HomeMy WebLinkAboutREGISTRY RIDGE PUD, 2ND FILING - PRELIMINARY - 32-95D - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORT3.2.2 Mite Conveyance Elements
As with the detention, the Filing One drainage report accommodates developed runoff from this
site in their storm sewer system. Northern Engineering was still working on their report but
provided us with their hydraulic design of the two systems we will connect to at Design Points I
and 9. Our preliminary evaluation of the runoff indicates a slightly increased flow at both these
points than what was developed by Northern but this may be corrected by a more precise
calculation of the composite runoff coefficient in our final drainage report. In any event we will
provide a UDSEWER analysis of both the onsite and pertinent offsite storm sewers with our final
report.
3.3 Erosion Control
Erosion and sediment control on the site will be accommodated by silt fence, inlet filters and
revegetation. An additional water quality concern is a proposed convenience store with gas
station to be located in Subbasin A3. The storm inlet to be located in this subbasin will need to
accommodate retention of contaminants. We anticipate utilizing some type of grease trap inlet,
perhaps a Carter Concrete "Stormceptor" system. The final report will include the erosion
control design and calculations required by the City.
6
ff 9 iL.--4 1_.._-4 l_J a! Ll IJ l.._l I_.J a:_J__--
TABLE 2. SUMMARY OF ATTENUATED RUNOFF
............ x.
.. ........
.:.... :.. n..
....n ... ..
x
... .....i
... ........
.. .....
..............................f.:
...............
.:: .... .... }::}iY:
...... ..... ...........................
.......xx......
.......... .....
:............
...x..: n...
.. ..
'MF:.V.\!'IIh .
.:.:. :.:::::.. .., •.
N.
..:"
:.YYYY'Uft9'i'.::.::::.�
...5. ........x.x......
.... .... n.........
:..:. .. x. .. n. n..,n. v...... e.x...... v.
... ...v:,w.. x. ....... ... ...x,.......»..
.. ..:v. n......... .. :.......
...x. nh.l .....v...
....:....,, .:. n.. t..x
... ........
.....
...r.............r.....h::::............... x. xr.......:::x
.: .......r...... :.... ....x....... :..:.::
:.::.:.......9t?�EA51k�19i:3i::ic;.^;.3!?:aS::
.. n.x.......x x ,..r:. .................
.. ... ...x.
... ..... ..x
::.. ..
... .........
...nx.. x.
.Y.} ,,..
w... gyp. ........ ...
..... n..
..:.:....
x•.....:. ... .. ....::.::x:...
i:.
0.70
3.90
4.60
1.80
0.90
2.70
7.30
0.60
1.90
3.80
11.70
.......... ....x x ..
:. ...
.. .....
..
...._ ..
x.
.....M. 1...
.. .............:...:..
.......... ..ii}:i: hY;..:...::
0.58
0.80
0.77
0.73
0.88
0.78
0.77
0.91
0.76
0.80
0.79
..: .........x.x..
.. .. .f.
.. ...
h....
..... x.. ...n
.. .. n :.....:.
.. .. ... ...
.v.... .........r.......
F, , c}9.�:}:.:
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
v. ..,
.. ...n:x:...v ..::.hhY}:}�.'v:::v':tv.::::::
.. .x
.. . t..
: :.•.. ... <
...
.:..
... :F..}.
.r.:....... . :
..{..
h}}::h:.i i
:::.n:..
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
.F......
:).....
.. ..Y:•.n�n e...
}. .. n. ... ,l�.:r....
x ::....
« ....1........:.....
.....i.... F.....
.....v.x... ..:......:n
7.5
13.0
13.0
5.8
3.3
5.8
13.0
3.7
13.5
13.5
13.5
:>:: s:::
:nSY..
0.l.ti.h - :.:J�..::
v.... },.;:h ' v'.i.Q
n..
,.: x:t„x...
.:..., ..Y......Y . Y......:
::::::lv.:. ...v::::.rv}:
....
5.9
10.9
10.9
4.3
3.8
4.3
10.9
2.4
11.9
11.9
11.9
>s:>:: ; . A3GCiU7Rk4
, 221E?.`i �v'
ii33:` ;Ti.:
:��x�
...... .
:F:
2.8
2.3
2.3
3.2
3.3
3.2
2.3
1 3.3
2.2
2.2
2.2
`>"s:
.. _...
