Slide 1 An Introduction to Low Impact Development 2012 Envirothon Trainings Salvatore Mangiafico Rutgers Cooperative Extension Environmental and Resource Management Agent This presentation will introduce the topic of low impact development. Specifically it will introduce small-scale, distributed stormwater control devices such as rain gardens, rain barrels, green roofs, and pervious concrete. This is a relevant topic for New Jersey as the state has extensive urban and suburban development, making dealing effectively with stormwater an important goal. Areas of the state have ongoing issues with flooding, water supply, and polluted waterbodies, which are significant concerns in some places.

2 Slide 2 Thinking about landscapes and water We re going to begin this presentation by thinking about different landscapes and different land uses, and how those land uses affect what happens to water in those landscapes.

3 Slide 3 Simplified hydrologic cycle Precipitation, irrigation (rain, snow) Infiltration Sub-surface flow Runoff Stream This is a very simplified version of the hydrologic cycle, but it has some of the elements we need to focus on for this discussion. (You should be able to name some processes that are not included in this diagram. Notably missing are transpiration from plants, evaporation from soil, and movement of water into deeper groundwater.) The question we want to focus on is, When it rains --- or when there is snowmelt --- where does that water go? Some portion of it can soak into the ground. There it might be stored in the soil so that plants can use it, or it might move into shallow groundwater where it might contribute to the baseflow of a local stream, or it might percolate more deeply into the ground and contribute to recharging groundwater stores. Recharging groundwater is important since a large portion of our drinking water is pumped from groundwater. Also, water for irrigating crops is often pumped from groundwater. It s important to think about how water that infiltrates into the soil contributes to the baseflow of streams. Have you ever wondered why there s still water in a stream when it hasn t rained for several weeks in the summer? It s because water that has soaked into the ground can move slowly through the soil toward a nearby stream. It may take the water days or weeks or months to reach a stream or pond On the other hand, some precipitation may run off the surface of the land. In this case, the water can move relatively quickly toward a nearby stream, particularly if it flows through stormwater pipes or ditches.

4 Slide 4 And let s think a little more about soil Figure by Caitrín Higgins, Rutgers Cooperative Extension Water Resources Program We also need to focus on how the soil interacts with water when thinking about landscapes and water use. First, what properties would a soil need to be able to allow water to infiltrate? It needs to be porous enough to allow the water to soak in and move through it. A soil that can allow a high rate of water to infiltrate is said to have a high infiltration capacity. In contrast, a soil that has been very compacted --- by having heavy equipment run over it, or from people walking on it continually --- may have a low infiltration capacity. Some clayey soils may also have a low infiltration capacity naturally.

5 Slide 5 Photo: Salvatore Mangiafico Looking at this scene, if it rains, where do you think the water will go? For a usual, fairly gentle rain, we expect that most of the water would infiltrate into the soil. Both the trees and the vegetation on the forest floor help to slow the water, and the action of growing roots, insects, and worms should keep the soil porous enough to infiltrate water in most cases. Some water may run off the surface of the land, and if there is a particularly hard rain or the ground is sloped, a greater portion may run off.

6 Slide 6 Photo: Salvatore Mangiafico How about in this scene, where does the water go? With all the roofs and streets and sidewalks and parking lots, there isn t much of a chance for the water to infiltrate into the ground. In this picture, there is a small area of turfgrass on the left side. If the soil is in good condition there, some rain could be infiltrated into the ground. But in the rest of the photo, the water will flow into storm drains, like the one in the foreground of the photo. From there, it will move through the stormwater infrastructure toward a nearby stream or lake. All these surfaces that don t allow water to infiltrate --- the roofs and streets and sidewalks and parking lots --- we call impervious surfaces.

7 Slide 7 Photo: Salvatore Mangiafico What about in this scene, where will the water go? There are some impervious surfaces, like the roof and driveway and street. It may be the case that water from the roof flows into a gutter, down a downspout, onto the driveway, and then on to the street, where it then goes to a storm drain. But a large area of the ground in the photo is covered with turfgrass and landscape plants. If the soil is in good condition, most of the rain from these areas may infiltrate into the soil and not get into the storm drain.

