[7-21-2021 by Ord. No. 1796]
A. The intent of this article is to ensure the long-term environmental
sustainability of the City of Holland by applying standards that preserve
and enhance the City's tree and landscaping coverage and enable developments to meet low-impact
development (LID) goals by incorporating green infrastructure into site design. LID assists the City in reaching its goals
to decrease flooding events, erosion, and pollutants entering the
waterways, and to protect groundwater and surface water quality by
infiltrating, filtering, storing, and detaining stormwater runoff
close to its source. These investments yield multiple benefits toward building City resilience, as indicated in detail below.
B. Benefits of low-impact development (LID) standards.
1. Preserve, protect, and enhance the City's urban tree canopy. One
of the City's sustainability and resiliency goals is to preserve,
protect, and enhance the City of Holland's urban tree canopy. This provides numerous natural benefits for air and water quality,
prevents the urban heat island effect, reduces harmful UV radiation,
lowers heating and cooling costs, mitigates soil erosion and stream
pollution, and ensures long-term environmental sustainability, since
planting trees remains one of the cheapest and most
effective means of drawing excess CO2 from the atmosphere.
2. Promote surface infiltration. LID is achieved through site design
that promotes surface water infiltration when impervious surfaces
(buildings, parking lots, etc.) are clustered to preserve undeveloped,
landscaped, or tree-covered pervious surfaces (natural green infrastructure),
and when site design includes a balanced mixture of pervious and impervious
surfaces, combined with structural green infrastructure. Both allow
stormwater to enter into the ground (infiltrate) and into conventional
infrastructure pipes and waterways more slowly, which reduces the
threat of local flooding and the amount of pollution that reaches
waterways.
Surface Infiltration Process
|
3. Minimize erosion. In urban areas, increased volume and velocity of
stormwater runoff causes erosion of both the land surface and the
streambank. As erosion occurs, the path of the waterway changes and
is more likely to intrude onto private properties, destabilize the land, and affect the roots of trees, making them unable to provide their full benefits.
4. Decrease pollutants. Increased impervious surface area does not allow rain and snowmelt to soak into the ground. This
leads to excess stormwater runoff that washes pollutants off of impervious surfaces and carries them into the City's lakes
and streams as shown in the image titled "Urban Wet Weather Flows."
Pollutants from urban runoff include oil, grease, and toxic chemicals
from motor vehicles, pesticides from lawns, viruses
and bacteria from pet waste, road salts, heavy metals from roof shingles
and motor vehicles, and thermal pollution from impervious surfaces. These pollutants can harm fish and
wildlife populations, kill native vegetation, foul drinking water,
and make recreational areas unsafe and unpleasant. (EPA. https://www.epa.gov/nps/nonpoint-source-urban-areas)
5. Decrease flooding. In a one-inch rainstorm, about 4,000 gallons of
water falls on a typical residential lot in the City of Holland, which
is enough to fill a swimming pool. In most development designs, about two-thirds of that water flows directly to storm drains.
6. Additional LID benefits.
a.
Increase property values.
d.
Reduce infrastructure costs.
e.
Reduce costs associated with flooding.
h.
Increase mental health and worker productivity.
C. Site design to achieve LID goals. To ensure LID goals are met, the
following standards are required, which shall be further specified
in this article:
2. Impervious surface maximums for certain zone districts.
3. Green infrastructure requirements.
Traditional Parking Lot Design
|
Preferred: LID Parking Lot Design
|
Traditional "Big Box" Site Layout
|
Preferred: Equivalent LID Site Layout
|
[7-21-2021 by Ord. No. 1796]
A. Applicability. The following developments shall
comply with the landscape requirements in this article:
1. New construction on any property requiring site plan approval.
2. Building additions on any property requiring site plan approval.
3. New parking lots or reconfigurations of parking lots, deemed significant enough by the approving
authority, and requiring site plan approval.
4. Street construction or reconstruction.
5. Residential dwellings with one to four units shall only be subject
to the street
tree requirements of Section
39-6.02C. The
Zoning Administrator and City Engineer may waive
this requirement if deemed unnecessary.
