HomeMy WebLinkAbout2024-07-01 I06 Waukee Standard Specifications for Public Improvements_AdoptionAGENDA ITEM:
CITY OF WAUKEE, IOWA
CITY COUNCIL MEETING COMMUNICATION
MEETING DATE: July 1, 2024
AGENDA ITEM:Consideration of approval of a resolution approving and adopting 2024 City
of Waukee Standard Specifications for Public Improvements
FORMAT:Resolution
SYNOPSIS INCLUDING PRO & CON: The City of Waukee Standard Specifications for Public
Improvements was last updated in February 2023. Staff have determined that amendments to certain
post construction stormwater management requirements should be made to the existing requirements
in the Waukee Standard Specifications for Public Improvements in order to comply with Section
364.3(18) of the Code of Iowa (fka Senate File 455) and its effective date of July 1, 2024.
FISCAL IMPACT INCLUDING COST/BENEFIT ANALYSIS:
COMMISSION/BOARD/COMMITTEE COMMENT:
STAFF REVIEW AND COMMENT:
RECOMMENDATION: Approve the resolution.
ATTACHMENTS: I. Resolution
II. 2024 Waukee Specifications for Public Improvements with Changes
Highlighted
PREPARED BY: Rudy Koester
REVIEWED BY: Rudy Koester RK
PUBLIC NOTICE INFORMATION –
NAME OF PUBLICATION:
DATE OF PUBLICATION:
I6
THE CITY OF WAUKEE, IOWA
RESOLUTION 2024-
APPROVING AND ADOPTING 2024 CITY OF WAUKEE
STANDARD SPECIFICATIONS FOR PUBLIC IMPROVEMENTS
IN THE NAME AND BY THE AUTHORITY OF THE CITY OF WAUKEE, IOWA
WHEREAS, the City of Waukee, Dallas County, State of Iowa, is a duly organized Municipal
Organization; AND,
WHEREAS, the Waukee City Council has determined that amendments to certain post construction
stormwater management requirements should be made to the existing requirements in the Waukee Standard
Specifications for Public Improvements in order to comply with Section 364.3(18) of the Code of Iowa (fka
Senate File 455) and its effective date of July 1, 2024; AND,
WHEREAS, The Waukee Standard Specifications have been amended in accordance with the standards
of the industry, complying with sound engineering principles and comply with the recently approved
Section 364.3(18) of the Code of Iowa; AND,
NOW THEREFORE, BE IT RESOLVED THAT:
1.The document entitled Standard Specifications for Public Improvements, Waukee, Iowa, is
hereby adopted.
2.These Standard Specifications shall be followed and used by the City in considering, permitting,
inspecting, and otherwise dealing with the construction of public improvements within the City.
3.These Standard Specifications may, from time to time, be amended, changed, or altered by action
of the City Council.
4.These Standard Specifications shall be used for all projects submitted after the date of adoption of
this resolution.
Passed by the City Council of the City of Waukee, Iowa, and approved the 1st day of July, 2024.
____________________________
Courtney Clarke, Mayor
Attest:
___________________________________
Rebecca D. Schuett, City Clerk
RESULTS OF VOTE: AYE NAY ABSENT ABSTAIN
Anna Bergman Pierce
R. Charles Bottenberg
Chris Crone
Rob Grove
Ben Sinclair
2-1
PART 2 – DESIGN STANDARDS
INDEX
1. GENERAL 8. SUMP PUMP DRAIN LINES
2. STREETS 9. SUBDIVISION LOT GRADING
3. SHARED USE PATHS AND MAINTENANCE
4. STORM SEWERS 10. STREET LIGHTS
5. SANITARY SEWERS 11. TRAFFIC SIGNALS
6. PUMPING STATIONS 12. FIBER OPTIC LINES
AND FORCE MAINS 13. STORMWATER MANAGEMENT
7. WATER MAINS
1. GENERAL
1.1 This section sets forth minimum design standards to be used for design of
streets, sidewalks, trails, sewers, water mains, sump pump drain lines, traffic
signals and street lights in subdivisions in the City of Waukee, Iowa.
1.2 The design standards specified hereinafter are minimum standards; all plans are
subject to review and approval by the City.
1.3 Provide all lots in subdivision with water, sanitary sewer and sump pump drain
service lines; stub sanitary sewer service 10' inside lot line; stub water and
sump pump drain services to lot line; omit Pipe Bedding Material on the last 5’
of sanitary service pipe at stub end; install curb stop valve and box on lot lines.
1.4 Provide geotechnical exploration and report for all proposed street, sanitary and
storm sewer and water main projects in accordance with the SUDAS Design
Manual; submit written report and test results to City for review.
2. STREETS
2.1 Design streets in accordance with SUDAS Design Manual, Subdivision Ordinance
of the City of Waukee, Iowa, and the following standards:
Design Standards
2-2
2.2 Culs-de-sac are subject to approval by City on project-by-project basis; provide
areas designated for snow removal storage from cul-de-sac.
2.2.1 Provide temporary 40' radius, granular surfaced turn around at temporary
ends of portland cement concrete pavement where temporary pavement
end is more than 150' from a street intersection. Other temporary turn
around configurations may be acceptable as approved by the City
Engineering Department. Granular surfacing to be a total of 8” thick with 4”
thick of 3” gradation rock base and with 4” thick of 1” road stone on top.
2.3 Minimum pavement thickness:
2.3.1 Local service and loop streets: 7" non-reinforced portland cement
concrete over 12” thick compacted natural subgrade.
2.3.2 Minor collector streets: 7” non-reinforced portland cement concrete
over 6” thick granular modified subbase with 12” thick compacted
natural subgrade.
2.3.3 Major collector streets: 8” non-reinforced portland cement concrete
over 6” thick granular modified subbase with 12” thick compacted
natural subgrade.
