HomeMy WebLinkAboutSCENIC VIEWS PUD - FINAL - 3-96A - SUBMITTAL DOCUMENTS - ROUND 2 - STORMWATER MANAGEMENT PLAN2.3 Wetlands Transfer
There is an existing area of about 8,000 sq.ft. near the northwest property boundary
which is a wetlands created accidentally when the CSU Detention Pond and City
water lines were installed in Overland Trail in 1988. This wetlands is too small to
qualify for U.S. Corp of Engineer regulations, but will be relocated to the Detention
Pond area to enhance stormwater quality and to create a visual amenity for residents.
2.4 Stormwater Quality and Best Management Practices
2.4.1 Existing Stormwater Quality --Prior to Development
a. The existing storm runoff now contains fertilizers and pesticides used
to grow alfalfa, plus wastewater and stream particulates from the CSU
Veterinary School and Equine Center. In storm conditions these
particulates are deposited into the canal.
b. In periods of storm runoff, particulates from the horse pastures to the
north of the Scenic Views site enter the canal.
c. According to the ditch company representative, it is a common
occurrence to have illegal dumping of oil, trash, and organic materials
into the canal.
d. Under present conditions, the canal water quality is poor quality due to
runoff for up to 24 hours after a storm,. The canal representative has
advised the Happy Heart Farm and other water users "NOT TO USE
the canal water for irrigation purposes within 24 hours of a storm
because of its poor quality during storm events." After 24 hours the
sediment will settle out in the canal bottom, and the water quality vastly
improves for irrigation.
e. The irrigation canal water is NOT for human consumption.
f. The ditch company has NO WATER QUALITY delivery standards or
criteria to meet or to guarantee for any of its users. Users of the
irrigation ditch take whatever water is in the ditch and use it for
irrigation purposes. They have operated this way for many generations
without service disruption or dissatisfied customers.
g. The irrigation company sees the creation of a retention pond as an
effective tool for limiting peak flows, which could also improve the
stormwater quality which would flow overland into the ditch. They
also recognize there would be less risk of overtopping of the ditch due
to flooding. They are also aware that detaining the stormrunoff would
cause less damage to the ditch embankments, and would result in
greater effective use of the ditch capacity in flood periods. They also
recognize the detention basin would reduce the historic flow of
stormrunoff into the ditch.
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By reviewing the Mean Number of Storm Days each month in Table 3, it is easy to
estimate how much of the time the retention area will be in use as a storm runoff
collector and how much of the time the area will be useable as open space for
residents. In the months of December, January, and February only ONE STORM a
month is expected to occur which will cause runoff... leaving an average of 25 days a
month of active open space for residents. During the months of September, October,
and November TWO STORMS are expected to occur which could produce
runoff... leaving an average of 22+ days a month for recreation. In the months of
March, April, June, and August THREE STORMS a month are expected to produce
runoff... leaving 18+ days a month for resident open space use. In May and July as
many as FOUR STORMS a month could produce runoff... leaving 15+ days for open
space use by residents. Based upon typical rainfall patterns for the area, the site would
be available for active open space use 258 days out of the year (71 % of the time), or
an average of 21+ days per month per year.
NOTE: These estimates are very conservative and assume it will take 2 full days to
drain the retention pond for each storm which exceeds 0.1 inch of rainfall.
From Tables 1 and 2 it is clear that for 80% of the storms which produce 0.1
inch of rainfall or more, the pond can be pumped within 7 hours time, if
desired. Thus, the estimate of DRY days usable as Open Space shown above
is the MINIMUM TIME estimate.
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2. FUNCTIONAL DIFFERENCES BETWEEN THE DETENTION & RETENTION POND
2.1. Definition of Detention, Extended Detention, and Retention Ponds
A detention pond holds runoff and may be releasing runoff simultaneously at the 2-yr
historic rate. The primary function of a detention or retention pond is moderating
flood flows. An added benefit is their ability to provide water quality enhancement.
An extended detention pond is designed to totally empty after runoff ends. The extended
pond extends the emptying time of the more frequent storms to facilitate pollutant
removal and does so with a smaller outlet. A drain time of the brim -full capture
volume of 40 hours is recommended to remove a significant portion of fine particulate
pollutants found in urban stormwater runoff. Soluble pollutant removal is enhanced
by providing a small wetland marsh or ponding area in the basin's bottom to promote
biological uptake. The basins or ponds are considered DRY because they are designed
not to have a significant permanent pool of water.