7.0
7.0
7.0
7.0
7.0
7.0
7.0
1 7.0
6.7
6.7
6.7
i}i.
x.::.:.. ;..
i' 111fSGC"EIiRC
Fy�:;'•n<Ai
:.0
::�RnY:�::
:: {�.�. .:...:.
1.1
7.2
8.1
4.2
2.6
6.7
12.9
1.8
3.2
6.7
20.3
{'}Y •'��'vE':�vi:::}..:
::>Y::.
�`'F::,.::.:F?.....
�....... ........
3.6
27.3
_31.0
11.5
6.9
19.4
49.2
4.8
12.1
7
60
6
5
4•
4
3
2
8
1•
1
A7
A6
A6,A7
A5
A4
A4,A5
A4,A5,A6,A7
A3
A2
AI A2
Al,A2,A3,A4,A5,A6,A7
A
25.5
77.4
B
9
B1,B2
8.50
0.63
1.00
1.25
25.0
19.7
1.6
5.3
8.6
35.5
TST, INC.
12lIS/97
CONSULTING
ENGMEERS •Indieataa not all basins contributing. 000_bydl.xb
8
TABLE I. HYDROLOGIC CALCULATIONS WORKSHEET
0
. ... .....
W.
X....
.......... . . . . .
....
... ..
. .. .. . . . . . . . . . . .
. . . . . . . . . . . . .
Al
1
0.83
1.80
10-0
12.1
10.8
2
8
1.00
2.00
10.7
13.5
11.9
A2
A3
2
2.00
.00
2.80
0.9
-:::33
2.4
1 3
A
A4
4
1.50
2.5
5.
5.3
A5
5
"'o
2.10
2.9
A6
6
O5 0
150
A7
7
1.00
2.00
2.0
1.3
5.9
2.80T.00
....
B
-BI
9
0.40
-
1.50
-
103
25.0
19.7
1.60
5.30
5.3
22.0
-B2
9
2.25
3.00
8.9
12.9
11.7
2.30
6.80
4.8
17.6
TST, INC.
CONSULTING
ENGINEERS
12/15/97
000_hydl.yls
7
TABLE 1. HYDROLOGIC CALCULATIONS WORKSHEET
......... ..
C-0 ......
V. X.
-0-nmmw
W.M.."M
M
OV
Al
1
1.9
0.84
1.00
1.25
30
2.00
2.1
0.8
1075
A2
9
1.9
0.76
1.00
1.25
30
2.00
2.9
1.2
1295
A3
2
0.6
0.91
1.00
1.25
100
2.00
2.9
1.5
150
A
A4
A5
4
5
0.9
1.8
0.88
0.73
1.00
1.00
1.25
1.25
75
30
2.00
2.00
2.8
3.0
1.3
1.5
225
350
A6
6
3.9
0.80
1.00
1.25
50
2.00
3.2
1.1
885
A7
7
0-7
0.58
1.00
1.25
50
R.0-0
5.5
3.9
240
B
BI
9
5.1
0.65
1.00
1-25
480
2.00
14.7
9.4
930
B2
DO
1.25
30
2.00
4.0
TST, INC.
CONSULTING
ENGINEERS
17JIS/97
000_tiydI.xls
i
where L is the length of overland flow in feet (limited to a maximum of 500 feet), S is the average
basin slope in percent, C is the runoff coefficient, and Cf is the storm frequency coefficient. The
q formula limits the product of CCf to 1.0 and when the product exceeds this value 1.0 is used in its
place. Gutter travel times were determined using Figure 3-2 of the USDCM which provides a
flow velocity for a given gutter slope. This procedure for computing time of concentration allows
7 for overland flow as well as travel time for runoff collected in streets, gutters, channels, pipes, or
ditches. After the peak runoff was calculated, attenuated runoff was calculated. This was done
by combining all contributing areas upstream of a given design point. The time of concentration
for the design point was taken as the greatest time of all the contributing subbasins.
3.2 Drainage Plan Development
The proposed drainage plan consists of a combination of overland flow and gutter flow. The
a runoff will sheet flow across landscaped yards, common areas and parking lots, then concentrate
at proposed streets. Gutter flow in streets will be collected at low points via curb or area inlets
and then conveyed to the Filing One detention ponds via a storm sewer system. Subbasins were
delineated based on proposed grading. Contours representing the proposed grading are shown on
the Preliminary Grading and Drainage Plan which can be found in the back of this report.
