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SUBURBAN RES Team 19183 Competition Submittal

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Electronic submittal from the team of Brown & Gay, SWA Group and InSite Architecture

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SUBURBAN RES Team 19183 Competition Submittal

  1. 1. 2009 Low Impact Development Design Competition Suburban Residential Development Team 19183
  2. 2. “ Ventana Run” Low Impact Development Design Concepts <ul><li>GOAL: </li></ul><ul><li>Demonstrate that a “conventional” residential land plan can benefit from simple low impact development (LID) measures without sacrificing marketability or adding excessive costs. </li></ul><ul><li>PRIORITY TECHNIQUES: </li></ul><ul><li>Reduced Public Hardscape 4. Hollywood Driveways </li></ul><ul><li>Extensive Use of Bioswales 5. Native/Naturalized Planting to Filter Rainwater </li></ul><ul><li>Grass Stabilized Storm Water Quality Strips </li></ul><ul><li>GENERAL OVERVIEW: </li></ul><ul><li>The low impact development (LID) design concept described in the following presentation focuses on minimizing the amount of impermeable surfaces to extend runoff times, encourage immediate infiltration and storage, and cleanse stormwater before reaching major points of discharge. </li></ul>
  3. 3. Ventana Run – Site Plan Hyperlink File: Master Plan
  4. 4. Ventana Run – Site Enlargements
  5. 5. Lot Illustrative Landscape Plan .
  6. 6. Lot Cross Section LOT GRADING: FROM ROADWAY TO BUILDING LINE The proposed lot cross section for the LID is designed so that from the building line the front 20 feet of the lot will drain to the proposed bioswale adjacent to the roadway. By minimizing the portion of the lot that drains to the roadside bioswales, the roadside bioswale is a maximum of 1 foot deep. The shallow depth allows the proposed driveways to cross the bioswales with an inlet trench drain constructed in the driveway at the crossing and eliminates the need for headwalls. LOT GRADING: FROM ROADWAY TO BACK OF LOT The remainder of the lot is graded so that the building line is the high point and the majority of the lot drains directly to the bioswale located in a 50-foot drainage easement behind the lots at minimum 1 percent slope. The fencing along the back lot line should be wrought iron, which will not block the drainage from the lot.
  7. 7. LID Technique 1 – Reduced Hardscape <ul><li>ROADWAYS: </li></ul><ul><li>It has been estimated that streets account for 40 to 50 percent of the impervious cover in traditional residential areas (1) and generate much of the pollutant load. Reducing the pavement area will reduce the impervious area, runoff volume and pollutants. In the Ventana Run LID design, the Harris County minimum paving design requirements have been incorporated for single and double paving sections with roadside ditches. </li></ul><ul><li>In addition to the use of narrower roadways to reduce the impervious area by approximately 21 percent (22 feet for residential streets vs. the typical 28 feet for residential streets), the LID design incorporates the use of narrower collector roadways throughout the development. The collector roadways have been reduced to a width of 22 feet with a 6-foot grass stabilized storm water quality strip on each side because they are serving residential development and not commercial or multi-family development. The narrower collector roads also help to control speeding. </li></ul><ul><li>INTERSECTIONS: </li></ul><ul><li>At the intersection of the two major collector roadways, the pavement width increases to 41 feet to allow room for a left turn lane. However, at the other intersections, the traffic counts do not warrant left turn lanes. </li></ul><ul><li>**ADD ROAD X-SECTION </li></ul><ul><li>The collector roadway along the west and southern side of the proposed school tract was not reduced in width and is proposed to be a typical 41-foot paved section with curb and gutter. </li></ul><ul><li>SIDEWALKS: </li></ul><ul><li>Sidewalks have been eliminated from the internal sections to further reduce the amount of impervious cover and are only located on a single side of major collector roadways and common green areas, as shown on the site plan, providing access to the proposed school tract and recreation site. </li></ul>
