1. CIM
CITY COMMISSION INFORMATION MEMORANDUM
June 26, 2017
ADMINISTRATIVE BRIEF FROM Jim Kowach
Department of Public Works
Stormwater Design and Utility Funding
Spring rains in Salina typically expose some areas of routine street flooding and slow
draining storm sewers. Intersections such as Santa Fe and Prescott, Neal and Ray, and
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Iron and 4 are a few areas that frequently fill with water until the rain ceases to allow
the slow draining system to empty. City staff periodically take questions from the public
on what level the storm sewer systems are designed for and what types of rain events
can these systems be expected to convey before flooding occurs.
Per Salina Code Sec. 36-The planning commission shall not approve any plat of a
subdivision which does not make adequate provisions for storm water runoff control.
This control may be accomplished through the use of temporary detention basins, open
channels and/or closed conduits. The applicant shall be required to submit a drainage
report prepared by a licensed professional engineer which examines the effects of the
proposed subdivision on all upstream and downstream drainage conditions. The
adequate
City design criteria for storm drainage systems (revised January 1998) state that
stormwater shall generally be carried in storm sewer and shall be designed
to prevent flooding of improvements by storms having the return period designated
below.
10-year (10% return period) - Enclosed drainage structures in residential areas;
original conditions on undeveloped areas being considered for re-zoning,
platting; etc.
25-year (4% return period) - Enclosed drainage structures in commercial areas;
detention ponds; arterial street culverts; and open channels.
Detention Storage As land use changes
from open space/agricultural to
suburban/commercial, these alterations
can affect how the land responds to rainfall.
The increased impervious area,
compaction of the natural soils and the
filling of natural depressions results in less
infiltration, more runoff volume, higher rates
of runoff, reduction in storage capacity and
degradation of stormwater quality.
Stormwater ponds are designed to mitigate
these changes by providing storage and
reducing peak discharge rates.
Laurie Detention Pond
Enclosed Storm Sewers Underground storm sewers along with open channels and
paved streets (with curb and gutter) help to convey stormwater to these detention ponds
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as well as larger drainage ways (4 Street slough, old Smoky Hill River channel,
Schilling ditch, etc.). These storm sewer systems have been built over many years with
different private and public projects as the City has developed. This patchwork system,
especially in older parts of Salina, may not have been designed to current criteria and
thus, does not perform as well in high intensity rain events. Much of this system is also
in need of maintenance and upkeep with a systematic improvement plan to address
deficiencies and needs.
Stormwater Utility (SWU) Funding A growing trend for municipalities to fund storm
In stormwater industry parlance,
defines stormwater operations and management, an Organization that is responsible for
governance and a Funding approach that provides dedicated financing. Stormwater is
increasingly beginning to be perceived as a resource to be protected and managed
similar to drinking water resources. To do so effectively, the Program, Organization and
Funding aspects have to be aligned and holistically addressed, as it is done in the water
and wastewater sectors of the utility industry (2014 Stormwater Utility Survey, a BLACK
& VEATCH repor
Per these figures, 34 cities in
Kansas have established SWU
fees, most recently McPherson
(9/1/16). The city of Lindsborg is
having a public meeting this week
to look at this issue as well.
Nationwide, the average monthly
single family residential fee was
$4.79, the standard deviation was
$3.34 and the median fee was
$4.00. Most fees go up over time
reflecting an increase in the
Consumer Price Index (CPI).
Some communities actually tie the
As has been
observed in previous surveys, no state
has all high fees. Even states with the
higher fees also have utilities with much
lower fees. The range of fee amounts
probably reflects stormwater needs and
local political realities.
The most widely used method of
funding is the Equivalent Residential
Unit system (ERU). An ERU is usually
the average impervious area on a single family residential parcel, although some
communities define it as the average of all residential parcels. Fees for non-residential
properties are proportional to the ratio of the parcel impervious area to the
.Usually most parcels in a community are residential parcels and these may all
have a single fee or may be divided into a few tiers. This simplifies the administration of
the utility (Western Kentucky University Stormwater Utility Survey 2014
The City of Hays ERU equals 3,369 square feet, and they charge $3.62 per ERU. When
the Utility was implemented, the community went through a lengthy process. The
governing body chose a lower cost option with the thought process of the General Fund
paying for some services such as drainage way maintenance and street sweeping.
Those costs have now been shifted to the Stormwater Utility.
The City of Salina storm sewer system represents a major infrastructure investment with
110 centerline miles of underground pipe systems and nearly 0.5 miles of force mains.
With many of our Kansas cities having already established fees for this, staff will be
exploring a SWU for Salina in the near future.
MEETING
Enclosed are other items on the agenda. If any Commissioner has questions or cannot
attend the meeting, please contact me.
Jason A. Gage, City Manager