This document summarizes several porous pavement projects completed by Onondaga County to manage stormwater runoff. It outlines case studies for four parking lots that used designs with porous asphalt and concrete to infiltrate runoff on-site. The case studies describe the design components, costs, estimated runoff reductions, and lessons learned. Key findings include the projects achieved runoff reductions at costs of $0.38 to $0.57 per gallon, and that proper construction and maintenance are important for ensuring the porous pavements function as intended over time.

1. Onondaga County’s 2010 Porous
Pavement Projects
Meeting Stormwater Goals while Managing Costs
March 17, 2011
Joanne M. Mahoney,
County Executive

2. www.SaveTheRain.us
Dan Wible, P.E., LEED AP
Senior Project Engineer

3. Presentation Outline
• Case Studies:
• City Lot #21 (formerly the “Farmer’s Market
Lot”
• City Lot #3
• Pearl Street Lot (DOT)
• Creekwalk
• Case Study Topics:
• Design Components / Goals
• Pre/Post-Construction Photos
• Costs and Metrics Summary
• Lessons Learned

4. Parking Lot #21 (Formerly “Farmer’s Market Lot”)

5. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Design Components
• Costs and Metrics Summary
• Lessons Learned

6. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Design Components:
• 5,000sf infiltration system
• Tree trench (2,000sf) with porous pavers
and 36” of CU-Structural Soil
• Aggregate infiltration bed under standard
asphalt (31” deep)
• Inlet filter inserts
• Entire lot repaved (standard asphalt) and
restriped (6 more spaces)
• Two outlet control structures with weirs
(connection to existing storm sewer)
• Infiltration testing yielded a rate of 20 in/hr

7. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Design Components:
• Impervious area managed: 26,250sf
• Infiltration area: 5,000sf (loading ratio of
5.3:1)
• Runoff capture goal (1”): 2,190cf
• 6 new trees
• Total soil: 6,000cf (1,000cf per tree)
• Total static storage capacity: 4,200cf
(equates to around 2.1” of runoff capture)

11. Parking Lot #21 (Formerly “Farmer’s Market Lot”)
After
Before
CSO Area: Clinton

15. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

16. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Total Project Cost: $188,046
• Total Estimated CSO Reduction: 328,000 gal
• Cost per CSO Reduction: $0.57 per gal

17. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

18. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Stormwater Details and Specifications
• Concrete structures preferred
• Overflow weir plates
• Concerns over inlet filter inserts
(maintenance)

19. Case Study: City Lot #21 (formerly the
“Farmer’s Market Lot”)
• Trees and Plantings
• Temporary maintenance: emphasize/enforce
temporary irrigation and initial pruning
• Species selection and maintenance streamlined
in the future with the City Arborist

20. Case Study: City Lot #21 (formerly
the “Farmer’s Market Lot”)
• Subsurface Materials
• Infiltration bed stone availability: NYSDOT #3A
is typically the cleanest, most available stone in
the size range desired
• CU-Structural Soil Handling/Acceptance:
ensure contractor provides appropriate cover
and maintenance, and perform testing if
needed
• Porous paver edge termination

21. Porous Pavement / Infiltration Practices
in Onondaga County, NY
• Design Assumptions / Guidelines:
• Static storage of first inch of runoff
• Maximum loading ratio of 10:1 (impervious
area to infiltration area); 5:1 is preferred
• Geotextile liner separating rock from soil
(non-woven or woven… or sand?)
• Impervious liner where needed (proximity
to utilities, buildings, etc)
• Observation well and cleanouts
• Perforated distribution pipe and/or
underdrain

22. Porous Pavement / Infiltration Practices
in Onondaga County, NY
• More Design Assumptions / Guidelines:
• Dewater within 72 hours
• Level bed/trench bottom
• Maximum surface grade change of 1-2 feet;
steeper sloped areas may warrant a change
in bottom elevation (via berms or other)
• Upper 3” of the infiltration bed subgrade
should be scarified prior to bed installation
(if necessary)
• Total facility depth should between 24-31
inches (frost consideration)
• Protect existing utilities

