HomeMy WebLinkAboutDrainage Reports - 07/02/2018I
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\ North Star
design
700 Automation Dri ve, U nit I
Windsor, CO 8 0550
Ph one : 97 0-6 86-6 939
Fax: 97 0-6 86-11 88
April 30, 2018
Heather McDowell
City of Fort Collins Storm water
7 00 Wood Street
Fort Collins , CO 80522 -0580
City of Fort Coll'ns Approved Plans
Approved by:-+--?-~~--!...~
Date: 7 -2= -18
RE: Drainage Addendum to the "Final Drainage Report for the Seventh Filing of
the Centre for Advanced Technology"
700 Centre A venue
Dear Heather,
I am pleased to submit this drainage addendum in conjunction with the minor amendment for this
site for your review and approval. This drainage addendum serves to summarize the drainage
design of the Summitstone Health Partner project. This letter will detail the effect of the prop osed
improvements for the site and show that the site complies with the drainage concepts and designs
presented in the previ ous studies for this site.
This addendum has been prepared in conformance with the Fort Collins Stormwater Criteria
Manual with exceptions made for the circumstance that this project is being processed as a minor
amendment. I certify that this report for the drainage design was prepared in accordance with the
Master Plan and the criteria in the City of Fort Collins Storm Drainage Manual.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely,
Patricia Kroetch, P .E
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The Summitstone Health Partners proj ect is a Minor Amendment to the Centre for Advanced
Technology Seventh Filing which was designed and detailed in the plans and report completed by
RBD Engineering Consultants dated August 5, 1988 . This site is located on Tract B of that original
plat. In the time since those plans were approved, changes have been made to the site design on
Tracts A and C which have been detailed in multiple plan sets and drainage reports and addendums
most notably, Amended Master Drainage Plan for the Centre for Advanced Technology ( dated
February 1987), The Centre Avenue Residences (A replat of Tracts A and C) by Northern
Engineering dated October 13, 2009, The Arrowhead Cottages (a replat of Centre Avenue
Residences) by Northern Engineering dated August 2016, and The Centre for Advanced
Technology Fourteenth Filing. The drainage plan for this proposed project will conform to these
previously approved reports .
Historically, the majority of the site sheet flowed north and west to an existing detention pond
located in the northwest portion of the site. The proposed site will follow similar drainage patterns
as the historical drainage patterns. The majority of the site basins will be collected in the parking
lot and routed to the detention pond via pans and curb openings or direct discharge into the
detention pond as has historically occurred.
A summary of the onsite basins continue below.
B asin A is the east half of the existing parking lot. This basin is being modified slightly as 3
additional parking stalls are being added in the northeast comer of the parking lot. The runoff will
flow to a 2' curb opening as it has historically done and enter the detention pond.
B asin B is the west half of the existing parking lot. This basin is being modified slightly as the
loading area is being removed from the northwest portion of the parking lot. The runoff will be
collected in a 4' concrete pan and flow north to a 2' curb opening and enter the detention pond as
it has historically done.
B asin C is the west most portion of the site which includes all of the existing building on site and
the proposed building addition. The flow patterns for this basin are around the west side of the
building and flowing north into the detention pond. This drainage pattern will be maintained with
the roof runoff from the proposed addition being collected in underground pipes and conveyed to
the detention pond.
Basin D is the undeveloped area of the site that contains the New Mercer Ditch. Runoff from this
basin enters the New Mercer Ditch and does not enter the detention pond. No changes to this basin
are proposed.
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Stormwater detention is pro vided by an existing detention facility constructed with the S eve nth
Filing of th e Cen tre f or A d vanced Technology and certified with the Final Drainage and Erosion
Control Report for Centre Avenue Residences. This pond is shared with the Arrowhead Cottages
site which is adjacent to the west of this site and the CAT Filing 14 site which is northwest of the
Arrowhead Cottages. The original design for this pond included a total area of 7.81 acres which
includes Basins D2 , D3 and Worthington Circle with all basins having a minor C-value of 0.71
and a major (100 year) C-value of0.89 (0.71 *l.25). The revision to the drainage report included
with the Arrowhead Cottages development shows a composite minor C-value of 0.57 and a major
C-value of 0.72.
The Summitstone site has an existing minor C-value of 0.62 and a major C-value of 0.77 . The
proposed site will have an increase of 1,753 square feet of imperviousness which will increase the
imperviousness from 48 % to 50 %. These values were used to compile revised composite C-values
for the 7.81 acres (Basins D2 and D3) contributing to the detention pond. The revised composite
values for the 7.81 acres area 44.4 % impervious and a major c-value of0.72. These values were ·
then used to recalculate the required water quality capture volume and the detention volume for
the pond. The water quality increases from 0.147 to 0.150 acre feet and the detention volume
remains the same at 1.44 acre feet which are negligible changes in the required volume for this
pond. For thi s reason, no increase to the existing detention pond sizing is proposed.
The proposed construction will disturb approximatel y 8,840 square feet which is below the
threshold of 10 ,000 square feet at which additional erosion control design is required.
