HomeMy WebLinkAboutLAURIE SUBDIVISION PUD - PRELIMINARY - 44-89C - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE INVESTIGATION
FOR
8 ACRES LOCATED IN THE
NE1/4,S3,T6N,R69W, LARIMER COUNTY, CO.
LAURIE SUBDIVISION SECOND FILING
Prepared for
Dr. Wiilliam Musslewhite
5001 S. Shields Street
Fort Collins, CO 80526
July 2, 1990
Commission No. 1180-01-01-03
CONSULTING ENGINEERS
FOUNDATION ENGINEERING, CONSULTING ENGINEERS, LTD.
320 N. Cleveland
Loveland, CO 80537
f
FOUNDATION I Counsulting
ENGINEERING Engineers
July 2, 1990
Commission No. 1180-01-01-02
Dr. William Musslewhite
5001 S. Shields Street
Fort Collins, Colorado 80526
Dear Dr. Musslewhite,
The enclosed report represents the results of the preliminary drainage
investigation for the Laurie Subdivision, -Second Filing, located in the
Northeast Quarter of Section 3, Township 6 North, Range 69 West of the
6th P.M., Larimer County, Colorado.
This investigation was based upon the proposed site development plan and
plat; proposed site development construction plans; on -site observations;
and available topographic information. The investigation was performed in
accordance with the criteria established in the City of Fort Collins -
"Storm Drainage Design Criteria and Construction Specification Standards"
manual.
It is our opinion that the construction of the Applewood Animal Hospital
is feasible provided that the recommendations contained in the attached
report and the incorporated final design are performed in accordance with
the final approved plans for the project.
If you should have any questions, please call.
Respectf �A
�f
Kev` W. P
21
FOUNDATI E
KWP/lanp
320 North Cleveland Avenue 0 Loveland, Colorado 80537 0 (303) 663-0138
TABLE OF CONTENTS
Letter of Transmittal
Table of Contents
Scope
Site Description
Existing Conditions
Proposed Development
Conclusions and Recommendations
Vicinity Map
Calculations
Drainage Plan/Site Plan
EXHIBITS
1
2
2
Exhibit A
Exhibit B
Exhibit C
ii
S C O P E
The following report represents the results of a drainage investigation
for a proposed development to be known as the Laurie Subdivision Second
Filing, located on a parcel of land situated in the Northeast Quarter of
Section 3, Township 6 North, Range 69 West of the 6th P.M., Larimer
County, Colorado. The investigation was performed for Dr. William
Musslewhite. The purpose of this investigation is to determine the
effects of the proposed development on the areas existing drainage
conditions and to determine the improvements, if any, and the appropriate
sizing for proposed improvements so that it may be incorporated with the
construction of the project. The conclusions and recommendations
presented in this report are based upon the proposed site development
plan and plat; proposed site development construction plans; on -site
observations; and the available topographic information. The analysis was
performed in accordance with the City of Fort Collins -"Storm Drainage
Design Criteria and Construction Standards" manual.
S I T E D E S C R I P T I O N
The site is generally rectangular in shape and contains approximately
eight acres, however, the sites East-West dimension is approximately
1,150 feet and its North -South dimension varies from approximately 390
feet at the westerly boundary to approximately 280 feet at the easterly
boundary. The site abuts the westerly right-of-way of South Shields
Street at a point approximately one-half mile south of Harmony Road. The
site is located on the Burns Tributary of the Fossil Creek Drainage
Basin.
E X I S T I N G C O N D I T I O N S
The site is presently used as a large residential tract with the existing
structures located at the southeast corner of the site near South Shields
Street. The Pleasant Valley and Lake Canal passes through the adjacent
property to the north with a lateral of that ditch flowing through the
site. Near the center of the site is a ravine that has been created by
scouring action associated with an overflow discharge from the Canal as
it flows across the site toward the South. According to the irrigation
company's officials, the overflow to the ravine is designed to discharge
a maximum flow of 30 c.f.s. (cubic feet per second).
East of the lateral ditch passing through the site, the property slopes
gently to the East toward South Shields Street at a slope of
approximately 20. The area below the ditch is irrigated and is used for
pasture except for the residence and out -buildings at the southeast
corner of the site.
1
The portion of the site that lies West of the ravine is not irrigated and
slopes rather steeply at approximately 15% toward the Burns Tributary of
Fossil Creek. The area is sparsely vegetated with ground cover consisting
mainly of native grasses and sage brush. The site abuts The Ridge
Subdivsion at the West and South.
