Tisbury MA Impervious Cover Disconnection (ICD) Project: An Integrated Stormwater
Management Approach for Promoting Urban Community Sustainability and Resilience
A TECHNICAL DIRECT ASSISTANCE PROJECT FUNDED BY THE U.S. EPA SOUTHERN NEW ENGLAND
Program (SNEP)
Task 4H. Quantifying Benefits for Municipal Long-Term GISCM Implementation
Strategies
U.S. EPA Region 1
Tisbury MA
Prepared for:
Martha's Vineyard Commission
MassDOT
MARTHA'S VINEYARD
COMMISSION
massDOT
Massachusetts Department of Transportation
Paradigm Environmental
Prepared by:
UNH Stormwater Center
Great Lakes Environmental Center
PARADIGM
ENVIRONMENTAL
sc
STORMWATER CENTER
GleC
Blanket Purchase Agreement: BPA-68HE0118A0001-0003
Requisition Number: PR-R1-18-00375
Order: 68HE0118F0011
1
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CC:
Date:
Re:
To:
From:
Ray Cody, Mark Voorhees (US EPA Region 1)
Khalid Alvi, David Rosa, Ryan Murphy (Paradigm Environmental)
Project Technical Team
2/25/2020
Quantifying benefits for municipal long-term GI SCM implementation strategies
(Task 4H)
1 EXECUTIVE SUMMARY
This memorandum presents the technical approach for the application of Opti-Tool (U.S. EPA, 2016) to the
evaluation of opportunities to address stormwater quantity and quality in Tisbury, MA. The Planning Level
Analysis functionality in Opti-Tool was used to compare the cost-effectiveness of various Green
Infrastructure (GI) and Stormwater Control Measures (SCM) design scenarios. The assessment includes a
town-wide assessment and further describes opportunities and their associated costs and benefits within the
town's nine zoning districts. This study expands upon a previously study (U.S. EPA, 2020) that focused on
two outfalls, #2 and #7, in Tisbury. Together, the studies leverage both the Planning Level and
Implementation Level Analyses options of Opti-Tool. The outlet study used the Implementation Level
Analysis which allows users to apply the SUSTAIN optimization engine to estimate SCM performance and
obtain optimization results to provide cost-effective SCM sizing strategies. The town-wide assessment
presented in this memorandum relied on the Planning Level Analysis option in Opti-Tool. The planning
level analysis provides a watershed-based overview of stormwater management opportunities for decision-
makers to consider. The Planning Level Analysis used Excel Solver to find optimal solutions using existing
SCM performance curves. Unlike the Implementation Level analysis, which produced cost effectiveness
curves based on hundreds of thousands of possible SCM type and size combinations, the Planning Level
Analysis assessed cost effectiveness over incremental SCM sizes. The Planning Level Analysis in this
memorandum assumes that for each size increment (i.e. 0.1, 0.2 inches, etc), all SCMs in the watershed are
built to that size.
Cost-effectiveness curves were generated town-wide and for each zoning district. The curves assess the costs
and benefits, in terms of stormwater volume and TN load reduction, which can be expected over a range of
GI-SCM sizes. At a planning level, the results demonstrate that if infiltration-based GI-SCM opportunities
were designed to capture 0.4 inches of runoff from impervious surfaces, the result would be a 78% reduction
in annual storm flow volume and an 81% in annual TN loading. An additional co-benefit of this level of
control is to reduce annual indicator bacteria load in runoff by an estimated 66.5% - 80% assuming a GI-
SCM infiltration rate of 1.02 in/hr. Approximately 78% of the runoff discharge events from treated IC areas
per year would also be eliminated. This benefit could immediately lower impacts to recreational uses in local
surface waters. The estimated cost to achieve these reductions was $13.54 million for the town's entire area
of 6.37 square miles (4,079 acres).
The ability of long-term GI SCM strategies to achieve objectives beyond flood mitigation and nutrient load
reductions, including urban community farming and affordable foods, urban aesthetics and safety, green
jobs, and smart growth land use planning was also assessed. There is substantial evidence that suggests GI
and SCM can be an integral part of holistic strategies that aim to make urban areas more sustainable and
resilient while also enhancing the aesthetic quality of developed areas.
2
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Recommendations: The data presented in this and previous memorandums provides strong support for the
town of Tisbury to begin pursuing the implementation of GI SCM opportunities on both public and private
lands. For Tisbury to successfully achieve long-term solutions to their stormwater issues, the following
should be a top priority:
1) Adopt bylaws for new and redevelopment that aim to reduce directly connected impervious cover.
2) Adopt generic GI SCM design templates that can be easily incorporated into municipal
infrastructure projects and urban renewal.
2 TECHNICAL APPROACH - PLANNING LEVEL ANALYSIS
The purpose of the Planning Level Analysis within Opti-Tool is to quickly evaluate multiple design scenarios
with minimum data requirements and compare them without running a continuous SCM simulation in the
more detailed Implementation Level Analysis mode of Opti-Tool. Two management goals we evaluated,
the goal of reducing TN loading and the goal of reducing stormwater volume. For these two management
goals, eight design scenarios were evaluated. The design scenarios represented incremental SCMs design
sizes to capture between 0.1 and 2 inches of runoff from the contributing impervious cover. A design between
0.31 and 0.35 was previously identified as optimal sizes for TN and volume reduction for outfalls #2 and #7
(U.S. EPA, 2020). Six practices from a range of potential stormwater management methods were evaluated
(Table 1). The six practices were two infiltration techniques, basins and trenches, on soil groups A, B, and
C. Infiltration trenches were used to treat roof runoff while infiltration basins were used to treat runoff from
all other impervious surfaces. Table 2 presents Opti-Tool default parameter specifications for the six
practices. Analyzing a range of large and small design capacities was intended to facilitate a better
understanding of relative costs ($) and maximum load and volume reductions (%) achievable for given design
SCM capacities in Tisbury, MA.
The Planning Level Analysis option used the annual pollutant loading rate by land use category to estimate
the baseline loads, a unit volume cost to estimate the SCM total cost, SCM performance curves (e.g.,
relationship between SCM size and associated TN load or stormwater volume reduction) to estimate the
load and volume reduction. Local climate data were used to develop the HRU-based annual pollutant
loading rates, U.S. EPA (2019) provides further information on the development of the timeseries. The local
data was used instead of the default land loading rates provided in the Opti-Tool. However, the analysis did
use default SCM unit volume costs and SCM performance curves, which are also provided in the Opti-Tool
and use region-specific data. Special attention should be given before using the Planning Level Analysis to
make sure that default data are representative of your study area. In this case study, local precipitation data
were used from Martha's Vineyard Airport station to develop the HRU timeseries, as described above.
Table 1. Potential stormwater management categories and SCM types in the Opti-Tool
Land
Use
Landscape
Slope (%)
Within
100 feet of
Coastline?
Within
25 feet of
Structure?
S
Gr
Management
Category
SCM Type(s) in
Opti-Tool
Pervious
Area
<= 15
Yes
Yes
All
SCM with
complicating
characteristics
-
No
No
A/B/C
Infiltration
Surface
Infiltration Basin
(e.g., Rain
Garden)
3
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Land
Use
Landscape
Slope (%)
Within
100 feet of
Coastline?
Within
25 feet of
Structure?
S
Gr
Management
Category
SCM Type(s) in
Opti-Tool
D
Biofiltration
Biofiltration (e.g.,
Enhanced
Bioretention with
ISR and
underdrain
option)
> 15
-
-
-
SCM with
complicating
characteristics
-
Impervious
Area
<=5
Yes
Yes
All
SCM with
complicating
characteristics
-
No
No
A/B/C
Infiltration
Infiltration Trench
D
Shallow filtration
Porous Pavement
> 5
-
-
-
SCM with
complicating
characteristics
-
4
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Table 2. Opti-Tool SCM design specifications
General
Information
SCM Parameters
Infiltration Trench - A
Infiltration Trench - B
Infiltration Trench - C
Infiltration Basin - A
Infiltration Basin - B
Infiltration Basin - C
SCM
Dimensions
Surface Area (ac)
Varies based-on design runoff depth from treated impervious cover'
Surface
Storage
Configuration
Orifice Height (ft)
0
0
0
0
0
0
Orifice Diameter (in.)
0
0
0
0
0
0
Rectangular orTriangular
Weir
Rectangular
Rectangular
Rectangular
Rectangular
Rectangular
Rectangular
Weir Height (ft)/Ponding
Depth (ft)
0.5
0.5
0.5
2
2
2
Crest Width (ft)
30
30
30
30
30
30
Soil
Properties
Depth of Soil (ft)
6
6
6
0
0
0
Soil Porosity (0-1)
0.4
0.4
0.4
0.4
0.4
0.4
Vegetative Parameter A
0.9
0.9
0.9
0.9
0.9
0.9
Soil Infiltration (in/hr)
8.27
2.41
1.02
8.27
2.41
1.02
Underdrain
Properties
Consider Underdrain
Structure?
No
No
No
No
No
No
Storage Depth (ft)
0
0
0
0
0
0
Media Void Fraction (0-1)
0
0
0
0
0
0
Background Infiltration
(in/hr)
8.27
2.41
1.02
8.27
2.41
1.02
Cost
Parameters
Storage Volume Cost
(S/ft3)
$12.49
$12.49
$12.49
$6.24
$6.24
$6.24
Cost Function
Adjustment
SCM Development Type
New SCM in
Developed Area
New SCM in
Developed Area
New SCM in
Developed Area
New SCM in
Developed Area
New SCM in
Developed Area
New SCM in
Developed Area
Cost Adjustment Factor
2
2
2
2
2
2
Decay Rates
TN (1/hr)
0.13
0.13
0.13
0.27
0.27
0.27
Underdrain
Removal
Rates
TN (%, 0-1)
0
0
0
0
0
0
5
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3 RESULTS: TISBURY Gl SCM OPPORTUNITIES
3.1 Town-wide
Figure 1 presents the HRU distribution in Tisbury, MA. Over half the area of the town is forest (Table 3).
The majority of residential and commercial land uses are concentrated in the eastern part of the town while
agriculture and forested areas are more common in the west. Table 4 presents the HRU area distribution by
the zoning district. Residential districts R3A and R50 are the two largest zoning districts, accounting for
approximately 63% of the total area of the town. Unsurprisingly the business districts (B2 light business
district, B1 business district, and the waterfront commercial) have the most acreage of impervious
commercial land while the residential districts have the highest concentration of impervious residential areas.