The detention pond will be modified to accommodate the building addition as a portion of this
addition encroaches on the existing detention pond. In order to minimize the impact of this
encroachment , a small landscape wall is being proposed along the portion of the building that is
adjacent to the pond. The pond will also be expanded in two small areas in order to compensate
for the storage volume that is being removed for the building addition. It is anticipated that the
pond volume will remain at 1.44 acre feet at an elevation of 5046.35 NA VD 88 (elevation 5043.35
NGVD ·29) as was determined in the Arrowhead Cottages drainage report. Calculations are
included at the end of this letter that show the impact of the increased imperviousness and the
modification of the existing pond . In summary , the impact of the proposed building expansion and
modifications to the site will have very minor impacts and the pond has been modified to
accommodate the encroachments.
In conclusion , this addendum has been prepared in accordance with the Fort Collins Stormwater
Criteria Manual and conforms to design completed with previous utility plans and drainage reports .
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II APPENDIX A
I DRAINAGE PLAN & VICINITY MAP
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I PROJEC
LOCATIO
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I VICINITY MAP
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,I APPENDIXB .
HYDROLOGY CALCULATIONS
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-- -- --------North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RUNOFF COEFFICIENTS & % IMPERVIOUS LOCATJON: PROJECT NO: COMPUTATIONS BY: DATE: Summitstone Health Partners 3 78-0 I ppk 4/30/2018 Recommended Runoff Coefficients from Table R0-11 of City of Fort Collins Design Criteria Recommended % Impervious from Urban Storm Drainage Criteria Manual Streets, parking lots (asphalt) Sidewalks Recycled Asphalt Roofs Lawns (flat <2%, heavy soil) I % Impervious 100% 90% 40% 90% 0% Runoff coefficient C 0.95 0.95 0.80 0.95 0.25 -SUBBASIN TOTAL TOTAL ROOF PAVED SIDEWALK REC. ASPHAL l LANDSCAPE DESIGNATION AREA AREA AREA AREA AREA AREA AREA (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) ALL ExistinQ 1.50 65,340 6,661 21,927 3,875 0 32,877 ALL Proposed 1.50 65,340 10,685 19,509 4,022 0 31,124 A 0.26 11,279 0 9,654 0 0 1,625 B 0.35 15,150 0 9,855 1,506 0 3,789 C 0.60 26,241 10,685 0 2,516 0 13,040 0 0.29 12,670 0 0 0 0 12,670 02 & 03** 7.81 340,204 76,950 77,500 0 0 185,754 02 & 03 Revised 7.81 340,204 80,974 75,082 147 0 184,001 -% Impervious 48% 50% 86% 74% 45% 0% 43.1% 44.4% •• Information taken from 'Final Drainage and Erosion Control Report for Centre Avenue Residences' by Northern Engineering dated October 13, 2009. Flow REV.xis Equations -Calculated C coefficients & % Impervious are area weighted . C = I: (Cl Ai)/ At Ci = runoff coefficient for specific area, Ai Ai = areas of surface with runoff coefficient of Ci n = number of different surfaces to consider At= total area over which C is applicable; the sum of all Ai's Cval -----RUNOFF RUNOFF COEFF. COEFF. (C) (C*1.25) 0.60 0.75 0.62 0.77 0.85 0.77 0.60 0.25 0.57 0.71 0.57 0.72