  8. 8. LID Technique 2 – Bioswales <ul><li>EDGE OF ROADS: </li></ul><ul><li>Traditional curb and gutter streets are designed to channelize storm water runoff and quickly transport runoff and pollutants to a storm sewer system. Therefore, as part of the low impact design concept, it was important to eliminate the use of curb and gutter throughout the development. Alternatively bioswales are proposed to be located parallel with the roadway and behind the lots. </li></ul><ul><li>BIOSWALE SLOPES: </li></ul><ul><li>The use of bioswales at a minimal slope of 0.05 percent allow water to slowly drain through grassed areas helping to reduce pollutants and increase the runoff time as water drains to the outfall channel. The increased runoff time allows more water to percolate into the soil. </li></ul><ul><li>BIOSWALE LANDSCAPING: </li></ul><ul><li>The bioswale in front of the lots adjacent to the grass stabilized storm water quality strip will be planted with street trees. The bioswales behind the lots will utilize reforestation and no mow plantings requiring little maintenance and also providing a natural landscape area. </li></ul>Picture from http://www.crd.bc.ca/ watersheds/lid/swales.htm (3)
  9. 9. LID Technique 3 – Grass Stabilized Storm Water Quality Strip COMPOSITION: A 6-foot grass stabilized storm water quality strip is proposed adjacent to the roadways throughout the development in lieu of the standard 6-foot paved shoulder. The 6-foot strip is excavated 8 inches deep and a geotextile is placed on the subgrade. The initial 6 inches are backfilled with an engineered aggregate-topsoil (EAT) mixture of 30 percent topsoil and 70 percent stone. The remaining 2 inches are backfilled with an EAT mixture of 50 percent topsoil and 50 percent stone. Lastly, the area will be seeded for turf establishment. The image to the left is an example of the stabilization technique used for a roadway pull-off along the Gatlinburg Spur in the Great Smokey Mountains National Park (2) . The stabilized 6-foot area provides a location for on-street parking as needed. Runoff from the paved roadway will sheet flow across the 6-foot grass strip helping to remove pollutants from the runoff before entering the roadway bioswale system. Picture from http://www.efl.fhwa.dot.gov/files/technology/GRSM- Stabilized-Grass-Pulloffs-report.pdf (2)
  10. 10. LID Technique 4 – Hollywood Driveways <ul><li>DRIVEWAY DESIGN: </li></ul><ul><li>To further reduce the amount of impervious paved area, Hollywood driveways are being proposed throughout the development. The driveways will consist of four 3-foot wide strips placed to align with the wheel base of a standard car and allow access from the roadway to a two-car garage. Between the tire strips, the grass area will be stabilized with the same material used to construct the 6-foot grass stabilized storm water quality strip adjacent to the roadway. The grass area between the strips should be stabilized to ensure the driveway will be functional for vehicles with a non-standard wheel base. </li></ul><ul><li>BIOSWALE CROSSINGS: </li></ul><ul><li>To eliminate the need for culverts and headwalls as the driveways cross the bioswales, the bioswales have been kept to a maximum depth of 1 foot. Trench drains with grate tops should be installed at the driveway crossings and between closely spaced adjacent driveways. </li></ul>
