Introduction:
Acknowledgements: This program was funded by a grant from Coastal Zone
Management under the Coastal Pollution Remediation program to the Town of Oak
Bluffs Shellfish Department. The project represents a cooperative effort between that
Department, the two Town Departments of Public Works and the Martha’s Vineyard
Commission. The Tisbury DPW, Oak Bluffs Highway and Shellfish Departments and
Town Accountant and MV Commission provided in-kind matches for the grant to meet
the 25 percent requirement.
The project was greatly aided by the insights of Fred LaPiana, Tisbury DPW Director
and Richard Combra, Jr., Oak Bluffs Highway Director. Fieldwork was planned by Bill
Wilcox and largely carried out by Tonya Jilek, summer intern at the Martha’s Vineyard
Commission. Bob Ford, Wallace Ross and Sam Low mapped the catch basins on
Vineyard Avenue in Oak Bluffs. Dave Grunden, Oak Bluffs Shellfish Warden and Bill
Wilcox, MVC Water Resource Planner, prepared the grant proposal for this project.
Chris Seidel, MVC, created the GIS graphics from a vast array of field data.
Limitations of the Data Within This Report:
The majority of the basin locations
shown were mapped with a Trimble Geoexplorer Global Positioning System with
accuracy set to near the highest setting that should provide positions to within less than
10 feet. In some cases, 100 percent correction of the positions could not be obtained and
the basin locations may not plot up in the pattern they are found on the ground. As we
neared completion of the GPS mapping component and began the field mapping for
ground slope and extent of the runoff contributing areas for each system, we found
additional basins that were then mapped on the Assessor’s base map. These are
indicated on the map with a dot in the center of the symbol and may not have the same
accuracy when shifted to the aerial photo base map.
The roads in both Towns vary in width and presence or absence of sidewalks along their
lengths. As a result, the width of impervious surface varies along the length of the road.
The widths shown in the following Tables are based on several measurements but do not
represent a precise indication of the area of impervious cover. The impervious areas
calculated are reasonable approximations of the actual situation and provide a means for
comparing one system with another and prioritizing corrective actions. However, a field
survey must be conducted to calculate precise runoff values before designing
infiltrations systems.
On the maps of the collection system, portions of the roadway that are sloped to
contribute runoff to the actual collection system are shown. These areas were identified
in the field using the Assessor’s Map as a base and represent reasonable outlines of the
contribution areas. In addition, in some areas there is sloping ground that is out of the
roadway right of way that will add runoff to the system under the right rainfall intensity.
This is particularly so in the Tisbury Main Street and Oak Bluffs Circuit Avenue
collection systems where the development pattern is dense and the presence of on-lot
infiltration capacity is very limited. There are also paved parking areas that will add to
CPR Final Report
2
the volume of runoff from off-road land use areas. These parking areas are mentioned
in the text that follows but were not measured.
Stormwater Collection System- Town of Tisbury
Sources Not Mapped:
Three substantial stormwater systems within the Town
were not mapped as they have been corrected to a large extent by the installation of first
flush systems. These include the West Spring Street system that receives runoff from
the entire length of West Spring Street back to the grammar school as well as from side
streets. The runoff from this roadway exits via a pipe at the head of a small wetland
system fed by fresh springs that flow into Tashmoo Pond near the Tisbury Water
Department driveway. Drainage from Dunham and Skiff Avenue has been greatly
reduced by the installation of an infiltration system that intercepts a large part of the
runoff that once flowed into the West Arm of Lagoon Pond. Runoff from Lagoon Pond
Road formerly flowed down to a low area and into a catch basin that discharged directly
into the West Arm near the drain way for Ben Luce’s Pond. Infiltration capacity was
installed along the road right of way to reduce this source. To the east of the crest in
Lagoon Pond Road near the intersection with Weaver Lane, runoff formerly flowed
down the road to the southeast, across a short stretch of beach and into the main body of
Lagoon Pond. This source was also substantially reduced by the installation of
infiltration capacity along the road right of way.
General Stormwater System description: Tisbury Harbor is the recipient of runoff
from a large portion of the Town that is arrayed on the sloping ground around the
Harbor to the west and south. The Lagoon receives a lesser amount. Ground slope
toward the Harbor ranges from 8 to 15 percent as mapped by the USDA Natural
Resource Conservation Service. Soil type is not mapped in the urban areas but nearby in
all directions it is Carver loamy coarse sand that is a drouthy soil with significant
capacity to infiltrate runoff.
The stormwater system can be divided into two isolated systems serving Town roads,
two isolated systems serving segments of Beach Road (a State road), the Main Street
system and a system that partially links a State Road system to a Town system on
Causeway Road.
In addition, we identified a residential street system that discharges into the outer Harbor
across a 40-foot wide stretch of beach that showed signs of gullying from the volume of
discharge running out. All Tisbury systems mapped are shown in Figures 1 and 2.
Owen Little Way Discharge:
This discharge is a direct outflow into outer
Tisbury Harbor after passage through a number of recently installed first-flush basins
higher up in the watershed and near the discharge point. As installed, the Owen Little
Way system includes two sub-systems that, while they discharge next to each other, are
not directly linked. Both systems have first flush basins to reduce pollutant output that
consist of leaching pit systems with limestone rock at the bottom and oil absorbent pads
at the top. Over 30 of these basins were installed. Many of the streets are curbed
preventing loss of runoff onto roadsides.
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One segment includes collection along Main Street south of Daggett, Tashmoo,
Hemlock and Daggett. This runoff passes into a leaching gallery located near the Yacht
Club with excess runoff returning to the discharge pipe and into the outer harbor by
direct discharge. The other includes Main Street north of Daggett and Fairfield. The
entire watershed is moderate density residential (approximately ½ to 1 acre density).
These systems discharge via two 24-inch diameter pipes. During the August 5 rainfall
the pipes discharged a noticeably “sooty” looking runoff at high enough rates to roil the
surface of the water for some distance beyond the pipe. The data is reported in Table 21
as TIS1. Street length and area for the systems are reported in Table 1.
NOTE: IN ALL TABLES OF IMPERVIOUS SURFACES THE LENGTH OF THE STREETS
DIRECTLY OVER THE COLLECTION SYSTEM AND THE LENGTH OF STREETS THAT
SLOPE TO THE COLLECTION SYSTEM AND CONTRIBUTE TO IT ARE REPORTED
SEPARATELY.
