presentation to 19th annual nps...
TRANSCRIPT
Presentation to19th Annual NPS Conference
Funding provided by Rhode Island DEM through a USEPA section 319 grant
Narrow River Stormwater Abatement Narrow River Stormwater Abatement Jim Riordan, AICPMay 20, 2008
Jim Riordan, AICPMay 20, 2008
Narrow River Study Goals & ObjectivesNarrow River Study Goals & Objectives
GOAL: Reduce pathogens and nutrients; and return baseflow to predevelopment levels.
Assess watershed conditions.
Conduct conceptual planning study.
Select 4 subwatersheds and appropriate BMPs with Stakeholder Input.
Design BMPs to 75%.
GOAL: Reduce pathogens and nutrients; and return baseflow to predevelopment levels.
Assess watershed conditions.
Conduct conceptual planning study.
Select 4 subwatersheds and appropriate BMPs with Stakeholder Input.
Design BMPs to 75%.
Project Study AreaProject Study Area
PETTA LAKE SHORES 2PETTA LAKE SHORES 2WOODSIA TRAIL –NORTH
PETTA LAKE SHORES 3WOODSIA ROAD –SOUTH
METTATUXET 4METTATUXET 4WOODBRIDGE ROAD
CIRCUIT DRIVE 1WAMPUM ROAD
EDGEWATER 2EDGEWATER 2SOUTH FERRY ROAD
METTATUXET 3METTATUXET 3SHAGBARK ROAD
PETTA LAKE SHORES 1SHADBUSH TRAIL
PETTASQUAMSCUTT COMBINATION
PETTASQUAMSCUTT TERRACE 1 & 2
PETTAQUAMSCUTT AVENUE
METTATUXET 1METTATUXET 1OLD PINE ROAD
METTATUXET ROAD
METTATUXET 2METTATUXET BEACH
EDGEWATER 1EDGEWATER 1LAKESIDE DRIVE
INDIAN HEADINDIAN HEADINDIAN TRAIL
CIRCUIT DRIVE 2CONANICUS ROAD
Technical Memorandum Subwatersheds
Narragansett Subwatershed Names
TMDL Subwatershed Names
Hydrologic Data by SubwatershedHydrologic Data by Subwatershed
27.73.21.180.300.6050.862.37.219.5Mettatuxet 4
35.93.70.980.320.6454.865.37.620.1Mettatuxet 3
51.35.61.640.420.8554.868.610.226.8Mettatuxet 1
119.022.83.120.971.9464.774.923.289.2PettasquamscuttTerrace Combo
22.23.50.340.170.3567.575.24.213.5Edgewater 2
70.213.21.120.761.5170.278.018.147.2Edgewater 1
225.727.73.251.282.5767.077.030.8100.4Petta Lake Shores 2
52.16.51.480.420.8458.972.910.127.2Indian Head
cfsacre-ftacre-ftacre-ftacre-ftacresacres
Q25V25VGWRV1flushWQV CNnCN
AimpATotalOutfall
Key Points
• WQV = 9.3 ac/ft
• VGWR = 13.11 ac/ft
Available BMPsAvailable BMPs
•Roof leader disconnection
Impervious surface disconnection
•Vegetated strips
Engineered vegetative strips and conveyances
•Permeable Pavement
•Dry wells
••Disconnected catch basins and proprietary infiltration units
••Infiltration trenches
•••Bioretention
•••Sand filters
Filtration and infiltration
Source Reduction
UplandEnd-of-PipePractices and Strategies
Key Points
• Considered all BMPs in Table 3 (page 8).
• Analyzed only BMPs that produced quantifiable result.
Sand FilterSand Filter
Elevation
Typical Section
OPTIONAL IMPERMEABLE LINER
Plan View
Section View
BioretentionBioretention
Plan View
Elevation
Typical Section
Infiltration TrenchInfiltration Trench
Disconnected Catch BasinDisconnected Catch Basin
Dry WellsDry Wells
Permeable PavementPermeable Pavement
Vegetative StripVegetative Strip
Roof Leader DisconnectionRoof Leader Disconnection
On-Lot BMPsAssuming 20% ParticipationOn-Lot BMPsAssuming 20% Participation
68Study Area (weighted average)1
811Mettatuxet 4
910Mettatuxet 3
611Mettatuxet 1
611Pettasquamscutt Terrace 2
67Pettasquamscutt Terrace 1
77Edgewater 2
56Edgewater 1
49Petta Lake Shores 2
36Indian Head
VGWRWQV
Percent Treated (%)
Subwatershed
• Based on a recent survey conducted by the Town, actual willingness to participate is 10 – 18%.
