Stormwater Utility Fee Advisory / Technical Committee Meeting

March 14, 20114 – 5:30 p.m.

March 14, 2011Meeting Agenda

1. Minutes (February 14, 2011)2. Member Inquiries / Staff Follow-up3. Stormwater Management – Revenue Plan4. Public Participation5. Next Meeting (April 11, 2011)6. Adjourn

Stormwater Utility FeeAdvisory Technical Committee Meeting

March 14, 2011

Agenda Item 3Revenue Plan

Rate Structure

Background InformationRevenue Plan defines how the costs of the

Expenditure Plan will be allocatedRate structure contains the specifics of the plan

Program Costs (from Expenditure Plan)

- Other Revenues (various fees, interest, etc)

+ Revenue Reductions (bad debt, credits, etc)

= Revenue Needed from Fee

÷ Rate Base (total number of billing units)

= Rate

Stormwater Utility FeeAdvisory Technical Committee Meeting

March 14, 2011

Agenda Item 3Rate StructureBase Structure

Impacts of Development on Runoff

Impact of development on runoff peakRational Formula

Q = C i A

where Q = discharge rateC = runoff coefficienti = rainfall intensityA = drainage area

“C” increases with increasing intensity of development

(imperviousness)

Impact of development on runoff volumeSimple Method

V = P Rv A / 12

where V = runoff volumeP = rainfall depth

A = drainage areaRv = runoff coefficient

= 0.05 + 0.009 ii = impervious percentage

Impact of development on runoff qualitySimple Method

L = V EMCL = (P Rv A / 12) EMC

where L = pollutant loadV = runoff volume EMC = event mean concentrationP = rainfall depthRv = runoff coefficient

= 0.05 + 0.009 ii = impervious percentage

Imperviousness as a rate method Imperviousness is utilized in hydrology as the

measuring stick for intensity of development

Multiple ways to include imperviousness in fee calculations: Straight imperviousness (actual or incremental blocks) Equivalent Runoff Units, ERUs (single family flat rate) Impervious plus gross area Impervious plus pervious area Intensity of development

Each method has pros and cons

Rate Bases

Imperviousness is the only physical parameter per parcel

Direct correlation to runoff and thus to demand

Easily measured and verified

Impervious Area

Rate Bases Compound rate structure

Imperviousness for development

Gross area component for entire property

Applies some costs to undeveloped properties

Can set minimum threshold for billing

Impervious plus Gross Area

Rate Bases

Based on the runoff potential of impervious and pervious areas

Directly compute billing units per parcel

Can apply program costs to undeveloped properties

Impervious Plus Pervious Area(Effective Hydraulic Area)

Rate Bases

IOD Land Use

Parking

Commercial

Institutional

Multi-Family

Single Family - small lot

Single Family - large lot

Vacant

Utilizes the average runoff potential by land use Gross area Land use IOD factor

Directly compute billing units per parcel

Typically not accurate enough for billing

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Intensity of Development

How A Fee Is Calculated

Significant aspects of rate bases Single family residential

Typically flat rates

Some use tiers to add equity

Some (very few) measure every parcel

Determines (typically) the base rate unit

Other parcels

Measure impervious area and compute billing units

How A Fee Is Calculated

Non-single family = 10,000 square feet impervious= 3.33 ERUs - credit

Impervious Only(Equivalent Residential Unit,

ERU)

Quarter acre lots1 ERU = 3,000 square

feet of impervious area

Single family residential= 3,000 sq ft impervious= 1 ERU

How A Fee Is Calculated

Non-single family = 10,000 square feet impervious= 0.218 + 0.002 – credit= 0.220 – credit

Impervious Plus Pervious Area

(Effective Hydraulic Area, EHA)

Quarter acre lotsEHA = 95% of impervious area

+ 10% of pervious area

Single family residential= 3,000 sq ft impervious= 0.065 + 0.018 units= 0.083 units

Rate Base DiscussionDo you have questions / comments about any of the rate base concepts? What did you like / not like about the various methods and their approaches?