System
North
South
Table 1: Owen Little Way Stormwater Discharge
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to collection system
Main
Main
Fairfield
N William
Hatch
Daggett
Daggett
Fairfield
N. William
Locust
Hemlock
Authier
Tashmoo
Tashmoo
Franklin
Main
Owen Little Way
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
30
30
21
28
18
27
25
21
24
18
19
15
26
26
32
30
20
1075
370
840
350
200
1040
700
650
840
540
335
300
790
160
2180
1440
590
5070
132360
7330
191465
Main Street- Steamship Authority Discharge:
This discharge is a direct outflow
into Tisbury Harbor. The Main Street system drains a large area of high-density (<1/4
acre) commercial and residential land use. The system discharges via a 36-inch
diameter pipe beneath the Steamship Authority pier. A large runoff contribution from
areas adjoining the streets is expected to add to the total volume discharged. Most of the
streets are curbed preventing loss of runoff onto roadsides. We were not able to obtain a
sample from this system due to the location of the discharge and hazards associated with
sampling at a site frequented by large vessels. In addition, runoff from two Town
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4
Parking lots and the Steamship Authority Parking lot add to the runoff on Water Street.
The school parking lot generates runoff that flows onto Spring Street at the west end of
this system. Some runoff from the Catholic Church parking lot on Clough Lane may
add to the runoff volume.
Table 2: Main Street System Discharging at the Steamship Authority Pier
Length of street in Length of street
System Street
Width of Street and
collection system
contributing to
Sidewalk(s)
collection system
Main
Main
William
William
Franklin
Franklin
Spring
Spring
Center
Center
Pine
Look
Look
Clough
Church
Colonial
Woodlawn
Union
Water
Drummer
Greenwood
N. William
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
32
32
24
24
39
34
27
29
25
25
28
27
27
33
30
13
29
32
60
9
27
24
1560
730
280
1170
440
1100
440
1540
1300
325
290
330
260
175
780
700
570
540
650
7065
229075
340
440
390
6115
190165
Causeway Road Discharge: The Causeway Road system collects water from three
separate basins and releases it into the head of the extensive lowlands and wetlands
associated with Mud Creek. One drainage basin includes Mt. Aldworth Street and part
of Delano Road. The second includes approximately 50 percent of the runoff collected
by the Edgartown Road-State Road system west of Causeway Road. Half of the flow
from this system is diverted into the Causeway Road system by a partially blocked pipe.
The third system is Causeway Road itself. All three areas are moderate density
residential.
The volume of runoff generated is sufficient to carry sand, silt and other debris that has
accumulated at the outlet in the upland area before the wetlands. This discharge was not
sampled during the course of this study. This discharge location has some advantages in
that filtration, absorption and infiltration of sediment, nutrients and bacteria can occur
before it reaches Mud Creek. One option for improvement may be the design and
installation of a sediment collection system to trap solids for removal and minimize their
movement, over time into the wetlands.
CPR Final Report
5
Table 3: Causeway Road Stormwater System
System Street
Width of Street and
Sidewalk(s)
Causeway
Causeway
Delano Road
Mt Aldworth
Edgartown-VH Road
(1/2)
Edgartown-VH Road
(1/2)
Cook Road
State Road (1/2)
State Road (1/2)
Look (1/2)
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
27
27
19
25
42
Length of street in Length of street
collection system contributing to
collection system
485
244
570
895
1000
42
19
32
32
27
240
180
650
1310
44495
1950
440
1874
84043
State Road Discharge at Beach Street Extension: This discharge is a direct outfall
into Tisbury Harbor. The remainder of State Road and Edgartown Road runoff that
bypasses the Causeway Road cutoff gathers runoff from Camp Street and William Street
and carries it to a 36-inch bypass pipe that begins at the Fire Station and enters the
Harbor at the end of Beach Street Extension. While not originating from the same
source, Beach Street Extension also includes three other stormwater discharges as
described under the section “Five Corners Discharge”. The watershed includes
moderate to high-density residential development. Analyses of runoff at this discharge
are reported in Table 21 as TIS2. This sample would reflect water quality impacts of
both this system as well as the Five Corners system as the pipes are immediately
adjacent to each other.
Table 4: State Road-Edgartown Road Stormwater System
System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Edgartown-VH Road
(1/2)
Edgartown-VH Road
(1/2)
Cook Road
State Road (1/2)
State Road (1/2)
State Road
Camp Street
William
Look (1/2)
Look
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
42
1100
42
240
19
32
32
32
17
24
27
27
180
650
1950
450
1275
45800
325
1510
440
400
3250
96815
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The outlet area has very low elevation that does not allow installation of infiltration
systems. Any effort to reduce the volume and impact from this system should focus on
the upper portions of the collection system.
Five Corners Discharge at Beach Street Extension: This discharge is a direct outfall
into Tisbury Harbor. Runoff from the beginning of Main Street, Beach Street, part of
Beach Road and, under the right conditions, part of Water Street enters the basins at the
intersection of Beach Street, Water Street and Beach Road known as Five Corners.
There is an 18-inch concrete pipe that carries the runoff collected by the catch basins on
the north side of this major intersection. There is also a 24-inch diameter pipe that
serves the catch basins on the south side of the Five Corners intersection as well as the
drains on Beach Road that flow into the intersection. Finally, there is a 12-inch diameter
backup pipe. Water Street has two level 12 inch pipes that normally outfall with the
Main Street system. However, with sufficient runoff, the system will back up to
contribute to the Five Corners system. As these pipes are adjacent to the discharge from
the State Road discharge, sample TIS2 was a mixture of these runoff sources.
Table 5: Five Corners Stormwater System
System Street
Width of Street and
Sidewalk(s)
Beach Street
Beach Road
Beach Road
Main Street
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
41
42
42
49
Length of street in Length of street
collection system contributing to
collection system
650
470
470
19740
215
240
1105
47440
Skiff Avenue Discharge:
Stormwater from Skiff Avenue and side streets and a
portion of Causeway Road flows down into a limestone contactor/detention basin and
then outlets across 30 to 40 feet of heavy Phragmites reeds into Mud Creek. The entry
point of the contactor bed was mapped with GPS and can be found in Figure 1. The
watershed is moderate density residential. Analyses from samples collected after the
detention basin are reported in Table 21 as TIS4 and 5.
Table 6: Skiff Avenue Stormwater System
System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Skiff Avenue
Skiff Avenue
Causeway Road
Causeway Road
Renear Street
Mt. Aldworth
Hinckley Circle
Davis
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
34
34
22
22
21
20
19
25
1250
430
450
1700
52400
520
340
200
195
320
2005
48905
CPR Final Report
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Beach Road Discharge to Lagoon Pond: Along Beach Road there is one system that
discharges into the Harbor and a second that discharges into the West Arm of the
Lagoon. Both systems are discharges from a State roadway. Available plans for the
entire road are not clear and as-built plans could not be obtained. This discharge is a
direct outflow into Lagoon Pond. The runoff generated by the intervening stretch of
Beach Road between these two systems flows into one or the other but the slope is so
gentle it is uncertain. The system draining into the Lagoon discharges between the
Piers belonging to Ralph Packer and MV Shipyard. The watershed is commercial and
industrial at moderate density.