2.3.4 Minor arterial streets: 9" non-reinforced portland cement concrete
over 6” thick granular modified subbase with 12” thick compacted
natural subgrade.
2.3.5 Major arterial streets: 10” non-reinforced portland cement concrete
over 6” thick granular modified subbase with 12” thick compacted
natural subgrade.
2.3.6 Construction requirements for reinforced and non-reinforced portland
cement concrete pavement are set out in PORTLAND CEMENT
CONCRETE PAVEMENT.
Design Standards
2-3
2.4 Minimum pavement width:
Design Elements Local Cul-de-
sac
Collector Arterial
Minor Major Minor Major
General
Lane width (single lane) (ft) 11 11 11 12 12 12
Two-Way Left-Turn Lanes (TWLTL) (ft) N/A N/A 12 14 14 N/A
Object setback (ft) 1.5 1.5 3.0 3.0 3.0 3.0
Urban (2-lane undivided roadway)
Roadway width with parking (one-side) (ft) 29 26 31 N/A N/A N/A
Roadway width without parking (ft) 26 26 26 29 31 N/A
Boulevard (2 or 4-lane divided roadway)
Roadway width without parking (one side) (ft) N/A N/A N/A 181 262 412
Raised median with left-turn lane (ft) N/A N/A N/A 18 20 30
1Based on one lane each direction
2Based on three lanes each direction
2.5 Minimum pavement radius at intersections: meet requirements of SUDAS Design
Manual.
2.6 Pavement gutter grades: minimum 0.60% and maximum 5.0% unless
otherwise approved by City.
2.7 Construct streets in accordance with details shown on Standard Drawings;
center pavement on right-of-way, unless otherwise permitted by City.
2.8 Minimum pavement diameter for culs-de-sac when approved by City: 80';
maximum length of street to serve culs-de-sac: 600' from end or radius of
intersecting perpendicular street to beginning of radius for cul-de-sac.
2.9 Provide depressed curb where sidewalks intersect streets and at driveways
constructed prior to pavement; construct 6" integral curb at other locations; mill
or saw cut and remove 6" curb at sidewalks and driveways constructed after
pavement. Sidewalks and crosswalks to meet requirements of Americans with
Disabilities Act (ADA) and Public Right of Way Access Guidelines (PROWAG).
2.10 Construct driveway approaches as shown on Standard Drawings; single driveway
approach width 10'; double driveway approach width 18'; triple driveway approach
width 22’ unless otherwise approved by City.
Design Standards
2-4
2.10.1 Construct commercial driveway and private street approaches in
accordance with SUDAS Standard Specifications Figure 7030.101 for
Concrete Driveway, Type A except minimum thickness is 8 inches.
2.11 Provide red nine dot object markers (OM4-2), 2 in each lane and one at centerline,
at dead ends of streets.
2.12 City to provide street name signs, speed limit signs, stop signs and no parking signs
as specified hereinafter; use symbol signs where appropriate. Subdivider to
reimburse City for cost of materials and installation of signs.
2.13 Surface and pavement replacement of existing streets:
2.13.1 Asphalt and seal coat streets: replace with asphalt or concrete as
specified.
2.13.2 Granular surfacing: replace with granular surfacing as specified.
2.13.3 Concrete curb and gutter: minimum pavement thickness as
specified.
2.14 Provide subdrain on all public street improvements unless specifically stated in
geotechnical report that subdrain is not needed. Provide storm sewer, sump pump
drain line, or subdrain on each side of street. Subdrain shall be 6” minimum
diameter.
2.15 Provide appropriate street network enhancements based upon projected traffic
volumes warranting additional travel lanes, turning lanes, or signalization.
2.15.1 Projected traffic volumes to be based upon development anticipated
within a 20 year planning period or as directed by the City. Traffic studies
to provide a 5 year and 20 year projection.
2.15.2 Costs associated with the street network enhancements and design will
be distributed between Subdivider and City based upon the Subdivider’s
contribution to the traffic volumes necessitating the enhancements.
2.16 Provide commercial drives with thickened approach between sidewalk and
edge of street pavement; minimum 8" thick; install expansion joint.
2.17 Subdivider responsible for installing pavement markings at improved street
intersections that include turning lanes as directed by City.
Design Standards
2-5
2.17.1 For purposes of these requirements the intersection will include all
areas within 250 feet of the intersection covering the required
improvements.
2.17.2 Subdivider to create a plan identifying all required markings at
intersection for City’s review.
2.17.3 Markings to be provided include centerline (2 solid or dashed yellow),
turn lane(s) (1 solid white), lane separation(s) (1 dashed white),
pedestrian crossings, (solid white longitudinal lines or bars parallel to
vehicle traffic flow), and directional arrows (solid white).
2.17.4 Markings to be comprised of Durable Paint.
3. SHARED USE PATHS
3.1 Design shared use paths including sidewalks and trails in accordance with
Americans with Disabilities Act (ADA) and Public Right of Way Access Guidelines
(PROWAG).
3.2 Curb ramps are required to be constructed with public improvements.
3.3 Provide minimum 1’ clear zone from edge of shared use paths to edge of hydrants,
poles, street signs, street lights and other obstacles.
3.4 Sidewalks:
3.4.1 Construct 5' wide sidewalks on both sides of street; or as directed by
City; place inside edge of sidewalk 1' outside property line or as directed
by City; conform to details shown on Standard Drawing Nos. 46 through
52 unless otherwise approved by the City.
3.4.2 Provide 1.5% +/- 0.5% cross slope.
3.5 Multi use trails:
3.5.1 Applicable to bike trails and multi-use trails including locations where
trail replaces standard sidewalks.
