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SUBURBAN RES Team 19188 Competition Submittal

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Electronic submittal from the team of English + Associates, Asakura Robinson, Watearth Inc, and CivilTech

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SUBURBAN RES Team 19188 Competition Submittal

  1. 1. <ul><li>VERDE LAKES </li></ul><ul><li>SURBURBAN DESIGN COMPETITION </li></ul><ul><li>PROJECT NUMBER 19188 </li></ul>
  2. 2. <ul><li>This scheme’s signature is a series of well distributed, smaller “green” (Verde) lakes as well as several Low Impact Development (LID) techniques throughout the development. In general, our approach accomplishes the following goals: </li></ul><ul><ul><li>Match or reduce development costs for the overall subdivision. </li></ul></ul><ul><ul><li>Filter storm water of pollutants and refuse prior to outfall. </li></ul></ul><ul><ul><li>Reduce acreage dedicated to detention basins and associated excavation costs </li></ul></ul><ul><ul><li>To dissipate runoff water more slowly to compensate for reduced dedicated detention area. </li></ul></ul>CONCEPT
  3. 3. GOALS <ul><li>Methods of accomplishing the project goals: </li></ul><ul><li>Filter storm water runoff through taller, thicker vegetation, through engineered, permeable soils and a through series of plunge pools which allow solids to settle. </li></ul><ul><li>These features double their function as recreational areas, trails, and open space amenities. </li></ul><ul><li>We propose 12-13% larger lots to home buyers which will accommodate target dissipation rates within each lot. The remainder of dissipation occurs through collector swales, divided ROW median swales and in a centrally located, 16 ac. +/- dual-use, detention/recreation area. </li></ul><ul><li>Lot sizes are enlarged from the lot size requirements as follows: </li></ul><ul><ul><li>70’x125’ lots become 70’x140’ lots (112% area increase) </li></ul></ul><ul><ul><li>60’x115’ lots become 60’x130’ lots (113% area increase) </li></ul></ul><ul><ul><li>50’x115’ lots become 50’x130’ lots (113% area increase) </li></ul></ul><ul><li>The larger sellable lot sizes should compete favorably to this entry level market segment and should increase sales velocity and/or allow the developer to sell lots at a higher price. </li></ul><ul><li>Conversely, 50’ local curb and gutter ROW’s become 60’ open ditch ROWs which increase ROW area by 1.12% but decrease impervious paving from 28’ to 22’ (78%) </li></ul><ul><li>The Verde Lakes Master Plan lot count exceeds the Mischer Plan by 18 lots (101.52%) </li></ul><ul><li>We propose further reducing impervious cover by: </li></ul><ul><ul><li>Utilizing permeable paving for all driveways </li></ul></ul><ul><ul><li>Installing residential rain tanks to capture 10% of rainfall from residential roofs for irrigation use. </li></ul></ul><ul><li>We recommend roadside ditches instead of curb and gutter streets in order to further filter storm water through vegetated swales, reduce storm drainage system costs by approximately 30%+/-, slow runoff by approximately 11%, and reduce life-cycle maintenance costs by approximately xx%. These cost reductions lower development capital required of the developer and ultimately lower residents’ MUD taxes and HOA fees. </li></ul><ul><li>We propose a depth of 2’-2.5’-typical for private residential lot bio-retention cells and for public vegetated swales. This depth allows increased soil percolation by penetrating into the Sandy Lean Clay (CL) with sand pockets noted at 2.0’ below existing grade per the Geo-Technical report by Terracon. </li></ul><ul><li>We Increase trail/sidewalk circulation throughout the development in order to reduce residents’ reliance on automobiles and encourage pedestrian and bicycle travel to common destinations such as the Elementary, Middle and High Schools, the central recreation center, the commercial anchors on Clay Road and to future regional trails beyond the subdivision’s boundaries. </li></ul><ul><li>Multiple locations of small ponds, vegetated swales and open spaces provide ample lot premium opportunities for Home Builders. Lot adjacency to trails, wide esplanades, entry features, collector swales, back-of-lot trails and the central detention/recreation facility are all desired locations for the entry level market segment. These smaller scale amenities reduce development expenses of a large, non-reimbursable amenity lake. </li></ul><ul><li>We employ two Options of LID in front yards and LID in rear yards of residential lots. </li></ul><ul><ul><li>The Front LID option is shown on the Master Plan on the 70’x140’ lots. This option allows approximately 30’x65’ of a 2.0-2.5’ deep bio-retention area (0.08-0.11 ACFT per lot). Pedestrian circulation is provided by typical 5’ sidewalks within the 60’ ROW, each side. </li></ul></ul><ul><ul><li>The Rear LID option is shown on the Master Plan on the 60’x130’ lots and the 50’x130’ lots. This option allows approximately 21’x55/45’ x 2.0’-2.5’ deep or 0.04-0.66 ACFT per lot. An 18’ wide drainage easement is located along the central swale line between lots as a public conveyance zone. Rear yard fences are located at the 18’ drainage easement and alternate typical 6’ wood sections with 6’ metal picket sections to balance for visibility to the amenity with back-yard privacy. </li></ul></ul>