Table 7: Beach Road System Discharging into the Lagoon
System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Beach Road
Beach Road
Beach Road
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
42
42
650
650
27300
700
700
29400
Beach Road Discharge into Tisbury Harbor: This discharge is a direct outfall into
Tisbury Harbor from a State roadway. The system draining into the Harbor discharges
behind the Mobil Station across from Tisbury Marketplace. The watershed is moderate
density commercial/industrial. Analyses of runoff from this watershed are reported in
Table 21 as TIS3.
System
Table 8: Beach Road System Discharging into the Harbor
Length of street
Street Width of Street and
Length of street in
contributing to
Sidewalk(s)
collection system
collection system
Beach Beach Road
Road
42
Beach Road
42
TOTAL LENGTH
(feet)
TOTAL AREA
(square feet)
210
210
500
500
8820
21000
In addition, there are numerous discharges along the length of Beach Road proceeding
out of Town to the drawbridge. The rectangular drains along the base of the seawall all
appear to discharge directly into the outer Harbor and are mapped as outfalls in Figure 1.
Several basins on the bridge discharge directly into the Lagoon or into the channel on
the Lagoon side of the bridge with no sediment retention capacity. Two sets of catch
basins discharge into the Lagoon by two 12-inch pipes as shown in Figure 1.
Grove Street Discharge to Outer Tisbury Harbor: This discharge carries runoff from
four residential streets across a limited stretch of beach into the water. During the
course of study, we identified the Grove Street runoff discharge as being readily
corrected and having adequate elevation to allow the installation of a first-flush leaching
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8
system above groundwater. The drainage area currently includes Grove Street and a
portion of Upper Main Street as well as Oak and Pine Streets. Runoff from Oak and
Pine Streets plus a portion of Upper Main flows into 5 catch basins (two on Oak Tree
and three on Pine Tree Lane with no leaching capacity) and then to a single, inadequate
infiltration basin on Harbor View Lane. Currently under moderate to heavy rainfall, the
leaching system is overloaded, backs up onto Harbor View Lane and runs down to add
to the Grove Street runoff. Volume is sufficient to cut a 12 to 18 inch gully across the
beach to the high tide line where recent wave activity had filled it. The contributing
areas total over 73000 square feet. The outflow affects Vineyard Haven outer Harbor.
System
Table 9: Grove Street Discharging into the Outer Harbor
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Grove Street
Oak Street
Pine Street
Harbor View
Upper Main Street
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
19
22
20
20
29
800
640
600
680
640
3360
73440
CPR Final Report
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Stormwater Collection System- Town of Oak Bluffs
Systems Not Mapped:
The South Circuit Avenue system that formerly
discharged into Farm Pond has been corrected by installation of an infiltration system in
Viera Park. The volume of water has been greatly reduced (after a 1.5 inch rainfall, only
a trickle of flow was produced-see Appendix A for a report). In addition, three streets
that either discharged into Lagoon Pond by a pipe or by direct surface flow across a
short stretch of beach are in process of being corrected with funding from the Section
319 program. These streets include: Vineyard Avenue Extension, Lagoon Road and
Hudson Avenue.
Mapping:
Stormwater systems in the Town of Oak Bluffs that were mapped are
shown in Figures 3 and 4 and include the following:
1.
Temahigan-Eastville-Beach Road system discharging into the waters of
Vineyard Sound (Figure 3- East Chop/Beach Road)
2.
New York Avenue West discharging into the waters of Vineyard Sound (Figure
3- East Chop/New York Ave.)
3.
New York Avenue East discharging into Oak Bluffs Harbor (Fig.3 Harbor/NY Ave/)
4.
Circuit Avenue North-Kennebec discharging to Oak Bluffs Harbor (Fig.3Harbor/Circuit 1)
5.
Circuit Avenue South- Kennebec discharging to Oak Bluffs Harbor (Fig.3
Harbor/Circuit 2)
6.
Sea View Avenue Extension discharging into Nantucket Sound at the Steamship
Authority pier.
7.
Sea View Avenue at Ocean Park discharging into Nantucket Sound.
8.
Sea View Avenue-Pequot Avenue discharging across jetty beach into Nantucket
Sound. (Figure 3- Jetty Beach/Sea View Ave.)
9.
Sea View Avenue-Tuckernuck Avenue discharging across Inkwell Beach into
Nantucket Sound.
10.
Vineyard Avenue West-County Avenue that discharges into wetlands associated
with Brush Pond (Figure 3- County Road/Brush Pond).
11.
Vineyard Avenue East that discharges into the wetlands south of Sunset Lake.
(Figure 3- Vineyard Ave. East).
In addition, there are five discharges into Nantucket Sound at regular intervals along the
sea wall on Sea View Avenue near Farm Pond. There are two discharges into Lagoon
Pond on the approach to the drawbridge on Beach Road. There are two pairs of grates
on the Bridge itself with no settling basin. In the North Bluff area, there are a number
of catch basins along Circuit Avenue Extension that we believe discharge to the Harbor.
There are two catch basins on East Chop Drive towards the north corner of the Harbor
that we are reasonably sure discharge through the retaining wall along the Harbor but no
pipe was found.
There are a number of distributed leaching basins in the area south and southwest of
Ocean Park. These are shown as mapped with a triangle symbol in Figure 3. We are
reasonably secure in saying that they are leaching basins and not tied into either the
Circuit Avenue stormwater system to the west or the systems along Sea View Avenue to
the east discharging to Nantucket Sound.
CPR Final Report
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We believe that the line carrying the storm water from the south end of Circuit Avenue
out to the Harbor runs as shown in Figure 3 down an alley next to Pomodoro Restaurant
and up Fisk Avenue but its exact path is not known. While the exact path is not known,
it discharges at Circuit 2 in the Harbor (see Figure 3).
The soil type is not mapped in the urban areas but nearby in all directions it is Carver
loamy coarse sand that is a drouthy soil with significant capacity to infiltrate runoff.
Slopes vary widely from 3 to 8 percent but steepening to 15 percent in some basins. The
intensity of development in systems 4 through 9 above is sufficient to generate
substantial runoff from roof and driveway surfaces to add to the flow.
Temahigan Stormwater System: This system drains into a direct outfall into outer
Tisbury Harbor. The system is a Mass Highways collection system. The contributing
basin area beyond the road itself is a moderate to low-density residential area. During
the mapping, the 12 inch steel outlet pipe was filled with beach sand. In Figure 3 it is
labeled East Chop-Beach Road.