3.5.2 Construct on prepared subgrade as specified for driveway approaches
and sidewalks in EARTHWORK AND INCIDENTALS FOR PAVEMENT.
Design Standards
2-6
3.5.3 Construct 10’ wide portland cement concrete surfacing, 6” minimum
thickness with maximum 10’ transverse joint spacing; thicken trail to 7”
at driveways and street crossings. Provide 1.5% +/- 0.5% cross slope.
Construct as specified for driveway approach and sidewalk construction
in PORTLAND CEMENT CONCRETE PAVEMENT.
3.5.4 Provide 2’ wide graded shoulder each side; sod shoulders.
4. STORM SEWERS
4.1 Provide adequately sized storm sewers and sump pump drain lines. Design
storm sewers in accordance with SUDAS Design Manual, Subdivision
Ordinance of the City of Waukee, Iowa and the following standards.
4.2 Determine runoff using the Rational Formula, Q=CIA, where:
Q = maximum rate of runoff in cubic feet per second.
C = runoff coefficient; use coefficients consistent with type of surfaces in
drainage area.
I = average rainfall intensity in inches per hour for the period of rainfall of a given
frequency having a duration equal to the time of concentration.
A = drainage area in acres.
4.3 Use 10-year storm frequency and the Mean Frequency Distribution for Storm
Periods referenced under Paragraph 4.6 to determine intensity for storm sewer
system including intakes, structures, and pipes except as follows:
4.3.1 Use 100-year storm frequency for future development without regard for
stormwater detention flow reduction for culvert design under roadways
where roadway embankment blocks drainageway.
4.3.2 Use 100-year storm frequency for future development storm sewers
draining sump area in roadways and private lands unless drainage
easements are provided for all areas inundated during 100-year storm.
Design Standards
2-7
4.4 City will consider open channel storm water drainage with a 15" dia. double wall
polyethylene or reinforced concrete pipe subdrain when required pipe diameter is
greater than 48".
4.5 Storm sewers, intakes and other structures located within the street right-of-way
shall not discharge storm water during a less than or equal to 10-year storm
frequency storm event into normally dry drainage swales located on private
property unless otherwise permitted by City.
4.6 Mean Frequency Distribution for Storm Periods per the Iowa Stormwater
Management Manual (ISWMM).
4.7 Use minimum of 15-minute time of concentration for single family residential
area storm sewers; time of concentration for all other developments will be
reviewed by City.
4.8 Minimum pipe size: 15" except for intake cross-runs which shall be 12" minimum
diameter.
4.9 No bends or pipe deflections permitted on storm sewers unless otherwise
permitted by City.
4.10 Storm sewers that cross a street shall cross the street at no more than
15 degrees from perpendicular. Intent is to locate storm sewer and the intakes
on each side of the street within the same pavement panel.
4.11 Maximum velocity within pipe (1/2 full): 15’ per second. Pipe slopes that exceed
the following chart are not allowed:
Pipe Diameter Maximum Slope
(in.) (%)
12 10.9
15 8.1
18 6.3
21 5.1
24 4.3
30 3.2
36 2.5
42 2.0
48 1.7
54 1.4
Design Standards
2-8
4.12 Curb intakes:
4.12.1 Single, SUDAS Standard Specifications Type SW-501, SW-502, SW-503 or
SW-504.
4.12.2 Double, SUDAS Standard Specifications Type SW-505 or SW-506.
4.12.3 Provide SUDAS Standard Specifications Types SW-501 through SW-506
Curb Intakes when street grade is less than 5.00%; provide special intakes
when street grade is 5.00% or greater; consult with City Engineering
Department.
4.12.4 Location: up grade from intersections, sidewalk ramps and other
locations to meet specific topographic conditions; locate outside of
intersection radius.
4.12.4.1 Install at least one intake at the low point of the street grade.
4.12.4.2 Install intake no further than 500 feet from the street high
point.
4.12.4.3 Maximum spacing 400 feet regardless of gutter flow capacity.
4.12.5 Connecting pipes: size to accommodate flow into intake without
surcharging intake.
4.13 Area intakes:
4.13.1 Rectangular area intake: SW-511.
4.13.2 Circular area intakes: SW-512 with Type 4 flat grate.
4.13.3 Open sided area intake: SW-513.
4.13.4 Connecting pipes: size to accommodate flow into intake without
surcharging intake.
4.14 Manholes: SUDAS Standard Specifications Types SW-301, SW-401, SW-402, SW-
403, SW-404 or SW-405 modified as specified in STORM SEWERS AND
STRUCTURES or Standard Drawings Types Special Manhole or Shallow Manhole.
4.15 Cleanouts: SUDAS Standard Specifications Figure 4040.232 Types A-1 or B.
Design Standards
2-9
4.16 Manholes, intakes and structures required that are larger or deeper than those
shown in SUDAS Standard Specifications shall be designed and certified by a
licensed professional engineer in the State of Iowa.
4.17 Provide minimum 8” dia. perforated subdrain surrounded by pea gravel or
minimum 3’ wide concrete flume along rear lot lines or side yards where surface
flowage has 2% or less longitudinal slope; provide flat grate intakes in areas
where standing water is present after a 1” rainfall event after finished grading of
the site is completed; comply with material standards for subdrains.
4.17.1 Minimum slope of flume is 0.5% with ponding depth less than or equal
to 1”.
4.17.2 Subdrain to be tied into the public storm sewer system or outletted into
a detention facility designed to handle the 100 year storm event.
4.17.3 Cleanouts or intakes to be provided a maximum of every 150 feet from
the point of outlet and at deadends or as directed by the City.
Use cleanouts as specified hereinbefore except use slotted casting.
5. SANITARY SEWERS
5.1 Comply with design standards contained in the SUDAS Design Manual and in
CHAPTER 12 - IOWA STANDARDS FOR SEWER SYSTEMS from IOWA WASTEWATER
FACILITIES DESIGN STANDARDS published by the IDNR.
