Case Study: Louisville, CO

Nestled near the vibrant community of Boulder, the City of Louisville, Colorado, stands as a model for improved Fats, Oils, and Grease (FOG) management. With a population of around 20,000 and a bustling downtown full of restaurants and historic charm, Louisville's approach to wastewater management is both innovative and adaptive. Their recovery from the 2021 Marshall Fire Is a testament to their resilience. Adversities such as this have shown how the City expertly balanced meeting the community’s needs with addressing the growing FOG problem.

Established in 1952, the Louisville Wastewater Treatment Plant (WWTP) has undergone several expansions to meet the city's growing population and evolving environmental standards. Originally featuring a simple settling pond and aerated lagoon, the plant added an Extended Aeration Activated Sludge system and lagoon system in 1965. Improvements continued throughout the decades, including a major remodel in 2017 which transformed the plant into a Biological Nutrient Removal (BNR) system. Initial FSE tracking commenced in 2010, and the WWTP purchased a replacement jetting truck in 2019-2020.

Year	Percent change
2017	158%
2018	15%
2019	37%
2020	-35%
2021	-6%
2022	36%
2023	-21%
2024	-100%

The BNR system can treat 2.53 million gallons per day and significantly reduces nutrient loading into Coal Creek. The WWTP's treatment process uses microorganisms to break down sewage, with stages for grit removal, aeration, and ultraviolet disinfection, before discharging treated water into Coal Creek. The plant also reuses treated water for irrigation at local facilities and stabilizes sludge into biosolids for agricultural use. Continuous upgrades including ozone treatment and SCADA monitoring (Supervisory Control and Data Acquisition–Louisville's data management software), have ensured efficient operation and consistent compliance with environmental regulations. 

The city launched its FOG program in 2015, but it wasn’t until early 2024 that they made significant strides. The project overcame initial hurdles with inconsistent tracking and staffing issues through a more structured approach to data management and dedicated personnel. Louisville employs advanced tools like BSI software for manifest tracking and Lucity for geographic mapping. This technology provides a comprehensive view of sewer lines and grease interceptors, allowing the city to prioritize inspections and maintenance effectively. 

With approximately 113 food service establishments (FSEs) under its purview, the city’s program aims to address the challenges posed by high grease levels and their impact on the wastewater treatment plant (WWTP). 

The results of Louisville's FOG program are already evident:

• WWTP Costs: Although operational costs fluctuate and some projects have caused an increase due to higher capacity needs (buying a new jet/vac truck, etc.), the WWTP has seen a decrease in maintenance and line cleaning, which  directly correlates to reduced FOG in the sewer system. Any decrease in FOG lowers operational costs at the WWTP. In 2024, operators measured the FOG buildup at the POTW to determine the efficacy of the program. The depth of the influent FOG mat was assessed through the use of a dipstick fog sampler. Plant staff sample 6 locations each month and record the depth of the grease mat. The data shows that improved operations have resulted in a 5-10% reduction in grease between June 2024 to present. 

• Fewer Sanitary Sewer Overflows: Following the implementation of the Environmental Compliance Program, the city recorded only one sanitary sewer overflow (SSO) in the last year, It occurred on a private property due to a failed grease interceptor, a testament to effective maintenance and management. SSO's are limited due to excessive jetting of the collection system. Since the program is still in its early stages and older infrastructure is in the process of being replaced, overall expenses have not yet been reduced. Education and outreach are the primary mechanisms that the WWTP employed to promote FOG reduction/voluntary compliance. 

• Maintenance Costs: Ongoing data collection shows an increase in collection system maintenance costs due to ongoing capital improvements. These improvements ought to assist with cutting maintenance costs in the future.  

• Infrastructure Longevity: Regular maintenance is helping to prevent sanitary sewer overflows. However, due to older clay pipes and the increase of jetting, they also face the barrier of needing to replace infrastructure more frequently.

Louisville’s FOG ordinance mandates that all FSEs must have a grease interceptor maintained every 90 days. This broad definition includes various establishments like coffee shops and bakeries. For areas where traditional interceptors are impractical, such as historic downtown locations, the city permits alternative solutions like under-the-sink interceptors. 

The city also enforces industrial pretreatment programs and is considering further clarifications and permits for specific food manufacturers. For example, one industrial user is installing a biodigester instead of a GI, which was a special request that was approved through the city. This was intended to combat their suspended solids and biological oxygen demand (BOD). This is one of many alternatives the city is exploring instead of committing to outdated technology. 

The city's Environmental Compliance Team, has implemented several effective strategies:

• Enhanced Outreach: Increased site visits and educational outreach to FSE’s improved compliance. Program staff encouraged FSE’s to make voluntary waste manifest submissions and created forms to help them prepare for inspections. Forms included information about the condition of interceptors, follow-up schedules for timely maintenance, and alternative requests. 

• Fixture Connections: Ensuring that all fixtures and drains are connected to grease interceptors through policy and building reviews, even if not yet mandated by ordinance. The Environmental Compliance Team is involved with new builds and tenant finish-outs that involve plumbing connections to the city collection system. The program manager reviews the building plans to determine if all fixtures in the kitchens or processes are being captured with the submitted design. If the plans for a particular project would not successfully prevent the introduction of FOG to the municipal sewer, they discuss revisions or alternatives with the user/contractor. 

• Collaborative Efforts: The city shares best management practices and program documentation with other jurisdictions. 

• Effective Tracking: The city utilizes geographic data and maintenance records to prioritize inspections and manage FOG buildup effectively. 

• Communication: Rather than trying to contact the managers of the FSE, the Environmental Compliance Team switched to reaching out to the property managers first. When they do visit establishments, they keep FSE guidance info handy to distribute to staff, even if a manager is not present. 

• Working with Other Jurisdictions/Departments: As part of the program restart, they invited numerous communities surrounding Louisville to participate in live training for inspections. They also revised all of the FOG program forms for inspection, NOVs, public education and outreach. 

Success Stories: 

• Amanda worked directly with a business on historic main street to properly size and replace a grease interceptor. Together, they completed alternate request forms, and chose a device that met the needs of the operation.  

• Similarly, a local elementary school had a grease cistern that was no longer meeting code. Input from the city opened the avenue of a cost-effective alternative to a concrete GGI, as the school is operating with a small capital improvement budget.