Landfills

Apparently there were a lot of landfills in Tampa. The city has research on those landfills. Rowlett Park is one of those sites of a former landfill.
"The City of Tampa Solid Waste Department disposed of municipal solid wastes in the area until 1956. Historical aerial photographs indicate that nuisance dumping continued until the early 1980’s. The total volume of landfill debris is estimated by the Solid Waste Department to be approximately 13,400 cubic yards and two to five feet thick. Site elevations range from +20 to +45 feet above mean sea level, with the surface contours sloping towards the Hillsborough River."

There was one at Martin Luther King and 22nd
Junior high school and playgrounds over landfill.

There was one at Yukon and Tampa

Landfill #38 is located on the south side of Yukon Street, one block west of North Florida Avenue. The impacted area reportedly consists of approximately one acre. This was a low lying area into which trash was disposed. This practice stopped in approximately 1963. The land is presently privately owned.
The property is bounded by Yukon Street on the north. Duplex residential units that front on North Tampa Street border the eastern side of the landfill area. It is not known if these units extend westward onto the landfilled area. The property lines of individual residential lots that front on North Ashley Street border the western edge of the subject property. The south end of the area is bounded by the northern boundaries of individual residences

Near Wellswood at Macdill and Giddens was another site:

Landfill #23 is located in northwest Tampa in Section 3, Township 29 South, Range 18 East (Figure 23-1 and 23-2). The landfill study area borders on North MacDill Avenue on the east. The remainder of the parcel is surrounded by residential lots (Figure 23-3). The parcel encompasses approximately 3.3 acres.

Records at the City of Tampa Sanitation Department contain a letter from the property owner authorizing the City to use the property for waste disposal. According to these records, however, the City may never have disposed of debris at the site.

The 1956 USGS topographic map, revised in 1981 (Figure 23-4), shows Pralls Lake designated as a "dry lake" with topographic lines showing a channel leading from Pralls Lake to the wet area to the southwest. This dry lake has been filled, but the source and type of fill is not known.