31 23 19 - Dewatering.pdf

31 23 19 - DEWATERING

Herbert, Rowland & Grubic, Inc. 31 23 19 - 1 000598.0465

SECTION 31 23 19 - DEWATERING

PART 1 - GENERAL

1.1 SUMMARY

A. Section Includes:

1. Dewatering system.

2. Surface water control system.

3. System operation and maintenance.

4. Water disposal.

B. Related Sections:

1. Section 31 05 16 - Aggregates for Earthwork: Filter sand.

2. Section 31 23 16 - Excavation: Excavation for structures below ground water table.

3. Section 31 23 16.13 - Trenching: Trenching for utilities below ground water table.

4. Section 31 25 00 - Erosion and Sedimentation Controls: Surface water runoff control.

1.2 REFERENCES

A. ASTM International:

1. ASTM C33 - Standard Specification for Concrete Aggregates.

1.3 DEFINITIONS

A. Dewatering includes the following:

1. Lowering of ground water table and intercepting horizontal water seepage to prevent ground water from entering excavations and trenches.

2. Reducing piezometric pressure within strata to prevent failure or heaving of excavations and trenches.

3. Disposing of removed water.

B. Surface Water Control: Removal of surface water within open excavations.

1.4 SYSTEM DESCRIPTION

A. Provide dewatering and surface water control systems, at the Contractor’s option and cost, to permit Work to be completed on dry and stable subgrade.

1.5 PERFORMANCE REQUIREMENTS

A. Design dewatering systems to:

1. Lower water table within areas of excavation to permit Work to be completed on dry and stable subgrade.

2. Relieve hydrostatic pressures in confined water bearing strata below excavation to eliminate risk of uplift or other instability of excavation.

Herbert, Rowland & Grubic, Inc. 31 23 19 - 2 000598.0465

3. Prevent damage to adjacent properties, buildings, structures, utilities, and facilities from construction operations.

4. Prevent loss of fines, quick condition, or softening of foundation subgrade.

5. Maintain stability of sides and bottoms of excavations and trenches.

B. Design surface water control systems to:

1. Collect and remove surface water and seepage entering excavation.

1.6 SUBMITTALS

A. Section 01 33 00 - Submittal Procedures: Requirements for submittals.

B. Product Data: Submit data for each of the following:

1. Dewatering Pumps: Indicate sizes, capacities, priming method, characteristics.

2. Pumping equipment for control of surface water within excavation.

C. Field Reports: Test and monitoring reports as specified in Field Quality Control article.

1.7 QUALITY ASSURANCE

A. Comply with authorities having jurisdiction for the following:

1. Water discharge and disposal from pumping operations.

B. Obtain National Pollutant Discharge Elimination System (NPDES) permit (as necessary), for storm water discharge from construction sites.

1.8 COORDINATION

A. Coordinate work to permit the following construction operations to be completed on dry stable substrate.

1. Excavation for structures specified in Section 31 23 16.

2. Trenching for utilities specified in Section 31 23 16.13.

PART 2 - PRODUCTS

2.1 DEWATERING EQUIPMENT

A. Select dewatering equipment to meet specified performance requirements.

2.2 ACCESSORIES

A. Valves and Fittings: Furnish valves and fittings to isolate each well from header pipe and to prevent loss of pump prime.

PART 3 - EXECUTION

3.1 EXAMINATION

A. Section 01 73 00 - Execution Requirements: Verification of existing conditions before starting work.

Herbert, Rowland & Grubic, Inc. 31 23 19 - 3 000598.0465

B. Notify the PA One Call System not less than three working days before performing Work.

1. Request underground utilities to be located and marked within and surrounding construction areas.

3.2 PREPARATION

A. Protect existing adjacent buildings, structures, and improvements from damage caused by dewatering operations.

3.3 DEWATERING SYSTEM

A. Install dewatering system in accordance with shop drawings.

B. Locate system components to allow continuous dewatering operations without interfering with installation of permanent Work and existing public rights-of-way, sidewalks, and adjacent buildings, structures, and improvements.

3.4 SURFACE WATER CONTROL SYSTEM

A. Provide ditches, berms, and other devices to divert and drain surface water from excavation area as specified in Section 31 25 00 – Erosion and Sedimentation Controls.

B. Divert surface water and seepage water within excavation areas into sumps and pump water into settling basins in accordance with requirements of agencies having jurisdiction.

C. Control and remove unanticipated water seepage into excavation.

3.5 SYSTEM OPERATION AND MAINTENANCE

A. Operate dewatering system continuously until backfill is minimum 2 feet above normal ground water table elevation.

B. When dewatering system cannot control water within excavation, notify Engineer and stop excavation work.

1. Supplement or modify dewatering system and provide other remedial measures to control water within excavation.

2. Demonstrate dewatering system operation complies with performance requirements before resuming excavation operations.

C. Modify dewatering and surface water control systems when operation causes or threatens to cause damage to new construction, existing site improvements, adjacent property, or adjacent water wells.

D. Correct unanticipated pressure conditions affecting dewatering system performance.

E. Do not discontinue dewatering operations without Engineer's approval.

Herbert, Rowland & Grubic, Inc. 31 23 19 - 4 000598.0465

3.6 WATER DISPOSAL

A. Prior to dewatering, evaluate site conditions. Evaluate flow path to minimize erosion and the transport of sediment to storm drains and receiving waters.

B. Discharge water into areas that are well vegetated and stable. Pollutants and sediments must be removed prior to discharging to a storm drain, waterbody, or wetland.

C. Dispose of water removed by dewatering in a manner that does not endanger public health, property, and portions of the work under construction or completed. Dispose of water in a manner that avoids inconvenience to others. Provide sumps, sedimentation tanks, and other flow control devices as required.

3.7 SYSTEM REMOVAL

A. Remove dewatering and surface water control systems after dewatering operations are discontinued.

B. Repair damage caused by dewatering and surface water control systems or resulting from failure of systems to protect property.

END OF SECTION