---North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: PROJECT NO: ----Summitstone Health Partners 378-01 COMPUTATIONS BY: ppk DESIGN POINT A B C D DATE: 2-yr storm SUB-BASIN DATA SUBBASIN(s) (1) ALL ExistinQ ALL Proposed A B C D EQUATIONS: tc =ti+ tt Cf= Area (ac) (2) 1.50 1.50 0.26 0.35 0.60 0.29 4/30/2018 1.00 INITIAL /OVERLAND TIME (ti) C Length Slope (ft) (%) (3) (4) (5) 0.60 0.62 0.85 56 1.0 0.77 42 1.0 0.60 22 2.0 0.25 10 20.0 ti= [1.87 (1.1 -CC1) L05J / S 113 --------STANDARD FORM SF-2 TIME OF CONCENTRATION - 2 YEAR TRAVEL TIME/ GUTTER OR CHANNEL FLOW tc CHECK (tt) (URBANIZED BASIN) ti Length Slope n Vel. tt tc= Total L tc=(l/180)+10 (min) (ft) (%) Manning (ft/s) (min) ti+ tt (ft) (min) (6) (7) (8) rough. (9) (10) (11) (12) (13) 3.4 210 0.5 0.016 1.4 2.46 5.8 266 11.5 3.8 200 0.5 0.016 1.4 2.35 6.1 242 11.3 3.3 233 0.1 0.030 0.3 11.46 14.8 255 11.4 1.8 460 0.1 0.030 0.2 31.99 33.8 470 12.6 tt = L/Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 minutes Flow REV.xis TOC-2 ----FINAL REMARKS tc (min) (14) 5.8 To Det Pond 6.1 To Det Pond 11.4 To Det Pond 12.6 To New Mercer
-- -North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: -PROJECT NO: COMPUTATIONS BY: DATE: 100-yr storm - --Cf= Summitstone Health Partners 378-01 ppk 4/30/2018 1.25 ------STANDARD FORM SF-2 TIME OF CONCENTRATION -100 YR SUB-BASIN DATA INITIAL /OVERLAND TRAVEL TIME/ GUTTER OR CHANNEL FLOW DESIGN POINT 0 0 A B C D SUBBASIN(s) (1) ALL Existinq ALL Proposed A B C D EQUATIONS: le= ti+ tt Area C (ac) (2) (3) 1.50 0.60 1.50 0.62 0.26 0.85 0.35 0.77 0.60 0.60 0.29 0.25 ti = [1.87 (1.1 -CC1) L 0·5 J / S 113 TIME (ti) C'Cf Length Slope (ft) (%) (4) (5) 0.75 0.77 1.00 56 1.0 0.97 42 1.0 0.75 22 2.0 0.31 10 20.0 (tt) ti Length Slope n Vel. tt tc = (min) (ft) (%) Manning {fl/s) (min) ti+ tt (6) (7) (8) rough. (9) (10) (11) 1.3 210 0.5 0.016 1.4 2.46 3.8 1.5 200 0.5 0.016 1.4 2.35 3.9 2.3 233 0.1 0.030 0.3 11.46 13.8 1.7 460 0.1 0.030 0.2 31.99 33.6 ----tc CHECK FINAL REMARKS (URBANIZED BASIN) tc Total L tc=(l/180)+1 O (ft) (min) (min) (12) (13) (14) 266 11.5 5.0 To Del Pond 242 11.3 5.0 To Del Pond 255 11.4 11.4 To Del Pond 470 12.6 12.6 To New Mercer tt = UVel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tl and urbanized basin check min. tc = 5 minutes Flow REV.xis TOC-100 ------------
-- -North Star Design, Inc. 700 Automation Drive, Unit I Windsor. CO 80550 Flow REV.xis - --LOCATION: PROJECT NO: COMPUTATIONS BY: DATE: 2-yr storm, Cf= Design Tributary Sub-basin Point ALL ExisUna ALL Proposed A A B B C C D D Q = CrCiA - -----RATIONAL METHOD PEAK RUNOFF (2-YEAR) Summitstone Health Partners 378-01 ppk 4/30/2018 1.00 DIRECT RUNOFF A C*Cf le (ac) (min) 1.50 0.60 1.50 0.62 0.26 0.85 5.8 0.35 0.77 6.1 0.60 0.60 11.4 0.29 0.25 12.6 Q = peak discharge ( cfs) C = runoff coefficient i (in/hr) 2.54 2.52 1.53 1.28 Cr = frequency adjustment factor i = rainfall intensity (in/hr) from IDF curve A= drainage area (acres) 02 CARRY OVER Q(2) from Q(2) Design (cfs) Point (cfs) 0.6 0.7 0.6 0.1 -- -----TOTAL REMARKS Q(2)tot (cfs) 0.56 To Det Pond 0.68 To Det Pond 0.34 To Det Pond 0.34 To New Mercer
----- -------North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: PROJECT NO: COMPUTATIONS BY: DATE: 100-yr storm, Cf= Des. Area Point Design. ALL Existina ALL Proposed A A B B C C D D Q=CiA bb Flow REV.xis RATIONAL METHOD PEAK RUNOFF (100-YEAR) Summitstone Health Pa1iners 378-01 ppk 4/30/2018 1.25 DIRECT RUNOFF A C*Cf tc (ac) (min) 1.50 0.75 1.50 0.77 0.26 1.00 5.0 0.35 0.97 5.0 0.60 0.75 11.4 0.29 0.31 12.6 Q = peak discharge ( cfs) C = runoff coefficient I Q (100) (in/hr) (cfs) 9.27 2.4 9.27 3.1 5.84 2.6 5.08 0.5 I = rainfall intensity (in/hr) from IDF curve A= drainage area (acres) 0100 CARRYOVER from Q (100) Design Point (cfs) ----- --TOTAL REMARKS Q(100)tot (cfs) 2.4 To Det Pond 3.1 To Det Pond 2.6 To Det Pond 0.5 To New Mercer
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APPENDIXC
DETENTION POND MODIFICATIONS
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LOCATION:
PROJECT NO :
M ODIFIED D ETENTION V OLUME REQ UIRED
FAA METHOD
(B ASINS D 2 & D3 , 100-YEAR)
Summitstone Health Partners
378-01
COMPUTATIONS BY: PPK
SUBMITTED BY: North Star Design , Inc.