  11. 11. TSS and Bacteria Removal Efficiencies <ul><li>The use of bioswales has proven to be a very effective means to remove total suspended solids (TSS), reduce turbidity, and reduce heavy metals from stormwater runoff. The reference table below from the State of Oregon’s Department of Environmental Quality summarizes pollutant removal rates for various pollutants. (4) </li></ul>The use of bioswales for the removal of bacterial fecal coliforms has shown mixed results.  Most studies suggest that the bacteria levels actually increase as a result of placement of bioswales.  One possible explanation could be attributed to animals.  Bioswales tend to attract wildlife, aquatic birds, and domestic pets that may contribute to the potential bacteria loading.   It would be important to educate the residents of the subdivision the importance of picking up after their pets and it may be sensible to place signs along the trails adjacent to the bioswales to encourage residential pet waste pickup. (5) Pollutant Removal Rate Total Suspended Solids 83 to 92% Turbidity (with 9 minutes of residence) 65% Lead 67% Copper 46% Total Phosphorus 29 to 80% Aluminum 63% Total Zinc 63% Dissolved Zinc 30% Oil/Grease 75% Nitrate 39 to 89%
  12. 12. Economic Analysis – Utilities <ul><li>EXCLUSIONS: </li></ul><ul><li>The costs shown above do not include the following items because the costs for these items will be equivalent for the traditional development or low impact development: </li></ul><ul><ul><ul><li>Costs for pipeline improvements and/or adjustments </li></ul></ul></ul><ul><ul><ul><li>Engineering fees for drainage studies </li></ul></ul></ul><ul><ul><ul><li>Geotechnical reports and materials testing costs </li></ul></ul></ul><ul><li>ASSUMPTIONS: </li></ul><ul><li>The traditional development utility costs are based on the costs provided in the creation report for the water distribution system, sanitary sewers, storm sewer system, detention and drainage channel, clearing, water plant, water interconnect and wastewater treatment plant. The costs were increased by 25 percent to reflect the increase in connections and acreage from the creation report. The costs include 10 percent contingencies and 15 percent engineering. </li></ul><ul><li>The low impact development utility costs are based on the creation report (increased by 25 percent) for the following items: the water distribution system, sanitary sewer, water plant, water interconnect and wastewater treatment plant. The drainage costs are based on detailed cost estimates for a representative section of each of the three proposed lot types. From those estimates, a cost per acre was established for each type of section. The drainage along the collector roadways and outfall ditch was quantified separately. The costs include half of the costs associated with construction of the 6-foot grass stabilized storm water quality strip adjacent to the roadways. After a conceptual discussion with the TCEQ, the possibility for reimbursement of a stabilized strip that aids in storm water quality and drainage was not ruled out. The costs also include 10 percent contingencies and 15 percent engineering. </li></ul>Hyperlink Files: Utility Cost Estimates
  13. 13. Economic Analysis – Paving <ul><li>EXCLUSIONS: </li></ul><ul><li>The costs shown above do not include the following items because the costs for these items will be equivalent for the traditional development or low impact development: </li></ul><ul><ul><ul><li>Costs for pipeline improvements and/or adjustments </li></ul></ul></ul><ul><ul><ul><li>Bridge costs </li></ul></ul></ul><ul><ul><ul><li>Geotechnical reports and materials testing costs </li></ul></ul></ul><ul><li>ASSUMPTIONS: </li></ul><ul><li>The traditional development paving costs are based on internal section costs of $25,000 per acre as provided in the competition materials. The collector roadways were quantified separately. The costs include 10 percent contingencies and 15 percent engineering. </li></ul><ul><li>The low impact development paving costs are based on detailed cost estimates for a representative section of each of the three proposed lot types. From those estimates, a cost per acre was established for each type of section. The collector roadways were quantified separately. The costs include half of the costs associated with construction of the 6-foot grass stabilized stormwater quality strip adjacent to the roadways. The costs also include 10 percent contingencies and 15 percent engineering. </li></ul>Hyperlink Files: Paving Cost Estimates