A retention pond has a permanent pool of water with a base flow to flush the
permanent pond, that is replaced with stormwater, in part or in total, during storm
runoff events. Temporary detention is provided above the permanent pool to allow
more sedimentation. Retention ponds are similar to extended basins because they are
designed to capture in total, and detain a volume of runoff from frequently occurring
storms. Retention ponds differ from extended detention basins because the runoff water
mixes with the permanent pool water as it rises above the permanent pool. The water
quality capture volume above the permanent pond is released over 40 hours, the same
as for an extended detention basin. The 40-hr discharge period allows the sediment
removal process to be more efficient when the outflow occurs above the bottom of the
basin. (See Utility Plan pond profile) Sediments become trapped below the outlet and
sedimentation continues in the pool after the captured surcharge volume is emptied.
Retention ponds are very effective in removing pollutants. They are used to improve
the quality of urban runoff from roads, parking lots, residential neighborhoods,
commercial areas, and industrial sites. They are generally used as regional or follow-
up treatment ponds.
Determination of the classification of the Scenic View basin as a retention pond or as
an extended detention pond is determined by the pond outlet elevation, the rainfall -
runoff data, the groundwater elevation, and the volume storage capacity.
2.2. Pond Water Levels for 2-Yr, 5-Yr, 10-Yr, and 100-Yr Storm Events and Impact on
Open Space Use
In a typical year the amount of runoff that needs to be detained can be estimated by
examining the mean inches of rainfall and storm frequency by month. Tables 1 and
2 contain the estimated amount of annual rainfall for the site. Table 3 shows the
seasonality of rainfall for the site. In general, 0.1 inches of rainfall depth is the
amount necessary to cause runoff. On average, about 35 storm events occur each year
that are equal to or greater than 0.1 inches in precipitation depth.
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1. RAINFALL, RUNOFF, AND POND DEPTH
1.1 Rainfall and Runoff data for the site show that 57% of the annual storms will create
practically NO RUNOFF producing events. These are storms with rainfall from .0 to
0.1 inch. About 34% of the storms will have rainfall depths from .10 to .50 inches.
These two categories of storms represent 91 % of the annual storms which will impact
the site and can be handled readily with only minor water depths in the retention
pond. The average depth would be 0" in the pond for a Storm of up to .5" if we were
retaining only site -generated runoff. With the pond designed to retain the off -site
flows from the CSU Equestrian Center and areas north of the site, the pond depth
would rise to 21" for a storm up to 0.5". Pond Depth refers to the area of the Pond
which is above the wetlands water quality control volume, which is graded a few feet
below the overall pond. The Pond would be DRY for resident use as Open Space, 97%
of time, if we were retaining solely on -site generated runoff. By increasing the capacity
of the pond to retain all off -site flows from the CSU facility and the area north of the
site, the pond will be dry 85% of the time during the year. Please refer to Table 1 and
2 on the following page for these explanations.
Rocky Mountain Research Institute
R M R 1 ,A91
rocky mountain research institute
marketing. real estate and economic consultants
DATE- February 5, 1997
6645 a txri[age place sc. = engiewcoo. cc 60 1 : 1 c 3=3 7Z. .9--54
TO: City of Ft.Collins Planning Staff and
STORMWATER UTILITY
FROM: Bill Veio, Manager
SOLITAIRE PROPERTIES,LLC
RE: OUTLINE OF OUR RESPONSES TO THE DEVELOPMENT ISSUES
RAISED AT THE PAST P & Z MEETING, DECEMBER 16, 1997
After reviewing the video tape of the December 16 meeting and after hearing Staff's concern in
our phone conversation this January, we have prepared this outline of the development issues
we intend to resolve. The issues are these:
1. Rainfall, Runoff, and Pond Depth
1.1 Rainfall and Runoff Patterns
1.2 The Groundwater Table Impact
2. The Functional Differences between the Detention vs. Retention Pond
2.1 Detention, Extended Detention, and Retention Ponds
2.2 Water Levels, Frequency, Open Space Use
2.3 Wetlands Transfer
2.4 Stormwater Quality & Best Management Practices
2.5 Overall Detention Pond Appearance, Dry -Wet Areas, Depth to Bottoms
2.6 Summary of The Detention Pond Benefits
3. Exhibits to Clarify Detention, Water Quality, and Open Space
3.1 Water Table Profile Pond Area --As Detention Pond -As Retention Pond
3.2 Pond Area in Plan View —As Detention --As Retention Pond
3.3 Rendering Showing Pond Functioning with Best Management Practices Identified
The following text is for your technical benefit and study. After reviewing the text, we would
like a meeting to discuss your comments and suggestions. The outline addresses what we believe
from an engineering, legal, and water quality perspective meets or exceeds the City of Ft. Collins
requirements for development approval. We would like to have your support for the Stormwater
Quality plan before scheduling a meeting with the neighboring property owners.
