1. General information
Location and description of the intervention
City or FUA
Boston
Region
Northern America
Native title of the NBS intervention
Porous Alley Demonstration Project
Short description of the intervention
The Porous Alley consists of a strip of porous asphalt in a public alley aimed at filtering stormwater and managing runoff in the affluent South End neighbourhood of Boston. Most of the neighbourhood around the NBS location is filled with land that once was tidal marshes, supported by wood pilings, and threatened by falling groundwater levels. The Porous Alley was designed and implemented as a demonstration project to test the feasibility of using porous asphalt to increase groundwater recharge and reduce flooding and water pollution. The increasing groundwater level has high importance in the area the NBS is located in as building foundations are at risk from low water levels. (1,2)
Address

Public Alley 543
Boston
United States

Location
Point location, which indicates where the NBS takes place
Total area
232.00m²
NBS area
232.00m²
Type of area before implementation of the NBS
Residential
Website of the intervention
https://www.crwa.org/uploads/1/2/6/7/126781580/porous-alley-demonstration-proje…
Timeline of intervention
Start date of the intervention (planning process)
2013
Start date of intervention (implementation process)
2013
End date of the intervention
2014
Present stage of the intervention
Completed
Goals of the intervention
- Testing the efficacy of new green technology in Boston – porous asphalt in streets and alleyways
- Recharging groundwater levels to reinforce the structural integrity of nearby buildings
- Cleaning and filtering polluted runoff to prevent it from entering the Charles River (1)
Quantitative targets
Unknown
Monitoring indicators defined
- Infiltration of precipitation to the ground (litres)
- Treatment of pollution, water quality
- Amount of sediment captured (kg) (1,2)
Sustainability challenge(s) addressed
Climate action for adaptation, resilience and mitigation (SDG 13)
Climate change adaptation
Water management (SDG 6)
Stormwater and rainfall management and storage
Improvements to water quality
Climate change adaptation: What were the goals of the NBS?
Reduce the impacts of climate risks events on urban places and communities
Build resilience
Climate change adaptation: What activities are implemented to realize the conservation goals and targets?
Implement sustainable urban drainage infrastructure (e.g. to make space for water)
Please specify "other Type of NBS project"
Application of green technology to increase ground water recharge rainwater drainage and filtration
Implementation activities
- Selection of an ideal area for the demonstration project based on several criteria
- Pre-construction on-site soil test (2)
- Coordination of several public meetings to ensure that area residents were comfortable with and well informed about the project
- Creation of a storage area beneath the porous asphalt layer from coarse gravel with a capacity of 425 cubic feet (approximately 12 m3) of water storage (2)
- Installation of an overflow pipe from the storage area into the existing sewer to prevent any possible overflow from the storage area. (2)
- Installation of a 6-inch diameter well to the storage area with an access cap at the surface to monitor infiltration (2)
Type of NBS project
Knowledge creation and awareness raising
Other
NBS domain and interventions
Ecological domain(s) where the NBS intervention(s) is/are implemented
Green areas for water management
Sustainable urban drainage systems
What is the level of innovation / development of the NBS related to water management?
Medium / High: sustainable urban drainage systems which include water storage and diverts water flooding
Amenities offered by the NBS
Educational and research amenities (nature protection centre, monitoring stations)
Services
Expected ecosystem services delivered
Provisioning services
Water (surface and ground water for drinking and non-drinking purposes)
Regulating services
Water purification / filtration
Scale
Spatial scale
Sub-microscale: Street scale (including buildings)
Beneficiaries
Primary Beneficiaries
Citizens or community groups
Governance
Governance arrangements
Co-governance with government and non-government actors
Non-government actors
Non-governmental organisation (NGO) / Civil society / Churches
Citizens or community groups
Please specify the roles of the specific government and non-government actor groups involved in the initiative
The initiative of a demonstration project of porous asphalt arose from the partnership among the City of Boston Public Works Department, the Charles River Watershed Association (CRWA), and the Boston Groundwater Trust (BGWT) in 2013 (1,2)
Key actors - initiating organization
Local government/municipality
Non-government organisation/civil society
District/neighbourhood association
Land owners
Public space owned by the city
Key actors - Other stakeholders involved (besides initiating actors)
Local government/municipality
Non-government organisation/civil society
District/neighbourhood association
Land owners
Public space owned by the city
Participatory methods/forms of community involvement used
Dissemination of information and education
Consultation (e.g. workshop, surveys, community meetings, town halls)
Policy drivers
NBS intervention implemented in response to an Regional Directive/Strategy
No
NBS intervention implemented in response to a national regulations/strategy/plan
No
NBS intervention implemented in response to a local regulation/strategy/plan
Yes
Please specify the "local regulation/strategy/plan"
The City of Boston has adopted a Groundwater Conservation Overlay District (GCOD), Article 32 zoning, in sections of the City to protect wood pile foundations of buildings from being damaged by lowered groundwater levels. The Porous Alley Demonstration project testing porous asphalt as green infrastructure technology to abide by 2012 consent decree requiring Boston Water and Sewer Commission to implement better water pollution control mechanisms (1)
Mandatory or voluntary intervention
Mandatory (based on policy)
Intervention is mandatory
Environmental regulation
Enablers
Presence of specific city-level GI/NBS vision/strategy/plan - mentioned in connection to the project
Unknown
Presence of specific city-level GI/NBS section/part in a more general plan - mentioned in connection to the project
Unknown
Presence of city network or regional partnerships focused on NBS - mentioned in connection to the project
Unknown
Presence of GI / NBS research project - mentioned in connection to the project
Unknown
Subsidies/investment for GI / NBS in the city - mentioned in connection to the project
Unknown
Co-finance for NBS
Yes
Co-financing governance arrangements
No
Was this co-governance arrangement already in place, or was it set up specifically for this NBS?