The site receives run-off from the properties to the North and West. For
the purposes of this investigation, the area above the Pleasant Valley
and Lake Canal was not considered to effect the conditions onsite since
the ditch flow is controlled to the extent that there is an existing
overflow structure that directs excess flow to the ravine through the
site, as previously stated. The area to the North consits of
approximately 10.5 acres which drains easterly to South Shields Street
and then southerly along the west side of South Shields Street through
the site. An area of approximately 2.5 acres drains into the smaller side
ravine that enters the site at mid -point of the northern boundary.
Approximately 4.5 acres drains directly into the major ravine before it
enters the site near the northwest corner.
P R O P O S E D D E V E L O P M E N T
The proposed construction is to consist of developing the remaining
approximately 6.5 acres into approximately nine single family residential
lots. Laurie Court is to be extended to the west to a circular turn-
around located just to the west of the deep ravine which splits the site.
C O N C L U S I O N S A N D R E C O M M E N D A T I O N S
1. The proposed development will retain the existing drainage patterns
however, a 48" RCP will need to be installed under Laurie Court.
2. A catch basin or other drainage facility will need to be installed at
the low pint on Laurie Court to discharge gutter flow to the ravine.
3. The site is located in the fossil Creek Drainage Basin. The site is
not located within the floodway or flood plain.
4. All development is to be performed in accordance with City of Fort
Collins Standards and Specifications.
5. Onsite detention of stormwater is not recommended due to the sites
proximity to the existing "Major" drainage course.
6. Additional runoff from the Laurie Subdivision Second Filing will
travel to the ravine via overland flow and gutter flow in Laurie Court,
then south to Fossil Creek. It is our opinion that the small amount of
additional runoff from the site will not require enlargement of
downstream facilities.
0)
VICINITY MAP
EXH�I�BIT "A"
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VICINITY MAP
EXHIBIT "A"
No Text
•
Dr. Mussleshite-Laurie Subdivision
By: DRM
Commission No. 1180-01-01-03
Date: July 2, 1990
Calculations for Drainage Investigation for Laurie Subdivision located in
the NE 1/4 of Section 3, Township 6 North, Range 69 West of the 6th P.M.,
City of Fort Collins, Larimer County, Colorado.
Total Site Area = 6.5 acres +/-
EXISTING CONDITIONS
Rational "C" Factor = 0.20 for Offsite Irrigated Areas
itof 11= 0.25 for Offsite Steeper Non -irrigated Areas
if it it = 0.25 for Onsite Irrigated Areas
of if if = 0.30 for Onsite Steeper Non -irrigated Areas
PROPOSED DEVELOPMENT FOR LAURIE SUBDIVISION SECOND FILING
Rational "C" Factor = 0.45 (Estate residential district)
Note: areas 3, 4, and 5 of the attached map to be developed, all other
areas to remain in their existing condition.
Onsite area 3
Q2 = 1 ac(.45)(2.5)=1.13 CFS
Q100= 1 ac(.45)(7) =3.15 CFS
Onsite area 4
Q2 = 1 ac(.45)(2.5)=1.13 CFS
Q100= 1 ac(.45)(7) =3.15 CFS
Onsite area 5
Q2 = 1 ac(.45)(2.5)=1.13 CFS
Q100= 1 ac(.45)(7) =3.15 CFS
Increased runoff due to development
Q2 = 1 ac(1.125-.75)(3)=1.13 CFS
Q100= 1 ac(3.15-2.28)(3)=4.4 CFS
Refer to following calculations for runoff quantity determination
CULVERT SIZING
1. New culvert to be installed at cul de sac under Laurie Court at
ravine. The culvert is considered to be at "Inlet Control". Based upon
the runoff calculations the design flows at this point are: Q100= 30 +
19.5 + 4.4 CFS = 53.9 CFS
Using the Design Nomograph for Circular Pipe at Inlet Control:
@ HW/D = 1.0 and Q = 59.3 cfs an 48" dia. pipe will be sufficient
3
EROSION CONTROL
The primary area of concern is the ravine running thru the site. This may
require some type of "drop structures" along its course and inlet and
outlet protection at the proposed culvert under the cul de sac street.
Additional protection at the inlet and outlet ends of the culvert at
Shields Street should also be provided.
The City's Standard Erosion treatments for wind and storm -runoff should
also be incorporated during the course of construction.
2
y.