B. Landscape Requirements Table. The table below summarizes the
landscape requirements, which are further specified in Section
39-6.02C through
G. An Airport
Zone District is exempt
from these requirements.
Landscaping Type
|
Requirements
|
---|
Trees along street frontage
|
1 tree per 30 feet
|
Parking lot interior
|
1 square foot of landscaping per 20 square feet of pavement
|
Parking lot islands
|
1 island with a tree per 20 spaces
Parking lots under 20 spaces exempt
|
Parking lot perimeter
|
1 square foot of landscaping per 20 square feet of pavement
|
Building perimeter
|
Along all walls visible from a street or parking lot, required
for buildings with a front setback greater than 2 feet
|
Residential buffer
|
Required when property is adjacent to a residential zone district
|
Green infrastructure
|
Site design meeting the requirements of Sections 39-6.06 through 39-6.08
|
C. Street trees along the right-of-way.
1. Requirements.
a.
One street tree per 30 linear feet measured at the center of
each tree.
b.
Minimum 2.5 caliper in size as measured at
4.5 feet above grade.
c.
Existing street trees may be counted towards street tree requirements when stated and shown on the site
plan.
d.
Street trees shall be planted in the right-of-way between the property line and
the street unless the applicant states why this is
not practical and shows an alternative on the site plan. The alternative shall be to either locate the trees a maximum of 10 feet from the right-of-way line
or allow the planting of ornamental trees depending
on the described rationale. The alternative will be reviewed and may
be approved by the approving authority.
e.
Urban streets or when planting trees into concrete
or brick, the following requirements shall be followed:
1)
Street trees shall be planted in accordance
with MISS DIG and avoid impacts with existing utilities.
2)
Street trees planted in the public right-of-way become the property of the
City of Holland.
3)
Streets trees shall be planted so as not to
damage brick pavers and not to interfere with snowmelt systems.
4)
Street trees shall be irrigated with drip irrigation
bubbles.
5)
Street trees shall be planted in raised beds
or in frames, as shown in the graphic.
|
Street Tree Types:
|
•
|
Columnar if close to buildings
|
•
|
Maple if able to grow out for a tree canopy
|
•
|
Ornamental trees where approved
|
•
|
Do not use locust trees in brick pavers
|
2. Species. Species shall be approved if they, in the opinion of the approving authority, meet these standards:
b.
Are generally resistant to salt, insects, diseases, damage,
and drought.
c.
Provide adequate shade and aesthetics.
d.
Are not anticipated to damage street, nonmotorized, or utility
infrastructure with their root or branch systems.
D. Parking Lot Island Rain Garden, 16th Street
Parking Lot Island Rain Garden, 16th Street
Interior parking lot and parking lot islands shall meet the following requirements:
1. One square foot of interior parking lot landscaping is required per 20 square feet of parking lot pavement.
2. Parking lot islands are required every 20 parking spaces minimum and shall meet the following requirements:
a.
Two hundred fifty square feet in size minimum;
b.
Include a minimum of one tree each; and
c.
Include additional
landscaping, an approved
ground cover, and/or structural green infrastructure. See Sections
39-6.06 through
39-6.08.
d.
Width minimums.
1)
No pedestrian pathway: seven feet.
2)
Pedestrian pathway: 11 feet. The pathway shall be a minimum
five feet wide, with a minimum of three feet of landscaping on each side of the pathway.
e.
Waiver. A waiver may be approved by the approving authority to reduce the amount of parking lot islands required
if the proposed interior parking lot landscaping still
meets the intent of this section.
f.
Curbs. Parking lot islands shall have curbs,
unless the island is designed as a vegetated swale, in which case
curbs may be eliminated or inlets may be constructed within the curb
to allow for stormwater flow. Vegetated swale design shall be approved
by the City Engineer.
E. Parking lot perimeter landscaping shall meet the following requirements:
1. One square foot of perimeter parking lot landscaping is required per 20 square feet of parking lot pavement;
2. Shall be planted surrounding parking lots and consist
of a mixture of landscaping and permitted ground
cover types; and
3. Street trees shall count towards both street tree and parking lot perimeter requirements.
F. Building perimeter landscaping shall
meet the following requirements:
1. Shall be planted along building walls visible from a public street
or from a parking lot.
