HomeMy WebLinkAboutASPEN DENTAL - FDP - 1-09/A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTI
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VICINITY MAP
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APPENDIX
Vicinity Map
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NORTHERN
Final Drainage Report
Aspen Dental
References
1. Drainage Criteria Manual, Urban Drainage and Flood Control District, Wright
Water Engineers, Inc., Denver, Colorado, Updated April 2008.
2. City of Fort Collins. Storm Drainage Criteria Manual and Construction
Standards, City of Fort Collins, May 1984.
3. Final Drainage Report for Speights PUD, Northern Engineering Services, Inc.,
Fort Collins, Colorado, June 1992.
4. Drainage and Erosion Control Report for Sunstone Mixed -Use, Ayres
Associates, Fort Collins, Colorado, September 2001.
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NORTHERN Final Drainage Report
Aspen Dental
- ENGINEERING As p
Basins B1 and B2 have a water quality requirement of 0.006 ac-ft, which falls
below the capacity of the existing structure.
8.0 Temporary Erosion Control
Temporary erosion control measures have been provided on the grading and
erosion control plan which will minimize sediment leaving the project site during
construction. Silt fence will be placed along the north and western perimeter of
the site to minimize sediment disturbance on -site. Wattles will be placed at all
curb cut locations in order to minimize sediment entering the receiving storm
sewer system. A vehicle tracking control pad will be placed at the southeastern
entrance to the site, to reduce the amount of sediment tracked off -site.
9.0 Conclusions
The proposed project will comply at final design with drainage criteria outlined in
the City of Fort Collins Storm Drainage Design Criteria. Overall, the drainage
system proposed within this report provides adequate conveyance, detention and
water quality enhancement for the developed stormwater runoff for the site. Care
has been taken to minimize any negative impacts on the downstream receiving
waters.
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NfFzi ENGINEERING
On -site Pond Information
Final Drainage Report
Aspen Dental
Basin
WQCV
WQ
Detention
Water Detention
Release
Description
Impervious-
(ft3)
WSEL
Volume
Surface
Rate
ness
ft3
( )
Elevation
(cfs)
Detention/Water
68.6%
332
4944.19
314
4945.01
1.58
Quality Pond
As shown above the 100-year water surface elevation in the pond is 4945.01,
which is at the same elevation as the. high point in the northern driveway to the
animal clinic. The drive will serve as an emergency overflow for the pond. Flow
from this point will travel north, ultimately reaching the Sunstone swale located
north of the Clinic site. The available freeboard in the pond is approximately
0.30', with the lowest top of wall elevation being 4945.30. A variance will be
requested to allow for the freeboard requirement of 1.0' to be waived. As
designed, in the 100-year condition there will be 0.40' of ponding seen in the
parking lot area. This falls below the acceptable limit of 1.0' in the 100-year
condition.
Basins B1 and B2 will discharge to the Sunstone Mixed Use detention pond
located to the southeast of the site. The existing pond was analyzed to calculate
the excess volume in the pond for use by the Aspen Dental site. The as -built
detention ponds grading certification done by Ayres and Associates in April of
2004 were used as a basis for the analysis. The pond certification states that the
detention volume requirements were met at an elevation of 4942.44, with a
volume of 1.093 acre-feet. The pond spillway, located in the drive south of the
Sunstone pond, was surveyed at with a flowline elevation of 4942.43 and a lip of
gutter elevation of 4942.51 (inflow curb and gutter).
The intent of this project is to replace the portion of the curb and gutter along the
northern edge of the road, which is the lowest point of the emergency spillway for
the Sunstone pond. When the portion of curb and gutter is replaced with an
outfall section or a flat section, the spillway elevation will be increased to a
minimum elevation of 4942.51. This translates into an additional 1791 cubic -feet
of available volume in the pond. The additional volume required for the 0.166
acres flowing to the Sunstone pond was calculated to be 1551 cubic -feet. The
Sunstone outlet structure was not modified, the additional depth of water on the
existing structure was calculated to be 0.06'. This resulted in an additional
release rate of 0.09 cfs.
Water quality for Basin B1 will also be included in the Sunstone Pond. The water
quality plate elevation for the Sunstone Pond was designed at 4939.10. From
the as -built survey (Ayres), the available water quality volume at that elevation is
0.141 ac-ft. The Sunstone report lists a required water quality volume of 0.12 ac-
ft for the site. This results in an excess in 0.021 ac-ft of volume for water quality.