innovative ideas for industry since 1972
STORMWATER QUALITY
AND
MANAGEMENT CONTROL PLAN
Prepared for Scenic Views, 2nd Replat
City of Ft. Collins
Stormwater Utility
RMRI � �► ,
rocky mountain research institute
6645 e. ner¢age pmca so , engiewppp co 90111 J 003-721-0054
hex 303-721-0245 r bi,e 303-546.4540
marketing, real estate and economic consultants
FINAL SUBMITTAL
February 5, 1997
Rocky Mountain Research Institute
JAN-24-97 FRI 16:13 DEPT OF ATMO SCIENCE FAX N0, 970 491 8449 P.07
MEDIAN LENGTH OF TIME BETWEEN MOISTURE
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2.4.3 Conclusions Drawn From Stormwater Quality Management Practices
An effective strategy for reducing stormwater pollution loads is to use
multiple BMPs, including Non -Structural measures, source controls, and
Structural BMPs. These water quality facilities are designed to capture and
treat the 80% percentile storm runoff event. Capturing and treating this
volume is estimated to remove between 80% and 90% of the annual TSS
(total suspended solids) load. Multiple BMPs can provide complementary
water quality enhancement to achieve desired results. A multi -level approach
deals with many pollutant and runoff sources throughout a watershed and
shows that combining most effect BMPs in a series can be an effective
strategy to reduce pollutant loads being transferred to receiving waters by
stormwater. This is the BMPs Strategy that is being employed for stormwater
control and quality enhancement at Scenic Views.
2.5 The Overall Detention Pond Appearance, Dry -Wet Areas, and Depth to Bottoms
The Scenic Views Pond could be just as easily be called an Extended Detention Pond
as a Retention Pond. With the smaller permanent pond and wetlands being charged
by groundwater and periodic stormwater runoff, it is the calculation of the water
quality capture volume which determines the more accurate description of the basin.
The WQCV computations show a required volume of .42 ac-ft. This translates to a
permanent triangular -shaped wetlands pond of about 170'length by 130' width by 3'
deep. The remaining volume of 13.8 ac-ft is the DRY portion of the basin which
varies in depth from 9' to 12' and will handle 2 times the 100-yr storm. The exhibits
specified in Section 3 of the outline are being prepared for the neighbors and the Final
Plat hearing. You will receive copies for review when they become available. The
purpose of the exhibits is to show how the pond will look in Plan and Profile view,
and how the BMPs work together on the site.
2.6 Summary of The Detention Basin Benefits
The above storm drainage basin will handle all on -site runoff for the 100-year storm,
plus has additional capacity to hold the off -site runoff volume from CSU and the
northern flows for the 100-yr storm. This excess storage capacity insures enhanced
stormwater quality to the downstream users. Of major importance is that Plum Basin
downstream property owners and homeowners should never again be flooded in the
5-yr, 10-year, or 100-yr storm event. This basin improvement is estimated to save
downstream residents over $2,800,000 in potential flood damages over the next 50
years.
3. Exhibits to Clarify Detention, Water Quality, and Open Space
3.1 Water Table Profile Duplex Area --Now vs. Underdrain
3.2 Water Table Profile Pond Area --As Detention Pond -As Retention
3.3 Pond Area in Plan View --As Detention --As Retention
3.4 Rendering Showing Pond Functioning with Best Management Practices Identified
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contaminants and can require from 12 to 40 hours to settle out of suspension.
Extended detention allows smaller particles to agglomerate into larger ones,
and for some of the dissolved and liquid state pollutants to adsorb to
suspended particles, thus removing a larger portion of them through
sedimentation.
Filtering. Here particulates are removed from water by filtering. Particles
attach to small diameter collectors such as sand, pebbles, or gravel.
Infiltration. Pollutant loads in surface runoff are removed or reduced as the
water infiltrates or percolates into the ground. Particulates are removed at
the ground surface by filtration through the vegetation and soil, while
soluble constituents are also adsorbed into the soil, at least in part.
