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HomeMy WebLinkAboutNotes Applicant 10/24/2024 (6) Favreau EngineeringFavreau EngineeringFavreau EngineeringFavreau Engineering 2206 Country 2206 Country 2206 Country 2206 Country Haven DrHaven DrHaven DrHaven Dr Eugene, OR 97408Eugene, OR 97408Eugene, OR 97408Eugene, OR 97408 (541) 556(541) 556(541) 556(541) 556----4425442544254425 1 503 17th STREET, SPRINGFIELD STORMWATER NARRATIVE August 1, 2024 SITE CHARACTERISTICS The subject tax lot, identified as TL 17-03-36-24-03300, is currently a vacant lot. A single-family residence previously existed on the site prior to demolition. NRCS soil classification maps identify this site as having Class C and D soils. The site is generally flat with only a couple of trees on site. According to available records, there is an existing 12” storm mainline in 17th Street. INFILTRATION TESTING An infiltration test was performed on 7/31/2024. A single test pit was dug near the approximate location of the proposed stormwater facility. No groundwater was encountered. After testing, it was determined that the soil had an infiltration rate of 3”/hr. For sizing, an infiltration rate of 1.5”/hr will be used, applying a factor of safety of 2. FACILITY SIZING There are two proposed facilities with this development. A stormwater planter is proposed to treat the runoff generated from the driveway and parking area. This facility has been sized only for the water quality storm and utilized the SIM Form from the City of Eugene Stormwater Management Manual. For larger events, an overflow structure will direct runoff via pipe to a weephole in the curb in 17th St, where it will ultimately discharge into the public stormwater system. Additionally, an underground soakage trench has been designed to detain runoff from the roof of the proposed building, sized for the 10-year storm. An overflow is proposed to connect to the public stormwater mainline within 17th St for larger events. See the attached calculations and details for further information regarding facility construction. Favreau Engineering, LLC 2206 Country Haven Dr Eugene, OR 97408 (541) 556-4425 DRAINAGE AREA =3,035 SQ. FT. = 0.070 ACRES AVERAGE RUNOFF COEFFICIENT (C) = 0.90 LENGTH OF DRYWELL = 40 FEET WIDTH OF DRYWELL = 8 FEET DEPTH OF DRYWELL = 6 FEET VOID RATIO OF DRYWELL =35% AVERAGE PERMEABILITY OF SOIL = 1.50 INCHES/HR SURFACE AREA OF BOTTOM =320 SQ. FT. SURFACE AREA OF SIDES =576 SQ. FT. OUTFLOW CAPACITY OF DRYWELL = 40.0 CU. FT./HR = 4.99 GALLONS PER MINUTE MAXIMUM STORAGE CAPACITY OF DRYWELL = 672 CU. FT. OF WATER DRYWELL VOLUME = 71.1 CUBIC YARDS 10 YEAR TOTAL RECURRENCE RAINFALL TOTAL OUTFLOW DURATION DURATION RAINFALL DURING STORM EVENT FROM STORAGE OF STORM OF STORM INTENSITY STORM RUNOFF DRYWELL REQUIRED DRYWELL IN MINUTES IN HOURS IN/HR INCHES CU. FT. CU. FT. CU. FT. SIZING 5 0.08 3.10 0.26 59 3 55 OK 10 0.17 2.10 0.35 80 7 73 OK 15 0.25 1.65 0.41 94 10 84 OK 20 0.33 1.40 0.47 106 13 93 OK 30 0.50 1.10 0.55 125 20 105 OK 60 1.00 0.70 0.70 159 40 119 OK 120 2.00 0.50 1.00 228 80 148 OK 180 3.00 0.44 1.32 300 120 180 OK 240 4.00 0.41 1.64 373 160 213 OK 360 6.00 0.36 2.16 492 240 252 OK 480 8.00 0.32 2.56 583 320 263 OK 600 10.00 0.28 2.80 637 400 237 OK 720 12.00 0.25 3.00 683 480 203 OK 900 15.00 0.21 3.15 717 600 117 OK 1,080 18.00 0.20 3.60 819 720 99 OK 1,260 21.00 0.19 3.99 908 840 68 OK 1,440 24.00 0.18 4.32 983 960 23 OK 1,800 30.00 0.17 5.10 1,161 1,200 EMPTY OK SOAKAGE TRENCH CALCULATIONS FOR 503 17th St, Springfield - Roof Runoff See Infiltration Report by: Attached Page 1 of 1 SOAKAGE TRENCH NOTES: 1. SOAKAGE TRENCH = 40' x 8' x 6' OR EQUIVALENT SQUARE FOOTAGE. 2. TOTAL IMPERVIOUS AREA DRAINED = 3,035 SQUARE FEET. 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; LINQ TYPAR3201; TNS E040; TNS R035; TNS R040; TNS R042; AMOCO 4535; MARAFI 140NL OR APPROVED EQUAL. 5. DRAINAGE ROCK SHALL BE A MINIMUM 2 1/2" TO 1 1/2" DRAIN ROCK. 6. THE PIPE WITHIN THE TRENCH SHALL EITHER BE PVC D2729 OR HDPE LEACH FIELD PIPE. 7. THE TRENCH BOTTOM IS TO BE INSTALLED LEVEL IN ALL DIRECTIONS. 