5.1.1 Size lateral sewers for residential areas to accommodate flow of
500 gallons per capita per day; volume of flow from areas other than
residential subject to approval by City. Size trunk sewers as directed by
the City.
5.2 Sanitary sewer service connections:
5.2.1 Minimum service pipe size for single family dwellings: 4" at minimum
slope of 1% or as specified in the adopted Plumbing
Code.
5.2.2 Minimum service pipe size for all other types of buildings: 6" at
minimum slope of 1% or as specified in the adopted Plumbing Code.
5.2.3 Shared sewer services from multiple buildings that are located on
separately owned lots are not allowed.
Design Standards
2-10
5.2.4 Cleanouts to be provided a maximum of every 150 feet or as directed
by the City. Use cleanouts as specified hereinbefore.
5.2.5 Label invert elevations at ends of sewer service stubs on construction
drawings.
5.3 Manholes: SUDAS Standard Specifications Types SW-301, SW-302,
SW-303, SW304, SW-305 or Standard Drawings Types Special Manhole or Shallow
Manhole. High point manholes are not allowed.
6. PUMPING STATIONS AND FORCE MAINS
6.1 Comply with design standards contained in the SUDAS Design Manual,
SANITARY SEWERS AND APPURTENANCES and in CHAPTER 13 - SEWAGE
PUMPING STATIONS from IOWA WASTEWATER FACILITIES DESIGN STANDARDS
published by the IDNR.
6.1.1 Pumping station capacity: size for maximum rate of flow from connected
sewers.
6.1.2 Provide at least 2 pumps of equal capacity, each capable of pumping
maximum flow; if more than 2 pumps, size pumps so that with largest
pump out of service remaining units have capacity for maximum sewage
flow.
6.1.3 Provide in-place standby power system; provide for automatic and
manual start-up, automatic load transfer and exercising of system under
load.
6.1.4 Size force main to maintain velocity of 2' per second at design
average flow and pass 3" solids.
6.1.5 Provide fence around pumping station site.
6.1.6 House major pump controls in heated above ground structure; provide
disconnect switches for pumps and all other electrical equipment; blend
pumping station superstructure with surrounding development
including landscaping.
6.1.7 Provide automatic pump alternators on multiple pump installation.
Design Standards
2-11
6.1.8 Provide stainless steel guide rails, cable holders, chain, bolts and
appurtenances inside wet well.
6.1.9 Provide magnetic flow meter on pump discharge pipe.
6.1.10 Provide water supply with yard hydrant.
7. WATER MAINS
7.1 Comply with design standards contained in the SUDAS Design Manual and in
RECOMMENDED STANDARDS FOR WATER WORKS (Ten States Standards) as
adopted by the IDNR.
7.1.1 Minimum water main size: Residential R-1 and Residential R-2 zoning: 8".
Water main size other than in residentially zoned areas subject to
approval by City.
7.1.2 Size major water mains as directed by the City.
7.1.3 Maximum dead end water main length: 300’.
7.2 Isolating valve spacing:
7.2.1 Residential R-1 and Residential R-2 zoning: 800' maximum and at street
intersections.
7.2.2 Other zoning: 400' maximum and at street intersections.
7.2.3 On all private lines at the connection with the City main.
7.3 Provide fire hydrant within 25 feet of each street intersection, measured from
an end of a street paving return. Equally space hydrants between
intersections, maximum hydrant spacing: 300', unless otherwise directed by
City.
7.3.1 Provide hydrant at entrance and at end of culs-de-sac when approved by
City; maximum spacing as specified hereinbefore.
7.4 Minimum water service size: 1".
Design Standards
2-12
7.4.1 Materials: use copper tubing for services 2" and smaller between main
and curb stop box and optional for services 2” and smaller between curb
stop box and building; use crosslinked polyethylene (PEXa) or
polyethylene (PE) pipe for services larger than 2" and optional for all
service sizes between curb stop box and building.
8. SUMP PUMP DRAIN LINES
8.1 Design sump drain lines in accordance with SUDAS Design Manual, Ordinances of
the City of Waukee, Iowa and the following standards:
8.2 Provide sump pump drain line for each building requiring foundation drainage.
8.2.1 Drain line standards herein are based on proper installation of a suitable,
commercially available automatic, thermal overload protected sump
pump capable of discharging 20 gpm at 20' TDH.
8.3 Outlet drain line in public collector pipe or storm sewer.
8.4 Collector pipes, receiving discharge of two or more sump pumps, may be used
upon written approval of installation details by City; minimum pipe size: 8".
8.5 Arrange sump pump drain lines and collector pipes to prevent freezing;
minimum depth of cover over buried pipe: 3'-6" or as approved by City.
8.6 Provide 4" pvc pipe with positive drainage for drain lines. Extend 4" drain line
from public storm sewer or collector pipe to minimum 1’ inside property line.
9. SUBDIVISION LOT GRADING AND MAINTENANCE
9.1 Construction sites covered by General Permit No. 2, issued by IDNR, are
required to fulfill the topsoil preservation requirement by either:
9.1.1 Stating that the requirements for on-site topsoil in SUDAS Standard
Specifications Section 2010 will be met OR using the General Permit
No. 2 language which states “The permittee shall minimize soil
compaction and, unless infeasible, preserve topsoil”.
9.2 Subdivider responsible for obtaining required borrow excavation and for disposal
of surplus excavated material.
9.3 Scarify slopes to a minimum depth of 3" prior to placement of topsoil.
Design Standards
2-13
9.4 Compact fill in areas intended to support utilities to not less than 95%
maximum density with moisture content between optimum moisture content
percentage and 4% above optimum unless otherwise directed by geotechnical
report; compact in horizontal layers not more than 8" in loose thickness.