23. Porous Pavement / Infiltration Practices
in Onondaga County, NY
• More Design Assumptions / Guidelines:
• Setbacks:
• 10ft to buildings with basements
• 3ft to buildings without basements
• 3ft from utility structures, vents, poles,
etc

24. City Parking Lot #3

25. Lot #3
Porous Concrete
Captures over 700,000 gallons of stormwater annually
CSO Area: Erie Blvd

26. Case Study: City Lot #3
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

27. Case Study: City Lot #3
• Design Components:
• 8,380sf infiltration system
• Tree trench with 36” of CU-Structural Soil
• 6” porous concrete / aggregate
infiltration bed (23” deep)
• Interior tree plantings
• Inlet filter inserts and sumps
• Entire lot repaved (standard asphalt) and
restriped
• One outlet control structure with removable
weir (connection to existing storm sewer)
• Infiltration testing yielded an average rate of
0.48 in/hr (0.24 in/hr used for design)

28. Case Study: City Lot #3
• Design Components:
• Impervious area managed: 38,507sf
• Infiltration area: 8,380sf (loading ratio of
4.6:1)
• Runoff capture goal (1”): 3,209cf
• 23 new trees
• Total soil: 7,650cf (333cf per tree, not
including existing soil volume along edge)
• Total static storage capacity: 3,392cf
(equates to around 1.1” of runoff capture)
• Dewatering time: 72 hours (100-year
storm)

36. Case Study: City Lot #3
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

37. Case Study: City Lot #3
• Total Project Cost: $239,102
• Total Estimated CSO Reduction: 625,000 gal
• Cost per CSO Reduction: $0.38 per gal

38. Case Study: City Lot #3
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

39. Case Study: City Lot #3
• Stormwater Details and Specifications
• Inlet restoration – check if necessary
• Porous Concrete
• Test pad quality control
• Letter to contractor noting concerns with
aggregate, water retarder, water content
• Site installation permitted as 2nd “test pad”
• Cold weather placement: 7 days curing time
per specified temperature requirements

40. Pearl Street Parking Lot

41. Pearl Street Parking Lot
CSO Area: Franklin FCF

42. Case Study: Pearl Street Lot
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

43. Case Study: Pearl Street Lot
• Design Components:
• 25,300sf infiltration system
• Porous asphalt (1.5”) on 3” of asphalt
treated permeable base (ATPB)
• Aggregate infiltration bed under both
standard and porous asphalt (24” deep)
• Inlet filter inserts and sumps
• Entire lot repaved (standard asphalt) and
restriped
• One outlet control structure with removable
weir (connection to existing combined sewer)
• Infiltration testing was variable, but yielded an
average rate of 7 in/hr (2 in/hr used for design)

44. Case Study: Pearl Street Lot
• Design Components:
• Impervious area managed: 73,172sf
• Infiltration area: 25,300sf (loading ratio of
2.9:1)
• Runoff capture goal (1”): 6,098cf
• Total static storage capacity: 10,120cf
(equates to around 1.7” of runoff capture)
• Dewatering time: 24 hours (100-year
storm)

50. Case Study: Pearl Street Lot
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

51. Case Study: Pearl Street Lot
• Total Project Cost: $396,772
• Total Estimated CSO Reduction: 915,000 gal
• Cost per CSO Reduction: $0.43 per gal

52. Case Study: Pearl Street Lot
• Design Components / Goals
• Costs and Metrics Summary
• Lessons Learned

53. Case Study: Pearl Street Lot
• Subsurface Utility Location – coordinate with
utilities early; lack of response or delayed
response resulted in field directives
• Unforeseen Conditions
• Subsurface structure demolition: multiple
building foundations were encountered
• Balance research costs with schedule and
field directive costs
• Ample public notification

54. Creekwalk

55. Creekwalk

60. Revisit Winter 2011: Pearl Street

61. Revisit Winter 2011: Pearl Street

62. Revisit Winter 2011: Lot 3

63. Winter Revisit Notes
• Pearl Street porous pavement performing well,
particularly vs. standard pavement, but is
being over-salted
• Lot 3 wheelstops – wheelstops vs. curbs with
inlets
• Lot 3 porous concrete performing well
• Snow storage areas

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Questions?
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