HomeMy WebLinkAboutNotes Applicant 12/13/2024 (5) Favreau Engineering
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
1
SYCAN BSYCAN BSYCAN BSYCAN B SUBDIVISIONSUBDIVISIONSUBDIVISIONSUBDIVISION
STORMWATER NARRATIVESTORMWATER NARRATIVESTORMWATER NARRATIVESTORMWATER NARRATIVE
November 15, 2024
PRE-DEVELOPMENT SITE CHARACTERISTICS
The subject property is a 2.33-acre lot west of Game Farm Rd, north of Pheasant Blvd; more specifically identified
as TL 17-03-22-13-20801. The site is currently vacant and is generally flat. The nearest stormwater system is
located on the east side of Game Farm Rd, but is not sized for to accommodate runoff from this development.
Therefore, the stormwater facilities will be sized for the flood control event with emergency overflows to the
existing stormwater system on the east side of Game Farm Rd. NRCS soil classification maps identify this site as
having Class C soils. Infiltration testing was performed on 3/8/24. Four test pits were dug throughout the site and
it was determined that on-site soils have an average infiltration rate of 12 inches per hour. For design purposes,
an infiltration rate of 6 inches per hour will be used, applying a factor of safety of 2.
POST-DEVELOPMENT SITE CHARACTERISTICS + FACILITY SIZING
The development proposal is for a 10-lot residential subdivision with a private street. The site will be graded and
piped to direct site runoff into curbside stormwater planters where it will be treated prior to discharging into
underground soakage trenches located underneath the private driveway. The soakage trenches will be sized for
the 25-year event for all impervious runoff created by the development (roadways and buildings). Please refer to
sheets HYD-1 and HYD-2 for basin boundary determinations.
Water Quality Facilities
The proposed stormwater treatment planters have been sized to accommodate the runoff from the private
roadway and parking areas for the Water Quality event only. Runoff will be directed into these facilities where it
will be treated and be piped into an underground soakage trench that has been sized to accommodate the
runoff for all proposed impervious area for the 25-year event. Since all basins are proposed to be under 15,000
SF, the City of Eugene’s SIM form was utilized to size each water quality facility (see attached). The table below
shows a summary of each basin’s proposed impervious surface and required facility size:
BASIN
IMPERVIOUS
AREA (SF)
MIN FACILITY
SIZE (SF)
RD-1 3,100 93
RD-2 5,050 152
RD-3 9,000 270
RD-4 9,000 270
RD-5 9,200 276
RD-6 8,000 240
RD-7 6,900 207
RD-8 4,700 141
Favreau Engineering
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
2
Flood Control Facilities
As mentioned above, soakage trenches will be constructed under the proposed private roadway that have been
sized to accommodate all impervious surface runoff generated by the development. Roadway runoff will be pre-
treated through stormwater planters (see above) and then overflow into the soakage trench. Runoff from
buildings will be piped directly into the soakage trenches. Soakage trenches were sized using the Rational
Method, and are summarized below. Refer to civil plan set for further details on facility sizing and construction.
