Horsley Witten Group Sustainable Environmental Solutions. Rich Claytor, P.E. Janet Bernardo, P.E. horsleywitten.com

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1 Horsley Witten Group Sustainable Environmental Solutions Rich Claytor, P.E. Janet Bernardo, P.E. horsleywitten.com

2 Agenda Introduction & Grant Goals Stormwater & GI Overview Grant Work Completed to Date Discuss Candidate Sites Select 2 Pilot GI Projects for Further Consideration Horsley Witten Group Sustainable Environmental Solutions

3 Introduction & Grant Goals Grant Project Funded through the 604(b) Program for Water Quality Assessment and Planning Increase Awareness Stormwater Issues Educate Stakeholders Identify Opportunities for Green Infrastructure Horsley Witten Group Sustainable Environmental Solutions

4 MassDEP Project Partners Watertown Department of Public Works Watertown Department of Community Development and Planning Watertown Stormwater Advisory Committee Horsley Witten Group, Inc. Horsley Witten Group Sustainable Environmental Solutions

5 Stormwater & Green Infrastructure Overview Stormwater Basics GI Practices Benefits Limitations Costs Horsley Witten Group Sustainable Environmental Solutions

6 Stormwater Basics Urbanization results in increased surface runoff BEFORE AFTER

7 Stormwater Basics At ~10% impervious we begin to see: Water quality issues Impacts to biological communities Increased flooding Stream erosion Loss of recreational uses Shellfish bed closures Reduced baseflow and recharge Watertown is 49% impervious

8 Watertown Street Views Horsley Witten Group Sustainable Environmental Solutions

9 Watertown Stormwater Improvements Horsley Witten Group Sustainable Environmental Solutions

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13 Green Infrastructure Practices Non-Structural Practices Bioretention and Green Street Practices Permeable/Porous/Pervious Pavements Infiltration Practices Wetland Practices Water Quality Swales Rainwater Harvesting Green and Blue Roofs

14 Non-Structural Practices Stormwater passive controls and/or programs designed to reduce runoff volume, reduce pollutants, and/or enhance infiltration. Practices: Impervious cover removal Open space preservation Natural landscaping Street sweeping

15 Bioretention and Green Streets Shallow landscaped depression designed to capture stormwater runoff for treatment and/or infiltration through natural processes. Practice Variants: Bioretention Tree Filters Stormwater Planters Rain Gardens

16 Bioretention and Green Streets

17 Bioretention Retrofit

18 Tree Trenches

19 Bioretention and Green Streets Benefits & Limitations Benefits Good runoff reduction & pollutant removal Good aesthetics fits in with site landscaping Natural approach, affecting air quality, temperature, & habitat Moderate cost Limitations Not good on steep slopes needs flat bottom Some clogging potential Limit drainage area to <10 acres Some maintenance required

20 Permeable/Porous/Pervious Pavements Permeable surface material that allows rainfall to percolate through the media into underlying soils or drainage collection system. Practice Variants: Permeable pavers Porous asphalt Pervious concrete Proprietary materials (precast pervious slabs, recycled tires/glass)

21 Permeable Paver Options

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23 Permeable/Porous/Pervious Pavements Benefits: Good runoff reduction, promotes recharge, excellent pollutant removal No additional space consumption Reduces need for sand/salt in winter Limitations: Not good on steep slopes High maintenance (e.g. vacuuming) to prevent clogging Require deeper groundwater and permeable soils Needs careful construction sequencing High cost

24 Cost Considerations Capital cost ranges - Implementation is site specific and economy dependent. As designers and contractors become more familiar with controls, costs decrease. Design and testing - Green infrastructure typically requires an engineered design. Design costs may be more costly than conventional, but implementation costs can be less expensive. Land consumption - Most practices can be integrated into site design. Maintenance costs - Requires a change in mind-set and training, some specialized equipment.

25 Routine general maintenance and frequency - Practices require initial inspection and early maintenance. Non-routine maintenance - infrequent but may require system overhaul. Specialized equipment and training - Mostly landscaping related for such activities as tree pruning, re-mulching, minor erosion gullying, etc.) Inspections and enforcement - Critical to overall long-term success. Performance impacts - Many practices will still perform, but may suffer aesthetically; clogging a real threat.

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27 Grant Work Completed to Date HW met with DPW and CDPD Staff Utilized MassGIS & Town Mapping Evaluated Total Phosphorous by Land Use Reviewed Historical Bacteria Data at Outfalls Analyzed Soils, Outfalls, Catchment areas Attended SAC Meeting Identified 21 Potential Locations, Site Visits Focused on Town-owned Property and ROWs Horsley Witten Group Sustainable Environmental Solutions

28 21 Potential Locations to Install Green Infrastructure

29 Catchment Areas and Outfalls

30 Soil Types of Catchment Areas

31 Annual Total Phosphorous Loads per Catchment Area

32 Bacteria Levels per Outfalls

33 12 Candidate Sites Visibility, Cost, Maintenance Priority Catchment Areas Public Improvement Projects 21 POTENTIAL LOCATIONS 12 CANDIDATE SITES 2 PILOT SITES

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35 Town Library Parking Lot

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37 Town Hall Roof Runoff

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39 Main Street Corridor

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41 Porter Boylston St.

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43 Springfield

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45 Grove Kondazian

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47 Orchard

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49 Lowell School

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51 Beacon Arsenal St.

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53 Common Spring St.

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55 Common St. Corridor

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57 Common Orchard St.

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59 Hosmer School Entrance

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61 Hosmer School

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63 Middle School Rear Lot

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65 O Connell Park Lot

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67 DPW Parking Lot

68 12 Candidate Sites

69 2 Pilot Projects Rank Sites Based on: Project Complexity Cost Effectiveness Impervious Area Public Education Constructability Soils, Slopes Maintenance

70 Next Steps Select 2 Pilot Sites Develop 30% Design Plans Develop Green Infrastructure Tracking System for Watertown

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72 Watertown Department of Public Works Stormwater Advisory Committee Horsley Witten Group, Inc. Rich Claytor, P.E. Janet Carter Bernardo, P.E Horsley Witten Group Sustainable Environmental Solutions

73 Horsley Witten Group