Developed runoff from approximately % of this site and some developed offsite flows will be
routed through the property. and be connected to a proposed Filing One storm sewer at the
southeast corner of the site. The proposed Filing One storm sewer will convey developed runoff
to a proposed detention pond located to the south of Bon Homme Richard Drive. Offsite flows
are conveyed to Basin A on this site from two curb inlets to be located near the intersection of
Nimitz Drive and Dewey Drive. The storm sewer will be extended through this site for
9 connection to the Filing one system at Design Point 1. Additional inlets will be added to the
system at Design Points 2, 4, 5, and 6 and a culvert type opening will be provided at Design Point
7. The majority of Subbasin B1 is being reserved for a future daycare center and the future
developed condition is accommodated in the hydrologic calculations. Most of Subbasin B2 is an
offsite contribution from Filing One. Basin B will be directed to a Filing One storm sewer system
located in the northeast corner of the site at Design Point 9. This proposed storm sewer
1 discharges to a Filing One detention pond located on the north side of Truxtun Drive.
The results of the Rational Method. hydrologic analysis can be found in Table 1 with the
methodology of calculations shown in Appendix A. Table 2 shows the results of the runoff
attenuation described previously.
3.2.1 Preliminary Detention Design
Detention of developed runoff from this site has been accounted for in the Filing One drainage
1 design prepared by Northern Engineering Services. At the time this report was being prepared
the Filing One report was still a work in progress and not yet approved by the City. Northern
q Engineering has committed to providing us with a copy of the final approved report so that we
may confirm their assumed runoff from this site and address any deviations or needed
modifications in our final drainage report and design.
5
G
1
3.0
J Developed Conditions Plan
3.1 Design Criteria
The drainage system presented in this report has been developed in accordance with the criteria
established by the City of Fort Collins Storm Drainage Design Criteria and Construction
9 Standards Manual (SDDC) dated May 1984 and as revised in January 1991and April 1997.
J Where applicable, design guidelines and information were also obtained from the Denver Regional
Council of Governments Urban Storm Drainage Criteria Manual (USDCM).
i
Developed condition hydrology was evaluated based on the 2-year and 100-year storm
frequencies as dictated by Table 3-1 of the SDDC manual. Detention of developed flows from
j this site is required and is being accommodated by offsite detention facilities associated with Filing
One.
Because of the limited size of the subbasins on the site, the Rational Method was selected to
calculate runoff. The Rational Method utilizes the SDDC manual equation:
Q = CCfIA
where Q is the flow in cfs, C is the runoff coefficient, Cf is the storm frequency coefficient, I is the
rainfall intensity in inches per hour, and A is the total area of the basin in acres. The runoff
coefficient, C, was calculated based on the proposed development and coefficients for impervious
surfaces and pervious surfaces selected from Table 3-3 of the SDDC manual. Cf was taken from
Table 3-1 of the SDDC manual and was determined to be 1.0 for the 2-year storm and 1.25 for
the 100-year storm. The appropriate rainfall intensity was taken from the rainfall intensity
duration curve in Figure 3-1 of the SDDC manual. To obtain the rainfall intensity, the time of
concentration had to be determined. The following equation was utilized to determine the time of
concentration:
t, = ti + tt
where t is the time of concentration in minutes, t; is the initial or overland flow time in minutes,
and t, is the travel time in the gutter in minutes. The initial or overland flow time was calculated
with the SDDC manual equation:
t; _ [1.87(1.1 - CCf)I.O.Si/(S)0.33
4
2.0
Historic Conditions
The site is currently undeveloped pasture located in the Fossil Creek Basin that generally drains
east and southeast at flat to moderate slopes. An existing drainageway adjacent to the south of
the property collects almost all of the runoff from the site and conveys it under Shields Street to
an unnamed tributary of Fossil Creek. It does appear that some of the historic runoff reaching
Shields is conveyed north in the existing roadside ditch.
Prior to development of this property there will be some grading occur as a part of the Registry
Ridge First Filing (final plans are currently in the City review and approval process). Mite
runoff from the west will be intercepted at Nimitz Drive and collected in a storm sewer system.
Ultimately Filing Two will extend the storm sewer to it's final configuration but temporarily the
storm sewer will daylight in a channel to be graded across this property. The offsite developed
and a portion of the onsite undeveloped will be conveyed in this temporary channel to a culvert
and inlet system under Bon Homme Richard Drive to a detention pond associated with Filing
One. The northern third of the site will be graded to runoff to a proposed culvert and inlet system
under Truxtun Drive that also discharges to a proposed detention pond associated with Filing
One. For more information regarding this temporary grading and channeling refer to the Filing
One drainage report prepared by Northern Engineering Services.
