Polluted stormwater runoff from construction sites often flows to MS4s and ultimately is discharged into local rivers and streams. Sediment is usually the main pollutant of concern. Sources of sedimentation include construction, agriculture, urban runoff and forestry. Sediment runoff rates from construction sites, however, are typically 10 to 20 times greater than those of agricultural lands and 1,000 to 2,000 times greater than those of forested lands. During a short period of time, construction sites can contribute more sediment to streams than can be deposited naturally during several decades. The resulting siltation and the contribution of other pollutants from construction sites can cause physical, chemical and biological harm to our nation's waters. For example, excess sediment can quickly fill rivers and lakes, requiring dredging and destroying aquatic habitats.
Construction stormwater runoff is covered under regulations of the Clean Water Act. In Texas, the Texas Commission on Environmental Quality (TCEQ) has primacy and issues Construction Stormwater General Permits, also called TXR150000 permits. Sites which disturb one acre or more and sites which are a common plan of development that disturbs more than one acre, are required to complete a Stormwater Pollution Prevention Plan (SWPPP), post a TCEQ construction site notice that is publicly visible and provide a copy of the construction site notice to the MS4. Construction sites which are five acres or greater (or part of a common plan of development greater than five acres) are additionally required to complete a Notice of Intent (NOI) and provide a copy to the MS4 to which they discharge. All construction sites within the City of Denton must comply with the Land Disturbing Activities section of Denton Development Code, DDC Section 35.18 and the Drainage Criteria Manual.