  14. 14. Economic Analysis – Amenity Lakes <ul><li>EXCLUSIONS: </li></ul><ul><li>The costs shown above do not include the following items because it assumed that these costs would be equivalent for the traditional development or low impact development: </li></ul><ul><ul><ul><li>Geotechnical reports and materials testing costs </li></ul></ul></ul><ul><li>ASSUMPTIONS: </li></ul><ul><li>The traditional development amenity lake costs are based on the lake areas shown on the traditional development land plan provided with the competition materials. The costs include excavation for a 6-foot deep amenity lake with 5:1 side slopes, a 10-inch thick reinforced concrete lake wall and 2-foot thick clay liner. Below is a link to the cost estimate prepared for the amenity lakes. </li></ul><ul><li>There are no amenity lakes included in the LID plan. Because of the layout of bioswales behind each of the lots, every lot in the subdivision becomes an “amenity” lot. The area behind each lot will be adjacent to a naturally landscaped green space. In the traditional development site plan, there are a limited number of lots that back up to the proposed amenity lakes areas. </li></ul>Hyperlink Files: Amenity Lake Cost Estimate
  15. 15. Economic Analysis – Landscaping and Trail Costs <ul><li>LID LANDSCAPE ASSUMPTIONS: </li></ul><ul><ul><li>All bermuda turf areas (mowed landscape) to receive full automatic irrigation </li></ul></ul><ul><ul><li>No-mow and reforestation areas to use temporary irrigation system until full establishment </li></ul></ul><ul><ul><li>Landscape treatment comprised of 40 percent reforestation and 60 percent no-mow tall grasses </li></ul></ul><ul><ul><li>No-mow grasses to be native prairie grasses or Costal Bermuda allowed to grow to full natural height </li></ul></ul><ul><li>EXCLUSIONS: </li></ul><ul><li>The costs shown above do not include the following items because it assumed that these costs would be equivalent for the traditional development or low impact development: </li></ul><ul><ul><ul><li>Rough grading of site </li></ul></ul></ul><ul><ul><ul><li>Utilities </li></ul></ul></ul><ul><ul><ul><li>Lighting </li></ul></ul></ul><ul><ul><ul><li>Site furniture and park elements (including shelters, structures, etc.) </li></ul></ul></ul>Hyperlink Files: Landscaping/Trail Cost Estimate <ul><li>CONVENTIONAL LANDSCAPE ASSUMPTIONS: </li></ul><ul><ul><li>All landscape to receive full automatic irrigation </li></ul></ul><ul><ul><li>50 percent of turf areas to include canopy trees at 50 trees per acre </li></ul></ul><ul><ul><li>Street tree quantities equal to proposed LID design </li></ul></ul><ul><ul><li>No landscape open space included in residential pod areas </li></ul></ul><ul><ul><li>Linear feet of trail equal to LID design </li></ul></ul>
  16. 16. Economic Analysis – Land Reimbursement ASSUMPTIONS: The traditional development land reimbursement amounts are based on the costs provided in the creation report for the District’s land acquisition of the detention ponds and channels, water plant site, off-site water line easements and wastewater treatment plant site. The land acquisition costs for the detention ponds and channels was increased by 25 percent to reflect the increase in connections and acreage from the creation report. A 10 percent contingency was included for the wastewater treatment plant site costs only. The low impact development land reimbursement amounts are based on the creation report for the following items: water plant site, off-site water line easements and wastewater treatment plant site. A 10 percent contingency was included for the wastewater treatment plant site costs only. Based on the approximate acreages of the water plant site and wastewater treatment plant site given on the traditional development plan and the land costs included in the creation report, an estimated land cost of $15,000 per acre was used to determine the land costs associated with drainage in the LID plan. Reimbursable land costs for the bioswales behind the lots and along the main collector roadway throughout the development were included for reimbursement. Hyperlink Files: Land Acquisition Cost Estimate