9.5 Provide minimum 2% slope for buildable areas of residential lots and minimum
1.5% slope for buildable areas of commercial and industrial lots; no slope limit for
areas not disturbed by construction having slopes stabilized by existing vegetation
or rock outcropping.
9.6 Provide unobstructed 100-year flood flow paths through platted areas subject to
development to convey runoff from upstream areas of the watershed.
9.6.1 Compute runoff in accordance with Paragraph 4. STORM SEWERS.
9.6.2 Preserve or improve natural drainageways for use as flood flow paths.
9.6.3 Grade lots for drainage as shown on Standard Drawings or in accordance
with an agreed-upon plan with City.
9.6.4 All 100-year flood flow paths in rear and side yards shall be within a
surface water flowage easement. Provide subdrains, storm sewers and
flumes for low flow storm events in accordance with Paragraph 4.
STORM SEWERS.
9.7 Stabilize disturbed areas by sodding or seeding and mulching; maintain
undeveloped lots free of weeds.
9.8 Provide sediment and erosion control in areas subject to development in
accordance with IDNR General Permit No. 2.
9.8.1 Deposition of eroded soil on public rights-of-way, adjacent properties not
owned by subdivider and established streams, drainage ditches and
sewers is prohibited.
9.8.2 Remove sediment deposited by erosion, vehicle tire or otherwise on
public rights-of-way or adjacent properties by end of work day and
prior to a storm event.
Design Standards
2-14
10. STREET LIGHTS
10.1 All lighting within the Kettlestone corridor shown in Exhibit No. 2 following PART 11 –
KETTLESTONE STREET LIGHTS shall conform to the standards in the Kettlestone Design
Guidelines and PART 11 – KETTLESTONE STREET LIGHTS.
10.2 All lighting on private property including lighting for buildings, parking lots and private
streets shall conform to the City of Waukee Site Plan Ordinance.
10.3 All lighting on public streets shall conform to the design standards contained in the
SUDAS Design Manual and the following standards:
10.4 Poles:
10.4.1 All new street light poles and appurtenances installed within the clear zone
of any public street right-of-way shall be of a design to break-away when hit
by a vehicle. The break-away design shall conform to the definitions of the
U.S. Department of Transportation.
10.4.2 Street light poles shall be placed near all intersections, outside the sight
triangle, for proper lumination of the intersection.
10.4.3 Street light poles along minor collectors and local streets shall be spaced at a
maximum of 250 feet. Street light poles along major collectors and arterial
streets shall be spaced as approved by the City.
10.4.4 Locate poles in a straight line 3-feet to 6-feet behind the back of curb. Install
poles plumb.
10.5 Fixtures:
10.5.1 All fixtures shall be full cut-off (no sag lenz).
10.5.2 All fixtures shall be supported by MidAmerican Energy unless otherwise
approved by the City as a part of a development agreement related to
special development characteristics of a subdivision.
10.5.3 Mounting height shall be a minimum of 24.5 feet along minor collector and
local streets and a minimum of 30.5 feet along major collector and minor
and major arterial streets.
Design Standards
2-15
10.6 Provide photometric plan identifying all pole locations and project lighting levels with
foot-candle measurements at 10’ increments.
10.7 In cases where a homeowners association is created for a particular subdivision and
includes the responsibility of on-going maintenance of street light poles and fixtures, a
street lighting design utilizing unique poles and fixtures may be approved at the
discretion of the City.
11. TRAFFIC SIGNALS
11.1 All traffic signal installations must meet the criteria as set forth in the MUTCD for
minimum warrants to be met or be approved by the City following an engineering
study.
11.2 Meet SUDAS Specifications for traffic signals except as modified in PART 12 - TRAFFIC
SIGNALS.
11.3 Pedestrian crossings and ramp areas associated with a new traffic signal installation
shall comply with Americans with Disabilities Act (ADA) and Public Right of Way Access
Guidelines (PROWAG).
11.4 Traffic signal interconnection must be considered for any installation deemed
appropriate by the City. Interconnection methodologies and technologies must be
compatible with adjacent signal systems.
11.5 Placement of signal poles, cabinetry and pedestrian push buttons shall comply with
appropriate clear zone requirements for design speeds of the adjacent roadway as set
forth by AASHTO.
11.6 Traffic signal pole locations, traffic head placement and pedestrian crossings shall be
located to accommodate design vehicle turning movements throughout the
intersection.
11.7 All poles, footings and mast arms are to be designed to accommodate appropriate
structural loadings that are expected for this installation. Additional loadings shall be
considered for signage, aesthetic amenities, etc.
11.8 All components and appurtenances shall be made from materials to withstand the
elements and be protected by low maintenance coatings. These coatings shall meet
the standard colors for such installations as approved by the City.
Design Standards
2-16
11.9 All footings, cabinetry and handholes shall be placed to minimize the exposure to
drainage paths or conflict with other utility providers.
11.10 For any combination signal and street light installations, street light components shall
be as specified hereinbefore.
12. FIBER OPTIC LINES
12.1 Provide fiber optic lines on all minor collector streets and larger unless otherwise
directed.
12.2 Design fiber optic lines in accordance with the following standards:
12.2.1 Conduit: Comply with Iowa Department of Transportation Standard
Specifications Section 4189. 2” diameter, 30” depth.
12.2.2 Handholes: 30” x 48” x 24” precast polymer rated for 20,000 lb. load
(Tier 15). Handholes shall be installed at splicing, building access, and future
signal locations; 800’ maximum spacing.
