This image cannot currently be displayed. Greening the Black Porous Pavement Demonstration Project City of Boston Presented by Bethany Eisenberg Maine Stormwater Conference November 16, 2015
TEAM LEADERS Bill Egan, Katie Choe; City of Boston Public Works Hilani Morales; Mayor s Office of Neighborhood Services Pallavi Mande, Kate Bowditch; Charles River Watershed Association Christian Simonelli, Elliott Laffer; Boston Ground Water Trust Bethany Eisenberg, Steve Thomas; VHB
Wont work in winter Clogs Too Expensive Too much maintenance DEP/EPA 319 Grant Funded Demonstration Project Evaluate Other Projects - Design Review - Recommend retro-fit approach for Boston Materials and Methods - Evaluate /select cost effective practices Construction Monitoring Provide construction oversight report successful /non-successful Stormwater Volume Effect - Evaluate reduction in volume of stormwater discharged to combined sewer (CRWA) Pollutant Reduction Effect - Evaluate pollutant removal via filtering through permeable pavement system. (CRWA) Recharge Effect - Evaluate effect on groundwater elevation. (BGWT) Process Evaluation - Evaluate design, public outreach and construction process for the permeable pavement demonstration
Boston Groundwater Protection Overlay District
BGwT Wells Source: Boston Groundwater Trust
Site Selection not so easy in Boston
Selection Criteria including: Poor Existing Pavement Minimal Surface Evidence of Utilities Source: VHB, Inc.
Any Concerns Here? Source: VHB, Inc. Boston Porous Alley Public Alley 543 Permeable Pavement Demonstration Project
Parking Basements Dumpster Access Sediment Control Materials Staging Safety Utilities Fine Grading Resident Access Source: VHB, Inc.
Public Alley Private Alley Source: VHB, Inc.
Geotechnical Information Borings and Permeability Information Get it EARLY
Starting Point Design Criteria System Porous Asphalt - Stone reservoir - Overflow structure Location - City owned portion public alley 543. Design /Load - City of Boston Alley Criteria (T-18, 18 Ton Axle). Specifications UNH Stormwater Center modified for this particular project. Liner - impermeable membrane at sides of reservoir Aggregate min. depth 24 in permeable pavement section. Grading - maintain existing grades at top of Alley/easement. Underdrain - underdrain (above the bottom of the reservoir) Hydrologic best possible with structural load driving design LOCAL LOW VOLUME ROADWAYS AND PARKING LOTS (< 2,000 ADT, < 2% Trucks, Limited Turning Movements)
4,820 s.f. drainage Area (100% IC) 560 s.f. permeable pavement section 425 cu.ft. storage (1,064 cubic feet aggregate reservoir with void ratio of 0.4) Alley Design Source: VHB, Inc.
Cross-Section of Porous Alley No. 543 Boston MA Source: VHB 2013
During Preliminary Design Phase City of Boston & CRWA Outreach to Community Project Purpose reduce CSOs, recharge groundwater, reduce pollutant discharge Project limits Porous pavement within the City owned Right of Way Parking City Effectively worked out alternative parking plans Dumpster - Temporarily relocated to one end of alley Dust Control - Contractor required to complete continual dust control Noise Construction activities weekdays 7:30 AM to 3 PM Safety - Contractor responsible for securing the entire site
Details and Design
Decisions Discussions Sequencing & Extent of Paving Public Private Conceptual Cost Estimates 3 Draft Options: $200,000-$230K Decided on: Full Depth pavement reconstruction with protection of the porous asphalt section Ability to correct/ modify roadway profile and grade for positive drainage to porous asphalt section Single construction job - mobilization Standard top around perimeter to get liner keyed in creating a joint Adjustment of the adjacent manhole will not require patching No surface joints around the structure
Construction Sequencing 1. Remove existing pavement/subbase 2. Trucking materials off Site 3. Excavate and install base & underdrains and cover 4. Install new manhole for overflow and draindown 5. Repave with permeable pavement and standard pavement
Daily construction oversight
Utilities & Construction Photo source: Keville
Liner and Fabric Installation Photo source: Keville
Reservoir Construction and Compaction
Transitional Edge and Protection Source: VHB, Inc.
Fine Grading
First Lift
Surface Course Source: VHB, Inc.
Finish Day Source: Keville.
Source: VHB, Inc.
Source: VHB, Inc.
Infiltration Testing ASTM 1701 Seal plastic or metal 12 dia. ring to porous pavement with plumber s putty. Pre-wet the area for testing. Slowly pour 5 gallons of water into the ring while maintaining a maximum depth of ¼ inches of water If the 5 gallons design not infiltrate within 15 minutes the pavement should be vacuum swept
Infiltration Test Results Test # 1-A M (lb) t (sec) D (in) K (in-lb) I (in/hr) 40.0 321 11.25 126870 124.9 Test # 3-A M (lb) t (sec) D (in) K (in-lb) I (in/hr) 40.0 520 11.875 126870 77.1 Test # 1-B M (lb) t (sec) D (in) K (in-lb) I (in/hr) 40.0 317 11.25 126870 126.5 Test # 3-B M (lb) t (sec) D (in) K (in-lb) I (in/hr) 40.0 512 11.875 126870 78.3 Test Site #1 Average I: 125.7 in/hr Test Site #3 Average I: 77.7 in/hr Test # 2-A M (lb) t (sec) D (in) K (in-lb) I (in/hr) 40.0 439 11.250 126870 91.3 Test # 2-B M (lb) t (sec) D (in) K (in-lb) I (in/hr) 40.0 430 11.250 126870 93.2 Test Site #2 Average I: 92.3 in/hr
Project Construction Tasks / Timeline Start July 14 Delay July 15 to August 20 Finish Day September 6, 2014 July 14 2014 September 6, 2014 Construction
Construction Cost Final Estimate $200-250K Contractor final billed amount $231K Factors for cost Utility relocation First time for some workers Lack of materials /equipment lay down (mobilization each day No parking on site for workers Space constraints necessitated handwork on a large portion of this project.
Lessons Learned Pre-Planning is significant Site Selection Education helpful Define Champion Team Limit Design Team Utility Coordination Construction Inspection
Lessons Learned Design
Treatment Potential Infiltration rate in the alley estimate 6-7.8 /hour based on in-situ testing 4,820 s.f. (0.11 Ac) Drainage Area- multi-family Residential Land Use with 100% IC 2.32 lbs/acre/year estimated phosphorus export rate for land use Storage for runoff from more than 1.06 storm event - before overflowing 0.26 lbs/year of phosphorus estimated to be captured in Alley. Preliminary Results - Rainfall data indicates a 1.09 rainfall event occurred on 10/22/2014 and a 2.09 event occurred on 10/23/2014 with 100% infiltration to groundwater. * Information from Charles River Watershed Association
Lesson Learned Location
Lesson Learned Materials Source: ICPI Source: ICPI Source: Adam Duedenhoffer
Permeable pavement Construction Checklist
Offices located throughout the east coast www.vhb.com