The URL can be used to link to this page

Home My Public Portal AboutPlanning Board Packet 10/27/21 supplementalINFILTRATION TRENCH ~managing runoff from rooftops and paved areas~ Purpose: Infiltration trenches collect and infiltrate runoff from paved driveways, rooftops and other areas. Infiltration trenches work best in well-drained soils like sands and gravels. Due to their relatively small size, they can effectively handle only smaller rainfall events. Infiltration trenches are not well suited for areas that receive large amounts of sediment (e.g., gravel driveways) as they will fill in quickly. Installation: Dig a trench that is 18” wide and at least 8” deep. Make sure to dispose of the soil in a flat area where it cannot be washed into the lake. The front and sides of the trench may be edged with stone or lumber to hold the stones in place. Extend the life of the infiltration trench by lining the sides with non-woven geotextile fabric. Fill to within 3” of the ground level with ½” to 1½” crushed stone. Fold a flap of non-woven geotextile fabric over the top of the trench and top off with additional stone. Materials: Crushed stone can be purchased at your local gravel pit. Contact your local Soil and Water Conservation District for suppliers of non-woven geotextile fabric. Other geotextiles, including landscaping weed barrier, can be substituted for smaller projects. Maintenance: To maintain these structures, periodically remove accumulated debris and weeds from the surface. Non-woven geotextile fabric will extend the life of these structures, however, they will eventually clog over time and the stone will need to be removed and washed to clean out the accumulated sediment and debris. Part of the Conservation Practices for Homeowners Factsheet Series, available at: Maine DEP (800.452.1942); http://www.maine.gov/dep/blwq/docwatershed/materials.htm Portland Water District (207.774.5961); http://www.pwd.org/news/publications.php SURFACE RUNOFF Non-woven Filter Fabric Clean Crushed Stone 8” deep 18” wide Portland Water District May 2006 DEPLW0775 RAIN BARRELS ~managing roof runoff in your backyard~ Purpose: Rain barrels provide an innovative way to capture rainwater from your roof, and store it for later use. Water collected from rain barrels can be used to water lawns, gardens, and indoor plants. This water would otherwise run off your roof or through downspouts and become stormwater, picking up pollutants on its way to a storm drain, stream, or lake. You can lower your water bill, conserve well water in the dry season, and reduce polluted stormwater runoff. Installation: A rain barrel must be placed on a level surface. If you have gutters, place the rain barrel beneath the downspout so the water flows onto the screen on top of the barrel. You may need to have your downspout cut to an appropriate height above your rain barrel. If you do not have gutters, find a location where water concentrates from your roof and place the rain barrel where it will capture this steady stream of water during rain storms. Elevate your rain barrel by placing it on cinder blocks or a sturdy wooden frame. Raising the barrel allows the barrel to drain properly, and you to easily fit a watering can underneath the spout, or attach a hose so you can recover the rainwater you have collected. Soaker hoses can also be attached to the rain barrel to slowly release water into gardens and recharge groundwater. Materials: Rain barrels are available in many sizes and styles, and range in price from $60 to over $200. Contact your local hardware store, garden center, or nursery. You can also order rain barrels on-line from Portland Water District at www.pwd.org (spring only) or SkyJuice New England http://www.skyjuice.us (year round). Building your own rain barrel is usually the least expensive option. Several web sites exist with material lists and clear directions. Sites are as follows: http://www.ci.superior.wi.us/publicwks/wastewater/RainBarrelInstructions.htm http://www.cwp.org/Community_Watersheds/brochure.pdf http://www.dnr.state.md.us/ed/rainbarrel.html Finally, you can simply use an open barrel to collect rainwater. Keep in mind that you should use the water within two weeks because the development of a mosquito from egg to adult takes 10 to 14 days. Maintenance: Gutters and downspouts should be clean of debris. Leaves and pine needles can clog gutters and prevent water from reaching the rain barrel. Furthermore, check the screen on the rain barrel after each storm event and remove leaves or pollen that has plugged the screen. Freezing water can damage your barrel. Rain barrels should be drained and stored before freezing weather sets in to prevent ice damage. They can be stored outside if they are turned upside down and the faucet is covered. Be sure to put something heavy on your rain barrel so it doesn’t roll away. Rain barrels can also be stored inside a garage or other protected area. Part of the Conservation Practices for Homeowners Factsheet Series, available at: Maine DEP (800.452.1942); http://www.maine.gov/dep/blwq/docwatershed/materials.htm Portland Water District (207.774.5961); http://www.pwd.org/news/publications.php Portland Water District N ov 2012 DEPLW0783 RAIN GARDENS ~managing roof runoff in your backyard~ http://clean-water.uwex.edu/pubs/raingarden/gardens.pdf Purpose: Rain gardens are attractive and functional landscaped areas that are designed to capture and filter stormwater from roofs, driveways, and other hard surfaces. They collect water in bowl- shaped, vegetated areas, and allow it to slowly soak into the ground. This reduces the potential for erosion and minimizes the amount of pollutants flowing from your lawn into a storm drain, and eventually into our streams and lakes. Installation: Rain gardens can vary in size, but are most effective when built to 20-30% of the drainage area. Rain gardens for single-family homes will typically range from 150 to 300 square feet, but even a smaller one will help reduce water pollution problems. The garden should be bowl-shaped, with the lowest point of the garden no more than 6” below the surrounding land. The sides should be gently sloping towards the center to prevent sudden drop-offs that could lead to erosion problems or walking hazards. Rain gardens are often placed in a preexisting or created depression within a lawn, or in a location that receives roof runoff from a downspout. To avoid flooding improperly sealed foundations, build your rain garden 10’ away from existing structures, and direct water into the garden with a grassy swale, French drain, gutter extension or other device. Rain gardens can be placed in sunny or shady regions of your lawn, but plants should be chosen accordingly, with the lowest point planted with wet tolerant species, the sides closest to the center planted with moist tolerant species, and the edges of the rain garden should be planted with sub- xeric (moist to dry) or xeric (dry) tolerant plants. It is also important to check the permeability of your soil. Sandy soils only need compost added, but clay soils should be replaced with a mix (50- 60% sand, 20-30% topsoil, 20-30% compost). After construction of the garden is complete, the entire area should be covered with a thick layer of mulch, preferably Erosion Control Mix. Materials: Replacement Soil mixes and Erosion Control Mix are available from local garden centers. Native plants can be purchased from your local nursery. Please see Native Plant Lists from this series for plant descriptions based on specific sun and soil conditions. Maintenance: Overall, once plants mature, the maintenance of a rain garden is very low. Watering is important during the first growing season, and some weeding is necessary after planting. As the garden matures, some of the perennials may need to be divided if plantings become too crowded. Part of the Conservation Practices for Homeowners Factsheet Series, available at: Maine DEP (800.452.1942); http://www.maine.gov/dep/blwq/docwatershed/materials.htm Portland Water District (207.774.5961); http://www.pwd.org/news/publications.php Before After After Before Portland Water District May 2006 DEPLW0784 DRIPLINE TRENCH ~managing roof runoff on homes without gutters~ Also Called: Roof Dripline Trench, Infiltration Trench Purpose: Dripline trenches collect and infiltrate stormwater, and control erosive runoff from the rooftop. The trenches collect roof runoff and store it until it soaks into the soil. These systems also minimize wear on your house by reducing back splash. Installation: Dig a trench that is 18” wide and at least 8” deep along the drip line. Slope the bottom away from the house so that water will drain away from the foundation. Make sure to dispose of the soil in a flat area where it cannot be washed into the lake. Fill the trench with ½” -1½” crushed stone. The front and sides of the trench may be edged with stone or with pressure-treated lumber to hold the stones in place. Extend the life of the dripline trench by lining the sides with non-woven geotextile fabric and filling to within 3” of the ground level with stone. Fold a flap of non-woven geotextile fabric over the top of the trench and top off with additional stone. Note: Dripline trenches work best in sand and gravel soils that can quickly disperse a large volume of water. They should not be used on structures with improperly sealed foundations, as flooding may result. Materials: Crushed stone can be purchased at your local gravel pit. Contact your local Soil and Water Conservation District for suppliers of non-woven geotextile fabric. Other geotextiles, including landscaping weed barrier, can be substituted for smaller projects. Maintenance: To maintain these structures, periodically remove accumulated debris and weeds from the surface. Trenches lined with non-woven geotextile fabric will require less frequent maintenance, however, they will still clog over time and the stone will need to be removed and washed to clean out the accumulated sediment and debris. Part of the Conservation Practices for Homeowners Factsheet Series, available at: Maine DEP (800.452.1942); http://www.maine.gov/dep/blwq/docwatershed/materials.htm Portland Water District (207.774.5961); http://www.pwd.org/news/publications.php 5” Crushed Stone Non-woven Geotextile Fabric 3” Crushed Stone Portland Water District May 2006 DEPLW0770 DRYWELLS ~managing roof runoff from homes with gutters~ Purpose: Drywells collect and infiltrate runoff at gutter downspouts and other places where large quantities of concentrated water flow off rooftops. These systems help control erosive runoff on your property, and reduce wear on your house by minimizing back splash. Installation: Drywells should measure about 3’ x 3’ x 3’, be lined with non-woven geotextile fabric and back-filled with 1/2” to 1½” crushed stone. Slope the bottom of the drywell away from the house so that water does not drain towards the foundation. Make sure to dispose of the removed soil in areas where it will not wash into the lake. Extend the life of the dry well by lining the sides with non-woven geotextile fabric and filling to within 3” of the ground level with stone. Fold a flap of filter fabric over the top of the dry well and top off with additional stone. Note: Drywells work best in sand and gravelly soils that can quickly disperse a large volume of water. They should not be used on structures with improperly sealed foundations, as flooding may result. If flooding is of concern, place