HomeMy WebLinkAboutStudies APPLICANT 6/11/2021HORACE STREET APARTMENTS DRAINAGE STUDY
May 12, 2021
SITE CHARACTERISTICS
The subject properly is identified on County Assessor's Maps as 18-20-05-23-0202. It is located on the south side of Horace
Street, east of Filbert Sl. The site is an open field and consists of about 0.31 acres.
EXISTING HYDROLOGY
The site is relatively flat and portions of the site drain to the north.
PROPOSED HYDROLOGY
There is approximately 9,000 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 SIM Form and was sized for flow control. The
required filtration planter is 630 square feel, with 658 square feet 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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SIM FORM: 2014 (Simplified Approach for Stormwater Management)
Application Building Permit #
Address
Resid entia I/Com m erci al
Tax Lot# 18-20-05-23-0202 Icrc o.e)
NRCS Soil Type or Soil Group B
Measured Infiltraiton Rate
Total Proposed New or Replaced Impervious Surface Area
Box 1
Impervious Area Reduction
Permeable Pavements sf
Eco -Roof sf
Contained Planter sf
Tree Credit sf
Total Impervious Area Reduction
>Box 2
Total Impervious Area Requiring Stormwater Managemment
Box 3
(eox 1-eox 2)
Facility Sizine for Water Quality Only
Surface Facilities Impervious Area Managed Sizing
Factor
Faclity Surface Area
Rain Garden sf x
0.05 =
Stormwater Planter sf x
0.03 =
Swale sf x
0.06 =
Vegetated Filter Strip sf x
0.2 =
Sand Filter sf x
0.03 =
Facility Sizine for Water Ouality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 =
Stormwater Planter 9000 sf x 0.07 = 630
Sand Filter sf x 0.07 =
Facility5izine for Water Quality, Flow Control and Flood Control "' Only for use in Type A & B Soils
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.13 =
Stormwater Planter sf x 0.11 =
Sand Filter sf x 0.11 =
Sum of Total
Impervious Area Managed Box Point of Discharge (check one)
(Box 4 must be equal or
greater than Box 3) Overflow to gutter(weephole)
Overflow to public storm drain pipe
Overflow to Open Drainage
Subsurface Infiltration
2014 SIM FORM: Tree Credit and Rainwater Harvesting Wor s eet
See "Tree Credits" section for more Information regarding the use of Reesto meet Stormwater Impervious Area Reduction.
New Evergreen Trees
To receive Impervious Area Reduction Credit, new evergreen trees must be planted within 25 feet of the oew, or replaced impervious
surfaces. New trees cannot be credited against rooftop areas. Minimum tree Might (at the time of planting) to receive credit is 6 feet
Enter number of new evergreen trees that meet qualification requirements in Box A BBo%A
Multiply Box A by 200 and enter result in Box B Box B
New Deciduous Trees
To receive Impervious Area Reduction Credit, new large deciduous trees must be planted within 25 feet of the newer replaced
impervious surfaces and new small deciduous trees must be plants! within 10 feet of new or replaced impervious surfaces. New
trees cannot be credited against rooftop areas. Minimum tree caliper (at the time of planting) to receive credit is 2 inches.
Enter number of new deciduous trees that meet qualification requirements in Box C Box C
Multiply Box C by 100 and enter result in Box D Box D
Existing Tree Canopy
To receive Impervious Area Reduction Credit, existing large tree carwpies must be within 25 feet and existing small tree canopies
must be within 10 feet ofground-level impervious surfaces(camet be credit against rooftop surfaces). Existing tree carwpy
credited towards Impervious Area Reduction must be preserved during and after construction throughout the life of the development
Minimum tree caliper m receive credit is 4 inches. No credit will be given to existing tree canopy located within environmental
conservation areas.
Enter square footage of existing tree canopy that meet qualification requirements in Box E. F—]BoxE
Multiply Box Eby 0.5 and enter result in Box F.
Box F
Total Tree Credit
Add Boxes B, D and F and enter the result in Box G
Box G
Multiply Box I of Form SIM by 0.1 and enter the result in Box H.
Enter the lesser of Box G and H in Box 1. mals Is tat amount to be entered as "Tree Credit" on Form SIM.)
SIM FORM 2014 Instructions
1. Enter square footage (sf) of total impervious area being developed into BOX 1.
2. Enter square footage(sf) for impervious area reduction techniques.
3. Enter sum of the impervious area reduction techniques into BOX 2.
4. Subtract BOX 2 from BOX 1 to find BOX 3, the amount of impervious area that requires stormwater management.
5. Select appropriate stormwater management facilities.
6. Enter the square footage of impervious area managed that will flow into each facility type.
7. Multiply each impervious area managed by the corresponding sizing factor. Enter this area as the facility surface area,
This is the size of faclity required to manage runoff
9. Where selecting facilities that will overflow, select the point of discharge location.
10. Enter the sum of the total of all the impervious area managed into BOX 4. BOX 4 must be greaer than or equal to BOX 3.