East Manawa Porous Paving Project Council Bluffs, Iowa. Project Location. Phase 1 Project Location 9/2/2011

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1 East Manawa Porous Paving Project Council Bluffs, Iowa International Public Works Congress & Exposition APWA September 19, 2011 Presented by Scott Renaud, P.E., FOX Engineering Project Location Phase 1 Project Location 1

2 Area History 430 homes in the project area Formerly a campground Small lots 50 to 60 foot in width, feet in depth Annexed in the 70s and utilities installed Evolved from campground to cabins to full time houses What prompted the project? Poor drainage no storm sewer Streets in poor condition Soil conditions fair to poor - variable Underground utilities in poor condition Corrosive soils Sanitary sewer cast iron Water main ductile 40 year life of underground piping Project Parameters Right of way width 30 feet All utilities in the right of way Fences next to the right of way line Very flat 1 foot of fall in 1 mile No basements high water table No sidewalks 2

3 Existing Street Existing Street Existing Drainage 3

4 Existing Drainage Existing Drainage Solutions Considered Conventional storm sewer Deep construction dewatering Large diameter pipe Pump station required Half mile to outlet to Lateral 5 open ditch Estimated cost - $18 to 20 million 4

5 Solutions Considered Storm Water Treatment Systems Treatment intakes and manholes Infiltration chambers Proprietary systems Expensive to clean & maintain High ground water issues Selected Solution Porous Pavement Shallow construction Recharge Lake Manawa Treat water for discharge Short distance to discharge Have a backup plan Estimated Cost $14-15 million Why porous asphalt? Standard HMA construction Quick construction Predictable permeability Small cost premium over conventional asphalt 25-30% Simple and effective storm water storage and treatment 5

6 Other permeable pavement alternatives? Permeable PCC Unproven lots of failures Unreliable, inexperienced, and unwilling contractors Weak, inflexible pavement on suspect subgrade Slow construction Cost premium of 2x or 3x Other permeable pavement alternatives? Porous Pavers Advantage of incremental construction Cost can be competitive Allow for utility repairs in the future Typical Cross Section 6

7 Features of the design Uncompacted subgrade Engineering fabric across the entire cross section 18 inches of crushed stone 1 inch choke stone (did not need) No crown single transverse slope Transverse grade of 1% Additional Features Stand up vertical curb Longitudinal grade minimum of 0.40% Storm sewer intakes installed for Junction manholes for pipe bends Access to drain pipe for cleaning Backup intake in the event of clogging installed at low points Operations and Maintenance Manual Asphalt Mix Design PG Grade ½ Inch Mix 100% Crushed Stone Hard Stone Granite No recycled materials No fines (<2%) Void Space of 22% minimum Two lifts of asphalt 7

8 Rock Gradation Sieve Size Percent Passing By Weight 3/ / / No No No Asphalt Content 5.75% Phase 1 Project Bid Phase 1 Project Demonstration Project Two blocks 400 linear feet Project bid on May 21, 2009 Engineer s Estimate - $489, Low Bid - $369, Awarded to MFT Construction, Council Bluffs HMA subcontractor Western Engineering, Harlan 8

9 Phase 2 Project 2010 Bid on Dec. 8 th, 2009 Utility relocation March/April 2010 Start May 2010 Complete August 2010 Engineer s Estimate $1,113,000 Low Bid (same contractor as Phase 1) $737,211 No major changes to project requirements Phase 1 Project Information HMA Base Course 290 tons bid, 266 tons placed HMA Surface Course 145 tons bid, 155 tons placed Porous HMA cost as % of project = 13.5% Porous HMA time as % = *5% Phase 1 Project Timeline June 17 th Utility relocations started July 21 st MFT started work on water July 30 th MFT started sanitary sewer Aug. 4 th MFT started storm sewer Oct. 6 th MFT started curb & gutter Oct. 15 th READY TO PAVE! 9

10 Phase 1 Project Timeline October 16 th Base Course Temperature 45 degrees Done in 4 hours October 20 th Asphalt Surface Course Project Complete October 28 th Project under construction for 20 weeks Paving (incl. Curb) 3 weeks Utility Relocation Water Main Installation 10

11 Sanitary Sewer Installation Sanitary Sewer Installation Sanitary Sewer Installation 11

12 Beginning Subgrade Excavation Pipe, fabric, rock installation Storm Pipe Installation 12

13 Pipe & Subgrade Construction A2000 Slotted Pipe Finish Rock Subgrade 13

14 Curb Laying Operation Curb Edge Adding 6 Inches of Rock 14

15 Rough Rock Grade Begin Curb Backfill Curb Backfill 15

16 Loaded Truck on Rock Ready to Pave Rock Surface 1 ½ Stone 16

17 Starting Paving Paving Operation First long pass completed 17

18 Awaiting Surface Course Base Course Structure Adjustment 18

19 Typical Drivewy Finished Project Finished Project 19

20 Raining on Final Walkover Finished Project What it looked like before 20

21 Finished Before After! 21

22 January 18, 2010 Does it work? Does it work? 22

23 Lessons Learned Side streets will be dirty after the project is complete Over-rolling can reduce permeability consider dual pavers one pass Consider a single lift more permeability Investment of $30,000 per lot Lessons Learned How does it handle winter conditions? Pavement and rock subgrade drains so fast that freezing the pavement is not an issue Research indicates that 18 inch rock layer prevents any freezing of the soil subgrade No issues to date 23

24 Unintended Benefits Limestone drainage layer may modify the soil ph to reduce corrosivity of the soil Porous HMA is 13.5% of the total project cost Special Thanks to City of Council Bluffs Greg Reeder, Public Works Director Ed Jankowski, Staff Engineer All the patient residents of E. Manawa Asphalt Paving Association of Iowa MFT Construction Western Engineering Questions? 24