13. STORMWATER MANAGEMENT
13.1 In 2024, the Iowa Legislature passed new regulations that limit how cities and counties
can enforce local stormwater post construction requirements. The City hereby
acknowledges the new Section 364.3(18) of the Code of Iowa relating to the
regulation of topsoil and storm water at construction sites and incorporates limits into
the Waukee Standard Specifications for Public Improvements for management of
stormwater.
13.2 The City hereby adopts the Iowa Stormwater Management Manual (ISWMM) and the
Waukee Standard Specifications for Public Improvements for management of
stormwater. The ISWMM is written as a guideline recommending certain techniques
and advising against others in order to accomplish goals related to managing water
volume and quality. Therefore, where the ISWMM states a design element or
technique is “essential” it is required by the City. Where ISWMM states a design
element or technique is “target” such design element or technique is desired by the
City and every effort shall be made to accomplish. Where ISWMM states a given
design element or technique is “advisory” this design element or technique shall not
be used within the City.
Design Standards
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13.3 In cases where ISWMM does not speak to a stormwater issue, such as sizing or
installation of pipes, the City follows the Iowa Statewide Urban Design and
Specifications (SUDAS), the Waukee Standard Specifications for Public Improvements
or the Iowa River Restoration Toolbox streambank stabilization guides as applicable.
13.4 All development and redevelopment projects shall meet the requirements described
in Section 364.3(18) of the Code of Iowa and/or the requirements of the Unified
Sizing Criteria, as described within the Iowa Stormwater Management Manual
(ISWMM), as noted below, unless stormwater management has been designated for
an alternative off-site location or an existing downstream conveyance capacity
requires additional management to ensure no adverse impacts to existing facilities.
13.4.1 Water Quality Volume Standard: Practices or techniques shall be employed
that capture and treat runoff from a 1.25” rainfall event, as further defined
within the ISWMM and as required per the current City MS4 permit.
13.4.2 Channel Protection Standard: Practices or techniques shall be employed
that provide extended detention of the 1-year, 24-hour storm event – with
release rates established as per methods defined within the ISWMM to
provide a minimum drawdown period of 24 hours.
13.4.3 Detention Standard: Practices and techniques shall be employed that limit
the allowable peak release rates that are anticipated to occur post-
development during the 5-, 10-, 25-, 50-, and 100-year, 24-hour storm events
to a level no greater than those expected to occur from the pre-developed
(existing condition) 5-year storm event. (e.g. the post-development release
rate from a 5-year storm event will be no greater than the existing condition
release rate from a 5-year storm event as well as the post-development
release rate from a 100-year storm event will be no greater than the existing
condition release rate from a 5-year storm event).
13.4.3.1 Alternative Detention Standard: Practices and techniques shall
be employed that limit allowable peak release rates that are
anticipated to occur post-development during the 2-, 5-, 10-,
25-, 50-, and 100-year, 24-hour storm events to levels no
greater than those expected to occur from natural conditions
a given site from a similar storm event (e.g. the post-
development release rate from a 5-year storm event will be
no greater than the natural release rate from a 5-year storm
event).
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13.4.3.1.1 Natural conditions are defined as meadow in good condition,
with times of concentrations calculated and Curve Numbers
selected based on those natural surface conditions and
drainage patterns. Curve Numbers shall be selected based on
the Hydrologic Soil Group for site soils, but the weighted
Curve Number used to determine allowable release rates for
the site to be served by the detention practice shall not
exceed a Curve Number of 58 unless demonstrated by a
geotechnical report that a higher curve number is warranted,
however, in no case shall the curve number exceed 71.
13.4.4 Detention of events larger than the 100-year storm event are not required,
however, the design of auxiliary spillways should safely convey flows from
the 500-year, 24-hour storm event.
13.4.5 Detention of off-site stormwater runoff is not required, however, the design
of the outlet structure and auxiliary spillways shall safely convey off-site
flows through the proposed development with no adverse impacts to
adjacent properties.
13.4.6 Surface water flowage easements shall be provided as needed to reserve a
safe and clear path for the width of expected concentrated flows for the
100-year storm event. Detention events larger than the 100-year can occur
and surface water conveyance for those events should be considered.
13.4.7 Detention basins shall be sized using the TR-55 Method or approved
equivalent.
13.4.8 Soil Group information shall be determined from current County Soil maps
as available through the NRCS. If a Soil Group type has not been identified
for a given location, the natural condition shall be assumed to be
Hydrologic Soil Group B and the post-developed condition shall be assumed
to be Hydrologic Soil Group C, unless geotechnical studies are provided for
City review that provide evidence for use of another Soil Group for analysis.
13.4.9 Restrict discharge rate from detention basins using a correctly sized
aluminum or stainless-steel weir plate or orifice plate securely fastened with
stainless steel hardware. Fasten orifice plate inside downstream pipe or
structure. Pipe downstream from weir plate or orifice plate to have
adequate capacity to accommodate a minimum of a 10-year storm
frequency event. The minimum orifice size to be used is 3” diameter
regardless of the calculated allowable release rate for a given storm event.
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13.4.10 Meet ISWMM requirements for the design of best management practices;
including, but not limited to: sizing, slopes, embankment widths, freeboard,
high water depths and auxiliary spillway.
13.5 Applicability:
13.5.1 New Development: Any new development of land adding more than
10,000 square feet of new impervious surface shall provide stormwater
management as outlined above. This includes the entirety of any existing
public right-of-way within new development and the development half of
any existing public right-of-way adjacent to new development. This
threshold is a cumulative amount of new square footage and may be
reached over time in increments. At such time that a development site
exceeds 10,000 cumulative square feet of new impervious surface the site
will be required to come into compliance with this chapter. This includes
linear roadway projects that are a part of a new development.
