HomeMy WebLinkAboutGrading Plans - 06/08/2022�J
Fetzer Engineering, L.1.0
June 5, 2022
Owner
609 E Plum St
Fort Collins, CO 80521
RE: Drainage Memo
for 609 E Plum St, Fort Collins, CO
Dear Owner;
Grading/Stormwater Plan Accepted
(Building Permit Released)
Accepted by: Dan Mogen
Date: 06/08/2022
Attached is a drainage plan showing the location of your proposed garage and the grading around this
proposed structure to mitigate the additional flows that will be generated due to the new impervious
area. Drainage calcs which show these additional flows which will be produced are also attached. All
planned downspouts of the garage are located on the west side of this structure and will be piped
underground to the rock pit. As a result of installing and routing runoff from the garage to the infiltration
sump, runoff from this garage building is effectively mitigated and no adverse impacts to adjacent
properties are anticipated. Rock sump has been sized per Fort Collins Drainage Manual criteria. Please
refer any questions to myself at the contact information provided below. Thank you
Shawn Fetzer, P.E.
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6/5/2022
Disclaimer:
This document, together with the concepts and recommendations presented herein, as an instrument of service, is
intended only for the specific purpose and client for which it was prepared. Reuse of and improper reliance on
this document without written authorization from Fetzer Engineering LLC shall be without liability to Fetzer
Engineering LLC
Fort Collins, CO (970) 702-4884
609 Plum St, Fort Collins Detention Calcs
Modified FAA Procedure - Assuming Storing Additional Post 100 yr Flows from 672 SF Garage Only
Proposed Existing
Time 100 Year 100 Year
Duration Cproposed** I* A(ac) Q(cfc) V(cf) �ex;sc;og** I* A(ac) Q(cfs) V(cf)
5 0.95 9.95 0.02 0.146 43.747 0.50 9.95 0.02 0.077 23.025
10 0.95 7.72 0.02 0.113 67.885 0.50 7.72 0.02 0.060 35.729
15 0.95 6.52 0.02 0.096 85.999 0.50 6.52 0.02 0.050 45.263
20 0.95 5.60 0.02 0.082 98.486 0.50 5.60 0.02 0.043 51.835
25 0.95 4.98 0.02 0.073 109.478 0.50 4.98 0.02 0.038 57.620
30 0.95 4.52 0.02 0.066 119.238 0.50 4.52 0.02 0.035 62.757
35 0.95 4.08 0.02 0.060 125.570 0.50 4.08 0.02 0.031 66.089
40 0.95 3.74 0.02 0.055 131.549 0.50 3.74 0.02 0.029 69.236
45 0.95 3.46 0.02 0.051 136.913 0.50 3.46 0.02 0.027 72.060
50 0.95 3.23 0.02 0.047 142.013 0.50 3.23 0.02 0.025 74.744
55 0.95 3.03 0.02 0.044 146.542 0.50 3.03 0.02 0.023 77.127
60 0.95 2.86 0.02 0.042 150.895 0.50 2.86 0.02 0.022 79.418
65 0.95 2.71 0.02 0.040 154.896 0.50 2.71 0.02 0.021 81.524
70 0.95 2.59 0.02 0.038 159.424 0.50 2.59 0.02 0.020 83.907
75 0.95 2.48 0.02 0.036 163.557 0.50 2.48 0.02 0.019 86.083
80 0.95 2.38 0.02 0.035 167.426 0.50 2.38 0.02 0.018 88.119
85 0.95 2.29 0.02 0.034 171.163 0.50 2.29 0.02 0.018 90.086
90 0.95 2.21 0.02 0.032 174.900 0.50 2.21 0.02 0.017 92.053
95 0.95 2.13 0.02 0.031 177.934 0.50 2.13 0.02 0.016 93.650
100 0.95 2.06 0.02 0.030 181.144 0.50 2.06 0.02 0.016 95.339
105 0.95 2.00 0.02 0.029 184.661 0.50 2.00 0.02 0.015 97.190
110 0.95 1.94 0.02 0.028 187.651 0.50 1.94 0.02 0.015 98.764
115 0.95 1.88 0.02 0.028 190.113 0.50 1.88 0.02 0.015 100.060
120 0.95 1.84 0.02 0.027 194.158 0.50 1.84 0.02 0.014 102.188
* Rainfall Intensity per Table 3.4.1 of Fort Collins Drainage Manua�
** C-values are based on Table 31.2 in the FC Drainage Manual. Proposed surface is a Rooftop at 0.95 and Existing is gravel at 0.50
Total Detention Required = 91.970 CF
Detainage Rock Sump Size
Width 10 FT
Length 10 FT
Depth 4 FT
Void % 25%
100 CF
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609 E PLUM ST
PARCEL N0. 9�13235092
NOTES
+. PRO?0�� SLOP 5 SHALL BE NO StEfPER 1HAN a::. SLOPES AWAY Ff20M GARAG"e SrIALL HE NO L"e55 iNAN 59
2. No iCaOGRP.PN�C -uRVCY W�5 pp?AirvF.G FOR Pi!5 S:i£.
1 NO l,'P.I..I'1S ARE SHOWN ON �IS �I.AN ;,iERE MAY 9E BIIRIE� UPLiTES ON OR Ap,�ACENT TO T4LS �R(1PF.RS" iHAT
ARE N�JT SHQWN GUE TO :NSU�FlLYENT SJRFq@` EVIDENCE. :JO STAi�MENT iS MADE CONC�fNiNP SUBSURFACE
CO�CIfI0N5 OF l+E EX-STENCE 9F OVENHEAL OR 11NCfJ2Gh011N[1 CONLAI.IE45 tr� FACILIiIES WMiCH MAT AFFECI TI;E
U4 1(�M�N� Oi IH�.S sil'F.-
GRAUING PLA� FOH oL9 �LLM S -�kPEftN0U5 AREA
d'JtLCING PF�U.I� pxxux GARAGF - 5�6 SF
:OYTACTIN-C�M�-�C�N CONCFCTE �RIVE - 96 SF
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Know whaFs bCIOW.
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4' �EPP�. CGVE4 W�P1 6' i0P5011. PROPOSE� ROOF GUTTER
TOP � �VAiIOry m 6" LOWEft piPE 40 NOCK SUM.V
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