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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. ���vED P%PT� ,�� z NZ 's01'824 OREGON J ti 11.195h CvQ' Vy �, FPS EXPIRES DEC. 31. 2021 9 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.