HomeMy WebLinkAboutA031 - Hearing on Text Amendments to Chapter 23 Conservation Subdivision OrdinanceITEM #:33
DATE:01-14-25
DEPT:P&H
SUBJECT:TEXT AMENDMENTS TO CHAPTER 23 CONSERVATION SUBDIVISION
ORDINANCE
COUNCIL ACTION FORM
BACKGROUND:
On November 12, 2024, the Ames City Council initiated a text amendment to the City's Conservation
Subdivision standards, which apply to new residential subdivision development in the Ada Hayden
Watershed north of Bloomington Road (see attached map). Council took action after extensive review,
including input from development interests, the Friends of Ada Hayden, and the results of a study
investigating the potential amendments to development standards and their potential effect on the Ada
Hayden Lake.
Council directed staff to: 1) eliminate from the Conservation Subdivision standards the
requirement for 80% of lots to abut open space, and 2) reduce the required open space set aside
to 10% from 25%. As a result of these changes, the ordinance was to be modified to establish an
expectation of integrated conservation areas and open spaces within the development, without the
mandatory percent set-asides, and to focus on enhanced water quality Best Management Practice
(BMP) requirements to offset potential impacts of increased development. The ordinance changes also
incorporate other issues raised by the AEDC Short Term Housing Taskforce regarding jurisdictional
wetlands, street lengths and design, mass grading, and useable open space.
The proposed ordinance includes amendments to Chapter 23, Subdivisions, which contains the
Conservation Subdivision standards. A forthcoming ordinance will also include amendments to the
Chapter 29 Floating Suburban Development Standard (Table 29.1202(6)) related to block lengths and
mid-block connections to align with the intent of Council's changes to the Subdivision Code.
PROPOSED ORDINANCE:
With the significant changes to the standards, the overall ordinance standards have been mostly
rewritten. The title of the ordinance has also been modified to Low Impact Development and
Conservation Subdivision Ordinance to reflect the type of features expected within subdivisions that
differ from a traditional conservation subdivision approach. All subdivisions will need to incorporate
these features to achieve the stated requirements without stating minimum open space and conservation
area percentages.
The proposed ordinance includes updated requirement sections focused on conservation set-asides,
conservation and open space design, residential lot layout, connectivity for roads and trails, and
stormwater treatment measures. Below are highlights of the changes. The full draft ordinance is
attached.
Elimination of the 80% of Lots Abutting Open Space Requirement and Reduction of the Open
Space Set-Aside to 10% from 25%
The original intent of the 80% requirement was to promote interconnected greenways and
environmental corridors. It also intended to create a certain character in Conservation Subdivisions, as
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lots appeared larger if they abutted conservation areas. In reality this did not occur as small strips of
open spaces were commonly kept adjacent to standard lot sizes. The conservation subdivision ordinance
also intended to create at least 25% open space in subdivisions, which was to be interconnected and
include conservation areas containing natural resources identified through a site inventory. These areas
were also meant for stormwater conveyance and treatment.
With the elimination of the 25% open space standard, the FS-RL and FS-RM base zone
requirement that 10% of a subdivision be dedicated as common open space will continue to apply.
Existing provisions for inventorying natural features and protecting conservation areas will be
maintained without the numeric minimum of 25%. A new provision to incorporate open spaces, without
a set-aside percentage, throughout a subdivision and provide connectivity to conservation areas is
introduced in place of the requirement that all conservation areas must connect.
The resource inventory process was also amended to clarify that the areas identified in the Natural
Resources Inventory to be included as Conservation Areas must be acceptable to the Public Works
Director and submitted with the first application submitted to the City.
Stormwater Best Management Practices
The consultant’s study identified specific stormwater BMPs and combinations of measures that should
be priorities related to Ada Hayden’s water quality. Through the amendments, the stormwater
management plans for developments would be required to demonstrate in-series BMPs that address
nitrogen, phosphorous, E. Coli, and Total Suspended Solids (TSS). Use of these practices in a series,
known as a treatment train, is recommended as different practices have different efficacy levels and
may be better at targeting a certain pollutant. Relying on multiple practices also eliminates the
uncertainty of if a single practice is achieving the desired pollutant reductions due to ongoing
maintenance.
Staff proposes adding the following additional standards regarding stormwater treatment techniques:
Select a variety of targeted stormwater management best practices and facilities to use in a series
to reduce off-site discharge of pollutants including Total Suspended Solids (TSS), phosphorous,
nitrogen, E. coli, and metals. A singular stormwater treatment measure of a detention pond will
not meet this standard.
Provide pre-treatment for stormwater runoff through practices such as swales, bioretention cells,
and vegetative buffers. Forebays may be required.
Include a total pollution reduction summary table for Total Suspended Solids (TSS),
phosphorous, nitrogen, E. coli, and metals showing reductions achieved for review by the Public
Works Director.