the drywell 6’ away from the base of the foundation. Materials: Crushed stone can be purchased at your local gravel pit. Contact your local Soil and Water Conservation District for suppliers of non-woven geotextile fabric. Other geotextiles, including landscaping weed barrier, can be substituted for smaller projects. Maintenance: To maintain these structures, periodically remove accumulated debris and weeds from the surface. Non-woven geotextile fabric will extend the life of these structures, however, they will eventually clog over time and the stone will need to be removed and washed to clean out the accumulated sediment and debris. Part of the Conservation Practices for Homeowners Factsheet Series, available at: Maine DEP (800.452.1942); http://www.maine.gov/dep/blwq/docwatershed/materials.htm Portland Water District (207.774.5961); http://www.pwd.org/news/publications.php 3’ Non-woven Geotextile Fabric 3’ ½”-1½” Crushed Stone Portland Water District May 2006 DEPLW0771 CONSTRUCTION BMPs ~minimizing erosion with sediment barriers and mulching~ Purpose: Sediment barriers, followed by mulching, are common construction BMPs (Best Management Practices) that intercept and retain sediment from disturbed or unprotected areas. Together these practices minimize pollutants flowing from your property into local streams and lakes. The installation of erosion control measures as directed in these guidelines will meet the requirements of the Maine Erosion and Sediment Control Law. Sediment Barriers: Sediment barriers must be installed before construction of any project that causes soil disturbance, and must be maintained until the area is fully stabilized and vegetation is established. Install sediment barriers across or at the bottom of a slope and down gradient of the area of disturbed earth. Sediment barriers should not be placed in areas of concentrated water flows. Erosion Control Mix (ECM) berms are the simplest method of filtering sediment, but silt fences are another option. At a minimum, berms should measure 4’ wide by 1.5’ high. If silt fences are used, they must be entrenched, kept taut, and installed according to the manufacturer’s directions (see diagram). ECM berms can be left in place after construction is complete, but silt fences should be removed once areas upslope have been stabilized. Once the site is stable, ECM can be raked out and seeded down, or removed and used as mulch elsewhere. Mulching: Mulch all bare areas as soon as possible and prior to any rainstorm. A tarp may be used instead of mulch to cover these areas overnight. Mulch should be thick enough so that the soil is not visible. The following types of mulch are best suited for construction projects: Hay mulch or straw is used as a temporary protective measure to cover bare soils and newly seeded areas. Secure the hay mulch by walking over it. Erosion Control Mix (ECM) is a special mix of wood waste and gravel that holds up to runoff and has a natural look. It is a long-term soil cover that will eventually allow the growth of new vegetation. Before ECM Berm ECM After Hay Mulch Portland Water District Materials: Contact your local contractor or gravel pit to see if Erosion Control Mix is available in your area. This relatively new product may also be called: Slope Stabilizer, Erosion Control Mulch, or Superhumus. Stump grindings may also be used for sediment berms in areas with low slopes. Hay and straw mulch is available in bales from local farms and hardware stores. Silt fences can be purchased from construction supply stores. Maintenance: Until grass and other vegetation is well established, mulched areas and sediment barriers should be inspected regularly for erosion, especially following rain events. Periodically remove sediment and debris that accumulates behind sediment barriers. Erosion Control Mix berms may need to be re-shaped and additional material may be needed to maintain function. For more information concerning the Maine Erosion and Sediment Control Law, contact DEP at 1-800-452-1942. For specific details on these conservation measures, consult the Maine Erosion and Sediment Control BMP manual (2003) at: http://www.maine.gov/dep/blwq/docstand/escbmps/index.htm Part of the Conservation Practices for Homeowners Factsheet Series, available at: Maine DEP (800.452.1942); http://www.maine.gov/dep/blwq/docwatershed/materials.htm Portland Water District (207.774.5961); http://www.pwd.org/news/publications.php Silt Fence Not Maintained 4”x6” Trench with Backfill 12” min depth Sheet Flow Stakes 3’ apart Silt Fence Diagram Silt Fence Not Trenched Working Silt Fence with Hay Bale Reinforcement May 2006 DEPLW0769 17 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs s izi NG a N d d esi GN STEP 1. Soffit depth. A soffit is the underside of a roof overhang. Measure the depth of the soffit by aligning your body under the edge of your roof and measuring the distance from your body to the house. This is the reference line. STEP 2. Reference line. Mark the reference line on the ground along the perimeter of your house where you will be installing the dripline trench. STEP 3. Outside boundary. Measure and mark 12” from the reference line away from your house. This the outside boundary line for excavation. STEP 4. Inside boundary. Measure and mark 6” from the reference line toward your house. This is the inside boundary line for excavation. STEP 5. Determine materials needed. CRUSHED STONE. Calculate the volume of the trench in cubic feet by using the calculation below. If needed, convert cubi c feet to cubic yards by multiplying cubic feet by 0.037. TRENCH LENGTH (ft) x TRENCH WIDTH (ft) x TRENCH DEPTH (ft) = TRENCH VOLUME (ft3) LANDSCAPE FABRIC. Purchase enough landscape fabric to extend twice the length of the trench. PERFORATED PIPE. Purchase enough perforated pipe to extend the length of the trench. i N stallatio N STEP 1. Dig a trench at least 8” deep between the outside and inside boundary lines marked along the perimeter of your house. Slope the bottom of the trench away dripliNe iNfiltratioN treNCH Soffit EQUIPMENT & MATERIALS r Measuring tape r Shovel r 1/2” to 11/2” Crushed stone r Non-woven geotextile or landscape fabric OPTIONAL r Perforated plastic pipe r String or spray paint A dripline infiltration trench collects and infiltrates stormwater from your roof until it soaks into the ground. It helps control stormwater from running off of your property. 18 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs from the house so that water will drain away from the foundation (Figure 1). STEP 2. Line the sides with a non-woven geotextile fabric to extend the life of the trench. STEP 3. Fill with stone. For Well Drained Soils: Fill the trench with stone. Fill the trench with 1/2” to 11/2” crushed stone until it is about 3” below the ground level. Place a piece of non-woven geotextile fabric over the stone layer and fill the remaining three inches with additional stone (Figure 1). For Slowly Draining Soils: Fill the bottom 1” - 2” of the trench with crushed stone. Lay a 4” perforated pipe with the holes facing up along the trench. The end of the pipe should either outlet to a vegetated area with a splash guard to prevent erosion or to another treatment practice such as a dry well or a rain garden. The pipe should be sloped toward the outlet so the water easily flows out of the pipe. Consider screening or adding another type of rodent guard on the exposed end of the pipe to prevent animals from nesting and clogging the pipe. Fill the trench with 1/2” to 11/2” crushed stone until it is about 3 inches below the ground level. Place a piece of non-woven geotextile fabric over the stone layer and fill the remaining three inches with additional stone (Figure 2). STEP 4. OPTIONAL: Extend stone to foundation. As material allows, spread a layer of stone all the way to the edge of your foundation. This creates a cleaner appearance and reduces the need for vegetation between the trench and your foundation. m ai N te N a NC e INSPECT: Periodically and after rain events, inspect the practice for any obvious signs of stress or potential failure. Remove accumulated debris and sediment as needed. Check for ponding or poorly draining water - this can be a sign of clogging. OTHER MATERIALS: Trenches lined with non-woven geotextile fabric will require less frequent maintenance, but will still clog over time. Ponding or slowly draining water can be a sign of clogging. The stone and fabric, if used, will need to be washed or replaced to remove the accumulated sediment and debris. d esi GN r efere NC e Maine Department of Environmental Protection. Conservation Practices for Homeowners. Fact Sheet Series. May 2006. 3-6” stone Figure 1. Profile for well drained soils. 18” 5” fabric 5 - 10”stone Figure 2. Profile for slowly draining soils. 18” 1-2” stone 4” perforated pipe surrounded by stone fabric 3-6” stone 19 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs s izi NG a N d d esi GN STEP 1. Observe Driveway. Observe your driveway during a rain storm to determine how stormwater runoff flows across it. Depending on the volume of runoff and where it flows, you may only need an infiltration trench along one side or only a portion of your driveway. STEP 2. Determine Width. Decide the width of the trench you want to install. It should be between 12” and 18”, as space allows. Mark the trench width (12” - 18”) along the edge of your driveway where you will be installing the trench. This is the boundary line for excavation. STEP 3. Determine materials needed. Crushed stone. Calculate the volume of the trench in cubic feet by using the calculation below. If needed, convert cubic feet to cubic yards by multiplying cubic feet by 0.037. TRENCH LENGTH (ft) x TRENCH WIDTH (ft) x TRENCH DEPTH (ft) = TRENCH VOLUME (ft3) Landscape fabric. Purchase enough landscape fabric to extend twice the length of the trench. Perforated pipe. Purchase enough perforated pipe to extend the length of the trench. i N stallatio N STEP 1. Dig trench. Dig a trench at least 8” deep between the edge of your driveway and the excavation boundary line marked along the perimeter of your driveway. Slope the bottom of the trench away from the driveway, if possible, so that water will drain away from the driveway. EQUIPMENT & MATERIALS r Measuring tape r Shovel r 1/2” to 11/2” Crushed stone r Non-woven geotextile or landscape fabric OPTIONAL r Perforated plastic pipe r String or spray paint drivewaY iNfiltratioN treNCH A driveway infiltration trench collects and infiltrates stormwater from your driveway allowing it to soak into the ground. It helps reduce stormwater runoff. 