8 Slide 8 Photo: Salvatore Mangiafico This is a photo of the National Mall in Washington, D.C., with the Washington Monument in the distance and the Smithsonian on the left. Do you know why there are large patches with no grass? The soil here is compacted from so many people walking on it. When the soil is compacted there are not enough spaces between the soil particles to hold water and air, which the plant roots need to survive. So where will the water go in this landscape when it rains? Where the soil is bare and compacted, water is likely to run off the surface. Also, where there isn t any vegetation to hold the soil in place or slow the water, the soil is likely to erode. If this eroded soil makes its way to a local stream or lake, it can be harmful to fish habitat by clouding water and covering the gravel bottom of some rivers and lakes. Eroded soil also carries phosphorus, which can cause eutrophication, algae blooms, and fish kills.

9 Slide 9 Photo: Salvatore Mangiafico In this picture is a field of soybeans in the foreground and corn in the background. What do you think happens to the water when it rains in this landscape? Because there is a good cover of vegetation to catch and slow water, a large portion of the water should infiltrate into the soil. In addition, the farmer probably takes good care of the soil by adding compost or using cover crops to keep the soil healthy. But also consider the case when a farm field has been recently plowed and there isn t any vegetative cover. In that case a heavy rain could cause soil erosion.

10 Slide 10 Photo: Salvatore Mangiafico How might wildlife in the landscape affect what substances are found in runoff? In this photo are snow geese in a farm field, but remember also that urban and suburban environments in New Jersey can have significant populations of wild animals such as deer, turkey, other birds, and small mammals like squirrels, raccoons, and skunks. Consider also that there are pets like dogs in these areas. What pollutants might these animals contribute to stormwater runoff?

11 Slide 11 The Impact of Development on Stormwater Runoff natural conditions Federal Interagency Stream Restoration Working Group Stream Corridor Restoration: Principles, Processes, and Practices. Washington, D.C. The next few slides show --- in a generalized way --- how developing land from a natural state to a suburban or urban landscape affects the hydrologic cycle. It s important to note that these are just generalizations. The actual amount of runoff or infiltration depends upon a variety of factors, such as the amount of rainfall and the conditions of the soil. For example, the amount of runoff may be greater on steep slopes or for intense rain storms or if there is little soil on top of bedrock. This slide shows infiltration and runoff amounts for a landscape in its natural conditions. There is little runoff for typical rainfalls, with the figure given here for runoff being 10% of the rain. The amount of infiltration is relatively large, with 50% of water infiltrating into the soil. The rest of the rain water presumably goes to evaporation from leaves and soil.

12 Slide 12 The Impact of Development on Stormwater Runoff medium density development Federal Interagency Stream Restoration Working Group Stream Corridor Restoration: Principles, Processes, and Practices. Washington, D.C. This slide shows infiltration and runoff amounts for a landscape with a medium density suburban development. The amount of runoff has increased from natural conditions, increasing from 10% to 30% now. The amount of infiltration has decreased, with 35% of water here infiltrating into the soil.

13 Slide 13 The Impact of Development on Stormwater Runoff urban development Federal Interagency Stream Restoration Working Group Stream Corridor Restoration: Principles, Processes, and Practices. Washington, D.C. This slide shows infiltration and runoff amounts for a landscape with dense urban development. The amount of runoff has increased further, up to more than 50% now. The amount of infiltration has decreased further, with only 15% of water here infiltrating into the soil.

