Coastal Resiliency Program Phase 1 for the City of St. Augustine, Florida

Client

St. Augustine Public Works Department

Services Provided

GIS Data Management, BMP Alternatives Analysis, Stormwater Retrofit Design, Sea Level Rise, Resiliency and Adaptation, Grant Support and Award

A fact sheet about an outfall site is shown on the left, including maps, tables, and data. On the right are two photos of a black pipe discharging water beneath a bridge and into a creek, surrounded by mud and vegetation.

Location

St. Augustine, Florida

Project Practice Areas

Environmental Management

Type of Facility

Sea Level Rise

Project Specifics

As a result of damaging storms such as Hurricane Matthew in 2016 and ongoing issues related to sea level rise, flooding events are occurring more frequently along the low-lying coastal areas of the City of St. Augustine.

Geosyntec Scope of Services

Tidal flooding is the most common type of flood event, characterized by spring or king tide events that cause tide waters to enter urban areas even without storm events. To address tidally-influenced nuisance flooding within St. Augustine, the City desired to implement tidal and stormwater backflow prevention on vulnerable stormwater outfalls within the Davis Shores subdivision, a particularly vulnerable residential area located on Anastasia Island.

Geosyntec’s Scope of Services

Geosyntec performed a rapid assessment of eight stormwater outfalls within the Davis Shores subdivision affected by tidal flooding. Geosyntec worked with the city’s in-house stormwater maintenance crews to establish suitability of in-pipe of end-of-pipe backflow prevention retrofits using TideFlex and WaStop backflow prevention devices. Measurements and observations were taken at each outfall and upstream storm sewer system to determine:

Issues that would affect installation
Remediation and maintenance needs before retrofitting
Long-term maintenance and cleaning requirements
Accessibility constraints to install and maintain
Installation personnel requirements (in-house city maintenance staff or term contractor)

Outfall fact sheets were developed for each outfall to enable decision making as to the appropriate installation methodology, backflow preventer type, and recommended retrofit location (end-of-pipe or upstream improvement).

Notable Accomplishments

Geosyntec’s work helped the city to apply for and receive a St. Johns River Water Management District Cost Share grant for the installation costs. The backflow prevention devices were installed primarily by the city’s internal maintenance staff and have successfully reduced nuisance flooding.

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