20 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs STEP 2. Line with fabric. To extend the life of the trench, line the sides with non-woven geotextile fabric. STEP 3. Fill with Stone. For Well Drained Soils: Fill the trench with stone. Fill the trench with 1/2” to 11/2” crushed stone until it is about 3” below the ground level. Place a piece of non-woven geotextile fabric over the stone layer and fill the remaining three inches with additional stone (Figure 1). For Slowly Draining Soils: Fill the bottom 1” - 2” of the trench with crushed stone. Lay a 4” perforated pipe with the holes facing up along the trench. The end of the pipe should either outlet to a vegetated area with a splash guard to prevent erosion or to another treatment practice such as a dry well or a rain garden. The pipe should be sloped toward the outlet so the water easily flows out of the pipe. Consider screening or adding another type of rodent guard on the exposed end of the pipe to prevent animals from nesting and clogging the pipe. Fill the trench with 1/2” to 11/2” crushed stone until it is about 3 inches below the ground level. Place a piece of non- woven geotextile fabric over the stone layer and fill the remaining three inches with additional stone (Figure 2). m ai N te N a NC e INSPECT: Periodically and after rain events, inspect the practice for any obvious signs of stress or potential failure. Remove accumulated debris and sediment as needed. Check for ponding or poorly draining water - this can be a sign of clogging. OTHER MATERIALS: Trenches lined with non-woven geotextile fabric will require less frequent maintenance, but will still clog over time. Ponding of slowly draining water can be a sign of clogging. The stone and fabric, if used, will need to be washed and replaced to clean out the accumulated sediment and debris. d esi GN r efere NC e Maine Department of Environmental Protection. Conservation Practices for Homeowners. Fact Sheet Series. May 2006. 3-6” stone Figure 1. Profile for well drained soils. 18” 5” fabric 5 - 10”stone Figure 2. Profile for slowly draining soils. 18” 1-2” stone 4” perforated pipe surrounded by stone fabric 3-6” stone 21 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs drY well s izi NG a N d d esi GN STEP 1. Choose the location. A good location for a dry well is an area that can receive and infiltrate large amounts of concentrated runoff, such as from a roof valley or gutter downspout. The area should be large enough to accommodate the dry well and should have good separation to groundwater. If you dig and the hole starts filling with water, you should choose another location. STEP 2. Infiltration test. Perform a simple perc test to determine the ability of the soil to infiltrate water (allow it to soak in and drain through the soil). Dry wells should only be installed on soils that will drain within 24 hours. To conduct a simple perc test, use the following steps. a. Using a shovel or a post hole digger, dig a 1-foot deep hole. b. Fill the hole with water and allow it to drain completely (NOTE: if the hole fills with water on its own or if water is still in the hole after 24 hours, choose a new location). c. Fill the hole with water a second time and place a ruler or yard stick in the hole. Note the water level and time. After 15 minutes, check the water level again and note the new water level. Multiply the change in water level by 4 to get the number of inches of infiltration in an hour. If the hole infiltrates at least 1/2” of water per hour, it is suitable for pervious pavers. STEP 3. Calculate runoff volume. To determine how large the dry well needs to be, you need to know the volume of water it will receive during a typical rain storm. Most EQUIPMENT & MATERIALS r Measuring tape r Shovel r 1/2” to 11/2” Crushed stone r Non-woven geotextile fabric or landscape weed fabric for smaller projects OPTIONAL r PVC or other plastic piping r String or spray paint r Splash guard r Gutter downspout extension TIP: One inch of rain will produce about 62 gallons of runoff for every 100 ft 2 of drainage area. A dry well collects runoff from gutter downspouts, roof valleys, and other areas where water concentrates and flows. They help infiltrate runoff and reduce erosion. Open-topped dry well 22 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs storms in New Hampshire produce one inch or less of rain so designing for a 1-inch storm will capture most runoff as well as the dirtiest “first flush” of larger storms. Complete steps a. through d. to calculate runoff volume. a. C alculate the square footage of the drainage area: DRAINAGE AREA LENGTH (ft) X DRAINAGE AREA WIDTH (ft) = DRAINAGE AREA (ft2) b. If multiple areas will be directed to the dry well, calculate the square footage of each and add them together . c. Find the volume of stormwater from the total drainage area for a 1-inch storm by dividing the drainage area by 12 to convert the inches to feet: TOTAL DRAINAGE AREA (ft2) ÷ 12 = STORMWATER VOLUME (ft3) STEP 4. Design how runoff will enter the dry well. For Open-Topped Dry Wells: Roof downspouts can direct runoff into the top of the of the dry well by simply directing and extending gutter downpouts. Shallow swales or trenches can also be used to direct runoff from the downspout into this type of dry well. For Buried Dry Wells: Roof downspouts can be buried under ground and extended through a flexible pipe/ trench into the dry well. This allows the dry well to be buried and planted. Consider installing a flow diverter to allow you to easily disconnect the gutter from the dry well during winter months if you are concerned with freezing conditions. STEP 5. Determine the dimensions. Dry wells are typically 3 feet deep and should be designed to accommodate the stormwater volume (determined in Step 2). Adjust the dimensions of your dry well as needed to fit your site. a. Calculate the surface area of your dry well in ft2: STORMWATER VOLUME (ft3) ÷ 3ft (depth) = DRY WELL AREA (ft2) b. Identify any limitations on the length or width of the dry well in the chosen location. For example, tree roots, large rocks, or other structures could be limiting factors. Use the most limiting dimension to help determine the shape. For example, if the dry well area should be 12ft2 and it can only be 2 feet wide, it will need to be 6 feet long to accommodate the stormwater volume. STEP 6. Determine materials needed. Crushed stone: To calculate the volume of stone needed, use the dimensions of the TIP: Crushed stone takes up about 60% of the space in a dry well, leaving about 40% for water storage. A typical dry well is 3’x3’x3’. This will store about 11ft3 of water, which is equal to the runoff from a 132ft2 drainage area in a storm that produces one inch of rain. Buried dry wells blend into the landscape, support pollinators, and can increase plant diversity. 23 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs dry well, determined in Step 4 above. If burying the downspout, you will also need to purchase extra stone to fill in the trench around the inlet pipe. If needed, convert cubic feet to cubic yards by multiplying cubic feet by 0.037. Landscape fabric: To prevent migration of soil from the sides of the dry well into the stone reservoir, it is recommended to line the sides of the dry well with landscape fabric. For ease of maintenance or if your dry well will be buried, you may also want to line the top of the stone with landscape fabric. Variations on dry well design are discussed below. Downspout adapter and flexible pipe: If you are trenching your downspout into the dry well underground, you will need to purchase a downspout adapter and flexible pipe, which can be purchased at most local hardware stores. i N stallatio N STEP 1. Mark the boundaries. Once you have determined the location and dimensions, clearly mark the boundary of your dry well to identify where to dig. Landscape flags, string, or spray paint work well. STEP 2. Dig the dry well . Excavate down 3’ within the marked dry well boundary. Consider separating the good topsoil from the deeper soil layers to use as a planting bed if you are installing a buried dry well. STEP 3. Dig the trench. If your dry well will be buried, also dig a trench to bury your inlet pipe from the gutter downspout to the dry well. Carefully remove and set aside the sod growing over the trench to use later to re-cover once it is complete. Be sure to pitch the trench toward the dry well so that the water easily drains from the gutter to the dry well and doesn’t back up. STEP 4. Shape the bottom. Slope the bottom of the dry well away from your house or other buildings so that water drains away from the foundation. STEP 5. Line with landscape fabric . Extend the life of the dry well by lining the sides with non-woven landscape fabric. For Open-Topped Dry Wells STEP 6. Fill with stone. Fill the excavated dry well with crushed stone to within 3” of the ground surface. STEP 7. Cover with landscape fabric. Fold a flap of filter fabric over the top of the crushed stone. STEP 8. Top coat with stone. Fill to ground level with stone. STEP 9. Connect to dry well. Extend gutter downspout to the dry well. A splash guard, flat paver, or flat stone can be placed under the downspout to soften the force of the water entering the dry well. If using a shallow swale or trench, dig it out and stabilize the trench with crushed stone, river rocks, or plants per your design. For Buried Dry Wells STEP 6. Fill with stone. Fill the excavated dry well with crushed stone to the depth where the pipe from the gutter will be laid. Be sure to place the pipe deep enough 24 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs to allow for a 6” planting bed or sod layer on top. STEP 7 (optional). Install the flow diverter. Flow diverters allow you to easily direct flow from your gutter downspout into your dry well during warm seasons. They can be closed during winter month, which allows your gutter to operate normally. To install the diverter, cut the gutter with a hand saw and install per manufacturers instructions at a height that allows the water to flow from the diverter into the dry well. STEP 8. Connect pipe to dry well. Attach the pipe to the downspout or flow diverter, if using one. Lay the pipe in the trench with the outlet near the center of the well. Use crushed stone and a level to make sure it is pitched toward the dry well so it will drain. STEP 9. Continue to Fill with Stone. Fill with stone to within 6” of the ground surface. STEP 10. Cover with Landscape Fabric. Fold a flap of filter fabric over the top of the crushed stone. STEP 11. Top coat with soil. Cover landscape fabric with a 6” planting bed of soil. Densely plant buried dry wells with native groundcover, grasses, or other perennials. Fertilize sparingly and only as needed. m ai N te N a NC e INSPECT: Seasonally and after large storms. Look for signs of clogging such as ponding at the surface or water backing up into gutter if your downspout is buried. CLEAN OUT: The use of filter fabric will extend the life of dry wells, but will eventually clog over time. If clogging occurs, remove and wash or replace stone and fabric. PLANT CARE: If your dry well is buried, inspect, prune, thin, or replace plants as needed on the surface of the dry well. d esi GN refere NC e Maine Department of Environmental Protection. Conservation Practices for Homeowners. Fact Sheet Series. May 2006. 