  4. 4. TYPICAL VEGITATED SWALE NATIVE FLOWERS & GRASSES 3-5” DEEP CHECK DAMS @ 12-20’ INTERVALS OR MINIMUM 2 DAMS PER SWALE HARDWOOD MULCH OR RIVER ROCK NATIVE GRASS MINIMUN 12” GROWING MEDIUM W/ PERMEABLE FILTER FABRIC OPTION PERMEABLE CONCRETE SHOULDER 5’ WIDE
  5. 5. TYPICAL RAINGARDEN/OPEN DITCH NATIVE FLOWERS & GRASSES SHREDDED WOOD MULCH 3-4” DEEP BLENDED COMPOST (70% WASHED SAND, 30% WOOD COMPOST, 1” DEEP) PERMEABLE CONCRETE SHOULDER 5’ WIDE NORMAL WEIGHT CONCRETE ON COMPACTED SUBGRADE LOOSENED SOIL AT BASE OF EXCAVATION UNDISTRUBED SOIL COMPACTED AGGREGATE BASE
  6. 6. PERMEABLE CONCRETE PERMEABLE BRICK PAVERS PERVIOUS PAVEMENT TYPES
  7. 7. RAIN WATER HARVESTING TANK
  8. 8. VERDE LAKES MASTERPLAN
  9. 9. PROPOSED LOT QUANTITIES
  10. 10. LID DIAGRAM
  11. 11. COMMERCIAL CONCEPTUAL DIAGRAM Commercial tracts offer similar opportunities to utilize bio-swales and underground rain tanks to filter and store storm water. Retention can be built into the detention systems for irrigation use. Rain tanks allow increased developable land. LID features again serve double duty as amenity areas within the retail areas.
  12. 12. SECTION STUDIES
  13. 13. LID STRATEGY AT PRIVATE HOMES
  14. 14. DRAINAGE STRATEGY PER HOME PUBLIC LID PRIVATE LID – REAR YARD PRIVATE LID – FRONT YARD
  15. 15. PUBLIC LID WALKWAY
  16. 16. PROPOSED BRIDGE DESIGN OVER HCFCD DRAINWAX
  17. 17. ENLARGED AERIAL VIEW
  18. 20. SITE ANALYSIS <ul><li>Existing Conditions </li></ul><ul><ul><li>Assumes 8% Impervious Area (CN=80) </li></ul></ul><ul><ul><li>The Lag Time for the project is very long – 6.9 hours </li></ul></ul><ul><li>Proposed Conditions </li></ul><ul><ul><li>Use of LID measures limit the site to 33% impervious (CN=86) </li></ul></ul><ul><ul><li>No LID measures increase the site to 44% impervious (CN=88) </li></ul></ul><ul><ul><li>LID slows velocities and a longer path creates a longer Lag Time through use of rain gardens, bio swales, etc. </li></ul></ul><ul><ul><li>Non LID approach will have a comparatively short Lag Time due to the high velocities through the storm sewer (velocities are approximately 10x higher) </li></ul></ul><ul><ul><li>LID removes the need for a detention pond allowing by limiting pervious area and provides opportunities for more community amenities such as pocket parks and trials where LID measures are located. </li></ul></ul><ul><ul><li>Harris County Flood Control requires a minimum of 0.55 ac-ft/ac of detention for development regardless of development type </li></ul></ul><ul><ul><ul><li>Unit detention rate is 265 ac-ft excluding the Katy ISD site </li></ul></ul></ul><ul><ul><ul><li>Establish County unit detention rate compensates for impervious cover as well as increased storm water conveyance through a site </li></ul></ul></ul><ul><ul><ul><li>Hydrograph comparison of the existing and Non LID approach (which considers development and storm sewer system) actually increases the detention requirement to 276 ac-ft for the 100-year storm </li></ul></ul></ul>LINKED TO: VentanaDrainage Analysis.pdf LINKED TO: Ventana Drainage Study.doc
  19. 21. PEAK STORM WATER FLOW RATE SUMMARY STORM EVENT EXISTING PEAK FLOW RATE (cfs) PROPOSED PEAK FLOW RATE (cfs) CHANGE IN FLOW RATES (cfs) % DECREASE 5 YEAR 232.6 230.5 -2.1 1% 10 YEAR 364.2 343.7 -20.5 6% 100 YEAR 743.2 662.2 -81.0 11%
  20. 22. COST COMPARISON STUDY
  21. 23. CONCLUSION <ul><li>The Verde Lakes Master Plan accomplished the goals of reduced developer costs as well as reduced infrastructure costs passed on to residents through MUD taxes. Larger residential lots will compete favorably with the surrounding market. Distributed amenities allow the majority of lots adjacency or close proximity to ponds, trails, vegetated swales and recreation facilities. This “green” development approach is affordable, technically feasible, meets Harris County requirements and provides a desirable product to the entry level housing market. </li></ul>

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