HomeMy WebLinkAbout6TH FILING OF QUAIL HOLLOW SUBDIVISION - FINAL - 46-89G - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE AND
EROSION CONTROL STUDY
FOR THE
QUAIL HOLLOW
SIXTH FILING
FINAL DRAINAGE AND
EROSION CONTROL STUDY
FOR THE
QUAIL HOLLOW
SIXTH FILING
March 2, 1992
Prepared for:
d. Jensen Enterprises
2903 Blue Leaf Drive
P.O. Box 1007
Fort Collins, Colorado 80526
Prepared by:
RBD, Inc. Engineering Consultants
2900 South College Avenue
Fort Collins, Colorado 80525
(303) 226-4955
RBD Job No. 014-040
MJMJ1
INC.
Engineering Consultants
2900 South College Avenue
Fort Collins, Colorado 80525
303/226-4955
FAX: 303/226-4971
March 2, 1992
Ms. Susan Hayes
City of Fort Collins
Utility Services Stormwater
235 Mathews
Fort Collins, Co. 80522
RE: Final Drainage and Erosion Control
Study for the Quail Hollow Sixth Filing
RBD Job. No. 014-040
Dear Susan:
We are pleased to submit to you, for your review and approval,
this Final Drainage and Erosion Control Study for the Quail Hollow
Sixth Filing. All computations within this report have been
completed in compliance with the City of Fort Collins Storm
Drainage Design Criteria.
Thank you for your time and consideration of this submittal.
Please call if you have any questions.
Respectfully,
RBD Inc."Engineering Consultants
Kevin W . Gingery, P.E.
Project Engineer
J g '���iir� i� ��ielt�r►'�ti�
CC: Mr. Dan Jensen - d. Jensen Enterprises
Other offices: Denver 303/778-7338 • Vail 303/476-6340 • Longmont 303/678-9584
TABLE OF CONTENTS
DESCRIPTION PAGE
I. GENERAL LOCATION AND DESCRIPTION
A. LOCATION 1
B. DESCRIPTION OF PROPERTY 1
II.
DRAINAGE BASINS AND SUB -BASINS
A. MAJOR BASIN DESCRIPTION 1
B. SUB -BASIN DESCRIPTION 2
III.
DRAINAGE DESIGN CRITERIA
A. REGULATIONS 2
B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 2
C. HYDROLOGICAL CRITERIA 2
D. HYDRAULIC CRITERIA 3
E. VARIANCES FROM CRITERIA 3
IV.
DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT 3
B. SPECIFIC DETAILS 3
V.
EROSION CONTROL
A. GENERAL CONCEPT 4
B. SPECIFIC DETAILS 5
VI.
CONCLUSIONS
A. COMPLIANCE WITH STANDARDS 5
B. DRAINAGE CONCEPT 6
C. EROSION CONTROL CONCEPT
REFERENCES 6
APPENDIX
VICINITY MAP 1
OFFSITE HYDROLOGY 2
FILING NO. 6 HYDROLOGY 7
DETENTION 10
DESIGN OF INLETS, STORM SEWER AND SWALES 12
RIPRAP DESIGN 30
SPRING CREEK FLOODPLAIN DATA INFORMATION 33
EROSION CONTROL 37
CHARTS, TABLES, AND FIGURES 41
FINAL DRAINAGE AND
EROSION CONTROL STUDY
FOR THE
QUAIL HOLLOW SIXTH FILING
I. GENERAL LOCATION AND DESCRIPTION
A. Location
The Quail Hollow Subdivision is located east of the
southerly extension of Overland Trail and south of
Yorkshire and Michener Streets in southwest Fort Collins,
Colorado. The site is shown on the Vicinity Map in
Appendix A. More particularly, the site is described as
Quail Hollow, Sixth Filing, and is situated in the
Northwest 1/4 of Section 28, Township 7 North, Range 69
West of the Sixth P.M., City of Fort Collins, Larimer
County, Colorado.
B. Description of Property
The Quail Hollow Sixth Filing contains 12.4 acres more or
less of which all of the area is currently undeveloped
and being proposed for residential development. The
majority of the property has consisted of cultivated farm
land. Topography at the site is generally sloping from
northwest to southeast at approximately 1.2%. A
tributary to Spring Creek traverses through the Quail
Hollow site from a northwest to southeasterly direction.
Within this tributary to Spring Creek exists a
substantial cattail outcropping/wetlands area in an
existing detention pond. There are two existing
detention ponds adjacent to the Sixth Filing of Quail
Hollow. Spring Creek traverses across the southeastern
corner of the Quail Hollow Subdivision as it flows in a
northeasterly direction.
