Appendix 3. Worksheet for sludge volume and treatment volume Revised August 2008
The average thickness of the sludge layer and the thickness of the existing liquid (sludge-free) treatment zone are determined from information on the Lagoon Sludge Survey Form (Items O and P, respectively). In this example, the average sludge layer thickness is 2.5 feet and the existing liquid treatment zone is 3.5 feet. If the lagoon has a designed sludge storage volume, see notes at end of the worksheet. The dimensions of the lagoon as measured and the side slope are needed for calculations of sludge volume and of total treatment volume. If the lagoon is a standard geometric shape, the sludge volume and treatment volume in the lagoon can be estimated by using standard equations. For approximate volumes of rectangular lagoons with constant side slope, calculate length and width at the midpoint of the layer, and multiply by layer thickness to calculate layer volume, as shown in the example. For irregular shapes, convert the total surface area to a square or rectangular shape. For exact volumes for lagoons with constant side slope, the "Prismoidal Equations" may be used.
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Example |
Your lagoon |
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|
1. Average Sludge Layer Thickness (T) |
2.5 ft |
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2. Depth of lagoon from top of bank to bottom soil surface (D) |
11 ft |
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3. Slope = horizontal/vertical side slope (S) |
3 |
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4. Length at top inside bank (L) |
457 ft |
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5. Width at top inside bank (W) |
229 ft |
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6. Length at midpoint of sludge layer: Lm = L - 2 S (D- (T/2)) |
398.5 ft |
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7. Width at midpoint of sludge layer: Wm = W - 2 S (D - (T/2)) |
170.5 ft |
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8. Volume of sludge (Vs): Vs = Lm Wm T |
169,860 ft3 |
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9. Volume in gallons (Vsg): Vsg = V * 7.5 gal/ft3 |
1,273,950 gal |
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10. Thickness of existing liquid treatment zone (Y) |
3.5 ft |
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11. Thickness of total treatment zone (Z): Z = T + Y |
6.0 ft |
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12. Length at midpoint of total treatment zone: Lz = L - 2(S) (D - (Z/2) |
409 ft |
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13. Width at midpoint of total treatment zone: Wz = W - 2(S) (D - (Z/2) |
181 ft |
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14. Volume of total treatment zone (Vz): Vz = Lz Wz Z |
444,174 ft3 |
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15. Ratio (R) of sludge layer volume to total treatment volume: R = Vs/Vz If the ratio exceeds 0.50, than a sludge Plan of Action may be required. Check with DWQ for information on filing the Plan of Action. |
0.38 |
Note: If the lagoon has a designed sludge storage volume (DSSV), subtract that volume from both the volume of sludge (Vs) (Item 8) and from the volume of total treatment zone (Vz) (Item 14), and take the ratio:
R = (Vs - DSSV) / (Vz - DSSV)
Example: If DSSV = 85,000 ft3, then R = (169,860 - 85,000) / (444,174 - 85,000)
R = 84,860 / 359,174 = 0.24