8. BAR RUN MATERIAL ENCOUNTERED AT APPROXIMATELY 7' DEEP. ENSURE THAT BOTTOM OF SOAKAGE TRENCH IS AT LEAST 1' INTO BAR RUN MATERIAL. 9. OVERFLOW TO CONNECT TO PUBLIC STORMWATER SYSTEM IN 17TH STREET. NO SCALE 503 17TH STREET, SPRINGFIELD SOAKAGE TRENCH DESIGN FOR DRAIN ROCK WRAPPED IN FILTER FABRIC, NOT BOTTOM NATIVE SOIL BACKFILL ORENCO CATCH BASIN MODEL SCB1236-6L 6" SOLID PIPE FINISH GRADE 6" SOLID PIPE6" PERFORATED PIPE LENGTH = 40' WIDTH = 8'6'2'4" DIA. OPEN GRATE/CLEANOUT OVERFLOW PER NOTE #9 6" SOLID PIPE DATE: 8/1/24 503 17TH STREET SOAKAGE TRENCH DETAIL FAVREAU ENGINEERING SCALE = N.T.S. E RIC J. F A V R E A US E P. 12 , 2 0 1 7OREGONREGISTERED PROFES S I ONALE N G I N EER TL: 17-03-36-24-03300 Stormwater Management Manual 4-33 Eugene 2014 4.5.14 Soakage Trench O & M Plan Soakage Trenches are infiltrating flood control devices. Soakage Trenches are linear excavations backfilled with sand and gravel injecting stormwater runoff into the ground recharging groundwater. There are various components within the system – inlet piping, aggregate storage basin and perforated piping. The trench surface may be covered with grating, stone, sand, or a grassed cover with a surface inlet and may also be installed under hard surfaces such as driveways. All facility components, vegetation, and source controls shall be inspected for proper operations and structural stability. These inspections shall occur, at a minimum, quarterly for the first two years from the date of installation, then two times per year afterwards, or within 48 hours after each major storm. Training and/or Written Guidance information for operating and maintaining Soakage Trenches shall be provided to all property owners and tenants. A copy of the O & M Plan shall be provided to all property owners and tenants. Inspection Logs shall be kept by the facility owner demonstrating the following items have been inspected and are being maintained properly: • Access to the Soakage Trench shall be safe and efficient. Obstacles preventing maintenance personnel and/or equipment access to the components of the facility shall be removed. • Algae Growth located on top of the soakage trench should be removed and disposed of properly. • Debris/Sediment that is found to clog the pipe shall be removed and disposed of in accordance with applicable federal and state requirements. • Failing Soakage Trenches shall be repaired and/or replaced if water is noticed on top of trench within 48 hours of a major storm. • Piping shall be cleared of sediment and debris to maintain conveyance. If piping is clear of sediment and debris and yet conveyance is poorly maintained, fabric around the pipe shall need replacing. • Shut-Off Valve or Flow-Blocking Mechanism may have been required with the construction of the drywell to temporarily prevent stormwater from flowing into it, in the event of an accidental toxic material spill. This may also involve mats kept on-site that can be used to cover inlet drains in parking lots. The shut-off valve shall remain in good working order, or if mats or other flow-blocking mechanisms are used, they shall be kept in stock on-site. • Sediment in the aggregate obstructing storage and infiltration shall be excavated and replaced. • Vegetation such as trees should not be located in or around the soakage trench because roots from trees can penetrate the unit body, and leaves from deciduous Stormwater Management Manual 4-34 Eugene 2014 trees and shrubs can increase the risk of clogging the intake pipe. Large shrubs or trees that are likely to interfere with operation will be identified at each inspection and removed. Spill Prevention Measures shall be exercised on site when handling substances that contaminate stormwater. Releases of pollutants shall be corrected as soon as identified. Non-Chemical Pest Control measures shall be taken to prevent development of insects, mosquitoes, and rodents. Stormwater Management Manual 4-23 Eugene 2014 4.5.9 Stormwater Planter O & M Plan Stormwater Planters are infiltration and filtration