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IFinal Drainage Report
NORTHERN 9 p
N ENGIMEERIMG Aspen Dental
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Detention for the site has been included with the water quality pond located on -
site. The detention and water quality portions of the pond were designed for the
on -site area only. Both off -site basins will be allowed to be released undetained
through the existing pipe system, flowing to the north. The existing pipe system
was modeled using an assumed downstream water surface elevation of 4941.90.
This value was agreed upon by Northern Engineering and City Staff, as a
conservative estimate. The downstream hydraulic grade line is halfway between
the top of pipe elevation of 4939.90 (24" invert elevation = 4937.90) and the rim
elevation of 4943.90. The Aspen Dental site will contribute runoff to the existing
storm pipe system within 5-10 minutes. The assumption is that the Aspen site
will beat the existing swale/storm line peak by a large time margin. Below is a
summary of the flows to the existing storm system.
100-
Area
year
Accumulated
Description
Served
Flow to
Pipe Flow
Comments
(ac)
Pipe
(cfs)
cfs)
Off -site Basin
0.094
0.82
OS-1
Off -site Basin
0.400
1.77
OS-2
On -site Basins
0.284
1.58
0.82+1.77
On -site Basin release rate
A1,A2,A3,C1
+1.58= 4.17
matches historic release rate
(to on -site
(Speights Basin D2)
and
Countryside
1.44
4.17+1.44=
Flow taken from Speights PUD
Animal Clinic
5.61
flow to existing inlet
The release from the water quality/detention pond will be 5.61 cfs, as shown
A above. The off -site basins will contribute 4.03 cfs of that value (undetained flow
from OS-1, OS-2 and existing Countryside Animal Clinic inlet), while the on -site
basins will be released at the historic Speights PUD Basin D2 flow value of 1.58
cfs. An 8" orifice will be placed at the outlet structure and will act as the
controlling factor in the pond release for the 100-year storm. Below is a
summary of the detention and water quality pond.
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(NORTHERN
ENGINEERING
Final Drainage Report
Aspen Dental
regarding the pond can be referenced in the detention/water quality section of
this report.
Basin OS-1
Basin OS-1 consists of a small area north of the site, on the Countryside Animal
Hospital site, which drains onto the property. The basin contains the southern
portion of the Animal Hospital parking lot area, as shown on the drainage plan.
The drainage basin boundary for this area was verified with field visits, and
shown approximately on the drainage plan. The imperious value for this basin
was calculated from the existing site layout. Drainage from this basin travels
overland into Basin A3. Basin A3 drains to a low point along the eastern curb
line, where a curb cut has been provided, at Design Point A3. The drainage from
the basin will discharge into the proposed detention/water quality pond, located
at the eastern edge of the site. Flows from the basin will be allowed to pass
through the pond undetained, per conversations with the City of Fort Collins
Stormwater Staff.
Basin OS-2
Basin OS-2 consists of the area located east of the site, which drains onto the
property. The basin incorporates drainage from the back yards of the residential
properties directly east of the site. The drainage basin boundary for this area
was outlined in the "Speights PUD" drainage report, indicated as Basin D2.
Basin D2 of the Speights report includes the Aspen Dental clinic site area as well
as the residential area, for a total basin area of 0.85 acres. The area for Basin
OS-2 was calculated by subtracting the Aspen Dental site area of 0.45 acres
from the Speights Basin D2 area of 0.85 acres, for a total of 0.40 acres. The
imperious percentage for the site was taken from the original Speights Report,
matching that of Basin D2. The Speights Basin D2 information can be found in
Appendix B. For the runoff time of concentration calculations, a time of 5
minutes was used as a conservative estimate. The flow from Basin OS-2 will
travel overland, following historic drainage patterns to a proposed inlet located in
sump at the eastern edge of the site. Flows from the basin will be discharged
directly into the existing storm system undetained, per conversations with the
City of Fort Collins Stormwater Staff.
7.0 Proposed Detention and Water Quality
Water quality for the site will be provided on -site through the use of a traditional
water quality structure, with an orifice plate designed to drain the pond within a
40-hour period. The water quality pond will be designed in accordance to
standards issued in the Urban Drainage and Flood Control Manual 3. The water
quality system will allow water to be filtered and discharged following historic
drainage patterns.
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NORTHERN Final Drainage Report
Nt-. ENGINEERING Aspen Dental
Basin A2
Basin A2 consists of the northern half of the building roof area. Downspouts from
the roof are located on the north side of the building. Drainage from this basin
travels to a drainage swale provided in the grassed area north of the building.
