SECTION 208 — DEWATERING 200-63 — DEWATERING
208.01 Description.
This work includes dewatering as necessary in excavations for all demolition and construction requiring dewatering Project wide. To avoid water pollution caused by sediment-laden discharge from excavation sites, additional dewatering may be required during high river flow events. When designing, providing, installing, operating, maintaining, and subsequently removing temporary dewatering systems and temporary dewatering basins , ensure that all erosion, sediment, and pollution prevention controls and devices are in place before the start of excavation when required by the SWPPP/SESC . If contaminated materials are within the dewatering location, the groundwater is assumed to be contaminated. Obtain a DEM RIPDES permit for any discharges of the water to a waterbody or storm drain. SECTION 907 addresses dust control to reduce dust nuisance and hazards.
208.02 Materials.
Dewatering Basins. Provide precast concrete barrier units that conform to SECTION 909. Provide f ilter fabric that conforms to Subsection 206.02.2. Provide filter stone that conforms to Subsection M01.09, Table I , Column V . Provide straw bales and wooden stakes that conform to Subsection 206.02.1. Filter Fabric Retention Basins. Provide fence that conforms to the requirements for Type I Chain Link Fence in SECTION 903 . Provide wooden posts that are 2-in. × 2-in. oak and at least 3 ft in length. Provide filter fabric that conforms to Subsection 206.02. Provide a layer of stone over the bottom of the basin that complies with Subsection M10.03.2 for Modified NSA Class R-4 riprap. Contaminated Groundwater Dewatering Treatment System. The Contractor shall apply for a RIDEM RIPDES RGP.
208.03 Construction Methods.
Install the required erosion and pollution controls before initiating any drainage, roadway, or bridge construction or for the disturbance of any soils. Dewatering.
a.Design. Use a Professional Engineer registered in the State of Rhode Island to perform all designs. Submit the following information: ● The qualifications of the Dewatering Contractor. The Dewatering Contractor shall have experience in installation, operation, and maintenance of dewatering systems including well point systems, contaminated water treatment systems, and sedimentation systems.
Part 200 — Earthwork and Erosion Control August 2025
200-64 SECTION 208 — DEWATERING ● Submit Shop Drawings that identify the proposed types and details of the surface water control. This includes dewatering systems (including well details, well screen openings, and filter pack materials), observation well locations, sedimentation tank to be used, and discharge systems. ● Include the arrangements, sizes, capacities, plan locations, and depths of the proposed systems and a description of the equipment, materials, and procedures for the dewatering system; the standby equipment and power supply; and the strategy for the effluent discharge. ● Provide the design details of the on- site sedimentation control structures and the associated piping, including calculations, supporting technical information, and a schedule for cleaning the sedimentation control structures. ● Provide the design calculations documenting that the dewatering system can handle all seepage into the excavation and will prevent piping or boiling of the excavation subgrade. ● Provide the anticipated peak and average dewatering rates. ● Describe the proposed methods for removing the dewatering system elements. If applicable, describe the details for leaving the dewatering system in place.
b.Design and Performance (General). Meet the following design and performance criteria: ● Select the methods for controlling water inside and outside the work area being dewatered for the dewatering system. ● Modify the dewatering and sedimentation treatment system(s) as required to meet the requirements of the work. ● Maintain the site, construction dewatering equipment, and subsurface drainage to protect the construction work. Maintain site grades to direct surface runoff to collection points, and prevent surface water from running or collecting over prepared subgrades, fill surfaces, or the work area being dewatered. Collect and discharge surface water, seepage, precipitation, groundwater, and other water that enters work areas being dewatered. Do not allow standing water to accumulate in excavations or work areas being dewatered. ● Install observation wells, as approved by the Engineer, to monitor the effectiveness of the dewatering system. ● Dewater to allow installation of temporary excavation support elements without loss of ground or unacceptable ground movements. ● Minimize impacts to water levels outside the site limits during construction. ● Dewater so that all construction and demolition is conducted in-the-dry, which means without standing water or saturated conditions that may interfere with construction.
Part 200 — Earthwork and Erosion Control August 2025
SECTION 208 — DEWATERING 200-65 ● Implement measures to prevent damage to properties, buildings , structures, utilities, etc. ● Provide design calculations demonstrating that the selected dewatering system(s) can accommodate seepage and prevent piping into the excavation. ● Modify the system(s) at no additional cost to the Department if, while in operation, the system causes or threatens to cause damage to properties, buildings , structures, utilities, etc., or otherwise does not perform as required. ● Repair damage to any utility, structure, and/or facility resulting from dewatering activities. ● Control effluent on-site if the on-site discharge of the effluent does not result in erosion and off-site surface runoff. ● Employ adequate back-up equipment, dewatering system components, and power in case of equipment breakdown. Develop emergency procedures for maintaining continuous, uninterrupted dewatering operations.