BASINS IMPERVIOUS
AREA (SF)
MIN DEPTH
(FT)
MIN WIDTH
(FT)
MIN LENGTH
(FT)
MIN AREA
(SF)
RD-1 3,100
SOAKAGE TRENCH 1 3,100 7 10 11 110
RD-2 5,000
BLD-1 2,100
SOAKAGE TRENCH 2 7,100 7 10 25 250
RD-3 9,150
BLD-2 2,300
BLD-3 2,300
SOAKAGE TRENCH 3 13,750 7 10 50 500
RD-4 9,000
BLD-4 2,300
BLD-5 2,300
SOAKAGE TRENCH 4 13,600 7 10 50 500
RD-5 9,200
BLD-6 2,300
BLD-7 2,300
SOAKAGE TRENCH 5 13,800 7 10 50 500
RD-6 8,000
BLD-8 2,500
SOAKAGE TRENCH 6 10,500 7 10 40 400
RD-7 6,900
BLD-9 2,300
BLD-10 3,000
SOAKAGE TRENCH 7 12,200 7 10 45 450
RD-8 4,700
SOAKAGE TRENCH 8 4,700 7 10 17 170
Favreau Engineering
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
3
ATTACHED DOCUMENTS
1. Stormwater Planter SIM Forms
2. Soakage Trench Calculations
3. Stormwater Planter Operations and Maintenance Form
4. Soakage Trench Operations and Maintenance Form
SIM FORM: 2014 (Simplified Approach for Stormwater Management)
Application Sycan B Subdivision - Basin RD-1 Building Permit # N/A
Address N/A
Residential/Commercial
Tax Lot # 17-03-22-13-02100 & 20801 (Circle One)
NRCS Soil Type or
Measured Infiltraiton Rate 6"/hr (measured 12"/hr)
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 0 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 x 0.05 = 0
Stormwater Planter 3100 sf x 0.03 = 93
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
3100
0
3100
3100
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 0 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 x 0.05 = 0
Stormwater Planter 5000 sf x 0.03 = 150
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
Sycan B Subdivision - Basin RD-2
N/A
17-03-22-13-02100 & 20801
6"/hr (measured 12"/hr)
N/A
5000
0
5000
5000
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 0 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 x 0.05 = 0
Stormwater Planter 9150 sf x 0.03 = 274.5
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
9150
0
9150
9150
Sycan B Subdivision - Basin RD-3 N/A
N/A
17-03-22-13-02100 & 20801
6"/hr (measured 12"/hr)
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 0 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 x 0.05 = 0
Stormwater Planter 9000 sf x 0.03 = 270
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
9000
0
9000
9000
Sycan B Subdivision - Basin RD-4 N/A
N/A
17-03-22-13-02100 & 20801
6"/hr (measured 12"/hr)
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 0 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 x 0.05 = 0
Stormwater Planter 9200 sf x 0.03 = 276
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
9200
0
9200
9200
Sycan B Subdivision - Basin RD-5 N/A
N/A
17-03-22-13-02100 & 20801
6"/hr (measured 12"/hr)
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 0 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 x 0.05 = 0
Stormwater Planter 8000 sf x 0.03 = 240
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
8000
0
8000
8000
Sycan B Subdivision - Basin RD-6 N/A
N/A
17-03-22-13-02100 & 20801
6"/hr (measured 12"/hr)
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 0 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 x 0.05 = 0
Stormwater Planter 6900 sf x 0.03 = 207
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
6900
0
6900
6900
Sycan B Subdivision - Basin RD-7 N/A
N/A
17-03-22-13-02100 & 20801
6"/hr (measured 12"/hr)
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 0 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 x 0.05 = 0
Stormwater Planter 4700 sf x 0.03 = 141
Swale sf x 0.06 = 0
Vegetated Filter Strip sf x 0.2 = 0
Sand Filter sf x 0.03 = 0
Facility Sizing for Water Quality and Flow Control
Surface Facilities Impervious Area Managed Sizing Factor Faclity Surface Area
Rain Garden sf x 0.11 = 0
Stormwater Planter sf x 0.07 = 0
Sand Filter sf x 0.07 = 0
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 x 0.13 = 0
Stormwater Planter sf x 0.11 = 0
Sand Filter sf x 0.11 = 0
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
4700
0
4700
4700
Sycan B Subdivision - Basin RD-8 N/A
N/A
17-03-22-13-02100 & 20801
6"/hr (measured 12"/hr)
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 1
BASINS:RD-1
DRAINAGE AREA =3,100 SQ. FT. = 0.071 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 11 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =110 SQ. FT.
SURFACE AREA OF SIDES =294 SQ. FT.