Drainage from the swale travels to curb cut A3-1. Ultimately flow travels
overland to a low point along the eastern curb line, where a curb cut has been
provided. The drainage from this basin will discharge into the proposed
detention pond, located at the eastern edge of the site.
Basin A3
Basin A3 consists of the northern and eastern portions of the site. The
impervious value for this basin was calculated from the proposed site layout.
Drainage from this basin travels overland to a low point along the eastern curb
line, where a curb cut has been provided. The drainage from this basin will
discharge into the proposed detention pond, located at the eastern edge of the
site.
Basin Bi
Basin B1 consists of the western half of the building roof area. Downspouts from
the roof area are located on the west side of the building. Drainage from this
basin travels beneath sidewalk chases B2-1 and B2-2, then overland to the
eastern curb line. The southern portion of the eastern curb line slopes to the
south, where drainage is discharged into the Sunstone detention pond. The
Sunstone pond is located southeast of the site, and will intercept drainage from
Basins B1 and B2.
Basin B2
Basin B2 consists of the southern half of the site and includes the southern
parking lot area. The impervious value for this basin was calculated from the
proposed site layout. Drainage from this basin travels overland to an existing
pan, which flows to the Sunstone Detention Pond. Historic drainage from
Speights PUD Basin H1 is 0.55 cfs with a basin area of 0.26 acres. Basins B1
and B2 have a combined area of 0.166 acres and a developed runoff of 1.65 cfs.
The total area of land draining to the pond is less than historic, however total
runoff has been increased due to the developed impervious condition. Upon
discussions with the City of Fort Collins Stormwater Staff, allowing runoff to travel
south to the Sunstone Detention Pond is acceptable, providing the total area
values fall below the original historic value seen in the Speights report.
Basin C1
Basin C1 consists of the detention/water quality pond area located on the eastern
edge of the site. The basin contains a traditional water quality structure, with a
40-hour release time. Detention volume for the site has been added to the water
quality volume, per the City of Fort Collins requirements. Additional information
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NORTHERN Final Drainage Report
gLL en Dental As
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5.0 Proposed Development
The proposed project site consists of a single -story commercial building to be
used as a dental clinic. Surrounding the proposed building will be a parking lot
area and detention/water quality pond. The parking area will also provide a
traffic connection between the veterinary clinic and the commercial buildings to
the south. The site is 0.449 acres, and is located on Lot 7 of the Speights PUD
subdivision. The USDA Soil Conservation maps indicate the site lies within soil
hydrologic group C and is classified as Nunn Clay Loam.
6.0 Proposed Drainage Plan
The drainage plan for the project is intended to match historic drainage patterns
for the site. Storm runoff for the northern portion of the site will travel overland to
the eastern boundary of the parking lot area. A curb cut will be placed in a sump
location along the eastern curb line. Drainage will flow from the curb cut into the
water quality and detention pond. An orifice plate at the outlet structure will act
as the water quality control component, allowing the pond to drain within a 40-
1 hour time period. Larger flows will overtop the water quality plate and be
discharged into the existing 15" storm line. An orifice plate will not be required to
regulate larger storm event flows, the existing 15" storm line will be the
controlling release factor. The northern portion of the site falls within Basin D2 of
the Speights PUD drainage report, which discharges north through the existing
pipe. The pipe drains to the Sunstone Swale located north of the Animal Hospital
site.
The southern portion of the site will flow to the south, to the detention pond
constructed with the Sunstone Mixed Use Development. The southern portion
of the site falls within Historic Basin H1 (Speights PUD), which drains to the
south. Below is a description of the proposed basins for the site and their
drainage patterns.
Basin Al
Basin Al consists of the eastern half of the building roof area. Downspouts from
the roof are located on the east side of the building. Drainage from this basin
travels through sidewalk chase A3-3, then overland to a low point along the
eastern curb line, where a curb cut has been provided. The drainage from this
basin will discharge into the proposed detention pond, located at the eastern
edge of the site.
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ENGINEERING
4.0 Historic Drainage and Major Drainage Basin
Final Drainage Report
Aspen Dental
Historic drainage patterns are outlined in the Speights PUD Drainage Report
provided in Appendix B. The site is included in the Speights historic drainage
Basin D2, Design Point 2. Basin D2 consists of a residential area within the
eastern portion of the basin, with the remaining portion of the site modeled as
undeveloped. The overall C value for the undeveloped basin was shown to be
0.27 in the Speights Drainage Report. Basin D2 is drains to an area inlet located
in a sump condition on the Aspen Dental project site. Flow to the existing inlet
was modeled as 0.45 and 1.58 cfs for the 2—year and 100-year storms
respectively. The existing storm inlet drains to a 15-inch diameter storm pipe
which drains to the north. The storm line intercepts drainage from the
Countryside Animal Hospital site via an area inlet located in the northeast corner
of the Animal Hospital property. The existing 15" storm line ultimately flows north
to an existing 24" storm line which parallels the Sunstone drainage swale. The
drainage swale is located north of the residential homes on Sunstone Drive. The
swale and pipeline flow to the east to an existing detention pond constructed with
the previous infrastructure improvements for the Sunstone development.