3
I
I
I
Q
�y
J
�=
U
1RILBY ROAD
SITE
�q
47
SCALE 1 " = 2000'
FIGURE 1 - VICINITY MAP
a 1.0
Introduction
1.1 Scope and Purpose
This report presents the results of a preliminary drainage evaluation for the Registry Ridge P.U.D.
Second Filing. A hydrologic analysis of the proposed development plan was completed to
determine the location and magnitude of the storm runoff.
1.2 Proiect Location and Description
The Registry Ridge P.U.D. Second Filing is a proposed multi -family residential site located in the
Registry Ridge P.U.D. This site is located in the Northeast Quarter of Section 15, Township 6
North, Range 69 West of the 6th Principal Meridian, Larimer County, Colorado. The site is
bounded on the north by Truxtun Drive, on the east by Shields Street, on the south by Bon
Homme Richard Drive, and on the west by Nimitz Drive. A vicinity map illustrating the project
location is provided in Figure 1.
The Registry Ridge P.U.D. Second Filing consists of approximately 14.7 acres. Approximately 9
acres is proposed for multi -family apartment units and retail commercial pads, 2.7 acres of duplex
units, and the remaining 3 acres is proposed for future daycare site. The development will consist
of 6 building pads for apartments, 3 commercial pads, and 13 duplex units on 26 lots. The
apartments will be two and three story. buildings with no basements. Parking will be provided in
the form of off street parking stalls and the 5 garage structures. All of the streets within the
l development will be private and will be maintained privately. All of the perimeter streets are
�J public streets.
1.3 Previous Studies
The "Final Drainage Report for Registry Ridge P.U.D. First Filing" (Northern Engineering
Services) was a work in progress at the time this report was being prepared but applicable
sections were provided to us prior to the preparation of this report. Pertinent information from
this report is referenced in this report.
I
TABLE OF CONTENTS
1.0 Introduction
Page
1.1 Scope and Purpose...............................................................................................1
1.2 Project Location and Description.........................................................................1
1.3 Previous Studies...................................................................................................1
2.0 Historic Conditions......................................................................................................... 3
3.0 Developed Conditions Plan............................................................................................ 4
3.1 Design Criteria.....................................................................................................4
3.2 Drainage Plan Development................................................................................. 5
3.2.1 Preliminary Detention Design.................................................................... 5
3.2.2 Offsite Conveyance Elements.................................................................... 9
3.3 Erosion Control...................................................................................................9
Figures
Figure1 - Vicinity Map...............................................................................................................
2
Tables
Table 1 - Hydrologic Calculations Worksheet......................................................................... 6&77
Table 2 - Summary of Attenuated Runoff.................................................................................
Technical Appendices
Appendix A - Rational Method Analysis
Sheets
Preliminary Grading and Drainage Plan
u
December 16, 1997
Mr. Basil Hamden
City of Fort Collins Stormwater Department
P.O. Box 580
Fort Collins, CO 80522
RE: Registry Ridge P. U.D. Second Filing
Project No. 10-890-000
Dear Mr. Hamden:
We are pleased to submit this Preliminary Drainage Report for the Registry Ridge P.U.D.
Second Filing. Much of the offsite detention and storm sewer information that is
pertinent to this project is being submitted to the City by Northern Engineering Services
as part of the Registry Ridge P.U.D. First Filing. At the time we were preparing this
preliminary report the filing one final report was still being prepared so there may some
temporary gaps in the information that we will fill in when we submit the final report for
the second filing.
7 We believe this report satisfies the requirements for a preliminary submittal, and we look
forward to your review and comment. If you have any questions please feel free to
contact us.
Sincerely,
TST, INC. CONSULTING ENGINEERS
C-
% \[�
David B. Lindsay, P.E. Sharlene A. adowen, P.E.
DBL/tdy
TST, INCH 748 Whalers Way — BuildingD 1021nverness Terrace East
Fort Collins, CO 80525 Suite 105
Consulting Engineers (970) 226-0557 Englewood, CO 80112
Metro Denver (303) 595-9103 (303) 792-0557
Fax (970) 226-0204 Fax (303) 792-9489
'RELIMINARY DRAINAGE REPORT
FOR
NSTRY RIDGE P.U.D. SECOND FILING
—ro -- --
i
CITY OF FORT COLLINS
December 16, 1997