System
Table 10: Temahigan -Eastville-Beach Road Stormwater System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to collection
system
Temahigan
Temahigan
Lyme
Elliot
Eastville
Eastville
Beach Road
Hospital Drive
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
28
28
18
18
26
26
29
22
880
95
120
70
475
140
950
2305
36990
530
425
21160
New York Avenue-West Stormwater System:
This system is a Mass Highways
stormwater system that outfalls through a 20-inch steel pipe directly into the coastal
waters off East Chop. The drainage area consists of moderate density residential. East
Chop Drive drops sharply to an elevation of less than 10 feet before it flattens out to the
beach where the discharge occurs. An infiltration project to reduce the amount of the
direct discharge would be best placed on the higher ground near to the junction of East
Chop and New York Avenue. This discharge was sampled and is reported in Table 21
as OB3). In Figure 3, it is labeled East Chop-New York Avenue.
CPR Final Report
System
11
Table 11: New York Avenue-West Stormwater System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
New York Avenue
East Chop Drive
Winemack
Nahomon
Pontiac
Cannahoot
Munroe
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
27
26
20
20
20
20
25
2700
330
3030
81480
120
240
330
430
240
1360
28400
New York Avenue-East:
New York Avenue slopes strongly downhill toward Oak
Bluffs Harbor. Several small roads drain moderate to high-density residential
neighborhoods to discharge on New York Avenue as surface flow. This system is a
Mass Highway system that drains into the southwest corner of Oak Bluffs Harbor by a
16-inch pipe and is labeled Harbor-New York Avenue in Figure 3. The contributing
watershed is moderate density residential on average. The end of the road nearest to the
Harbor is low lying limiting any attempt to reduce direct discharge through infiltration at
the downhill end. A preliminary proposal prepared by the Natural Resource
Conservation Service to divert this runoff into Lakeside Park (Town owned) to the west
of Sunset Lake seems to hold promise for a significant reduction in the discharge. This
site was sampled for both wet and dry weather runoff analyses and the data is shown in
Table 21 as OB1.
Table 12: New York Avenue-East Stormwater System
System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
New York Avenue
New York Avenue
Maple
Laurel
Cedar
Pacific-Spruce
Hampson
Chestnut complex
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
30
30
19
19
19
20
19
20
740
740
22200
998
240
570
320
780
665
830
4403
97805
Circuit Avenue North:
This system drains a high-density commercial and a small
area of high-density residential land use. The discharge enters Oak Bluffs Harbor at the
southeast corner from a 16-inch pipe labeled Circuit 1 in Figure 3. Circuit Avenue,
Kennebec, Lake and Oak Bluffs Avenue all drain toward the Harbor for at least a
portion of their length both within this system and as surface flow along the roadways.
Lake and Oak Bluffs Avenue are wide roads with diagonal parking. Several moderate
CPR Final Report
12
size public and private paved parking areas on Kennebec contribute to the volume of
runoff. The runoff discharge was sampled for both wet and dry weather analyses and
the data is shown in Table 21 as OB5. It may be possible to reduce the total volume of
runoff by infiltrating separate components on Lake near Ocean Park, Oak Bluffs Avenue
beneath the right of way near the old town hall and Ocean Avenue in the right of way or
in Ocean Park itself. Once the roads meet near the foot of Circuit Avenue there may be
insufficient elevation to address the problem.
System
Table 13: Circuit Avenue-North and Kennebec Stormwater System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Circuit Avenue
Circuit Avenue
Kennebec
Kennebec
Oak Bluffs Avenue
Oak Bluffs Avenue
Lake Avenue
Lake Avenue
New York Avenue
Ocean Avenue
Circuit Avenue Ext.
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
46
46
30
30
81
81
60
40
59
51
40
400
120
425
160
100
475
170
1095
49450
380
120
170
140
1445
85345
Circuit Avenue-South Stormwater System:
Circuit Avenue also slopes to the
south from the crest of the road near the Post Office park. The system collects runoff
from a high-density commercial area as well as high-density residential areas both to the
east and to the west of the road. The collected stormwater is carried by a pipe of
unknown size down an alley near the present location of the Pomodoro restaurant
through the Camp Grounds and out onto New York Avenue across from the Wesley
House where it discharges through a 12-inch pipe into the southern end of Oak Bluffs
Harbor at the outlet labeled Circuit 2 on Figure 3. Hiawatha Park and Niantic Park
might provide infiltration capability for a small portion of the runoff. Additional
reduction in discharge volume by infiltration could be gained only through an easement
from the private property through which the pipe passes between Circuit Avenue and the
Harbor. This location was sampled for both dry and wet weather sample analyses and
the results are shown in Table 21 as OB4.
CPR Final Report
System
13
Table 14: Circuit Avenue-South Stormwater System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Circuit Avenue
Circuit Avenue
Kennebec
Kennebec
Hiawatha
Uncas
Bradley
Penacook
Pequot-Massasoit
Narragansett
Bayliss
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
35
20
28
26
16
20
11
18
19
31
16
1000
550
120
1120
38360
330
330
450
640
520
475
170
200
3665
60715
Sea View Avenue-Jetty Beach Stormwater System:
The high-density residential
area south of Ocean Park slopes toward the east along Samoset, Narragansett and Pequot
Avenues where it enters Sea View Avenue and flows into two sets of storm drains.
These drains also collect a large amount of runoff from Sea View Avenue itself and
discharge through a 12-inch concrete pipe onto the beach known as Jetty Beach (Figure
3 Jetty Beach-Sea View Avenue). This discharge is substantial enough to create a gully
that extends across a considerable portion of the beach. The eventual discharge into
Nantucket Sound poses little water quality threat due to the dilution available. However,
this discharge does pose some threat to the health of beach goers during and shortly after
a runoff event. Fecal coliform levels were high in the runoff here. It may be possible to
divert this runoff to Waban Park (Town owned) for infiltration if there is adequate
elevation. This discharge was sampled for wet weather runoff analyses and is shown as
sample OB6 in Table 21.
Table 15: Sea View Avenue-Jetty Beach Stormwater System
System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Sea View Avenue
Sea View Avenue
Ocean Avenue
Samoset
Narragansett
Pequot
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
48
48
40
18
24
20
300
240
190
285
350
300
300
14400
1365
38650
Sea View Avenue at Waban Park Stormwater System: The middle of Waban Park
is a low area that extends toward the south and drains toward Farm Pond after passing
CPR Final Report
14
through a wetland area. Sea View Avenue also reaches a low point at the east edge of
the park where Tuckernuck and Sea View intersect. The surface runoff from the highdensity residential area to the north of Waban Park runs down toward the Park and a
portion is carried into this stormwater system. Runoff from Sea View Avenue both from
the north and south also flows to this low point where it is carried through the sea wall in
a 12-inch concrete pipe to discharge across the beach known as the Inkwell Beach. It
may be possible to combine the runoff from this segment with that from the previous
segment to infiltrate the first flush into Waban Park.