Existing calculations from the above mentioned reports are shown in Appendix B.
The project site is located within the Fox Meadows major drainage basin. There
are no floodplains associated with the project.
a: INORTHERN Final Drainage Report
ENGINEERING Aspen Dental
1.0 Scope
This preliminary drainage report has been prepared for the proposed Aspen
Dental site, located at 3838 South Timberline Road in Fort Collins, Colorado.
This report is intended to provide information regarding existing and proposed
storm drainage including:
• Historic drainage patterns for the site, including quantities of flow to the
existing storm drainage system.
• Proposed drainage patterns for the site.
i• Proposed on -site water quality, and off -site detention for the site.
2.0 Design Criteria and References
Drainage criteria outlined in the City of FortCollins Storm Drainage Design
Criteria (SDDC) has been referenced in this study, and will be complied with at
final design.
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- The Rational Method has been used to estimate peak discharge rates in the
initial and major storm events for proposed conditions in this study, and will also
be used at final design to estimate peak discharge rates. The initial and major
storm events are considered to be the 2-year and 100-year storm events,
respectively.
Runoff coefficients and rainfall values utilized in the Rational Method are
consistent with the City of Fort Collins SDDC and will also be utilized at final
design.
3.0 Site Location and Description
The project site is located on the east side of Timberline Road between Caribou
Street and Horsetooth Road, in Fort Collins, Colorado. The Aspen Dental site
lies on Lot 7 of the Speights PUD subdivision. The Aspen Dental site is bounded
on the north by the Countryside Animal Hospital, to the south by the Reflections
Medical Spa, to the west by Timberline Road, and to the east by a residential
neighborhood. The major east -west running street is Horsetooth Road located to
the north of the development and Caribou Drive to the south.
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TABLE OF CONTENTS
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1.0
Scope
1
2.0
Design Criteria and References
1
3.0
Site Location and Description
1
4.0
Historic Drainage and Maior Drainage Basin
2
5.0
Proposed Development
3
6.0
Proposed Drainage Plan
3
7.0
Proposed Detention and Water Quality
5
8.0
Temporary Erosion Control
8
9.0
Conclusions
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1 APPENDIX
APPENDIX A - VICINITY MAP
APPENDIX B - PREVIOUS DESIGN REPORT INFORMATION
APPENDIX C - RATIONAL CALCULATIONS
APPENDIX D - DETENTION AND WATER QUALITY POND CALCULATIONS
APPENDIX E - STORM SEWER CALCULATIONS
APPENDIX F - MISCELLANEOUS CALCULATIONS
MAP POCKET
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NORTHERN
J14E I ENGINEERING
ADDRESS: PHONE: 970.221.4158
200 S. College Ave. Suite 100 Northern
E N
Fort Collins, CO 80524 FAX: 970.221.4159 orthernEngineering.com
iCity of Fort Collins Stormwater Utility
700 Wood St.
Fort Collins, CO 80521
May 5, 2009
RE: Final Drainage Report
Aspen Dental
Dear Stormwater Staff:
Northern Engineering Services, Inc. is pleased to submit this Final Drainage
Report for the Aspen Dental Clinic site in Fort Collins, Colorado. In general, this
report serves to outline the overall drainage design for the site in accordance to
the concepts outlined in the Speights PUD Final drainage report, prepared by
Northern Engineering in June of 1992.
We understand that review by the City is to assure general compliance with
standardized criteria contained in the City of Fort Collins Storm Drainage Design
Criteria.
If you should have any questions or comments regarding this report, please feel
free to contact us at your convenience.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Cinde Welken, PE
Design Engineer
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Final Drainage Report
for
Aspen Dental Care .
3838 South Timberline Road
Fort Collins, CO
May 5, 2009
Prepared for:
Aspen Dental
Prepared By:
M INORTHERN
ENGINEERING
200 South College Ave., Suite 100
Fort Collins, Colorado 80524
Phone: (970) 221-4158 Fax: (970) 221-4159
Project Number: 431-001