II. DRAINAGE BASINS AND SUB -BASINS
A. Major Basin Description
No major drainageway exists in the Sixth Filing of the
Quail Hollow Subdivision. The Quail Hollow Subdivision
does drain into Spring Creek per the Spring Creek Major
Drainageway Plan by Gingery Associates, Inc. dated August
1980. The City of Fort Collins is planning a regional
detention pond on the southwest corner of Drake Road and
1
B.
Taft Hill Road in the future.
Sub -Basin Description
Historic drainage patterns on the subject site are
southeasterly across the site to Spring Creek. Several
off -site basins lying west of Overland Trail contribute
storm water runoff which crosses the Quail Hollow
Subdivision. Off -site basins from future Quail Hollow
Seventh Filing and Burns Ranch (located west of Overland
Trail) must be routed through the Sixth Filing of Quail
Hollow and into the existing detention pond. All off -
site flows are currently at historic conditions, but
construction of the First Filing of Burns Ranch is
beginning on March 2, 1992.
III. DRAINAGE DESIGN CRITERIA
A.
B.
C.
D.
Regulations
The City of Fort Collins Storm Drainage Design Criteria
is being used for the subject site.
Development Criteria Reference and Constraints
Several drainage reports were previously completed for
the subject site and adjacent lands as referenced in this
report. The Final Drainage Study for the Quail Hollow
Fifth Filing developed the design criteria for the
existing on -site detention ponds. The City of Fort
Collins is planning a regional detention pond on the
southwest corner of Drake Road and Taft Hill Road in the
future. Until the regional detention pond is
constructed, storm water runoff from the Sixth Filing of
Quail Hollow and from off -site lands lying west of
Overland Trail must be diverted into the existing
detention ponds.
Hydrological Criteria
The rational method was used to determine runoff peak
flows from the site and the surrounding off -site
tributary areas. The 2 and 100 year rainfall criteria,
which was obtained from the City of Fort Collins, is the
criteria which was utilized. This criteria is included
in the Appendix.
Hydraulic Criteria
All calculations within this study have been prepared in
accordance with the City of Fort Collins Drainage
Criteria.
K
E. Variances from Criteria
No variances are being sought for the proposed project
site.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
As development occurs within the Sixth Filing of Quail
Hollow, all on -site fully developed flows will flow
southeasterly into one of the two existing detention
ponds. Off -site runoff (from west of Overland Trail)
will be directed around the south side of the Sixth
Filing of Quail Hollow and northeasterly into the
existing detention pond. Included in the back pocket of
this report is the Sixth Filing drainage plan.
B. Specific Details
Two year developed storm water runoff from basins 1
through 4 is proposed to be collected in storm sewer
systems at the low areas (sumps) in each street and
redirected into the existing detention ponds adjacent to
the Sixth Filing of Quail Hollow. Flows in excess of the
2 year storm runoff will pond up at the sump locations
and eventually over top the sidewalks and be redirected
by overflow swales between the lots to the existing
detention ponds. Included in the appendix are the
hydraulic calculations for each storm sewer system, the
overflow swales, and related street over topping
calculations. A concrete trickle pan is proposed to
carry low flows from the Poteet Court storm sewer system
to the outlet of existing detention pond no. 2.
The off -site future fully developed runoff from the
Seventh Filing of Quail Hollow and Burns Ranch
subdivisions must be redirected around the Sixth Filing
of Quail Hollow. The 100 year developed storm water
runoff from the off -site areas lying west of Overland
Trail is proposed to be collected in a storm sewer system
at the south property line of the Sixth Filing of Quail
Hollow and redirected easterly in a swale into existing
detention pond no. 1. Due to the location of this storm
sewer system and its 100 year design, in the event that
the upstream end becomes plugged, storm water will pond
up and over top onto Overland Trail and flow in a
southerly direction to the eventual low point at the
Spring Creek future crossing of Overland Trail. For the
Sixth Filing of Quail Hollow, approximately one half of
the storm sewer system will be constructed. In order to
ensure that the entire storm sewer system will function
as intended, the hydraulic design was completed for the
entire system and will need to be reviewed and updated as
the Seventh Filing of Quail Hollow is developed in the
future.
Within existing detention pond no. 1 there is an existing
wetlands/wildlife area. This area has been created in
the natural tributary to Spring Creek over the years.
The Sixth Filing of Quail Hollow will discharge storm
water runoff into the existing wetlands/wildlife area.
Storm water runoff will pass through the
wetlands/wildlife area and eventually be transported to
Spring Creek. It is the intent of this Sixth Filing
development to keep the existing wetland/wildlife area as
natural as possible in order to not affect the wetlands
area. The runoff generated from this development will
pass through the existing detention pond no. 1 with
little to no impact upon the area. No drainage
construction is anticipated directly within the existing
cattail outcroppings of the wetlands area. Care should
be taken when constructing the storm sewer and swale
which connect into existing pond no. 1. If for some
unforeseen reason the cattail outcropping is disturbed,
a U.S. Army Corps of Engineers 404 permit may be required
to complete the work, but this is not anticipated to be
needed. Coordination of a 404 permit would need to be
done with the local regional office of the U.S. Army
Corps of Engineers in Denver.