25 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs iNfiltratioN steps Infiltration steps slow down and infiltrate runoff on moderate slopes to reduce erosion and define walking paths. They are well-suited for shorefront properties. s izi NG a N d d esi GN STEP 1. Measure the slope. Measure the overall rise and run of the area in inches (Figure 1). STEP 2. Determine the number of steps needed. Divide the rise of the slope (measured in Step 1) by the height of the timber (6” unless you are using different sized timbers) and round to the nearest whole number. This is the number of steps you will need. RISE ÷ TIMBER HEIGHT = NUMBER OF STEPS STEP 3. Determine step depth (tread). Divide the run of the slope by the number of steps (figured in Step 2). The depth of the step tread is flexible, but should be at least 15” to be comfortable to walk up and down. RUN ÷ NUMBER OF STEPS = DEPTH OF STEP TREAD STEP 4. Determine the width of the steps. A comfortable width is usually 4 feet, but depending on the topography, trees, or other site conditions, a wider or narrower step may be desired. STEP 5. Determine materials needed. Once you know the number of steps that you need, their width and tread depth, you can determine the length of timber and the amount of steel rebar that you will need. Figure 1 EQUIPMENT & MATERIALS r Measuring tape r Shovel r Sledge hammer r 4 Wooden stakes r String or spray paint r 3/4” crushed stone or pea stone r Non-woven geotextile fabric r 6” x 6” pressure treated timbers (or similar sized material such as granite or logs r 18” long pieces of 1/2” diameter steel rebar r Level r Power drill with 1/2” drill bit r 12” galvanized spikes 26 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs Timbers: If you are using side timbers, add the length of each side timber (the tread depth) to the step width to get the total length of timber you’ll need per step. As a guide, use the following equations to estimate the length (in feet) of timber material you will need: STEP WIDTH + (2 X TREAD DEPTH) = TIMBER LENGTH PER STEP TIMBER LENGTH PER STEP X NUMBER OF STEPS = TOTAL TIMBER LENGTH Rebar: If you two-piece any of the side timbers together, plan to install rebar at each end of the timber where the pieces join. STEPS: Two 18” lengths of 1/2” diameter steel rebar for each step. SIDE TIMBERS (if using): Six 18” lengths of 1/2” diameter steel rebar for each step. Landscape Fabric: Multiply the number of steps by the square footage of each step to estimate the total square footage of fabric needed. For example: 4 steps X 4’ width X 1.5’ tread = 24 ft2 of landscape fabric needed. Crushed Stone or Pea Stone: Multiply the number of steps to be back-filled by the volume of step. Calculate the volume for each step by multiplying the step’s width, tread, and depth. For example: 4 steps X 4’ width X 1.5’ tread X 0.5’ deep = 12 cubic feet of stone are needed. You can convert cubic feet to cubic yards by multiplying by 0.037. i N stallatio N STEP 1. Stake perimeter. Stake out the perimeter of the stairway by driving a stake into the ground at each corner of the stairway and stretching string between them (Figure 2). STEP 2. Mark areas to be excavated. Determine the areas that need to be excavated for each step. Using a measuring tape and starting from the string at the bottom of the slope, measure and mark the depth of the each step until you reach the string at the top of the slope. Use spray paint, sand, or flour to mark the depth of each step (Figure 2). STEP 3. Excavate first step. Starting at the bottom, dig a trench for the first riser timber (this will be more like a shallow groove in the ground). Next, if using side timbers, dig trenches for the side timbers, which should be long enough to extend 6” past the next step’s riser. Check to make sure the trenches are level (Figure 3). TIP: Side timbers may not be needed if the steps are in a pathway where the surrounding land is higher. In this case, extend the timbers into the adjacent banks so water will not go around the steps. Figure 2 Figure 3 27 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs STEP 4. Prepare materials. Cut the timbers to the appropriate length. For each step, cut one riser timber as long as the step width and 2 timbers as long as the step depth for the side timbers (remember that each step should extend 6” past the next step’s riser.) Drill 1/2” diameter holes approximately 6” from the ends of each timber (Figure 4). STEP 5. Position timbers. Position the timbers in the step and remove or add soil as needed to level them (Figure 4). STEP 6. Anchor timbers. Drive the steel rebar through the drilled holes on the end of each timber and into the ground. Make sure the rebar is level with the timber surface or slightly recessed since the edges may be sharp (Figure 4). STEP 7. Dig and level inside step. Shovel out the soil inside the step to create a surface roughly level with the bottom of the timbers. Additional soil can be removed to provide more area for infiltration if desired. Make sure to dispose of excavated soil in a place where it will not wash away (Figure 4). STEP 8. Build second step. To build the next step, measure from the front of the first riser timber and mark the tread depth on the side timbers with a pencil. Align the front of the second step riser timber with the pencil lines on the side timbers of the step below. Secure the riser timber to the side timbers using 12” galvanized spikes (Figure 5). To make it easier to drive the galvanized spikes into the timber, you can pre-drill holes to about 5” deep. STEP 9. Excavate side timbers. Set and anchor side timbers by driving the steel rebar through the drilled holes on the end of each timber into the ground (Figure 5). STEP 10. Dig and level inside step. Shovel out the soil inside the step to create a surface roughly level with the bottom of the timbers the same as in Step 7. STEP 11. Repeat. Repeat Steps 8 through 10 for each remaining step. When installing the top step, cut the side timbers 6” shorter than the ones on the lower steps - these timbers do not need the extra length since no stairs will rest on them. STEP 12. Fabric and backfill. Lay down landscape fabric and backfill with stone. a. Line the area inside each set of timbers with non-woven geotextile fabric. Make sure the fabric is long enough to extend a few inches up the sides of the timbers. b. Fill each step with 3/4” crushed stone or pea stone until it is about 1” below the top of the timber (Figure 6). c. Seed and/or mulch bare soil adjacent to the steps. TIP: Most lumber supply stores have a cutting station to cut timbers to the correct length if you do not have a saw. TIP: Place the galvanized spikes where they will not interfere with the rebar. Figure 4 Figure 5 Figure 6 28 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs t o r etrofit e xisti NG s teps Existing steps can be retrofit to improve infiltration by removing the current material and filling in according to Step 12. TIP: If the timbers are not firmly secured, drill 1/2” diameter holes six inches from the ends of each timber. Drive 1/2” diameter, 18” long steel rebar through the holes with a sledge hammer. For gentle slopes, wooden stakes or large rocks can also secure the timbers. m ai N te N a NC e INSPECT: Seasonally and after large storms, look for signs of erosion or clogging such as ponding at the surface or accumulated sediment. CLEAN OUT: If clogging occurs, remove and wash or replace stone and fabric. Remove any vegetation growing on the steps if not included in the design. REPLACE: Replace timbers if damaged or rotted, as needed. d esi GN r efere NC e Maine Department of Environmental Protection. Conservation Practices for Homeowners. Fact Sheet Series. May 2006. Figures adapted with permission from the Maine Department of Environmental Protection. Native shrubs, perennials, grasses, and groundcover enhance the function of these infiltration steps to provide multiple ecological benefits. 29 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs pervious walkwaYs & patios s izi NG a N d d esi GN STEP 1. Identify installation area. Determine the areas where you will be installing pervious pavers. Pervious pavers are best for areas with slopes of less than 2%. There should be a minimum of 2’ between the bottom of the gravel base and bedrock or the water table. STEP 2. Infiltration test. Perform a simple perc test to determine the ability of the soil to infiltrate water (allow it to soak in and drain through the soil). Pervious pavers should only be installed on soils that will drain within 24 hours. To conduct a simple perc test, use the following steps. a. Using a shovel or a post hole digger, dig a 1-foot deep hole. b. Fill the hole with water and allow it to drain completely (NOTE: if the hole fills with water on its own or if water is still in the hole after 24 hours, choose a new location). c. Fill the hole with water a second time and place a ruler or yard stick in the hole. Note the water level and time. After 15 minutes, check the water level again and note the new water level. Multiply the change in water level by 4 to get the number of inches of infiltration in an hour. If the hole infiltrates at least 1/2” of water per hour, it is suitable for pervious pavers. Pervious pavers look like traditional pavers, but are able to absorb and store rain and snowmelt to reduce runoff from your property. TIP: Pervious pavers come with manufacturer instructions for the type and depth of sub-base material. If the information in this fact sheet differs from the manufacturer’s instructions, follow the manufacturer’s instructions. EQUIPMENT & MATERIALS r Measuring tape r Shovel r Rake r Broom r 11/2” crushed stone r 3/8” pea stone r Non-woven geotextile fabric r Tamper or roller r Pervious pavers r Level 30 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs STEP 3. Determine materials needed. a. Calculate the area of the new or existing walkway or patio that you will be installing with pervious pavers by multiplying the length (in feet) and width (in feet) of the area to be paved. If the area you are paving is not a simple square or rectangle, sketch the area where the pavers will be installed on a piece of paper, write down the corresponding measurements, and bring it to your local landscape supply yard or store where you will be purchasing the pavers. They will be able to help you determine how many pavers you need. b. Sub-base materials (Figure 1) are the gravel and pea stone layers that go under the pavers. These materials provides a reservoir for stormwater before it soaks into the ground underneath. You should have a minimum depth of 12” of 11/2” diameter crushed stone and 6” of 3/8” pea stone for your sub- base. Use the following equations to determine the amount of sub- base materials you will need (multiplying by 0.037 converts cubic feet to cubic yards): CRUSHED STONE: PAVEMENT AREA (ft2) x 1ft x 0.037 = YARDS PEA STONE: PAVEMENT AREA (ft2) x 0.5ft x 0.037 = YARDS i N stallatio N STEP 1. Prepare the Installation Site. Remove any existing walkway or patio material. This may require renting a jackhammer or other equipment such as a backhoe. Mark the location of the walkway or patio with either landscaping paint or a string line on either side. STEP 2. Excavate. Excavate the site approximately 20” deep, depending on the type of paver you’re using. Smooth the area you’ve excavated with a rake. STEP 3. Lay the Sub-base Material and Pavers. a. Spread the crushed gravel over the excavated dirt. The depth of the gravel should be 12” or per manufacturer’s instructions. Compact with a roller or tamper. b. Check paver manufacturers instructions for use of non-woven geotextile fabric over the crushed gravel. c. Spread the pea stone over the fabric, if using. The depth of the pea stone should be 6” or per manufacturer’s instructions. Compact with a roller or tamper. Level the surface to make the pavers easier to install. Figure 1. Pervious walkway profile. 31 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs d. Install the pavers on top of the pea stone and use a level to make sure they are installed uniformly. Most pervious pavers have tabs on the edges to create proper spacing between them. e. Once the pavers are installed, spread more pea stone over the top and use a push broom to work the pea stone into the space between the pavers. m ai N te N a NC e INSPECT: Seasonally and after large storms, look for signs of clogging such as ponding at the surface or accumulated sediment. CLEAN OUT: If clogging occurs, remove and wash or replace pea stone and fabric. Remove any vegetation growing on the steps if not included in the design. Refer to manufacturers instructions for pressure washing or vacuuming. d esi GN r efere NC e Low Impact Development Center. Permeable Paver Specification. 