HomeMy WebLinkAboutPVH HEALTH SYSTEM, HARMONY CAMPUS, 2ND FILING, INFRASTRUCTURE - PDP - 32-98D - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTF
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proposed detention ponds. The combination of on -site street capacities and the on -
site storm sewer system will provide for the developed flows to reach the proposed
detention ponds. The sizes, locations and release rates of these ponds will allow the
Poudre Valley Hospital site to develop in conformance with the McClellands Basin
Drainage Master Planning concepts accepted by the City of Fort Collins.
If groundwater is encountered at the time of construction, a Colorado Department of
Health Construction Dewatering Permit will be required.
C. Storm Water Quality
The sediment basin traps proposed within the on -site detention ponds are excellent
ways to allow storm water pollutants an opportunity to be filtered out of the storm
water as the storm water carries the pollutants across the site. Periodic maintenance
may be required to remove sediment deposits as they accumulate in the on -site
detention pond.
D. Erosion Control Concept
The proposed erosion control concepts adequately provide for the control ofwind and
rainfall erosion from Poudre Valley Hospital. Through the construction of the
proposed erosion control concepts, the City of Fort Collins performance standards
will be met. The proposed erosion control concepts presented in this report and
shown on the erosion control plan are in compliance with the City of Fort Collins
Erosion Control Criteria.
REFERENCES
1. Storm Drainage Design Criteria and Construction Standards by the City of Fort
Collins, Colorado, May 1984, Revised January 1997.
2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins,
Colorado, January 1991, Revised January 1997.
3. McClellands Basin 100-Year Master Plan Update, by Icon Inc., Fort Collins,
Colorado, March 2000.
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V. STORM WATER QUALITY
A. General Concept
The State of Colorado requires Stormwater Management Plans as part of their permit
process. The Poudre Valley Hospital site development is anticipating construction
beginning in January of 1999. Therefore this study has sought to find various Best
Management Practices for the treatment of storm water runoff that could be
implemented in the construction phase of the project.
B. Specific Details
Best Management Practices (BMP) for the treatment of storm water runoff has
been 'incorporated into the design for this project. This includes extended
detention, grass lined swales and an irrigation pond that will trap sediment. Also,
best management practices will be used during construction.
VI. EROSION CONTROL
A. General Concept
At this time no erosion control calculations have been completed. These will be
completed with each subsequent Filing. Revisions to this report and the Utility
drawings will be done at that time.
The Poudre Valley Hospital site lies within the Moderate Rainfall Erodibility Zone
and the Moderate Wind Erodibility Zone per the City of Fort Collins zone maps.
The potential exists for erosion problems during construction, and after construction
until the disturbed ground is re -vegetated or paved
VII. CONCLUSIONS
A. Compliance with Standards
All computations within this report have been completed in compliance with the City
of Fort Collins Storm Drainage Design Criteria. The City of Fort Collins Storm
water Utility will not maintain the on -site storm drainage facilities within the Poudre
Valley Hospital site. The owners of the Poudre Valley Hospital site will maintain
their on -site storm drainage facilities on a regular basis.
B. Drainage Concept
The proposed drainage concepts presented in this study and shown on the final utility
plans adequately provide for the transmission of developed on -site runoff to the
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Detention Ponds
Detention Pond 393 presently is constructed as a detention pond as well as an
irrigation pond and has a total storage capacity of approximately 7 acre-feet, where
2.5 acre-feet of this storage has been allocated for detention storage. The pond is
comprised of two ponds with an equalizing pipe connecting them. In order to
maintain water in the pond for irrigation purposes, the outlet structure will be placed
above the irrigation high water surface. As with the outlet structure for Pond 394,
there is a 10-year and 100 year staged release rate which outlets into a temporary
trapezoidal swale that conveys the flows to the existing grass -lined drainage (SWMM
model Conveyance' Element 39) ditch at the south boundary of the site. Similar to
Detention Pond 394, an emergency overflow spillway was designed for this pond
with its elevation equal to the 100 year WSEL.
At final build out, detention pond 393 will be relocated to the southeast corner of
Filing 2 (Pond 593) and will provide 18.71 acre-ft of storage, in accordance with the
SWMM model and water quality capture volume calculations. Pond 593 will
discharge at the staged release rate of 0.20 cfs/acre for the 10-year design storm and
0.50 cfs/acre for the 100-year design storm, in accordance with the Master Plan for
the McClelland's Basin. Pond 593 will have a 241' emergency overflow weir, which
will convey flows south and into the existing channel on the south side of the site. At
this time it is not certain how the construction of this detention pond will be phased.
