Land Use Planning Division
1600 SE 190th Ave, Ste 116
Portland OR 97233
Ph: 503-988-3043 Fax: 503-988-3389
multco.us/landuse
Advanced BMP Documentation Form
*
1). Sediment Fence
Install along contours at base of grading and stockpiled soil. Series of fences needed on slopes between 20%
and 50% grade, or to reduce drainage area for each fence. Shall not be installed across streams or ditches.
Bottom flap of fence must be buried w/ 6-inches of backfill.
Check Appropriate Design






Avg. Slope of Construction Area
(Small projects on slopes <10% may
substitute sediment fence with grassy
buffer strip preservation)
1% - 10%
10% - 15%
15% - 20%
20% - 30%
30% - 50%
Suggested Spacing Between Fences
When Used To Break Up Slope Length
or Disturbance Area
(see footnote**)
300 feet
150 feet
100 feet
25 feet (Required for slopes >20%)
20 feet (Required for slopes >20%)
Not Appropriate
Greater than 50%
(Erosion Blanket Required)
**Min. 100 linear feet of fence per 10,000 square feet disturbed
2). Erosion Blankets
Required on slopes >50% grade. Optional on shallower slopes and in swales/ditches. Erosion Control
blankets are mats of organic fibers or inorganic materials held together by netting. Typically used on steep
slopes or in areas of concentrated water flow to stabilize area and to enhance success of planting and grass
seed applications. Must be anchored to slope with erosion blanket staples to minimize undermining.
Slope of Disturbed Area
(H:V)
Concentrated flow
on matting shall not
exceed

3:1 (33%) or less
8 feet/per/second


3:1 (33%) – 2:1 (50%)
2:1 (50%) – 1:1 (100%)
> 2:1 – 50% (higher
flows)
> 2:1 – 50% (higher
flows)
*Straw placed 2-inches thick
8 feet/per/second
8 feet/per/second
Straw*, Jute,
Excelsior
Jute, Excelsior
Jute
10 feet/per/second
Coir fabric
20 feet/per/second
TRM
(3-d synthetic fibers)
Check Appropriate Design


Appropriate
Material
* These are minimal BMP requirements and are subject to amendment to assure adequate site
protection.
GEC-BMP Documentation Form
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3). Bio-Bag Check Dams in Ditches and Swales
Appropriate for all on-site ditches/swales receiving project related runoff or work within ditches/swales.
Commonly required in ditches along road projects. Bags are plastic mesh filled with various organic
materials. Bark chips is the most common filler. Designed to slow flow velocity and deposit suspended
sediment. Can be placed at base of sediment fence for extra protection.
Check Appropriate Design
Ditch
Pitch
Check Dam Spacing
(feet)
Design Specifications
Place (2) 1” x 2” wood stakes per bag
downhill of bag to anchor during flows.
5%
30
See above.

4%
40
See above.

3%
50
See above.

2%
80
See above.

*Ditches pitching more than 6% require more substantial check dam design such as 4-6-inch gabion rock
placed to top of ditch at edges and 6-inches below top of ditch at middle to allow spill-over. Spacing of
rock dams should be so that bottom of uphill dam matches height of downhill dam top.

6 %*
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4). Interceptor Soil Dike*
Optional BMP to minimize runoff volume entering a construction site by routing runoff around the work area.
Dike should not re-direct runoff across property line. BMP’s should be installed at dike outlet. Earthen dike
should be mechanically compacted to at least 95% Standard Proctor Compaction (ASTM D698).
Slopes
above
Dike Spacing if
Dike
Dike Width
Check Appropriate Design
proposed
used in series
Height
(at base)
dike
location
1% - 5%
300 feet
1.5 feet
2 feet

200 feet
1.5 feet
2 feet
 5% - 10%
100 feet
1.5 feet
2 feet
 10% - 40%
*Concentrated flow existing dike system must be mitigated with appropriate BMP’s.
Dike
Sidewalls
2:1 (H:V)
2:1 (H:V)
2:1 (H:V)
5). Interceptor Swale
Optional BMP to minimize surface runoff volume entering a construction site by routing runoff around the
work area. Swale should not re-direct runoff across property line. Swale pitch exceeding 5 percent is not an
appropriate design. BMP’s should be installed at swale outlet.
Check Appropriate Design




Slopes
above
proposed
swale
location
1% - 5%
5% - 10%
10% - 25%
25% - 50%
GEC-BMP Documentation Form
Swale Spacing if
used in series
Swale
Depth
Swale Width
(measured at
grade)
Swale
Sidewalls
300 feet
200 feet
100 feet
50 feet
1 feet
1 feet
1 feet
1 feet
2 feet
2 feet
2 feet
2 feet
2:1 (H:V)
2:1 (H:V)
2:1 (H:V)
2:1 (H:V)
2
SEDIMENT FENCE
STOCKPILE COVERING
GEC-BMP Documentation Form
3