14 Slide 14 The idea of non-point source pollution: many sources of pollutants, each may only contribute a little bit Image: NOAA Ocean Service Education, ce.html. The past few slides emphasized the effects of development on the hydrologic cycle. Another effect we will have to consider when thinking about stormwater management and low impact development is the amount pollutants in the water. There are a variety of substances that occur in different landscapes that can act as pollutants if they make their way into rivers, lakes, or coastal waters. For example, suburban landscapes can contribute nitrogen and phosphorus from lawn fertilizers, bacteria and pathogens from pet wastes, motor oil from streets and parking lots, grass clippings and leaves, and trash. Likewise, construction sites can contribute sediment from soil erosion. It s important to note that with non-point source pollution there are usually small amounts of pollutants contributed by many different sources. For example in a suburban watershed, there may be hundreds of home lawns, with each contributing a small amount of nitrogen from fertilizer. There may be no one culprit. There is a connection between water pollution and the hydrologic cycle, because some pollutants from non-point sources are more likely to travel with runoff or stormwater. These include phosphorus, sediment, and bacteria. If water infiltrates into the soil instead, these pollutants can be partially or mostly removed by the soil.

15 Slide 15 What does conventional stormwater management look like

16 Slide 16 What does conventional stormwater management look like Impervious roof, roads, and parking lots Roof gutters Collect, convey, detain Very good at preventing upstream flooding Storm drains Pipes to detentions basins or the nearest stream Photo: Salvatore Mangiafico The goal of the stormwater management infrastructure in most residential and urban areas is to prevent flooding in that area. It s effective in collecting stormwater and quickly moving it away. Water runs off of roofs and roads and parking lots. Water from roofs is collected by gutters, sent down downspouts, and piped into the stormwater system. Water from roads goes into storm drains where it is piped toward a nearby stream. Often the stormwater flows to a detention basin first which stores the water for a period of time and slowly discharges it to the receiving stream.

17 Slide 17 Connected Impervious Surfaces Slide by Rutgers Cooperative Extension Water Resources Program These photos exemplify our conventional stormwater management: rainwater falling on the roof is captured by the roof gutter and travels down the downspout, and in this case across the driveway, toward the street and down the storm drain. The rightmost photo shows the inlet to a detention basin.

18 Slide 18 Slide by Rutgers Cooperative Extension Water Resources Program. Photo: NRCS, Will/South Cook Conservation District. Looking at this housing development, we can see all the impervious cover in this landscape: the roofs and roads and parking lots, and imagine the amount of stormwater that is generated. How we handle that stormwater across a whole watershed can make a difference on the amount of water and the amount of pollution reaching the streams and lakes within the watershed.

19 Slide 19 Add detention basins along the path Photo: Sal Mangiafico This is a photo of a small and simple detention basin. Runoff from the road and parking areas on the right flow into the storm drain, and into the recessed basin. The water exits through the pipe on the left to the rest of the stormwater infrastructure. You can imagine that for relatively small rains, water is able to move from the entrance to the exit without much delay. Larger rains are detained when the basin fills and empties slowly.

20 Slide 20 Add detention basins along the path Photo: US EPA. This is a photo of a typical detention basin used in many parts of the country, including in New Jersey. Notice a concrete low-flow channel has been added to convey the water efficiently from the entrance to the exit and to prevent standing puddles. (The structure in the upper left is an overflow riser to prevent the basin from overtopping). Notice these basins are typically maintained in mowed turfgrass. Also note they are meant to be dry most of the time. (Another type of basin that is designed to hold standing water most of the time is called a wet pond.) Dry detention basins are effective at slowing water in large rain events to decrease downstream flooding, but they are only moderately effective at removing pollutants from the stormwater. For small rain storms, the flow may simply flow through the basin in the concrete channel with little interaction with the rest of the basin.

21 Slide 21 Consider soil compaction in developed areas Images: Sal Mangiafico, Rutgers Cooperative Extension As mentioned previously, even vegetated areas may suffer from soil compaction if they have received a lot of vehicle or foot traffic. You may not be able to tell, but the lawn on the left is composed almost entirely of crab grass and other weeds. In this case, the soil at this newlyconstructed home was too compacted --- and also nutrient-poor --- to support the growth of turfgrass. The compaction may have been from heavy equipment use combined with poor soil management during construction. Could soil compaction also be a problem for detention basins maintained in turfgrass?