  17. 17. Economic Analysis – Maintenance Costs <ul><li>In the proposed LID concept, the elimination of major storm sewer infrastructure and detention basins significantly reduces the maintenance costs associated with those items. It is estimated that over $100,000 is spent annually on maintaining storm sewers; repairing pavement due to storm sewer failures; and mowing, de-silting, erosion repair, and re-seeding of detention basins. </li></ul><ul><li>Additionally, the landscape proposed in the LID street and back of lot bioswales will require minimal maintenance. The cost savings in landscape maintenance is approximate $1,200,000 per year. Prairie Nursery of Westfield, Wisconsin estimates a reduction in maintenance costs of 85 percent for no-mow grasses over a 20 year period. We have conservatively estimated a 50 percent reduction and have not included a reduction in water bills due to reduced irrigation. </li></ul>
  18. 18. Ventana Run <ul><li>Traditional Development Single Family Lot Yield </li></ul><ul><ul><li>70’ x 125’ – 209 Lots (17.59% of Total) </li></ul></ul><ul><ul><li>60’ x 115’ – 664 Lots (55.89% of Total) </li></ul></ul><ul><ul><li>50’ x 115’ – 315 Lots (26.52% of Total) </li></ul></ul><ul><ul><ul><ul><li> 1,188 Total Lots </li></ul></ul></ul></ul><ul><ul><li>* The lot cost is based on 20 percent of an average home sales price of $180,000. </li></ul></ul><ul><li>LID Single Family Lot Yield </li></ul><ul><ul><li>70’ x 125’ – 133 Lots (12.54% of Total) </li></ul></ul><ul><ul><li>60’ x 115’ – 606 Lots (57.12% of Total) </li></ul></ul><ul><ul><li>50’ x 115’ – 322 Lots (30.35% of Total) </li></ul></ul><ul><ul><ul><ul><li> 1,061 Total Lots </li></ul></ul></ul></ul>Traditional Development Low Impact Development Total Cost $46,417,532 $39,697,939 Lot and Land Revenue (average $36,000 per Lot) $43,806,207 $40,257,301
  19. 19. Alternative LID Ideas . Alternative Idea Disadvantage Side lot swales to eliminate the need for driveways to cross the roadside bioswales <ul><li>Side lot fences would not be feasible making the product undesirable in the Houston area </li></ul>Narrower roadways <ul><li>Roadways narrower than the proposed 22-foot wide section would not meet Harris County minimum standards for pavement width </li></ul><ul><li>Narrower roadways would make it difficult for emergency vehicles to pass with cars parked along the street </li></ul>Shared driveways <ul><li>Shared driveways would minimize the amount of impervious cover, however, we did not feel like this would be a marketable alternative that would appeal to homebuyers in the proposed home price range </li></ul><ul><li>Shared driveways may be a viable alternative in a development with higher priced homes </li></ul>Storage of runoff on individual lots <ul><li>The use of rain gardens and/or small retention basins on individual lots would be difficult for the county to maintain or enforce homeowner maintenance </li></ul><ul><li>Water storage below homes would require pier and beam foundations, and this alternative foundation type is not cost effective </li></ul>Rainwater cisterns <ul><li>Rainwater cisterns are not effective because of cost and they would be difficult for the county to permit for use as detention </li></ul>
  20. 20. Alternative LID Ideas . Alternative Idea Disadvantage Green roofs <ul><li>Green roofs for individual homes would be too costly to provide economic benefit to the development </li></ul>Absorption wells <ul><li>The clayey type soils will not absorb as much water as in rocky or sandy soils </li></ul><ul><li>Utilizing small absorption wells will take longer for water to absorb into the soil because of the minimal area in lieu of using bioswales, the water will be spread over a larger area and absorption will increase </li></ul><ul><li>Groundwater elevations could vary from that shown in the geotechnical report depending on the time of year and could affect the conductivity of the soil </li></ul>Use of permeable pavers for roadway shoulders <ul><li>Permeable pavers are more expensive than the proposed stabilized grass shoulder </li></ul><ul><li>Pavers also require additional paving excavation for the paver base </li></ul>Alleys <ul><li>Use of alleys was discussed; however, it was determined that alleys would likely not be as marketable utilizing the proposed product type in this geographic area of Houston </li></ul>Cluster development or open-space development <ul><li>Use of cluster or open-space development may not be marketable in the Houston area. </li></ul>