13.5.2 Redevelopment: Any redevelopment of land adding more than 10,000
square feet of new impervious surface but disturbing less than 50% of the
site shall provide stormwater management at the Water Quality Volume
standard and shall be asked to also meet the Channel Protection standard
or demonstrate why doing so is infeasible. This standard is in addition to
remaining in compliance with detention proposed for larger storm events
in any previously approved stormwater management plan. This threshold
is a cumulative amount of new square footage and disturbance and may be
reached over time in increments. At such time that a site exceeds 10,000
cumulative square feet of new impervious surface, the entire site will be
required to come into compliance with this section. Any redevelopment
disturbing 50% or more of a site shall be required to meet the same
stormwater management standards as a new development per section
13.5.1. At such time that 50% or more of a site is cumulatively disturbed,
the entire site will be required to come into compliance with section
13.5.1.
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13.5.3 New Development or Redevelopment with Existing Regional Detention:
Any new development or redevelopment adding more than 10,000 square
feet of new impervious surface or any redevelopment disturbing 50% or
more of a site with existing regional detention shall provide stormwater
management at the Water Quality Volume standard and shall be asked to
also meet the Channel Protection standard in addition to the regional
detention provided or demonstrate why doing so is infeasible. This
standard is in addition to remaining in compliance with the regional
detention proposed for larger storm events in the previously approved
regional detention stormwater management plan. This threshold is a
cumulative amount of new square footage and disturbance and may be
reached over time in increments. At such time that a development site
exceeds 10,000 cumulative square feet of new impervious surface or 50%
or more of a site is cumulatively disturbed, the entire site will be required
to come into compliance with this section.
13.5.4 City Projects: Stormwater management standards shall apply to all City
projects including new City parks and buildings.
13.5.5 Exemptions: The following activities shall be exempted from meeting the
stormwater management standards of this ordinance:
13.5.5.1 New development adding less than 10,000 square feet of new
impervious surface.
13.5.5.2 Redevelopment adding less than 10,000 square feet of new
impervious surface and less than 50% site disturbance and if in
compliance with a previously approved stormwater
management plan.
13.5.5.3 Removal and replacement of impervious surface exactly
matching location and area.
13.5.5.4 Logging or agricultural activity that is consistent with an
approved soil conservation plan or timber management plan
prepared or approved by the appropriate agency, as
applicable.
13.5.5.5 Additions or modifications to single family structures.
13.5.5.6 Repairs to any stormwater management BMP deemed
necessary by the city.
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13.5.5.7 Linear road construction projects where stormwater detention
is impractical. This does not include linear roadway projects
that are a part of a new development.
13.6 All development or redevelopment projects shall begin with a pre-application
meeting with the City Development Services and Public Works staff. At said
meeting, City staff will discuss the proposed project with the developer or developer
representatives and will review preliminary information regarding stormwater
management as indicated on the City’s Stormwater Management Plan Review
Checklist.
13.7 The City will maintain a checklist of required plans and studies and timing for
submittal which may include, but not be limited to:
13.7.1 Post-Construction Stormwater Management Plan consistent with City
requirements outlined in the City Post-Construction Stormwater
Management Plan Review Checklist in section 13.12 to follow.
13.7.2 Natural Resources Inventory as outlined in section 13.12.2.1.8 to follow.
13.7.3 Soil Management Plan as outlined in section 13.12.2.2 to follow.
13.8 The site shall be designed using Better Site Design principals. Better Site Design
involves techniques applied early in the process to preserve natural areas, reduce
impervious cover, distribute runoff and use pervious areas to more effectively treat
stormwater runoff. Site design should address open space protection, impervious
cover minimization, and runoff distribution and minimization, and runoff utilization
through considerations such as:
13.8.1 Open space protection and restoration:
13.8.1.1 Conservation of existing natural areas (upland and wetland).
13.8.1.2 Reforestation.
13.8.1.3 Re-establishment of prairies.
13.8.1.4 Restoration of wetlands.
13.8.1.5 Establishment or protection of stream, shoreline and wetland
buffers.
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13.8.1.6 Re-establishment of native vegetation into the landscape.
13.8.2 Reduction of impervious cover:
13.8.2.1 Reduce new impervious through redevelopment of existing
sites and use of existing roadways, trails etc.
13.8.2.2 Minimize street width, parking space size, driveway length,
sidewalk width.
13.8.2.3 Reduce impervious surface footprint (e.g. two-story buildings,
parking ramp).
13.8.3 Distribution and minimization of runoff:
13.8.3.1 Utilize vegetated areas for stormwater treatment (e.g. parking
lot islands, vegetated areas along property boundaries, front
and rear yards, building landscaping).
13.8.3.2 Direct impervious surface runoff to vegetated areas or to
designed treatment areas (roofs, parking, driveways drain to
pervious areas, not directly to storm sewer or other
conveyances).
13.8.3.3 Encourage infiltration and soil storage of runoff through grass
channels, soil compost amendment, vegetated swales,
raingardens, etc.
13.8.3.4 Plant vegetation that does not require irrigation beyond
natural rainfall and runoff from the site.
13.8.4 Runoff utilization:
13.8.4.1 Capture and store runoff for irrigation in areas where
irrigation is necessary.
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13.9 It is intended that this section is construed to be consistent with City Ordinance
Chapters 165-169 Zoning Regulations, Chapters 175-179 Subdivision Regulations,
Chapter 102 Construction Site Erosion and Sediment Control (COSESCO), Chapter
103 Post Construction Storm Water Management, Chapter 101 Illicit Discharge to
Storm Sewer System, Chapter 170 Floodplain Management, as well as any other
applicable local, state or federal regulations.
13.10 The requirements of this chapter should be considered minimum requirements, and
where any provision of this chapter imposes restrictions different from those
imposed by any other chapter, rule or regulation, or other provision of law,
whichever provisions are more restrictive shall take precedence.