Not applicable
Financing
Total cost
€50,000 - €100,000
What is/was the Cost/Budget (EUR) of the NBS or green infrastructure elements?
apprx. 60 200 EUR
What are the total amount of expected annual maintenance costs?
Unknown
What is the expected annual maintenance costs of the NBS or GI elements?
Unknown
Please specify cost savings
Unknown
Please specify total cost (EUR)
Under Section 319 (of the Clean Water Act), the U.S. Environmental Protection Agency provides grant funding to states to reduce pollution from stormwater runoff and other sources. The Massachusetts Department of Environmental Protection’s Section 319 Nonpoint Source Competitive Grants program provided 43 000 EUR that was matched with funds for construction provided by the City of Boston. Additional funding and in-kind support was provided by the Boston Groundwater Trust and Vanasse Hangen Brustlin, Inc. (1,2)
Source(s) of funding
Public national budget
Type of fund(s) used
Earmarked public budget
Non-financial contribution
Unknown
Business models
Risk reduction model
Which of the involved actors was motivated by this model?
Public actor (e.g. municipality)
Type of innovation
Technological
Infrastructural innovation
Please specify technological innovation
The technology of porous asphalt is not exactly innovative, however, its application in Boston is. Porous pavement experiments in Boston have not had an excellent track record, and the Porous Alley project not only provided the city and relevant stakeholders the opportunity to learn-by-doing but also enabled the monitoring and evaluation systems necessary to systematically test the efficacy of the technology in a Boston-specific setting (1)
Novelty level of the innovation
The innovation is copied/derived from previous initiative(s) without substantial adaptation
Please specify novelty level of the innovation
Unknown
Replicability/Transferability
Unknown
Please specify Replicability/Transferability
Unknown
Impacts, benefits
Environmental impacts
Water management and blue areas
Improved water quality
Improved stormwater management
Enhanced protection and restoration of freshwater ecosystems
Description of environmental benefits
- Rainwater that fell directly onto the porous asphalt, and runoff that ran onto the porous asphalt from surrounding pavement, was filtered into the subsurface storage area, and then rapidly filtered into the soil below (2)
- The groundwater monitoring wells showed increases in ambient groundwater levels during all seasons monitored (2)
- In 2015, the Porous Alley resulted in about 273,000 litres of water recharged into the ground, along with about 20 kilograms of sediment being captured
Economic impacts
Unknown
Description of economic benefits
Unknown
Social and cultural impacts
Unknown
Description of social and cultural benefits
Unknown
Type of reported impacts
Achieved impacts
Indicators
1) increase in groundwater levels through infiltration of precipitation to the ground, and 2) treatment of water pollution (1,2)
Analysis of specific impact categories
Job creation: The NBS created ...
No information available
Negative impacts: Did the project cause any problems or concerns?
Yes
Please specify the negative impacts
During consultations with civil society, some residents close to the NBS area mentioned the concern of flooding in their basement as a result of the porous asphalt installation. These complaints were addressed and examined. There is no available record of any actual basement flooding as a result of the intervention (1)
COVID-19 pandemic
Unknown
Methods of impact monitoring
Process of recording NBS impacts
No evidence in public records
Methods used to evaluate the impacts of NBS
Measurements of biophysical aspects of the NBS (e.g. temperature, water flow)
Where can this data be accessed? Please include a link to a report or web-page.
https://www.crwa.org/uploads/1/2/6/7/126781580/porous-alley-demonstration-proje…
Evidence for use of assessment
Presence of an assessment, evaluation and/or monitoring process
Yes
Presence of indicators used in reporting
Yes
Presence of monitoring/evaluation reports
Yes
Link to monitoring/evaluation reports
https://www.crwa.org/uploads/1/2/6/7/126781580/porous-alley-demonstration-proje…
Availability of a web-based monitoring tool
No evidence in public records
Impact assessment mechanism
Name of any specific impact assessment tools
Unknown
Use of GIS in mapping impacts
No evidence in public records
Citizen involvement
Citizens involvement in assessment/evaluation
No
Citizens involvement in the analysis of the assessment/evaluation
No
Follow-up to the evaluation / assessment
Unknown
References
List of references
"1) Kim, E., 2018, NATURVATION - Case Study Working Paper: Boston, Massachusetts, USA
2) City of Boston.(2016). Boston’s Porous Alley Demonstration Project Summary Report. Accessed on 16 February 2021. https://www.crwa.org/uploads/1/2/6/7/126781580/porous-alley-demonstration-project.pdf
3) Boston Public Works Department - The Mayors Office of Neighborhood Services. (2013). Boston Porous Alley Project - Public Meeting. Accessed on 16 February, 2021. http://www.bostongroundwater.org/uploads/2/0/5/1/20517842/public_meeting_09-26-13.pdf"
Comments and notes
Public Images
Porous Alley Boston
Source: https://www.crwa.org/hubfs/Our_Work/Blue_Cities_Initiative/Green_Infrastructure_Projects/Porous_Alley/porous-alley-demonstration-project.pdf
Porous Alley Boston
Source: https://www.crwa.org/hubfs/Our_Work/Blue_Cities_Initiative/Green_Infrastructure_Projects/Porous_Alley/porous-alley-demonstration-project.pdf