  21. 21. Drainage Analysis - Methodology Method Explanation Drainage Model EPA-SWMM 5.0 <ul><li>Dynamic routing model designed for complex drainage networks </li></ul><ul><li>Software suited for both micro (pod) and macro (site) analysis </li></ul><ul><li>Robust tools/variables for capturing LID techniques and properties in drainage computations </li></ul><ul><li>Industry-recognized standard and non-proprietary </li></ul>Model Approach Two-model analysis: Pod and Site <ul><li>Pod-level analysis to focus on the parameters and LID techniques applied within each lot and group of lots (pods) </li></ul><ul><li>Site-level analysis to determine the effects of LID techniques on the entire development and compare against the existing (undeveloped) peak flow values for the site </li></ul>Hydrologic/Hydraulic Method SWMM calibrated with Harris County data <ul><li>Harris County (Addicks watershed) Type III 24-Hr Rainfall data for 5, 10, and 100-yr storm events </li></ul><ul><li>Green & Ampt infiltration parameters consistent with Addicks watershed soil types and values </li></ul><ul><li>SWMM-generated hydrographs </li></ul><ul><li>Dynamic Wave routing method </li></ul>
  22. 22. Drainage Analysis – Pod Assumptions Pod Model Entity Assumptions Green & Ampt Infiltration Values <ul><li>Soil values chosen are consistent with the watershed (Addicks) and reflect runoff rates equivalent to those provided in the HCFCD Policy Criteria & Procedure Manual </li></ul>Development Lot Sub-areas <ul><li>Front 20 feet of lot excluded (drains to street and is included in that subarea) </li></ul><ul><li>Standard slope of 1% draining from front to back (to bioswale) </li></ul><ul><li>Percent Imperviousness based on an average slab size of 2,500 sq.ft. </li></ul><ul><li>Manning’s “n” for impervious cover based on asphalt-type shingles, pervious cover based on lawn grass for sheet flow </li></ul><ul><li>Depth of depression storage assumed minimal for impervious cover, elevated for pervious cover consistent with LID practices </li></ul>Street Sub-areas <ul><li>Includes front 20 feet of lot with “hollywood” driveway </li></ul><ul><li>Lot drainage provides longest watercourse to roadside bioswale and therefore 1% slope dictates runoff </li></ul><ul><li>Percent imperviousness based on average of lot, driveway, street, and stormwater quality strip </li></ul><ul><li>Manning’s “n” for impervious cover based on asphaltic concrete, pervious cover based on lawn grass for sheet flow </li></ul><ul><li>Depth of depression storage assumed similar to lot values </li></ul>Bioswale Sub-areas <ul><li>Slope based on natural overland contours </li></ul><ul><li>Percent imperviousness based on undeveloped area </li></ul><ul><li>Manning’s “n” for pervious cover based on dense grass for sheet flow </li></ul><ul><li>Depth of depression storage assumed similar to lot values </li></ul>
  23. 23. Drainage Analysis – Site Assumptions Site Model Entity Assumptions Existing Peak Runoff Rates <ul><li>5, 10, and 100-year storm event values used were those provided for the 640-acre site by the competition </li></ul><ul><li>Values equate to 0.36 cfs/ac for the 5-year, 0.57 cfs/ac for the 10-year, and 1.16 cfs/ac for the 100-year storm events </li></ul>Pod Sub-areas <ul><li>Peak flow rates calculated based on cfs/ac release rates from the Pod analysis assuming average lot width of 60 feet </li></ul><ul><li>Sub-area characteristics are consistent with Pod analysis </li></ul><ul><li>Width factor was adjusted as necessary to match the pod release rates for all three storm events </li></ul>Street Sub-areas <ul><li>Includes street (those outside of pods), stormwater quality strip, and undeveloped bioswale/conveyance ditch </li></ul><ul><li>1% slope maximum from shoulder area assumed </li></ul><ul><li>Percent