Table 16: Sea View Avenue at Waban Park Stormwater System
System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Sea View Avenue
Sea View Avenue
Penacook
Tuckernuck
Waban
Pequot
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
48
48
18
20
18
18
120
120
5760
570
400
400
240
120
1730
49040
Sea View Avenue Steamship Authority Stormwater System: The discharge location
at the Steamship Authority could not be found but is believed to be beneath the pier.
Runoff draining into two catch basins at the intersection of Sea View Avenue and Oak
Bluffs Avenue is carried across Sea View to a catch basin in front of the SSA Office and
into the discharge system. The outlet pipe is on the armored shore protection where it
flows down to and enters Nantucket Sound. The impact of this discharge on water
quality should be minimal due to the small drainage area and the large dilution available.
Table 17: Sea View Avenue Steamship Authority Stormwater System
System
Street
Width of Street & Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Sea View Avenue
Sea View Avenue Ext
Oak Bluffs Avenue
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
48
51
80
240
240
11520
240
120
360
21840
Sea View Avenue at Ocean Park Stormwater System: The swale in Sea View
Avenue at about the midpoint of Ocean Park contains two drains that are connected and
discharge from a 12-inch steel pipe onto the rock armament on the shore where the
runoff enters Nantucket Sound. As in the case of the previous system and for the same
reasons, the impact of this discharge on water quality is probably minimal.
CPR Final Report
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15
Table 18: Sea View Avenue at Ocean Park Stormwater System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Sea View Avenue
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
59
0
740
740
43660
Vineyard Avenue-County Road Stormwater System:
The stormwater from
Vineyard Avenue west of the crest in the hill near the Catholic Cemetery runs down to
the County Road system that carries the stormwater toward the intersection with
Eastville Avenue. Runoff from Eastville Avenue in both directions from the County
Avenue intersection flows down to two catch basins at this intersection and also enters
the system. Several roadside runoff chutes along the north side of Eastville Avenue will
somewhat reduce the flow from this road. The intersection area is low and may not
have sufficient elevation to correct this discharge by infiltration.
The exact location of the discharge(s) is not known but we believe the outfall is in the
wetlands at the head of Brush Pond very near County Road as shown in Figure 3 and
labeled County Road-Brush Pond. A mound-shaped feature that extends out from the
roadside some 30 feet into the wetland marks the probable discharge location. Around
the end of this feature a substantial amount of silt and fine sand was noted indicating the
likelihood of a substantial discharge here. A drainage trench in the marsh approaches
close to the discharge area such that treatment within the wetland itself may be limited.
At one location on the mound a 12-inch diameter hole opened down into standing water
implying it may be a large corrugated pipe or concrete structure in decay.
Table 19: Vineyard Avenue-County Road Stormwater System
System
Street
Width of Street and Length of street in Length of street
Sidewalk(s)
collection system contributing to
collection system
Vineyard Avenue
Vineyard Avenue
Dreamers Way
County Road
County Road
Eastville Ave.
James Place (dirt)
Leslie’s Lane
Stanley Street
Robert’s Way
Prospect Avenue (dirt)
Buena Vista Street (dirt)
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
24
24
20
32
32
21
950
140
100
2375
16
16
16
2490
98800
240
1660
475
550
190
520
330
330
3015
68060
Vineyard Avenue East Stormwater System:
The Vineyard Avenue East system
collects runoff from a number of residential streets that drain down to it. Land use
CPR Final Report
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density is moderate to high. The collected runoff is carried down to discharge in the
wetland (on Assessor’s Map 11 Lot 351) that is south of and drains into Sunset Lake.
The exact location of the discharge could not be determined and the discharge shown in
Figure 3 should be considered approximate. Travel through the large wetland (as much
as 8 acres) will probably remove solids and provide some opportunity for significant
uptake of nitrogen and phosphorus.
Table 20: Vineyard Avenue East Stormwater System
System Street
Width of Street Length of street in
and Sidewalk(s) collection system
Vineyard Avenue
Vineyard Avenue
Winthrop
Shawmut
Franklin Avenue
Potato Farm
Norris
Marvin (dirt)*
Pierce (dirt)*
Pacific
Perkins
28
28
18
26
20
18
20
12
13
20
19
TOTAL LENGTH (feet)
TOTAL AREA (square feet)
Length of street
contributing to
collection system
1450
1450
40600
590
470
780
140
170
140
70
120
120
190
2600
50598
*Dirt roads not included in area calculation
Other Probable Discharges into Oak Bluffs Harbor (eastern shore): In addition to
the sites listed, surface runoff flows down Pasque and Saco to Circuit Avenue Extension
and a large paved parking, passenger staging and auto rental area. This flow discharges
through catch basins and a number of discharge pipes through the sheet piling that forms
the eastern shore of the Harbor. The probable discharge points mapped with GPS in
Figure 3 from south to north along the eastern shore are as follows:
 At Nancy’s Snack Bar (map 8 lot 284.1)
16-inch diameter
 Under the pier near Nancy’s (map 8 lot 284.1) 16-inch diameter (reportedly closed)
 Through bulkhead (map 8 lot 285)
16-inch diameter
 Under the McCarthy pier (map 8 lot 296.1)
16-inch diameter
We believe that the discharge pipe at the McCarthy pier collects runoff from the three
catch basins on Circuit Avenue Extension that are at the foot of North Bluff Avenue and
possibly the two catch basins at the foot of Saco Avenue. However, it appears more
likely that the Saco runoff flows into those catch basins and out the outlet pipe through
the bulkhead on map 8 lot 285. In addition, there are three outlets through the cap on the
bulkhead to the north near the Island Queen dock area. These provide an exit for the
runoff that comes down Sea View Avenue Extension and from the large paved parking
area for pick-up/drop-off of commercial ferry passengers.
CPR Final Report
17
Stormwater System Runoff Sampling and analyses:
Data collected during the course of this study are reported in Table 21.
Five runoff discharge sites in each Town were identified for water testing based on the
estimated size of the contributory area and the nature of the water body that received the
discharge. The purpose of the sampling was to characterize the water quality impact
associated with these stormwater discharges, to draw insights about other discharges not
sampled and as an input to prioritize systems for correction. Samples were collected
during dry weather near where the system discharged directly into a water body to
establish background levels of the parameters to be measured. Samples were also
collected during rainfall events where sufficient precipitation had fallen to generate
runoff. Samples were collected and handled according to the Sampling and Analysis
Plan prepared and approved by DEP for a 604(b) funded water quality study carried out
in 9 coastal salt ponds during July and August 2003. The Coastal Systems Group of the
School for Marine Science and Technology at University of Massachusetts in New
Bedford (SMAST) performed all analyses reported. The Dukes County Laboratory
performed fecal coliform bacterial analyses.