2. Shall consist of a mixture of landscaping and approved ground cover types.
3. Plantings shall be in the building setback when
the building has a setback of two
feet or greater. Plantings may be in an above ground planter when
the building is setback between
two feet and six feet from the street fronting property line.
4. Waiver. The approving authority may waive these
requirements if determined the design, use, or context of the property does not necessitate any or all building perimeter landscaping.
G. Trees and ground cover type requirements.
1. Minimum size at planting.
Plant Material
|
Minimum Plant Size
|
Where Measured
|
---|
Canopy/shade trees
|
2.5-inch caliper
|
4.5 feet above grade
|
Ornamental trees
|
2.0-inch caliper
|
4.5 feet above grade
|
Evergreen trees
|
5 feet in height
|
Highest point, including leaves or flowers
|
Shrubs
|
3 feet in height
|
Highest point, including leaves or flowers
|
2. Ground cover types and requirements.
a.
Native vegetation. These are listed in the Michigan State University
Native Plants and Ecosystem Services Southern Lower Peninsula Regional
Plant List, or those species that occurred within nearby municipal
boundaries prior to European settlement, according to available historical
and scientific evidence. These species shall not require pesticide
and herbicide applications, in order to eliminate toxicity to local
wildlife and aquatic habitats.
Native Plants
Source: Rethinking the American Lawn, Ottawa Country
Planning and Performance Improvement
|
b.
Xeriscape: landscape that reduces or eliminates the need for
irrigation. Xeriscape plants range from succulents to leafy, flowering trees.
c.
Rain garden plantings: no additional requirements.
d.
Perennial and annual flowers: no additional requirements.
e.
Mulch. One shrub per 50 square feet shall be
planted on parking lot islands in addition to a tree. Ten percent of a parking lot island
shall be a mulch planting bed with flowers or flowering shrubs. Turf grass shall only supplement
other ground cover types to provide a multispecies
landscape to increase biodiversity.
f.
Rocks and stones are not permitted as a primary ground
cover and may only be used in building perimeter
maintenance strips and in limited situations where mulching may otherwise
be problematic with storm drainage plans, as approved by the approving authority.
3. Prohibited species are invasive species artificially introduced to
West Michigan, are nonnative, and are capable of out-competing and
displacing native vegetation. Any species on the Michigan Department
of Natural Resources list of invasive species shall be prohibited,
in addition to those listed on the following table. Existing prohibited
species shall be identified on a site plan and shall
not count towards landscape requirements.
Common Name
|
Botanical Name
|
---|
Amur maple
|
Acer Ginnala
|
Autumn olive
|
Elaeagnus Umbellata
|
Black locust
|
Robinia Spp.
|
Box elder
|
Acer Negundo
|
Common buckthorn
|
Rhamnus Cathartica
|
Common reed
|
Phragmites australis
|
Flowering rush
|
Butomus umbellatus
|
Garlic mustard
|
Alliaria petiolata
|
Giant knotweed
|
Polygonum sahalinensis (Fallopia sachalinensis)
|
Glossy buckthorn
|
Rhamnus Frangula
|
Japanese barberry
|
Berberis Thunbergii
|
Japanese knotweed
|
Fallopia japonica
|
Lombardy poplar
|
Populus nigra var. italica
|
Multiflora rose
|
Rosa Multiflora
|
Purple loosestrife
|
Lythrum salicaria
|
Russian olive
|
Elaeagnus Angustifolia
|
Spotted knapweed
|
Centaurea Biebersteinii
|
Tree of heaven
|
Ailanthus Altissima
|
White mulberry
|
Morus alba
|
H. Tree replacement requirements.
1. Applicability. Lots half an acre in size or greater, where five or
more trees are proposed to be removed. These trees include:
a.
Deciduous trees over six inches in diameter at breast height (DBH).
b.
Coniferous trees over 10 feet in height.
c.
Healthy and noninvasive trees.
2. Definition of "removed tree": The destruction, relocation, or cutting
of a tree so that no portion larger than a stump
remains intact on the site, or the mutilation of
a tree to the point of near certain death.