The consultant also identified that one of the peak times for pollution is during construction when
grading work is occurring and soils are exposed. This can lead to erosion and sedimentation. To address
this issue, staff has added a requirement for the use of sediment basins until final site stabilization for
extended times of buildout. This will be a component of a stormwater management plan approval.
Wetland protections:
Staff notes that while the current ordinance refers to wetlands in general, in practice the protections
were only applied to jurisdictional wetlands. Jurisdictional wetlands are those that have a continuous
surface connection to Waters of the United States (WOTUS). WOTUS are under the jurisdiction of the
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U.S. Army Corps of Engineers (USACE) and require permits from the USACE for activities such as
filling and dredging or discharging pollutants. Some wetlands, such as prairie potholes, may not have a
connection to WOTUS and are not considered jurisdictional. The ordinance requires retention of actual
jurisdictional wetlands; a fill permit eliminating the wetland is not allowed even if issued by the
USACE. It will be rare for a jurisdictional wetland to be part of a project, but it will be based upon
determination by the USACE.
The proposed ordinance clarifies that only jurisdiction wetlands are required to be located in
conservation areas. It also introduces a buffer requirement that must be provided around the wetland
depending on its size and quality. Other wetlands are encouraged to be retained but are not required as
a mandatory conservation area.
Variations to street lengths and more cul-de-sacs/dead ends to minimize impacts to natural
resources and reduce impervious area
The City’s Subdivision Design and Improvement standards require that all subdivisions:
Minimize overall lengths of public ways and infrastructure facilities while limiting the use of
dead-end streets and cul-de-sacs
Achieve a preferred block length that does not exceed 600 feet and in no case be longer than
1,320 feet or shorter than 280 feet between center lines of public ways unless topography or other
conditions justify variation
These requirements may be in conflict with Conservation Subdivision standards for open space and
natural resource preservation. A clustered design for residential lots may better preserve resources and
ensure a high percentage of lots abut open space. This design may be better accomplished through the
use of cul-de-sacs or other limited connectivity streets.
An allowance for the use of limited connectivity street networks such as loop streets and cul-de-sacs is
proposed in order to reduce impervious areas and create larger conservation areas. Pedestrian
connections are required at the end of dead-ends to maintain connectivity. The prior ordinance
required a trail network within each subdivision, the proposed language would reduce that expectation
to focus on access and connectivity.
The original ordinance suggested sidewalks would not be necessarily required on both sides of a street.
This allowance has now been changed to be only for a short block with no more than four houses on the
block face without a sidewalk and that the houses have direct access to a trail.
Mass Grading Limitations
The current ordinance states that “mass grading of sites shall be minimized in order to preserve the
natural features of the site.” This requirement was unclear if mass grading was allowed site-wide and
what level of disturbance was considered mass grading (e.g. a certain size of area disturbed or a certain
amount of cut and fill work). Staff has drafted several amendments to the ordinance to clarify this
provision.
First, grading and other disturbance of natural resources contained in conservation areas is not
permitted unless allowed by the Public Works Director for restoration of a feature or for essential
infrastructure. All conservation areas shall be minimally disturbed. This clarifies the priority for
minimizing mass grading and the retention of existing soils in these areas.
Grading is permitted on other portions of the site; however, staff proposes amendments to help clarify
how grading can be minimized and to limit erosion when grading does occur. New provisions to site
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lots and roadways to work with existing topography are introduced. This demonstrates an intent to fit a
development to the site, but it does not outright prohibit grading.
Usable Open Space Requirements
The FS-RL and FS-RM base zones require that 10% of a subdivision be dedicated as common open
space. This space is to be available for passive or active recreation. In Conservation Subdivisions, that
means that if over 10% of a subdivision is common open space, only 10% must be usable. Usable open
space is defined within the Zoning Ordinance.
Staff has added the following standard for conservation areas to clarify this issue since the original
ordinance seemed to require that all conservation areas be available as open space:
Conservation areas are not required to serve as passive or active recreation areas in
addition to the required percentage of common open space to be set-aside by Zoning
Ordinance standards.
Other Amendments
Clarified applicability that Conservation Subdivision standards may apply to other areas outside
of the Ada Hayden Watershed at the discretion of City Council, including those areas within the
City’s two-mile extraterritorial review area for subdivisions. Additionally, the standards may also
apply to commercial development lots within a subdivision.
Clarified trees are not required to be individually inventoried if part of a larger wooded area to be
protected. Additionally, staff reduced the caliper size of trees required to be inventoried to 12
inches measured four feet off the ground from 24 inches. A 24-inch caliper size tree is very large
—significant trees typically may be as small as a 12-inch caliper.
Added a provision that residential lots shall not contain large stormwater flowage easements. This
is not typically permitted in subdivisions due to maintenance and encroachment issues. Given
enhanced stormwater management requirements, staff felt it necessary to introduce this
requirement and see these types of features as common open space meeting the intent of the
ordinance.