1995. NH Department of Environmental Services. Permeable Pavement Demonstration Brochure. 2010. 32 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs raiN barrel EQUIPMENT & MATERIALS r Purchased or home- made rain barrel (food grade) r Downspout diverter (purchased or made) r Shovel r Cinder block or other elevated base r Level OPTIONAL r Soaker hose r Crushed stone r Mulch r Splash guard s izi NG a N d d esi GN STEP 1. Observe your roof runoff. Note where you have existing roof gutter downspouts, roof valleys or edges that drain large amounts of water. STEP 2. Calculate the runoff volume. To determine how many rain barrels you need and whether you should designate an area to direct the rain barrel overflow, you need to know the volume of water the barrels will receive during a typical rain storm. Most storms in New Hampshire produce one inch or less of rain so designing for a 1-inch storm will capture most of the runoff volume as long as the barrels are emptied between storms. Complete steps a. through d. to calculate runoff volume. a. C alculate the square footage of the drainage area: DRAINAGE AREA LENGTH (ft) X DRAINAGE AREA WIDTH (ft) = DRAINAGE AREA (ft2) b. If multiple areas will be directed to the rain barrel, calculate the square footage of each and add them together . c. Find the volume of stormwater from the total drainage area for a 1-inch storm by dividing the drainage area by 12 to convert the inch to feet: TOTAL DRAINAGE AREA (ft2) ÷ 12 INCHES = STORMWATER VOLUME (ft3) d. Most rain barrel s give the holding capacity in gallons . Convert the cubic feet to gallons by multiplying by 7.48. STORMWATER VOLUME (ft3) X 7.48 GALLONS = STORMWATER VOLUME (gallons) A rain barrel captures rainwater from your roof to reduce runoff from your property and provide you with water for lawns, gardens, and indoor plants to use in dry weather. 33 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs TIP: If more than one rain barrel will be needed to capture a one-inch storm: • Rain barrels can be linked together so that the overflow from one goes into the next. • You can plan to capture smaller storms and designate an area to receive overflow. TIP: Your rain barrel must be secured on a firm, level surface. A full, 55-gallon rain barrel weighs over 400 pounds. STEP 3. Determine how many rain barrels are needed. Attempt to capture the volume from a one-inch storm. STORMWATER VOLUME (gallons) ÷ RAIN BARREL STORAGE CAPACITY (gallons) = NUMBER OF RAIN BARRELS NEEDED STEP 4. Address the overflow. Be sure to note where the overflow will go during large storms. Avoid directing the overflow next to building foundations. Plan to use a splash guard, install a soaker hose, or build a slight swale to direct overflow away from your home and into an area where it can be absorbed, such as a naturally vegetated area, a rain garden, or dry well. i N stallatio N STEP 1. Level the area. Once you have determined where you want your rain barrels to go, level the ground surface. You can use crushed stone or mulch to stabilize the ground. STEP 2. Install blocks or stand. Elevating the rain barrel is necessary to allow room for a watering can, bucket, or hose attachment under the spigot. Elevating the barrels will also create stronger water pressure. Place the blocks or other materials to create a stand on the leveled ground and recheck for level. Adjust as needed to achieve level. STEP 3. Connect the downspout to the rain barrel. Flow diverters allow you to easily direct flow from your gutter downspout into your rain barrel during warm seasons. They can be closed during winter month, which allows your gutter to operate normally. To install the diverter, temporarily place the rain barrel on the blocks to mark where the diverter needs to be installed. Cut the gutter with a hand saw and install the diverter per the instructions, at a height that allows the water to flow from the diverter into the barrel. If not using a flow diverter, the gutter downspout can be directed or connected directly to the barrel. STEP 4. Install the rain barrel. a. Place the rain barrel on the blocks or stand. b. Direct flow from gutter downspout or diverter into the barrel. c. Cover the open top of the rain barrel with screen to prevent mosquitoes from breeding in the standing water and to reduce the amount of debris entering the barrel. Most rain barrels that you purchase pre-made will come with a screened cover. d. Direct the overflow hose from the rain barrel to a vegetated area or another stormwater practice, where it can soak into the ground. 34 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs m ai N te N a NC e INSPECT: Check after storms to determine how soon you need to empty the barrel. Remember that a rain barrel only works if it has space to contain more water. EMPTY: Empty the rain barrel between storms or, at a minimum, when full. The water can be used on perennial gardens, house plants, and other non-potable or non- drinking water needs. Carefully consider what you water with your rain barrel. This water has the potential to contain pollutants from your roof that you may not want to come in contact with vegetables or other edible crops. CLEAN: Keep the screen clear of debris and clean with a soft brush as needed. Periodically clean out the inside of the barrel if debris has collected. Keep gutters and downspouts clean and clear to prevent debris, such as leaves and pine needles from entering the rain barrel. WINTER STORAGE: It is recommended in New Hampshire that you completely empty your rain barrel and store it indoors through freezing winter months. When the rain barrel is removed for the season, the gutters and downspouts should be returned to their normal function to drain the roof during winter storms. This can be done by closing or removing the diverter and extending the downspout back to the ground. b uild Y our o w N r ai N b arrel Pre-made rain barrels are available in many sizes and styles. They range in price from $50 to over $200. To save money, you can make your own rain barrel out of a food grade drum and plumbing parts that you can find at most hardware stores. An internet search of “How do I make a rain barrel” will result in a long list of how-to sites and videos like this one http://www.instructables.com/id/Rainwater-harvesting-Rain- Barrel-DIY/?ALLSTEPS#step1. Whatever instructions you follow, we recommend using a food grade drum and avoiding trash barrels, which may not be sturdy enough to stand up to the pressure of being full of water. d esi GN r efere NC es Vermont Department of Environmental Conservation. Low Impact Development Guide for Residential and Small Sites. December 2010. 35 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs raiN GardeN d esi GN C o N sideratio N s STEP 1. Site Constraints. Identify site constraints in the area that the rain garden will be located such as: • High water table - rain gardens should not be placed in persistently wet areas or areas where puddles regularly form. • Underground obstructions such as gas or electrical lines, other utilities, structures or bedrock. Contact DigSafe 72 hours in advance of your project. • Property boundaries and local setbacks. STEP 2. Setbacks. Be sure to locate the rain garden: • At least 10 feet away from buildings with basements to prevent seepage into the basement. • At least 15 feet away from septic tank or leach field. • Away from tree roots and drinking water wells. STEP 3. Infiltration test. Perform a simple perc test to determine the ability of the soil to infiltrate water. Rain gardens should only be built in areas where a simple perc test drains completely within 24 hours. To complete a simple perc test: a. Using a shovel or a post hole digger, dig a 1-foot deep hole. b. Fill the hole with water and allow it to drain completely. If the hole fills with water on its own or if water is still in the hole after 24 hours, choose a new location. c. Fill the hole with water a second time and place a ruler or yard stick in the hole. Note the water level and time. After 15 minutes, check the water level again and note the new water level. Multiply the change in water level by 4 to get EQUIPMENT & MATERIALS r Calculator r Measuring tape r Spray paint r Yard stick r 6-12 Stakes r 2-4 long stakes (4’) r String r Shovels r Carpenter’s level r String level r Rakes r Compost/Woodchips r Mulch r Crushed stone r Flat stones or pavers r Tarp(s) r Wheel Barrow(s) r Plants A rain garden is a sunken, flat-bottomed garden that uses soil and plants to capture, absorb, and treat stormwater. This helps to reduce stormwater runoff and recharge groundwater. 36 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs the number of inches of infiltration in an hour. A rate of 1/2” or more per hour indicates that it will drain within 24 hours. s izi NG Use the following steps to determine the dimensions of the rain garden. Use Table 3 to organize the information. STEP 1. Total drainage area. Identify the surface(s) that will drain to the rain garden. Multiple the length by the width to get the drainage area in square feet. DRAINAGE AREA LENGTH (ft) X DRAINAGE AREA WIDTH (ft) = DRAINAGE AREA (ft2) If more than one surface will contribute runoff to the rain garden, add them together. For example, if two roof areas are collected by a downspout that will drain to the rain garden, add the two roof areas together. STEP 2. Soil type. The size of the rain garden is dependent on the soil type. Estimate your soil type by performing a ribbon test using the following steps: a. Grab a handful of moist soil and roll it into a ball in your hand. b. Place the ball of soil between your thumb and the side of your forefinger and gently push the soil forward with your thumb, squeezing it upwards to form a ribbon about 1/4 inch thick. c. Try to keep the ribbon uniform in thickness and width. Repeat the motion to lengthen the ribbon until it breaks under its own weight. Measure the ribbon and compare it to Table 1. STEP 3. Slope. Find the slope of the land where the rain garden will be located. Slopes should be less than 12%. Follow the steps below to determine slope. a. Place one stake at the uphill end of the rain garden area and another at the downhill end as illustrated in Figure 1. b. Tie a string to the uphill stake at ground level. Using a string level, level the string between the two stakes. c. Measure the length of the string between the stakes. This is the run or length. d. On the downhill stake, measure the height from the ground to the string. This is the rise or height. e. Divide the rise by the run and then multiply the result by 100. This is the slope. SLOPE (%) = (RISE ÷ RUN) X 100 Soil Type Ribbon Length (inches) Sand No ribbon will form Silt Weak ribbon <1.5” Clay >1.5” Table 1. Soil type based on ribbon test. Figure 1. Determine the slope of the landscape before digging. uphill stake string must be level downhill stake 37 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs STEP 4. Ponding depth. Use the slope to determine the corresponding rain garden ponding depth in Table 2. The ponding depth