stormwater facilities that can provide flood control, flow control and stormwater quality benefits. Stormwater Planters are walled vegetated surface reservoirs used to collect and treat stormwater runoff from impervious surfaces by allowing pollutants to settle and filter out as the water percolates through the vegetation and soil mediums before infiltrating into the ground below or being piped to its downstream destination. Stormwater Planters can be used to help fulfill a site’s required landscaping area requirement and should be integrated into the overall site design. Numerous design variations of shape and planting scheme can be used to fit the character. All facility components and vegetation shall be inspected for proper operations and structural stability. These inspections shall occur, at a minimum, quarterly for the first 2 years from the date of installation, 2 times per year thereafter, and within 48 hours after each major storm event. Training and/or Written Guidance information for operating and maintaining Stormwater Planters shall be provided to all property owners and tenants. A copy of the O & M Plan shall be provided to all property owners and tenants. Inspection Logs shall be kept by the facility owner demonstrating the following items have been inspected and are being maintained properly: • Access to Stormwater Planters shall be safe and efficient. Obstacles preventing maintenance personnel and/or equipment access to the components of the facility shall be removed. • Debris and Litter shall be removed to prevent channelization, clogging, and interference with plant growth. Fallen leaves and debris from deciduous plant foliage shall be raked and removed. • Erosion Damage shall be identified and controlled when native soil is exposed or erosion channels are forming. • Filter Media consisting of sand and/or topsoil shall be tested to ensure stormwater percolates through the planter. Remove and replace sand and/or topsoil to correct percolation deficiencies. • Infiltrating Stormwater Planters shall be excavated and cleaned, and gravel or soil shall be replaced to correct low infiltration rates. Water should drain through the planter within 3-4 hours after a storm event. • Inlets shall be cleared when conveyance capacity is plugged to ensure unrestricted stormwater flow to the rain garden. • Mulch shall be replenished as needed to ensure healthy plant growth. • Nuisance and Prohibited Vegetation from the Eugene Plant List (such as blackberries and English Ivy) shall be removed when discovered. Invasive Stormwater Management Manual 4-24 Eugene 2014 vegetation contributing up to 25% of vegetation of all species shall be removed and replaced. • Outlets shall be cleared when 50% of the conveyance capacity is plugged. • Piping shall be cleared of sediment and debris to maintain conveyance capacity. • Planter Walls shall be examined for deficiencies, such as rot, cracks, and failure, and repaired as needed. Holes that are not consistent with the design and allow water to flow directly through the planter to the ground shall be plugged. • Sedimentation build-up near or exceeding 2” in depth shall be hand-removed with minimum damage to vegetation using proper erosion control measures. Sediment shall be removed if it is more than 4 inches thick or so thick as to damage or kill vegetation. • Vegetation shall be healthy and dense enough to provide filtering while protecting underlying soils from erosion. Dead vegetation shall be removed to maintain less than 10% of area coverage or when vegetative filter function is impaired. Vegetation shall be replaced immediately to control erosion where soils are exposed and within 3 months to maintain cover density. Spill Prevention Measures shall be exercised on site when handling substances that contaminate stormwater. Releases of pollutants shall be corrected as soon as identified. Non-Chemical Pest Control measures shall be taken to prevent development of insects, mosquitoes, and rodents. OVERFLOW GROWING DRAIN ROCK DOWNSPOUTOVERFLOW (SEE NOTE #6) SUB-GRADE OR EXISTING SOIL PER PLAN INFILTRATION STORMWATER PLANTER DETAIL NO SCALE 503 17TH STREET FILTER FABRIC SURROUNDING ROCK LAYER OVERFLOW ZONE A ESTIMATED PLANT COUNT: CAREX OBNUPTA 71 - 4" POTS JUNCUS PATENS 71 - 4" POTS STORMWATER PLANTER NOTES: 1. SQUARE FOOTAGE OF FACILITY = 142 SQUARE FEET MINIMUM. 