Landscaping design and vegetation will primarily utilize native plants and trees.
PUBLIC OUTREACH:
The amendment language was shared with the general development interest group email list and the two
developers involved with projects in the watershed and the Friends of Ada Hayden prior to the Planning
and Zoning Commission meeting. Development representatives provided no additional comments.
Representatives of Auburn Trail again indicated they were supportive of the changes. Staff met with a
representative of the Friends of Ada Hayden and they were also still receptive to the amendments.
PLANNING AND ZONING COMMISSION RECOMMENDATION:
The Planning and Zoning Commission reviewed the proposed amendment at its December 18, 2024,
meeting. The Commission's discussion focused on the impacts of the changes to Ada Hayden Lake.
One Commissioner asked for more information on how Ada Hayden Lake serves as the City's
emergency water supply. Staff clarified that water from Ada Hayden was not directly used as a water
supply in case of drought, but rather able to be used to replenish South Skunk River levels that then
recharge the aquifer where the City's wells are located.
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The Commission asked for assurance that the consultant found the changes to the ordinance would be
offset by enhanced stormwater management practices. Staff stated that individual stormwater practices
for water quality could attain up to an 80% reduction in Total Suspended Solids. When multiple
practices are used in a series, reductions would be anticipated to be greater. While a treatment train
approach is not common in existing residential subdivisions, the use of swales, part of a treatment train
approach, is and staff believes that they are relatively effective and easy to maintain.
Staff also noted that the existing stormwater management ordinance in Chapter 5B ensures runoff rates
post-development do not exceed pre-development site conditions. In terms of general maintenance,
stormwater practices for residential subdivisions are maintained by a homeowners or other association.
The City would use stormwater funds for long-term maintenance for capacity issues such as dredging of
basins that are beyond general maintenance obligations. Chapter 5B also includes enforcement
mechanisms for maintenance and other issues.
The Commission also asked if increased open space would be required for Low Impact Development
and enhanced stormwater management BMPs. Staff stated that the developments impacted by the
amendments are already incorporating these practices. With increases in the number of lots, additional
volume for detention may be required, but it would not significantly offset increased development
intensities possible through the amendments. If the acreage of natural resources on a site exceeded the
common open space requirement of the base zoning, additional land would be required beyond the
minimum to be set aside in a conservation area to preserve all resources.
No members of the public spoke at the meeting. The Commission voted (5-0) to recommend the City
Council amend the Conservation Subdivision standards as recommended by the City staff.
ALTERNATIVES:
1. Approve the first reading of an ordinance amending the Conservation Subdivision Standards of
Chapter 23 of the Ames Municipal Code as shown in the attached ordinance.
2. Approve the first reading of an ordinance with modified language suggested by the City Council.
3. Do not approve the proposed text amendment.
4. Request additional information from staff.
CITY MANAGER'S RECOMMENDED ACTION:
The Conservation Subdivision standards were adopted in 2010 to protect Ada Hayden's water
quality prior to the City's adoption of the current stormwater management requirements. In
2014, the City introduced specific numeric water quality standards for developments meeting
certain thresholds. These standards now apply to Conservation Subdivisions in addition to
Conservation Subdivision standards.
The two main changes to the ordinance remove numeric requirements related to open space (total
percentage set aside and percentage of adjacent lots) while preserving the intent of the standards for
natural resource preservation and connectivity of conservation areas with residential lots. The
amendments also include enhanced stormwater management practices recommended by the consultant
to offset any impacts of more intense development on the Ada Hayden Watershed.
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Similarly, while more flexibility in standards regarding roadway design, mass grading, and wetlands is
proposed through the amendments; staff has also proposed amendments that ensure this flexibility is not
at odds with resource protection by guiding development to be designed around natural topography and
drainage patterns.
Staff believes appropriately designed development following the proposed standards of the
amended ordinance will provide water quality benefits in terms of reducing pollutant loads and
resource preservation compared to current unmitigated farmland conditions of the future
development sites in the Ada Hayden Watershed. The outcome of these changes will likely result
in modest development intensity gains for lot layout and focus the design on retaining the highest
value conservation and open spaces areas as part of the subdivision design. Therefore, it is the
recommendation of the City Manager to adopt Alternative #1.
ATTACHMENT(S):
Watershed Map.pdf
Ordinance Conservation Subdivisions.pdf
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ORDINANCE NO.________
AN ORDINANCE TO AMEND THE MUNICIPAL CODE OF THE
CITY OF AMES, IOWA, BY AMENDING AND RENUMBERING
SECTIONS 23.201, 23.600, 23.601, 23.602, 23.603, 23.604, 23.604,
AND 23.605 THEREOF, FOR THE PURPOSE OF AMENDING
CONSERVATION SUBDIVISION STANDARDS, REPEALING
ANY AND ALL ORDINANCES OR PARTS OF ORDINANCES IN
CONFLICT TO THE EXTENT OF SUCH CONFLICT; AND
ESTABLISHING AN EFFECTIVE DATE.
