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Recommendations of the On -Site Wastewater Treatment Systems Nitrogen Reduction Technology Expert Review Panel February 2014 In addition to the distinction between in situ and ex situ BMPs, the OWTS Expert Panel recognized fundamental differences between proprietary and nonproprietary BMPs. Proprietary systems are those developed, marketed, and constructed by a manufacturer. Nonproprietary systems are those designed on a case-by-case basis for each site. Tables ES -1, ES -2, and ES -3 address nonproprietary BMPs. A two-tiered approval protocol is recommended for proprietary BMPs since the manufacturer typically has standardized design and operating protocols, which increase the likelihood that the system will perform consistently if the manufacturer's recommendations are followed. The proprietary BMP protocol consists of an initial provisional approval on the basis of a recognized third -party testing protocol. A final approval, based on the results of the field testing, is also recommended. Nonproprietary BMPs, however, require evaluation on an individual basis unless the state or local government validates the performance of nonproprietary systems that are constructed with standardized system designs and materials and operated under recognized and specified operation and maintenance (O&M) protocols. At a minimum, all of the in situ and ex situ BMPs described should have a system operator (typically a contract operator) consistent with the U.S. Environmental Protection Agency (USEPA) Level 2 management program model (USEPA 2003). The operator performs specified O&M activities, verifies proper system function, and reports back to the local health department (LHD) or state. An operating or construction permit should also be required. State -issued and renewable permits consistent with USEPA's Level 3 management program model are encouraged but not deemed mandatory for reduction credit. Responsible management entities (RMEs) are also encouraged and, for permeable reactive barriers (PRBs), required. During the course of their work, the OWTS Expert Panel considered a number of additional BMPs and related issues. Where applicable, the OWTS Expert Panel provided information and recommendations to help the CBPO and future Expert Panels refine the representation of on-site systems in the CBPO model and better understand factors associated with TN load reductions from this sector. The OWTS Expert Panel's broad recommendations include the following: Ensuring sufficient alkalinity is critical for nitrification and thus TN reduction. Although it is frequently monitored, little effort has been made to control alkalinity in on- site TN reduction systems. Additional research and development of alkalinity control methods would help optimize the TN removal associated with biological nitrogen removal systems and, if widely implemented, could allow for higher TN reduction credits to be justified for OWTS BMPs. The critical concern is that alkalinity control be relatively easy to manage and ideally, not be reliant on the system owner (e.g., homeowner) for effectiveness. BMP sampling is encouraged by the OWTS Expert Panel, but not recommended as mandatory for ongoing BMP verification or used to disqualify credit at individual sites. Monitoring plans should be left to the discretion of the states. Nevertheless, installation of BMPs throughout the watershed offers a good opportunity to collect additional data that could be useful in refining TN reduction performance and also suggest design or operational enhancements. Numerous protocols for and examples of statistically robust sampling and assessment exist, and interested parties can use them as models to design their own programs. OTETRATEC.J.. 10