Biological Uptake. Plants and microscopic animals require soluble
constituents such as nutrients and minerals for growth while are found in
stormwater runoff. Soluble constituents are ingested or taken up from the
water and concentrated through bacterial action and phytoplankton growth.
In some instances plants could be harvested to remove the constituents
permanently. In addition, certain biological activities can reduce toxicity of
some pollutants and/or possible adverse effects on higher aquatic species.
Pollutant Removal Efficiencies
Table 4 presents the ranges of pollutant removal efficiencies which are
expected using the Structural BMPs with the above processes.
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Grass Buffer Strips
10-20
0-10
0-10
0-10
n.a.
Grass -Lined Swales
2040
0-15
0-15
0-20
n.a
Extended Detention Pond
50-70
10-20
10-20
30-60
50-90
(Dry)
Retention Pond (Wet)
60-95
0-80
0-80
0-70
n a.
Constructed Wetlands
40-50
10-60
0-20
50-60
n.a
Source: Observed BMPs reported for Extended Detention and Retention Ponds by Environmental Protection Agency
(1983), Grizzard (1982), Whipple and Hunter (1982) and Urban Drainage and Flood Control District, Metro
Denver (1992). Wetland data from USGS for all constituents except Total-P; Lakatos and McNemer (1987) for
Total-P as reported by Urban Drainage Flood Control District, Metro Denver (1992).
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The HOA will check the retention pond pumps prior to the start of the
rainy season, and during major storms. In the event of a pump
malfunction, possible repairs will be made, and the ditch company and
city stormwater department notified, if repairs are unsuccessful, and a
storm is occurring or forecasted.
4. Water Quality Retention Pond (Wet Pond)
Retention ponds are designed for a 40-hour drain time above the
permanent pond because the sedimentation process is more efficient and
some mixing and dilution between a permanent dry weather pool and
storm runoff occurs. The wet pond also provides for treatment between
storms which provides a long period of time for fine particles to settle
out and for biological activity to occur. Outflow occurs above the
bottom of the basin allowing sediment to be trapped below the outlet
with sedimentation continuing after the captured surcharged volume is
emptied. A continuing source of water flow is needed to support the
permanent pond (WQCV). Refer to Pond Plan in the Utility drawings.
5. Constructed Wetlands
Wetland basins are designed to drain the water quality capture
volume (WQCV) in no less than 24 hours, thereby providing for some
biological uptake during the contact with wetland media. The depth of
the WQCV is under 2'. The permanent pool area is divided between
free water surface area (30% to 50%) which will be 2' to 4' deep ... and
the wetland zones with vegetation (50% to 70%) which are typically 6"
to 12" deep. A skimmer device is installed on the pond outlet about
one-half the depth below the permanent water surface and rises to the
maximum capture volume depth. The full WQCV should be above the
permanent pool level. Refer to the Landscape Plan and Utility Drawings
for the wetlands area design.
6. Sand, Gravel and Other Filters, Skimmer, Perforated Raised Pipe
These are other BMPs that work in conjunction with the above Structural
BMPs which enhance the stormwater quality before it enters the canal
or other waterways.
Effectiveness of BMPs Measures
Runoff Pollutants can be grouped into two categories: particulate and soluble.
Particulates are considered larger than .4 microns in diameter. In many cases,
constituents, such as metals and oxygen demand compounds, become
adsorbed to particulate matter. If the particulate matter is removed, so are
the adsorbed or attached constituents. A combination of the following basic
pollutant removal processes is used to remove pollutants at Scenic Views:
Sedimentation is the process of particulate matter settling out of stormwater
runoff. Smaller particles under 60 microns in size (fine silts and clays) can
account for 80% of the metals in stormwater attached or adsorbed with other
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Structural BMPs to be Used at Scenic Views
The following Best Management Practices are being employed for the Scenic
Views development:
1-2 Irrigated Grass Buffer Strips and Grass -Lined Swales.
Adjacent to all buildings and parking areas are large patches of grass
to which roof top drains will direct storm runoff. Passing through the
grass and vegetation slows the storm runoff peak and promotes
pollutant fallout prior to the water entering the stormwater drains.
Grass lines Swales direct stormwater flow, contribute to lowering the
peak flow, and reduce pollutant loads into the stormwater basin. A
swale will occur in the detention pond bottom to direct water flow to
the wetlands. This wetlands bottom channel will be gravel lined and
filter particulates.
NOTE: Healthy grass can generally be maintained without using
fertilizers because runoff from lawns and other areas contain the needed
nutrients. Periodic inspection is needed in the first few years to identify
any problems areas and to plan for long-term restorative maintenance.