BE IT ENACTED, by the City Council for the City of Ames, Iowa, that:
Section One. The Municipal Code of the City of Ames, Iowa shall be and the same is hereby
amended by amending and renumbering Sections 23.201, 23.600, 23.601, 23.602, 23.603, 23.604, 23.604,
and 23.605 follows:
“DIVISION II
DEFINITIONS AND RULES OF CONSTRUCTION
Sec. 23.201. DEFINITIONS.
. . .
(7) BMPs: Best Management Practices. Those practices most appropriate for land management. A practice
or series of practices used to manage stormwater in accordance with City stormwater requirements in Chapter
5B Post Construction Stormwater Management Ordinance.
. . .
(19) Conservation Subdivision: A housing development which is characterized by compact and cluster lots
designed around environmentally sensitive areas and dedication of environmentally sensitive areas as
conservation areas to preserve and enhance natural features and dedicated conservation areas where the
natural and/or restored features of the land are maintained.
. . .
(36) Low Impact Development: an approach to stormwater management that attempts to mimic pre-
development conditions by compensating for losses of rainfall abstraction through infiltration,
evapotranspiration, surface storage, and increased travel time to reduce excess runoff.
. . .
(53) Stormwater Treatment Train: A combination of stormwater management practices that are constructed
or planted to convey, cleanse, and enhance stormwater quality and address quantity to manage the rate of
stormwater before the remaining water is discharged to receiving waters.
…
DIVISION VI
LOW IMPACT DEVELOPMENT AND CONSERVATION SUBDIVISIONS
23.600. CONSERVATION DEVELOPMENT FOR SUBDIVISIONS
23.6001. APPLICABILITY. Low Impact and Conservation Subdivisions are alternative sets of design
objectives and standards primarily for single-family residential subdivisions development. These objectives
and standards can be used as an alternative to common residential subdivision development patterns in Ames.
However, they shall apply, at least in part, to all residential subdivision development in the undeveloped
areas of Ada Hayden Watershed north of Bloomington Road. City Council may also require conformance to
this Section when there are unique environmental protection priorities for a site or area.
23.6012. INTENT. The intent of these standards for Low Impact and Conservation Subdivisions is to
preserve the existing natural features of the site, to preserve the natural drainage features and hydrologic
characteristics of the landscape, and to reduce the impacts of development on the landscape; and
(1) To maintain and protect in perpetuity Ames area natural character by preserving these important
landscape elements including but not limited to those areas containing unique and environmentally
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sensitive natural features as prairie, woodlands, stream buffers and corridors, drainageways,
wetlands, floodplains, ridgetops, steep slopes, critical species habitat, and by setting them aside from
development;
(2) To promote interconnected greenways and environmental corridors throughout Ames;
(3) To provide commonly-owned open space and conservation areas for passive and/or active
recreational use by residents of the development and, where specified, the larger community;
(4) To permit various means for owning conservation areas, preserved landscape elements, and to
protect such areas from development in perpetuity;
(5) To provide greater flexibility in site dwellings and other development features than would be
permitted by the application of standard use regulations in order to minimize the disturbance of
natural landscape elements and sensitive areas, scenic quality, and overall aesthetic value of the
landscape;
(6) To protect and restore environmentally sensitive areas and biological diversity, by minimizing
disturbance to existing soils, vegetation, and maintaining environmental corridors; and
(7) To preserve significant archaeological sites, historic buildings and their settings.; and
(8) To provide enhanced stormwater management to prevent and minimize the release of pollutants
of concern from stormwater runoff within the Ada Hayden Watershed.
23.602 APPLICATION PROCEDURE.
In addition to the standard subdivision application requirements, all applications shall include a complete
inventory and mapping of natural resources as described herein.
(1) Inventory and Mapping of Natural Resources. An inventory of natural resources of the proposed
development site shall be conducted by experts in the field such as biologists, ecologists, soil
scientists, hydrologists, geologists or those credentialed in a manner acceptable to the City. The
inventory must include, but is not limited to, the following information mapped at a scale of no less
than one-inch equals 50 feet and with topographic contours at 2-foot intervals.
(a) United States Department of Agriculture-Natural Resource Conservation Service soil
type locations and identification of soil type characteristics such as percolation rates,
suitability for infiltration-based stormwater management practices, hydric soils, depth to
water table, and suitability for wastewater disposal systems if applicable.
(b) Hydrologic characteristics, including surface water bodies, floodplains, groundwater
recharge and discharge areas, wetlands, natural swales, drainage ways, and slopes 10% or
greater.
(c) Land cover on the site including, but not limited to, prairie, woodland, forest, wetland
with its general cover type (pasture, woodland, etc.), and stand-alone trees with a caliper
of more than 12 inches measured four feet off the ground. The inventory shall include
comments on the health and condition of the natural resources.
