In order to comply with the National Pollutant Discharge Elimination System (NPDES) MS4 Phase II requirements, the City of Arnold is required to map the location of all stormwater discharges within the city limits. Based on a list of recommendations from a recent Missouri DNR audit, the City must complete the mapping of storm sewer system outfalls and perform dry-weather screening regularly at these outfalls.  Screening involves checking each outfall when stormwater from a rain event is not flowing through the system. With assistance from their contractor, Tetra Tech, Inc., the City of Arnold will begin field mapping in the next month. The work is expected to be completed by February 2013. The work may require entry onto private property to accurately identify the location of all discharges.

To meet the requirements, the mapping/screening will be performed by a two-person team consisting of a representative of the City of Arnold and a Tetra Tech Environmental Scientist. The field team will physically locate discharge outfalls by walking the entire stream system. Outfalls are defined as pipes, culverts, ditches, or streams. Once located, the field crew will survey the coordinates of each outfall location using a GPS receiver. Information concerning the name of the stream the discharge is entering, type of discharge (ditch or pipe), size of ditch or pipe, and a description of the discharge will be recorded. For the Meramec and Mississippi Rivers, mapping/survey activities will be conducted by boat.

Since the entire length of each stream has to be observed, the field crew will also collect GPS location information of log jams, large accumulations of trash or debris and other items that may require the City’s attention (collapsing structures, high erosion areas, stream blockage, etc.). Each discharge location, log jam, trash/debris accumulation, or other items of interest will be photo documented and a description of the item will be recorded.

Results of the surveys will be provided to the City of Arnold and will include: the physical descriptions, GPS coordinate locations, an updated Outfall Map, and photographs of each outfall or other item of interest. 

For more information, contact the City of Arnold Stormwater Department at 636-282-2386.

For more information regarding Tetra Tech, Inc., please visit www.tetratech.com.