DWQ-2024-004366

UPDES General Permit for Construction
Dewatering and Hydrostatic Testing (CDHT)
DEWATERING CONTROL PLAN GUIDELINES
The permittee is required to develop and implement a written site-specific Dewatering Control Plan prior to initiating
dewatering. The plan must be maintained and available for inspection on-site, and must include:
1) Evaluation, installation and maintenance of Best Management Practices (BMPs), including but not limited to:
a. Run-on prevention and/or ground water exclusion methods (where low permeability cut-off walls are used
to keep water out of the excavation);
b. Erosion control to prevent surface water/storm water contamination of site (i.e. soil roughening, riprap,
mulching, geotextiles, etc.) Excavated material must be transported and stockpiled in such a manner as to
prevent its erosion returning to the receiving stream;
c. Treatment at dewatering pump intake (i.e., filtering sump, wrapping submersible pump in filter fabric);
d. Sediment Control for dewatering discharge (i.e. constructed settling pond, dewatering bags, fiber rolls,
vegetated buffers, etc.); and
e. Proper use of anionic flocculants and coagulants, if needed (including maintaining MSDSs and following
manufacturers’ recommendations).
2) Measures taken to prevent first flush/initial purge discharges from entering state surface waters. If not possible,
minimizing turbidity and TSS in this initial discharge through use of land application, settling ponds, or other BMPs.
3) Measures taken to prevent spilled or leaking fuels and lubricants from entering the watercourse. If an oil sheen if
observed in the discharge, a grab sample must be taken for analysis and the dewatering discharge must be stopped
until the source of the oil is eliminated.
4) Measured taken to minimize erosion from the discharge through the use of flow dissipation devices such as rip rap,
baffles, or other methods, as necessary. The discharge shall not cause or result in erosion to the area of the discharge
of the surrounding stream banks.
5) Discharge monitoring procedures for the site to ensure that monitoring is effective and must cover all times of
discharge (including weekends and holidays if applicable). The Dewatering Plan must include an identification of
the person(s) responsible, monitoring frequency, any necessary and its maintenance, including calibration materials,
and record-keeping in the daily log. The monitoring procedures must also ensure that both visual monitoring and
sampling is conducted at times representative of operations on-site (the plan must address how the responsible
parties will ensure that monitoring is conducted at times the site has construction activity).
6) BMP inspection procedures in order to prevent breakdowns or failures of the control equipment. The permittee must
include the inspection frequency, person(s) responsible, and extent of the inspections (including erosion prevention,
dewatering operations, dewatering treatment, and discharge quality), and recordkeeping in the daily log. The
permittee must also include names/numbers for off-house notification of responsible personnel in the event of an
emergency.
7) Corrective action protocol, including roles and responsibilities for observing and reporting any failures to the
permittee’s responsible official or their designee, and what site-specific steps may be required to regain compliance.
8) Control Measures to control Erosion, Sediment and Runoff