When collected by hand, stormwater samples were collected by plunging a 1-liter HDPE
bottle in to a depth of approximately 6 inches below the surface. Where samples could
not be collected by hand a dipstick with a rubber stopper was used to get the bottle
below the surface at the sample site before pulling the stopper and filling the bottle. The
initial water collected was shaken vigorously and dumped to flush the bottle and then the
actual sample was collected.
Samples were processed either immediately after collection or upon return to the office
but in no case more than 1 hour after collection. Samples were filtered through a 0.22micron cellulose-acetate filter into a lab-clean, 60-milliliter, labeled bottle for dissolved
nutrient analyses including nitrate, nitrite, ammonium, orthophosphate and dissolved
organic nitrogen. Unfiltered samples were poured into similar lab-cleaned, 60 ml bottles
for total phosphorus analyses. Known volumes of sample were run through glass fiber
filters for particulate carbon and particulate nitrogen analyses. Samples were kept on ice
during processing and while shipped via Steamship Authority or by Cape Air to be
picked up by lab personnel. Approximately 0.5 liter of the sample was returned to the
SMAST lab where known volumes of the samples were filtered onto pre-weighed glass
fiber filters for total suspended solids analyses.
In the field, data was collected with a calibrated YSI85 meter to gather information on
temperature, specific conductivity and dissolved oxygen.
The first, dry-weather sample round was collected on 8 May at 5 stations in Tisbury and
5 in Oak Bluffs. These samples were sent to the Wampanoag Tribe laboratory as we
hoped they could run the required analyses. Those analyses we knew that lab could not
run (TSS, total phosphorus and particulates) were sent to the SMAST lab.
Unfortunately, there were unforeseen interferences with the dissolved nutrient analyses
run by the local lab so that the data was not reliable. The wind during sample collection
CPR Final Report
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was blowing 20 to 25 mph out of the north causing 1.5 to 2 foot waves at sites TIS1,
TIS2 and TIS 3.
Following the dry-weather date, we entered a prolonged time period where precipitation
did not occur during the early part of the workweek to allow collection and lab analyses.
The next date sampled was a wet-weather event in early August when samples were
collected only in Tisbury because the event was a short-duration, heavy rainfall and we
did not have sufficient personnel available to collect samples simultaneously in Oak
Bluffs and Tisbury. Over 0.5 inches fell before sample collection and the rain event had
ceased by the time the Tisbury samples were collected. These samples were sent to the
SMAST lab for analyses.
The third sample event was a dry-weather sampling that occurred on October 14. These
samples were collected from 5 identified sites in Oak Bluffs.
The last sample round was a wet-weather sample round on 27 October for 6 sites in Oak
Bluffs. These samples were also sent to the SMAST lab for analyses. This precipitation
event delivered steady rainfall for a period of hours. We estimate that over 0.5 inches
had fallen by the time the samples were collected between 3 and 4 p.m. A total of 0.69
inches had fallen in West Tisbury by 4:30 p.m.
Tisbury Stormwater Site Sample Results:
During the early May sampling round, the following stations were sampled:
 TIS1 Owen Little Way discharge location
 TIS2 Beach Street Extension discharge location in the Harbor
 TIS3 Beach Road discharge location into Harbor
 TIS4 Beach Road discharge location into Lagoon Pond
 TIS5 Skiff Ave. discharge location at Mud Creek
During sample collection we noted that the surf stirred up by steady winds had
suspended a considerable amount of bottom sediment and debris that caused a notable
cloudiness and a swirl of visible particles in the water. We believe that the Total
Suspended Solids (TSS) results on 8 May are higher at these stations than during the wet
weather events on 5 August due to resuspension of bottom materials. Dissolved oxygen
values ranged from 92 to 100 percent saturation. Specific conductivity values varied
from a high of 44 milli-Siemens (mS) at TIS 1 and TIS3 to a low of 27.6 mS at TIS 5.
The tide during collection was early in the flood stage.
Samples collected during the 5 August runoff event include the following locations:
 TIS1, TIS2, TIS3 and TIS 5 as above.
 TIS4 Skiff Ave discharge after passing limestone contactors but before Mud
Creek.
During the runoff event on 5 August, the TSS values are comparatively low at all sites
except for the Beach Road (Harbor TIS3) discharge where field notes indicate that the
pipe discharge was discolored. At stations TIS1, TIS2 and TIS3 discharge volume was
CPR Final Report
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sufficient to cause a rolling motion in the receiving water. Discoloration was also noted
at TIS1 but the TSS values are low. Dissolved oxygen saturation ranged from a low of
55% at TIS4 to a high over 100% at TIS1 and TIS5. Specific conductivity values were
much the same at TIS1 as they were during the dry-weather round. However, at TIS2,
TIS 3 and TIS5 the water was significantly fresher. The discharge at TIS2 varied from 1
to 4 milli-Siemens. At TIS4, the runoff was essentially fresh with a specific
conductivity value of 72 micro-Siemens. The tide during collection was mid-flood
stage.
There were marked increases in Total Dissolved Nitrogen concentrations at TIS1, TIS4
and TIS5 during the rainfall event comprised mainly of dissolved organic nitrogen and,
in the case of the latter two, also nitrate and nitrite. Total Phosphorus concentrations
also increased dramatically at all sites from less than 1 micro-mole (uM) during the dryweather sample to 3 or more uM during the wet-weather sample round.
Particulate nitrogen and carbon values were elevated reflecting the discharge of fine
suspended organic matter with the runoff. The Beach Road discharge into the Harbor
had the highest values for both of these parameters.
Oak Bluffs Stormwater Site Sample Results:
A round of dry-weather samples were collected on 14 October as follows:
 OB1 New York Ave. East discharge location into Harbor
 OB2 Harbor boat ramp
 OB3 New York Ave. west discharge location at East Chop
 OB4 Circuit Ave. South discharge location into Harbor
 OB5 Circuit Ave. North discharge location into Harbor
The tide during collection was high. During this round, TSS values were higher when
compared to the concentrations found in May. Total phosphorus values were similar to
May but generally somewhat lower.
During the wet weather event on 27 October, the discharge at the Jetty Bathing Beach
was added as OB6. All other stations are the same (same numbers) as the dry-weather
round listed above. TSS values increased by a factor of 2 to 4 times at all stations except
the discharge at the boat ramp. This probably reflects the relatively small volume of
runoff generated at this location. At OB1 and OB5, TSS values were 150 and 104
milligrams per liter respectively. The tide during the collection was midway to low tide.