Calculated By:
DRM
STORM DRAINAGE INVESTIGATION
# 1180-01-01.02
Client : Dr. Musslewhite
Nil
Date : Dec. 29, 1989
RATIONAL METHOD PROCEDURE
Project: LAURIE SUBDIVISION
Checked By:
KWP
Design Storm: 2 YEAR Existing Conditions
Location
Point
Area
Runoff Coeff. Freq. Factor AxCxCf Flow Time
Flow Time
Rain Intens.
Runoff Comments
Description
Designation
(acres)
C.
'Cf"
Tchan(min.)Tc
(min.)
"I"(In./hr.)"Q"(c.f.s.)
Offsite Area "A"
Pt. A
10.5
0.2
1
2.10
15
2.1
4.41
Onsite Area 1
Pt. A+1
2
0.25
1
0.50
20
1.85
0.93
Pt. A+1
12.5
0.2
1
2.50
20
1.85
4.63 Flow at west side of Shields flowing to south
Offsite Area 'B"
Pt. B
2.5
0.25
1
0.63
10
2.5
1.56
Onsite Area 3
Pt.ik+3
1
0.3
1
0.,30
10
2.5
0.75
Pt. B+3
3.5
0.26
1
0.91
10
2.5
2.28 Flow at "minor" ravine at north central area
Offsite Area "C'
Pt. C
4.5
0.25
1
1.13
10
2.5
2.81
•
Onsite Area 4
Pt. C+4
Pt. C+4
1
5.5
0.3
0.26
1
1
0.30
1.43
10
10
2.5
2.5
0.75
3.58 Flow from north and west- add 30 c.f.s. Irrig
33.60 Total with irrigation flow
Onsite Area 6
Pt. 6
1
0.3
1
0.30
10
2.5
0.75
Total at Ravine
Pt. B+C+6
10
0.26
1
2.60
15
2.1
5.46 Flow exiting site - add 30 c.f.s. irrig.
35.50 Total with Irrigation flow
Onsite Area 2
Pt. 2
1
0.3
1
0.30
10
2.5
0.75 Flow to south offsite overland
Onsite Area 5
Pt. 5
1
0.3
1
0.30
10
2.5
0.75 Flow to south offsite to "major" ravine
r
Calculated By:
DRM
STORM DRAINAGE INVESTIGATION
# 1180-01-01-02
Client : Dr. Musslewhite
Date : Dec. 29, 1989
RATIONAL METHOD PROCEDURE
Project: LAURIE SUBDIVISION
Checked By:
KWP
Design Storm:100 YEAR - Existing Conditions
Location
Point
Area
Runoff Coeff. Freq. Factor AxCxCf Flow Time
Flow Time
Rain Intens.
Runoff Comments
Description
Designation
(acres)
C.
"Cf"
Tchan(min.)
To (min.)
'I"(In./hr.)"Q"(c.f.s.)
Offslte Area 'A'
Pt. A
10.5
0.2
1.25
2.63
15
6
15.75
Onsite Area 1
Pt. A+1
2
0.25
1.25
0.63
20
5.15
3.22
Pt. A+1
12.5
0.2
1.25
3.13
20
5.15
16.09 Flow at west side of Shields flowing to south
•
Offsite Area "B"
Pt. B
2.5
0.25
1.25
0.78
10
7
5.47
Onsite Area 3
Pt. 13+3
1
0.3
1.25
0.38
10
7
2.63
Pt. 13+3
3.5
0.26
1.25
1.14
10
7
7.96 Flow at 'minor" ravine at north central area
Offsite Area "C"
Pt. C
4.5
0.25
1.25
1.41
10
7
9.84
Onsite Area 4
Pt. C+4
1
0.3
1.25
0.38
10
7
2.63
Pt. C+4
5.5
0.26
1.25
1.79
10
7
12.51 Flow from north and west- add 30 c.f.s. Irriq
Onsite Area 6
Pt. 6
1
0.3
1.25
0.38
Total at Ravine
Pt. B+C+6
10
0.26
1.25
3.25
Onsite Area 2
Pt. 2
1
0.3
1.25
0.38
Onsite Area 5
Pt. 5
1
0.3
1.25
0.38
Page 1
42.50 Total with Irrigation flow
10 7 2.63
1 5 6 19.50 Flow exiting site - add 30 c.f.s. Irrig.
49.50 Total with Irrigation flow
10 7 2.63 Flow to south offsite overland
10 7 2.63 Flow to south offsite to "major' ravine