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Underwood and Associates was awarded the NRCS State Conservation Innovation grant to reduce stormwater discharge on a local sod farm using an application of stream restoration called regenerative stream conveyance or RSC. Water quality sampling is an important component of this grant. The goal of water quality sampling at the sod farm is to determine the nature and extent of nutrients that are an issue before the stream restoration is in place, and after. This sampling design is known as a BACI (Before, After, Control Impact) approach, and can also be described as measuring water quality pre- and post- construction. This is one of the most effective ways to study whether a given Best Management Practice (BMP) approach is effective. The hypothesis is that RSC as a BMP will reduce Total Nitrogen (TN), Total Phosphorus (TP), and Total Suspended solids (TSS) between the non-restored and restored conditions, as well as between the top of the project (also the control) and the outlet before entry into a farm pond.
The first step in setting up both the design of the restoration and the water quality sampling experiment design is to determine the flow path of water and location of greatest flow volume and erosion, i.e. the “trouble areas”, particularly during storms. For both, subsurface flow of water, as well as overland surface flow, are important to determine the treatment of water flow volume and water quality in the system. These parameters also determine the size of the BMP and how it is designed.
Because water may not be visible on the surface in all seasons, subsurface (groundwater) wells have been installed. In order to track groundwater level dynamics as well as treatment along the path of the restoration, water will be measured at four points in the RSC: one groundwater and one surface water sampling station have been located at the top of the project, the bottom at the BMP outlet, and two in between.
Samples are taken at each point of the BMP by first doing a sample rinse, and then finally filling up one bottle each for the well and the surface water. A long tube known as a “fast bailer” is lowered down the 2-inch diameter well (which is approximately 5-6 feet deep), filled once for the sample rinse and a second time to fill the water. After being filled, the bottles are put on ice for transit back to the lab for pre-analysis processing.
Within four hours of field collection, samples are pre-processed. Water samples are passed through the filter apparatus using a suction hand pump. The particles left on the filter are tested for particulate carbon and nitrogen, total suspended solids and particulate phosphorus. The filtrate (the portion of the water sample that passes through the filter) is tested for the dissolved portions of nitrogen, phosphorus and carbon, specifically Dissolved Inorganic Nitrogen (DIN - includes Ammonium), Dissolved Inorganic Phosphorus (DIP), Total Dissolved Nitrogen and Phosphorus (TDNP), and Dissolved Organic Carbon (DOC). The filters are labelled and placed in foil pouches; the filtrate is placed in a 125 ml bottle. All samples are placed on ice, and shipped next day air to Chesapeake Biological Laboratory for analysis.
Post-construction water quality sampling will begin in the spring after project installation. We look forward to offering the results of this study in the future, once all data has been collected and analyzed.
*Dr. Zinecker is a scientist for Underwood & Associates