is the distance between the top of the mulch layer and the top of the rain garden outlet. STEP 5. Size Factor. Match the ponding depth to the appropriate soil type in Table 2 to find the rain garden size factor. For example, if your slope is 6%, the corresponding ponding depth is 6 - 7 inches. If you have a silt soil, your corresponding size factor is 0.25. STEP 6. Rain garden area. Use the equation below to calculate the needed rain garden area in square feet. You can configure the shape and dimensions to best suit the site as long as it meets the total rain garden square footage. RAIN GARDEN SIZE FACTOR x TOTAL DRAINAGE AREA (ft2) = RAIN GARDEN AREA (ft2) STEP 7. Total depth to dig. a. A rain garden should have between 6” and 12” of planting bed material with 12” being ideal. The planting bed can include native soil, compost, and other soil amendments. Choose the planting bed depth for your rain garden. A 2” mulch layer is recommended to suppress weeds and prevent the soil from drying out in the first few years until the garden is established. b. The total depth to dig your rain garden is the sum of the ponding depth from Step 5, the planting bed depth (anywhere between 6” and 12”), and the mulch layer depth. PONDING DEPTH + PLANTING BED DEPTH + MULCH LAYER DEPTH = TOTAL DEPTH TO DIG d esi GN STEP 1. Identify staging and material disposal area(s). Identify an area on the site where delivered materials, such as stone, compost, and mulch, can be stored temporarily while the rain garden is being built. Also determine where excess materials, like sod and soil that is excavated from the rain garden, will be disposed. Slope ≤ 4%5 - 7%8 - 12% Ponding Depth 3-5 inches 6-7 inches 8 inches Soil Type Sand 0.19 0.15 0.08 Silt 0.34 0.25 0.16 Clay 0.43 0.32 0.20 Table 2. Ponding Depth & Size Factor START. Infiltration test (pass/fail) STEP 1. Total drainage area (ft2) STEP 2. Soil test (type) STEP 3. Slope (%) STEP 4. Ponding depth (inches) STEP 5. Size factor STEP 6. Rain garden area (ft2) STEP 7a. Planting bed depth (inches) STEP 7b. Total depth to dig (inches) Table 3. Rain Garden Sizing Information TIP: To maintain the ponding depth, it is best to design the berm to be a few inches higher than the outlet. If this makes the berm taller than 12”, you can increase the “depth to dig” and decrease the berm height. 38 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs STEP 2. Design the berm. If the rain garden is on a slope, a berm or low wall is needed on the downslope side of the rain garden to hold water in the garden. The berm should be the same height as the upslope edge of the garden to make the entire perimeter of the garden level. This creates the ponding area. The berm should be no more than 12” high in order to blend with the surrounding landscape and to be easier to maintain. This can limit the length of the rain garden in the direction of the slope. Table 4 shows the recommended rain garden length based upon the slope of the ground where the rain garden will be located. STEP 3. Consider the rain garden shape. Plan the shape of the rain garden to fit the situation. The rain garden can be any shape as long as it meets the square footage determined in Design Step 6. Restrictions include the length based on the berm height(recommended)and other potential site constraints that limit the length, width, or depth of the garden. STEP 4. Plan the inlet and outlet. a. Inlet. The location where runoff enters a rain garden is called the inlet. Whether stormwater runoff enters the rain garden through a gutter downspout, a swale, or as sheet flow, the inlet is susceptible to erosion and scouring during rain storms, To reduce erosion and scouring, the inlet should be reinforced with stone or gravel. A flat rock or paver can also be placed at the inlet, directly under where runoff enters the garden to help spread out the flow. b. Outlet. The location where water exits or overflows from a rain garden is called the outlet. While the rain garden is designed to contain most rain storms, the outlet provides a safe and controlled place for water to overflow during storms that produce a lot of rain. An outlet is usually created along a portion of the berm on the downslope side of a rain garden. An outlet is created by lowering a 1’ to 2’ wide section of the berm a couple of inches. Similar to the inlet, the outlet is susceptible to erosion and scour and needs to be reinforced with stone. STEP 5. Select plants and create a planting plan. Rain garden plants are not the same as water loving plants. Rain gardens have fluctuating wet and dry conditions and can have extended periods of dry soils between storms. Similar to planning any perennial garden, soil, light, wind, climate, and exposure to environmental stressors like road salt, need to be considered. Consider the following recommendations when selecting plants for your rain garden. • Refer to Native Plants for New England Rain Gardens on the Soak Up the Rain Slope 12%11%10%9%8%7%6%5%4%3%2%1%0% Rain Garden no longer than 8.5’9’10’11’12.5’14.5’16.5’20’25’33.5’50’100’NA Table 4. Suggested Rain Garden length for a 12” berm height. TIP: If the length of the rain garden cannot be adjusted, increase the “depth to dig” and decrease the berm height. 39 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs NH program website at http://soaknh.org/wp-content/uploads/2016/03/Native- Plants-for-NH-Rain-Gardens_20160322.pdf. • Choose New England native species to enhance the ecological function of the rain garden by supporting native species including birds and pollinators. • Avoid plants with lower basal leaves that may remain under water and become more susceptible to rot. • Use sturdy plants, such as Blue Flag Iris, where runoff enters the garden at the inlet. • Have the soil tested to determine pH, organic content, and other soil conditions to plan for soil amendments that you may need to encourage healthy plant growth. • Review the spacing suggestions for each plant and design your plan accordingly to give plants the space they need to grow to full maturity. • Create a bird’s eye view drawing of your planting plan to guide you when you plant and to help remind you of their placement when you inspect and maintain the rain garden. STEP 6. Determine materials needed. Once you know the area and depth to dig of your rain garden, follow the instructions below to approximate the amount of soil, compost, mulch and other materials that you may need. If needed, convert cubic feet to cubic yards by multiplying cubic feet by 0.037. 1. Decide how thick each material (soil, compost, mulch, etc.) should be. Material thickness: ________ inches 2. Use Table 5 to match the material thickness to the area covered per cubic yard of material. Area covered per cubic yard of material: ________ ft2 3. Determine the area (in ft2) the material needs to cover based on your rain garden size. Use the equation below to divide the size of the area to be covered by the area covered per cubic yard. The result is the number of cubic yards you will need. SIZE OF AREA TO BE COVERED ÷ AREA COVERED PER CUBIC YARD = CUBIC YARDS NEEDED Soil Amendments: The condition of the soil, organic content, pH, and other factors will determine the type and amount of soil amendments for your rain garden. The University of New Hampshire Cooperative Extension offers soil testing and will provide soil recommendations for residential rain gardens. More information on soil testing can be found at https://extension.unh.edu/Problem-Diagnosis-and-Testing-Services/ Soil-Testing. Be sure to indicate on the form that the test is for a residential rain garden. Plants: The number and type of plants will be dictated by the size of the rain gardens Material Thickness (inches) Area Covered (in ft2) per Cubic Yard (yd3) of Material 1”324 ft2 2”162 ft2 3”108 ft2 4”81 ft2 5”67 ft2 6”54 ft2 7”47 ft2 8”40 ft2 9”36 ft2 10”33 ft2 11”30 ft2 12”27 ft2 Table 5. Material thickness and coverage. 40 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs and localized sun/shade, soil, and climate conditions and should be specified in your planting plan. Stone: About a half of a yard of crushed stone is useful for securing the inlet and outlet and achieving the pitch of the inlet pipe from the gutter. Two or more 1ft2 or larger flat stones or pavers are useful for placing at the inlet. The outlet can also be reinforced with stones that you find as you dig out the rain garden area. i N stallatio N STEP 1. Define borders. Use string or spray paint to outline the shape of the rain garden. The berm, if needed, will be built outside of the outline. STEP 2. Remove sod. Remove the grass within the outlined area. You can either dig through the lawn or lay a tarp or sheet of black plastic within the rain garden area for several weeks to kill the grass. Herbicides are not recommended. STEP 3. Start digging. Remove the soil from within the rain garden area. Form a gentle slope along the edges as you dig. Lay out tarps to temporarily sort and store sod, top soil, and lower soil layers to use later in building the berm and preparing the soil planting bed. Consider the following: a. On a Slope: If the rain garden is on a slope, a berm will be needed. The sod and soil material excavated from digging the garden should be reserved to build the berm (Figure 2). b. On Level Ground: If the rain garden is on level ground, no berm is necessary and the excavated soil and sod can be removed or used elsewhere on the property. STEP 4. Set the berm height. Once you are close to having the entire garden area dug down to the “total depth to dig”, hammer stakes along the perimeter of the rain garden about 4-6 feet apart, starting with the highest edge and working around the garden. Attach a string to the base of the highest stake. Use a string level to mark the leveled height on each stake around the perimeter of the garden. This will be your berm height. STEP 5. Level the bottom. The rain garden must have a level bottom to encourage the water to spread evenly throughout. Once all of your stakes are marked with the berm height , use a leveled string and a yard stick or measuring tape to measure the distance from the bottom of the rain garden to the string throughout the rain garden. You may find that you need to dig out additional material or rake it out to get rid of high or low spots. STEP 6. Prepare the soil. Combine native soil, compost, and other soil amendments to Figure 2. Where to dig and put the soil on a sloped site. 41 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs create a planting bed between 6” and 12” deep. STEP 6. Prepare inlet. If your rain garden is capturing roof runoff from a gutter, you can dig a trench to bury your inlet pipe from the gutter downspout to the garden. Carefully remove the sod growing over the trench and set it aside to use as a cover once it is complete. Be sure to pitch the trench toward the rain garden so that the water easily drains from the gutter to the garden and doesn’t back up. You can use a carpenter’s level to do check the pitch. Inside the rain garden, stabilize the inlet area with crushed stone to prevent erosion and scour of the inlet. Place one or more flat stones or pavers directly under the inlet pipe to further reduce erosion and to prevent a channel from forming. STEP 7. Build berm and outlet. Using the marked stakes along the edge of the rain garden as a guide, use overturned sod and soil to build and shape the berm to the specified berm height. Designate a 1’ to 