log y = 2.00 + 0.008 (x)
where y = Ft2/100 Gals
x = Percolation rate in minutes/inch
Notwithstanding the above, the minimum absorption area for single family residential dwellings shall be 400 square feet.
Table 5.4. Area Requirements for Absorption Trenches Receiving Septic Tank Effluent. | ||||||
Percolation Rate (Minutes/Inch) | Area Required (Ft2/100 Gals) | Area Required (Ft2/Bedroom) | ||||
Gravity | Gravity Gravelless | Low Pressure Distribution | Gravity | Gravity Gravelless | Low Pressure Distribution | |
5 | 110 | 83 | 110 | 165 | 124 | 165 |
10 | 120 | 90 | 120 | 180 | 135 | 180 |
15 | 132 | 99 | 132 | 198 | 149 | 198 |
20 | 146 | 110 | 146 | 218 | 164 | 218 |
25 | 158 | 119 | 158 | 237 | 178 | 237 |
30 | 174 | 131 | 164 | 260 | 195 | 255 |
35 | 191 | 143 | 170 | 286 | 215 | 260 |
40 | 209 | 157 | 176 | 314 | 236 | 264 |
45 | 229 | 172 | 185 | 344 | 258 | 279 |
50 | 251 | 188 | 193 | 376 | 282 | 293 |
55 | 275 | 206 | 206 | 412 | 309 | 309 |
60 | 302 | 227 | 217 | 452 | 339 | 325 |
65 | 331 | 248 | 228 | 496 | 372 | 342 |
70 | 363 | 272 | 240 | 544 | 408 | 359 |
75 | 398 | 299 | 251 | 596 | 447 | 375 |
80 | 437 | 328 | 262 | 656 | 492 | 394 |
85 | 479 | 359 | 273 | 718 | 539 | 409 |
90 | 525 | 394 | 284 | 786 | 590 | 424 |
95 | 575 | 489 | 288 | 862 | 733 | 431 |
100 | 631 | 536 | 316 | 946 | 804 | 473 |
105 | 692 | 588 | 346 | 1038 | 882 | 519 |
110 | 759 | 645 | 379 | 1138 | 967 | 569 |
115 | 832 | 707 | 416 | 1248 | 1061 | 624 |
120 | 912 | 775 | 456 | 1368 | 1163 | 684 |
Table 5.5 Soil Absorption Area Loading Rates for Systems Receiving TL-2 Effluent or TL-3 Effluent | ||||||||
Percolation Rate (mpi) | TL-2 Effluent | TL-3 Effluent | ||||||
Pressure Trench* Loading (gpd/ft2) | Gravity Trench* Loading (gpd/ft2) | Drip** Loading) (gpd/ft2) | Pad/Mound Loading** (gpd/ft2) | Pressure Trench* Loading (gpd/ft2) | Gravity Trench* Loading (gpd/ft2) | Drip** Loading (gpd/ft2) | Pad/Mound Loading** (gpd/ft2) | |
5 | 1.8 | 1.80 | 0.60 | 1.20 | 3.0 | 3.00 | 1.00 | 1.66 |
10 | 1.67 | 1.67 | 0.56 | 1.11 | 2.67 | 2.67 | 0.89 | 1.66 |
15 | 1.53 | 1.53 | 0.51 | 1.02 | 2.33 | 2.33 | 0.78 | 1.66 |
20 | 1.4 | 1.40 | 0.47 | 0.93 | 2.0 | 2.00 | 0.67 | 1.66 |
25 | 1.30 | 1.30 | 0.43 | 0.86 | 1.75 | 1.75 | 0.58 | 1.33 |
30 | 1.2 | 1.13 | 0.40 | 0.80 | 1.5 | 1.41 | 0.50 | 1.11 |
35 | 1.10 | 0.98 | 0.37 | 0.73 | 1.38 | 1.22 | 0.46 | 0.95 |
40 | 1.00 | 0.84 | 0.33 | 0.66 | 1.25 | 1.05 | 0.42 | 0.83 |
45 | 0.90 | 0.73 | 0.30 | 0.60 | 1.13 | 0.91 | 0.38 | 0.74 |
50 | 0.8 | 0.62 | 0.27 | 0.53 | 1.0 | 0.77 | 0.33 | 0.67 |
55 | 0.76 | 0.57 | 0.25 | 0.50 | 0.94 | 0.71 | 0.31 | 0.61 |
60 | 0.71 | 0.51 | 0.24 | 0.47 | 0.89 | 0.64 | 0.30 | 0.55 |
65 | 0.67 | 0.46 | 0.22 | 0.44 | 0.83 | 0.57 | 0.28 | 0.51 |
70 | 0.62 | 0.41 | 0.21 | 0.41 | 0.78 | 0.51 | 0.26 | 0.48 |
75 | 0.58 | 0.36 | 0.19 | 0.38 | 0.72 | 0.46 | 0.24 | 0.44 |
80 | 0.53 | 0.32 | 0.18 | 0.35 | 0.67 | 0.40 | 0.22 | 0.42 |
85 | 0.49 | 0.28 | 0.16 | 0.33 | 0.61 | 0.35 | 0.20 | 0.39 |
90 | 0.44 | 0.24 | 0.15 | 0.30 | 0.56 | 0.30 | 0.19 | 0.37 |
95 | 0.4 | 0.20 | 0.13 | 0.27 | 0.5 | 0.25 | 0.17 | 0.35 |
100 | 0.37 | 0.19 | 0.12 | 0.25 | 0.46 | 0.23 | 0.15 | 0.33 |
105 | 0.34 | 0.17 | 0.11 | 0.23 | 0.43 | 0.21 | 0.14 | 0.32 |
110 | 0.31 | 0.16 | 0.10 | 0.21 | 0.39 | 0.19 | 0.13 | 0.30 |
115 | 0.28 | 0.14 | 0.09 | 0.19 | 0.35 | 0.18 | 0.12 | 0.29 |
120 | 0.25 | 0.13 | 0.08 | 0.17 | 0.32 | 0.16 | 0.11 | 0.28 |
*Loading rates to trenches, whether gravity or pressure dosed, are based on the gallons per day of wastewater applied to the bottom of the trench. **Loading rates to drip systems, pads, and mounds are based on the infiltrative surface area provided and are on an aerial basis. |
12 Va. Admin. Code § 5-610-950
Statutory Authority: §§ 32.1-12 and 32.1-164 of the Code of Virginia.