A summary of impervious and pervious areas by zoning district is presented in Table 5. Impervious areas
were identified as either being roofs or other impervious areas. Other impervious areas included driveways,
parking lots and roads. The distinction allowed for an assessment of different GI SCM opportunities
depending on the type of imperviousness. The GI SCM opportunities assessed in this study were infiltration-
based, rooftop disconnections were simulated as an infiltration trench, while all other impervious areas were
treated using an infiltration basin. The use of two practices, simulated on three soil types, helped to simplify
the analysis, however the practices predicted benefits from rooftop disconnection may be achieved by a
variety of on-the-ground implementations, including barrels/cisterns that drain slowly to permeable areas.
The maximum area, by zoning district, to implement GI SCM opportunities is presented in Table 6. The
data represents existing pervious areas by land use type that may be retrofitted to treat stormwater.
Importantly, the information in Table 6 only assesses the maximum area, it does not account for the
feasibility of implementation. Therefore, while the majority of pervious land is located in forested areas in
the town, it is unlikely that these areas will become the focus of stormwater management solutions. The
table provides valuable insight into the existing opportunities within the more developed, urbanized zoning
districts and was the basis for the GIS and Opti-Tool analyses to further investigate cost-effective solutions
to reducing storm volume and TN loading. Table 7 presents the treated impervious area for the six SCM
types by land use and zoning district. The analysis assumed that all impervious areas were treated by GI
SCM opportunities. Therefore, while the design size changed incrementally during the analysis, the treated
impervious areas remained as shown in Table 7.
Town-wide, the analysis suggests that a 78% reduction in annual stormwater volume and an 81% reduction
in annual TN load could be achieved at a cost of approximately $13.54 million (Figure 3). The optimal
solutions fall at the inflection point or 'knee' of the curves where reduction has been maximized but costs
have not begun to increase substantially. The result is based on the simplifying assumption that all GI SCM
opportunities were sized to capture 0.4 inches of runoff, which is close to the optimization-derived result of
0.31-0.35 inches estimated to achieve similar reductions in the catchments for outfalls #2 and #7 (U.S. EPA,
2020). Importantly, the curve also demonstrates that a 100% percent reduction in flow volume and TN
reduction should not be expected since only impervious surfaces are treated in the simulation; pervious
surfaces are still capable of producing stormflow and contributing to TN loading.
The distribution of the total cost of implementation across zoning districts is presented in Table 8. Overall,
planning level analysis requires more money spent on implementation is the residential areas versus the
business/commercial districts. This is largely attributed to the distribution of total impervious surfaces (Table
5), there are more acres of impervious surfaces in the larger, residential zones. Table 9 presents the amount
each SCM, distributed across the various land uses in the town, disconnects impervious surface, stores and
captures stormwater, and removes TN. Table 9 also provides a breakdown of the total costs in Table 8.
Rooftop disconnections account for 36% of total costs while treating all other impervious surfaces account
for the remaining 64%.
6
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Legend
Agriculture
~
cn
CD
~
CD
(=~
~
~
~
~
~
Agr
Agr
Agr
Agr
Agr
culture
culture
culture
culture
iculture
Agriculture
Developed
Developed
Developed
Developed
Pervious.
Pervious.
Pervious.
Pervious.
Pervious.
Pervious
_IMP
Pervious_
Pervious_
Pervious_
Pervious
A_High 1=1
~A_Low 1=1
_A_Medium 1=1
_B_High ™
~B_Low 1=1
B Medium
" ~ ~
A_High 1=1
A_Low
A_Medium 11
B_High
Developed Pervious_B_Low
Developed Pervious_B_Medium
Developed Pervious_C_High
Developed Pervious_C_Low
Developed Pemous_C_Medium
Developed Pei"vious_D_High
Developed Pervious_D_Low
Developed Pervious_D_Medium
Forest Pervious_A_High
Forest Pervious_A_Low
Forest Pervious_A_Medium
Forest Pervious_B_High
N
¦ Forest Pervious_B_Low
¦¦ Forest Pervious_B_Medium
¦ Forest_IMP
cu Open Land_IMP
en Commercial_IMP
~ Low Density Residential_IMP
¦ Medium Density Residential_IMP
¦ High Density Residential_IMP
¦ Transportation_IMP
~ Industrial_IMP
d Water
Figure 1. HRU distribution forTisbury, MA.
7
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Table 3. Land use area distribution in Tisbury zoning districts
Total Area by Zoning District (acres)
Land Use
Business
District
(Bl)
Light
Business
District
(B2)
Residential
District
(RIO)
Residential
District
(R20)
Residential
District
(R25)
Residential
District
(R50)
Residential
District
(R3A)
Lagoon
Harbor
Park
(LHP)
Waterfront
Commercial
(W/C)
Total
Forest
0.5
36.0
157.7
145.9
160.5
849.4
1,040.6
-
0.8
2,391.5
Agriculture
-
-
1.1
-
0.9
28.2
116.8
-
-
146.9
Commercial
15.3
46.9
16.0
4.7
4.4
3.5
2.0
-
20.0
112.7
Industrial
-
34.8
0.7
6.2
-
-
-
-
-
41.7
Low
Density
Residential
-
0.7
69.7
142.4
47.0
195.4
95.3
-
1.0
551.5
Medium
Density
Residential
1.9
2.1
361.4
4.1
97.7
9.2
-
-
1.7
478.1
High
Density
Residential
0.3
1.4
5.8
5.9
1.6
11.1
-
-
1.5
27.5
Highway
-
-
-
-
0.0
-
-
-
2.7
2.7
Open Land
0.5
4.1
40.5
21.1
32.2
135.4
76.1
4.5
12.2
326.7
Total Area
(acres)
18.5
126.0
652.9
330.4
344.3
1,232.1
1,330.8
4.5
39.8
4,079.3
8
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Table 4. HRU area distribution in Tisbury Zone districts
Total Area by Zone District (acres)
HRU-Model
Business
District
(Bl)
Light
Business
District
(B2)
Residential
District
(RIO)
Residential
District
(R20)
Residential
District
(R25)
Residential
District
(R50)
Residential
District
(R3A)
Lagoon
Harbor
Park (LHP)
Waterfront
Commercial
(W/C)
Total
Forest IMP
0.1
2.2
11.7
12.8
8.0
56.4
43.7
0.0
0.3
135.3
AgricultureJMP
0.0
0.0
0.0
0.0
0.1
2.0
6.8
0.0
0.0
8.9
Commercial IMP
12.4
34.0
8.5
2.9
2.0
1.2
0.6
0.0
15.6
77.2
Industrial IMP
0.0
14.8
0.5
4.9
0.0
0.0
0.0
0.0
0.0
20.3
Low Density ResidentialJMP
0.0
0.3
24.0
42.4
11.4
52.8
21.3
0.0
0.3
152.5
Medium Density Residential IMP
0.8
0.8
122.6
1.4
27.8
3.0
0.0
0.0
0.7
157.2
High Density ResidentialJMP
0.2
0.5
2.2
3.1
0.7
5.9
0.0
0.0
0.8
13.4
Highway IMP
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
2.4
2.4
Open LandJMP
0.0
1.0
11.3
5.3
3.6
9.7
5.9
1.1
7.7
45.7
Developed Pervious A Low
0.5
11.7
104.1
32.1
49.9
90.2
27.9
0.0
0.1
316.5
Developed Pervious_A_Medium
1.3
14.0
158.0
59.3
59.5
117.4
47.1
0.0
0.4
457.1
Developed Pervious_A_High
0.9
12.6
53.5
31.8
16.1
38.2
21.8
0.0
0.3
175.1
Developed Pervious_B_Low
0.0
0.1
0.2
0.0
0.0
1.5
17.1
0.0
0.0
18.8
Developed Pervious_B_Medium
0.0
0.1
0.1
0.0
0.0
1.1
13.8
0.0
0.0
15.1
Developed Pervious_B_High
0.0
0.1
0.0
0.0
0.0
0.1
2.5
0.0
0.0
2.7
Developed Pervious_C_Low
1.0
0.0
4.6
0.0
0.1
0.0
0.0
0.6
5.6
11.9
Developed Pervious C Medium
0.7
0.0
0.4
0.0
0.2
0.0
0.0
0.8
2.9
4.9
Developed Pervious_C_High
0.2
0.0
0.1
0.0
0.0
0.0
0.0
0.4
0.8
1.5
Developed Pervious D Low
0.0
0.0
2.0
0.4
1.6
21.6
10.4
0.6
0.6
37.3
Developed Pervious_D_Medium
0.0
0.0
1.7
0.6
6.5
9.2
4.2
0.6
0.4
23.2
Developed Pervious_D_High
0.0
0.0
0.3
0.4
3.4
2.6
0.9
0.4
0.3
8.3
Forest Pervious_A_Low
0.1
5.8
30.0
27.1
67.2
203.3
196.4
0.0
0.0
529.9
Forest Pervious_A_Medium
0.2
15.0
73.6
59.2
75.2
408.3
399.7
0.0
0.1
1,031.3
Forest Pervious_A_High
0.1
10.6
40.1
46.5
10.2
158.3
171.0
0.0
0.2
437.1
Forest Pervious_B_Low
0.0
0.8
0.8
0.0
0.0
11.4
130.0
0.0
0.0
143.0
Forest Pervious_B_Medium
0.0
1.5
1.1
0.1
0.0
9.5
81.7
0.0
0.0
94.0
Forest Pervious_B_High
0.0
0.1
0.4
0.1
0.0
2.2
18.1
0.0
0.0
21.0
Agriculture Pervious A Low
0.0
0.0
0.8
0.0
0.3
7.0
27.1
0.0
0.0
35.2
9
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Total Area by Zone District (acres)
HRU-Model
Business
District
(Bl)
Light
Business
District
(B2)
Residential
District
(RIO)
Residential
District
(R20)
Residential
District
(R25)
Residential
District
(R50)
Residential
District
(R3A)
Lagoon
Harbor
Park (LHP)
Waterfront
Commercial
(W/C)
Total
Agriculture Pervious_A_Medium
0.0
0.0
0.3
0.0
0.5
15.4
42.4
0.0
0.0
58.5
Agriculture Pervious_A_High
0.0
0.0
0.0
0.0
0.0
3.7
11.1
0.0
0.0
14.9
Agriculture Pervious_B_Low
0.0
0.0
0.0
0.0
0.0
0.0
21.5
0.0
0.0
21.5
Agriculture Pervious_B_Medium
0.0
0.0
0.0
0.0
0.0
0.0
6.9
0.0
0.0
6.9
Agriculture Pervious_B_High
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
1.0
Total Area (acres)
18.5
126.0
652.9
330.4
344.3
1,232.1
1,330.8
4.5
39.8
4,079.3
Note: The color scale represents the lowest (blue) to the highest (red) footprint of a model HRU across the zoning districts (color gradient varies
horizontally).