3. Water Quality Extended Detention Basin (Dry Basin)
Extended detention basins are designed to drain their brim -full volume
in about 40 hours through a perforated riser pipe to remove a significant
portion of the particulate pollutants found in the stormwater runoff.
Soluble pollutant removal is enhanced by providing the small wetland
marsh or ponding area in the basin's. bottom to promote biological
uptake. The basin is considered dry because it is designed not to have
a large permanent pool of water. The flood detention volume is
provided above the water quality capture volume (WQCV)'of the basin.
No more than 50% of the WQCV will be released in 12 hours. The
extended detention basin reduces peak runoff flow rates into the canal
and prevents periodic flooding of properties downstream while
improving water quality and providing recreation and open space
opportunities. The basin is effective in removing particulate matter and
associated heavy metals and other pollutants.
On -Going Monitoring of the Stormwater Outfall
The HOA will be responsible for the drainage basin maintenance and
will have instructions for using bio-degradable pesticides, debris
removal, grass mowing, and wetlands monitoring. The HOA will keep
a log of basin grounds maintenance including pumps, recycling pickups,
resident attendance at on -site ecological seminars, and use of outdoor
litter disposal conveniences. Annually in May, July, August, and
September the HOA will monitor pond discharge by water sampling
and send results to an independent lab for content analysis. Results will
be evaluated by the HOA Board annually to track the effectiveness of
the Best Management Practices program.
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activities by far exceed the quantities from urban areas. Establishing
and maintaining landscaping and vegetation in existing urban areas can
assist in reducing stormwater runoff rates and volumes, sediment loads,
and pollutants associated with sediment from entering streams and
lakes. Vegetation acts to reduce raindrop impact on soil, slows runoff
rates, and encourages infiltration of precipitation into the soil.
Pollutants, such as metals, nutrients, and bacteria that are attached to
sediment will also be removed. The overall volume of runoff from a
vegetated area is less than from an area of bare soil. Although bare soil
will also allow some infiltration, its surface has a tendency to seal and
erode. The eroded soils are a source of sediment transport to the
receiving waterway.
The landscape plan for the site contains over 100 trees, bushes, shrubs,
and several acres of grass vegetation. The landscaping and vegetation
will reduce the sediment load from existing conditions and enhance
stormwater quality. Maintenance of the planted areas will be the
responsibility of the HOA.
Advantages of Structural BMPs
Reduced runoff, particulate removal, and some measure of flood control
are the principal benefits of Structural BMPs. Pollutants are removed
by adsorption, settling, precipitation, infiltration, filtration, and
biological activity.
The advantages are:
* Enhanced stormwater runoff quality
* Can reduce runoff volumes through infiltration and interception
* Can reduce peak rates of runoff, especially for smaller storms, by
capturing and slowly releasing urban runoff
* Can be constructed first and then used to control erosion and
sedimentation during site construction
* Can be combined with other municipal or public uses such as
active and passive recreation, open space, and wildlife habitat
* Can sometimes integrate BMPs into site landscaping to supplement
irrigation of vegetation
* Can be combined with drainage and flood control objectives at
incremental costs to minimize and control downstream flooding
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Other on -site actions that will be taken to improve resident and visitor
awareness and personal responsibility for stormwater quality:
* Distribution of the Irrigation Ditches brochure in the rec center, sales
offices, and on the bike and walking paths along the canal
* DON'T LITTER signs in open space and along canal
* Neighborhood clean-up day for parks, bike paths, open areas
* Pet Waste disposal bag containers along paths and park areas
* Waste containers distributed throughout the open spaces and walks
4. Guidelines for Proper Use of Pesticides, Herbicides, and Fertilizers
Pesticides, herbicides, and fertilizers are chemicals used in landscape
maintenance. Pesticides are used for insect control, herbicides for weed
control, while fertilizers are used for the growth and greening of grass.
Pesticides and herbicides are toxic to aquatic life at low concentration,
and fertilizers can be toxic at high concentrations. Fertilizers tend to
promote algae growth which can deplete dissolved oxygen for fish and
other aquatic organisms. -
The rate and timing of the use of pesticides, herbicides, and fertilizers
are important to minimize potential transport by stormwater runoff.
Overapplication and overspraying onto impervious areas needs to be
avoided as well as too frequent or excessive use. Following
manufacturer's recommendations can prevent most of the surface water
contamination being attributed to their use. With the HOA"in control of
all open space applications, manufacturer's specifications can be
followed.
