HomeMy WebLinkAboutStudies APPLICANT 8/24/2021HORACE STREET APARTMENTSDRAINAGE STUDY
July 27, 2021
SITE CHARACTERISTICS
The subject properly is identified on County Assessor's Maps as 18-20-05-23-0204. It is located on the south side of
Horace Street, east of Filbert Sl. The site is an open field and consists of about 0.74 acres.
EXISTING HYDROLOGY
The site is relatively flat and portions of the site drain to the north.
PROPOSED HYDROLOGY
There is approximately 18,204 square feel of impervious area that will be directed towards a filtration planter on site. The
required size of the filtration planter was determined by the City of Eugene Stormwaler Surface Filtration/Infiltration
Facility Sizing Spreadsheet and was sized for flow control. The required filtration planter is 1,450 square feel, with 1,589
square feel provided. Attached are the calculations.
CONCLUSION
Based on my calculations and the proposed drainage system is sized properly and will provide the necessary flow control.
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Stormwater Surface FiltrationAnfiltration Facility Sizing Spreadsheet
24 Hour Storm, NRCS Type 1 A Rainfall Distribution
City of Eugene
Name:
Horace St.2 Unit Apmtmr
Address:
Horace
Impervious Area CN=l
Sorinafield. OR [Zip Codel
or:
Anthony J. Fayreau
TY:
The Fmmeeu Group
Date: 7/8/2021
Permit Number: Permit
CatchmentlD: Entire Subdivision
Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach.
Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate
calculations with the facility.
The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF)
=or infiltration facilities in Class A or B soils where no infiltration testing has been per romed use an infiltration rate of 0.5 in/for.
For all facilities use a maximum soil infiltration rate of 2.5 in/hr for lommi/growing medium.
loses'Ym' from the dmpdown loxes below next to the design standards requirements for this facility.
Pollution Reduction (PR)Yes
Flow Control (FC)j Yes
Destination(DT) No 'Animiio-ationkciiiry rnuA1vrhsenas memr1l1Vrvem rroOcivsonmion 2qui2rrow
Total Square Footage Impervious Area=
=5
sgfl
Total Square Footage Pervious Area= 14209 sqN
Impervious Area CN=l
98
Flow Control
Pervious Area CN=l 85
Total Square Footage of Drainage Area=
31925
sfi
Time of Concentration Post Development= min
Weighted Average CN=l
92
Pre�Development CN= 85 Time of Concentration Pre�Development= 10 min
Tested Soil Initiation Rate= 1 rotor (Soo role 4) Destination Design=®iNhr
Design Soil Infiltration Rate=Iin/hr Soil Infiltration Rate
R uirement
Rainfall De h
Desi nStorm
Stoma
P011otlonlVuIlon
1.4inches
Water
Flow Control
3.6 inches
Flood Control
Destination
I 3.6 inches
Flood Control
Facility
Max. Ponding Depth
in Stormwater Facility=
Depth of Growing Medium (So
]/2]/2021-3:24 PM
Facility Surface
Facility Surface Pern
Facility Bottom
Facility Bottom Pern
Ratio of Facility Area to
Basin Vc
Pollution Reduction-Calculation Results
Peak Flow Rate to Stormwater Facility = 0.136 cfs
Pik Facility Overflow Rate= 0.000 cfs
Total Runoff Volume to Stormwater
Facility 193] cf
Total Overflow Volume= 0 cf
Max. Depth of Stormwater in Facility= 2.0 in
Drawdown Time= 02 hours
Yes Facility Sizing Meets Pollution Reduction Standards?
VES Meets Requirementof No Facility Flooding?
VES Meets Requirement for Maximum of 18 Hour Drawdown Time?
Flow Control-Calculation Results
Peak Flow Rate to Stormwater Facility = 0.579 cfs
Peak Facility Overflow Rate= 0.358 cfs
Total Runoff Volume to Stormwater
Facility= 718 cf
Total Overflow Volume= 3297 cf
Peak Off -Site Flow Rate
Max. Depth of Sierra in Facility= in
Filtration Facility Underdrain= 0.034 cfs
Drawdown Timms hours
Pre-Development Runoff Data
Peak Flow Rate = 0.362 cfs
Total Runoff Volume =1 5597 cf
=Facility Sizing Meets Flow Control Standards?
VES Meets Requirement for Post Development offsite flow less or equal to Pre-Development Flow?
VES Meets Requirement for Maximum of 18 Hour Drawdown Time?
Destination-Calculation Results
Peak Flow Rate to Stormwater Facility = N/A cfs
Peak Facility Overflow Rate= N/A cfs
Total Runoff Volume to Stormwater
Facility= N/A cf
Total Overflow Volume= N/A cf
Max. Depth of Stormwater in Facility- N/A in
Drawdown Time= N/A lours
N/A Facility Sizing Meets Destination Standards?
=Meets Requirement of No Facility Flooding?
L.2LAJMftt, Requirement for Maximum of 30 hour Drawdown Time?
7/0/2021-3:24 PM