(d) Known critical habitat areas for rare, threatened or endangered species using existing
documented inventories.
(e) Cultural resources shall be identified by a brief description of historic character of
buildings and structures, historically important landscapes, and archeological features
using a review of existing, documented inventories.
23.603. GENERAL REQUIREMENTS.
All subdivisions shall incorporate open spaces and conservation areas to provide dispersed and
connected conservation areas with a natural setting for conserving natural resources and providing
stormwater management that meet requirements outlined below.
(1) Design and Standards for Residential Lot Layout. Conservation Area Set-Asides
(a) The subdivision layout shall include conservation areas that incorporate site features
identified in the natural resources inventory required by Section 23.602 that, as native
species in good condition, have particular preservation or restoration value. These
conservation areas shall be evaluated for acceptability by the Public Works Director.
At a minimum, the following features and defined buffers must be included in conservation
areas:
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(i) All jurisdictional wetlands, floodways, and/or identified wildlife habitat areas.
Non-jurisdictional wetlands are encouraged to be retained.
(ii) A 25-foot landscape buffer around the perimeter of a subdivision adjacent to
major roadways. Walkways, other incidental encroachments, and variations of
buffer depth are permitted, provided that they meet the intent of this Division. The
buffer shall be established with and maintained with natural vegetation utilizing
native plants.
(iii) Natural Feature Buffers. The following features as identified in the natural
resources inventory Section 23.602 and their required buffer measures. Buffer
area widths may be reduced when restoration activities or enhancements to the
area are included with the subdivision design and approved by the Public Works
Director.
(1) Open water areas - A 50-foot native vegetative buffer shall be
maintained around open water areas such as ponds and lakes unless a
specific common use area is identified.
(2) Stream buffers with native vegetation shall be maintained along
stream areas using the following requirements based on stream order,
with the final classification by the Public Works Director:
(a) Streams exceeding third (3rd) order and above, the City
requires sketches, maps, studies, engineering reports, tests,
profiles, cross-sections, construction plans and specifications to
determine adequate buffer widths.
(b) Perennial streams (1st and 2nd order). The total required
stream buffer width is one hundred (100) feet on each side
perpendicular to the waterway measured from the outer wet
edge of the channel during base flows.
(c) Intermittent streams. The total required stream buffer width
is fifty (50) feet on each side perpendicular to the water way
measured from the centerline of the channel.
(d) Waterways and/or dry channels that have a contributing
drainage area of fifty (50) acres or greater. The total required
stream buffer width is thirty (30) feet on each side perpendicular
to the waterway measured from the centerline of the waterway.
(e) Waterways and/or dry channels with a contributing drainage
area of less than 50 acres. The total required stream buffer
width is twenty (20) feet on each side perpendicular to the
waterway measured from the centerline of the waterway.
(3) Jurisdictional wetlands shall also be provided with a buffer
appropriately sized based on size and quality of habitat and diversity of
plant and animal communities. The buffer size shall be acceptable to the
Public Works Director.
(2) Conservation Area Design.
(a) Conservation area design shall promote minimal disturbance and include
primarily native vegetation and landscaping in accordance with Section
23.603(5). Features identified by the natural resources inventory Section 23.602
and located in Conservation Areas shall be maintained in their natural condition
or an enhanced condition.
(b) Access easements sufficient for maintenance vehicles shall be provided to
conservation areas.
(c) Conservation areas may include greenways, shared use paths, walking paths,
and other trails for access to environmental resources, parks, and other amenities
for the benefit of the subdivision residents and general public. Conservation areas
are not required to serve as passive or active recreation area in addition to the
required percentage of common open space to be set-aside by Zoning Ordinance
standards.
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(d) Grading, removal of topsoil, and other disturbance of features identified by
the natural resources inventory required by Section 23.602 and located in
Conservation Areas is not permitted. The Public Works Director may authorize a
modification of the conservation area to improve the appearance of natural
features or to restore the overall condition and natural processes, in compliance
with an approved management plan, as described in Section 23.605. The Public
Works Director may also authorize impacts to the conservation area for essential
infrastructure.
(e) Conservation areas shall be managed in accordance with a Conservation Area
Management Plan as outlined in Section 23.605 and applicable landscaping
standards in Section 23.603(5).
(f) The conservation area shall be designated as a Conservation Easement as
detailed in the definition section of this ordinance.
(a) All residential units should be in cluster groups unless the site has been designed to
preserve sensitive areas and maintain a stormwater treatment train.
(b) All lots shall take access from interior roads.
(c) All separation areas for residential lots along existing roads shall be landscaped in
accordance with the conservation area landscaping requirements in Section 23.603(2)(f).
d) Eighty percent (80%) of residential lots shall abut a conservation area or open pace to
the front or rear. Open space and conservation area across a road shall qualify for this
requirement.
