The amount of eroded soil and dissolved pollutants that move from construction sites to nearby lakes or streams is controlled, in part, by the quantity of runoff produced during a storm.

Compost-treated areas produced significantly less runoff during high intensity rainfall (4 inches per hour) than conventionally-treated roadside areas.

• As shown in table 1, runoff from compost-treated areas during a 30-minute high intensity rain storm was less than 0.8% of the runoff from areas treated with topsoil, and 0.5% or less of that from compacted subsoil.
   
• Although the amount of runoff from the yard waste compost (shown in table 1) appears to be less than from the other two composts, these differences are not statistically significant.
   
• Due to the water absorbing capacity of the compost, initiation of runoff from compost-treated areas was significantly delayed.  While compacted subsoil and topsoil typically began producing runoff within 5 to 8 minutes after rainfall began, areas treated with any of the three types of compost took, on average, 30 – 60 minutes to begin producing runoff (shown in table 2) . Since most naturally-occurring high-intensity storm events last less than 30 minutes, compost treatments would be expected to reduce the total number of storms each year that produce runoff.

• The reductions in quantity and frequency of runoff provided by compost treatments were similar under both un-vegetated and vegetated conditions.  These results show that compost blankets can provide storm water runoff control (and erosion control) on construction sites before vegetative cover can  be established.