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Impervious Cover Audit: Findings in Greenville and Pickens Counties

This report by Lawrence Group outlines an audit of pavement regulations in Greenville and Pickens Counties, emphasizing the need to minimize impervious cover from new developments to address non-point source pollution. The methodology used and key recommendations are highlighted to prompt action for sustainable urban planning.

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Impervious Cover Audit: Findings in Greenville and Pickens Counties

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  1. “Pavement Audit” for Greenville and Pickens Counties Diagnosis Report to Focus Group January 25, 2006

  2. Presentation Overview • Lawrence Group • Scope of Audit • Audit Methodology • Recommendations/Findings • Questions/Feedback/Next Steps

  3. The Lawrence Group • Founded in St. Louis in 1983 • Carolinas office in Davidson, NC • Town Planning & Architecture • Municipal, non-profit, and developer clients

  4. Lawrence Group Projects

  5. Mooresville, NC Code

  6. Haynie-Sirrine Master Plan – Greenville, SC

  7. General Development Guidelines – Research Triangle, NC

  8. Active Living Assessment

  9. Concord-Roberta Church Small Area Plan - Concord, NC

  10. Woodlands-Davidson, NC

  11. Belmont Reserve-Belmont, NC

  12. Project Scope

  13. Saluda-Reedy Watershed “. . .non-point source pollution – sediment, nutrients and waste carried by storm water – is now the chief threat to these rivers. . . It will take a concerted effort by community leaders across the Upstate to effectively address the threats of non-point source pollution fed by rapid development . . .” -SRWC

  14. Project Scope • “. . . audit of paving requirements in the codes and ordinances of Greenville and Pickens Counties. . .” • “Identify opportunities. . .to reduce the amount of impervious cover generated by new development.”

  15. Project Scope

  16. Ordinances Reviewed Pickens County • Central • Clemson • Easley • Liberty • (Pickens) Greenville County • City of Greenville • Greenville LUDO • Fountain Inn • Greer • Mauldin • Simpsonville • Travelers Rest

  17. Methodology • Zoning Ordinances and Land Development Regulations • Based on “Builders for the Bay” process (www.cwp.org) • 10 major categories; 36 factors

  18. Methodology • Major Categories • Street width • Right-of-way width • Cul-de-sac design • Street drainage (swales v. curb & gutter) • Parking ratios • Shared parking • Parking lot design • Parking lot landscaping • Sidewalks and planting strips • Driveways

  19. Imperviousness Rooftops + Car space

  20. Imperviousness Transport-related impervious cover: 60-70% (streets + parking areas) Roof tops: 30-40%

  21. Street Design

  22. Street Width • Local Streets: 20-24 feet • Could be as narrow as 16-18 ft

  23. Street Width • Minimum street widths

  24. Street Width • Local Streets: 20-24 feet • Cul-de-Sac streets: 22-28 ft • Could be as narrow as 18 ft • Manufactured home park streets: 20-28 ft • Should be same as local streets • Alleys: 12-30 feet (Greenville County standard is good: 12-18 ft)

  25. Street Width • Local Streets: 20-24 ft • Cul-de-Sac streets: 22-28 ft • Manufactured home park streets: 20-28 ft • Alleys: 12-30 ft (Greenville County standard is perfect) • Collector Streets: 24-40 ft • Could be as narrow as 20 ft • Consider parking, bike lanes, turn lanes

  26. Curb Radii • 25-40 ft (Greenville County) • Pickens Co: Not specified • AASHTO Guidelines: • Local/local: 10-15 ft • Local/collector: 15-20 ft • Collector/collector: 15-25 ft

  27. Right-of-Way Width • 40-50 ft; typically 50 ft • Could be as narrow as 34-38 ft. • Allow utilities in the street

  28. Cul-de-sac Design • Typical: 40 ft (Greenville: 41 ft; Clemson: 35 ft) • Landscaped Islands: 8 of 13 allow • Alternate turn-arounds: • Greenville: yes • Pickens: no

  29. Cul-de-sac Design • Cul-de-sac islands: • Greenville Co.: typically yes • Pickens Co: typically no

  30. Open Channels/Swales • Only Clemson, Easely, Liberty require curb & gutter on all streets • Pickens County swales: < 2 dua; slopes “not excessive” • Tom Schueler: • No slopes > 5% • Runoff velocities > 4-5 ft/sec. • Soils/climate don’t allow dense turf • Water table < 1 ft below channel • No densities > 3 dua

  31. Sidewalks • Context-sensitive requirements • Based on street-type (Clemson) • Development density (> 2 dua) • Proximity to schools (1-1.5 miles) • One side only generally • Alternate networks: 4/13 codes

  32. Sidewalks Street-type based (Clemson): Density-based (FHWA):

  33. Sidewalks • Sidewalk width: typically 4 ft min • ITE & FHWA: 5 ft min.

  34. Planting Strips & Trees • 5/13 codes require planting strip • 2-3 ft wide • 6-8 ft recommended for street trees • No codes require street trees • Benefits of trees • Reduce runoff volumes • Increase soil infiltration • Increase soil water storage • Reduce erosion • Shade prolongs life of asphalt; reduces runoff temperatures • Shade: cars, pedestrians, homes • Improve air quality • Aesthetics (= increased property values)

  35. Planting Strips & Trees

  36. Parking Areas

  37. Parking Ratios • Wide variation in requirements • Not based on reliable research • Shopping Centers • 2-6 spaces/1000 sf in Greenville Co. • 4-5 spaces/1000 sf in Pickens Co. • 10 spaces/1000 sf for food stores in Central, Easley, Liberty • ICSC: 4/1000 yields surplus 99% of time • Parking requirements waived in most CBD’s

  38. Parking Ratios Recommendations to consider: • Use draft Greenville LUDO model • Low minimums (2/1000 sf for retail) • Maximums (use current minimums) • Allow on-street parking to count • Waive/reduce parking req’mts in all CBD’s and other mixed-use nodes • Reduced minimums for transit service

  39. Shared Parking • All codes allow except Clemson • No incentives for sharing • 50 or 100% of spaces may be shared • “each parking space may be counted for each activity” (Central, Easley, Liberty) • Greenville LUDO offers more complex/accurate formula

  40. Parking Lot Design • Stall width: 8.5-9 ft • 2 rows & aisle: 60-64 ft • 60 ft is adequate • Compact spaces: 3/13 codes • Limited benefit • Pervious Pavement (good!): • Wide variation: not allowed; allowed; required • Pickens Co.: allowed but not req’d • Greenville Co.: req’d for 100-200% over minimum

  41. Parking Lot Design

  42. Parking Lot Landscaping • Greenville Co.: All but Fountain Inn • Pickens Co.: Clemson, Easley • Range of applicability: • 1-60+ spaces; new and/or expanded • Clemson, Greenville Co. extremes • Required planting: • Greenville Co.: ~ 1 tree/10-20 spaces • Pickens Co.: 5-10% of area • No required curbing: Good! • No biorention encouraged/required

  43. Parking Lot Landscaping Bio-rentention

  44. Parking Lot Landscaping Bio-rentention: Wilmington, NC

  45. Driveways • Clemson & Mauldin allow permeable driveways (all other codes silent) • Residential Setbacks: 15-40 ft; generally 20+ • Reduce front setbacks to 20 ft or less

  46. Other Issues • Minimum lot size • Consider minimum density instead • Provide incentives for clustering • Encourage Alleys in higher density SF (8+ dua) • LEED-ND (Leadership in Energy and Environmental Design) • Land use policies • Greater density = less impact • Transportation Demand Management

  47. Next Steps Questions/Discussion

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