imperviousness based on average of bioswale, street, and stormwater quality strip </li></ul><ul><li>Manning’s “n” for impervious cover based on concrete, pervious cover based on grass for sheet flow </li></ul><ul><li>Depth of depression storage assumed similar to pod values </li></ul>Offsite Sub-areas <ul><li>Includes school site, commercial sites, wastewater treatment plant (offsite for drainage assumptions), main channels, and bounding roadways </li></ul><ul><li>Offsite areas assumed to be detained to the undeveloped flow rates (see values in table above) by conventional means </li></ul><ul><li>Sub-area characteristics are consistent with Harris County values </li></ul><ul><li>Width factor was adjusted as necessary to match the undeveloped flow rates for all three storm events </li></ul>
  24. 24. Drainage Analysis – Pod Model <ul><li>POD MODEL FACTS: </li></ul><ul><li>Lots drain directly to bioswales </li></ul><ul><li>Streets, stormwater quality strip and lot-fronts drain to street swales flowing to bioswales </li></ul><ul><li>Street swale roughness is 0.06 for small swale; bioswale roughness is 0.08 for dense brush </li></ul><ul><li>Street swale is 1-foot depth with 4:1 side slopes, 10-foot top width, and 2-foot bottom width; bioswale is 3-foot depth with 5:1 side slopes, 50-foot top width, and 10-foot bottom width </li></ul>Hyperlink Files: Pod Input Data Pod 5-Yr Output Pod 10-Yr Output Pod 100-Yr Output Storm Event Pod Release Rate 5-Year 0.35 cfs/ac 10-Year 0.43 cfs/ac 100-Year 1.09 cfs/ac
  25. 25. Drainage Analysis – Site Model <ul><li>SITE MODEL FACTS: </li></ul><ul><li>Thoroughfare bioswales also act as conveyance channels for side streets and development pods </li></ul><ul><li>Street bioswales range from 2 to 4 feet in depth with 4:1 side slopes, average 25-foot top width, and minimum 1-foot bottom width </li></ul><ul><li>Main thoroughfare bioswales range from 4 to 5 feet in depth with 5:1 side slopes, average 55-foot top width, and minimum 13-foot bottom width </li></ul><ul><li>Culverts modeled at all street crossings and outfalls into the main channel </li></ul><ul><li>Water feature areas, parks, visitor center, and water treatment plant included in pod areas (conservative ) </li></ul>Hyperlink Files: Site Input Data Site 5-Yr Output Site10-Yr Output Site 100-Yr Output SWMM Site Map Drainage Diagram
  26. 26. Drainage Analysis – Site Results <ul><li>Site results taken at the discharge point of the main channel show that the proposed LID configuration and techniques applied to the development provide a reduction in peak flow rates below existing (predevelopment) values for the 5, 10, and 100-year storm events. </li></ul>
  27. 27. Marketability and Public Acceptance <ul><li>A premise for applying LID techniques is that LID can be used for any development or site as opposed to focusing on Smart Growth or Land Use Planning practices. The proposed LID concept incorporates a “conventional” neighborhood layout to test LID practices rather than using the competition to study land use planning theory. Because the lot layout does not vary significantly from standard practices, it can be assumed that buyers will not be distracted by unusual lot layouts and will be comfortable with its marketing niche. </li></ul><ul><li>The proposed LID concept incorporates many times the number of trees and no mow grasses found in conventional subdivisions resulting in reduced long term maintenance costs. Additionally, buyers are typically attracted to landscape and street trees, and the long term real estate values bear this out. </li></ul><ul><li>Most lots include visual access to naturalized landscape features in the backyards of the residents. </li></ul><ul><li>Decreases in impermeable surfaces will create healthier soil structure for the community’s landscape and result in higher quality and quantity of wildlife habitat. </li></ul><ul><li>The reduced paving surfaces will act to calm traffic and create a greater sense of community safety. </li></ul>