3. Replacement requirements.
Trees shall either be
replaced on-site at a ratio of one replacement
tree per five removed
trees, or a payment in lieu of
trees shall be made per the requirements of Section
39-6.02H.4. Replacement
trees shall comply with the following:
a.
Deciduous replacement trees shall be a minimum three inches DBH at planting.
b.
Coniferous replacement trees shall be a minimum
10 feet in height.
c.
Prohibited species listed in Section
39-6.02G.3 shall not be used as replacement
trees.
d.
Replacement trees may be counted as required trees to meet other requirements of this section.
e.
Replacement trees shall be indicated on the
site plan and planted in locations that, in the opinion of the approving authority, would have the greatest impact on reducing
urban heat islands to make the City more resilient.
4. Payment in lieu of trees. In lieu of planting trees on site, the applicant may pay a replacement fee per tree to the City
of Holland to plant trees elsewhere within the City
per the City's Tree Replacement Policy. The fee shall
be $300 per tree.
5. Professional tree survey. To verify the
trees that
shall be replaced, the
applicant shall submit a professional
tree survey performed by a licensed arborist, specifying which
trees meet and do not meet the applicability requirements of Section
39-6.02H.1. The
applicant shall then only
be required to replace or provide a payment in lieu of
trees for those specified.
6. No professional tree survey. The applicant shall either replace or provide a payment-in-lieu-of-trees per the standards in Section
39-6.02H.3 for all
trees, regardless of if they meet the applicability requirements in Section
39-6.02H.1. The number of
trees proposed for replacement shall be approved by the
approving
authority.
7. Exempt activities.
a.
Tree trimming and other routine maintenance that does not result
in the destruction, mutilation, relocation, or cutting of a tree leaving more than a stump intact.
b.
Emergency removal or trimming of trees made
necessary by a natural disaster, where the removal of the tree would prevent injury or damage to persons or property.
c.
Trees removed or trimmed by public
utilities, public agencies, or when located in seasonal tree farms.
I. Residential buffers are required when the property is located directly adjacent to a residential zone district.
1. Buffering shall be required along all property lines separating a multifamily, nonresidential use, or a mixed-use development and a residential zone district. This requirement shall also apply if the development is located in a residential zone district.
2. Buffering options.
a.
Wall.
1)
Minimum six feet in height.
2)
Solid or opaque and constructed from one of the following materials:
masonry, brick, vinyl, or wood.
b.
Berm.
1)
Berm slopes shall not exceed a 4:1 horizontal
to vertical ratio, with a top width of at least 1/2 the berm height,
and a maximum height of three feet above the base of the berm.
2)
Berm slopes shall be stabilized with an approved ground cover type and be located outside of clear
vision areas.
c.
Evergreen screen.
1)
An evergreen screen shall consist of a row
of evergreen trees, forming a complete screen as viewed from the adjacent residential property.
2)
Evergreens shall be a minimum five feet in
height at the time of planting.
d.
Landscape buffer area.
1)
Size: shall be a minimum 20 feet wide and shall extend along
the entire property line.
2)
Trees: shall include a minimum of one tree per
500 square feet of landscape area. If the landscape buffer area is
less than 500 square feet, then one tree shall be
required.
3)
Shrubs: shall include a minimum of four shrubs per 500 square feet of landscape area.
e.
Preserved woodlands.
1)
Shall be a minimum 20 feet wide and shall extend along the entire property line abutting the residential property.
2)
At least 90% of existing trees six inches in diameter
at breast height (DBH) or greater shall be retained.
J. Clear vision corners required.
1. Definition: a triangle formed on properties located
at intersection corners in required front or secondary street setbacks.
2. Measurement: established as a triangle formed by two points, each
a minimum of 20 feet from the intersection of the property
line and the line connecting the points.
3. Height maximum. Landscaping shall be a maximum of
three feet in height within a clear vision corner.
K. Additional landscape requirements.
1. Species variety. The landscape plan shall not contain more than 33%
of any single plant species. Landscape plans with fewer than 15 required
plantings shall be exempt from this requirement.