5. Illicit Discharge Controls
Educating residents and visitors about illegal dumping practices, about
the potential hazards to public health and the environment, and
encouraging the immediate reporting of spills can create a citizen
sensitivity to deter illicit dumping.
Controlling public automobile access to the neighborhood would go a
long way to prevent the dumping of trash, refuse, and fluids or toxic
substances into the canal. Controlled access to the neighborhood was
part of the original design to presented to the city planning staff, but
was refused "as an undesirable neighborhood element".
6. Landscaping and Vegetation Practices
Soil erosion and transport from urban areas produces only a fraction of
total sediment arriving at streams and waterways. Agricultural
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Non -Structural BMPs Used at Scenic Views
The following Best Management Practices are being employed for the Scenic
Views development:
1. Preparation of this Storm Water Quality Control Plan which states
water quality control objectives, the description of stormwater quality
management practices, contains exhibits and drawings showing the
structural BMPs, the hydrological and hydraulic calculations
documenting sizing and stability of drainage features, and descriptions
of maintenance responsibilities and access.
2. Preparation of an Erosion Control Plan
This Plan is a part of the Final Drainage Plan and Utility drawings which
have been submitted to city staff. The objective of the Plan is to mitigate
the potential for soil erosion and to control sediment movement during
the construction process until final landscaping and stormwater quality
measures are effectively in place.
3. Proper Disposal of Household Waste and Toxins
The developer and the Homeowners Association will create a resident
and visitor information program that teaches the proper disposal of
household waste, litter, pet waste, yard waste, used oil, and toxic waste.
Facilities for proper disposal will be provided throughout the
development. Neighborhood newsletters, HOA monthly billing inserts,
recreation center bulletin boards, the HOA covenants, and periodic
HOA meetings will reinforce these policies. Proper disposal of
household waste and toxics can reduce the deposition of solids,
organics, nutrients, oxygen -demanding substances, solvents, caustics,
paints, automotive fluids, toxic substances and fecal material on the land
and reduce their presence in the stormwater reaching receiving waters.
Improper disposal of used oil and automotive fluids causes receiving
waters to be contaminated with hydrocarbons and residual metals that
can be toxic to stream organisms. Used oil and other petroleum
products can be recycled. Information on the location of recycling
centers, the benefits of recycling, prevention of fluid leaks, and the
importance of proper disposal for improving stormwater quality can
reduce the amount of oil and used automobile fluid reaching receiving
waters.
Through an on -site communication program residents and visitors will
be alerted about their everyday use of toxic wastes: paint, solvents,
putties, cleaners, waxes, polishes, oil products, aerosols, acids, caustics,
pesticides, herbicides, and certain medicines or cosmetics. Seminars will
present non -toxic, safe, biodegradable product alternatives and discuss
proper disposal points within the community.
Rocky Mountain Research Institute
h. The irrigation company is willing to allow the discharge into the ditch
after peak flow periods of a storm, because of the benefits cited above.
2.4.2 Stormwater Quality with Development —Best Management Practices
Urban stormwater runoff contains a variety of constituents that originate
from a number of different sources. To reduce the concentrations and the
loads that would reach the irrigation canal or other receiving waters, Best
Management Practices (BMPs) have been suggested by EPA, other Federal
and State Agencies, and professionals who deal with stormwater.
There are two categories of BMPs, both of which will be utilized in
improving stormwater quality at Scenic Views:
Non -Structural BMPs include pollution prevention and source control BMPs.
Structural BMPs include facilities constructed to passively treat stormwater
runoff before it enters the canal or other receiving waters.
Advantages of Non -Structural BMPs
Non-structural BMPs prevent or limit the entry of pollutants into stormwater
at their source. Prevention is desirable and can be cost effective because it
avoids pollution in the first place and thereby reduces the amounts that need .-.
to be removed by subsequent treatment. The advantages of Non -Structural
BMPs are:
* The quality of stormwater runoff is improved
* The volume of sediment, debris, and other pollutants deposited in
receiving waters is reduced
* The operation and maintenance of structural controls is reduced
* There are benefits to air quality, ground water quality, and waste control
* Open space and wildlife habitat is enhanced
* Public awareness of water quality problems is heightened and personal
involvement in solutions happens
* Public awareness of stormwater quality issues increases
* Most require only a modification of existing practices, are simple to
understand, and make good sense
* Implementation can occur rapidly
Rocky Mountain Research Institute
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