2’ section of the berm to be the outlet. The outlet should be a few inches lower than the rest of the berm height. After shaping the berm and the outlet, compact the soil. Reinforce the outlet with stone. STEP 8. Add planting bed materials. Before adding the planting bed materials into the rain garden, hammer tall stakes into the bottom of the rain garden and mark them with the planting bed depth, which should be between 6” to 12”. Use this line as a guide as you evenly distribute a mix of native soil, compost, and other amendments, as needed to create a planting bed. Mix well and be sure to place some planting bed material up the sloped sides of the rain garden so that they may also be planted. Rake the bed level. To avoid compacting the planting bed, work from the center of the garden outward. STEP 9. Plant. Place plants while still in their pots into the garden according to the planting plan. Make adjustments for spacing as needed. When you are ready to plant, remove one plant at a time from its pot and loosen the root ball with your fingers to encourage root growth. Plant to the same depth or slightly deeper than they were in the pot. STEP 10. Apply mulch. Apply a 2” layer of mulch over the entire rain garden to help retain moisture in the soil and to prevent weeds. STEP 11. Water thoroughly. Water thoroughly immediately after planting. Give the plants an inch of water every week for the first growing season. Once the plants have been established, water only as needed during extended dry weather. m ai N te N a NC e Rain garden maintenance is similar to the maintenance of any perennial garden, with a few extra tasks: INSPECT: After storms to verify the inlet and outlet are stable, no channels have formed, that plants are healthy, and that it is draining. Adjust and repair if needed. PLANT CARE: Weed and water as needed. Replace dead plants as needed. Cut back, prune, or divide plants when appropriate to encourage growth. CLEAN: If the rain garden is receiving runoff that contains sand or debris, such as from 42 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs a driveway or roadway, clean out accumulated materials as needed. d esi GN refere NC es Winooski Natural Resources Conservation District. The Vermont Rain Garden Manual “Gardening to Absorb the Storm” . 2009 Wisconsin Department of Natural Resources. Rain Gardens: A How-to Manual for Homeowners. 2003. Figures adapted from Wisconsin Department of Natural Resources. Rain Gardens: A How-to Manual for Homeowners. 2003. 43 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs A buffer is a vegetated area along a waterbody that provides shade, stabilizes slopes, and can help slow down and clean stormwater runoff. s izi NG a N d d esi GN STEP 1. Location. Buffers are beneficial along all types of surface waters from small streams to large rivers and bays. Vegetated buffers are located between the water and the built portions of a property, such as buildings, driveways, patios, and lawns. STEP 2. Check for local and state regulations. Be sure to follow any local or state regulations regarding working along shorelines. Permits and other permissions are often needed before doing any work close to surface waters or wetlands. STEP 3. Sizing. The larger the buffer, the more beneficial it is to water quality and ecosystem health. Even a thin strip of vegetation can help stabilize the shoreline. Consider the following when sizing your buffer: Length. Where possible, extend the buffer along the entire shoreline particularly in areas with steeper slopes. Consider the placement of walking paths through the buffer or installing additional practices such as water bars or infiltration steps to clearly define water access. Width. The wider the buffer, the greater the benefits. Table 1 suggests minimum buffer widths for water quality protection based on slope, however, even a narrow buffer will help to stabilize the shoreline, slow down runoff, and intercept falling rain. A buffer can vary in width being wide where space allows and narrower where necessary. Percent Slope Buffer Width (ft) 0 - 1%25 2 - 5%35 6 - 9%50 10 - 12%65 13 - 15%75 Note: Assumes buffer is not in wetland soils or ledge and that the area does not receive channelized flow. Modified by the University of New Hampshire from USDA NRCS. Table 1. Suggested buffer width by slope of land for water quality. veGetated buffer EQUIPMENT & MATERIALS r Measuring tape r Spray paint r Stakes r String r Shovels r Rakes r Compost/Woodchips r Mulch r Wheel Barrow(s) r Plants 44 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs Height. We often think that buffers on shorefront properties will block the view of the water, but a well-designed buffer can enhance the view by: • Layering the buffer with plants of various heights. Thoughtful placement of high and low vegetation can provide a screen where you want it, such as to block a neighbor’s house, and can frame views that you want to emphasize, like the open water or the location of sunrises or sunsets. • Selective removal of a few low branches can provide openings or “windows” to enjoy views from a house to the water without sacrificing privacy or the water quality and wildlife benefit of the buffer. Check local and state regulations before removing branches to make sure it is allowed. STEP 4. Plant selection. If creating a landscaped or enhanced buffer (see Table 2), selecting plants is similar to planning a perennial garden. Soil, light, wind, climate need to be considered. Salt tolerance may also need to be considered if your buffer will be next to a tidal waterbody or treated roadway. Consider the following recommendations when selecting plants for your vegetated buffer: • Select a variety of groundcover and herbaceous plants, shrubs, and trees appropriate for each zone within the vegetated buffer. • Refer to Landscaping at the Water’s Edge; An Ecological Approach for plant suggestions in the different buffer zones including salt-tolerant species that survive well in estuarine and coastal landscapes. • Refer to Native Plants for New England Rain Gardens at http://soaknh.org/wp- content/uploads/2016/03/Native-Plants-for-NH-Rain-Gardens_20160322.pdf for plant suggestions. While this guide was developed for rain gardens, many of the species would do well in buffer plantings. • Choose New England native species to enhance the ecological function of the buffer by supporting native species including birds and pollinators. • Consider the type of soil - sand, loam, clay - and select plants that prefer that soil type. If you are uncertain, look at what is already growing in the buffer zone on your property or nearby. As long as they are not invasive, add plants of the same species and feel confident they will likely grow well. • Review the spacing suggestions for each plant and design your plan accordingly to give plants the space they need to grow to full maturity. • Consider how you want the buffer to look and how much time you have to maintain it. Table 2 gives different approaches to establishing buffers. STEP 5. Paths and water access design. Access to the water through the buffer will likely be needed. Consider the following when planning pathways and access: • Avoid straight paths. Instead meander paths across the slope to prevent water from channelizing. • Use materials that can infiltrate runoff, such as pea stone with stepping stones, or consider materials that can be compacted and do not easily erode, such as stone dust. Incorporate water bars to shed water off of the path and into nearby vegetation. • Consider installing infiltration steps on steep slopes. 45 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs Natural Buffer Landscaped Buffer Enhanced Buffer • Designate an area to stop mowing/ maintaining and allow to grow • Plants will slowly grow and fill in - must watch for invasives • Takes the longest time • Often the simplest and least expensive approach • Plant purchased or transplanted native and other non-invasive plants • Quickest results - can be planted in phases • Often the most labor intensive • Often most expensive if plants need to be purchased • Combination of natural and landscaped - allow to grow in and add plants where desired • Good middle ground for effort, cost, time, and appearance Table 2. Approaches to establishing buffers. i N stallatio N STEP 1. Site preparation. It may be useful to mark the perimeter of the buffer area with stakes and string. This is particularly helpful to identify no-mow areas if you are going to allow a natural buffer to grow. If you created a planting plan, identify where plants will be placed and where your pathways and access points will meander through the buffer. In New Hampshire, fertilizer use is prohibited within 25’ of the reference line of a surface water, which is usually the high water mark, and is restricted to slow-release nitrogen and low- or no-phosphorus fertilizer within the 250’ waterfront buffer area. STEP 2. Planting landscaped or enhanced buffers. Use good planting practices, such as those listed below. Place plants while still in their pots into the buffer according to the planting plan. Make adjustments for spacing as needed. When you are ready to plant, remove one plant at a time from its pot. • Dig a hole twice as wide as the plant’s rootball and no deeper than the rootball. • Loosen and rough up the rootball before planting, especially those rootbound in the container, to encourage healthy root growth. • Plant as deep or just slightly deeper than they were in their pots. • If staking trees, make sure the trunks are allowed to sway in the wind. • Water: For landscaped or enhanced buffers, water just after planting and daily during the first week. During the second week, water every other day. Then, water twice a week through the first growing season. STEP 3. Mulching. Spread 2” to 3” of mulch over the root zone of plants to provide weed suppression, slow release of nutrients, and additional moisture retention. Be sure to keep mulch a few inches away from plant stems and shrub and tree trunks. 46 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs m ai N te N a NC e WATER: Newly planted vegetation needs regular watering for the first two growing seasons. A good rule of thumb is give plants about an inch of water twice a week. In Fall, cut back to watering once a week and in the next growing season. INSPECT: Inspect plants frequently for stress - wilting, discolored leaves, etc. If one type of plant doesn’t do well, consider replacing it with a species that is thriving. WEED: Weed as needed, or allow native and non-invasive “weeds” like goldenrod, Queen Anne’s lace, and yarrow to grow. Be on the look out for invasive plants such as oriental bittersweet and purple loosestrife. Carefully remove invasives in a way that will not spread seeds and cause more to grow. d esi GN refere NC es Hardesty and Kuhns. Maine Buffer Handbook. 1998. University of New Hampshire Cooperative Extension. Landscaping at the Water’s Edge An Ecological Approach. 