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Home My WebLink AboutStudies APPLICANT 7/28/2021TAX LOTS 17-02-33-42-00300 & 00700, SPRINGFIELD INFILTRATION RATE June 11, 2021 The site is a vacant lot with mowed grass. NRCS soil classification maps identify this site as having Class C soils. One test hole was dug onsite in the approximate location of one of the proposed infiltration rain garden. The test hole was dug to approximately 6 feet deep. Ground water was not encountered. The infiltration rate was conservatively determined to be about r per hour. For purposes of determining the rain garden size, an infiltration rate of 0.5" per hour was used. FACILITY SIZING An open drainage channel exists on the south side of B Street, although the City has determined that this drainage channel has not been sized to accommodate runoff from this private development. Because of this, the proposed stormwater system has been broken up into several facilities. There will be three private soakage trenches sized to accommodate runoff from each home plus 1/3 of the driveway surface area. Since DEQ does not consider driveway runoff clean, the driveway will first drain towards a surface rain garden that is sized to treat the entirety of the driveway runoff during the water quality storm. Please see attached SIM form demonstrating proper sizing for the treatment of the driveway for treatment only. For events larger than the water quality storm, runoff from the driveway will enter into an overflow that will be piped to the inlet pipe for the soakage trenches, where the runoff will be mitigated up to the 25 -year storm (see attached soakage trench sizing calculations). These facilities will be constructed underneath the proposed driveway and will have separation between each of them for maintenance and ownership purposes. An overflow pipe from the most downstream soakage trench will be constructed that will connect to the existing drainage channel on the north side of B Street. This overflow should only be utilized for events larger than the 25 -year storm. Based on this narrative and provided calculations and details, the proposed stormwater system complies with the City's stormwater criteria, 5��4�p PROFESS �� mnFE k /oZ w OREGON s 1a N`* FP. T2, 15 J rC J. FAV Pf'P i FJPIIES �2iNTl f SIM FORM: 2014 (Simplified Approach for Stormwater Management) Application Chad Wilson Partition (Driveway) Build Ing Permitil Address 5524 R St Springfield, OR 97478 CResidential ommercial Tax Loaf 17-02-33-42-00300 & 00700 lar<ieone) NRCS Soil Type or Measured lnfiltraiton Rate 0.5"/hr Total Proposed Newer Replaced Impervious Surface Area 1 2079 Box 1 Impervious Area Reduction Permeable Pavements If Eca-Roof If Contained Planter If Tree Credit If Facility Sizinefor Water Quality Flow -Control and Flood Control"' Only for use in Tvne A&BSolis Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area Total Impervious Area Reduction sf x Box 2 P2079Box Total Impervious Area Requiring Stormwater Managemment Stormwater Planter > 0.11 = Sand Filter If x Facility Sizing for Water Quality Only Sum of Total Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area Rain Garden 2079 IF x 0.05 = 104 Stormwater Planter sf z 0.03 = Swale If x 0.06 = Over flow [o gu[terlweephole) Vegetated Filter Strip sf x 0.2 = Sand Filter If x 0.03 = Facility Sizing for Water Quality and Flow Control Overflow to Open Drainage Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area Rain Garden sf x 0.11 = Stormwater Planter If x 0.07 = Sand Filter If x 0.07 = Facility Sizinefor Water Quality Flow -Control and Flood Control"' Only for use in Tvne A&BSolis Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area Rain Garden sf x 0.13 = Stormwater Planter If x 0.11 = Sand Filter If x 0.11 = Sum of Total Impervious Area Managed 2079 Box4 Point of Discharge (check one) IBo%4 must be equal or greater than Sox 3) Over flow [o gu[terlweephole) Overflow to public storm drain pipe Overflow to Open Drainage X fa Subsurce Infiltration g 2014 SIM FORM: Tree Credit and Rainwater Harvesting Worksheet See "Tree credits" section for more information regarding the use of trees to most stormwater Impervious Area Reduction. New Evergreen Trees To receive Impervious Area Reduction Credit, new evergreen trees must be planted within 25 fear of the new or replaced impervious Surfaces. New trees cannot be credited against rooftop areas. Minimum tree height(at the time of plasmas) to receive credit is 6 feet Enter number of new evergreen trees that meet qualification requirements in Box A �Bo%A Multiply Box