2. Stabilization. All landscape planting areas shall be stabilized and
maintained with seed, sod, ground covers, mulch, or
other approved materials to prevent soil erosion and allow stormwater
infiltration. Mulch shall be spread in a manner that
avoids soil compaction and shall not overflow into public rights-of-way.
3. Protection of trees during construction. For every one inch of DBH, there should be a one-foot radius of protection. Appropriate
guards shall be maintained around all existing trees to be retained. Remaining trees shall have sufficient
room for their root structures to be maintained during construction
and in site plan design.
4. Timing of planting. All required plant material shall be planted
prior to issuance of a final certificate of occupancy. In the event
that the development is completed during a time of
year when planting is impractical, a temporary certificate of occupancy
may be issued with a deadline for installing the required landscaping and obtaining a permanent certificate of occupancy.
A performance guarantee in the amount of the remaining improvements
may be required.
5. Completion of improvements. Tree stakes, tree ties, and tree wrap shall be removed
after completion of the initial growing season.
[7-21-2021 by Ord. No. 1796]
A. Property owners shall take all reasonable measures
to keep all landscaping alive and thriving and shall
provide the following:
1. A maintenance plan shall be included in the required written project summary stating which measures will be used to meet this requirement. This plan is separate from the maintenance agreement required by Chapter
29, Stormwater Ordinance.
2. Irrigation of trees and shrubs is required. The approving
authority may not require all landscaping to be irrigated, if requested, and if adequate green infrastructure
is otherwise provided, as determined by the approving authority.
3. Kept neat. All landscape materials, manufactured materials, and green
infrastructure shall be kept in a neat, orderly, and thriving manner,
free from debris and refuse.
4. Removal of plant material. All diseased, unhealthy, and dead plant
material or green infrastructure shall be removed immediately and
replaced. Replacement landscaping shall be installed
at or as close as possible to the size of the landscaping at the time of its removal.
5. Minimum height of branches over sidewalk. A branch hanging over a
public sidewalk or street shall be a minimum seven feet above grade and shall be maintained by the property owner. This maintenance shall include removal of dead branches or stubs
that are or may become a menace to people on the public sidewalk or
street.
6. Not permitted on publicly owned trees.
a.
Wearing spurs when climbing trees unless done
by a designated City of Holland employee or contractor.
b.
Wires shall not be attached to any tree.
c.
Signs shall not be attached to any tree.
7. Trees shall not be removed from the right-of-way without permission of City of Holland's Parks and Recreation Department.
[7-21-2021 by Ord. No. 1796]
A. Maximum impervious surface allowance. Impervious
surfaces shall not exceed the maximum percentage for these zone districts. An increase in the impervious surface percentage may be provided upon request if the approving
authority deems it necessary.
OS
|
HDR
|
CMU
|
GMU
|
RMU
|
I
|
---|
20%
|
70%
|
80%
|
70%
|
80%
|
80%
|
B. Required open space. All areas not covered by
buildings, parking areas, driveways, walkways, pedestrian plazas, other
impervious surfaces, or water surfaces shall be planted
with living vegetation, including
canopy trees,
shrubbery, and allowable
ground cover types (Section
39-6.02G.2).
[7-21-2021 by Ord. No. 1796]
A. Intent. To meet the City of Holland's sustainability and resiliency
goals, development needs to diversify the ways that
stormwater runoff is collected, infiltrated, stored, and treated.
Continued reliance solely on conventional infrastructure (water runoff
into pipes and ponds) has proven to be unsustainable, especially with
an increase in large storms and built development. The use of green infrastructure best management practices (BMPs)
has proven to be effective in working in conjunction with conventional
infrastructure to mimic natural processes and to meet low-impact development
site design.
B. Chapter
29 Stormwater Ordinance and UDO relationship. Most
developments shall be required to obtain a stormwater permit
from the City Engineer in addition to obtaining
site plan approval. Chapter
29, Article
VI, (Stormwater Ordinance) in the City's Code of Ordinances provides specific engineering standards to meet the ordinance and obtain a stormwater permit and references the
applicant to the City of Holland's Stormwater
Standards Manual for additional stormwater designs and details.