Detention Pond 394 has a storage capacity of 2.3 acre-feet. The outlet structure
allows for a 10-year and 100-year staged release rate, which releases the detained
flows into the existing grass -lined drainage ditch (SWMM model Conveyance
Element 39) at the south boundary of the site. The elevation of the spillway is equal
to the 100-year water surface elevation (WSEL). The allowable release rates were
determined using the requirements from Master Plan for the McClellands Basin: 0.20
cfs/acre for a 10-year design storm and 0.50 cfs/acre for a 100-year design storm.
SWMM Model
In order to analyze the detention ponds within the Poudre Valley Hospital Phase I
development, the Urban Drainage Districts SWMM routing computer model was
used. The updated McClelland Creek Master Drainage Plan Update (March 2000)
was modified to reflect the proposed condition for Filing 2. The entire
undeveloped are was considered 80% impervious.
The SWMM models and data are located in Appendix C.
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Basin 42
Basin 42 conveys its flows east toward design point 42, while joining with that of
basins 3, 4, 30-39, 50-53, and 101-104. Two, 2' x 6' concrete box culverts deliver
the 197.1 cfs flow (100-Yr) to pond 593 (basin 43).
Basins 48 and 49
Basins 48 and 49 convey storm flows south down Snow Mesa Drive, where two, 15'
Type 13 Inlets (on grade) capture the flows at design points 48 and 49. Once
captured by the inlets, the flow from basins 48 and 49 is conveyed south in 18" and
24" RCP, and finally east into pond 593.
Basins 40 and 41
Basins 40 and 41 convey flows south along Snow Mesa Drive, where two, 10' Type
13 Inlets (on grade) capture the flows at design points 40 and 41. Once captured by
the inlets, the flow from basins 40 and 41 is conveyed east, via 15" RCP, into pond
593.
Basins 105,107,109, 46, and 47
Basins 105, 107, and 109 convey their flows southeast and into Swale C/CS261,
located along the eastern boundary of the site. Swale C/CS261 conveys the flows
from these basins south towards design point 109, where two, CDOT Type D Inlets
(in sump) capture the combined flow from basins 105, 107, and 109. Meanwhile,
basins 46 and 47 convey flows east along Timberwood Road, where two, 5' Type R
Inlets capture the flow at design points 46 and 47. Once captured by the inlets, the
flow from basins 46-47 combines with that from basins 105, 107, and 109, and is
conveyed south and into pond 593 (basin 43).
Basins 108, 44, and 45
Basin 108 conveys its flows southeast towards design point 108, where two, CDOT
Type D Inlets capture the flow from basin 108. Meanwhile, basins 44 and 45 convey
flows east and west along Timberwood Road, where a 10' Type R Inlet (north side of
Timberwood Road) and a 5' Type R Inlet (south side of Timberwood Road) capture
the flow at design points 44 and 45. Once captured by the inlets, the flow from
basins 44 and 4..5 combines with that from basin 108 and is conveyed south and into
pond 593 (basin 43).
Basin 43
Basin 43, located in the southeast corner of the site, is the ultimate design point for
the PVHS Filing 2 Site. In the future,. Basin 43 (Pond 593) will capture flows from
all the basins contained in PVHS Filings 1 and 2. Basin 43/pond 593 will provide
18.71 acre-feet of detention, including water quality volume for the PVH Site. Basin
43 will discharge at the staged release rate of 0.20 cfs/acre for the 10-year design
storm and 0.50 cfs/acre for the 100-year design storm.
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Basins 3, 4, 30, and 32
Basins 3, 4, 30, and 32 all drain to the existing detention pond 394, located in basin
30. The storm flows from these basins were accounted for in Filing 1, and thus are
not used in routing with the other on -site basins. However, the 10 and 100-year
release rates (3.4 cfs & 8.6 cfs) from pond 394 were added as "other flow" in the
rational routing calculations in Appendix B. Storm drain inlets have been provided
to intercept the 100-year storm flows from basins 3 and 32, which were previously
conveyed to pond 394 via a small swale. These inlets convey the flows into the north
end of pond 394.
Basins 31, 33, and 101
Basins 31 and 33 convey runoff southeast along Timberwood Road until the storm
flows are captured by 10' Type R Inlets (in sump) at design points 31 and 33.
Meanwhile, basin 101's flow is conveyed south overland and into the proposed 2' x
4' concrete box at design point 101. Here the flow from basins 31, 33, and 101 is
conveyed south through the 2' x 4' box culvert, where it then combines with the
flows from basins 3, 4, 30, and 32. This combined flow is routed eastward in Swale
A/CS260 towards design point 36.
Basins 102, 34, 35, and 36
Basins 34 and 35 convey runoff east and west along Timberwood Road until the
storm flows are captured by 10' Type R Inlets (in sump) at design points 34 and 35.