by 200 and enter result In Box B Bax B New Deciduous Trees To receive Impervious Area Reduction Credit, new large deciduous trees must be planted within 25 feet of the new or replaced impervious surfaces and new small deciduous trees must be pla and within 39 feet of new or replaced impervious surfaces. New trees cannot be credited against rooftop areas. Minimum tree caliper (at the time of planning) to receive credit is 2 inches. Enter number of new deciduous trees that meet qualification requirements in Box C H BoxC 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 canopies must be Within 25 feet and exerting small tree canop'ees must be within 10 feet of ground-level impervious surfaces (cannot be credit against rooftop surfacesl. Exist ng tree canopy credited towards Impervious Area Reduction must be preserved during and after construction throughout the life of the development. Minimum tree caliperto 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. Box E El Multiply Box E by 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 1 of Form SIM by 0.1 and enter the result! n Box H. Enter the lesser of Box G and H In Box I. (This Is the 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. S. 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. SOAKAGE TRENCH CALCULATIONS FOR 5524 B Street, Springfield, OR DRAINAGEAREA= AVERAGE RUNOFF COEFFICIENT (C) _ LENGTH OF DRYW ELL = WIDTH OF DRYW ELL = DEPTH OF DRYW ELL = VOID RATIO OF DRYWELL= AVERAGE PERMEABILITY OF SOIL = SURFACE AREA OF BOTTOM= SURFACE AREA OF SIDES - OUTFLOW CAPACITYOF DHYWELL- MAXIMUM STORAGE CAPACITY OF DPMELL ELL = DRYWELLVOLUME= 93.3 CUBIC YARDS 2,950 Si 0,90 10 FEET 36 FEET 7 FEET 31% 0.50 INCHES/HR 360 SO, FT, 644 SQ. FT. 0.068 ACRES Sea Infiltration Repod by: A1.1nad 15.0 CU, FT/HR= 1.87 GALLONS PER MINUTE 781.2 CU. FT. OF WATER ED PROP �� HGINEE Fss W OREGON jr F J•FA t2 .1Gi J J 9lC J. FAVPEP ' ewleery tLaYa 25YEAR TOTAL RECURRENCE RAINFALL TOTAL OUTFLOW DURATION DURATION RAINFALL DURING STORM EVENT FROM STORAGE OF STORM OFSTORM INTENSITY STORM RUNOFF DRYWELL REQUIRED DRYWELL IN MINUTES IN HOURS IN/HR INCHES CU FT. CLL FT. CU, FT, SIZING 5 0.08 3.45 0.29 64 1 62 OK 10 0.17 2.37 040 87 3 85 OK 15 0.25 1.90 0.48 105 4 101 OK 20 033 1,56 052 115 5 110 OK 30 0.50 1.36 068 150 8 143 OK 60 1.00 0.81 081 179 15 164 OK 120 2.00 0.56 1.12 248 30 218 OK 180 3.00 0.49 147 325 45 280 OK 240 4.00 0.44 1.76 389 60 329 OR 360 6.00 0.37 2.22 491 90 401 OK 480 6.00 0.34 212 602 120 482 OK 600 10.00 0.31 3.10 686 150 536 OK 720 12.00 028 336 743 180 563 OR 900 1500 0.25 3.75 330 225 605 OK 1,080 18.00 0.23 4.14 916 270 646 OK 1,260 21.00 0.22 4.62 1,022 315 707 OK 1,440 2400 0.21 504 1,115 360 755 OK ED PROP �� HGINEE Fss W OREGON jr F J•FA t2 .1Gi J J 9lC J. FAVPEP ' ewleery tLaYa TYPICAL SOAKAGE TRENCH DESIGN FOR CHAD WILSON PARTITION - PROPOSED DRIVEWAY 4" AC ON 12" CRUSHED ROCK 4" DIA. OPEN GRATEICLEANOUT CHANNEL SOAKAGE TRENCH SOAKAGE TRENCH DETAIL NO SCALE SOAKAGE TRENCH NOTES: 1. SOAKAGE TRENCH = 36'X 10'X TOR EQUIVALENT SQUARE FOOTAGE. SOAKAGE TRENCHES HAVE BEEN SIZED FOR THE 25 -YEAR STORM PER ATTACHED CALCULATIONS. 2. TOTAL IMPERVIOUS AREA DRAINED = 2,950 SQUARE FEET PER SOAKAGE TRENCH. 3. SEE THE CITY OF EUGENE STORMWATER MANAGEMENT MANUAL FOR ADDITIONAL INFORMATION. 4. FILTER FABRIC MUST BE ONE OF THE FOLLOWING TYPES/BRANDS: LINQ 125EX; LINO TYPAR3201; TNS E040; TNS R035; TNS R040; TNS R042; AMOCO 4535; MARAFI 140NL. 5. DRAINAGE ROCK SHALL BE A MINIMUM 2 112" TO 1 112" DRAIN ROCK. 6. THE PIPE WITHIN THE TRENCH SHALL EITHER BE PCV D2729 OR HDPE LEACH FIELD PIPE. 7. THE TRENCH BOTTOM IS TO BE INSTALLED LEVEL IN ALL DIRECTIONS. WILSON PARTITION T 4GE TRENCH DESIGN �;p PRpgFss/ Wu eta y � r r O s F � � 12,2 J FtC J. FA40 oo-w� Wada PER PLAN ZONES _ __ ZGNEA 20NEG PER PIAN TOP OF 31 SLOPE2. -OVERFLOW "\FALI[1TT OWY DETAILS PER PLAN TYPICAL FREEBOARC ELEVATION I IN \ m `PaiG — 12"TOPSOIL NATIVE SOIL e � III q' PIPE TO SCARAGE TRENCH _ PER PLAN FILTER FABRIC SURROUNDING ROCK LAYER 1 W SQUARE FEET IN ZGNEA THE RAIN GARDENS WILL BE FILLED WITH 12" OF TOPSOIL [TWAT MILO VEGETATION IN THE RAIN GAROEN5 SHALL BE PLANTED PER SCHEME I OF THE CITY OF EUGENE STORMWATER MANUAL SECTION 2.39. PLANTS TO BE T ON CENTER. ESTIMATED PLANT COUNT. ZONEA ZONE. CPRE%OBNUPTA 52-4 POTS CAMASSIA OUAMASH 26-6"POTS JUNCUSPATENS 4-q'POB DESCHAMPSIACAEBPITBY4 2Y 4 -POTS CHAD WILSON PARTITION (DRIVEWAY) INFILTRATION RAIN GARDEN DETAIL NO SCALE CHAD WILSON PARTITION (DRIVEWAY) INFILTRATION RAIN GARDEN DETAIL 5~��Ep PROAFLssi marn� Oy Lu y � r \ I aQ1 91C �. FRV P.�P EY9E8 v/aVa