C. This section of UDO requires the applicant to meet the Stormwater Ordinance requirements in specific ways that
are critical for site design and achieving low-impact development
goals. The two ways these requirements do this are through the use
of structural green infrastructure best management practices and by
making retention and detention ponds amenities in
addition to being used for stormwater storage.
D. Structural green infrastructure requirement.
1. Structural green infrastructure best management practices (BMPs) shall be used to the maximum extent practicable to comply with the Chapter
29, Stormwater Ordinance, the adopted Stormwater Standards Manual, and to obtain a required stormwater permit. Credits are provided when using green infrastructure BMPs to meet the Stormwater Ordinance and are determined through stormwater permit calculations.
2. Nonstructural BMPs are encouraged to be used in addition to using
the required structural green infrastructure BMPs.
3. Additional best practices include managerial and certain other structural and nonstructural BMPs that are encouraged to be used in addition to the required structural green infrastructure BMPs. These are listed in Section
39-6.08.
E. Examples of green infrastructure BMPs.
1. Structural green infrastructure best management practices (BMPs) are stormwater management and treatment techniques where devices are constructed for temporary storage and treatment of stormwater runoff. The following structural green infrastructure BMPs shall be approved in meeting the requirement in Section
39-6.05C.
a.
Pervious durable surface, Section
39-6.06.
2. Additional structural green infrastructure BMPs are listed in Appendix
3 of the City's Stormwater Standards Manual as "LID and Small Site
Structural Best Management Practices." Other structural green infrastructure
BMPs may be requested and approved by the approving authority.
3. Nonstructural green infrastructure BMPs are stormwater treatment
techniques that use natural measures to manage and treat stormwater
and do not involve the construction or installation of devices. These
types are encouraged, but are not required or countable in meeting
the requirement of this section. They include:
b.
Minimized soil compaction.
c.
Natural flow paths and sensitive area preservation.
F. Retention and detention pond amenities.
1. Intent: to incorporate retention and detention ponds into the overall
site design by designing them to be site amenities.
2. Definitions. A "retention pond" is a permanent wet pond without a
positive surface outlet, or a temporary wet pond that drains dry through
infiltration into the ground, which is used to manage stormwater runoff.
A "detention pond" is a permanent wet pond with a surface outlet,
or a temporary wet pond that drains dry through the use of stormwater
infrastructure.
3. Design standards.
a.
Retention or detention ponds shall provide an amenity in the site's design that in the opinion of the approving authority provides a benefit beyond the storage
of stormwater; and
b.
The location of the retention or detention pond shall, in the
opinion of the approving authority, be able to amply
benefit the proposed users of the site.
4. Examples of approvable amenities are:
a.
Permanent wet pond.
3)
Walking path around or over the pond.
b.
Temporary wet pond.
2)
Walking path around, on, or over the pond.
[7-21-2021 by Ord. No. 1796]
A. Intent. The use of pervious surfaces in site and
street design mimics natural ground water infiltration, decreases
the amount of post-construction stormwater runoff, and implements
low-impact development (LID).
B. "Pervious" definition: a surface covering the ground that allows
the infiltration of water into the ground and provides stormwater
treatment and storage without a surface outlet; also referred to as
"permeable" or "porous."
C. Pervious durable surface types. The following types of pervious surfaces shall be permitted to meet the durable paving requirements in Section
39-9.02 and are also a type of structural green infrastructure.
1. Grass pavers: used for areas with occasional parking; not permitted
for high-use areas.
2. Permeable interlocking concrete pavers.
4. Permeable clay brick pavers: used for areas with pedestrian and vehicular
traffic.
7. Plastic grids. These grids help reinforce driveways, parking
lots, and fire lanes. Plastic grids can also be planted with grass. Used for areas with occasional parking; not permitted
for high-use areas.
8. Any type not listed but approved by the City Engineer and the approving authority.
Pervious and Nonpervious Split Parking Lot, Hope College
|
Pervious Parking Lane
|
Permeable Grass Pavers, Detroit, MI
|
Grass Pavers, Detroit, Michigan
|
D. Benefits of pervious durable surfaces. (Source:
'Introduction to Green Infrastructure Techniques and Opportunities',
Drummond Carpenter, PLLC)
1. Eliminates or minimizes runoff.
3. Traps suspended solids and pollutants.
4. Melting water seeps through the pavement instead of freezing to increase
slip and fall protection.
