Selection of the linear loading rate is a very important step in designing a mound system. The linear loading rate determines the length of the mound along the contour and controls the landscape hydraulic loading. Based on the soil and site evaluation conducted by a qualified professional and in accordance with Bulletin 905, Soil and Site Evaluation for Onsite Wastewater Treatment, identify the nature of the limiting condition. Using Table 1, select the corresponding linear loading rate. The space-limited value is a less conservative value and should be used only if limited suitable area is available.
| Table 1. Linear Loading Rates Based on Limiting Conditions | |||
| Nature of Limiting Condition | Linear Loading Rate Range (gpd/linear ft) | ||
|---|---|---|---|
| Conservative Value | Space-Limited Value | ||
| Solid bedrock | 3 | to | 4 |
| Impermeable soil layer | 3 | to | 4 |
| Seasonal high water table | 3 | to | 4 |
| Semipermeable soil layer | 5 | to | 6 |
| Fractured compacted till | 5 | to | 6 |
| Creviced or fractured bedrock | 8 | to | 10 |
| Sand and/or gravel layer | 8 | to | 10 |
Linear Loading Rate:
The soil evaluation revealed a limiting condition as a restrictive soil
layer (with fine platy structure above solid bedrock). The corresponding
linear loading rate (space-limited value) from Table 1 is 4 gpd/lf.