OUTFLOW CAPACITY OF DRYWELL = 55.0 CU. FT./HR = 6.86 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 231 CU. FT. OF WATER
DRYWELL VOLUME = 28.5 CUBIC YARDS
25 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 3.45 0.29 67 5 62 OK
10 0.17 2.37 0.40 92 9 83 OK
15 0.25 1.90 0.48 110 14 97 OK
20 0.33 1.56 0.52 121 18 103 OK
30 0.50 1.36 0.68 158 28 131 OK
60 1.00 0.81 0.81 188 55 133 OK
120 2.00 0.56 1.12 260 110 150 OK
180 3.00 0.49 1.47 342 165 177 OK
240 4.00 0.44 1.76 409 220 189 OK
360 6.00 0.37 2.22 516 330 186 OK
480 8.00 0.34 2.72 632 440 192 OK
600 10.00 0.31 3.10 721 550 171 OK
720 12.00 0.28 3.36 781 660 121 OK
900 15.00 0.25 3.75 872 825 47 OK
1,080 18.00 0.23 4.14 963 990 EMPTY OK
1,260 21.00 0.22 4.62 1,074 1,155 EMPTY OK
1,440 24.00 0.21 5.04 1,172 1,320 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 1 of 8
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 2
BASINS:RD-2 & BLD-1
DRAINAGE AREA =7,100 SQ. FT. = 0.163 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 25 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =250 SQ. FT.
SURFACE AREA OF SIDES =490 SQ. FT.
OUTFLOW CAPACITY OF DRYWELL = 125.0 CU. FT./HR = 15.58 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 525 CU. FT. OF WATER
DRYWELL VOLUME = 64.8 CUBIC YARDS
25 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 3.45 0.29 153 10 143 OK
10 0.17 2.37 0.40 210 21 190 OK
15 0.25 1.90 0.48 253 31 222 OK
20 0.33 1.56 0.52 277 42 235 OK
30 0.50 1.36 0.68 362 63 300 OK
60 1.00 0.81 0.81 431 125 306 OK
120 2.00 0.56 1.12 596 250 346 OK
180 3.00 0.49 1.47 783 375 408 OK
240 4.00 0.44 1.76 937 500 437 OK
360 6.00 0.37 2.22 1,182 750 432 OK
480 8.00 0.34 2.72 1,448 1,000 448 OK
600 10.00 0.31 3.10 1,651 1,250 401 OK
720 12.00 0.28 3.36 1,789 1,500 289 OK
900 15.00 0.25 3.75 1,997 1,875 122 OK
1,080 18.00 0.23 4.14 2,205 2,250 EMPTY OK
1,260 21.00 0.22 4.62 2,460 2,625 EMPTY OK
1,440 24.00 0.21 5.04 2,684 3,000 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 2 of 8
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 3
BASINS:RD-3, BLD-2, & BLD-3
DRAINAGE AREA =13,750 SQ. FT. = 0.316 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 50 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =500 SQ. FT.
SURFACE AREA OF SIDES =840 SQ. FT.
OUTFLOW CAPACITY OF DRYWELL = 250.0 CU. FT./HR = 31.17 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 1050 CU. FT. OF WATER
DRYWELL VOLUME = 129.6 CUBIC YARDS
25 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 3.45 0.29 296 21 276 OK
10 0.17 2.37 0.40 407 42 366 OK
15 0.25 1.90 0.48 490 63 427 OK
20 0.33 1.56 0.52 536 83 453 OK
30 0.50 1.36 0.68 701 125 576 OK
60 1.00 0.81 0.81 835 250 585 OK
120 2.00 0.56 1.12 1,155 500 655 OK
180 3.00 0.49 1.47 1,516 750 766 OK
240 4.00 0.44 1.76 1,815 1,000 815 OK
360 6.00 0.37 2.22 2,289 1,500 789 OK
480 8.00 0.34 2.72 2,805 2,000 805 OK
600 10.00 0.31 3.10 3,197 2,500 697 OK
720 12.00 0.28 3.36 3,465 3,000 465 OK
900 15.00 0.25 3.75 3,867 3,750 117 OK
1,080 18.00 0.23 4.14 4,269 4,500 EMPTY OK
1,260 21.00 0.22 4.62 4,764 5,250 EMPTY OK
1,440 24.00 0.21 5.04 5,198 6,000 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 3 of 8
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 4
BASINS:RD-4, BLD-4, & BLD-5
DRAINAGE AREA =13,600 SQ. FT. = 0.312 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 50 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =500 SQ. FT.
SURFACE AREA OF SIDES =840 SQ. FT.
