Building better communities with you© 2007 Nitsch Engineering

Low Impact Development: Jackson Square Case Study

Presented by John M. Schmid, P.E., Senior Project Manager

Stormwater Management Design Criteria

Mitigate the peak rate of stormwater runoff to pre-existing levels (Boston Water and Sewer Commission requirement)

• 2- and 10-year storm eventsEncourage groundwater recharge(City of Boston requirement)

• Swales, Pervious Pavement, Perforated PipesMitigate the project’s infrastructure costs (Owner’s requirement)

• Strive for non-redundant systems– i.e.: green roof versus below grade perforated

pipe detention system

Low Impact Development (LID) Initiatives

Green Roof Systems

Rain Gardens

Vegetated Swales

Pervious Pavements

Jackson Square intends to utilize:

Jackson Square – Existing ConditionsColumbus Avenue at Centre Street, Boston, MA

Site I: 60,287 sf CN=86Site II: 216,929 sf CN=94Site III: 212,187 sf CN=90

* Urban Fill – “D” Soils

Jackson Square – Conventional Utility PlanSite I: 60,287 sf CN=94Site II: 216,929 sf CN=95Site III: 212,187 sf CN=91

1. Underground detention systems

2. Conventional catch basin & pipe systems

3. Conventional Roofs

Jackson Square – Proposed Green ImprovementsSite I: 60,287 sf CN=88Site II: 216,929 sf CN=89Site III: 212,187 sf CN=87

1. 50%-75% Green roofs2. Rain Gardens3. Vegetated Swales

Comparing Design Alternatives

Existing Conventional Green RoofCN Value CN Value CN Value

Site I 86 94 88Site II 94 95 89Site III 90 91 87

Curve Number (CN) Value Comparison:

Jackson Square LID Initiatives

Green Roof Systems Components of Green Roofs

EssentialWaterproofing MembraneRoot barrierDrainage LayerFilter FabricGrowing Medium (Substrate)Vegetation

OptionalMembrane Protection layerInsulationWater Retention LayerErosion Protection LayerIrrigation SystemWater Features, Walkways,

Curbs, Railings, Lighting

Jackson Square LID InitiativesRain Gardens

Jackson Square LID InitiativesVegetated Swales

Jackson Square LID InitiativesPervious Pavement

Any Questions?

THANK YOU!

Contact Information

John M. Schmid, P.E., Senior Project Manager

Nitsch Engineering

186 Lincoln Street, Suite 200

Boston, MA 02111

(617) 338-0063

jschmid@nitscheng.com