Building Blue ProjectSpruce Pond Sub-watershed, Franklin

Charles River Watershed Association

A Practical Example of Pollution Prevention in a Typical New England Suburban Town.

Study Area: Spruce Pond Sub-watershed

Sub-watershed Drainage Areas

Existing Phosphorus Load by Drainage Area

Design Parameters

• Reduce phosphorus in stormwater runoff by 43% to comply with expected permit

• Design with no credit given for street sweeping, fertilizer control or other practices

• Evaluate existing stormwater treatment for credit and/or retrofit

Site 4A - 1: Central Park Terrace/North Park Street

Fletcher Field Infiltration AreaProposed underground infiltration chamber to infiltrate 1” storm

INFILTRATION CHAMBER

DRAINAGE AREA 1,096,682 sqft

% IMPERVIOUS 32%

BMP AREA (AB) 14,775 sqft

BMP DEPTH (AD) 3 ft

ACTUAL WQV 30,941 cuft

ACTUAL WQD 1.00 in

Site 4A – 3: Peck Street lot, Fletcher Field

Peck Street Lot, Fletcher Field

BIORETENTION- 1” Storm

DRAINAGE AREA 34,474 sqft

% IMPERVIOUS 100%

WQV 2873 cf

DEPTH MEDIA (DF) 2.00 ft

PONDING HEIGHT (2X HF) 9 in

TF (FILTER TIME) 2 days

SURFACE AREA REQUIRED 1210 sqft

Bioretention area placed within reorganized parking lot

Visualization: Bioretention garden in Parking Lot

Peck Street lot – alternative design in park area

BIORETENTION- 0.4” Storm

DRAINAGE AREA 34,474 sqft

% IMPERVIOUS 100%

WQV 1149 cf

DEPTH MEDIA (DF) 2.00 ft

PONDING HEIGHT (2X HF) 9 in

TF (FILTER TIME) 2 days

SURFACE AREA REQUIRED 484 sqft

Alternative 2- Bioretention system placed on field instead of reorganizing parking lot

Site 4B-2: Wachusett Street lot, Fletcher Field

Parking lot alternatives

Visualization: Vegetated Swale

Visualization: Rain Garden in Fletcher Field

Site 4c: Parmenter School

Drainage Areas - Parmenter SchoolFour Bioretention areas dispersed across site to treat 1” storm

BIORETENTION - 1" storm

DRAINAGE AREA 93,422.05 sqft

IMPERVIOUS AREA 49,933.31 sqft

PERVIOUS AREA 43,488.74 sqft

WQV 4,107 cf

DEPTH MEDIA (DF) 2.00 ft

PONDING HEIGHT 6 in

TF (FILTER TIME) 2 days

SURFACE AREA REQUIRED 1826 sqft

Drainage Area- Parmenter School (4C)

Visualization: Rain Gardens in Front Lawn

Visualization: Rain Gardens in Front Lawn

Site 3G – 2: Cottage St./Union St.

BIORETENTION - 1" storm

DRAINAGE AREA 340,774.00 sqft

IMPERVIOUS AREA 270,628.70 sqft

PERVIOUS AREA 70,145.30 sqft

WQV 20,882 cf

DEPTH MEDIA (DF) 2.00 ft

PONDING HEIGHT (2X HF) 6 in

TF (FILTER TIME) 2 days

SURFACE AREA REQUIRED 9,281 sqft

Dispersed bioretention areas treating 1” storm across sub-drainage areas including:

• Cottage and Union Street on and off ROW retrofits

• On site retrofits on hardware store site, etc.

• Bump-outs at intersection of Geb & Saxon St.

Visualization of Cottage Street Retrofits

Computer optimization process

• “Best Engineering Judgment” design – S0• Computer Optimization:

– Define possible treatment types– Establish requirements for treatment types– Assign costs to treatment types

Optimal Design – S2

Estimated cost range

Spruce Pond Subwatershed Restoration51 potential sites for stormwater improvements

• “Best Engineering Judgment”– 28 sites selected– ~ $4.6 m

• Optimized– 41 sites selected– ~ $2.9 m

Preliminary Cost Comparison Cost Per Impervious Acre Treated

$0.00

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

CRWA S0 CRWA S2 EPA S1 EPA S2 EPA S3Scenario

Do

llar

($

$/impervious acre

Proposed Drainage Area Retrofits

S0

Plan S0 Plan S2

Lessons Learned

• Model optimization can save you money!

• Treat the first flush• Infiltration is the most cost

effective strategy• Treating large volumes is cost

effective but may not solve the whole problem

Next Steps for Franklin

• New stormwater permit, expected by end of 2010– Develop a Phosphorus Control Plan within 5 years

– Implement Phosphorus Control Plan within 10 years

• Install several pilot projects to learn from experience

Special Thanks

• Jeff Nutting, Town Administrator• Bill Yadisernia, Robert Cantoreggi, Franklin DPW• James Esterbrook, Franklin GIS Department• Nick Alfieri, Franklin Conservation Commission• Beth Dahlstrom, Franklin Planning Department• Franklin Technical Advisory Committee