10
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Table 5. Pervious and impervious areas in Tisbury
Description
Total
Area
(acres)
Impervious Area (acres)
_ , Other Total
Roofs „ „
Impervious Impervious
Pervious Area
(acres)
Business
District (Bl)
18.53
4.44
9.04
13.48
5.04
Light
Business
District (B2)
125.99
8.72
44.93
53.65
72.33
Residential
District
(RIO)
652.92
49.12
131.77
180.89
472.03
Residential
District
(R20)
330.40
15.46
57.31
72.77
257.63
Residential
District
(R25)
344.27
16.46
37.13
53.60
290.67
Residential
District
(R50)
1,232.14
24.40
106.60
131.01
1,101.13
Residential
District
(R3A)
1,330.80
10.46
67.85
78.31
1,252.48
Lagoon
Harbor
Park (LHP)
4.53
0.02
1.12
1.15
3.38
Waterfront
Commercial
(W/C)
39.75
6.30
21.58
27.88
11.87
Total Area
(acres)
4,079.32
135.40
477.34
612.74
3,466.58
11
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Legend
E3 Biofiltration
Infiltration
~ Rooftop disconection
en Shallow Rltration
~ BMP with complicating site characteristics (Imperviousness)
¦ BMP with complicating site characteristics (Shoreline)
¦ BMP with complicating site characteristics (Wetland)
Figure 2, G! SCM opportunities in Tisbury, MA.
12
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Table 6. Potential infiltration Gl SCM opportunity areas (maximum footprints) by Tisbury zoning district.
Pervious Opportunity Areas for Infiltration Gl SCM in Tisbury by Zoning District (acres)
Land Use Group
HSG
Business
District
(Bl)
Light Business District (B2)
Residential
District
(RIO)
Residential
District
(R20)
Residential
District
(R25)
Residential
District
(R50)
Residential
District
(R3A)
Lagoon
Harbor
Park
(LHP)
Waterfront
Commercial
(W/C)
Total
A
0.41
31.39
143.69
131.90
152.18
754.68
753.24
-
0.35
1,967.83
Forest
B
-
2.41
1.37
-
-
10.12
225.95
-
-
239.85
C
0.04
-
0.32
-
-
-
-
-
-
0.35
A
-
-
1.05
-
0.79
26.01
79.52
-
-
107.37
Agriculture
B
-
-
-
-
-
0.05
27.55
-
-
27.60
C
-
-
-
-
-
-
-
-
-
0.00
A
1.42
12.46
7.38
1.79
2.14
2.20
1.11
-
-
28.49
Commercial
B
-
0.20
-
-
-
0.01
0.28
-
-
0.49
C
1.51
-
0.10
-
0.30
-
-
-
3.70
5.61
A
-
19.72
0.15
1.34
-
-
-
-
-
21.21
Industrial
B
-
-
-
-
-
-
-
-
-
0.00
C
-
-
-
-
-
-
-
-
-
0.00
A
-
0.41
45.21
95.49
32.30
134.43
55.00
-
0.59
363.44
Low Density Residential
B
-
-
0.24
-
-
1.86
10.87
-
-
12.96
C
-
-
-
-
-
-
-
-
-
0.00
A
1.15
1.29
238.82
2.68
69.05
5.44
-
-
-
318.43
Medium Density Residential
B
-
-
-
-
-
-
-
-
-
0.00
C
-
-
0.00
-
0.00
-
-
-
1.00
1.01
A
0.07
0.92
3.57
2.84
0.84
5.24
-
-
-
13.47
High Density Residential
B
-
-
-
-
-
-
-
-
-
0.00
C
-
-
-
-
-
-
-
-
0.63
0.63
A
-
-
-
-
-
-
-
-
-
0.00
Highway
B
-
-
-
-
-
-
-
-
-
0.00
C
-
-
-
-
0.00
-
-
-
0.17
0.17
A
0.02
3.06
19.73
6.52
6.05
56.06
14.50
-
0.00
105.94
Open Land
B
-
-
-
-
-
0.07
20.71
-
-
20.78
C
0.43
-
4.62
-
0.00
-
-
-
0.97
6.02
A
3.07
69.25
459.61
242.55
263.35
984.05
903.37
-
0.94
2,926.20
Total
B
-
2.61
1.61
-
-
12.10
285.36
-
-
301.68
C
1.97
-
5.03
-
0.30
-
-
-
6.47
13.78
13
-------
Table 7. Infiltration Gl SCM treated impervious area (impervious cover disconnected) for Tisbury, MA
Treated Impervious Area for Infiltration Gl SCM in Tisbury by Zoning District (acres)
Land Use
Group
SCM Type
HSG
Business
District (Bl)
Light
Business
District
(B2)
Residential
District
(RIO)
Residential
District
(R20)
Residential
District
(R25)
Residential
District
(R50)
Residential
District
(R3A)
Lagoon
Harbor Park
(LHP)
Waterfront
Commercial
(W/C)
Total
Infiltration
A
0.045
0.066
1.669
0.810
0.631
1.907
0.752
-
-
5.879
Trench
B
-
0.005
0.016
-
-
0.026
0.226
-
-
0.272
Forest
(Rooftop
disconnected)
C
0.004
-
0.004
-
-
-
-
-
-
0.008
Infiltration
A
0.053
1.980
9.901
12.024
7.361
53.779
32.876
-
0.293
118.268
Basin
B
-
0.152
0.095
-
-
0.721
9.862
-
-
10.830
(OtherIC
disconnected)
C
0.005
-
0.022
-
-
-
-
-
-
0.026
Infiltration
A
-
-
0.006
-
-
0.083
0.697
-
-
0.786
Trench
B
-
-
-
-
-
0.000
0.241
-
-
0.242
Agriculture
(Rooftop
disconnected)
C
-
-
-
-
-
-
-
-
-
-
Infiltration
A
-
-
-
-
0.114
1.893
4.343
-
-
6.351
Basin
B
-
-
-
-
-
0.003
1.505
-
-
1.508
(OtherIC
disconnected)
C
-
-
-
-
-
-
-
-
-
-
Infiltration
A
1.957
6.020
2.197
0.613
0.504
0.390
0.125
-
-
11.805
Trench
B
-
0.097
-
-
-
0.002
0.031
-
-
0.130
Commercial
(Rooftop
disconnected)
C
2.087
-
0.029
-
0.070
-
-
-
3.825
6.012
Infiltration
A
4.036
27.418
6.212
2.280
1.228
0.848
0.360
-
-
42.382
Basin
B
-
0.442
-
-
-
0.004
0.090
-
-
0.536
(OtherIC
disconnected)
C
4.304
-
0.083
-
0.172
-
-
-
11.798
16.357
Infiltration
A
-
2.188
0.031
0.386
-
-
-
-
-
2.605
Trench
B
-
-
-
-
-
-
-
-
-
-
Industrial
(Rooftop
disconnected)
C
-
-
-
-
-
-
-
-
-
-
Infiltration
A
-
12.662
0.497
4.521
-
-
-
-
-
17.679
Basin
B
-
-
-
-
-
-
-
-
-
-
(OtherIC
disconnected)
C
-
-
-
-
-
-
-
-
-
-
Infiltration
A
-
0.030
5.491
12.053
4.065
18.279
6.768
-
0.017
46.704
Trench
B
-
-
0.029
-
-
0.253
1.337
-
-
1.619
Low
Density
Residential
(Rooftop
disconnected)
C
-
-
-
-
-
-
-
-
-
0.000
Infiltration
A
-
0.228
18.402
30.302
7.355
33.765
11.037
-
0.305
101.394
Basin (Other IC
B
-
-
0.096
-
-
0.468
2.180
-
-
2.744
disconnected)
C
-
-
-
-
-
-
-
-
-
-
14
-------
Treated Impervious Area for Infiltration Gl SCM in Tisbury by Zoning District (acres)
Land Use
Group
SCM Type
HSG
Business
District (Bl)
Light
Business
District
(B2)
Residential
District
(R10)
Residential
District
(R20)
Residential
District
(R25)
Residential
District
(R50)
Residential
District
(R3A)
Lagoon
Harbor Park
(LHP)
Waterfront
Commercial
(W/C)
Total
Medium
Density
Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.254
0.109
38.645
0.305
10.635
0.781
-
-
-
50.729
B
-
-
-
-
-
-
-
-
-
-
C
-
-
0.000
-
0.000
-
-
-
0.258
0.258
Infiltration
Basin
(OtherIC
disconnected)
A
0.504
0.740
83.954
1.119
17.123
2.256
-
-
-
105.695
B
-
-
-
-
-
-
-
-
-
0.000
C
-
-
0.000
-
0.000
-
-
-
0.483
0.484
High
Density
Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.097
0.163
0.924
0.759
0.332
2.261
-
-
-
4.537
B
-
-
-
-
-
-
-
-
-
-
C
0.001
-
-
-
-
-
-
-
0.226
0.227
Infiltration
Basin
(OtherIC
disconnected)
A
0.098
0.316
1.310
2.299
0.407
3.598
-
-
-
8.028
B
-
-
-
-
-
-
-
-
-
-
C
0.001
-
-
-
-
-
-
-
0.599
0.600
Highway
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
-
-
-
-
-
B
-
-
-
-
-
-
-
-
-
-
C
-
-
-
-
-
-
-
-
0.211
0.211
Infiltration
Basin
(OtherIC
disconnected)
A
-
-
-
-
-
-
-
-
-
-
B
-
-
-
-
-
-
-
-
-
-
C
-
-
-
-
0.012
-
-
-
2.159
2.171
Open Land
Infiltration
Trench
(Rooftop
disconnected)
A
0.000
0.044
0.066
0.531
0.226
0.421
0.115
-
0.000
1.403
B
-
-
-
-
-
0.001
0.165
-
-
0.165
C
0.000
-
0.015
-
0.000
-
-
-
1.766
1.782
Infiltration
Basin
(OtherIC
disconnected)
A
0.002
0.994
9.071
4.768
3.358
9.257
2.306
-
0.002
29.757
B
-
-
-
-
-
0.011
3.295
-
-
3.307
C
0.040
-
2.123
-
0.001
-
-
-
5.942
8.104
Total
Infiltration
Trench
(Rooftop
disconnected)
A
2.353
8.620
49.029
15.457
16.393
24.122
8.457
-
0.017
124.448
B
-
0.102
0.045
-
-
0.281
2.000
-
-
2.428
C
2.092
-
0.049
-
0.071
-
-
-
6.286
8.497
Infiltration
Basin
(OtherIC
disconnected)
A
4.692
44.337
129.347
57.313
36.947
105.397
50.922
-
0.600
429.555
B
-
0.594
0.191
-
-
1.207
16.932
-
-
18.924
C
4.348
-
2.228
-
0.185
-
-
-
20.981
27.743
15
-------
Cost-Effective Curve for Tisbury
$80,000,000
$70,000,000
$60,000,000
$50,000,000
$40,000,000
$30,000,000
$20,000,000
$10,000,000
$-
- 0.1 inch
0.6 inch
1.5 inch
-TN Load Reduction (%)
0.2 inch
0.8 inch
2 inch
X Selected Solution (Flow)
0.4 inch
1 inch
-¦— Flow Volume Reduction (%)
X Selected Solution (TN)
1
7
81%, $13,539,752
<
A
J
7
78%, $13,539,752
10% 20% 30% 40% 50%
Average Annual Reduction (%)
70%
90%
100%
Figure 3. Cost effectiveness curves for incremental sizing of Gl SCM opportunities in Tisbury, MA.