4/30 /2018 D ATE:
Equations :
Q0 =C iA
Vi = T*CiA = T*Qo
V0 =K*Qp 0 *T
S =V i - V0
Rainfall intensity from City of Fort Collins IDF Curve
A trib . To pond =
C100 =
Developed C* A =
Qp o=
K =
7.81
0.72
5.6
1.4
Storm Rainfall Qo V ol. In V ol. O ut Sto r age
Duration, T Intensity, i
(min) (in/h r)
5 9.95
10 7.72
20 5.60
30 4.52
40 3.74
50 3.23
60 2.86
70 2.62
80 2.38
90 2.22
100 2.05
110 1.93
120 1.80
130 1.60
140 1.40
150 1.20
160 1.15
170 1.10
180 1.05
R equired Stor age Volum e :
(cfs)
56 .0
43.4
31.5
25.4
21.0
18 .2
16.1
14.7
13.4
12.5
11.5
10.9
10 .I
9.0
7.9
6.7
6.5
6.2
5.9
627 97
1.442
V;
(ft 3}
16785
26047
37788
45750
50474
54489
57896
61878
64239
67411
69165
71628
72877
70178
66 129
60731
62080
63092
63767
ft3
acre-ft
** (1.5 acres at 0.77 + 6.31 acres at 0.71) / 7.81 acre! = 0.72
Vo s
(ft3) (ft3)
420 16365
840 25207
1680 36108
2520 43230
3360 47114
4200 50289
5040 528 56
5880 55998
6720 57519
7560 598 51
8400 60765
9240 62388
10080 62797
10920 59258
11760 54369
12600 48131
13440 48640
14280 48812
15120 48647
acre
** see below
acre
cfs
(from fig 2.1)
Stor age
s
(a c-ft)
0.376
0.579
0.829
0.992
1.082
1.154
1.213
1.286
1.320
1.374
1.395
1.432
1.442
1.360
1.248
1.105
1.1 17
1.121
1.117
-------------------LOCATION: PROJECT NO: MODIFIED WATER QUALITY POND SIZE (BASINS D2& D3, 100-YEAR) Sununitstone Health Partners 378-01 COMPUTATIONS BY: PPK SUBMITTED BY: DATE: North Star Design, Inc. 4/23/2018 From Urban Storm Drainage Criteria/ Manual Use 40-hour brim-full volume drain time for extended detention basin Required Storage= a* ( 0.91 * 13 -1.19 * 12 + 0.78 * I) Water Quality Capture Volume = WQCV = (required storage/12)*(tributary drainage area) Trib. % lmperv. Req. Storage WQCV req. vol area from Fig. EDB-2 WQCV *1.2 (ac) (in. of runoff) (ac-ft) (ac-ft) Ex POND 7.81 43.1 0.188 0.122 0.1468 Rev POND 7.81 44.4 0.191 0.125 0.1495 (1.5 acres at 50.0% + 6.31 acres at 43.1 %) / 7.81 acres = 44.4% imperviousness
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STAGE -STORAGE TABLE
(100-YEAR)
LOCATION:
PROJECT NO:
Summitstone Health Partners
378-01
CALCSBY:
SUBMITIED BY:
DATE:
PPK
North Star D esign, Inc.
4/20 /2018
EXISTING POND
WQC Volume Required= 0.147
100 yr Detention Volume Required = 1.446
(On NGVD 1929 datum)
Surface Incremental Total
Stage Area Storage Storage
(ft) (ft2) (ac-ft) (ac-ft)
5039.20 645.33
5039.40 2450.42 0.007 0 .007
5039 .60 5291.24 0 .017 0 .024
5039.80 7639.85 0 .030 0.054
5040.00 9359.05 0.039 0.093
5040 .20 10856.29 0 .046 0.139
5040.23 11008.61 0.008 0.147
5040.40 11808.30 0.052 0 .191
5040.60 12559 .23 0 .056 0 .2 47
5040.80 13148.15 0.059 0.306
5041.00 14013 .52 0.062 0.368
5041.20 14680.0 1 0 .066 0.434
5041.40 15433.82 0 .069 0 .503
5041.60 16171.07 0.073 0.576
5041 .80 17156 .13 0 .076 0 .652
5042 .00 18654.88 0.082 0 .734
5042.20 20134 .80 0.089 0 .823
5042.40 21217.82 0.095 0 .918
5042.60 22292.83 0.100 1.0 18
5042 .80 23490.37 0.105 1.123
5043 .00 24775 .61 0.11 1 1.234
5043 .20 26 171.89 0 .117 1.351
5043.35 27239.15 0 .094 1.445
5043.40 27557.94 0.123 1.474
<=WQCV
<= 100 yr HWEL
M OD IFIED POND
WQC Volume Required = 0.149
I 00 yr Detention Volume Required= 1.442
(O n NA VD 1988 datum)
To convert from 1929 datum, ad d 3.18'
Surface ncrementa Total
Stage Area Storage Storage
(ft) (ft2) (ac-ft) (ac-ft)
5042 .38 645.33
5042 .58 2450.42 0.007 0 .007
5042.78 5291.24 0.017 0 .024
5042.98 7639.85 0 .030 0 .054
5043 .18 9359 .05 0.039 0.093
5043.38 10856 .29 0.046 0.139
5043.42 11046.69 0.010 0.149
5043 .58 11808.30 0.052 0 .191
5043.78 12559.23 0 .056 0 .2 47
5043 .98 13148.15 0.059 0 .306
5044 .18 14013.52 0.062 0 .368
5044.38 14680.01 0 .066 0.434
5044.58 15433 .82 0.069 0 .503
5044 .78 16171.07 0 .073 0.576
5044 .98 17156.13 0.076 0 .652
5045.18 18654 .88 0 .082 0.734
5045.38 20134.80 0.089 0 .823
5045.58 2 1217 .82 0.095 0 .918
5045.78 22292 .83 0.100 1.0 18
5045.98 23703 .95 0.106 1.124
5046 .18 24861.3 1 0 .111 1.23 5
504 6 .3 8 260 18.68 0.11 7 . 1.352
5046.53 2 6909.85 0.094 1.446
5046.58 27176.04 0.122 1.474
Modified values ( du e to ret wall ) have been shaded
<=WQCV
<=100 yrHWE
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Fi na l Drainage and Eros ion Con tr ol Report
for
Centre Avenue Res idences
(Being a Re -plat of Tract A and Tract C, Centr e for Adva~ced Technology P.U.D., Seyenth Fil ing)
Fort Collin s Colora · of t. Ii Plan ' AD1Df0V By . ~
JJ-& -C"i. C
Prepared for:
Mr. St a n Everi
Ever itt Com panies
3003 East Harmony Road, Su ite 400
Fort Co ll in s, Colorado 80528
Prepared by : I NORTHERN