5. Reduces surface temperatures and, therefore, the heat island effect.
6. Eliminates the need for retention basins and water collection areas.
7. Eliminates costs for retention basins, curbs, gutters, and other
water collection installations.
8. In winter conditions, typically requires much less salt or other
de-icing products than traditional pavement types.
9. Lower installation costs (no underground piping, storm drains, or
sloping/grading needed).
10.
Low life-cycle costs with an equal life expectancy to that of
regular concrete (20 to 40 years when correctly installed).
[7-21-2021 by Ord. No. 1796]
A. Rain gardens, also called "bioretention facilities," provide stormwater
treatment, water storage, and uptake with or without a surface outlet.
They are best used in drainage areas and can be used in a combination
with an underdrain BMP to provide extended detention for channel protection.
See
tree box, Section
39-6.07D. Rain gardens are designed to reduce the stormwater flow rate, quantity, and pollutant load of runoff from
impervious surfaces to manage
water on-site. Rain gardens rely on plants and natural or engineered
soil medium to retain stormwater and increase infiltration, while
remediating and filtering pollutants carried by urban runoff. They
also provide a method to reuse and optimize water, reducing the need
for additional irrigation. Rain gardens decrease ambient air and water
temperature to reduce the urban heat-island effect.
1. Common locations for rain gardens are in or along a:
d.
Street.
Parking Lot Island Rain Garden
|
Parking Lot Perimeter - Curb Cut Rain Garden
|
Field Rain Garden
|
Street Bioretention/Rain Gardens
|
B. Vegetated swales are similar to rain gardens, but they focus more
on channeling stormwater off from streets and parking lots whereas rain gardens focus on retaining water on site. This BMP is a stormwater conveyance designed to slow, filter, and
infiltrate stormwater and is used for small drainage areas with concentrated
water flow. A vegetated swale is typically designed with sufficient
bottom slope to convey water while filtering it.
C. Vegetated green roofs provide stormwater treatment and water storage
with a surface overflow. They are most practical for flat or slightly
sloped rooftops. They provide a stormwater buffer, purify the air,
reduce ambient temperature, regulate indoor temperates, save energy,
and encourage biodiversity.
D. Tree filter boxes and planter boxes are infiltration
filters that combine structural green infrastructure BMPs, nonstructural
green infrastructure BMPs, and a perforated underdrain pipe, to retain
and filter water. They are most often used on the sides of or center
of streets and in parking lot islands.
Trees planted with pervious pavement reduce stormwater
flow and reduce associated pollution
|
E. Constructed filters are underdrained structures or excavated areas
containing a layer of sand, compost, organic material, peat, or other
media that reduce pollutant levels in stormwater runoff by filtering
sediments, metals, hydrocarbons, and other pollutants before the stormwater
reaches the underdrain to be routed to the storm sewer system. Constructed
filters are suitable for sites where infiltration
is not possible or practical. Any one of the aforementioned bioretention
BMPs can also operate as a constructed filter if it has an impervious
bottom/sides and includes an underdrain.
Constructed Filter Graphic
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F. Vegetated filter strips are permanent, maintained strips of vegetation
designed to slow runoff velocities and filter out sediment and other
pollutants from urban stormwater. Filter strips require the presence
of sheet flow across the strip, which can be achieved through the
use of level spreaders. Frequently, filter strips are designed for
pretreatment where runoff is directed from a parking lot into another BMP.
Vegetated Filter Strip.
Slope design may vary from site to site.
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[7-21-2021 by Ord. No. 1796]
A. The following stormwater management and green infrastructure practices
are encouraged by UDO because all uses impact sustainability and can
assist in meeting the City of Holland's low-impact development (LID) goals.
2. Planting of trees on residential properties.
5. Water-efficient landscaping.
6. Washing cars on a lawn area.
7. Downspout extensions to direct water away from a building foundation, directed into the lawn, landscape, or a rain garden.
8. Water harvesting: use of rain barrels or other mechanisms to collect
and store rainwater from roofs to use for irrigation.
9. Residential rain gardens.