16
-------
Table 8. Costs by development zone to achieve town-wide reductions of 78% and 81% in stormwater volume and TN loading, respectively for the town of Tisbury,
MA
1 Development Zone 1
B1
Business
District
B2 Light
Business
District
LHP
Lagoon
Harbor
Park
R3A
Residential
District
RIO
Residential
District
R20
Residential
District
R25
Residential
District
R50
Residential
District
WC
Waterfront
Commercial
District
Total
325038
$1,130,554
-
$1,608,886
$4,169,444
$1,599,198
$1,270,024
$2,816,910
$619,698
$13,539,752
Note: The color scale represents the least expensive (blue) to most expensive (red).
17
-------
Table 9. Infiltration Gl SCM Solution (0.4 inch) Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) forTisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration
Trench
(Rooftop
disconnected)
A
5.879
63,858
5,547,883
46.176
$213,242
B
0.272
2,956
217,188
2.072
$9,872
C
0.008
82
5,231
0.056
$274
Infiltration Basin
(OtherIC
disconnected)
A
118.268
1,284,599
112,569,011
938.393
$2,143,140
B
10.830
117,630
8,586,227
82.456
$196,246
C
0.026
286
17,597
0.194
$478
Agriculture
Infiltration
Trench
(Rooftop
disconnected)
A
0.786
8,542
742,087
6.177
$28,524
B
0.242
2,624
192,750
1.839
$8,762
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
6.351
68,978
6,044,544
50.388
$115,078
B
1.508
16,378
1,195,480
11.481
$27,324
C
-
-
-
-
-
Commercial
Infiltration
Trench
(Rooftop
disconnected)
A
11.805
128,218
11,139,465
133.671
$428,164
B
0.130
1,413
103,768
1.428
$4,716
C
6.012
65,299
4,178,287
63.909
$218,058
Infiltration Basin
(OtherIC
disconnected)
A
42.382
460,348
40,340,116
484.825
$768,014
B
0.536
5,820
424,851
5.882
$9,710
C
16.357
177,664
10,934,736
173.881
$296,404
Industrial
Infiltration
Trench
(Rooftop
disconnected)
A
2.605
28,300
2,458,676
29.504
$94,504
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
17.679
192,023
16,826,934
202.233
$320,358
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
46.704
507,285
44,072,479
486.545
$1,693,998
B
1.619
17,585
1,291,823
16.350
$58,722
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
101.394
1,101,316
96,507,964
1,067.068
$1,837,362
B
2.744
29,805
2,175,576
27.711
$49,724
C
-
-
-
-
-
Medium Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
50.729
551,008
47,871,095
528.481
$1,840,004
B
-
-
-
-
-
C
0.258
2,806
179,539
2.526
$9,370
Infiltration Basin
(OtherIC
disconnected)
A
105.695
1,148,037
100,602,069
1,112.336
$1,915,308
B
-
-
-
-
-
C
0.484
5,254
323,387
4.731
$8,766
High Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
4.537
49,279
4,281,291
47.264
$164,558
B
-
-
-
-
-
C
0.227
2,461
157,440
2.215
$8,216
Infiltration Basin
(OtherIC
disconnected)
A
8.028
87,201
7,641,373
84.489
$145,480
B
-
-
-
-
-
C
0.600
6,519
401,210
5.869
$10,876
18
-------
Infiltration Gl SCM Solution (0.4 inch) forTisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
0.211
2,289
146,493
1.341
$7,646
Infiltration Basin
(OtherIC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
2.171
23,582
1,451,376
13.818
$39,342
Open Land
Infiltration
Trench
(Rooftop
disconnected)
A
1.403
15,238
1,323,877
11.019
$50,886
B
0.165
1,793
131,722
1.257
$5,988
C
1.782
19,356
1,238,500
13.139
$64,636
Infiltration Basin
(OtherIC
disconnected)
A
29.757
323,215
28,323,260
236.107
$539,232
B
3.307
35,915
2,621,534
25.175
$59,918
C
8.104
88,028
5,417,858
59.757
$146,860
Total
Infiltration
Trench
(Rooftop
disconnected)
A
124.448
1,351,727
117,436,853
1,288.837
$4,513,878
B
2.428
26,371
1,937,250
22.946
$88,060
C
8.497
92,293
5,905,491
83.187
$308,196
Infiltration Basin
(Other IC
disconnected)
A
429.555
4,665,717
408,855,270
4,175.840
$7,783,972
B
18.924
205,548
15,003,669
152.706
$342,922
C
27.743
301,332
18,546,165
258.250
$502,724
19
-------
A summary of the results of the town-wide analysis is presented in Table 10. The residential zoning districts
which encompass a majority of the area of the town, unsurprisingly also had the highest baseline stormwater
volume (gallons/yr) and TN loading (lbs/yr). However, commercial and industrial HRUs generated more
TN per acre than in residential areas (U.S. EPA, 2019). The overall cost ($/gallon) to reduce stormwater
volume was $0.01, a penny per gallon, however, when treating with millions of gallons of runoff, costs can
still add up quickly. The total cost for removing TN ($/lb) was $2,264. Unlike surface runoff, which all
impervious surfaces generate identically (all impervious areas convert the same amount of rainfall to runoff),
TN loading differs by land use type. The cost-effectiveness of GI SCM solutions tends to increase with TN
runoff concentrations. Based on annual TN loading and stormwater volume (Table 10) 99,066 gallons of
stormwater needs to be treated, at a 100% removal rate, to remove 1 lb of TN. Therefore, if TN
concentrations were higher in the runoff, it would take less volume, and therefore less money, to remove a
pound of TN. Local water quality monitoring data could help inform these costs.
The following subsections describe the HRU composition and associated opportunities for GI SCM
implementation within each of the town's nine zoning districts.
20
-------
Table 10. Summary table for baseline conditions, costs, and effectiveness of the Gl SCM solution (0.4 inch) for Tisbury, MA
Results Summary by Zone District
Business
District (Bl)
Light
Business
District (B2)
Residential
District (R10)
Residential
District (R20)
Residential
District (R25)
Residential
District (R50)
Residential
District (R3A)
Lagoon
Harbor
Park
(LHP)
Waterfront
Commercial
(W/C)
Total
Impervious Cover
Disconnected
(acre)
13.485
53.653
180.888
72.770
53.595
131.007
78.311
-
27.884
612
Baseline Average
Flow Volume
(gallons/yr)
14,086,926
56,021,249
193,152,326
79,092,890
62,856,054
166,124,955
124,907,630
1,926,511
30,247,094
728,415,636
Baseline Average
TN Load
(Ibs/yr)
159.679
622.274
1,984.825
789.530
635.617
1,579.136
1,253.917
19.411
307.774
7,352
Flow Volume
Removed
(gallons/yr)
11,046,984
50,887,420
171,090,623
69,136,916
50,808,604
124,262,584
71,469,201
-
18,982,366
567,684,698
TN Load Removed
(Ibs/yr)
147.406
599.656
1,845.838
724.391
533.597
1,200.446
671.385
-
259.047
5,982
Total Cost for
Selected Solution
(S)
$325,038
$1,130,554
$4,169,444
$1,599,198
$1,270,024
$2,816,910
$1,608,886
-
$619,698
#########
Cost per Gallon
Flow Removed
(S)
$0.03
$0.02
$0.02
$0.02
$0.02
$0.02
$0.02
-
$0.03
$0.02
Cost per Pound TN
Removed
(S)
$2,206
$1,886
$2,258
$2,208
$2,380
$2,346
$2,396
-
$2,392
$2,264
21
-------
3.2 B1 Business District
Figure 4 presents the HRUs for the B1 Business District zone. Impervious surfaces make up a high
proportion of the area, with 73% of the land consisting of rooftops and other impervious surfaces. The zone
has relatively limited opportunities for GI SCM implementation (Figure 5). A 0.4 inch design criteria
achieved a 78% reduction in flow volume and a 92% reduction in TN loading (Figure 6). The TN reductions
were achieved at a cost of $325,037.
22
-------
Zone: B1 Business District
Legend
CH Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
CD
CD
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
JMP
Pervious,
Pervious _
Pervious,
Pervious,
Pervious
Pervious,
Pervious
Pervious
Pervious,
Pervious
_A_High
_A_Low
A. Medium
B High
B_Low
_B_Medium
A_High
A_Low
A_ Medium
B_High
B_Low
B Medium
C_High
C_Low
C_Medium
D_High
Developed Pervious_D_Low
Developed Pervious, D. Medium
Forest Pervious _A_ High
Forest Pervious A. Lovv
Forest Pervious,A Medium
Forest Pervious_B_High
Forest Pervbus_B_Lovv
Forest Rerv»us_B_Medium
Forest JMP
Open Land_IMP
Commercial_IMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
InaustriaT_IMP
Water
Figure 4. HRU distribution in the B1 Business District Zone of Tisbury, MA.
¦ Rooftop Area
¦ Other Impervious Area
23
-------
Zone: B1 Business District
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
Figure 5, G! SCM opportunities in the B1 Business District Zone of Tisbury, MA.
24
-------
Cost-Effective Curve for Business District (Bl)
$1,800,000
$1,600,000
$1,400,000
U $1,000,000
"ra
£ $800,000
$600,000
$400,000
$200,000
- 0.1 Inch
0.6 inch
1.5 inch
-TN Load Reduction (%)
0.2 inch
0.8 inch
¦ 2 inch
Selected Solution (Flow)
0.4 inch
1 inch
- Flow Volume Reduction (
Selected Solution (TN)
30% 40% 50% 60%
Average Annual Reduction (%)
100%
Figure 6. Cost effectiveness curves for incremental sizing of Gl SCM opportunities in the B1 Business District Zone
of Tisbury, MA.
