Oak Creek Village/ Butler Oak Creek Village/ Butler Farms Stormwater Study Farms Stormwater Study

GroupGroup

July 27, 2006July 27, 2006

Objectives tonight:Objectives tonight:

1.1. Understand “hybrid” or “whole picture” Understand “hybrid” or “whole picture” engineering approachengineering approach

2.2. Review cost, finance, pros/cons sheetsReview cost, finance, pros/cons sheets3.3. Choose date for field day to look at options on Choose date for field day to look at options on

the groundthe ground4.4. Identify points to be included in mailer to Identify points to be included in mailer to

entire neighborhood to explain options and entire neighborhood to explain options and field dayfield day

5.5. Choose date for next meeting on Choose date for next meeting on recommending an engineering option, recommending an engineering option, timeframe, financial approach, and any other timeframe, financial approach, and any other aspects to Councilaspects to Council

Recap: Recap: Two engineering options developed, with cost Two engineering options developed, with cost

estimates:estimates:

1.1. ““The Super Pond” – Treat all The Super Pond” – Treat all development runoff in a large pond at development runoff in a large pond at north end of Oak Creek Villagenorth end of Oak Creek Village

2.2. More minimal, State Rules-Based More minimal, State Rules-Based Upgrades and New Treatment in four Upgrades and New Treatment in four dispersed sitesdispersed sites

Third “hybrid” engineering option outlined by Third “hybrid” engineering option outlined by UVM and rough cost estimate completed by UVM and rough cost estimate completed by Stantech & City – presentation & comparison Stantech & City – presentation & comparison tonighttonight

City Council Discussion:City Council Discussion: Total City-wide cost likely to be $18 million to comply Total City-wide cost likely to be $18 million to comply

with TMDLs/Watershed General Permitswith TMDLs/Watershed General Permits About $9.5 million does NOT have identified funding, About $9.5 million does NOT have identified funding,

including BF/OCV (except engineering)including BF/OCV (except engineering) Roughly 3,000 residential units face expiration of Roughly 3,000 residential units face expiration of

“deferral of permit” provisions in Sept. 2007“deferral of permit” provisions in Sept. 2007 MaybeMaybe 12 neighborhoods can complete takeover before 12 neighborhoods can complete takeover before

that date – possibly including OCV/BFthat date – possibly including OCV/BF City needs to work out plan with State, EPA, legislature City needs to work out plan with State, EPA, legislature

to move forward and prevent title problemsto move forward and prevent title problems Significant decision to be made about how and when to Significant decision to be made about how and when to

socialize stormwater costs among taxpayers.socialize stormwater costs among taxpayers.

Where BF/OCV Fits:Where BF/OCV Fits:

Residential Systems with Expired Permits and No Association:

Watershed Owner

Permit Status

Existing Treatment?

Impervious Acres

CITY ROAD?

Cost based on per-acre assumptions Units

Potash Ledgeknoll Expired No 7.6 Yes $228,000 49

Potash Butler Farms/Oak Creek Expired No 43.7 Yes $1,311,000 253

Potash Brookwood Drive Expired No 5 Yes $150,000

Potash Funky houses on Dorset Expired Yes 5.6 Yes $42,000 6

Potash Davis Parkway expired Yes 5.1 Yes $38,250 30

Centennial Queensbury Road Expired No 2.35 Yes $70,500 5

Bartlett Pheasant Way Expired No 15.7 Yes $471,000

Bartlett Irish Farm Expired Yes 8.4 Yes $63,000 30

Bartlett Overlook at Spear Expired Yes 15.9 Yes $119,250 70

Financial Status:Financial Status: Current annual utility Current annual utility

appropriation for capital could appropriation for capital could support a $4 million, 20-year bond support a $4 million, 20-year bond

Some suggestions for funding Some suggestions for funding upgrades of permitted surfaces upgrades of permitted surfaces have included:have included: Utility surcharge by permitted area/neighborhoodUtility surcharge by permitted area/neighborhood Capped per-unit contribution from each unit to Capped per-unit contribution from each unit to

Utility capital fundUtility capital fund Combination of utility and general obligation Combination of utility and general obligation

bonding to cover total costbonding to cover total cost

Job for the Study Group:Job for the Study Group:

In a perfect world, which In a perfect world, which ENGINEERING OPTION is ENGINEERING OPTION is preferred?preferred?