22 Slide 22 Problems with conventional stormwater management Downstream flooding Reduction in baseflow for streams Reduction in groundwater recharge Stream scour Salvatore Mangiafico Our conventional stormwater management is good at conveying water away from upstream cities and preventing flooding there. Detention basins help decrease downstream flooding, but during large rain events, or if the basins are insufficient, flooding in downstream areas can be a problem. This increase in flow in the stream channel also results in the stream banks being eroded, a process sometimes called stream scour. Because only a small fraction of rain water may have the chance to infiltrate into the soil, there is less water to contribute to the baseflow of streams or to recharge groundwater supplies.

23 Slide 23 Photos: Rutgers Water Resources Program Scenes of flooding in the City of Camden.

24 Slide 24 Federal Interagency Stream Restoration Working Group Stream Corridor Restoration: Principles, Processes, and Practices. Washington, D.C. telprdb This figure shows two hydrographs (blue lines) that indicate the change in the amount of water flowing in a stream due to urban development in a watershed. On the x-axis is time and on the y-axis is discharge --- which is the amount of water flowing in the stream per minute. Notice that as we move from the pre-development stream (dashed blue curve) to the postdevelopment stream (solid blue curve), the peak discharge is greater (the curve is taller), and the peak discharge occurs sooner (the peak is more to the left of the graph).

25 Slide 25 Slide by Rutgers Cooperative Extension Water Resources Program This photo shows an example of severe bank erosion a small river, probably caused by high water flow after storms.

26 Slide 26 Problems with conventional stormwater management Nonpoint source pollution Salvatore Mangiafico The previous slides emphasized the hydrologic effects --- the effects on the water cycle --- of conventional stormwater management. But how we manage stormwater can also affect the amount of pollutants that reach streams and lakes.

27 Slide 27 Problems with conventional stormwater management Lots of stuff in urban / suburban environment ~ 60% of water pollution is from NPS (includes agriculture, urban, forestry, etc.) - nutrients (fertilizers) & pesticides - oil and chemicals - sediment (eroded soils), incl. construction sites - heavy metals (cars, etc.) - bacteria and disease (pets and wildlife) - all kinds of trash Salvatore Mangiafico There are a variety of pollutants that can come from non-point sources. Non-point source pollution is any pollution that doesn t come from an identifiable point like a discharge pipe or a smokestack. Instead, non-point source pollution comes from many spots throughout the landscape, such as many home lawns, roof tops, or farm fields. The kinds of pollutants found in stormwater runoff will depend upon the type of land use. For example, we might find more heavy metals in runoff from an urban area and more sediment in runoff from a construction site. One estimate is that 60% of all water pollution is from non-point sources, including urban and rural land uses. Some common non-point source water pollutants found in urban and suburban environments include nitrogen and phosphorus from fertilizers used for lawns and gardens, pesticides used in homes or lawns, motor oil and other chemicals, eroded soil particles from construction sites, heavy metals that come from cars, harmful bacteria from pet and wildlife feces, and trash.

28 Slide 28 Problems with conventional stormwater management Lots of stuff in urban / suburban environment Which leads to - impacts to streams, lakes, marine environments - impacts to wildlife / fish kills - beach closures - algae and other water quality effects - drinking water contamination Salvatore Mangiafico - Lots of money repairing these problems If they are present in large amounts, these pollutants can have negative impacts on the aquatic environment and the plants and animals that live there. These impacts include fish kills, beach closures, an overabundance of weeds and algae, and drinking water contamination. Trying to restore polluted waterbodies or drinking water can require considerable investments of money, perhaps making preventing the pollution more cost-effective.

29 Slide 29 Images: Sal Mangiafico, Rutgers Cooperative Extension A pond and a lake with overabundances of algae and weeds, probably from non-point source pollution.