25
-------
Table 11. Infiltration Gl SCM Solution (0.4 inch) for the B1 Business District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Business District (Bl) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration Trench
(Rooftop
disconnected)
A
0.045
484
42,064
0.350
$1,616
B
-
-
-
-
-
C
0.004
42
2,681
0.028
$140
Infiltration Basin
(Other IC
disconnected)
A
0.053
571
50,004
0.417
$952
B
-
-
-
-
-
C
0.005
49
3,039
0.034
$82
Agriculture
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Commercial
Infiltration Trench
(Rooftop
disconnected)
A
1.957
21,257
1,846,809
22.161
$70,986
B
-
-
-
-
-
C
2.087
22,666
1,450,334
22.184
$75,690
Infiltration Basin
(Other IC
disconnected)
A
4.036
43,838
3,841,518
46.169
$73,136
B
-
-
-
-
-
C
4.304
46,744
2,876,950
45.748
$77,984
Industrial
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Medium Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
0.254
2,762
239,945
2.649
$9,222
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
0.504
5,470
479,331
5.300
$9,126
B
-
-
-
-
-
C
-
-
-
-
-
High Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
0.097
1,058
91,935
1.015
$3,534
B
-
-
-
-
-
C
0.001
7
470
0.007
$24
Infiltration Basin
(Other IC
disconnected)
A
0.098
1,064
93,196
1.030
$1,774
B
-
-
-
-
-
C
0.001
7
455
0.007
$12
26
-------
Infiltration Gl SCM Solution (0.4 inch) for Business District (Bl) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Open Land
Infiltration Trench
(Rooftop
disconnected)
A
0.000
0
10
0.000
So
B
-
-
-
-
-
C
0.000
3
165
0.002
$8
Infiltration Basin
(Other IC
disconnected)
A
0.002
19
1,652
0.014
$32
B
-
-
-
-
-
C
0.040
429
26,427
0.291
$716
Total
Infiltration Trench
(Rooftop
disconnected)
A
2.353
25,562
2,220,763
26.175
$85,358
B
-
-
-
-
-
C
2.092
22,718
1,453,649
22.220
$75,864
Infiltration Basin
(Other IC
disconnected)
A
4.692
50,961
4,465,702
52.930
$85,020
B
-
-
-
-
-
C
4.348
47,230
2,906,870
46.080
$78,796
27
-------
3.3 B2 Light Business District
Figure 7 presents the HRUs for the B1 Business District zone. The majority of land in the district is pervious
surfaces, with 43% of the land consisting of rooftops and other impervious surfaces. Figure 8 presents the GI
SCM opportunities for the area. A 0.4 inch design criteria achieved a 91% reduction in flow volume and a
96% reduction in TN loading (Figure 9). The reductions were achieved at a cost of $1,130,554.
28
-------
Pervious Area
i Rooftop Area
i Other Impervious Area
01
0.5
1 mi
Zone: B2 Light Business District
Legend
CH Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
CD
CD
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
_IMP
Pervious,
Pervious _
Pervious,
Pervious,
Pervious
Pervious,
Pervious
Pervious
Pervious,
Pervious
_A_High
_A_Low
A. Medium
B High
B_Low
_B_Medium
A_High
A_Low
A_ Medium
B_High
B_Low
B Medium
C_High
C_Low
C_Medium
D_High
Developed Pervious_D_Low
Developed Pervious, D. Medium
Forest Pervious _A_ High
Forest Pervious A. Lovv
Forest Pervious,A Medium
Forest Pervbus_B_High
Forest Pervbus_B_Lovv
Forest Rerv»us_B_Medium
Forest_IMP
Open Land_IMP
Commercial_IMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
InaustriaT_IMP
Water
Figure 7. HRU distribution in the B2 Light Business District Zone of Tisbury, MA,
29
-------
Zone: B2 Light Business District
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
Figure 8. G! SCM opportunities in the B2 Light Business District Zone of Tisbury, MA.
30
-------
Cost-Effective Curve for Light Business District (B2)
$6,000,000
$5,000,000
vv $4,000,000
o
-------
Table 12. Infiltration Gl SCM Solution (0.4 inch) for the B1 Business District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Light Business District (B2) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load SCM Cos-
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration
Trench
(Rooftop
disconnected)
A
0.066
720
62,586
0.521
$2,406
B
0.005
55
4,062
0.039
$184
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
1.980
21,509
1,884,859
15.712
$35,884
B
0.152
1,651
120,495
1.157
$2,754
C
-
-
-
-
-
Agriculture
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Commercial
Infiltration
Trench
(Rooftop
disconnected)
A
6.020
65,385
5,680,607
68.166
$218,344
B
0.097
1,054
77,447
1.065
$3,520
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
27.418
297,812
26,097,210
313.647
$496,850
B
0.442
4,802
350,501
4.853
$8,012
C
-
-
-
-
-
Industrial
Infiltration
Trench
(Rooftop
disconnected)
A
2.188
23,769
2,065,064
24.780
$79,374
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
12.662
137,528
12,051,494
144.840
$229,442
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.030
327
28,448
0.314
$1,094
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
0.228
2,472
216,616
2.395
$4,124
B
-
-
-
-
-
C
-
-
-
-
-
Medium Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.109
1,181
102,600
1.133
$3,944
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
0.740
8,036
704,180
7.786
$13,406
B
-
-
-
-
-
C
-
-
-
-
-
High Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.163
1,766
153,434
1.694
$5,898
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
0.316
3,433
300,817
3.326
$5,728
B
-
-
-
-
-
C
-
-
-
-
-
32
-------
Infiltration Gl SCM Solution (0.4 inch) for Light Business District (B2) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load SCM Cos-
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Open Land
Infiltration
Trench
(Rooftop
disconnected)
A
0.044
475
41,273
0.344
$1,586
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
0.994
10,792
945,727
7.884
$18,006
B
-
-
-
-
-
C
-
-
-
-
-
Total
Infiltration
Trench
(Rooftop
disconnected)
A
8.620
93,625
8,134,013
96.952
$312,644
B
0.102
1,110
81,509
1.104
$3,706
C
-
-
-
-
-
Infiltration
Basin
(OtherIC
disconnected)
A
44.337
481,582
42,200,903
495.591
$803,440
B
0.594
6,453
470,995
6.010
$10,766
C
-
-
-
-
-
33
-------
3.4 LHP Lagoon Harbor Park
Figure 10 presents the HRUs for the Lagoon Harbor Park Zone. The majority of land in the district is
pervious surfaces, with 25% of the area consisting of rooftops and other impervious surfaces. The GIS
analyses did not identify any opportunities of GI SCM implementation in the area (Figure 11) due to
proximity to mapped wetlands (Table 1), these areas present regulatory and physical barriers that limit the
feasibility of infiltration-based opportunities. Given the lack of GI SCM implementation in the Lagoon
Harbor Park zone, no cost effectiveness curves were generated. The analysis was based on desktop review
of geospatial data, on-the-ground field assessment may help identify opportunities missed in this assessment.
34
-------
¦ Pervious Area
¦ Other Impervious Area
Zone: LHP Lagoon Harbor Park
Legend
CH Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
CD
CD
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
JMP
Pervious,
Pervious _
Pervious,
Pervious,
Pervious
Pervious,
Pervious
Pervious
Pervious,
Pervious
_A_High
_A_Low
AMedium
B High
B_Low
_B_Medium
A_High
A_Low
A_ Medium
B_High
B_Low
B Medium
C_High
C_Low
C_Medium
D_High
Developed Pervious_D_Low
Developed Pervious, D. Medium
Forest Pervious ,A, High
Forest Pervious A. Lovv
Forest (Pervious,A Medium
Forest Pervbus_B_High
Forest Pervbus_B_Lovv
Forest Rervtous_B_Medium
Forest_IMP
Open Land_IMP
Commercial_IMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
InaustriaT_IMP
Water
Figure 10. HRU distribution in the Lagoon Harbor Park Zone of Tisbury, MA.
35
-------
Zone: LHP Lagoon Harbor Park
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
Figure 11. G! SCM opportunities in the Lagoon Harbor Park Zone of Tisbury, MA,
36
-------
3.5 R3A Residential District
Figure 12 presents the HRUs for the R3A Residential District Zone. The majority of land in the district is
pervious surfaces, with only 6% of the area consisting of rooftops and other impervious surfaces. Figure 13
presents the GI SCM opportunities in the area. A 0.4 inch design criteria achieved a 57% reduction in flow
volume and a 54% reduction in TN loading (Figure 14). The reductions were achieved at a cost of
$1,608,886. Interestingly, the TN and flow curves cross each other at a relatively small design interval
(approximately 0.3 inches). The graph suggests that managing TN in the R3A residential zone through GI
SCM implementation to treat impervious surfaces becomes exceedingly expensive with little improvement
to load reductions. This is likely because the zone is dominated by pervious surfaces, including agriculture,
the TN loading from which is not treated in this analysis by the GIS SCM opportunities.
37
-------
¦ Pervious Area
¦ Rooftop Area
¦ Other Impervious Area
Zone: R3A Residential District
Legend
CH Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
CD
CD
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
JMP
Pervious,
Pervious _
Pervious,
Pervious,
Pervious
Pervious,
Pervious
Pervious
Pervious,
Pervious
_A_High
_A_Low
A. Medium
B High
B_Low
_B_Medium
A_High
A_Low
A_ Medium
B_High
B_Low
B Medium
C_High
C_Low
C_Medium
D_High
Developed Pervious_D_Low
Developed Pervious, D. Medium
Forest Pervious _A_ High
Forest Pervious A. Lovv
Forest Pervious,A Medium
Forest Pervious_B_High
Forest Pervbus_B_Lovv
Forest Rerv»us_B_Medium
Forest JMP
Open Land_IMP
Commercial_IMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
InaustriaT_IMP
Water
Figure 12. HRU distribution in the R3A Residential District Zone of Tisbury, MA.
38
-------
Figure 13. G! SCM opportunities in the R3A Residential District Zone of Tisbury, MA.
Zone: R3A Residential District
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
39
-------
$9,000,000
$8,000,000
$7,000,000
g $6,000,000
4->
(/)
5 $5,000,000
Cost-Effective Curve for Residential District (R3A)
- 0.1 inch
0.6 inch
1.5 inch
-TN Load Reduction (%)
0.2 inch
0.8 inch
2 inch
X Selected Solution (Flow)
0.4 inch
1 inch
-¦— Flow Volume Reduction (%)
X Selected Solution (TN)
30% 40% 50% 60%
Average Annual Reduction (%)
100%
Figure 14. Cost effectiveness curves for incremental sizing of Gl SCM opportunities in the R3A Residential District
Zone of Tisbury, MA.
