FLOOD01805

• County: Statewide
• Community: State of Colorado
• Title: A Utility Approach to Comprehensive Storm Water Management
• Date: 7/28/1983
• Prepared For: Roger E. Krempel
• Prepared By: Marc Engomen
• Floodplain - Doc Type: Project

The fOllowing examples illustrate how the various storm drainage fees are calculated:

{ll Monthly utility fees for a commercial lot.

Address:
Area:
Runoff Coefficient (01
Rate Factor*
Operations & Maintenance
Base Rate
Monthly O&M Fee

101 West Swallow
22,776 square feet
0.95
0.95

SO.000285/ft. 2/month
22,776 (0.95) SO.000285
= S6.17/month
Footh; 11 s
SO.000109/ft. 2/month
22,776 (0,95) SO.000109
= S2.36/month

Basin:
Foothills Caital Improvements Base Rate
Monthly Capital Fee

Total Drainage Utility Fees

= S8.53/lIKlnth

*A rate factor is an average coefficient of runoff for a particular category of development. For example,
if the cal cul ated runoff coeffici ent for a property is between 0.31 and 0.50, it is pl aced in the "l i ghtU
category of development. and the rate factor for this caetgory is 0.40.

(2) Monthly.utility fees. for a residential lot.

Address:
Area:
Runoff Coefficient
Rate Factor
Operations & Maintenance
Base Rate
Monthly O&M Fee

519 Wabash Orive
7,081 square feet
0.45
0.40

SO.000285/ft. 2/month
7,081 (0.4) $0.000285
SO.81/month
McClellands-Ma;l Creek

Basin:
McClellands-Mail CreeK
Capital Improvements
Base Rate
Monthly Capital Fee

$0.000260/ft. 2/month
= 7,081 (0.4) SO.000260
$0.74/month

= $l.55/month

Total Orainage Utility Fees

(3) Basin fee (plant investment fee) for a commercial lot.

Address:
Gross Area:
Basin:
McCl ell ands-r1ail CreeK
Basin Fee Base Rate
Runoff Coefficient
Detention Reduction Factor**

3750 South Mason Street
140,378 square feet
McClel1ands-Mail Creek

.'.0,

52,877/acre
0.52
0.85

= 140,388 (2,877) 0.52 (0.B5)
= S4,098.01

Basin Fee

**Obtained from the reduction factor nomograph.
Figure 1. Calculation of various storm drainage fees.

The runoff coefficient, c, is a measure of
the surface resistance to flow. The area, A, is
gross area. The basin fee base rate, B, is a
unit cost for drainage i~provements based on the
estimated cost of improvements in the basin
master plan and the total "weighted- area of the
drainage basi!l. The detention reduction factor,
R, reduces the amount of the drainage fee for
properti es wh; ch provi de on-s1 te detent; on and

therefore reduce the peak stormwater runoff.

The method of determining the appropri-
ate detention reduction factor is relatively
straight-forward. The nomograph in figure 2 was
developed for this purpose. The unit volume of
the on-site detention pond (cubic feet of storage
provided per acre of tributary area) is entered
at the left side. At the intersection of this

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