Total phosphorus concentrations were also increased dramatically at all sites except
OB2 by a factor 4 to 10 times the dry-weather results. Total dissolved nitrogen values
essentially doubled. Particulate carbon concentration increased tremendously by as
much as 40 times at OB1 and OB5 reflecting the discharge of fine organic matter and
silt. Particulate nitrogen increased 8 to 12 times at stations OB1, 4 and 5 and by
nearly18 times at OB3. OB2, the boat ramp was elevated by only a factor of about 2.
CPR Final Report
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Lab Accuracy:
Sample OB7 collected on 27 October is a blind duplicate sample to test the laboratory’s
accuracy. This sample is drawn from the same bottle and handled and processed in the
same manner but labeled with a different, sequential number. The Total phosphorus was
a duplicate of station OB 4 and the results of 5.7 (OB4) and 5.5 (OB7) agree very
closely. The dissolved nutrient results were a duplicate of sample site OB3 and show
agreement to within less than about 10 percent.
Some Interpretations of the Data:
By knowing the approximate area of the contributory watershed of each discharge, an
approximation of the nutrient loading from a 0.5-inch rainfall can be calculated from the
nutrient concentrations measured in the rain event. Except for TIS4, the samples were
all collected from the receiving water. Specific conductivity values measured during the
Tisbury rain event of 5 August indicate that the TIS2 sample was nearly fresh, implying
it is near full-strength runoff. Conductivity values from TIS 1, TIS 3 and TIS5 imply
approximately 1/3 to ½ dilution with coastal water. In these samples, this means that the
concentration of the nutrients reported is significantly less than the actual stormwater
concentration due to mixing with the coastal water. Although field equipment was not
used during the 27 October rain event in Oak Bluffs, dilution to at least the same extent
can be expected for all samples.
In Table 22, the estimated content of fine sediment (Total Suspended Solids or TSS),
total dissolved nitrogen (TDN), particulate nitrogen and total phosphorus (Tot. P) are
calculated based on their concentration as measured by the lab and the volume of runoff
from a ½ inch rainfall discharge. This data represents a glimpse of the quality of the
runoff or the mix of runoff and receiving water at one time. We expect but we do not
know that the concentration of all these parameters will decrease substantially over time
during a larger rainfall or later in the runoff cycle of a moderate rainfall. The values
may have been higher if we had sampled earlier in the runoff period.
The data indicate a significant amount of Total Suspended Solids are discharged
amounting to over 10 pounds per ½ inch volume at all sites except at TIS4 where the
limestone contactor apparently slows outflow and allows settling to occur. The
discharge in the Harbor from New York Avenue carried a substantial volume of
sediment amounting to over 40 pounds per ½ inch volume. The Circuit Avenue north
discharge (OB5) also carries a substantial amount of sediment. The total discharge to
Oak Bluffs Harbor from the three main collection systems is in excess of 90 pounds per
½ inch volume of runoff.
Filters used to create dissolved nutrient samples from the rainfall runoff samples were
turned a sooty color at all stations except TIS4 and 5 and OB2. Four filters are
photocopied along with an unused filter in the Appendix from stations in Oak Bluffs
Harbor and the East Chop discharge from New York Avenue. The discoloration
resulted from filtering 100 milli-liters of sample water (less than ½ cup) and indicates
the amount of fine matter that is discharged.
CPR Final Report
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In Tisbury, Total Dissolved Nitrogen loading exceeds 0.1 kilograms per ½ inch rainfall
volume at most stations. The exception is TIS3 at the Beach Road outfall into the
Harbor. In Oak Bluffs, all four stations shown exceed 0.1 kilogram per ½ inch rainfall
volume. The discharge of 0.1 kilogram is enough to raise the nitrogen concentration to
unacceptable levels in 200 thousand liters of receiving water. (Generally poor water
quality results from nitrogen concentrations exceeding 0.5 milligrams per liter.)
Total phosphorus includes both dissolved organic and inorganic forms but also the
content of particulate matter. All runoff samples contained less than 0.1 kilogram
Sources of nitrogen include fertilizer applied to lawns and landscaping that is mobilized
by the runoff. Accumulation of street debris is also a source of nitrogen as is the acid
rainfall itself. It is also possible that there is a cross-connection with a septic system or
where the line is in or near the groundwater by infiltration at pipe connections or
damaged sections. Sources of phosphorus include fertilizers and acid rain but are
primarily derived from street debris accumulation.
Fecal Coliform Bacteria: Runoff also carries with it the droppings of birds, other
wild animals and pets that accumulate on the streets. These cause the amount of fecal
coliform bacteria to increase. Fecal coliform concentration in shellfishing waters can be
cause for closure of the bed. On October 2, five fecal coliform samples were collected
and the lab report is included in the Appendix. The sample locations were all in Oak
Bluffs Harbor and include the outlets for the boat ramp, New York Ave. discharge into
the Harbor (“Our Market)’, Circuit Avenue north (Nancy’s) and south (slip #35) and at
Jetty Beach. Coliform concentrations were too high to count at the Jetty Beach outlet
and at the Circuit Avenue North outlet. The New York Avenue and Circuit Avenue
South discharges were measurable but still very high.
CPR Final Report
24
Conclusions and Recommendations:
The stormwater discharges identified during this project are substantial sources of
sediment, fecal coliform bacteria and, to a somewhat lesser extent when compared to
other sources, nitrogen and phosphorus. All the discharges mapped represent large
volumes of runoff with the possible exception of the discharges from Beach Road into
the Harbor and the Lagoon in Tisbury and some of the discharges in Oak Bluffs from
Sea View Avenue into Nantucket Sound. Photographs of selected oulets are attached in
the Appendix to this report.
Both Towns:
Mass Highways should examine the potential for reducing the discharge volume from all
the State roadways identified here that discharge directly into coastal waters.
Non-structural, relatively less expensive steps that can be taken to reduce the discharge
of particulate matter and phosphorus include more frequent street cleaning and catch
basin sediment removal.
The installation of first flush basins either within the road right of way or, where
available, adjacent Town-owned land will decrease the volume of runoff particularly the
most contaminated first flush that occurs with the first ½ inch of rainfall. Town-owned
land is shown in Figures 1 and 3.
These maps should be incorporated in any oil spill contingency planning to identify
those areas where spillage of hydrocarbon products on the streets could lead to direct
contamination of surface water resources.
Oak Bluffs:
The Vineyard Avenue-County Road system in Oak Bluffs is a good candidate for flow
reduction by infiltration further up in the watershed.
The New York Avenue discharge into the Harbor could be diverted to infiltrate a first
flush in Lakeside Park. An evaluation confirming this has been done.
Drainage from the high-density residential area along Sea View Avenue near Jetty
Beach will have a preliminary engineering design to evaluate the potential for
infiltrating the first flush into Waban Park.