30 Slide 30 Images: Sal Mangiafico, Rutgers Cooperative Extension Planktic algae making the lake water soupy green.

31 Slide 31 First Flush Effect Slide by Rutgers Cooperative Extension Water Resources Program Because pollutants can collect on impervious surfaces during dry weather when it doesn t rain, sometimes the first runoff after a dry period has higher levels of pollutants than during later rainstorms. This phenomenon is called the first flush effect. Because of this effect, low impact development practices may not need to treat all the runoff from a rain storm, but could be fairly effective by treating the first flush of stormwater.

32 Slide 32 Problems with conventional stormwater management Combined sewer overflow issue especially in older urban environments Salvatore Mangiafico Another issue is that several of the older cities in New Jersey have their stormwater infrastructure connected to their sewer system so that the sewage mixes with stormwater when it rains. During large rain storms, this mixture may discharge to a stream, an event known as a combined sewage overflow. Low impact development helps prevent these discharges by decreasing the amount of stormwater going to the stormwater system.

33 Slide 33 Low Impact Development Salvatore Mangiafico

34 Slide 34 Low Impact Development LID is an approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing effective imperviousness to create functional and appealing site drainage that treat stormwater as a resource rather than a waste product. Salvatore Mangiafico From 2012 Envirothon Current issues topics This is the definition of low impact development from the 2012 Envirothon Current Issues topic: Low impact development is an approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible. Low impact development employs principles such as preserving and recreating natural landscape features, minimizing effective imperviousness to create functional and appealing site drainage that treat stormwater as a resource rather than a waste product.

35 Slide 35 Low Impact Development By implementing LID principles and practices, water can be managed in a way that reduces the impact of built areas and promotes the natural movement of water within an ecosystem or watershed. Applied on a broad scale, LID can maintain or restore a watershed's hydrologic and ecological functions. Salvatore Mangiafico From 2012 Envirothon Current issues topics By implementing low impact development principles and practices, water can be managed in a way that reduces the impact of built areas and promotes the natural movement of water within an ecosystem or watershed... Applied on a broad scale, low impact development can maintain or restore a watershed's hydrologic and ecological functions.

36 Slide 36 development or re-development Note, urban areas in New Jersey may be built out and need retrofitting, sometimes in a very tight urban environment Other parts of the state have the opportunity to use Smart Growth ideas. Salvatore Mangiafico Note that some areas in New Jersey may already be built out, where all land is already committed to a specific land use. In these cases, there might not be room for any new development, but existing developments can be retrofitted to include low impact design features. These might include dense urban areas which could benefit from stormwater planters, green roofs, or rainwater harvesting. On the other hand, brand new communities could be designed with smart growth principles which might include considerations of energy efficiency and minimizing sprawl, as well as considering stormwater management.

37 Slide 37 green infrastructure The term green infrastructure is also used to indicate the component mechanisms, e.g. rain gardens, green roofs, etc and adding elements like preserving open space and using areas for recreation Salvatore Mangiafico The term green infrastructure can be used to refer to low impact design components like rain gardens and green roofs. Sometimes the term also includes other environmentally friendly infrastructure, like open space for human recreation.

38 Slide 38 - Infiltration - Filtration and treatment by soil - Evapotranspiration - Water reuse How LID Works LID: - Treats stormwater at the source - mimicking natural hydrology - reducing effective impervious area Salvatore Mangiafico As mentioned in the previous definition, low impact development attempts to treat stormwater at the source, rather than send it down a pipe for storage at a distant detention basin. It attempts to mimic the natural hydrology of an area by allowing stormwater to infiltrate onsite. Also, it reduces the effective impervious area, for example by disconnecting roof runoff from the stormwater infrastructure or by replacing traditional pavement with pervious pavement. When water infiltrates into the soil, many pollutants are naturally removed from the water, either by the soil physically removing pollutants like a filter or chemically binding up the pollutants. Also, soil organisms like bacteria and plants can remove or break down some pollutants. Plants also use up some of the water by taking up the water and transpiring it back to the atmosphere. Many low impact development practices treat stormwater as a resource --- by using it to water plants or collecting it in a rain barrel --- rather than treating it like a waste product to be disposed of.

