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Recommendations of the On -Site Wastewater Treatment Systems Nitrogen Reduction Technology Expert Review Panel February 2014 Data sharing and interstate reciprocity should be the focus of data management efforts to support Chesapeake Bay watershed total maximum daily load (TMDL) implementation. States and local jurisdictions generally lack the resources to ensure BMP performance at a high level of confidence, either through sampling or field inspection. Additionally, duplicative protocols for technology approval can present logistical and financial obstacles for technology developers. These obstacles can preclude the display of promising TN reduction technologies, potentially at the expense of Chesapeake Bay watershed water quality. Therefore, Chesapeake Bay watershed states and other jurisdictions should share information to the greatest extent possible. USEPA Office of Wastewater Management (OWM) has offered to help facilitate data sharing. Soil type should be considered a potential predictor of TN reduction performance in future watershed models. The OWTS Expert Panel recognizes that the characteristics of the soil within the drainfield highly influence both baseline and BMP on-site system performance. Soil texture, in particular, is a relatively easy characteristic to represent in a model that is known to influence treatment. The existing model only allows the assignment of a single soil texture per county. Although the OWTS Expert Panel's analysis suggests that it is feasible to assign a predominant soil texture for each county, it is recommended that the future Attenuation Expert Panel explore this issue in more detail, since it relates to the interaction between natural soil conditions and system performance. Table ES -1. Summary of BMP Recommendations for Ex Situ Unit Processes. 1 (� OTETRATECH,INC. 11 Ex Situ Best Management Reduction Practice Qualifying Conditions Credit' Septic tank (baseline N/A 0 practice) NSF 40 Class I • Certified as Class I under NSF International Standard 40 or 20% Equivalent similar (e.g., CAN/BNQ 3680-600, CEN Standard 12566-3) Secondary Systems . Design, installation, and operation in accordance with manufacturer recommendations and state or local regulation Intermittent media . Timer -based flow equalization with 12-24 doses/day 20% filters . 2' depth (sand) media ES = 0.5-1.0 mm; UC <_ 4.0; < 0.5% passing #200 sieve • HLR <_ 2 gpd/sf • OLR <_ 5 Ib BOD/1,000 sf • Uniform, pressurized distribution <_ 6 sf/orifice Constructed wetlands . <_2' depth media ES = 40-80 mm inlet/outlet-, ES = 20-30 20% mm treatment zone, extending 0.1 m above water level • Length -to -Width ratio < 10:1 • Surface Area >_ 54 sf/PE • Width between 0.56 and 1.31 feet/PE • Outlet structure allows for variable flooding depth • 6" top layer of planting media OTETRATECH,INC. 11