Stormwater Utility Workshop

March 25, 2015

Case Studies in New England

Cost Effective Methods for Parcel Analysis

and Completing Comparisons/Evaluations

for Stormwater Utility Rate Structure Options

Presented by

Bethany Eisenberg, VHB

Josh Sky, VHB

Juli Beth Hinds, Birchline Planning LLC

Mark Wetzel, Ayer Public Works

Answering Rate & Revenue

Questions Efficiently

Goals

Remote Sensing Technology

Ayer Case Study

Protecting resources, maintaining systems, and compliance

with state and federal regulations

Developing a User-Fee-Funded Stormwater

Program (without the “u” word)

Making sure the fee/fund matches

the services provided

“Any charge system in which a customer’s bill is determined based on the

demands that the customer imposes on the system and the related

benefits and services enjoyed by the customer, with the revenues that are

raised dedicated to addressing the needs of the program.”

Making sure the services provided

(maintenance, equipment, labor,

capital projects) are balanced with

economic realities in the

Municipality

Technology advances have helped

make program development and

management easier – but not the

politics.

How can we answer the

“how much” questions

efficiently, so that a

potential fee-based

program can be

discussed realistically?

Remote Sensing

Remote Sensing

Uses remotely sensed data from satellite or

airborne sensors to interpret impervious cover,

instead of hand-digitizing plans or

interpolating from other records

Quickly evaluate visually and quantitatively the

area & location of impervious surfaces Image captures red, green, and blue bands of the

electromagnetic spectrum (visible light) and the Near Infrared

(NIR) spectrum used to differentiate land cover types, including

impervious surfaces and vegetation on the landscape.

Can use satellite and aerial images

– Ikonos, Quickbird, USDA NAIP

– Quickbird 4-band $65/sq km

– (w/100 sq km (38 sq mi) minimum purchase) – Better to get higher resolution - others for lower resolution

($35-55)

– Usually under $10k for most municipalities

City of South Burlington Remote Sensing

Image, True Color Composite – Quickbird

Satellite Image (July 2006)

City of South Burlington Aerial

Photograph Remote Sensing Image,

Near Infrared Spectrum (NIR)

Composite – USDA NAIP (May 2008)

Benefits

Cost effective!

Easy to link downloaded data to

municipal parcel and other GIS

data sets for analysis.

Has been evaluated for accuracy (University of Vermont & CCPRC 2002)

Can create parcel level

impervious maps (data layers) up

to and including setting &

charging stormwater fees

Easily asses changes in

impervious cover over time with

periodic re-flights

Main Issues:

Data Purchase:

• Accuracy - depends on quality of base image data (price difference

is about 40% between medium- and high-quality)

• Need 4-band imagery (red/green/blue/NIR)

• Need proper pixel size of the image relative to ground area

(optimal between six-inch and three-foot (one meter) pixel size.

Data Analysis:

• Angle of image, sparse vegetation, snow fields, compacted soil,

quarries all may be misinterpreted as impervious area

• Not completely automated – there will be labor time to process &

adjust (plus integration with utility billing)

• Accuracy of parcel data is biggest variable in how accurate the

overall assessment will be

• Plan on multiple field checks if used for actual billing!!!

City & Town of St Albans Project (2008)

City & Town of St Albans Project (2008)

Compacted soils, sparse vegetation will show up as impervious – a

community’s definition of “impervious surface” may or may not include

these areas

Once linked to parcel data, enables

parcel, ERU, fee & credit scenario analysis

Case Studies

Applications for rapid stormwater fee

assessment:

City of Burlington, VT

– Understand distribution

of impervious area by

property type

– Assess different ERUs vs

“ISU” (Impervious

surface units)

– Ultimately implemented

flat fee for SFR through

triplex and “ISU” for

Directly Assessed

Customers

Applications for rapid stormwater fee

assessment:

City & Town of St Albans, VT

– What are the revenue options for

a City-only, Town-only, or joint

City-Town stormwater utility?

– Rapid assessment of impervious

cover using NAIP

– Reasonably (!) good parcel data

– Identified crucial importance of

railroad-owned land as % of

impervious area & potential

impact on stormwater budgets

– Fee not implemented, but

analysis has helped with

development of MS4 programs

Case Study:

Ayer, Massachusetts

Ayer Stormwater Management Budgets

$2.39M sewer budget

$1.69M water budget

$0.52M solid waste budget

Proposing $312,000 for stormwater

Current Stormwater Budget $123,000 out of General Fund

Current budget does not support regulatory compliance

Not addressing aging infrastructure

More costly to address upgrades in crisis/emergency (i.e.

collapsed catch basins)

Town of Ayer Evaluation Process:

Preliminary

Town stormwater budget determined (compliance + maintenance)

Prepared preliminary parcel distribution Analysis and compared with

budget.. Rough cut fee identified

• Significant needs & inaccuracies with Town’s in parcel map,

infrastructure data

– Parcel maps & assessor data not linked

– Fitchburg State worked on mapping/GPS of storm drainage

infrastructure

Town of Ayer Evaluation Process

• Background work with Mass GIS zoning data layer to establish

classifications:

– Used Mass GIS zoning data layer merged with existing GIS

database.