39 Slide 39 How LID Works 1) Hydrology Salvatore Mangiafico Considering the water cycle

40 Slide 40 Federal Interagency Stream Restoration Working Group Stream Corridor Restoration: Principles, Processes, and Practices. Washington, D.C. telprdb The goal of low impact development is to return a developed area back to the natural hydrology, moving from the solid line back to the dashed line. This is accomplished by increasing infiltration, disconnecting impervious surfaces, and minimizing runoff.

41 Slide 41 How LID Works 2) Water pollutants - Sedimentation and filtration (Removes sediment, trash, soil-bound phosphorus, some soil-bound pathogens) - Adsorption to soil particles (Removes dissolved metals and soluble phosphorus) Salvatore Mangiafico Low impact development also helps reduce non-point source pollution. Specifically, by slowing runoff water with vegetation, rocks, or mulch --- or by allowing water to infiltrate the soil --- low impact development structures remove sediment and associated pollutants like phosphorus, pathogens in fecal matter, and other particulates like trash and plant debris. Other pollutants like metals and phosphorus may be removed from the water by chemically adsorbing to the soil.

42 Slide 42 How LID Works 2) Water pollutants - Plant uptake (Removes small amounts of nutrients) - Microbial processes (Removes organics and pathogens) - Exposure to sunlight and dryness (Removes pathogens) Salvatore Mangiafico Furthermore, plants remove water from the soil by taking up water and transpiring it back to the atmosphere. Plants also take up some nitrogen and phosphorus, which can act as pollutants if they reach surface waters or drinking water supplies. In the soil, microbial processes --- the activity of bacteria --- break down organic pollutants like motor oil and pesticides. Exposure to sunlight and drying conditions destroy pathogens found in fecal matter from pets and wildlife.

43 Slide 43 Disconnection of roof gutters Photo: Rutgers Water Resources Program The following slides will show examples of low impact development practices A simple example of a low impact development practice is disconnecting roof runoff from the stormwater system, in this case by changing the flow of the downspout from going to the driveway or street and instead diverting it to a pervious area like a lawn, which allows the water to infiltrate into the ground.

44 Slide 44 Permeable pavement Photo: USEPA. Amy Rowe, Green Infrastructure Practices: an Introduction to Permeable Pavement Using permeable pavement is another example of low impact development. This photo shows a cement truck full of water dumping water onto a parking lot paved with permeable pavement. This is at the US EPA office in Edison, New Jersey. Permeable pavements in general have a very high infiltration rates.

45 Slide 45 Permeable pavement Photo: Amy Rowe. Amy Rowe, Green Infrastructure Practices: an Introduction to Permeable Pavement There are different kinds of permeable pavement: pervious concrete, porous asphalt, interlocking concrete pavers, and grid pavers like the kind that have turfgrass growing between them. In general these materials are similar to their convention counterparts --- that is, pervious concrete is similar to regular concrete except that it is made in way that leaves the final concrete surface with pores that can infiltrate water.

46 Slide 46 Permeable pavement Photo: USEPA. Amy Rowe, Green Infrastructure Practices: an Introduction to Permeable Pavement Pervious pavements are somewhat more expensive than their traditional counterparts. During installation, a porous storage layer needs to be placed below the permeable pavement itself to temporary store infiltrated water.

47 Slide 47 Permeable pavement Rubber-edged plow blade and salt (calcium chloride) application Photo: USEPA. There are a few maintenance considerations with permeable pavements. The surface may get clogged over time with sand and fine particles, so occasional vacuuming of the pavement may be necessary. Also, for this reason, sanding in winter isn t advisable, but a salt solution can be used to prevent the surface from icing.

48 Slide 48 Rainwater harvesting Rain barrel at a home Photo: Michele Bakacs, Rutgers Cooperative Extension Another low impact design practice is rainwater harvesting. The goal is to reduce the amount of stormwater by collecting it and using it to water plants after the rain subsides, or for other beneficial uses. Rainwater harvesting can be accomplished at home with a simple rain barrel like the one shown here.