40
-------
Table 13. Infiltration Gl SCM Solution (0.4 inch) for the R3A Residential District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R3A) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration
Trench
(Rooftop
disconnected)
A
0.752
8,168
709,608
5.906
$27,274
B
0.226
2,450
179,990
1.717
$8,182
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
32.876
357,096
31,292,214
260.857
$595,756
B
9.862
107,118
7,818,943
75.088
$178,710
C
-
-
-
-
-
Agriculture
Infiltration
Trench
(Rooftop
disconnected)
A
0.697
7,569
657,580
5.473
$25,276
B
0.241
2,622
192,633
1.838
$8,756
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
4.343
47,170
4,133,460
34.457
$78,694
B
1.505
16,342
1,192,827
11.455
$27,264
C
-
-
-
-
-
Commercial
Infiltration
Trench
(Rooftop
disconnected)
A
0.125
1,359
118,047
1.417
$4,538
B
0.031
340
24,993
0.344
$1,136
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
0.360
3,911
342,716
4.119
$6,524
B
0.090
979
71,480
0.990
$1,634
C
-
-
-
-
-
Industrial
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
6.768
73,517
6,387,061
70.511
$245,498
B
1.337
14,524
1,066,935
13.503
$48,498
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
11.037
119,876
10,504,730
116.149
$199,994
B
2.180
23,682
1,728,636
22.019
$39,510
C
-
-
-
-
-
Medium Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
High Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
41
-------
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R3A) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Open Land
Infiltration
Trench
(Rooftop
disconnected)
A
0.115
1,251
108,673
0.905
$4,178
B
0.165
1,787
131,308
1.253
$5,968
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
2.306
25,047
2,194,856
18.297
$41,786
B
3.295
35,791
2,612,509
25.089
$59,712
C
-
-
-
-
-
Total
Infiltration
Trench
(Rooftop
disconnected)
A
8.457
91,863
7,980,969
84.212
$306,762
B
2.000
21,723
1,595,859
18.656
$72,542
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
50.922
553,100
48,467,977
433.878
$922,756
B
16.932
183,912
13,424,395
134.640
$306,828
C
-
-
-
-
-
3.6 RIO Residential District
Figure 15 presents the HRUs for the RIO Residential District Zone. The majority of land in the district is
pervious surfaces, with 28% of the area consisting of rooftops and other impervious surfaces. Figure 16
presents the GI SCM opportunities in the area. A 0.4 inch design criteria achieved an 89% reduction in flow
volume and a 93% reduction in TN loading (Figure 17). The reductions were achieved at a cost of
$4,169,444.
42
-------
¦ Pervious Area
¦ Rooftop Area
¦ Other Impervious Area
Zone: RIO Residential District
Legend
CH Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
CD
CD
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
JMP
Pervious,
Pervious _
Pervious,
Pervious,
Pervious
Pervious,
Pervious
Pervious
Pervious,
Pervious
_A_High
_A_Low
A, Medium
B High
B_Low
_B_Medium
A_High
A_Low
A, Medium
B_High
B_Low
B Medium
C_High
C_Low
C_Medium
D_High
Developed Pervious_D_Low
Developed Pervious, D_Medium
Forest PsrvbusAHigh
Forest Pervbus_A_Low
Forest Pervbus,A_Medium
Forest Pervbus_B_High
Forest Pervbus_B_Low
Forest Rervbus„B_Medium
Forest JMP
Open Land IMP
CommerciaLIMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
InaustriaT_IMP
Water
Figure 15. HRU distribution in the R10 Residential District Zone of Tisbury, MA.
43
-------
Zone: RIO Residential District
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
Figure 16. GI SCM opportunities in the R10 Residential District Zone of Tisbury, MA.
44
-------
Cost-Effective Curve for Residential District (RIO)
$25,000,000
$20,000,000
g $15,000,000
u
$10,000,000
$5,000,000
- 0.1 inch
0.6 inch
1.5 inch
-TN Load Reduction (%)
0.2 inch
0.8 inch
¦ 2 inch
Selected Solution (Flow)
0.4 inch
1 inch
- Flow Volume Reduction (%)
Selected Solution (TN)
- - <
\ 93%, $4,169,444 |
i
r
I 89%, $4,169,444
w' A
0% 10% 20% 30% 40% 50% 60%
Average Annual Reduction (%)
70%
80%
90%
100%
Figure 17. Cost effectiveness curves for incremental sizing of Gl SCM opportunities in the R10 Residential District
Zone of Tisbury, MA.
45
-------
Table 14. Infiltration Gl SCM Solution (0.4 inch) for the R10 Residential District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Residential District (RIO) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration
Trench
(Rooftop
disconnected)
A
1.669
18,124
1,574,573
13.106
$60,522
B
0.016
173
12,739
0.122
$580
C
0.004
40
2,551
0.027
$134
Infiltration Basin
(Other IC
disconnected)
A
9.901
107,543
9,423,987
78.560
$179,418
B
0.095
1,029
75,111
0.721
$1,716
C
0.022
237
14,558
0.161
$394
Agriculture
Infiltration
Trench
(Rooftop
disconnected)
A
0.006
70
6,063
0.050
$234
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Commercial
Infiltration
Trench
(Rooftop
disconnected)
A
2.197
23,862
2,073,142
24.877
$79,684
B
-
-
-
-
-
C
0.029
320
20,498
0.314
$1,070
Infiltration Basin
(Other IC
disconnected)
A
6.212
67,474
5,912,736
71.062
$112,570
B
-
-
-
-
-
C
0.083
906
55,751
0.887
$1,512
Industrial
Infiltration
Trench
(Rooftop
disconnected)
A
0.031
333
28,915
0.347
$1,112
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
0.497
5,395
472,746
5.682
$9,000
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
5.491
59,641
5,181,553
57.203
$199,162
B
0.029
311
22,868
0.289
$1,040
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
18.402
199,880
17,515,429
193.664
$333,466
B
0.096
1,043
76,149
0.970
$1,740
C
-
-
-
-
-
Medium Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
38.645
419,758
36,468,186
402.597
$1,401,714
B
-
-
-
-
-
C
0.000
2
Ill
0.002
$6
Infiltration Basin
(Other IC
disconnected)
A
83.954
911,884
79,908,082
883.527
$1,521,326
B
-
-
-
-
-
C
0.000
4
232
0.003
$6
High Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.924
10,038
872,102
9.628
$33,520
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
1.310
14,228
1,246,779
13.785
$23,736
B
-
-
-
-
-
C
-
-
-
-
-
46
-------
Infiltration Gl SCM Solution (0.4 inch) for Residential District (RIO) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
$2,382
B
-
-
-
-
-
C
-
-
-
-
$558
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
$164,380
B
-
-
-
-
-
C
-
-
-
-
$38,464
Open Land
Infiltration
Trench
(Rooftop
disconnected)
A
0.066
713
61,981
0.516
$2,382
B
-
-
-
-
-
C
0.015
167
10,681
0.113
$558
Infiltration Basin
(Other IC
disconnected)
A
9.071
98,530
8,634,143
71.976
$164,380
B
-
-
-
-
-
C
2.123
23,055
1,418,955
15.651
$38,464
Total
Infiltration
Trench
(Rooftop
disconnected)
A
49.029
532,539
46,266,515
508.323
$1,778,330
B
0.045
485
35,607
0.411
$1,618
C
0.049
529
33,841
0.455
$1,766
Infiltration Basin
(Other IC
disconnected)
A
129.347
1,404,934
123,113,903
1,318.256
$2,343,898
B
0.191
2,072
151,259
1.691
$3,458
C
2.228
24,201
1,489,497
16.701
$40,376
47
-------
3.7 R20 Residential District
Figure 18 presents the HRUs for the R20 Residential District Zone. The majority of land in the district is
pervious surfaces, with 22% of the area consisting of rooftops and other impervious surfaces. Figure 19
presents the GISCM opportunities in the area. A 0.4 inch design criteria achieved an 87% reduction in flow
volume and a 92% reduction in TN loading (Figure 20). The reductions were achieved at a cost of
$1,599,198.
48
-------
Pervious Area
Rooftop Area
Other Impervious Area
Zone: R20 Residential District
Legend
CH Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
CD
CD
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
JMP
Pervious,
Pervious _
Pervious,
Pervious,
Pervious
Pervious,
Pervious
Pervious
Pervious,
Pervious
_A_High
_A_Low
AMedium
B High
B_Low
_B_Medium
A_High
A_Low
A_ Medium
B_High
B_Low
B Medium
C_High
C_Low
C_Medium
D_High
Developed Pervious_D_Low
Developed Pervious, D. Medium
Forest Pervious _A_ High
Forest Pervious A. Lovv
Forest (Pervious,A Medium
Forest Pervbus_B_High
Forest Pervbus_B_Lovv
Forest Rerv»us_B_Medium
Forest_IMP
Open Land_IMP
Commercial_IMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
InaustriaT_IMP
Water
Figure 18. HRU distribution in the R20 Residential District Zone of Tisbury, MA.
49
-------
Zone: R20 Residential District
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
Figure 19. GI SCM opportunities in the R20 Residential District Zone of Tisbury, MA.
50
-------
$9,000,000
$8,000,000
$7,000,000
S? $6,000,000
4-J
n
° $5,000,000
+->
Is $4,000,000
$3,000,000
$2,000,000
$1,000,000
$-
Cost-Effective Curve for Residential District (R20)
- 0.1 inch
0.6 inch
1.5 inch
-TN Load Reduction (
0.2 inch
0.8 inch
2 inch
X Selected Solution (Flow)
0.4 inch
1 inch
-¦— Flow Volume Reduction (%)
X Selected Solution (TN)
0% 10% 20% 30% 40% 50% 60%
Average Annual Reduction (%)
70%
80%
90%
100%
Figure 20, Cost effectiveness curves for incremental sizing of Gl SCM opportunities in the R20 Residential District
Zone of Tisbury, MA.