Impervious only Impervious plus gross areaImpervious plus pervious areaIntensity of development

Stormwater Utility FeeAdvisory Technical Committee Meeting

March 14, 2011

Agenda Item 3Rate Structure

Residential Rate Simplifiers

Imperviousness in ChampaignImperviousness is a significant part of all

stormwater rate structures

For the initial phase of the project an estimate of total imperviousness was needed:Identified primary land usesDetermined the statistically significant sample

sizes for each land use Digitized the appropriate number of samples

for eachEstimated rate base size based on the product

of gross area and measured intensity of development by land use

Imperviousness by Land UseLand Use

No. of Parcels Gross Area

Impervious %

Impervious Area

Single Family 18,050 167,040,210 62,777,900

Duplex 317 2,804,024 1,102,526

Multi-Family 824 19,471,798 51% 12,250,300

Condo 333 2,281,497 66% 1,514,686

Industrial 62 7,347,754 68% 4,973,695

Commercial 1,811 108,411,645 71% 76,636,192

Churches 149 6,449,735 53% 3,437,064

Government 757 65,589,695 32% 20,785,374

University 160 24,825,203 39% 9,785,206

Misc 204 25,202,975 32% 1,337,392

Agriculture 79 71,417,617 1% 857,011

Total Area 22,746 500,842,152 195,457,346

Approximate Areas in Square Feet

”Bundling” ImperviousnessIssue: How do you bill the proposed $2.25M (or

$3.21M) annual program cost? Billing per square foot of impervious area (195M) results

in a fee of $0.0115 / sq ft / yr (not modeled) and thousands of units to be billed per ratepayer

Other utilities “bundle” the units of serviceElectric utilities measure in kilowatt hours Water utilities sell water in thousands of gallons

Imperviousness is typically “bundled” in one of two ways:In increments of 500 or 1000 square feetIn “equivalent” units, such as based on the average

imperviousness on a single family residential property

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”Bundling” ImperviousnessLand Use

Impervious Area*

500 Sq Ft Units

1000 Sq Ft Units

3478 Sq Ft Units

Single Family 62,777,900 125,556 62,778 18,050

Duplex 1,102,526 2,205 1,103 317

Multi-Family 12,250,300 24,501 12,250 3,522

Condo 1,514,686 3,029 1,515 436

Industrial 4,973,695 9,947 4,974 1,430

Commercial 76,636,192 153,272 76,636 22,035

Churches 3,437,064 6,874 3,437 988

Government 20,785,374 41,571 20,785 5,976

University 9,785,206 19,570 9,785 2,816

Misc 1,337,392 2,675 1,337 385

Agriculture 857,011 1,714 857 246

Total Rate Base 195,457,346 390,915 195,457 56,201

*Approximate Area in Square Feet

”Bundling” ImperviousnessTherefore, $0.0115 / sq ft / yr could be billed as:

$ 5.75 / 500 sq ft / yr $0.44 / 500 sq ft / mo$11.50 / 1000 sq ft / yr $0.88 / 1000 sq ft / mo$40.00 / 3478 sq ft / yr $3.33 / 3478 sq ft / mo

The number of billing units for single family residential properties under a flat rate method would be:7.0 units at 500 sq ft bundles3.5 units at 1000 sq ft bundles1 unit at 3478 sq ft bundles, or

1 equivalent residential unit (ERU)

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Single Family Imperviousness

Residential Rate SimplifierIs there a need to further refine the billing within the single family residential properties?Why some communities do add detail;

decreased fees for less imperviousnessincreased fees for more imperviousness

Illinois communities with tiered single family rates:Bloomington, Moline, Rock Island

Residential Rate Simplifier

Is there a need to further refine the billing within the single family residential properties?Why some communities do not add detail;

increased cost of master account file creationincreased cost of master account file maintenanceincreased uncertainty in account calculationvariations within flat rate typically low (± $1.00/mo)

Illinois communities with one rate for all single family:Morton, Normal, Highland Park

Questions?