13.11 The purpose of a Stormwater Management Plan is to identify in detail how
stormwater runoff will be managed from a site including specifications on what
stormwater management techniques and facilities will be used and where they will
be located. It is the policy of the City that stormwater management is planned and
designed early in the development process so that developments are built in
harmony with nature versus forcing stormwater management to fit a development
site design. Therefore, certain items will be discussed at the time of a pre-
application meeting with City staff so that they can be considered before detailed
engineering site design has occurred.
13.11.1 The following are items to be discussed or submitted at the pre-application
phase. Items in the pre-application phase need not be final reports or
engineering studies nor is that the intent. A designer should consider these
items at the start of the design process and should discuss them with City
staff. Examples of the items in this section are as follows:
13.11.1.1 Natural Resources Inventory – written and/or maps.
13.11.1.2 Soil Management Plan.
13.11.1.3 Map(s) showing existing and proposed conditions.
13.11.1.4 Be prepared to discuss Better Site Design Principles being
incorporated into the site plan.
13.11.2 Items to be submitted with site plan/plat/grading plan submittals:
13.11.2.1 Report and Narrative Information.
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13.11.2.2 Cover sheet including project name, location, engineer and
developer contact information.
13.11.2.3 Table of contents indicating sections and page numbers.
13.11.2.4 Professional certification from Iowa Licensed Engineer.
13.11.2.5 Summary of any previous studies or master plans.
13.11.2.6 Natural Conditions and runoff analysis summary.
13.11.2.7 Description and explanation of storm water analysis (e.g.
computer-generated hydrographs).
13.11.2.8 Summary of stormwater management plan detailing
compliance with design standards.
13.11.2.9 Natural Resources Inventory:
13.11.2.9.1 Soil conditions (karst, hydric, etc.).
13.11.2.9.2 Forest cover.
13.11.2.9.3 Topography.
13.11.2.9.4 Wetlands/Prairie Potholes.
13.11.2.9.5 Streams and floodplains.
13.11.2.9.6 Review of FEMA FIRM maps.
13.11.2.9.7 Other Native Vegetative Areas.
13.11.2.9.8 Environmentally Sensitive Areas.
13.11.2.9.9 Archeological and/or cultural resources.
13.11.2.9.10 Wildlife areas
13.11.2.9.11 Wellhead protection and drinking water supply
management areas.
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13.11.2.9.12 Areas of existing stormwater storage.
13.11.2.10 Soil Management Plan. The intent of a Soil Management Plan
is simply to demonstrate what is to be done with soil on site.
Where will it be stockpiled and eventually spread and used on
site. Depending on intended use of soil to meet stormwater
requirements, the following items may be applicable:
13.11.2.10.1 Review NRCS or USGS soils maps or geotechnical
reports.
13.11.2.10.2 Avoid disturbance of higher quality soils to
maximum extent possible.
13.11.2.10.3 Avoid disturbance activities under the drip line
of any trees intended to be preserved.
13.11.2.10.4 Identify where topsoil is to be stripped,
stockpiled and replaced.
13.11.2.10.5 Identify locations where Soil Quality Restoration
techniques are proposed to be used to manage
water quality treatment requirements.
13.11.2.11 Summary of how Better Site Design Principles, if applicable,
have been incorporated into site design.
13.11.2.12 Geotechnical report.
13.11.2.13 US Army Corps of Engineers Section 404 Permit, if applicable.
13.11.2.14 Local or DNR Floodplain Development Permit, if applicable.
13.11.3 Calculations – for each calculation, provide exhibits demonstrating how
calculated and assumptions made:
13.11.3.1 Runoff coefficient and/or curve number calculations
(allowable release rates).
13.11.3.2 Time of concentration calculations.
13.11.3.3 Water volume infiltrated.
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13.11.3.4 Water Quality Volume calculations required and proposed.
13.11.3.5 Channel Protection Volume calculations required and
proposed (if applicable).
13.11.3.6 Large storm (100 year) calculations detention volume required
and proposed.
13.11.3.7 Storm system capacity calculations (outlet control, pipe
capacity, swale/ditch capacity, erosion control and emergency
dissipation measures, downstream capacity calculations).
13.11.3.8 Runoff and routing hydrographs.
13.11.3.9 Floodplain modeling if applicable and base flood elevations.
13.12 Project Summary:
13.12.1 Identify method(s) and location of proposed post-construction
stormwater management BMPs.
13.12.2 Map indicating drainage area of each post-construction BMP.
13.12.3 Discuss how proposed management methods comply with requirements.
13.12.4 Post-construction BMP maintenance plan.
13.12.5 Operation and maintenance of post-construction BMPs.
13.12.6 Identify post development stormwater impacts to adjacent properties and
mitigation measures for any potential impacts.
13.12.7 Offsite / downstream conditions and runoff analysis if applicable.
13.13 Maps:
13.13.1 Existing drainage contour map illustrating and labeling pre-development
drainage patterns, basins, swales/ditches, creeks, river, streams, etc. and
any other relevant on-site or off-site information.
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13.13.2 Proposed drainage contour map illustrating and labeling post
development drainage patterns, areas for which storm water
management will be provided, conveyance methods (pipes, swales, etc.)
and any other relevant on-site or off-site information.
13.13.3 Location of existing and proposed buildings, roads, parking areas, utilities
and stormwater management facilities and erosion/sediment control,
easements, ROWs.
13.13.4 Preliminary stormwater storage estimation.
13.13.5 Proposed land use.
13.13.6 Existing and proposed drainage patterns.
13.13.7 Limits of clearing and grading.
13.13.8 Map(s) identifying where stormwater runoff enters and leaves the project
limits.
13.13.9 Watershed area delineations.
13.13.10 Floodplain delineations.
13.13.11 Natural Resources Inventory Map.