Adequate detention volume has been provided in the
existing detention ponds no. 1 and 2 for the Sixth Filing
of Quail Hollow per the Fifth Filing of Quail Hollow
approved drainage report.
The groundwater table is close to the surface of the
ground in the Sixth Filing of Quail Hollow and is
expected to be pumped, piped and redirected during the
course of construction. Therefore a Colorado Department
of Health Construction Dewatering Permit will be required
before any construction can begin on the Sixth Filing of
Quail Hollow.
V. EROSION CONTROL
A. General Concept
The Sixth Filing of Quail Hollow lies within the both the
Low and High Rainfall Erodibility Zone and both the Low
and Moderate Wind Erodibility Zone per the City of Fort
Collins zone maps. Due to the existing site slopes of
around 1%, the potential exists for minor erosion
problems after the Sixth Filing improvements are
.19
completed and the ground is bare. It is anticipated that
the Sixth Filing improvements will be completed during
the summer of 1992. Thus the new improvements will be
subjected to both wind and rainfall erosion.
Per the City of Fort Collins Erosion Control Reference
Manual for Construction Sites and related calculations in
the appendix, the erosion control performance standard
for the subject site is 78.9 %. From the calculations in
the appendix, the effectiveness of the proposed erosion
control plan is 96.5 %. Therefore the erosion control
plan as specifically detailed below, most nearly meets
the City of Fort Collins requirements.
B. Specific Details
For basins 1,2,3 and 4, after the overlot grading has
been completed, all disturbed areas, not in a roadway,
should have a temporary vegetation seed applied. After
seeding, a hay or straw mulch should be applied over the
seed at a rate of 2 tons/acre minimum and the mulch
should be adequately anchored, tacked, or crimped into
the soil. After the utilities have been installed, the
roadway surfaces should receive the pavement structure.
After installation of the curb inlets, the inlets should
be filtered with a combination of concrete blocks, 1/2"
wire screen and coarse gravel (3/411).
All other disturbed areas should have temporary
vegetation seed applied. After seeding, a hay or straw
mulch should be applied over the seed at a rate of 2
tons/acre minimum and the mulch should be adequately
anchored, tacked, or crimped into the soil. Erosion bale
check dams and sediment collection barriers should be
installed immediately after the improvements they protect
have been constructed, as shown on the drainage plan in
the back pocket of this report.
In the event the temporary vegetation seed and mulch will
not be applied for an extended period of time after
overlot grading, install a temporary silt fence along the
south and east boundaries of the site to minimize rain
and wind erosion.
VI. 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.
5
1.
2.
3.
4.
5.
6.
B.
C.
Drainage Concept
The existing detention ponds adequately provide for the
detention of developed on -site flows from the Sixth
Filing of Quail Hollow. By utilizing the temporary
detention ponds in the Fifth Filing of Quail Hollow, the
developed storm water runoff has been controlled in order
to eliminate off -site downstream damage from the 2 year
and 100 year storm events.
The proposed drainage concept
and shown on the drainage plan
City of Fort Collins drainage
Erosion Control Concept
s presented in this report
are in compliance with the
criteria.
The proposed erosion control concepts adequately provide
for the control of wind and rainfall erosion from the
Sixth Filing of Quail Hollow. 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. Hay or straw mulch is being proposed as it has
recently proven to be the most economical and efficient
method available to control erosion.
Storm Drainage Design Criteria and Construction Standards by
the City of Fort Collins, Colorado May 1984.
Quail Hollow Subdivision, Filings 4 through 7, Preliminary
Drainage Report by RBD, Inc., Engineering Consultants,
November 1989.
Final Drainage Report for Quail Hollow P.U.D. , Third Filing by
RBD Inc., Engineering Consultants, May 1988.
Quail Hollow Subdivision, Filing 4 Final Drainage Report by
RBD, Inc., Engineering Consultants, March 1990.
Preliminary Drainage Report for the Burns Ranch at Quail Ridge
by RBD, Inc., Engineering Consultants, December 21, 1990.
Report of a Geotechnical Investigation for Quail Hollow P.U.D.
Fourth, Fifth, Sixth & Seventh Filings by Empire Laboratories,
Inc., November 3, 1989.
6
7. Spring Creek Major Drainageway Plan for the City of Fort
Collins, Larimer County Colorado by Gingery Associates, Inc.,
August 1980.
8. Final Drainage Study for the Quail Hollow Fifth Filing by RBD
Inc. Engineering Consultants, May 10, 1991.
9. Final Drainage and Erosion Control Study for Burns Ranch at
Quail Ridge First Filing by RBD Inc. Engineering Consultants,
August 2, 1991.
rJ
APPENDIX
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