Hollywood, Florida

Lowering groundwater levels as much as 15 ft. to depths of greater than 20 ft. below grade, at multiple structures concurrently, without impacting access or construction methodology.


The entire site had sandy soil approximately 45 ft. deep underlain by limestone that contributed in varying degrees to groundwater flows. Water levels fluctuated seasonally around 5-7 ft. below ground surface. Construction occurred during hurricane season and was impacted by Hurricane Irma, the 5th costliest hurricane to hit the mainland U.S.



Griffin dewatered for the 70 ft. x 50 ft. sheeted foundation and elevator core utilizing nine (9) deep wells. The original plan called for six (6) deep wells; however, the foundation was within a lake that was previously backfilled and compacted causing the permeability of the soil and production of the wells to vary from one side of the excavation to the other. During installation a pump test was conducted. The site specific data was used to update the original design model to determine the likely impact of the planned dewatering system. The updated model showed that additional flow (and wells) would be necessary to accomplish drawdown. All wells were installed to ±40 ft. The entire system pumped approximately 650 gallons per minute (GPM) and provided water level drawdown to approximately 20 ft. below ground surface for the 4-month duration of the dewatering system operation.


The pilecaps for this structure required wellpoint dewatering of two (2) separate sheeted foundation areas with a total perimeter of 800 linear ft. The water level was maintained approximately 12 ft. below grade for the 3-month duration of the dewatering system operation.


The basement level of this structure required wellpoint dewatering of a total sheeted perimeter of 500 linear ft. The water level was maintained at approximately 19 ft. below grade for the 4-month duration of the dewatering system operation. A supplementary wellpoint system was installed in the base of the excavation to dewater one (1) deep elevator pit.


The subsurface pool equipment room required wellpoint dewatering of a total perimeter of 300 linear ft. Approximately 100 ft. of the excavation was completed by open cutting and the remaining 200 ft. was sheeted. The water level was maintained approximately 15 ft. below grade for the 4-month duration of the dewatering system operation.


Griffin dewatered for the 650 linear ft. tunnel to move cars between the casino entrance and the parking garage. The original plan called for seventeen (17) deep wells. Once construction began a pump test was completed. This information was utilized to update the original design model to determine the anticipated performance of the planned dewatering system. It was determined that additional drawdown would be needed at the major utility crossing at the deepest point of the tunnel. To obtain the required drawdown, two (2) wells were added and well spacing was modified to maximize drawdown throughout the tunnel. All wells were installed to ±40 ft. The entire system pumped approximately 2,000 GPM and provided water level drawdown to approximately 20 ft. below ground surface for the 6-month duration of the dewatering system operation.


This basement feature required wellpoint dewatering of the sheeted excavation with a total perimeter of 320 linear ft. This feature was added partway through construction as a change to the original scope. Dewatering of hallways leading to and from basement (60 linear ft. each) was also included, as was dewatering at the tie-in to valet tunnel. The water level was maintained approximately 15 ft. below grade for the 3-month duration of the dewatering system operation.


The application of our knowledge in deep well construction and aquifer modeling is unique and provided Griffin the ability to use an alternate to the wellpoints typically utilized in South Florida. During installation of the East Tower and Valet Tunnel, our experts used pump test data to model the anticipated impact of the dewatering system. This data was used to modify the number of wells, spacing, and layout to ensure that we would accomplish the desired drawdown. 

During the project the entire site had to shut down as Hurricane Irma made landfall in South Florida. Griffin worked with the trades on-site to safely flood all excavations (to prevent damage to buoyant foundations) during dewatering system shutdown. Griffin was also among the first trades back on-site working to unwater all excavations and restart the dewatering systems to minimize the impact to the construction schedule. 

Griffin provided dedicated operations and maintenance personnel to keep the multiple systems operational during the complex construction sequence. Griffin coordinated with the prime contractor and other trades on-site to modify, relocate, and adjust equipment layouts to allow construction to progress with-out interruption.