] ENG l1N EER HiS
200 Sou-:n Collelll! Averu.1 Sui • l 00
Fo,t Collins, Colorado 80524
?11<,neo 970.221.4158 Fa,.; 970.221 4159
www.northeme:ngin og.com
Project Number : 1 10-034
bi s unoffic ial copy was do wnl oaded o n Se p-1 3-201 7 fro m th e Ci ty of Fort Collins Public Reco rds We bsite: http://citydocs .fcgov.co m
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APPENDIXB
Dete11tio11 and Water Quality Calculatio11s
•• _ _. his unofficial copy was downloaded on Sep-13-2017 from the City o f Fort Collins Public Records Website: http://citydocs.fcgov.com
---- - ----- --- --- ---- - - - --- --- ---- - -- -I NORTHERN tll01H££11111G Centre Avenue Residences DEVELOPED COMPOSITE o/o IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS CHARACTER OF SURFACE: Runoff Percentage Coefficient Impervious Project: Centre Avenue l~esidences Streets, Parking Lots, Roots. Alleys, and Drives: Calculations By: N. Haws Asphalt.............. .... .. . .... .. .............................................................. 0.95 100 Date: April 15, 2009 Concrete ............................................................................................. 0.95 90 Gravel ................................................................... .. ........... ... 0.50 40 Roofs ............................................................................................... 0.95 90 ?avers ................................................................................................ 0.40 22 Lawns and Landscaping Sandy Soil ................................................................................... 0.15 0 Clayey Soll .................... _ ....................... _ ............................................. 0.25 0 2-year C, "' l .00 10 vear C, ~ 100 lOO·year C, -1.2!i Runoff Coefficients 0,e la~en from lne City of rort Coll111s Storm Drninap,e Oes,gn Crilena and Construchon Stand~rris, Table 3-3. % lmpeM011s taken from UDFCD USDCM, VOlu111e I Area of Area of Area of Area of Area of 2-year 10-year 100-year Basin ID Basin Area Basin Area Asphalt Concrete Roofs Gravel Lawns and Composite Composite Composite Composite (s.f.) (ac) (ac) (ac) (ac) (ac) Landscaping Runoff Runoff Runoff % lmperv. (ac) Coefficient Coefficient Coefficient D2 & 03 340204 7.81 1.78 0.00 1.77 0.00 4.27 0.57 0.57 0.71 43.l 1. The purpose of this worksheet 1s to C{Jmpare the 100 yr Devclopcrt Runoff Coeff1c1enl PtOPo5erl with the rndcveloprnent of Tracts A & C to that previously assumer. with the CAT·7 DtAinage RePO 2. Areas listed are a composite of existing bu11cting5 .:inct parking w1lh1n Basins 02 ~nd D3, 35 well as the propnseti Site Pinn for Centre Avenue R1;>.sldenc1 3. Existing off.sue areas are taken from City GIS clata and aerial photography Prel,mmary Dmmagc 11nd Erosion Control Report D:\Proiects\110-034\Drninago\Hydrology\ 110-034 _ Tolal-Basm_ C-Va/oo.xls\C-Va/ues
---~-----------Centre Avenue Residences Pond Volumes 8/27/2009 Northern Pond Contour Contour Area Elevation (ft2) 5039.2 645.33 5039.4 2,450.42 5039.6 5,291.24 5039.8 7,639.85 5040 9,359.05 5040.2 10,856.29 5040.4 11,808.30 5040.6 12,559.23 5040.8 13,148.15 5041 14,013.52 504U 14,680.01 5041.4 15,433.82 5041.6 16,171.07 5041.8 17,156.13 5042 18,654.88 5042.2 20,134.80 5042.4 21,217.82 5042.6 22,292.83 5042.8 23,490.37 5043 24,775.61 5043.2 26,171.89 5043.4 27,557.94 Incremental Depth (ft) 0.0 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 -------------Avg. End Area Avg. End Area Conic Incremental Cummulative lncren1ental Volume (ft3) Volume (ft3) Volume (ft3) 0 0 0 309.58 309.58 290.22 774.17 1083.74 756.16 1293.11 2376.85 1285.94 1699.89 4076.74 1696.98 2021.53 6098.27 2019.68 2266.46 8364.73 2265.79 2436.75 10801.48 2436.37 2570.74 13372.22 2570.51 2716.17 16088.39 2715.71 2869.35 18957.74 2869.09 3011.38 21969.12 3011.07 3160.49 25129.61 3160.2 3332.72 28462.33 3332.23 3581.1 32043.43 3580.05 3878.97 35922.4 3878.03 4135.26 40057.66 4134.79 4351.07 44408. 73 4350.62 4578.32 48987.05 4577.8 4826.6 53813.65 4826.03 5094.75 58908.4 5094.11 5372.98 64281.38 5372.39 Conic CL1mmulative Average Volume (ft3) Volume (ft3) 0 0 290.22 300 1046.38 1,065 2332.32 2,355 4029.3 4,053 6048.99 6,074 8314.78 8,340 10751.15 10,776 13321.66 13,347 16037.37 16,063 18906.46 18,932 21917.53 21,943 25077.73 25,104 28409.97 28.436 31990.02 32,017 35868.05 35,895 40002.84 40,030 44353.46 44,381 48931.26 48,959 53757.29 53,785 58851.4 58,880 64223.79 64,253 Average Volume (adt) 0.00 0.01 0.02 0.05 0.09 0.14 0.19 0.25 0.31 0.37 0.43 0.50 0.58 0.65 0.74 0.82 0.92 1.02 1.12 1.23 1.35 1.48 Water Quality Volume= 0.147 Jc-ft WSEL :: 5040.23 100-yr Detention Volume= 1.446 ac-ft WSEL = 5043.35 --"