In a perfect world, which FUNDING In a perfect world, which FUNDING OPTION is preferred?OPTION is preferred?

In an imperfect real world, what In an imperfect real world, what approach should be recommended to approach should be recommended to the owners, state, and City Council?the owners, state, and City Council?

Back to Engineering:Back to Engineering:

Hybrid Approach has been Hybrid Approach has been developed in conceptual developed in conceptual engineering and cost termsengineering and cost terms

Treats all sources and areas in a Treats all sources and areas in a “distributed” approach“distributed” approach

Deals with flooding, safety, Deals with flooding, safety, quality of life AND permit quality of life AND permit standardsstandards

Has Has very different implicationsvery different implications for use of private and public for use of private and public landland

Use of High Resolution Use of High Resolution Remote Sensing Data to Remote Sensing Data to Optimize the Placement Optimize the Placement

of Alternative of Alternative Stormwater BMPsStormwater BMPs

Data: 3m Lidar and 16cm (5-inch) MOP Data: 3m Lidar and 16cm (5-inch) MOP Orthophotos –Nat Colors, NIR.Orthophotos –Nat Colors, NIR.

VCGI data on hydrologic stream network, VCGI data on hydrologic stream network, roads, houses, Land Use, Engineered roads, houses, Land Use, Engineered catchments pipeline network and inlets points.catchments pipeline network and inlets points.

With high resolution data at the first stage of With high resolution data at the first stage of analysis. We used Lidar elevation data , with analysis. We used Lidar elevation data , with hydrologic modeling capabilities of hydrologic modeling capabilities of

Arc GIS, we’ve created DEMs, defined stream Arc GIS, we’ve created DEMs, defined stream network, delineated the watershed and network, delineated the watershed and multiple subwatersheds multiple subwatersheds

Step 1 Identify:- Areas where engineering solutions bring most relief before anything else can be applied.- Areas that have been artificially connected to our neighborhood, adding significantly to the existing problem. Redirecting water from these areas would not be interbasin transfer but rather restoration of natural water pathways- Areas suitable for mid-scale BMPs and small-scale dispersed BMPs- Time line for BMPs depending on large-scale engineering solutions and redirecting the artificial adds-on from the watershed

Stream network derived from LIDAR elevation data. How it is supposed to look.

Stream network derived from LIDAR elevation data. Some storm micro-drainage

Stream network derived from LIDAR elevation data. Detailed storm micro-drainage .

Closer look. Only the main stream

Closer look. Some storm micro-drainage

Closer look. Detailed storm micro-drainage

Subwatersheds delineatedBased on Lidar elevation data

Areas 1,2,3 - large scale engineering solutions. Most part of those areas extend way beyond the neighborhood (golf course)

Areas 4, 5, 6 – mid scale and small scale BMPs

Areas 7 and 8 – Delineation of watershedbased on Lidar data shows that according to elevationthose areas are supposed to drain to the right of Hinesburg road

Step 2Step 2 - Identify the patterns of micro storm - Identify the patterns of micro storm water drainage network and the density of water drainage network and the density of this network (MSDD – index ). this network (MSDD – index ).

Using MSDD index we are able to identify Using MSDD index we are able to identify

where the medium-sized alternative BMPs where the medium-sized alternative BMPs will do the job and where the small-scale will do the job and where the small-scale private rain gardens will be effective. private rain gardens will be effective.

The threshold for calculating this index has The threshold for calculating this index has been derived from the information about been derived from the information about DEM resolution, the average parcel size, DEM resolution, the average parcel size, average imperviousness for the area, and average imperviousness for the area, and EPA recommendation for the private rain EPA recommendation for the private rain garden size based on all above.garden size based on all above.