(e) Cluster groups shall be located to avoid or mitigate directly disturbing existing native
prairie, woodlands, wetlands and other natural features identified in the site inventory of
natural resources
(3) Residential Lot Layout.
(a) All single-family residential subdivisions shall incorporate open spaces in order to meet
the intent of subdivisions with dispersed and connected conservation areas with a natural
setting that supports a treatment train approach to stormwater management. For example,
if all conservation areas are at one remote area of the site, other open space features would
be required to meet the intent of connected large open spaces. However, not all areas must
strictly be linked together.
(b)The use of cluster groups, smaller lots, or other unique residential lot layouts that
support reduced impervious area along with maximizing conservation areas and open space
are highly encouraged. Lot layout design shall minimize overall mass grading of site and
be situated in a manner that maintains the general topography and natural site features such
as drainage ways.
(c) In support of reduced impervious areas and larger conservation areas within a
development, use of limited connectivity street networks such as loop streets and cul-de-
sacs may be appropriate. These designs shall be shown to provide for convenient
circulation routes, and to otherwise meet the intent of Section 23.401(1)(d) regarding
minimizing dead-end streets. Limited connectivity street networks shall still provide for
access to significant conservation areas and for convenient pedestrian circulation routes.
(d) All lots shall take access from interior roads.
(e) Shared driveways to reduce impervious surfaces are encouraged.
(f) Residential lots shall not contain large stormwater flowage easements.
(4) Connectivity and Roadway Design.
(a) All developments shall provide for pedestrian access for enjoyment of significant
conservation area and open space set asides.
(b) Roadway design, subdivision layout, and use of sidewalks and trails shall provide for
an interconnected neighborhood while minimizing impacts to natural areas and reducing
total impervious area within the development.
(c) Roadways are encouraged to follow natural contours and slopes to minimize
disturbance of drainage patterns.
(d) Sidewalks may be only required on one side of street for short block lengths with less
than four dwellings. However, all lots shall have direct access to sidewalks or the pathway
system.
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(e) Typical driveway approach sections, Chapter 7 of SUDAS specifications, shall be used.
(2) Site Requirements
(a) Open water areas - A 50-foot native vegetative buffer shall be maintained around open water
areas such as ponds and lakes unless a specific common use area is identified.
(b) Stream buffers - Stream buffers with native vegetation shall be maintained along stream areas
using the following requirements based on stream order:
(i) Streams exceeding 3rd order and above, the City requires sketches, maps, studies,
engineering reports, tests, profiles, cross-sections, construction plans and specifications to
determine adequate buffer widths.
(ii) Perennial streams (1st and 2nd order). The total required stream buffer width is one
hundred (l00) feet on each side perpendicular to the waterway measured from the outer wet
edge of the channel during base flows.
(iii) Intermittent streams. The total required stream buffer width is fifty (50) feet on each
side perpendicular to the water way measured from the centerline of the channel.
(iv) Waterways and/or dry channels that have a contributing drainage area of fifty (50)
acres or greater. The total required stream buffer width is thirty (30) feet on each side
perpendicular to the waterway measured from the centerline of the waterway.
(v) Waterways and/or dry channels with a contributing drainage area of less than 50 acres.
The total required stream buffer width is twenty (20) feet on each side perpendicular to the
waterway measured from the centerline of the waterway.
(5c) Stormwater Management Design.
(a) Development is subject to all requirements of Ames Municipal Code Chapters 5A and
5B for minimum stormwater management requirements.
(b) The stormwater management design shall utilize low-impact development principles
and best management practices in a treatment train to address water quality. This
includes, but is not limited to, the following:
(i) Minimize the use of storm sewer piping and maximize the use of swales.
(ii) Use curb cuts in lieu of storm sewer intakes when appropriate when adjacent to
conservation areas to divert street water to a stormwater conveyance or treatment
system.
(iii) Sump pump discharge can be dDischarged sump pumps where possible into a
stormwater conveyance or treatment system.
(iv) Use conservation areas for Oon-site treatment and storage of stormwater
generated by the development shall occur in conservation area if it is consistent with
the environmental functions of the conservation area. Individual lot on-site
stormwater management may also be used in conservation subdivisions in conjunction
with open space and conservation area management of stormwater.
(v) Select a variety of targeted stormwater management best practices and facilities to
use in a series to reduce off-site discharge of pollutants including Total Suspended
Solids (TSS), phosphorous, nitrogen, E. coli, and metals. A singular stormwater
treatment measure of a detention pond will not meet this standard.
(vi) Provide pre-treatment for stormwater runoff through practices such as swales,
bioretention cells, and vegetative buffers. Forebays or other water quality practice may
be required prior to surface-stormwater detention practices such as constructed
wetlands and wet and dry ponds to enhance such practices.