51
-------
Table 15. Infiltration Gl SCM Solution (0.4 inch) for the R20 Residential District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R20) in Tisbury
Land Use Group SCM Type HSG |C Disconnected St0rage Flow Volume TN Load
. . Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration Trench
(Rooftop
disconnected)
A
0.810
8,795
764,139
6.360
$29,370
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
12.024
130,606
11,444,921
95.407
$217,894
B
-
-
-
-
-
C
-
-
-
-
-
Agriculture
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Commercial
Infiltration Trench
(Rooftop
disconnected)
A
0.613
6,654
578,059
6.937
$22,218
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
2.280
24,762
2,169,927
26.079
$41,312
B
-
-
-
-
-
C
-
-
-
-
-
Industrial
Infiltration Trench
(Rooftop
disconnected)
A
0.386
4,198
364,697
4.376
$14,018
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
4.521
49,101
4,302,694
51.712
$81,916
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
12.053
130,920
11,374,174
125.567
$437,184
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
30.302
329,129
28,841,502
318.894
$549,098
B
-
-
-
-
-
C
-
-
-
-
-
Medium Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
0.305
3,312
287,747
3.177
$11,060
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
1.119
12,158
1,065,442
11.780
$20,284
B
-
-
-
-
-
C
-
-
-
-
-
High Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
0.759
8,245
716,337
7.908
$27,534
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
2.299
24,969
2,188,038
24.193
$41,656
B
-
-
-
-
-
C
-
-
-
-
-
52
-------
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R20) in Tisbury
Land Use Group SCM Type HSG |C Disconnected St0rage Flow Volume TN Load
. . Capacity Captured Removed
aCrSS (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Open Land
Infiltration Trench
(Rooftop
disconnected)
A
0.531
5,763
500,643
4.167
$19,244
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
4.768
51,793
4,538,596
37.834
$86,408
B
-
-
-
-
-
C
-
-
-
-
-
Total
Infiltration Trench
(Rooftop
disconnected)
A
15.457
167,886
14,585,796
158.492
$560,628
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
57.313
622,519
54,551,120
565.899
$1,038,568
B
-
-
-
-
-
C
-
-
-
-
-
53
-------
3.8 R25 Residential District
Figure 21 presents the HRUs for the R25 Residential District Zone. The majority of land in the district is
pervious surfaces, with 16% of the area consisting of rooftops and other impervious surfaces. Figure 22
presents the GISCM opportunities in the area. A 0.4 inch design criteria achieved an 81% reduction in flow
volume and an 84% reduction in TN loading (Figure 23). The reductions were achieved at a cost of
$1,270,025.
54
-------
¦ Pervious Area
¦ Rooftop Area
¦ Other Impervious Area
Zone: R25 Residential District
Legend
CH Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
CD
CD
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
JMP
Pervious,
Pervious _
Pervious,
Pervious,
Pervious
Pervious,
Pervious
Pervious
Pervious,
Pervious
_A_High
_A_Low
A, Medium
B High
B_Low
_B_Medium
A_High
A_Low
A, Medium
B_High
B_Low
B Medium
C_High
C_Low
C_Medium
D_High
Developed Pervious_D_Low
Developed Pervious, D_Medium
Forest PsrvbusAHigh
Forest Pervbus_A_Low
Forest Pervbus,A_Medium
Forest Pervbus_B_High
Forest Pervbus_B_Low
Forest Rervbus„B_Medium
Forest JMP
Open Land IMP
CommerciaLIMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
InaustriaT_IMP
Water
Figure 21. HRU distribution in the R25 Residential District Zone of Tisbury, MA.
55
-------
Figure 22. G! SCM opportunities in the R25 Residential District Zone of Tisbury, MA.
56
-------
Cost-Effective Curve for Residential District (R25)
$7,000,000
$6,000,000
$5,000,000
O $4,000,000
$2,000,000
$1,000,000
- 0.1 inch
0.6 inch
- 1.5 inch
-TN Load Reduction (%)
0.2 inch
0.8 inch
2 inch
X Selected Solution (Flow)
0.4 inch
1 inch
-¦— Flow Volume Reduction (%)
X Selected Solution (TN)
-
y-
"
84%, $1,270,02
tU
1
81%, $1,270,025 _
A
~
30% 40% 50% 60%
Average Annual Reduction (%)
Figure 23. Cost effectiveness curves for incremental sizing of Gl SCM opportunities in the R25 Residential District
Zone of Tisbury, MA.
57
-------
Table 16. Infiltration Gl SCM Solution (0.4 inch) for the R50 Residential District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R25) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration
Trench
(Rooftop
disconnected)
A
0.631
6,858
595,781
4.959
$22,900
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
7.361
79,951
7,006,048
58.404
$133,384
B
-
-
-
-
-
C
-
-
-
-
-
Agriculture
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
0.114
1,243
108,896
0.908
$2,074
B
-
-
-
-
-
C
-
-
-
-
-
Commercial
Infiltration
Trench
(Rooftop
disconnected)
A
0.504
5,470
475,242
5.703
$18,266
B
-
-
-
-
-
C
0.070
765
48,934
0.748
$2,554
Infiltration Basin
(OtherIC
disconnected)
A
1.228
13,340
1,168,965
14.049
$22,256
B
-
-
-
-
-
C
0.172
1,865
114,783
1.825
$1,556
Industrial
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
4.065
44,157
3,836,318
42.352
$147,456
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
7.355
79,889
7,000,638
77.405
$133,282
B
-
-
-
-
-
C
-
-
-
-
-
Medium Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
10.635
115,511
10,035,527
110.789
$385,732
B
-
-
-
-
-
C
0.000
2
132
0.002
$1,556
Infiltration Basin
(OtherIC
disconnected)
A
17.123
185,986
16,297,919
180.203
$310,288
B
-
-
-
-
-
C
0.000
3
205
0.003
$1,556
High Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.332
3,607
313,397
3.460
$12,046
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
0.407
4,423
387,605
4.286
$7,380
B
-
-
-
-
-
C
-
-
-
-
-
58
-------
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R25) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
0.012
134
8,260
0.079
$224
Open Land
Infiltration
Trench
(Rooftop
disconnected)
A
0.226
2,455
213,318
1.776
$8,200
B
-
-
-
-
-
C
0.000
1
32
0.000
$2
Infiltration Basin
(OtherIC
disconnected)
A
3.358
36,473
3,196,145
26.644
$60,850
B
-
-
-
-
-
C
0.001
7
458
0.005
$12
Total
Infiltration
Trench
(Rooftop
disconnected)
A
16.393
178,059
15,469,584
169.037
$594,598
B
-
-
-
-
-
C
0.071
767
49,098
0.751
$2,562
Infiltration Basin
(OtherIC
disconnected)
A
36.947
401,305
35,166,217
361.897
$669,510
B
-
-
-
-
-
C
0.185
2,010
123,705
1.912
$3,354
59
-------
3.9 R50 Residential District
Figure 24 presents the HRUs for the R50 Residential District Zone. The majority of land in the district is
pervious surfaces, with 11% of the area consisting of rooftops and other impervious surfaces. Figure 25
presents the GI SCM opportunities in the area. A 0.4 inch design criteria achieved a 75% reduction in flow
volume and a 76% reduction in TN loading (Figure 26). The reductions were achieved at a cost of
$2,816,910.
60
-------
Zone: R50 Residential District
Legend
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Agriculture
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
Developed
en
~
CD
CD
CD
CD
CD
CD
Pervious
Pervious
Pervious
Pervious
Pervious
Pervious
IMP
Pervious,
Pervious.
Pervious
Pervious,
Pervious
Pervious,
Pervious _
Pervious _
Pervious,
Pervious
_A_High
_A_Low
A_ Medium
_B_High
_B,Low
_B_Medium
A_High
A, Low
A. Medium
B_High
B_Low
B_Medium
C_High
C_Low
C_ Medium
D..High
Developed Pervious_D_Low
Developed Pervious D._Medium
Forest Pervious,A,High
Forest PferviousALow
Forest Rervious„A_Medium
Forest flervious_B_High
Forest Pervbus_B_Low
Forest Ftervk>us_B_Medium
Forest,IMP
Open Land IMP
CommerciaLIMP
Low Density Residential_IMP
Medium Density ResidentiaLIMP
High Density ResidentiaLIMP
Highway IMP
IndustriaT_IMP
Water
Figure 24. HRU distribution in the R50 Residential District Zone of Tisbury, MA.
¦ Pervious Area
¦ Rooftop Area
¦ Other Impervious Area
61
-------
N
o
0.5
1 mi
Zone: R50 Residential District
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
Figure 25. GI SCM opportunities in the R50 Residential District Zone of Tisbury, MA.
62
-------
Cost-Effective Curve for Residential District (R50)
$16,000,000
$14,000,000
$12,000,000
$10,000,000
o
(J
jj $8,000,000
$6,000,000
$4,000,000
$2,000,000
$-
- 0.1 inch
0.6 inch
1.5 inch
-TN Load Reduction (%)
0.2 inch
0.8 inch
2 inch
X Selected Solution (Flow)
0.4 inch
1 inch
-¦— Flow Volume Reduction (%)
X Selected Solution (TN)
~ --1
~ 1
76%, $2,816,910
i
~ ¦
75%, $2,816,910
10% 20% 30% 40% 50% 60%
Average Annual Reduction (%)
70%
80%
90%
100%
Figure 26. Cost effectiveness curves for incremental sizing of Gl SCM opportunities in the R50 Residential District
Zone of Tisbury, MA.
63
-------
Table 17. Infiltration Gl SCM Solution (0.4 inch) for the R50 Residential District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R50) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration Trench
(Rooftop
disconnected)
A
1.907
20,708
1,799,132
14.975
$69,152
B
0.026
278
20,397
0.195
$928
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
53.779
584,138
51,187,800
426.710
$974,536
B
0.721
7,832
571,679
5.490
$13,066
C
-
-
-
-
-
Agriculture
Infiltration Trench
(Rooftop
disconnected)
A
0.083
903
78,444
0.653
$3,016
B
0.000
2
117
0.001
$6
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
1.893
20,566
1,802,187
15.023
$34,310
B
0.003
36
2,653
0.025
$60
C
-
-
-
-
-
Commercial
Infiltration Trench
(Rooftop
disconnected)
A
0.390
4,231
367,558
4.411
$14,128
B
0.002
18
1,327
0.018
$60
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
0.848
9,210
807,042
9.699
$15,364
B
0.004
39
2,871
0.040
$66
C
-
-
-
-
-
Industrial
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
18.279
198,544
17,249,302
190.427
$663,006
B
0.253
2,750
202,021
2.557
$9,184
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
33.765
366,752
32,138,346
355.347
$611,864
B
0.468
5,080
370,791
4.723
$8,474
C
-
-
-
-
-
Medium Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
0.781
8,484
737,090
8.137
$28,332
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
2.256
24,502
2,147,113
23.740
$40,878
B
-
-
-
-
-
C
-
-
-
-
-
High Density Residential
Infiltration Trench
(Rooftop
disconnected)
A
2.261
24,564
2,134,086
23.560
$82,028
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
3.598
39,084
3,424,939
37.869
$65,206
B
-
-
-
-
-
C
-
-
-
-
-
64
-------
Infiltration Gl SCM Solution (0.4 inch) for Residential District (R50) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Open Land
Infiltration Trench
(Rooftop
disconnected)
A
0.421
4,576
397,554
3.309
$15,280
B
0.001
6
413
0.004
$18
C
-
-
-
-
-
Infiltration Basin
(Other IC
disconnected)
A
9.257
100,545
8,810,698
73.447
$167,742
B
0.011
124
9,026
0.087
$206
C
-
-
-
-
-
Total
Infiltration
Trench
(Rooftop
disconnected)
A
24.122
262,010
22,763,165
245.470
$874,940
B
0.281
3,053
224,275
2.775
$10,194
C
-
-
-
-
-
Infiltration Basin
(OtherIC
disconnected)
A
105.397
1,144,796
100,318,125
941.836
$1,909,902
B
1.207
13,111
957,019
10.365
$21,874
C
-
-
-
-
-
65
-------
3.10 WC Waterfront Commercial District
Figure 27 presents the HRUs for the Waterfront Commercial District. Over half (54%) of the land in the
district consists of rooftops and other impervious surfaces. The zone has limited opportunities for GI SCM
implementation (Figure 28). The majority of pervious surfaces that could represent opportunities for GI
SCM installation are in in areas associated with complicating factors, these areas include close proximity to
coastlines, wetlands and structures (Table 1). The analysis was based on desktop review of geospatial data,
on-the-ground field assessment may help identify opportunities missed in this assessment. A 0.4 inch design
criteria achieved a 63% reduction in flow volume and an 84% reduction in TN loading (Figure 29). The
reductions were achieved at a cost of $619,698.