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APPENDIXD
EROSION CONTROL SURETY
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Erosion and Sediment Control Escrow/Security Calculation
for The City of Fort Collins
Project: SUMMITSTONE HEAL TH PARTNERS
BMP Amount
Estimated
Disturbed Acres: 0 .21
EROSION CONTROL BMPs Units Quantity
Unit
Price
Silt Fence
Rock Sock
Rock Berm
Vehicle Tracking Control Pad
Concrete Washout
Inlet Protection
L.F. 302 $3.00
$85.00
$220.00
$1 ,500.00
$1,200.00
$210 .00
each 6
each 0
each 1
each 1
each 0
Reseeding Amount
Sub-Total :
1.5 x Sub-Total:
Amount of security:
Total Acres x Price/acre:
Unit Price of Seeding per acre: $1,200.00 Sub-Total :
1.5 x Sub-Total:
Amount to Re-seed:
Miniumum Escrow Amount
Minimum escrow amount:
Total
Price
$906.00
$510.00
$0.00
$1,500.00
$1,200.00
$0.00
$4,116.00
$6,174.00
$6,174.00
$252 .00
$252 .00
$378.00
$378.00
$3,000.00
$6,174.00
"The amount of the security must be based on one and one-halftimes the estimate of the cost to install the approved measures, or one and one-halftimes
the cost to re-vegetate the disturbed land to dry land grasses based upon unit cost def.ermined by the City's Annual Revegetation and Stabilization Bid,
whichever is greater. In no instance, will the amount of security be less than one tlwusandjive hundred dollars ($1,500) for reside/Ilia/ development or three
thousand dollars ($3 ,000)for co mmercial development"
10/26/2017 3:54 PM N:1378--01 summit SIOne\Drainage\ErosionEscrow.xls
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APPENDIXE
EROSION & SEDIMENT CONTROL REPORT
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EROSION & SEDIMENT CONTROLS
1.0 Written Analysis
An Erosion and Se<limenl Cunlrnl Plan is indu<le<l herewith. It should be noted, however,
that any such Erosion and Sediment Control Plan serves only as a general guide to the
Contractor. Staging and/or phasing of the BMPs depicted, and additional or different BMPs
from those included may be necessary during construction, or as required by the authorities
having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are
properly maintained and followed. The Erosion and Sediment Control Plan is intended to
be a living document, constantly adapting to site conditions and needs. The Contractor shall
update the location of BMPs as they are installed, removed or modified in conjunction with
construction activities. It is imperative to appropriately reflect the current site conditions
at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be
implemented during construction, as well as permanent erosion control protection. Best
Management Practices from the Volume 3, Chapter 7 -Construction BMPs will be utilized.
Measures may include, but are not limited to, silt fencing along the disturbed perimeter,
gutter protection in the adjacent roadways and inlet protection at proposed storm inlets.
Vehicle tracking control pads, spill containment and clean-up procedures, designated
concrete washout areas, dumpsters, and job site restrooms shall also be provided by the
Contractor.
Grading and Erosion Control Notes can be found on Sheet 2 of the Utility Plans. In addition
to this report and the plan sheets, the Contractor shall be aware of and adhere to the
applicable requirements outlined all Development Agreements pertaining to this property.
Also, the Site Contractor for this project will be required to secure a Stormwater
Construction General Permit from the Colorado Department of Public Health and
Environment (CDPHE), Water Quality Control Division -Stormwater Program, before
commencing any earth disturbing activities. The Contractor shall also develop a
comprehensive Storm Water Management Plan (SWMP) conforming to applicable
requirements including descriptions of the ongoing activities, inspections and maintenance
of construction BMPs.
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The site is approximately 1.50 acres and approximately 9300 square feet of which will
undergo earthmoving operations. The existing site has an existing building, parking lot and
landscaping cover approximately 75% of the site and an irrigation ditch that covers
approximately 20% of the site.
Runoff from this site currently discharges into an existing detention pond and the
improvements will continue this runoff pattern .