(vvii) Include detailed design information for the stormwater management practices in
accordance with City stormwater requirements in Chapter 5B Post Construction
Stormwater Management Ordinance following the design information provided in the
Iowa Stormwater Management Manual. including The stormwater treatment train
approach shall be used where appropriate to capture, treat and release stormwatera
total pollution reduction summary for Total Suspended Solids (TSS), phosphorous,
nitrogen, and metals showing reductions achieved by discharge point and practice in
the treatment train. The Public Works Director may require additional practices to
protect water quality based on reductions shown.
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(vii) For longer duration buildout of a subdivision, sediment basins shall be provided
until final stabilization. Their location and storage capacity per acre drained shall be
indicated on the grading plan. The approved plan shall be incorporated into the
SWPPP required by Chapter 5A.
(d) Shared use paths, sidewalks, and driveway
(i) An accessible and interconnected shared use path system shall be developed to connect
residential areas with open space/conservation areas within or adjacent to the site.
(ii) Sidewalks shall only be required on one side of streets; however, all lots shall have
direct access to sidewalks or the pathway system.
(iii) Typical driveway approach sections, Chapter 7 of SUDAS specifications, shall be
used.
(e) Conservation Area Requirements
(i) The conservation area shall be designated as a Conservation Easement as detailed in
the definition section of this ordinance.
(ii) Applicants must provide an explanation of the conservation area objectives achieved
with their proposed development and identify the percentage of the total development area
that this area occupies.
(iii) All conservation areas shall be part of a larger continuous and integrated system
except for conservation areas that are naturally isolated from other conservation areas on
or near the site. For the purposes of this section, continuous shall be defined as either
physically touching or located across a public right-of-way, for example, on opposite sides
of an internal road.
(iv) Conservation areas, in accordance with the Conservation Area Management and
Ownership outlined in Section 23.605, shall protect site features identified in the site
natural resources inventory Section 23.604 (1) and analysis as having particular value in
preserving and/or restoring the natural character and conserving natural resources in
compliance with the intent of this ordinance and consistent with the goals and objectives
of this ordinance.
(v) Healthy natural features such as woodlands, prairie, wetlands, and streambanks shall
generally be maintained in their natural condition. If recommended by a professional with
pertinent qualifications, the Municipal Engineer may authorize a modification to improve
the natural features’ appearance or restore the overall condition and natural processes, in
compliance with an approved management plan, as described in Section 23.605.
(vi) All wetlands, floodways, and/or identified wildlife habitat areas shall be contained in
conservation areas.
(vii) Conservation areas and open space shall be distributed throughout the development
and combined shall comprise at least twenty-five (25) percent of the total area of the
subdivision. An area comprised of conservation areas and open space greater than twenty-
five percent of the total area of the subdivision may be required if necessary to maintain
health features such as woodlands, prairie, wetlands and streambanks in their natural
condition as provided in 23.603(2)(v).
(viii) Safe and convenient pedestrian access and access easements sufficient for
maintenance vehicles shall be provided to conservation areas.
(6 f) Landscaping. for Conservation Subdivisions – The layout and design of a subdivision includes
a variety of conservation and open space areas. A landscaping plan shall be prepared that identifies
all proposed landscaping within common areas and conforms to the following:
(i) The preservation of existing native, non-invasive vegetation as identified in the natural
resources inventory Section 23.604(1) 23.602 as being in good condition and of good
quality shall generally be preferred to the installation of new plant material. New plant
material shall be primarily native species.
(ii) Mass grading of sites shall be minimized in order to preserve the natural features of
the site.
(iii) Within all required separation areas between residential lots and external roads and
site boundaries, existing woodlands with desirable tree species shall be retained.
(iiiv) All new landscaping in conservation areas to be installed and existing native
vegetation to be preserved shall be protected through a conservation easement. Native
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landscaping shall be installed according to the guidelines provided in the Iowa Stormwater
Management Manual Section 2E-6.
(iv) Trees of native species as indicated by the Iowa Department of Natural Resources and
approved by the City shall be planted along internal roads within cluster groups in a total
amount equivalent to the standard subdivision requirements. Trees may be planted, but are
not required, along internal roads passing through conservation areas.
(vi) Informal, irregular, or natural arrangement is required for newly planted trees and
other landscaped areas to avoid the urban appearance that regular spacing may evoke.
(vii) Trees shall be located so as not to interfere with the installation and maintenance of
utilities, shared use paths, or sidewalks that may parallel the road.
(viii) Within all conservation areas, separation between external roads and residential lots,
a vegetated buffer area at least 25 feet in width shall be maintained or established. Where
no natural trees and/or shrubs exist, native plant materials shall be planted.
(xvii) Required buffers around wetlands, all water bodies and drainageways must be
naturally vegetated or planted with native plant species appropriate to the surrounding
landscape.
(viii) Buffers consisting of an informal, irregular or natural arrangement of native plant
species, combined with infrequent or prescriptive mowing are required to create a low-
maintenance, naturalized landscape.