66
-------
Zone: W/C Waterfront Commercial
Legend
~ Agriculture Pervious A High EE Developed Pervious_D_Lx)w
CD Agriculture FterviouslA.Low n Developed Pervious D Medium
d) Agriculture Pervious. A. Medium ™ Forest Pervious A High
~ Agriculture Pervious B High ™ Forest Perv»us_A_Low
~ Agriculture Pervious"B_Low ¦ Bsrvous_A_Medium
~ Agriculture Pervious B Medium ¦ Pores* Pei^»us_B_High
1=) Agriculture IMP m rest
cd Developed Pervious_A_High ™ Forest Pervious_B_Medium
CD Developed Pervious _A Low m1 Forest IIMP
~ Developed Pervious _A Medium 1=1 2pen ,
CD Developed Psrvious_B_High 1=1 Commercial IMP
cu Developed Ftervious B Low n Low Density ResidentialJMP
1=1 Developed FterviouslB" Medium ¦ Medium Density ResidentialJMI
CD Developed Ften/ious_C_High ¦ High Density ResidentialJMP
CD Developed Pervious_C_Low Highway IMP
CZ3 Developed Pervious_C_Medium l=1 Indus tna LI MP
~ Developed Pervious_D_High ™ Water
Figure 27. HRU distribution in the Waterfront Commercial Zone of Tisbury, MA.
67
-------
Zone: W/C Waterfront Commercial
Legend
Roads
I I Rooftops
GI SCM opportunity
Infiltration
I I Rooftop disconnection
Figure 28. G! SCM opportunities in the Waterfront Commercial Zone of Tisbury, MA.
68
-------
$3,500,000
$3,000,000
$2,500,000
O $2,000,000
$1,000,000
$500,000
$-
0%
Cost-Effective Curve for Waterfront Commercial (W/C)
- 0.1 inch
0.6 inch
1.5 inch
-TN Load Reduction (%)
0.2 inch
0.8 inch
2 inch
X Selected Solution (Flow)
0.4 inch
1 inch
-¦— Flow Volume Reduction (%)
X Selected Solution (TN)
H
a
J
84%, $619,698
/
- - - j
63%, $619,698 |_-
1
10%
20%
30% 40% 50% 60%
Average Annual Reduction (%)
70%
90%
100%
Figure 29. Cost effectiveness curves for incremental sizing of Gl SCM opportunities in the Waterfront Commercial
District Zone of Tisbury, MA.
69
-------
Table 18. Infiltration Gl SCM Solution (0.4 inch) for the Waterfront Commercial District of Tisbury, MA
Infiltration Gl SCM Solution (0.4 inch) for Waterfront Commercial (W/C) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load SCM Cost
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Forest
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration
Basin
(Other IC
disconnected)
A
0.293
3,186
279,179
2.327
$5,316
B
-
-
-
-
-
C
-
-
-
-
-
Agriculture
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration
Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Commercial
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
3.825
41,548
2,658,522
40.663
$138,744
Infiltration
Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
11.798
128,150
7,887,252
125.421
$213,796
Industrial
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration
Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
-
-
-
-
-
Low Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
0.017
180
15,623
0.172
$600
B
-
-
-
-
-
C
-
-
-
-
-
Infiltration
Basin
(Other IC
disconnected)
A
0.305
3,317
290,703
3.214
$5,534
B
-
-
-
-
-
C
-
-
-
-
-
Medium Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
0.258
2,802
179,296
2.523
$9,358
Infiltration
Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
0.483
5,247
322,950
4.725
$8,754
High Density Residential
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
0.226
2,453
156,970
2.209
$8,192
Infiltration
Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
0.599
6,511
400,756
5.863
$10,864
70
-------
Infiltration Gl SCM Solution (0.4 inch) for Waterfront Commercial (W/C) in Tisbury
Land Use Group SCM Type HSG lc storage Flow Volume TN Load SCM Cost
Disconnected Capacity Captured Removed
(acres) (gallons) (gallons/yr) (Ibs/yr)
Highway
Infiltration
Trench
(Rooftop
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
0.211
2,289
146,493
1.341
$7,646
Infiltration
Basin
(Other IC
disconnected)
A
-
-
-
-
-
B
-
-
-
-
-
C
2.159
23,447
1,443,116
13.739
$39,118
Open Land
Infiltration
Trench
(Rooftop
disconnected)
A
0.000
5
425
0.004
$16
B
-
-
-
-
-
C
1.766
19,186
1,227,622
13.024
$64,068
Infiltration
Basin
(Other IC
disconnected)
A
0.002
16
1,441
0.012
$28
B
-
-
-
-
-
C
5.942
64,536
3,972,018
43.810
$107,668
Total
Infiltration
Trench
(Rooftop
disconnected)
A
0.017
185
16,048
0.176
$616
B
-
-
-
-
-
C
6.286
68,278
4,368,902
59.761
$228,004
Infiltration
Basin
(OtherIC
disconnected)
A
0.600
6,520
571,324
5.554
$10,878
B
-
-
-
-
-
C
20.981
227,892
14,026,092
193.557
$380,200
71
-------
4 ABILITY OF Gl SCM STRATEGIES TO ACHIEVE OBJECTIVES BEYOND
WATER RESOURCES MANAGEMENT
The implementation of GI SCM strategies can be part of larger community strategies that aim to improve
sustainability. Stormwater treatment can provide aesthetic, green spaces within the community (Figure 30).
Investment in GI SCM is generally publicly funding from federal, state, and local sources. The planning
design, construction and long-term maintenance of the GI SCM project can increase jobs and boost local
economies (U.S. EPA., 2015). Tree-box filters (Figure 31) require not only engineers and contractors to
design and install the system but can also support local tree nurseries.
GI SCM implementation plans should aim to safeguard, expand, and enhance a community's network of
parks, recreational trails, open spaces, and working and agricultural lands. To facilitate achieving co-benefits
from supporting GI SCM and urban agriculture, communities may consider listing stormwater management
as a benefit or definition of urban agriculture in planning materials and zoning codes, as well as offer farmers
funding and tax credits for impropriating GI SCM (American Rivers, 2015). The Commonwealth of
Massachusetts has approved science-related curriculums based on the numerous processes associated with
hydrology and the application of GI SCMs (MDESE, 2016). Boston has retrofitted several schools with GI
SCMs that are being used as part of hands-on science studies at the schools (presentation by BWSC, 2018).
Although GI/SCM implementation consistent with this project will help to offset the impact of climate
change storm events, this project did not specifically investigate climate resilience, particularly along the
coastline. Consequently, given the value of waterfront property generally, next-generation ordinance/bylaws
could be considered which require development/redevelopment practices to (a) eliminate/reduce IC, and
(b) provide for climate resilience mitigation, including some or all of the recommendations outlined in the
Tisbury Coastal Resilience Planning Report and more generally, next-generation architectural design and
materials.
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Figure 31. Treebox filter in San Diego, CA.
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5 SUMMARY
The Opti-Tool was used to provide a planning level evaluation of incrementally sized GISCM opportunities.
The analysis assessed 6 types of GI SCM opportunities in Tisbury's nine development zones. Overall the
analysis suggests that a 78% reduction in stormwater volume and an 81% reduction in TN can be achieved
at a cost of $13.54 million. These reductions are based on treating the 0.4 inches of runoff from roofs and
other impervious surfaces using infiltration-based techniques. The R3A residential district had the lowest
reductions as a result of GI SCM implementation, with storm flow volume and TN loading decreasing by
57% and 54%, respectively. Alternatively, the B2 light business district had the highest reductions as a result
of GI SCM implementation, with storm flow volume and TN loading decreasing by 91% and 96%,
respectively. The differences in cost effectiveness are a result of the HRU composition of the zoning districts.
The B2 light business district has a relatively high percentage of the total area as rooftop or other impervious
surfaces, with enough opportunities for GI SCM implementation. Much the stormwater volume and TN
loading were generated from impervious surfaces in this zone, and there is ample opportunity to treat the
runoff. The R3A residential district was a much more rural area and implementing GI SCM to treat the
relatively small (6%) of impervious area less of an impact than in more urban areas with enough
opportunities.
The results of this study provide support to the implementation of a town-wide strategy to install GI and
SCMs to help address flood mitigation by reducing stormwater volume and to improve water quality through
TN load reductions. A successful GI SCM implementation strategy should recognize and encourage the role
stormwater management can play in achieving other community objectives.
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REFERENCES
American Rivers. 2015. Urban Farms - A Green Infrastructure Tool for the Chesapeake Bay.
https: / /americanriver s. or g/wp-
content/uploads/2016/05/AmericanRivers UrbanAgricultureReport final.pdf
Massachusetts Department of Elementary and Secondary Education (MDESE). 2016. 2016 Massachusetts
Science and Technology/Engineering Curriculum Framework.
http://www.doe.mass.edu/frameworks/scitech/2016-04.pdf
U.S. EPA. 2015. Green Infrastructure Opportunities that Arise During Municipal Operations. EPA 842-R-15-002.
Office of Wetlands, Oceans and Watersheds, National Estuary Program.
https://www.epa.gov/sites/production/files/2015-
09/documents/green infrastructure roadshow.pdf
U.S. EPA. 2020. Opti-Tool Application for Two Pilot Drainage Areas (Outfall #2 and #7) to Evaluate Source Area
Contributions and GISCMReduction Benefits (Task 4c). Prepared for: U.S. EPA Region 1, Boston, MA.
Prepared by: Paradigm Environmental, Fairfax, VA.
U.S. EPA. 2019. Opti-Tool Analyses for Quantifying Stormwater Runoff Volume and Pollutant Loadings from
Watershed Source Areas (Task 4b). Prepared for: U.S. EPA Region 1, Boston, MA. Prepared by:
Paradigm Environmental, Fairfax, VA.
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