49 Slide 49 Rain Barrels Conserve Water How many gallons of rain water comes from a single rooftop? Photo by: SharkeyinColo Based on a Roof area of 800 ft 2 (40 x 20 ) 1in rainfall event = 500 gallons 1 50 gal rain barrel saves 10% 10 % of 42 in rainfall per year = 2,095 gallons Slide: Mike Haberland, Rutgers Water Resources Program, et al. Even a single 55-gallon barrel can reduce stormwater by a significant amount. This example considers just a section of a home roof, an area of 40 feet by 20 feet, which produces 500 gallons of stormwater in a 1-inch rainstorm. A 50-gallon barrel could collect 10% of this amount. Depending on the size of rainstorms, and if the barrel is drained between rain events, in the course of a year a single barrel could collect perhaps 2000 gallons.

50 Slide 50 Rainwater harvesting Larger-scale rainwater harvesting at school Photo: Rutgers Water Resources Program This photo shows a larger-scale water harvesting system at a school. The two collection vessels together hold perhaps 1000 gallons of water, and the system is designed so that any overflow goes to stormwater infrastructure when the tanks are full. The system also has a pump that supplies water to the irrigation system for a nearby ornamental garden.

51 Slide 51 Rainwater harvesting Slide: Mike Haberland, Rutgers Cooperative Extension, photo credit not known This photo shows some decorated rain barrels.

52 Slide 52 Rain garden Photo: Rutgers Water Resources Program Rain gardens are another popular low impact design structure in New Jersey. They are aesthetically attractive, and can be used at homes or at public buildings like schools, libraries, and offices.

53 Slide 53 Rain garden Photo: Rutgers Water Resources Program For a rain garden, a shallow depression is dug and planted. Stormwater is diverted into the garden where the water is held and can infiltrate into the soil. The garden should drain completely within 48 hours to prevent creating a habitat where mosquitoes can breed.

54 Slide 54 Rain Garden Site Selection and Installation Surface Area = (L1xW) + (L2xW) Roof Roof = (15 x20 ) + (10 x20 ) = (300 ) + (200 ) = 500 square feet W L1 L2 Hockman Farm, Winchester, Virginia Slide: Rutgers Water Resources Program Rain gardens can be designed to treat a certain volume of stormwater, for example from a certain roof area. The water can be piped from the roof area directly to the garden.

55 Slide 55 Rain Garden Site Selection and Installation Rain Garden Drainage Area Slide: Rutgers Water Resources Program Or from a parking lot or other impervious area.

56 Slide 56 Rain garden Slide: Rutgers Water Resources Program Rain gardens can be designed with a variety of plants and in a variety of locations.

57 Slide 57 Rain garden Photo: Elizabeth Boyajian and Rutgers Water Resources Program Two native wildflowers that are commonly used in rain gardens: black-eyed Susan (Rudbeckia), and butterfly weed (Asclepias).

58 Slide 58 Bio-retention Basin Figure: USEPA, Low Impact Development A Literature Review A bio-retention basin is a general term for a vegetated area that holds and treats runoff. A rain garden is a type of bio-retention basin. Bio-retention basins may be larger and engineered to treat larger volumes of water, for example to treat runoff from a parking lot at a big-box store.

59 Slide 59 Stormwater basin retrofitting Figure: Mike Haberland, Rutgers Cooperative Extension Traditional stormwater detention basins --- like those shown earlier in this presentation --- can be retrofitted by changing the way the water flows through them and planting them with native vegetation or other vegetation, so that they allow more infiltration and function more like bioretention basins.

60 Slide 60 Stormwater planter Figure: USEPA, Design Principles for Stormwater Management on Compacted, Contaminated Soils in Dense Urban Areas A stormwater planter is also similar to a rain garden, except it is built in a container so that it can be installed in urban environments or other places where planting a garden may not be practical.