The soils on this site are classified by the USGS Soil Survey as Nunn Clay Loam and are
classified in the hydrologic group C. These soils are characterized as having a slow
infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that
impedes the downward movement of water or soils of moderately fine texture or fine
texture. These soils have a slow rate of water transmission. The rainfall erodibility is
deemed to be moderate and the wind erodibility is deemed to be moderate to high.
The site is surrounded by developed sites including streets , buildings and paved areas . The
construction shall utilize silt fence around the perimeter to control sediment transport from
rainfall and from wind. The silt fence that is located in the proposed pavement areas will
be removed prior to placing new pavement. Rock socks will be utilized in the exi sting curb
and detention pond to capture sediments that are not fully contained by the silt fence
placement. The locations of the rock socks will be in the areas of concentrated flow such
as in the existing curb and on the concrete pans.
The site will also utilize a vehicle tracking control pad to minimize sediment from being
tracked onto adjacent pavements. Sediment that is tracked will be removed and placed
within the site or permanently disposed of offsite. A concrete washout will be used on site
during the concrete placement. All hardened concrete will be disposed of offsite. · These
BMP's have not been located on the site map due to the fact that the site is very small and
these BMP 's will need to be placed by the contractor in locations that are mo t beneficial
and will minimize disruption of adjacent traffic.
Permanent erosion control consists of covering the soils with a building, concrete walks ,
concrete pavement, recycled asphalt pavement and sod. No soil will be left exposed to
erosion after the construction is complete. Refer to the landscape plan for areas of and
instructions for placement of sod and soil amendments required prior to placement of sod .
Refer to Appendix D for the Erosion Control Surety calculations.
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2.0 SWMP contact information
Permit holder:
Name:
Address :
Phone Number:
Email Address:
Appointed agent:
Name:
Address :
Phone Number:
Email Address:
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30 Id f fi t en 1 1ca 10n an dl t oca 10n o f 11 a t t I po en 1a po 11 t u 10n sources
~
Potential Pollutant Applicable to Control Measure Potentia! Pollutant Source Activity Generated this project
Disturbed Areas Sediment X Silt Fence, Rock Socks
Soil stockpiles Sediment X Silt Fence, Rock Socks
Travel to adjacent public streets Tracked sediment X Tracking Pad, street sweeping
Contaminated soils , Sediment, chemicals Possible Remove contaminated soils
from site **
Loading and unloading chemicals Chemicals
Unloading of building materials Trash , debri s X Trash dumpsters , Waste
Management Firm**
Outdoor storage of chemicals Chemicals
On site equipment maintenance Oil, grease
On site equipment fueling Diesel, gasoline X Containment berm**
Dust generating activities Particulates, sediment X Water truck
Use of fertilizer, pesticides, herbicides Fertilizer, pesticides
If spilled, remove
Use of detergents, solvents, oils Detergents , solvents, oil X contaminated soils from site
**
Waste dumpsters, waste piles Chemicals , trash , debris X Waste Management Firm
Concrete washout Concrete, sediment , wash X Remove hardened concrete,
water dispose of offsite **
On site equipment washing Detergents , oil
On site asphalt batch plant Asphaltic cement, sediment
On site concrete batch plant Cement, sediment
Portable toilets Domestic sewage X Waste Management Firm
** Refer to Section 1.5.2 for additional Materials Handling & Spill Prevention BMP
4.0 Best Management Practices (BMP's) for Stormwater Pollution Prevention
Structural Practices for Erosion and Sediment Control
Structural practices for the site will consist mainly of silt fence and rock sock filters and
are described in detail in the following paragraphs. These BMP's are expected to change as
the construction progresses and it is the responsibility of the contractor to ensure
appropriate BMP's are in place and/or removed at the appropriate time in the construction
sequence. All temporary and permanent erosion and sediment control practices must be
maintained and repaired as needed to assure continued performance of their intended
function .
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Silt fence and rock sock filters shall be in place prior to commencement of construction
activities. During clearing and grubbing necessary for silt fence installation, all cleared
material shall be placed on the uphill side so that if erosion occurs from the cleared
material, the sediment will be trapped and not transported downstream. Rock socks shall
be implemented in the existing curb line as shown on the Drainage & Erosion Control Plan.
All BMP's shall be installed per the details shown on the construction plan set.
Temporary & Permanent Structural BMP's:
Structural BMP Approximate location on site Applicable to this
Project
Silt Fence Site perimeter, refer to site map X
Straw bale dams
Rock Socks At existing sidewalk culverts , in existing X gutters, refer to site map
Earthen diversion dams
Vegetated swales
Sediment trap/pond
Pipe slope drains
Geogrid
Inlet/outlet protection In the detention Pond X
Culverts Refer to site map X
Riprap
Erosion control mats
Inlet protection
Vehicle Tracking Control Pad At site entrance, refer to site map X
Concrete Washout To be located by Contractor X
Non-Structural Practices for Erosion and Sediment Control:
Soil s exposed during the earthwork phase and landscape prep phase shall be kept in a
roughened condition by ripping or disking along land contours until mulch, vegetation, or
other permanent erosion control is installed . No large amount of soils (in excess of 15
yards) will be allowed to be stock piled on site. Overburden from the utility pipe trenching
will be piled adjacent to trenches upstream of sediment controls and will be replaced in the
trenches within 72 hours.