Micro Storm Water Drainage Pathways

Spatial representation of MSDD index - the density of micro storm water drainage network

Step 3Step 3 . Calculate the water volumes and . Calculate the water volumes and quantities for the chosen mid-range BMP quantities for the chosen mid-range BMP areas areas

To do so we have to finesse the analysis by:To do so we have to finesse the analysis by:

1 – deriving and utilizing remote sensing indices 1 – deriving and utilizing remote sensing indices in order to assess the impervious areas for in order to assess the impervious areas for selected subwatersheds. selected subwatersheds.

2 - developing the GIS model/tool to estimate 2 - developing the GIS model/tool to estimate amount of water/sediments accumulated/ amount of water/sediments accumulated/ intercepted by BMPsintercepted by BMPs

We use high resolution Quick Bird or 0.15m MPO We use high resolution Quick Bird or 0.15m MPO NIR image to calculate NDVI and NIR image to calculate NDVI and consequently calculate impervious surfacesconsequently calculate impervious surfaces

NDVI based on 15cm MPO NIR image

Very good match - Impervious surfaces calculated on the basis of Quick Bird (red line) versus NDVI on the basis of 15cm MPO NIR image

Reclassified MSDD index for clear delineation of mid-scale/small scale BMPs areas

Mid-scale BMP Watershed delineation based on Lidar data

““EFA” ApproachEFA” Approach

Area 1Area 1 MarceaMarceau u MeadowMeadowss

Do not treat or size pond for Do not treat or size pond for flow; allow to flow through Trib flow; allow to flow through Trib 7/swale as is; not needed for 7/swale as is; not needed for EFA specsEFA specs

Areas 2 Areas 2 & 3& 3

Golf Golf CourseCourse

Size pond for inflow from a new Size pond for inflow from a new swale, but swale not needed to swale, but swale not needed to meet EFA specsmeet EFA specs

Areas 4 Areas 4 & 6 (BF) & 6 (BF) and 5 and 5 (OCV)(OCV)

Central Central sectionssections

Route area 6 into east pond; Route area 6 into east pond; Resize pond & build infiltration Resize pond & build infiltration for area 5; no treatment for for area 5; no treatment for area 4area 4

Areas 7 Areas 7 & 8& 8

Eastern Eastern sectionssections

Build east pond for areas 6 & 7; Build east pond for areas 6 & 7; build infiltration for area 8build infiltration for area 8

““Super Pond” ApproachSuper Pond” Approach

Area 1Area 1 MarceaMarceau u MeadowMeadowss

Do not treat or size pond for Do not treat or size pond for flow; allow to flow through Trib flow; allow to flow through Trib 7/swale as is; not needed for 7/swale as is; not needed for specsspecs

Areas 2 Areas 2 & 3& 3

Golf Golf CourseCourse

Size pond for inflow from a new Size pond for inflow from a new swale, but swale not needed to swale, but swale not needed to meet EFA specsmeet EFA specs

Areas 4 Areas 4 & 6 (BF) & 6 (BF) and 5 and 5 (OCV)(OCV)

Central Central sectionssections

Connect into treatment system Connect into treatment system draining to ponddraining to pond

Areas 7 Areas 7 & 8& 8

Eastern Eastern sectionssections

Connect 7 into treatment Connect 7 into treatment system; no treatment for area 8system; no treatment for area 8

Whole Picture ApproachWhole Picture ApproachArea 1Area 1 Marceau Marceau

MeadowsMeadowsBuild detention pond Build detention pond to reduce flow, to reduce flow, velocity, and velocity, and sediment load in Trib sediment load in Trib 77

Areas 2 & 3Areas 2 & 3 Golf Golf CourseCourse

Build swale to re-Build swale to re-route flow into route flow into properly sized pondproperly sized pond

Areas 4 & 6 Areas 4 & 6 (BF) and 5 (BF) and 5 (OCV)(OCV)

Central Central sectionssections

Treat with multiple Treat with multiple small and mid-sized small and mid-sized retention areas and retention areas and BMPs; retro-fit Oak BMPs; retro-fit Oak Creek pondCreek pond

Areas 7 & 8Areas 7 & 8 Eastern Eastern sectionssections

Build eastern pond Build eastern pond for area 7 (smaller for area 7 (smaller than EFA version) than EFA version) and infiltration for and infiltration for area 8area 8