– Mass GIS zoning simplified into commercial, residential and

industrial classification.

– Commercial and industrial properties further subdivided by

parcel size to assess percent impervious, create “tiers”

– Comparison made to Ayer Assessor’s database to ensure

general appropriateness of Mass GIS zoning data.

• As remote sensing data were integrated, continued to make

adjustments to parcel maps

Mass GIS, Montachusett RPC provided substantial help!

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Parcel Size Range (acres)

Ayer, MA Parcel Distribution by Lot Size

Frequency Cumulative %

Remote sensing imagery of residential

land/impervious cover in Ayer, MA

Impervious Surface Classification Sample

Ayer, MA | February 25, 2010

Town Fee Evaluation Three fee structures

prepared:

– “Straight” ERU

– ERU w/cap for parcels with

more than 10 acres of

impervious area

– Flat fee based on impervious

surface “intervals” (i.e.

parcels w/1-3 acres

impervious charged

$1000/year, etc.)

– One property-type based fee

structure was prepared

based on Mass GIS zoning

data; Properties were broken

down into residential,

commercial, industrial and

road.

Average lot size 0.2–2.0 acres

– 2,000 of the 2,458 parcels are in

this size range

Mean parcel size = 2.47 acres

Typical residential lot size is 0.5

acres with 20% impervious area

20% impervious area = 0.1 acres

= 4,356 sf

4,356 sf = 1 ERU

*note: Town Parcel Maps needed

updating for final calculations!

Various Options Easily Evaluated

1) TIERED RATE

STRUCTURE

2) ERU-BASED RATE STRUCTURE with

maximum of $3,600 per parcel

PROPERTY TYPE

PARCEL

COUNT Tiered Cost

Estimated Annual

Revenue # of ERUs Cost by ERUs

Estimated

Annual Revenue

Occupied Residential 1,693 $36 $60,948 1 $36 $60,948

Non-Residential < 1 acre 199

Varied by

ERU $35,460 1 to 10 $36 - $360 $35,460

Non-Residential 1 to 2.999 acres 78 $1,000 $78,000 10 to 30 $360 - $1080 $47,484

Non-Residential 3 to 5.999 acres 29 $1,400 $40,600 30 to 60 $1080 - $2160 $42,588

Non-Residential 6 to 8.999 acres 10 $1,800 $18,000 60 to 90 $2160 - $3240 $27,108

Non-Residential 9 to 11.999 acres 2 $2,200 $4,400 90 to 120

$3240 - $3600

max $7,200

Non-Residential > 12 acres 9 $2,600 $23,400 120 and up $3,600 $32,400

TOTALS2 2,020 $260,808

$253,188

Town parcel data required updating for final calculations to be considered accurate

It was critical to show various options to Town management as well as homeowners and

commercial/industrial property owners. Remote sensing and GIS images were notably beneficial in

explaining the impervious cover method to prospective ratepayers, enabling them to visualize directly

the basis for calculating fees.

Stormwater Utility Fee Calculations

by Incremental Impervious Area

Based on average residential impervious area

(Equivalent Residential Unit = ERU)

Larger areas in increments of the “ERU”

Evaluated range but settled on $3/month/ERU

Stormwater budget $312,000 year

Land Use

Impervious

Area (sf/ac)

Impervious

Area (sf/ac)

Fee

($/mo.)

Fee

($/yr.)

Residential 4,356 .1 $3 $36

(= 1 ERU)

Small Commercial 43,560 1 $30 $360

Larger Commercial 435,600 10 $300 $3,600

Takeaways:

Remote sensing offers a cost-effective way to make the

potential budgets and fees “real,” and to improve the quality

and accuracy of the discussion

Even if a fee-based program ultimately is not adopted,

mapping has multiple uses:

– Environmental management

– Planning

– Assessing tree canopy, vegetated conditions in watersheds

Still requires skilled GIS technical skills – which can come

through Regional Planning Commission or University

partnerships, in-house, or consultants

Bethany Eisenberg | beisenberg@vhb.com | 617.607.1852

Juli Beth Hinds | birchlineplanningllc@gmail.com| 802.324.5760

Mark Wetzel | mwetzel@ayer.ma.us | 617.607.1852

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Offices located throughout the east coast