61 Slide 61 Green roof Slide: Rutgers Water Resources Program A green roof can be similarly designed and installed on a rooftop.

62 Slide 62 Green roof Figure: USEPA, Design Principles for Stormwater Management on Compacted, Contaminated Soils in Dense Urban Areas

63 Slide 63 Swales Photo: Sal Mangiafico Swales are vegetated waterways used to channel stormwater. They are often maintained in turfgrass or taller grasses. A swale allows some water to infiltrate, and also slows flowing water to allow the settling out of sediment and removal of some pollutants. They should be engineered so that their size, shape, and slope allows for the maximum benefits.

64 Slide 64 Benefits, Issues, Considerations Benefits of LID: - reduced runoff volumes and pollutant loadings to downstream waters - reduced incidences of combined sewer overflows - groundwater recharge, water for plants in landscape, stream baseflow Salvatore Mangiafico From 2012 Envirothon Current issues topics These final few slides will present some benefits and challenges of implementing low impact development solutions... Benefits of low impact development include reduced runoff volumes and pollutant loadings to downstream waters; increased groundwater recharge and stream baseflow; and where it is an issue, reduced incidences of combined sewer overflows.

65 Slide 65 Benefits, Issues, Considerations Benefits of LID: - improved aesthetics - expanded recreational opportunities - increased property values due to the desirability of the lots and their proximity to open space - improved quality of life. Salvatore Mangiafico From 2012 Envirothon Current issues topics Other benefits of low impact development might include improved aesthetics, expanded recreational opportunities, increased property values, and improved quality of life.

66 Slide 66 Benefits, Issues, Considerations Some difficulties with LID: - Private property - Incentives for private citizens and companies to do - Cost to install - Cost to maintain - Knowledge to maintain - Site limitations: space, soil properties, regulations about roads and parking and stormwater conveyance - Community fear of mosquitoes, overgrown areas, ticks Salvatore Mangiafico There may be some difficulties with implementing low impact development strategies. Since low impact development structures are typically installed on private property, there must be incentives for private citizens and companies to implement them. There are installation and maintenance costs, and some maintenance may require a higher level of training than other landscape maintenance. Some sites have limitations, including those of limited space, soil properties, regulations about the design of roads and parking areas, and regulations about stormwater structures. In some cases, there may be discomfort in the community about the potential for mosquitoes, overgrown vegetated areas, ticks, wildlife, and other nuisances.

67 Slide 67 Benefits, Issues, Considerations Considerations: - Functionally Equivalent Landscape : - water storage - water infiltration - groundwater recharge - water detention Salvatore Mangiafico The term functionally equivalent landscape is sometimes used to describe the goal of having a developed area mimic the pre-development hydrology in terms of water infiltration, water storage in the soil, groundwater recharge, and stormwater detention.

68 Slide 68 Benefits, Issues, Considerations Benefits of LID: - Allows developers to comply with municipal or state requirements that limit allowed negative effects of development on the amount of stormwater produced Salvatore Mangiafico And, importantly, implementing low impact development structures may allow developers to comply with municipal or state requirements that limit the permissible effects of development on the amount of stormwater produced.

69 Slide 69 Benefits, Issues, Considerations Which LID practice is appropriate? - Space and practicality - Soils : well drained or wet? compacted? - Amount of water to be treated - Aesthetics - Pollutants of concern - Costs, Maintenance, Knowledge Salvatore Mangiafico There are a host of considerations that would influence which low impact development practices may be most appropriate. A full discussion is beyond the scope of this presentation, but a few considerations include: the space available; the conditions of the site, such as if the soils are poorly drained or compacted; the amount of stormwater to be treated; aesthetic goals for the site; the probable pollutants in the stormwater; and the limitations of installation costs and required maintenance.

70 Slide 70 Salvatore Mangiafico County Environmental and Resource Management Agent Cooperative Extension of Salem County 51 Cheney Rd, Ste. 1 Woodstown, NJ mangiafico@njaes.rutgers.edu