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Water and Sediment Control Basin (WASCoB) Design Information Sheet
(Multiple WASCoB System)

Author: Robert P. Stone, P. Eng.- Engineer, Soil/OMAFRA
Creation Date: 13 June 2007
Last Reviewed: 3 April 2008

Note: Use this Design Information Sheet for each WASCoB if more than one WASCoB is to be constructed and drained through a single subsurface tile outlet. Start at uppermost WASCoB.

WASCoB Number ________ of ________

  1. Watershed area
________ ha
________ ac
  1. Watershed slope
________ %
  1. Runoff curve number from Tables 2.2 to 2.4
__________
  1. Peak flow from watershed for 10 year storm from
    Table 4.25-M to 4.31-M (4.25-I to 4.31-I)
________m3/s
________ft3/s
  1. Peak flow from watershed for 25 year storm from
    Table 4.25-M to 4.31-M (4.25-I to 4.31-I)
________m3/s
________ft3/s
  1. Obtain the storm duration for a 10 year storm from
    Table 4.25-M to 4.31-M (4.25-I to 4.31-I)

________ hours
  1. Obtain the storm volume expected for a 10 year storm from Table 4.25-M to 4.31-M (4.25-I to 4.31-I)
________m3
________ft3
  1. Determine slope of ponding area upstream from storage berm from field measurements
________ %
  1. Determine slope of side of ponding area upstream from storage berm from field measurements. If side slopes are different use the average of the two slopes.
________ %
  1. Determine soil loss expected above ponding area from Table 4.32-M (4.32-I)
________
tonnes/ ha/yr
________
tons/ ac/yr
  1. Storage required for eroded soil for 15 year life expectancy
    Line (10) x Line (1) x 15
    = ________ x ________ x 15
    = ________ tonnes x 0.68 m3/tonne
    = ________m3
    (________ x ________ x 15
    = ________ tons x 21.7 ft3/ton = ________ ft3)
________m3
________ft3
  1. Total pond storage
    Line (7) + Line (11)
    = ________ + ________
    = ________ m3 (________ ft3)
________m3
________ft3
  1. Determine volume factor
    Line (12) x Line (8) x Line (9)
    = ________ x ________ x ________
    = ________m3 (________ ft3)
________m3
________ft3
  1. Obtain pond depth (design berm height) from
    Table 4.33-M (4.33-I)
________m
________ft
  1. Determine pond length
    (Line (14) ÷ Line (8)) x 100 = ________ m (________ft)
________m
________ft
  1. Determine maximum pond width
    (Line (14) ÷ Line (9)) x 200 = ________ m (________ft)

    If pond side slopes vary by more than 50%, the calculated pond width will be different than the actual field pond width. For accuracy, separate the sides and calculate individually.
________m
________ft
  1. Obtain maximum flooding time from Table 4.34
________ hours
  1. Determine outlet capacity
    Line (7) ÷ (Line (17) - Line (6)) x 0.000277
    = ________ x 0.000277
    = ________ m3/sec (________ft3/s)
________m3/s
________ft3/s
  1. Horizontal pipe capacity required (this WASCoB from
    Line (18))
________m3/s
________ft3/s
  1. Riser pipe diameter required (this WASCoB) from
    Table 4.19-M to 4.20-M (4.19-I to 4.20-I)
________mm
________ in
  1. Maximum flow through riser pipe (this WASCoB) from
    4.19-M to 4.20-M (4.19-I to 4.20-I)
________m3/s
________ft3/s
  1. If applicable, orifice plate diameter used (this WASCoB) from Table 4.21-M to 4.22-M (4.21-I to 4.22-I) (attempt to equal or slightly exceed Line (19) value)
________mm
________ in.
  1. If applicable, maximum flow through riser pipe orifice plate (this WASCoB) from Table 4.21-M to 4.22-M
    (4.21-I to 4.22-I)
________m3/s
________ft3/s
  1. Horizontal pipe flow from Line (31) for upper WASCoB(s) (enter 0 if this is the upper WASCoB)
________m3/s
________ft3/s
  1. Minimum horizontal pipe flow (below this WASCoB, i.e., including this WASCoB + upper WASCoB flows)
    Line (19) + Line (24)
    = ________ + ________ = ________ m3/s (________ft3/s)
________m3/s
________ft3/s
  1. Minimum horizontal pipe slow (below this WASCoB)
________ %
  1. Horizontal pipe size required (below this WASCoB) using flow from Line (25), pipe slope from Line (26) and Table 4.18-M (4.18-I), Figure 4.31 or OMAFRA Publication 29, Drainage Guide for Ontario
________mm
________ in.
  1. Maximum possible flow in horizontal pipe using pipe size from Line (27), pipe slope from Line (26) (below this WASCoB) and Figure 4.31
________m3/s
________ft3/s
  1. Extra horizontal pipe capacity (below this WASCoB)
    Line (28) - Line (24)
    = ________ - ________ = ________m3/s (________ft3/s)
________m3/s
________ft3/s
  1. Restricting flow (identify as the smallest value of Line (21), Line (23), (if applicable; ie. an orifice plate is used) and Line (29)). If no orifice plate used, Line (23) = Line (21), do not insert 0 value.
________m3/s
________ft3/s
  1. Horizontal pipe flow transferred to lower WASCoB
    Line (30) + Line (24)
    = ________ + ________ = ________ m3/s ________ft3/s)
    If the value from Line (31) is considerably less than Line (28), consider increasing water inflow (ie. increase riser pipe size at this WASCoB location up to maximum value of Line (28)).
________m3/s
________ft3/s
  1. Surface water transfer from Line (33) for upper WASCoB(s)
    Enter 0 if this is the upper WASCoB
________m3/s
________ft3/s
  1. Surface water transfer to lower WASCoB
    Line (32) + Line (5) (this WASCoB)
    = ________ + ________ = m3/s (________ ft3/s)
________m3/s
________ft3/s
  1. Check emergency overflow spillway type to be used
_____ Grass lined
_____ Rock lined
  1. Determine emergency overflow spillway capacity from
    Line (33)
________m3/s
________ft3/s
  1. Determine emergency overflow spillway notch dimensions from
    Table 4.35-M (4.35-I) to meet capacity requirements from Line (35)
  • Notch width (L)
________ m
________ ft
  • Notch depth (D)
________ m
________ ft
  1. Actual berm height (Note: Freeboard is 10% of Line (14) to maximum of 0.15 m (6 in.))
    Line (14) + freeboard + notch depth (D) (Line 36))
    = ________ + ________ + ________
    = ________m (________ft)
________ m
________ ft
  1. Actual berm length
    (Line (37) ÷ Line (9)) x 200
    = ________ x 200 = ________ m (________ ft)
________ m
________ ft
  1. Berm side slope (minimum 2:1, maximum 8:1)
________ : 1
  1. Top width of berm
    (Note: Default width of 1.2 m (4 ft))
1.2 m
4 ft
  1. Bottom width of berm
    Line (40) + (2 x Line (37) x Line (39))
    = ________ + (2 x ________ x ________)
    = ________m (________ft)
________ m
________ ft
  1. Earth volume for berm from
    Table 4.36-M to 4.38-M (4.36-I to 4.38-I)
________m3
________yd3

Proceed with the design of the next (lower) Water and Sediment Control Basin. Complete a separate Water and Sediment Control Basin (WASCoB) Design Information Sheet (Multiple WASCoB System).

For more information:
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