Upland BMPsUpland BMPs
32% - 47%62% - 96%TOTAL
62%100%Mettatuxet 3
100%100%Mettatuxet 1
100%100%Pettasquamscutt Terrace 2
0% – 30%48% - 100%Pettasquamscutt Terrace 1
0%0%Edgewater 2
0% – 56%42% - 100%Edgewater 1
0% -23%29% - 100%Petta Lake Shores 2
58%100%Indian Head
VGWRWQV
Best Available Volumetric CapacitySubwatershed
End-of-Pipe BMPsEnd-of-Pipe BMPs
73%78% - 80%TOTAL
100%100%Mettatuxet 3
100%100%Mettatuxet 1
100%100%Pettasquamscutt Terrace 2
92%100%Pettasquamscutt Terrace 1
100%100%Edgewater 2
100%100%Edgewater 1
0% -9%11% - 29%Petta Lake Shores 2
97%100%Indian Head
VGWRWQV
Best Possible Level of Treatment Subwatershed
Conceptual DesignsConceptual Designs
Conceptual DesignsConceptual Designs
Conceptual DesignsConceptual Designs
Conceptual DesignsConceptual Designs
Conceptual DesignsConceptual Designs
Conceptual DesignsConceptual Designs
Conceptual DesignsConceptual Designs
Conceptual DesignsConceptual Designs
Order-of-Magnitude Opinions of CostOrder-of-Magnitude Opinions of Cost
98139$3,000,000TOTAL
913$260,000Mettatuxet 4
711$220,000Mettatuxet 3
1318$370,000Mettatuxet 1
2433$690,000Pettaquamiscutt Terrace Combo
34$80,000Edgewater 2
1216$340,000Edgewater 1
2028$710,000Petta Lake Shores 2
1116$330,000Indian Head
% GWR% WQVCOSTSUBWATERSHED
Key Points
• Cost are ESTIMATES for planning purposes only.
• Cost do not include, land, design and permitting.
• Actual costs may be 2x or greater.
Rating MatrixRating Matrix
Key Points
• Allows comparison of BMPs across subwatersheds.
• Does not rate on-lot BMPs as the decision to implement is primarily in the hands of property owners.
Rating MatrixRating Matrix
Criteria Rankings as Determined by TACCriteria Rankings as Determined by TAC
Types of BMPs Analyzed
Types of BMPs Analyzed
Rating MatrixRating Matrix
Calculated from Reference MaterialsCalculated from Reference Materials
Calculated Based on Hydrologic Data
Calculated Based on Hydrologic Data
Subjective Values—Based on BPJ
Subjective Values—Based on BPJ
Scoring RubricScoring Rubric
NA
NA
1
3
1
2
2
2
2
3
3
Assigned Weight
Fraction town-owned x 1Fraction in roadway, managed open space or stabilized x 0.5Fraction unmerged vacant land x 0.25Fraction merged vacant land x 0.13
Multiplier B – Type of Area Available
=( 0.75(Vtreatable1/WQVtotal) + 0.25(Vtreatable /VGWR-total))4 x 10Multiplier A – Treated
Volume
Project has few impediments to being implemented (permitting, engineering, other approvals)=10
Project has significant impediments to being implemented (permitting, engineering, other approvals)=0
Ability to Implement
Finished project has limited impacts to neighborhood (perceived or otherwise) = 10
Finished project has significant impacts to neighborhood (perceived or otherwise) = 10
Public Acceptance
High reliability to function during range of storm events = 10Little reliability to function during range of storm events = 0
Reliability
O&M cost/ability low = 10O&M cost/ability moderate = 5O&M cost/ability high = 0
Operation & Maintenance (O&M)
= 10 – unit cost (Table 153)Construction Cost
= 10 – VPA (Table 153)Space Requirement/Land
=VGWR1 x GWR factor
VGWR-SW2
Groundwater Recharge
= WQV x nitrogen reduction benefit factorWQVSW
2Nitrogen Reduction
= WQV1 x bacteria reduction benefit factorWQVSW
2Bacteria Load Reduction
Scoring RubricCriteria
BMP SelectionBMP Selection
Recommendations
• Scores provide a strong starting point for identifying locationsfor BMPs.
• Based on the scores (above) and additional information from the Town, we would recommend:
– Pettaquamscutt Terrace Combination (PTC).
– Edgewater 1 & 2 (E1 & 2).
75% Plans75% Plans
75% Plans—Pettaquamscutt Terrace75% Plans—Pettaquamscutt Terrace
75% Plans—Edgewater 1&275% Plans—Edgewater 1&2
Next StepsNext Steps
Grant of $1.1M from RIDEM
• Final design and permitting for Pettaquamscutt and Edgewater.
• Construction and monitoring of BMPs at Pettaquamscutt and Edgewater.
• Further design work for the other Narrow River Subbasins