2. TOTAL IMPERVIOUS AREA DRAINED = 4,745 SQUARE FEET. 3. THE FILTRATION PLANTER WILL BE FILLED WITH 12" OF TOPSOIL (3-WAY MIX). VEGETATION IN THE PLANTER SHALL BE PLANTED PER SCHEME I OF THE CITY OF EUGENE STORMWATER MANUAL SECTION 2.3.9. PLANTS TO BE 1' ON CENTER. 4. SEE THE CITY OF EUGENE STORMWATER MANAGEMENT MANUAL FOR ADDITIONAL INFORMATION. 5. FILTER FABRIC MUST BE ONE OF THE FOLLOWING TYPES/BRANDS: LINQ 125EX; LINQ TYPAR3201; TNS E040; TNS R035; TNS R040; TNS R042; AMOCO 4535; MARAFI 140NL. 6. OVERFLOW SHOULD BE PIPED TO A WEEPHOLE IN THE CURB ALONG 17TH ST. 7. WHERE THE FILTRATION PLANTER IS WITHIN 10' OF THE BUILDING FOUNDATION OR 5' OF THE PROPERTY LINE, A 30 MIL PVC (OR EQUIVALENT) WATERPROOF LINER SHALL BE INSTALLED ALONG SIDES AND BOTTOM OF FACILITY. 8. IN NO CASE SHALL ANY PART OF THE FACILITY BE LOCATED WITHIN 7' OF BUILDING FOUNDATION OR 1' OF PROPERTY LINE. 9. SEE STD DWGS RD700(D) AND (H) FOR FURTHER DETAILS REGARDING WALL CONSTRUCTION ELEVATION 1'MEDIUM 1'2:1 M A X 6" ROCK BENCH (TYP) 2" MIN FREEBOARD ROCK SPLASH PAD SOLID PIPE POND LINER, 30 MIL PVC OR EQUIVALENT WHEN WITHIN 5' OF PROPERTY LINE OR 10' OF BLDG PLANTER CURB PER RD700(H) (TYP) DATE: 8/1/24503 17TH STREET INFILTRATION STORMWATER PLANTER DETAIL FAVREAU ENGINEERING SCALE = N.T.S. E RIC J. F A V R E A US E P. 12 , 2 0 1 7OREGONREGISTERED PROFES S I ONALE N G I N EER TL: 17-03-36-24-03300 SIM FORM: 2014 (Simplified Approach for Stormwater Management) Application Building Permit #  Address Residential/Commercial Tax Lot #(Circle One) NRCS Soil Type or Measured Infiltraiton Rate Facility Sizing 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 (Box 1 ‐ Box 2) Facility Sizing for Water Quality Only Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area Rain Garden sf         x0.05 = Stormwater Planter sf         x0.03 = Swale sf         x0.06 = Vegetated Filter Strip sf         x0.2 = Sand Filter sf         x0.03 = Facility Sizing for Water Quality and Flow Control Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area Rain Garden sf         x0.11 = Stormwater Planter sf         x0.07 = Sand Filter sf         x0.07 = Facility Sizing 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         x0.13 = Stormwater Planter sf         x0.11 = Sand Filter sf         x0.11 = Sum of Total  Impervious Area Managed Box 4 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 503 17th St Springfield, OR 97477 17-03-36-24-03300 3"/hr 4,745 0 4,745 4,745 142 4,745 x 503 17th St 2014 SIM FORM: Tree Credit and Rainwater Harvesting Worksheet See "Tree Credits" section for more information regarding the use of trees to 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 new or replaced impervious surfaces.  New trees cannot be credited against rooftop areas.  Minimum tree height (at the time of planting)to receive credit is 6 feet Enter number of new evergreen trees that meet qualification requirements in Box ABox 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 new or replaced impervious surfaces and new small deciduous trees must be plantd 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 CBox 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 canopies must be within 25 feet and existing small tree canopies must be within 10 feet of ground‐level impervious surfaces (cannot be credit against roof top surfaces).  Existing tree canopy credited towards Impervious Area Reduction must be preserved during and after construction throughout the life of the development. Minimum tree caliper to 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 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 in Box H. 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.)Box I 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.