OUTFLOW CAPACITY OF DRYWELL = 250.0 CU. FT./HR = 31.17 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 1050 CU. FT. OF WATER
DRYWELL VOLUME = 129.6 CUBIC YARDS
25 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 3.45 0.29 293 21 272 OK
10 0.17 2.37 0.40 403 42 361 OK
15 0.25 1.90 0.48 485 63 422 OK
20 0.33 1.56 0.52 530 83 447 OK
30 0.50 1.36 0.68 694 125 569 OK
60 1.00 0.81 0.81 826 250 576 OK
120 2.00 0.56 1.12 1,142 500 642 OK
180 3.00 0.49 1.47 1,499 750 749 OK
240 4.00 0.44 1.76 1,795 1,000 795 OK
360 6.00 0.37 2.22 2,264 1,500 764 OK
480 8.00 0.34 2.72 2,774 2,000 774 OK
600 10.00 0.31 3.10 3,162 2,500 662 OK
720 12.00 0.28 3.36 3,427 3,000 427 OK
900 15.00 0.25 3.75 3,825 3,750 75 OK
1,080 18.00 0.23 4.14 4,223 4,500 EMPTY OK
1,260 21.00 0.22 4.62 4,712 5,250 EMPTY OK
1,440 24.00 0.21 5.04 5,141 6,000 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 4 of 8
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 5
BASINS:RD-5, BLD-6, & BLD-7
DRAINAGE AREA =13,800 SQ. FT. = 0.317 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 50 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =500 SQ. FT.
SURFACE AREA OF SIDES =840 SQ. FT.
OUTFLOW CAPACITY OF DRYWELL = 250.0 CU. FT./HR = 31.17 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 1050 CU. FT. OF WATER
DRYWELL VOLUME = 129.6 CUBIC YARDS
25 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 3.45 0.29 298 21 277 OK
10 0.17 2.37 0.40 409 42 367 OK
15 0.25 1.90 0.48 492 63 429 OK
20 0.33 1.56 0.52 538 83 455 OK
30 0.50 1.36 0.68 704 125 579 OK
60 1.00 0.81 0.81 838 250 588 OK
120 2.00 0.56 1.12 1,159 500 659 OK
180 3.00 0.49 1.47 1,521 750 771 OK
240 4.00 0.44 1.76 1,822 1,000 822 OK
360 6.00 0.37 2.22 2,298 1,500 798 OK
480 8.00 0.34 2.72 2,815 2,000 815 OK
600 10.00 0.31 3.10 3,209 2,500 709 OK
720 12.00 0.28 3.36 3,478 3,000 478 OK
900 15.00 0.25 3.75 3,881 3,750 131 OK
1,080 18.00 0.23 4.14 4,285 4,500 EMPTY OK
1,260 21.00 0.22 4.62 4,782 5,250 EMPTY OK
1,440 24.00 0.21 5.04 5,216 6,000 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 5 of 8
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 6
BASINS:RD-6 & BLD-8
DRAINAGE AREA =10,500 SQ. FT. = 0.241 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 40 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =400 SQ. FT.
SURFACE AREA OF SIDES =700 SQ. FT.
OUTFLOW CAPACITY OF DRYWELL = 200.0 CU. FT./HR = 24.93 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 840 CU. FT. OF WATER
DRYWELL VOLUME = 103.7 CUBIC YARDS
25 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 3.45 0.29 226 17 210 OK
10 0.17 2.37 0.40 311 33 278 OK
15 0.25 1.90 0.48 374 50 324 OK
20 0.33 1.56 0.52 410 67 343 OK
30 0.50 1.36 0.68 536 100 436 OK
60 1.00 0.81 0.81 638 200 438 OK
120 2.00 0.56 1.12 882 400 482 OK
180 3.00 0.49 1.47 1,158 600 558 OK
240 4.00 0.44 1.76 1,386 800 586 OK
360 6.00 0.37 2.22 1,748 1,200 548 OK
480 8.00 0.34 2.72 2,142 1,600 542 OK
600 10.00 0.31 3.10 2,441 2,000 441 OK
720 12.00 0.28 3.36 2,646 2,400 246 OK
900 15.00 0.25 3.75 2,953 3,000 EMPTY OK
1,080 18.00 0.23 4.14 3,260 3,600 EMPTY OK
1,260 21.00 0.22 4.62 3,638 4,200 EMPTY OK
1,440 24.00 0.21 5.04 3,969 4,800 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 6 of 8
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 7
BASINS:RD-7, BLD-9 & BLD-10
DRAINAGE AREA =12,200 SQ. FT. = 0.280 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 45 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =450 SQ. FT.
