Septic-to-Sewer Conversion Technology Optimization

Aging septic tank systems used for the treatment of residential/commercial wastewater were determined to leak and negatively impact groundwater and nearshore water bodies over time by releasing nitrogen and phosphorus into the environment. To reduce these impacts, the State of Florida enacted Senate Bill 712, the 'Clean Waterways Act' (Chapter 2020-150, Laws of Florida). This new law requires a wide range of water quality protection provisions aimed at minimizing impacts from known nutrient pollution sources and includes changes to the Florida Department of Agriculture and Consumer Services Basin Management Action Plan program. The law covers both permitted point source contributors, including National Pollutant Discharge Elimination System permitted discharge points and non-point source contributors like agriculture and residential septic systems. In response to this bill and community outcry to clean the Indian River Lagoon, one of the most biodiverse estuaries in the Northern Hemisphere that is home to more than 4,300 species of plants and animals, Brevard County passed a referendum to fund the Save Our Indian River Lagoon Program (expected to exceed $160 million) which includes the elimination of septic tanks located in areas adjacent to the lagoon. This presentation focuses on the technology selection and design optimization to be used for the elimination of septic systems and conveyance of wastewater to existing wastewater treatment facilities in three areas adjacent to the Indian River Lagoon known as South Merritt Island, North Merritt Island, and Little Hollywood, and the selection of the best collection system technology. Brevard County first evaluated three technologies for the septic to sewer conversions including gravity, vacuum, and low pressure. Gravity sewers are defined as gravity mains with lift stations located to minimize deep excavations in Florida's high-water table. Vacuum technology consists of a vacuum main connected to valve pits that serve multiple residents and is driven by one or more vacuum pump stations. Low pressure consists of grinder pumps located on individual private property energized by the property owner's electrical connections that pump wastewater through low-pressure laterals to mains that convey the wastewater. Rather than selecting a 'preferred' technology across all three areas, County staff and Wade Trim completed an evaluation to select the optimal technology that will bring the highest value to the program. The three areas were divided into subareas and each subarea's specific characteristics were considered. A rating system was developed that considered geography, parcel density, operation and maintenance, capital cost, etc., and impacts on private property owners and weighted the importance of each. Brevard County recognized that private property owners are the most impacted stakeholder in septic-to-sewer conversion projects and made resolving private property challenges a priority in the technology evaluation and selection process. Although private property owners benefit from the removal of the septic system and a potential property value increase from the connection to a centralized sewer system, this benefit can quickly be dismissed if the system technology does not 'fit' with their property conditions. Deep parcels, or parcels with elevations lower than the right-of-way struggle in vacuum and gravity collection systems. Sparsely populated subareas often push the cost-per-connection figures to unaffordable levels for vacuum technology. Florida law mandates on-site grinder pumps to be operated and maintained by the governing body requiring private property owners to allow constant access of municipal staff onto their property. The balance of private property impacts to technology costs, and the impacts of area characteristics (geography, parcel density, etc.) led to a combination of collection system technologies being selected throughout the three areas to maximize the value of Brevard County's infrastructure investment and garner buy-in by the residential/commercial property owner. Learning Objectives: No. 1 — Attendees will understand wastewater collection technologies and how private property characteristics impact, and are impacted, by the wastewater collection technology that serves them. No. 2 — Attendees will understand how to optimize collection system technology selection based on property and area characteristics such as geography, population density, right-of-way conditions, etc.