Third Cycle sewer system evaluation surveys for three 7-Eleven stores in Miami-Dade County

What the project was

Three 7-Eleven stores in Miami-Dade County, one in Cutler Bay and two in Miami, each operate a private sanitary sewer system that discharges into the county's wastewater collection and transmission system through a small pump station. Under Chapter 24 of the Miami-Dade County Code every such system, whether a utility owns it or not, has to be evaluated on a recurring ten-year cycle, with the findings submitted to the Department of Environmental Resources Management for review and approval. RSP Engineers was the engineer of record for the Third Cycle Sewer System Evaluation Survey at all three.

The survey is not a formality. An SSES exists to find and correct excessive infiltration and inflow, meaning groundwater entering through defects and stormwater entering through openings that should not be there, and Chapter 24 sets the limit at less than 5,000 gallons per inch of pipe diameter per day per mile of pipe and laterals. Finding those defects keeps sewage out of the ground, reduces wear on the pump station and lowers what it costs to run.

Why the deadline matters

The consequence of letting an SSES lapse is not a fine, it is a hold on growth. Section 24-42.3(3) prevents new sewage flows being authorised for a sanitary sewer basin, pump station or system until the reports Chapter 24 requires have been completed on schedule. For a retail operator that means a non-compliant permit can sit between a site and its certificate of occupancy, or between a remodel and the extra capacity it needs. It is the kind of problem that gets discovered at the worst possible moment, when the construction is finished and the opening date is already set.

The fieldwork also has a narrow window. Flow testing has to be carried out between 1 June and 30 November of the same calendar year, the wet season, and where the groundwater level is tidally influenced, which in coastal Miami-Dade is a great deal of the county, testing has to happen within two hours of local high tide. Miss the season and the survey waits a year.

What the work involved

Each of the three systems is small, and none of them contains a single manhole. They are short runs of 4-inch PVC between cleanouts, falling to a wet well with two submersible pumps. Across the three sites the survey covered 541.8 feet of gravity sewer. What these systems lack in length they make up in exposure, because a lift station in a parking lot gets walked over, driven over and pressure washed, and its lid is the most likely inflow path in the whole system.

The surveys were built around visual inspection and smoke testing rather than camera work. On a system with no manholes and a few hundred feet of 4-inch pipe, smoke introduced at the wet well reaches every branch, and anywhere it surfaces that is not a vent is a defect. Each system was inspected, every cleanout was opened and graded, the pump station and its cover were examined, and DERM was notified in advance of the tests that require notice. Five smoke tests were carried out across the three stores between March and July 2026 using a plumbing smoke tester with liquid smoke, in dry weather with no precipitation recorded at the time of testing. At one store the grease interceptor line was smoke tested separately from the sanitary collection system, because a grease interceptor sits on its own branch and one injection point does not prove both.

Flow testing was not required at any of the three systems. Each survey closed with an updated Sanitary Sewer Collection System drawing, signed, sealed and dated by a professional engineer licensed in Florida, which Section 24-15.2 requires for the report and the drawings alike.

What the testing found

Two of the three stores needed a repair, and in both cases it was the lift station lid. At the Cutler Bay store the lid was found loose with smoke escaping from it during the first test. It was sealed on 16 April 2026 and the system re-tested on 5 June, when smoke emerged from the lid as designed and nowhere from the ground beside the building. At the Bird Road store the same finding came out of the March test and was corrected on site the same day; the second smoke test in July showed smoke leaving through the sanitary vent system as expected, and no emissions from the ground, the building foundation, the cleanouts or anywhere else that would indicate infiltration, inflow, a cross connection or a structural defect.

The Cutler Bay store also had a leak inside the wet well. It was identified during the inspection and corrected while the crew was on site, rather than written up and scheduled as a follow-up.

The third store, on NW 72 Avenue, passed at the first attempt: cleanouts in good condition, the gravity system operating normally, no smoke along the sanitary sewer line and no repairs required.

Approvals

DERM's Water and Wastewater Division reviewed each submittal against the Chapter 24 requirements and found all three systems in compliance with the Third Cycle SSES code requirements: PSO-0393 on 16 June 2026, PSO-0611 on 7 July 2026 and PSO-0388 on 23 July 2026. The Fourth Cycle reports for all three permits fall due on 12 November 2032.

The outcome

Three permits that each carried an open compliance obligation now carry an approval letter instead, and the two defects the surveys found were repaired during the survey rather than deferred to a second submittal. The practical result for the operator is that none of the three stations is sitting in the way of a future connection, a remodel or a certificate of occupancy.

For anyone responsible for a portfolio of small commercial sites, the useful observation is that these systems are easy to forget precisely because they are small. A private lift station behind a convenience store has no dedicated operator, and the obligation attaches to the permit rather than to the building, so it survives a change of tenant, manager or facilities contractor. The cheap version of this work is the one done inside the wet season with the defects fixed on the day they are found. The expensive version is the one discovered when a permit is suddenly needed in a hurry.