A portion of the flow from Oak Bluffs Avenue and Lake Avenue that contributes to the
discharge from the Circuit Avenue North system may also be infiltrated either beneath
the road layout or in Ocean Park.
The exact location of the Vineyard Avenue East discharge should be identified to assure
that there is adequate wetland treatment of this source before it enters Sunset Lake. If
the discharge is into surface waters that will offer little treatment, this site may offer an
opportunity for a created artificial wetland or sediment settling detention system to pretreat the discharge.
CPR Final Report
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The location of the Vineyard Avenue-County Road discharge into the wetlands around
Brush Pond should be confirmed by observation during a runoff event to assure that the
discharge flows through enough wetland to reduce sediment and nutrient loads. If not,
this site may offer an opportunity for a created wetland or sediment settling system to
improve water quality.
Stormwater pipe sizes in the Town are largely unknown. Obtaining pipe size
information from old records or from former Highway Department personnel should be
a priority activity.
Tisbury:
In Tisbury, we identified the Grove Street runoff problem as one that could be largely
corrected by infiltration through a system of first flush basins beneath the road layout.
This will be the focus of a preliminary engineering design.
In addition, the DPW is already planning to reduce the flow to the Main Street system
from the grammar school parking lot by installing a first flush basin along Spring Street.
It is recommended that Mass Highways look into reducing the stormwater flow from the
State Road segment. This may be possible through placement of first flush basins in the
road layout.
The Causeway Road discharge may have some negative impact on the wetlands at the
head of Mud Creek. An evaluation of this potential was beyond the scope of this study
and is not clear at this time. If found to be the case, placement of a limestone
contactor/detention bed as is used with the Skiff Avenue discharge may improve water
quality and reduce the amount of sediment discharge. The flow here is considerably
greater than at Skiff Avenue and some means of settling the sediment before entry into
the limestone contactors may be necessary.
Placement of first flush systems along the Franklin-William Streets area could offer
substantial reduction in flow to the Main Street system. Reduction of flow on William
Street will reduce the quantity of runoff going down Camp Street and entering the Beach
Street Extension discharge.
In general, it is recommended that potential discharge reduction by infiltration be
evaluated for inland segments of both the Main Street and Beach Street Extension
systems.
Mass Highways should examine the Beach Road discharge into Lagoon Pond for
alternatives to reduce release of fecal coliform bacteria due to the value of the West Arm
of the Lagoon as a shellfish resource and the limited tidal circulation available.
CPR Final Report
26
Prioritizing systems for preliminary engineering design:
Stormwater discharges that could potentially affect human health are a top priority for
correction. These discharges include those that outfall to recreational waters used for
swimming and into shellfish producing waters. All samples collected contained
excessive numbers of fecal coliform bacteria that can cause health problems and lead to
closure of shellfish beds (see page 21 for discussion).
Outflows into coastal waters used for swimming in Oak Bluffs include Jetty Beach,
Inkwell Beach, New York Avenue (East Chop), Beach Road and, to a lesser extent, the
other discharges along Sea View Avenue. In Tisbury, these discharges are Main Street,
Owen Little Way, Grove Street and along Beach Road.
Discharges into shellfish producing waters include all discharges into Oak Bluffs Harbor
and the Vineyard Avenue West discharge into Brush Pond that is tidally connected to
Lagoon Pond. In Tisbury, these discharges include the Beach Road discharge into the
West Arm of the Lagoon and, indirectly, the discharge from Skiff Avenue into Mud
Creek that is tidally connected to the West Arm.
Once systems that may impact human health were identified, the next level of evaluation
we conducted rested on water quality impacts and feasibility. While not all discharges
were analyzed, among those tested, some stand out for higher levels of contaminants
(see Table 22):
For sediment loading: Beach Road discharge to Tisbury Harbor
New York Avenue discharge to Oak Bluffs Harbor
Circuit Avenue North discharge to Oak Bluffs Harbor
For nitrogen loading: Owen Little Way to outer Tisbury Harbor
Skiff Avenue discharge to Mud Creek
New York Avenue discharge to Oak Bluffs Harbor
Circuit Avenue North discharge to Oak Bluffs Harbor
For phosphorus loading: Owen Little Way to outer Tisbury Harbor
Skiff Avenue discharge to Mud Creek
New York Avenue discharge to Oak Bluffs Harbor
Circuit Avenue North discharge to Oak Bluffs Harbor
Many of these stormwater systems were shifted to lower priority because they have
already been partially upgraded (Owen Little Way and Skiff Avenue) or because
preliminary plans for addressing them are available (New York Avenue discharge to
Oak Bluffs Harbor). Others pose difficult engineering problems because the lower
segment of the stormwater system is at such low elevations that there is insufficient
depth for infiltration to be added and remain above the water table (grade at less than
about 5 feet MHW). These include both Circuit Avenue discharges, Vineyard Avenue
West and Beach Road in Oak Bluffs. The Beach Road, Main Street and Beach Street
Extension systems in Tisbury are also constrained by low elevation near the outfall and
for a considerable distance up gradient from it. Opportunities to reduce these discharges
by infiltrating portions of the contributing flow further up in the watershed should be
pursued.
CPR Final Report
27
After considering the possible impacts to human health and the potential to correct the entire
discharge rather than addressing a small segment further up in the watershed, we chose the
Grove Street discharge in Tisbury and the Jetty Beach and Inkwell Beach discharges in Oak
Bluffs. The Oak Bluffs sites are discharges to recreational beaches that we believe have
sufficient elevation for a suitable engineering design and in which the Department heads in the
two Towns were interested. If the Jetty Beach outflow can be corrected, it will have the added
advantage of allowing the Town to nourish this beach with dredging material from the entrance
to Oak Bluffs Harbor. The Grove Street discharge is less used beach.
Beyond these two sites, the general strategy suggested to reduce the impact of the other
discharges is to reduce total present-day flow by infiltrating portions of the runoff further up in
the watershed. This can be accomplished either by intercepting the flow in the collection
system at a location where Town-owned land (or right of way) is available or before it enters the
collection system from those roads beyond the system that contribute surface runoff to it.
Engineering Plans:
Sourati Engineering Group conducted preliminary engineering evaluation of the two sites
identified for correction and these designs are attached to this document. The two sites are the
Sea View Avenue discharges to Jetty and Inkwell beaches in Oak Bluffs and the Grove Street
discharge in Tisbury. Both sites are believed to offer the likelihood of correction by installation
of first-flush systems to treat and infiltrate the first ½ inch of runoff.
In the case of the Sea View Avenue discharges, the Town-owned Waban Park has potential as
an infiltration site. The elevation of the Park may be low enough that some fill may be required.
In the case of Grove Street, sufficient elevation for infiltration within the road right of way
exists a short distance away from the discharge as the road is steeply sloped. There is no Townowned land in this area.