Meanwhile, basin 102's flow is conveyed south overland and into the proposed 2' x
3' concrete box at design point 102. Here the flow from basins 34, 35, and 102 is
conveyed south through the 2' x 3' box culvert, where it then combines with the
flows from basins 3, 4, 30, 32, 31, 33,101, and 36 at design point 36. This combined
flow is routed eastward in Swale A/CS260 towards design point 3.7.
Basins 50, 51, 52, 53,1039104, 38, 39, and 37
Basins 50 and 51 convey storm flows south across Harmony Road and a small
portion of Snow Mesa Drive where two, 10' Type R Inlets (in sump) capture the
flows at design points 50 and 51. The flows from 50 and 51 are conveyed west and
then south in 18" and24" RCP. Meanwhile, basins 52 and 53 convey storm flows
southeast and northwest along the private drive to two, 5' Type R Inlets (in sump) at
design points 52 and 53. The flows from basins 50-53 combine in the 24" RCP and
are conveyed south, where basin 104's flow is added. Once combined, the flow from
basins 50-53, and 104, is directed south towards the 2' x 6' box culvert. at design
point 103. The flows from basins 50-53, 103, and 104 combine at design point 103
and are conveyed south, through the 2' x 6' box culvert. The flow from. basins 38
and 39 is conveyed east and west along Timberwood Road to two, 10' Type R Inlets
(in sump) at design points 38 and 39. The combined flows continue south in the 2' x
6' culvert towards design point 37. Basin 37 conveys its flows eastward in Swale
A/CS260 towards design point 37. Here, the flow from basins 3,4,30-39, 50-53, and
101-104 combine and continue east in Swale B/260 towards design point 42.
D. Hydraulic Criteria
All calculations within this study have been prepared in accordance with the City of
Fort Collins Storm Drainage Criteria and are included in the appendix.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
The purpose of this report is to size the proposed detention pond and present general
drainage concepts for PVHS Filing 2, for use when future development of the site is
reviewed. It is important to note that all storm infrastructure was designed for the
100-year storm.
In the future, the north detention pond (existing pond 393) will be moved to the
southeast comer of the site (refer to the drainage exhibit in Appendix G). The
relocated pond 393 (Pond 593 in PVHS Filing 2) will provide the required volume
for Filing 2 and act as a regional detention pond. Pond 593 will provide all of the
required detention for the second filing and the area that was served by the previous
location of pond 393. Pond 593 will drain to the existing drainage swale that exists
along the north and east boundary of Timber Creek. The release rates from Pond 593
are based on the requirements of the Master Plan for the McClellands Basin, which
requires on -site detention using a staged release rate of 0.20 cfs/acre for a 10-year
design storm and 0.50 cfs/acre for a 100-year design storm.
Please note that the relocation of pond 393 may be delayed until sufficient
development has taken place to justify the expense of building the regional pond.
p B. Specific Details
The remaining portion of the Poudre Valley Health Systems Harmony Campus
® Medical Center property contains approximately 72.6 acres of which approximately
® 29 acres has been developed with the first phase. Filing 2 has been broken into 34
on -site drainage basins.
Basins 2 and 106
Basins 2 and 106 contain a portion of Harmony Road that allows developed runoff to
sheet flow into the Spring Canyon Lateral, located between the project site and
Harmony road, as it has historically done.
The flow from this site ultimately discharges into the McClellands Basin Drainage
way.
No off -site runoff from properties surrounding the Poudre Valley Hospitalsite pass
through the site. With the construction of PVHS Filing 2, no additional flows are
anticipated.
Poudre Valley Hospital Filing 1 has detention ponds #393 and 4394 on site. The
total area draining to these two ponds is equal to approximately 29 acres.
In this report, pond 393 will be relocated to the southeast corner of the site and will
be called Pond 593, as seen in the updated SWMM model for PVHS Filing 2.
B. Sub -Basin Description
Historic drainage patterns on the subject site are in a southeasterly direction.
Excerpts from the McClellands Basin 100-Year Master Plan Update can be found in
Appendix C. No off -site runoff from properties surrounding the Poudre Valley
Hospital site traverse through the site.
III. DRAINAGE BASIN CRITERIA
A. Regulations
The City of Fort Collins Storm Drainage Design Criteria is being used for the subject
site.
B. Development Criteria Reference and Constraints
The criteria and constraints from The McClellands Basin 100-Year Master Plan and
the subsequent update, dated March 2000 by Icon Engineering will be utilized in this
Drainage Study. The Poudre Valley Hospital site is currently'being utilized as
® fallow agricultural land
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C. Hydrologic Criteria
The SWMM hydrologic model that was previously used in the McClellands Basin
100-Year Master Plan Update by Icon Engineering, has been utilized and updated in
this report in order to analyze the hydrologic conditions of the proposed PVHS Filing
2.
