#D1015-00 Dewatering

BMP Factsheet NS-2

Standing water shall be eliminated within 72 hours after a storm event. Any water that ponds or forms a pool on site from either storm water or non-storm water must be dealt with effectively before a period of 72 hours.

If the water is clear and free of pollutants and not restricting the site from performing scheduled construction activities, it may be best to wait and determine if the water will percolate into the soil or evaporate completely within the 72-hour period.

If the water is contaminated and/or polluted, restricts scheduled construction activities, or will persist beyond the 72-hour period, action will need to be taken. Actions may include treating the water if pollutants are present, before discharging it off site, or dispersing the water to more dry areas on site where the water will percolate or evaporate within 72 hours. Trucks may also be used to haul polluted water off site for proper disposal or cleaning. Alternatively, an Active Treatment System (ATS) can be used on site to treat storm water before discharging. These actions may be more expensive but at times may be necessary.

Dispersing water around the site is an effective means of dust control, post rain. This is done using pumps to move the water or manual shoveling of the water.

The 72-hour limit to eliminate standing water is to prevent the production of vectors (such as mosquitoes) that use standing water as a breeding ground. By eliminating standing water from a construction site, it maintains the safety of the construction site.