c.Design and Performance (Dewatering System). Meet t he following design and performance criteria: ● Provide, install, maintain and operate pumps, wells, and related equipment of sufficient capacity to adequately dewater excavations or work areas , until the required construction, installation, and backfilling of underground structures is complete to avoid construction impacts. ● Provide sedimentation basins that accommodate the dewatering flows and that reduce suspended materials in the dewatering effluent. ● Maintain water levels or hydrostatic pressure heads at least 2 ft below excavation to maintain an in-the-dry stable work area and/or subgrade 24 hours per day. ● Prevent loss of fine materials into bedding, piping, boiling up of trench and excavation bottoms, or other disturbances that may cause subsidence or loss of strength of the underlying natural soils. ● Excavate all soils made unsuitable due to inadequate dewatering or disturbance by construction operations, and replace the unsuitable soils with compacted fill. ● If the dewatering procedures result in boiling, loss of fines, ground instability, uncontrolled flow, or other detrimental effects, notify the Engineer of the unsuitable conditions. Modify the operations to correct the problems at no additional cost to the Department. ● Inform the Engineer of any necessary changes in the dewatering system to accommodate field conditions before making any changes.
Part 200 — Earthwork and Erosion Control August 2025
200-66 SECTION 208 — DEWATERING ● Provide access to the dewatering system(s) to facilitate obtaining samples before and after discharge. ● Ensure that the dewatering effluent contains no hazardous materials at concentrations sufficient to cause a sheen or other visual/olfactory evidence of contamination. If these conditions exist, notify the Engineer and discontinue the discharge until the system can be modified. Temporary Dewatering Basins. Dewatering basins form a rectangular concrete barrier enclosure, the bottom and sides of which are lined with filter fabric . The bottom fabric is stabi lized with filter stone . The basin is divided into the required number of 12-ft sections by stone berms approximately 18 in. high.
a.Installation. The following stipulations apply: ● Place the precast concrete barrier units on level or nearly level ground. ● Place filter fabric on the bottom of the area enclosed by the concrete barrier units . If more than one sheet of fabric is required, overlap the adjacent section a minimum of 12 in. to ensure full coverage. Turn up the f ilter fabric along the inside face of the concrete barriers to the top of the barrier, which is folded across the top of the barriers. Maintain the fabric in position with sand bags, end-to-end, along the top of the concrete barrier enclosure. ● Spread a minimum layer of 6 in. of filter stone over the bottom of the basin. Locate the stone berms at 12-ft intervals along the basin length.
b.Removal. Do not remove the dewatering basin until all dewatering operations are complete. Before the removal, however, remove all accumulated sediment within the basin according to SECTION 212 . Seed and mulch the area covered by the basin immediately after the basin is removed. Backfill any voids resulting from dewatering system removal with cement grout, concrete, or other material to prevent potential loss of ground. Filter Fabric Retention Basin. The filter fabric retention basin forms a rectangular enclosure formed by a 2- ft high chain link fence. Both the fence and the bottom of the enclosure are lined with filter fabric that is stabilized by a layer of rock riprap.
a.Installation. The following stipulations apply: ● Place the filter fabric retention basin on stabilized and level ground to prevent erosion by water exiting the basin. ● Dig a 6-in. × 6-in. minimum trench where the basin will be constructed. ● Provide the filter fabric and wire backing that is 3 ft wide (minimum) positioned in the trench and secured to metal posts positioned 4 ft on center (maximum).
Part 200 — Earthwork and Erosion Control August 2025
SECTION 208 — DEWATERING 200-67 ● Drive the metal posts into undisturbed soil next to the trench to a minimum depth of 12 in. ● Place fill material in the trench and compact. ● Provide an installed height of fence that is 2 ft (minimum). ● Spread a minimum layer of 6 in. of filter stone (Modified NSA Class R-4 riprap) evenly over the bottom of the basin.
b.Removal. Remove the filter fabric retention basin according to the dewatering basin requirements in Para. b of Subsection 208.03.2.
208.04 Method of Measurement.
Dewatering is not measured for payment. Dewatering Basins, Filter Fabric Retention Basins, and Contaminated Groundwater Treatment Systems will be measured by each.
208.05 Basis of Payment.
The Department will pay for the completed and accepted quantities at the Contract unit prices as follows. Pay Item Pay Unit Dewatering LS Dewatering Basins EA Filter Fabric Retention Basin EA Contaminated Groundwater Treatment System EA The prices constitute full compensation for all labor, materials, and equipment, including installation, subsequent removal, and restoration of basin areas, and all incidentals required to finish the work, complete and accepted. The cleaning and maintenance of Dewatering Basins, and Filter Fabric Retention Basins, will be paid for under SECTION 212.
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Source: Standard Specifications for Road and Bridge Construction (Blue Book), 2022 (Aug 2025 compilation) Edition. Pages 189–193 of 951. View official source ↗