  28. 28. School and Commercial Site LID Ideas <ul><li>URBANGREEN BIOFILTER: </li></ul><ul><li>The BioFilter system can be used for curb and gutter flow or as an area drain in parking lots. The initial runoff is treated using an engineered soil mixture and vegetation. Product is available from Contech Construction Products, Inc. (6) </li></ul>. PERMEABLE PAVERS: Permeable pavers can reduce or eliminate the need for stormwater detention ponds, and they help to reduce the pollutants from runoff. The pavers allow water to infiltrate through openings between the pavers filled with aggregate. Although more expensive than traditional concrete (depending on the allowable traffic load of the specific paver), permeable pavers can be used for parking stalls, overflow parking areas, walkways, patios or roadways if budget allows. An example of a permeable paver is the Eco-Priora paver from Pavestone. (7) Picture from http://www.contech-cpi.com/stormwater/products/ BioFiltration/biofilter/847 (4) Pictures from http://www.pavestone.com/component/page,shop.product_details/flypage,shop.flypage_pavers_flash_index/product_id,198/category_id,7/ manufacturer_id,0/option,com_virtuemart/Itemid,136/ (7)
  29. 29. Conclusion . The LID design concept presented incorporates several LID techniques to convey storm water through the development. The LID techniques incorporated into the design are both functional and marketable in the Houston area. The overall layout of the LID development is not significantly different from the traditional development layouts popular in the Houston area, but it incorporates additional trees and green areas which are attractive to home buyers and help to increase home values. Based on the economic analysis comparing the cost of a traditional development to the LID concept, the LID concept will cost the Developer less initially and due to greater exposure to landscape areas, should be more marketable from the outset. The LID design concept presented minimizes the amount of impermeable surfaces and extends the runoff time through the use of bioretention areas and green areas. According to the drainage analysis, the post development hydrographs are less than the pre-development hydrographs presented with the competition materials for the 5-year, 10-year and 100-year storms. The proposed LID design concept is feasible from an engineering and economic point of view. As a result of low impact development practices focusing on increased runoff time, additional benefits are realized. Improved water quality through the use of native naturalized plantings, decreased irrigation requirements, increases in wildlife habitat and viewing opportunities, and greater exposure to open space directly from one’s place of residence. These benefits can potentially provide a high quality of life for future residents.
  30. 30. References <ul><li>&quot;Protecting Our Waters-Streets and Roads.&quot; Protecting Our Waters-A Guide to Responsible Development within the Milwaukee River Basin . 11 03 2003. Wisconsin Costal Management Program, Web. 10 Dec 2009. <http://clean-water.uwex.edu/plan/index.htm>. </li></ul><ul><li>Hatcher, Martin L. &quot;Construction of Stabilized Grass Pull-Offs Using Geo-Technology Along the Gatlinburg Spur.&quot; 2004. Web. <http://www.efl.fhwa.dot.gov/files/technology/GRSM-Stabilized-Grass-Pulloffs- report.pdf>. </li></ul><ul><li>Bioswale . Web. 13 Dec 2009. <http://www.crd.bc.ca/watersheds/lid/swales.htm>. </li></ul><ul><li>Jurries, PE, Dennis. &quot;BIOFILTERS (Bioswales, Vegetative Buffers, & Constructed Wetlands) for Storm Water Discharge Pollution Removal.&quot; (2003): 25. Web. 11 Dec 2009. <http://www.deq.state.or.us/wq/stormwater/docs/nwr/biofilters.pdf>. </li></ul><ul><li>International Stormwater BMP Database . Web. 11 Dec 2009. <http://www.bmpdatabase.org/index.htm>. </li></ul><ul><li>Web. 10 Dec 2009. <http://www.contech-cpi.com/stormwater/products/BioFiltration/biofilter/847>. </li></ul><ul><li>Web. 10 Dec 2009. <http://www.pavestone.com/component/page,shop.product_details/flypage,shop.flypage_pavers_flash_i ndex/product_id,198/category_id,7/manufacturer_id,0/option,com_virtuemart/Itemid,136/>. </li></ul>.

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