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PROJECT DEVELOPMENT PLAN, DRAINAGE AND EROSION CONTROL REPORT
FOR THE POUDRE VALLEY HEALTH SYSTEMS HARMONY CAMPUS
INFRASTRUCTURE
FORT COLLINS, COLORADO
I. GENERAL LOCATION AND DESCRIPTION
A. Location
The Poudre Valley Health Systems site is located south of Harmony Road and east of
Timberline Road in southeastern Fort Collins, Colorado. The site is shown on the
Vicinity Map in Appendix A. More particularly, the site is situated in the
northwesterly portion of Section 5, Township 6 North, Range 68 West of the Sixth
P.M., City of Fort Collins, Larimer County, Colorado.
B. Description of Property
The remainder of Poudre Valley Health Systems Harmony Campus Medical Center
site contains approximately 72.6 acres of land, all of which is currently undeveloped
and being proposed for Poudre Valley Health Systems Harmony Campus Medical
Center Filing 2 (PVHS Filing 2). The majority of the property currently consists of
fallow farmland with tall grass vegetation. The site generally slopes in a southeasterly
direction at approximately 2.0%.
II. DRAINAGE BASINS
A. Maior Basin Description
The PVHS Filing 2 site lies entirely within the McClellands Basin. The project
drainage is modeled in The McClellands Creek Master Drainage Plan Update (March
2000). Applicable portions of these studies are included in Appendix C.
Historic drainage patterns on the subject site are in a southeasterly direction per the
McClellands Basin 100-Year Master Plan Update. The site historically discharges
into Conveyance Element 39. Conveyance Element 39 is currently an open channel
that runs along the southern property line of the PVH site. At the southeast corner of
the site, Conveyance Element 39 turns the corner and flows south along the east
property line of the Timber Creek PUD and the Stetson Creek PUD. Excerpts from
the McClellands Basin 100-Year Master Plan Update can be found in Appendix C.
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APPENDIX
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VICINITY MAP/ MODIFIED SWMM MAP A
RATIONAL METHOD HYDROLOGY/ STREET CAPACITIES B
SWMM POND SIZING, RATING CURVES, WQCV, ORIFICE, & C
OVERFLOW WEIR CALCULATIONS
STORM DRAIN SIZING: UDSEWER & HY8 D
STORM INLET SIZING: UDINLET E
SWALE SIZING & RIPRAP CALCULATIONS F
DRAINAGE & EROSION CONTROL PLAN DRAWINGS & DETAILS G
TABLE OF CONTENTS
DESCRIPTION PAGE
I. GENERAL LOCATION AND DESCRIPTION
A. LOCATION 5
B. DESCRIPTION OF PROPERTY 5
II. DRAINAGE BASINS
A. MAJOR BASIN DESCRIPTION
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B. SUB -BASIN DESCRIPTION
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III.
DRAINAGE DESIGN CRITERIA
A. REGULATIONS
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B. - DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
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C. HYDROLOGICAL CRITERIA
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D. HYDRAULIC CRITERIA
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IV.
DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT
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B. SPECIFIC DETAILS
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V.
STORM WATER QUALITY
A. GENERAL CONCEPT
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B. SPECIFIC DETAILS
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VI.
EROSION CONTROL
A. GENERAL CONCEPT
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VII.
CONCLUSIONS
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A. COMPLIANCE WITH STANDARDS
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B. DRAINAGE CONCEPT
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C. STORM WATER QUALITY
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D. EROSION CONTROL CONCEPT
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REFERENCES
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SEAR• BROWN
Mr. Basil Hamdan
City of Fort Collins
Water Utilities --Storm water
700 Wood Street
Fort Collins, Colorado 80521
ARCHITECTURE 2095outh Meldrum
ENGINEERING Fort Collins,C080521
PLANNING 970.482.5922 phone
CONSTRUCTION 970.482.6368 fax
www.searbrown.com
February 11, 2004
RE: Final Drainage and Erosion Control Report for Poudre Valley Health Systems Harmony
Campus Infrastructure
Dear Basil:
We are pleased to resubmit to you, for your review and approval, this Final Drainage and Erosion
Control Report for Poudre Valley Health Systems Harmony Campus Infrastructure. All
computations within this report have been completed in compliance with the City of Fort Collins
Storm Drainage Design Criteria.
We appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Respectfully,
The Sear -Brown Group
Prepared by:
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John Gooch, EIT
Project Engineer
Jim Allen -Morley, P.E.
Project Manager
Final
Drainage and Erosion Control Report
Poudre Valley Health Systems
Harmony Campus
Infrastructure Project
Development Plan,
Fort Collins, Colorado
February 11, 2004
SEAR• BROWN