Excess excavated materials from the demolition and grading phases of the project that
cannot be reused on site will be exported as it is excavated. This includes any asphalt
pavement from the existing site that is to be removed.
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A vehicle tracking pad will b e installed at a location most b eneficial to the site construction
as determined by the contractor. Vehicles will not be permitted in the excavated area if
soil is muddy. Gravel sub base will be placed and compacted in the areas indicated for
pavement following excavation. In the current pre construction state the site enab les
tracking of silt onto the adjacent streets during wet conditions. During construction
activities the street will be monitored for foreign debris tracked out of the site and
mechanical sweeping and clean up will be performed as needed .
No area shall remain exposed by land disturbing activity for more than thirty (30) days
before required temporary or permanent erosion control ( e.g. seed/mulch, landscaping,
etc .) is installed.
T emp orary & Permanent non-structural BMP's:
Non-Structural BMP Approximate location on site Applicable to this
Project
Surface roughening
Soil stockpile height limit (less than
10')
Perimeter vegetative buffer All boundaries of site X
Minimization of site disturbance
Mulch
Seed & mulch stockpiles after 30
days
Stockpile toe protection (silt fence ,
wattles or ditch)
Preservation & protection of existing All boundaries of site X vegetation & trees
Good site ho usekeeping (routine Entire Site X cleanup of trash & cons tr debris)
Sweeping & scraping ofhardscape On and off site pavements X areas
Heavy equip staged on site, properly
maintained & inspected daily (no Staging area X
onsite maintenance)
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5.0BMP Implementation
5.1 Phased BMP Implementation
BMP's are expected to change as the construction progresses and it is the responsibility of
the contractor to ensure appropriate BMP's are in place and/or removed at the appropriate
time in the construction sequence . A construction sequence schedule has been included on
the Drainage & Erosion Control Plan and included in the construction plans for this site.
All BMP's shall be inspected and repaired or replaced as required to satisfy the conditions
of the Stormwater Discharge Pennit. All BMP's must be maintained and repaired as
needed to assure continued performance of their intended function. Refer to Appendix E
for the BMP schedule and estimated costs .
5.2 Mat . 1 H dl" ena s an mg an d S ·11 P ,pl t reven 10n :
Materials Handling & Spill Prevention BMP Approximate location on site Applicable to
this Project
Portable toilets, anchored & located away from Contractor to determine X drainages
Fuel storage located in bulk tanks with secondary
containment & spill kit
Mobile fueling performed at least 200 feet away from Contractor to determine X drainages & fully attended
Fertilizers, form oil, solvents , cleaners, detergent
stored in 55 gal or smaller containers, kept in storage Contractor to determine X
units
Dumpsters containing used chemicals containers & Contractor to determine X liquid wastes kept covered
Equipment cleaning (on site) uses no detergents &
flows to onsite retention basin
In case of a release of fuel or other chemicals ,
absorbent booms or earthen berms will be Location of spill X immediately constructed to contain the spill &
prevent runoff to adjacent surface waters
MSDS sheets for onsite chemicals will be kept at the
construction trailer to facilitate spill response & Contractor to determine X
cleanup
5 .3 Dedicated Asphalt or Concrete Batch Plant:
Not proposed with this development
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5.4 Vehicle Tracking Pad:
Vehicle tracking control pad shall be installed wherever construction vehicle access
routes intersect paved public roads. Vehicle tracking control pads shall be installed to
minimize the transport of sediment (mud) by runoff or vehicles tracking onto the paved
surface. Any mud tracked to public roads shall be removed on a daily basis and after any
significant storm that causes sediment to be transported. It is unlawful to track
sediment/mud onto public streets and may be enforced by the City of Fort Collins, by the
State of Colorado or by the EPA.
5.5 Waste Management and Disposal:
Portable toilets will be anchored & periodically maintained by waste management
company. Dumpsters on site will be covered & periodically emptied by waste management
company. Concrete waste will be allowed to harden and then will be removed from site.
No washing activities will occur on site.
Location of the concrete washout is shown on the site map . The washout will be sufficiently
deep to accommodate all anticipated concrete truck wash water. Waste concrete will be
allowed to harden and be removed from site periodically as the washout reaches 50% of its
capacity. Truck wash water will not be allowed to reach the curb & gutter or any other
water course.
5 .6 Groundwater and Stormwater Dewatering:
No groundwater was encountered during soils exploration therefore ground water is not
anticipated to be an issue . If groundwater is encountered a groundwater discharge permit
shall be obtained and a detailed report shall be completed describing the location and the
route of where pumped groundwater will be conveyed and the measures taken to prevent
the transport of any pollutants to downstream waters.
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5.7 Inspection & Maintenance:
It is required that routine site inspections are performed to effectively address maintenance
and repair of Best Management Practices (BMP 's). The site inspections are to perfonned
by the contractor or an inspector designated by the administrator at a minimum of once
every fourteen (14) calendar days on active construction sites and after any significant
storm event (an event causing runoff). As part of the site inspections the inspector is
required to keep documentation of all inspections and BMP maintenance , including an
updated Site Map indicating new BMP's or the removal of BMP's since the previous
inspection.
Any maintenance , repair, or necessary installation of BMP 's that are noted during the
inspection must be completed within seven (7) calendar days from the date of the
inspection.