(ixii) In addition to the above, land management practices minimizing the impact of
nutrients shall be used and demonstrated in Ada Hayden Watershed; minimal fertilization
of lawns including the use of phosphorus-free fertilizers is recommended.
APPLICATION PROCEDURE.
In addition to the standard subdivision application requirements, an inventory and mapping of natural
resources shall be conducted prior to the initial submittal.
(1) Inventory and Mapping of Natural Resources. An inventory of natural resources of the proposed
development site shall be conducted by experts in the field such as biologists, ecologists, soil
scientists, hydrologists, geologists or those credentialed in a manner acceptable to the Municipal
Engineer and must be submitted with the conservation subdivision application. The inventory must
include, but is not limited to the following information mapped at a scale of no less than one inch
equals 50 feet:
(a) Topographic contours at 2-foot intervals.
(b) United States Department of Agriculture, Natural Resource Conservation Service soil
type locations and identification of soil type characteristics such as percolation rates,
suitability for infiltration-based stormwater management practices, hydric soils, depth to
water table, and suitability for wastewater disposal systems if applicable.
(c) Hydrologic characteristics, including surface water bodies, floodplains, groundwater
recharge and discharge areas, wetlands, natural swales, drainage ways, and slopes 10% or
greater.
(d) Land cover on the site including but not limited to prairie, woodland, forest, wetland
and general cover type (pasture, woodland, etc.), and stand-alone trees with a caliper of
more than [24] inches measured four feet off the ground. The inventory shall include
comments on the health and condition of the natural resources.
(e) Known critical habitat areas for rare, threatened or endangered species using existing
documented inventories.
(f) Cultural resources shall be identified by a brief description of historic character of
buildings and structures, historically important landscapes, and archeological features
using a review of existing, documented inventories.
(2) Education and Outreach Plan for the Development. An educational plan shall be developed and
distributed to all perspective lot owners that describes the characteristics of the conservation
subdivision including the development concept, conservation areas management practices that will
be used to manage these areas, and benefits of the natural features. They shall also include
information on lawn care strategies that reduce nutrient and pesticide inputs and pollution to local
water bodies. Lot owners shall be made aware of the wildlife aspects of a conservation subdivision.
Deer, birds, and other animals and insects will be attracted to the natural areas.
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23.6054. CONSERVATION AREA MANAGEMENT AND OWNERSHIP.
(1) Conservation Area Management Plan. Every development conservation subdivision must
include a plan that provides evidence of a means to properly manage the conservation areas and
open space areas in perpetuity through a conservation easement for conservation areas or common
ownership for open space areas and evidence of the long-term means to properly manage and
maintain all common facilities, including any stormwater facilities. The plan shall be approved by
the Public Works Director Municipal Engineer prior to plat approval.
(a) A conservation area management plan shall be submitted with the following
components during the following approval stages:
(2) Preliminary Plat:
(a) Include a conservation area management plan specifically focusing on the long-term
management of conservation areas. The conservation area management plan shall include
a narrative, based on the site analysis required in Section 23.604(1), describing:
(i) Existing conditions including all natural, cultural, historic, and scenic elements
in the landscape.
(ii) The proposed completed condition for each conservation area; and the
measures proposed for achieving the end state.
(iii) Proposed restoration measures, including: measures for correcting
increasingly destructive conditions, such as erosion, and measures for restoring
habitats, ecosystems, and historic features.
(3) Final Plat:
(a) The conservation area management plan shall include the following items for final plat
approval:
(i) Provide a copy of the conservation easement acceptable to the City in a
recordable format.
(ii) Designate the ownership of the conservation area and common facilities.
(iii) Establish necessary regular and periodic operation and maintenance
responsibilities.
(iv) Estimate staffing needs, insurance requirements, and other associated costs
and define the means for funding the same on an on-going basis.
(v) The operations needed for maintaining the stability of the resources, including:
mowing schedules; native vegetation burns; weed control; planting schedules;
clearing and cleanup; the applicant shall be required to provide financial security
in a form acceptable to the city for the maintenance and operation costs of
conservation areas for a two-year period of time at time of the plat.
(vi) A proposed Education and Outreach Plan for the Development. An
educational plan shall be developed to be distributed to all prospective lot owners
that describes the characteristics of conservation subdivision including the
development concept, conservation areas management practices that will be used
to manage these areas, and benefits of the natural features. It shall also include
information on lawn care strategies that reduce nutrient and pesticide inputs and
pollution to local water bodies. Lot owners shall be made aware of the wildlife
aspects of a conservation subdivision. Deer, birds, and other animals and insects
will be attracted to the natural areas.”
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Section Two. All ordinances, or parts of ordinances, in conflict herewith are hereby repealed to the
extent of such conflict, if any.
Section Three. This ordinance shall be in full force and effect from and after its passage and
publication as required by law.
Passed this day of , 2025.
______________________________________ _______________________________________
Renee Hall, City Clerk John A. Haila, Mayor
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