Transcript Stormwater Utility Fee Advisory / Technical Committee Meeting

March 14, 2011
4 – 5:30 p.m.
March 14, 2011
Meeting Agenda
1.
2.
3.
4.
5.
6.
Minutes (February 14, 2011)
Member Inquiries / Staff Follow-up
Stormwater Management – Revenue Plan
Public Participation
Next Meeting (April 11, 2011)
Adjourn
Stormwater Utility Fee
Advisory Technical
Committee Meeting
March 14, 2011
Agenda Item 3
Revenue Plan
Rate Structure
Background Information
 Revenue Plan defines how the costs of the Expenditure
Plan will be allocated
 Rate 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
= Rate
(total number of billing units)
Stormwater Utility Fee
Advisory Technical
Committee Meeting
March 14, 2011
Agenda Item 3
Rate Structure
Base Structure
Impacts of Development on Runoff
Impact of development on runoff peak
Rational Formula
Q=CiA
where
Q
C
i
A
=
=
=
=
discharge rate
runoff coefficient
rainfall intensity
drainage area
“C” increases with increasing intensity of development
(imperviousness)
Impact of development on runoff volume
Simple Method
V = P  Rv  A / 12
where
V =
P =
A =
Rv =
=
i =
runoff volume
rainfall depth
drainage area
runoff coefficient
0.05 + 0.009  i
impervious percentage
Impact of development on runoff quality
Simple Method
L = V  EMC
L = (P  Rv  A / 12)  EMC
where
L
V
EMC
P
Rv
i
=
=
=
=
=
=
=
pollutant load
runoff volume
event mean concentration
rainfall depth
runoff coefficient
0.05 + 0.009  i
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
Impervious Area

Imperviousness is the
only physical parameter
per parcel

Direct correlation to
runoff and thus to
demand

Easily measured and
verified
Rate Bases
Impervious plus Gross Area
Compound rate structure
 Imperviousness for
development
 Gross area component
for entire property
 Applies some costs to
undeveloped properties
 Can set minimum
threshold for billing

Rate Bases
Impervious Plus Pervious Area
(Effective Hydraulic Area)

Based on the runoff
potential of impervious
and pervious areas

Directly compute billing
units per parcel

Can apply program
costs to undeveloped
properties
Rate Bases
Intensity of Development
IOD
Land Use

Parking
Commercial
Increasing Intensity
Institutional
Multi-Family
Vacant

Gross area

Land use

IOD factor

Directly compute billing
units per parcel

Typically not accurate
enough for billing
Single Family - small lot
Single Family - large lot
Utilizes the average runoff
potential by land use
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
Impervious Only
(Equivalent Residential Unit, ERU)
Quarter acre lots
1 ERU = 3,000 square
feet of impervious area
Single family residential
= 3,000 sq ft impervious
= 1 ERU
Non-single family
= 10,000 square feet impervious
= 3.33 ERUs - credit
How A Fee Is Calculated
Impervious Plus Pervious Area
(Effective Hydraulic Area, EHA)
Quarter acre lots
EHA = 95% of impervious area
+ 10% of pervious area
Single family residential
= 3,000 sq ft impervious
= 0.065 + 0.018 units
= 0.083 units
Non-single family
= 10,000 square feet impervious
= 0.218 + 0.002 – credit
= 0.220 – credit
Rate Base Discussion
Do 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 area
 Impervious plus pervious area
 Intensity of development
Stormwater Utility Fee
Advisory Technical
Committee Meeting
March 14, 2011
Agenda Item 3
Rate Structure
Residential Rate Simplifiers
Imperviousness in Champaign
 Imperviousness 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 uses
 Determined the statistically significant sample sizes for
each land use
 Digitized the appropriate number of samples for each
 Estimated rate base size based on the product of gross
area and measured intensity of development by land use
Imperviousness by Land Use
Land Use
Single Family
No. of
Parcels
Gross Area
Impervious
%
Impervious
Area
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
62
7,347,754
68%
4,973,695
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
Industrial
Commercial
Approximate Areas in Square Feet
195,457,346
”Bundling” Imperviousness
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 service
 Electric 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 feet
 In “equivalent” units, such as based on the average
imperviousness on a single family residential property
Numbers are Approximate
 Issue: How do you bill the proposed $2.25M (or $3.21M)
”Bundling” Imperviousness
Land Use
Single Family
Impervious
Area*
500 Sq Ft
Units
1000 Sq Ft
Units
3478 Sq Ft
Units
62,777,900
125,556
62,778
18,050
1,102,526
2,205
1,103
317
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
76,636,192
153,272
76,636
22,035
3,437,064
6,874
3,437
988
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
857,011
1,714
857
246
195,457,346
390,915
195,457
56,201
Duplex
Multi-Family
Commercial
Churches
Government
Agriculture
Total Rate Base
*Approximate Area in Square Feet
 Therefore, $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 bundles
 3.5 units at 1000 sq ft bundles
 1 unit at 3478 sq ft bundles, or
1 equivalent residential unit (ERU)
Numbers are Approximate
”Bundling” Imperviousness
Single Family Imperviousness
Residential Rate Simplifier
Is there a need to further refine the billing within the
single family residential properties?
 Why some communities do add detail;
 decreased fees for less imperviousness
 increased 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 creation
 increased cost of master account file maintenance
 increased uncertainty in account calculation
 variations within flat rate typically low (± $1.00/mo)
 Illinois communities with one rate for all single family:
 Morton, Normal, Highland Park
Questions?