2007 47 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs veGetated swale s izi NG a N d d esi GN STEP 1: Location. Swales are often located close to roads or driveways. They are usually built in naturally sloping areas to convey runoff safely and slowly to a vegetated area where it can infiltrate. If a vegetated area doesn’t exist, consider building a rain garden, dry well, or other practice at the end of the swale to encourage the runoff to soak into the ground. A slope of 1” for every foot in length is enough to slowly move the runoff through the swale. Consider the source of the runoff, the slope of the land, and where you want the runoff to ultimately end up when selecting the location of your swale. Swales should not be used to direct water off of your property, or into a road or waterbody. STEP 2: Length and width. Consider the natural contour of the land when deciding on the shape and dimension of the swale. A swale that meanders down a slope will convey runoff more slowly than a straight swale. The distance from the source of the runoff to the desired outlet location will dictate the length. A swale can be any width. Constraints on the site, such as buildings and property setbacks, can influence the width and how the swale fits into other landscaped features. STEP 3: Berms or check dams. If a swale needs to be oriented straight down a hill or on a steep slope, consider adding berms or check dams to the swale design. Berms or check dams are built across a swale, similar to speed bumps in a road. They are used to slow down the speed of runoff as it flows through the swale. STEP 4: Plant selection. Refer to Native Plants for New England Rain Gardens on the Soak Up the Rain NH program website at http://soaknh.org/wp-content/uploads/2016/03/ Native-Plants-for-NH-Rain-Gardens_20160322.pdf for plant suggestions. While this guide A vegetated swale is a shallow channel that slows runoff and directs it to an area where it can infiltrate. Swales use plants to stabilize the soil, reduce erosion, slow the flow and absorb runoff. EQUIPMENT & MATERIALS r Measuring tape r Shovels r Rakes r Plants - native grasses, sedges, and seedlings r Mulch r Wheel Barrow(s) r Stakes r String & string level 48 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs was developed for rain gardens, many of the species would do well in vegetated buffers. Hardy ground covers and grasses that produce uniform, dense cover, and can withstand flood and drought conditions are best. If the swale is to be located close to a road or in an area where snow will be stored, salt-tolerant plants should be considered. STEP 4. Identify staging and material disposal area(s). Identify an area on the site where delivered materials, such as stone, compost, and mulch, can be stored temporarily while the vegetated swale is being built. Also determine where excess materials, like sod and soil that is excavated from the swale, will be disposed. i N stallatio N STEP 1: Mark out location. Using stakes and string or spray paint, mark out the boundary of the swale according to the design. Be sure to identify the placement of any berms or check dams. These are areas that you will likely not need to dig as deeply, if at all. STEP 2: Dig. Dig out the shape of the swale. The deepest part of the swale should be about 3’ deep. The width of the swale will depend on how much space you have on your site. A swale can be any size or length, but most are shaped like a trapezoid with the sides being three times wider than the width of the base. The slope of the sides should be between 1% and 4% (Figure 1). STEP 3: Berms and check dams. For swales on steep slopes (5% or steeper), berms or check dams can be used to slow down the flow of runoff and reduce the potential for erosion. These can be made of compacted earth and reinforced with plantings and stone, or can be made of larger stones. Be creative. Berms made with large stones can become beautiful landscape features. STEP 4: Secure swale inlet. Depending on how runoff enters the swale, consider stabilizing the inlet with a splash guard, crushed stone, or hardy plants to reduce erosion from fast moving water. STEP 5: Plant the swale. Use good planting practices, such as those listed below. Place plants while still in their pots into the buffer according to the planting plan. Make adjustments for spacing as needed. When you are ready to plant, remove one plant at a time from its pot. TIP: Be careful not to compact the soil when digging because it will reduce the ability of the swale to infiltrate runoff. For clay soils or other poorly infiltrating soils, you may want to dig down an additional 11/2’ below the bottom of the swale and create a sandy loam by mixing sand in with the existing soil, then refill the hole. This will improve infiltration. Figure 1. Profile of vegetated swale. 3 31 RATIO 1% - 4% SLOPE 49 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs • Dig a hole twice as wide as the plant’s rootball and no deeper than the rootball. • Loosen and rough up the rootball before planting, especially those rootbound in the container, to encourage healthy root growth. • Plant to the same depth or slightly deeper than they were in the pot. • If staking trees, make sure the trunks are allowed to sway in the wind. • Water: For landscaped or enhanced buffers, water just after planting and daily during the first week. During the second week, water every other day. Then, water twice a week through the first growing season. STEP 2. Mulching. Spread 2” to 3” of mulch over the root zone of plants to provide weed suppression, slow release of nutrients, and additional moisture retention. Be sure to keep mulch a few inches away from plant stems and shrub and tree trunks. m ai N te N a NC e INSPECT: Inspect seasonally and after large storm for signs of erosion, accumulated sediment, and plant stress - wilting, discolored leaves, etc. WATER: Newly planted vegetation needs regular watering for the first two growing seasons. A good rule of thumb is for trees and shrubs to get about an inch of water twice a week each time you water. In Fall, cut back to watering once a week and in the next growing season. WEED: Weed as needed, or allow native and non-invasive “weeds” like goldenrod, Queen Anne’s lace, and yarrow to grow. Be on the look out for invasive plants such as oriental bittersweet and purple loosestrife. Carefully remove invasives in a way that will not spread seeds and cause more to grow. CLEAN: Clean out accumulated sediment and replace vegetation as needed. d esi GN refere NC es Vermont Department of Environmental Conservation. Low Impact Development Guide for Residential and Small Sites. December 2010. 50 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs water bar A water bar intercepts runoff traveling down moderately steep walkways, paths, gravel driveways, and other areas and diverts it into stable vegetated areas to reduce erosion. s izi NG a N d d esi GN STEP 1. Determine slope. Find the slope of the land where the water bars will be located. Follow the steps below to determine slope. a. Place one stake at the uphill end of the slope and another at the downhill end (Figure 1). b. Tie a string to the uphill stake at ground level. Use a string level to level the string between the two stakes. c. Measure the length of the string between the stakes. This is the run or length. d. On the downhill stake, measure the height from the ground to the string. This is the rise or height. e. Divide the rise by the run and then multiply the result by 100. This is the slope. SLOPE (%) = (RISE ÷ RUN) X 100 STEP 2. Determine how many water bars are needed. a. Compare your percent slope to the waterbar spacing in Table 1 to determine how far apart the water bars should be. b. Divide the length of your path by the spacing between water bars from Table 1 to get the number of water bars that you will need. Round to the nearest whole number. LENGTH OF PATH / WATER BAR SPACING = # WATER BARS EQUIPMENT & MATERIALS r Measuring tape r Shovels r Saw r 6” x 6” pressure treated or other rot- resistant timbers or logs r two 18” lengths of 1/2” steel rebar (per water bar) r 3/4” crushed stone r Mulch Percent Slope Spacing between water bars (ft) 2%250 5%130 10%80 15%50 25% +40 Table 1. Suggested water bar spacing. Figure 1 TIP: Alternatively, you can place the waterbars to target erosion prone areas. 51 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs STEP 2. Determine material needs. Timbers or Logs: Water bars should be installed at about a 30 degree angle to the path and should extend 6” off both sides of the path. Measure the width of your path at the angle you intend to install them. To determine the length of timbers or logs you will need, multiple the number of water bars by the width of the path plus 1 foot. NUMBER OF WATER BARS x (PATH WIDTH + 1ft) = TIMBER LENGTH (ft) Crushed Stone: Each bar should have a trench about 12” wide and 6” deep along the entire uphill length and an apron, or small dry well, at the outlet end. Allow about 1 cubic foot for the apron for each bar. To determine the volume of crushed stone needed, multiply the number of steps by the volume needed for each step using the equation below (assumes a 12” wide and 6” deep trench). If needed, multiply the result by 0.037 to convert cubic feet to cubic yards. [1ft3 +(0.5ft2 x LENGTH OF BARS IN FEET)] x NUMBER OF BARS = CRUSHED STONE NEEDED(ft3) i N stallatio N STEP 1. Dig. Dig a trench for the wood timber or log that is at approximately a 30º angle across the path. The trench should be deep enough so the top of the timber or log will be almost flush with the trail on its downhill side once in place. Be careful to dig only as deep as needed to set the timber to make sure that the soil under the water bar is stable. Store soil and rocks excavated from the trench on the trail below the water bar to be used later to backfill the trench (Figures 1 and 2). STEP 2. Prepare timbers. Prepare materials by cutting the timbers or logs to the appropriate length according to the design. Many lumber suppliers will cut them to length for you. Remember that each timber should extend 6” on each side. Drill 1/2” diameter holes approximately 6” from the ends of each timber. STEP 3. Install timbers. Install the timber or log by placing it snug against the downhill side of the trench. The timber should be level and have no high points or voids under it. STEP 4. Secure timbers. Secure the timber with rebar stakes making sure that the rebar is pounded down to be flush or slightly recessed with the top of the timber to avoid any sharp edges. 6” diameter log or timber steel rebar 18” long 1/2” diameter 3/4” crushed stone Figure 2. Side view of waterbar. Figure 1. Top view of waterbar. secure timbers with steel rebar install at 30º angle create stone apron to armor outlet 52 New H ampsHire HomeowNer’s Guide to s tormwater maNaGemeNt do-it-Y ourself stormwater solutioNs STEP 5. Backfill the water bar. a. Dig a 12” wide and 6” deep trench along the uphill side of the timber. b. Fill the trench with crushed stone, leaving a few inches of the timber exposed. c. At the outlet of the waterbar, place an apron of crushed stone to prevent erosion. d. Pack soil and gravel up against the downhill side of the timber so that the top of it is flush with the path. e. Cover all disturbed soil with seed and mulch or cover with leaf litter. m ai N te N a NC e INSPECT: Inspect seasonally and after large storm for signs of erosion or accumulated sediment. CLEAN: Clean out accumulated sediment, leaves, and debris. The stone may need to be cleaned or replaced periodically if void spaces get filled with sediment. Remove and replace with clean stone or remove clogged stone, wash, and reinstall. d esi GN refere NC e Maine Department of Environmental Protection. Conservation Practices for Homeowners. Fact Sheet Series. May 2006. Figure used with permission from the Maine Department of Environmental Protection.