SURFACE AREA OF SIDES =770 SQ. FT.
OUTFLOW CAPACITY OF DRYWELL = 225.0 CU. FT./HR = 28.05 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 945 CU. FT. OF WATER
DRYWELL VOLUME = 116.7 CUBIC YARDS
25 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 3.45 0.29 263 19 244 OK
10 0.17 2.37 0.40 361 38 324 OK
15 0.25 1.90 0.48 435 56 378 OK
20 0.33 1.56 0.52 476 75 401 OK
30 0.50 1.36 0.68 622 113 510 OK
60 1.00 0.81 0.81 741 225 516 OK
120 2.00 0.56 1.12 1,025 450 575 OK
180 3.00 0.49 1.47 1,345 675 670 OK
240 4.00 0.44 1.76 1,610 900 710 OK
360 6.00 0.37 2.22 2,031 1,350 681 OK
480 8.00 0.34 2.72 2,489 1,800 689 OK
600 10.00 0.31 3.10 2,837 2,250 587 OK
720 12.00 0.28 3.36 3,074 2,700 374 OK
900 15.00 0.25 3.75 3,431 3,375 56 OK
1,080 18.00 0.23 4.14 3,788 4,050 EMPTY OK
1,260 21.00 0.22 4.62 4,227 4,725 EMPTY OK
1,440 24.00 0.21 5.04 4,612 5,400 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 7 of 8
Favreau Engineering, LLC
2206 Country Haven Dr
Eugene, OR 97408
(541) 556-4425
SOAKAGE TRENCH 8
BASINS:RD-8
DRAINAGE AREA =4,700 SQ. FT. = 0.108 ACRES
AVERAGE RUNOFF COEFFICIENT (C) = 0.90
LENGTH OF DRYWELL = 17 FEET
WIDTH OF DRYWELL = 10 FEET
DEPTH OF DRYWELL = 7 FEET
VOID RATIO OF DRYWELL =30%
AVERAGE PERMEABILITY OF SOIL = 6.00 INCHES/HR
SURFACE AREA OF BOTTOM =170 SQ. FT.
SURFACE AREA OF SIDES =378
OUTFLOW CAPACITY OF DRYWELL = 85.0 CU. FT./HR = 10.60 GALLONS PER MINUTE
MAXIMUM STORAGE CAPACITY OF DRYWELL = 357 CU. FT. OF WATER
DRYWELL VOLUME = 44.1 CUBIC YARDS
25 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 3.45 0.29 101 7 94 OK
10 0.17 2.37 0.40 139 14 125 OK
15 0.25 1.90 0.48 167 21 146 OK
20 0.33 1.56 0.52 183 28 155 OK
30 0.50 1.36 0.68 240 43 197 OK
60 1.00 0.81 0.81 286 85 201 OK
120 2.00 0.56 1.12 395 170 225 OK
180 3.00 0.49 1.47 518 255 263 OK
240 4.00 0.44 1.76 620 340 280 OK
360 6.00 0.37 2.22 783 510 273 OK
480 8.00 0.34 2.72 959 680 279 OK
600 10.00 0.31 3.10 1,093 850 243 OK
720 12.00 0.28 3.36 1,184 1,020 164 OK
900 15.00 0.25 3.75 1,322 1,275 47 OK
1,080 18.00 0.23 4.14 1,459 1,530 EMPTY OK
1,260 21.00 0.22 4.62 1,629 1,785 EMPTY OK
1,440 24.00 0.21 5.04 1,777 2,040 EMPTY OK
SOAKAGE TRENCH CALCULATIONS FOR
SYCAN B SUBDIVISION, SPRINGFIELD
See Infiltration Report by:
Attached
Page 8 of 8
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.
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.