Safe Operating Procedure
(Revised 6/15)
DEWATERING
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Introduction
Certain provisions of the Clean Water Act and related federal, state, and local
regulations and ordinances are intended to protect the quality of surface waters (e.g.,
lakes, streams, rivers, etc.) by regulating certain activities having the potential to
discharge pollutants.
Dewatering has the potential to introduce contaminants into surface waters. Potential
contaminants include: petroleum hydrocarbons, total suspended solids from sediment
discharges, metals, organics and high or low pH based on soil and groundwater
characteristics. Therefore, dewatering activities are subject to authorization by permit
and compliance with permit conditions.
Dewatering Activities Conducted by Contractors:
If construction excavation dewatering of groundwater or groundwater mixed with
stormwater is conducted by a contractor, the contractor is responsible for attaining
proper permit authorization and complying with the terms of the permit. De-watering of
construction excavations containing groundwater or groundwater mixed with stormwater
must be authorized by NDEQ through one of the following permits:
1. NDEQ has established a General NPDES Permit for Dewatering (NEG671000),
which covers both groundwater and groundwater mixed with stormwater from
dewatering on construction sites, foundation drains, utility vaults, or wells. This
general permit can be found on NDEQ’s web site.
2. Coverage under NEG671000 is not necessary if a site is covered by a General
NPDES Permit Authorizing Storm Water Discharges Associated with
Construction Sites (NPDES #NER110000) so long as specific Best Management
Practices (BMPs) related to dewatering have been incorporated into the site’s
Stormwater Pollution Prevention Plan (SWPPP). See EHS SOP, Construction
Site NPDES Permits.
Coverage under a General NPDES Permit for Dewatering (NEG671000) is not
necessary for dewatering of only stormwater on construction sites less than an acre.
Discharges are authorized under UNLs Small Municipal Stormwater System (SMS4)
permit. The water must be void of color, turbidity, odors, surface sheens, films, or other
unusual condition (e.g., off-gassing, foaming, etc.) otherwise alternative disposal
measures must be in place. For sites greater than one acre, dewatering of stormwater,
(Created 5/15)
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groundwater, or groundwater mixed with stormwater must be in accordance with the
site’s Stormwater Pollution Prevention Plan (SWPPP).
Dewatering Activities Conducted by UNL Employees:
If construction excavation dewatering of groundwater or groundwater mixed with
stormwater is conducted by a UNL employee on UNL property, then EHS is responsible
to obtain coverage under NDEQ’s General NPDES Permit for Dewatering
(NDEG671000), by submitting to NDEQ a Notice of Intent (NOI). UNL employees
intending to engage in dewatering must contact EHS before initiating dewatering
actions, and implementing appropriate Best Management Practices (BMPs) during the
dewatering activity. EHS will advise on the appropriate BMP selection based on sitespecific conditions. Possible BMPs include the following:
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Sediment Bags: Direct the discharge flow through a sediment bag. This allows
sediments to settle prior to discharging into surface waters.
Flocculants: Disperse flocculant (see manufacturers recommendation on dose)
over the excavation/utility vault that needs to be dewatered. Allow time for
flocculant to bond to clay particles in soil. This will result in lower suspended
solids. Carefully start pump and discharge.
Vegetative Buffer/Land Application: Reuse water (i.e., for watering plants, or
dust control) or dewater to a vegetative buffer (grassy swale), provided the
following conditions are met:
o Land application shall not be conducted when the ground is frozen or
saturated.
o Land application sites shall have a slope of 12% or less.
o Land application shall not occur on sites where the water table is less than
4 feet from the surface.
o The total hydraulic application rate shall not exceed 2 inches per acre
(54,304 gallons) per week.
o Land application sites shall be free of perennial or intermittent streams,
ponds, lakes, or wetlands.
o Land application is not allowed on crops that are intended for distribution
in their raw form for direct human consumption (e.g., fresh produce).
o Land application must cease immediately if any adverse impacts to animal
or plant life is discovered or if any film, foam, color, or noxious odors
occur, of if erosion, channelization, ponding, or surface runoff occurs.
Drum: Dewatering into a 55-gallon drum. Allow sediments to settle prior to
discharging. This is feasible when dewatering small volumes of water.
Discharge Point: Ensure a BMP is utilized to address for concentrated flow.
Force from discharging large amounts of water can itself result in erosion at the
discharge point.
Coverage under NDEQ’s General Dewatering Permit also requires sampling. EHS will
collect the necessary samples or advise on appropriate sample collection based on sitespecific conditions (e.g., including physical characteristics examination, total suspended
solids, pH, flow, petroleum hydrocarbons, etc.). Following sampling, EHS is responsible
(Created 5/15)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
to file Discharge Monitoring Reports, as necessary. Additional information on
requirements associated with NDEQ’s General Dewatering Permit can be found in
Attachment 1.
Foundation Drains, Vaults, Tunnels
Dewatering of uncontaminated accumulated storm and ground water from foundation
drains, and utility vaults and tunnels conducted by UNL employees is covered under
UNL’s Small Municipal Stormwater System (SMS4) permit rather than NDEQ’s General
Dewatering permit as an allowable non-stormwater discharge (per NDEQ
correspondence 5/16/12). If an illicit discharge is detected, sampling will be conducted
by EHS and corrective actions will be implemented.
Stormwater Dewatering
At times, it may be necessary to remove flood or accumulated stormwater from areas
on campus. There are three options: 1) direct the flow to a sanitary sewer; 2) direct the
flow towards vegetation for land application wherein no water discharges to the storm
drain; 3) direct the flow to the storm drain under the authority of UNL’s SMS4 permit. If
discharged directly to the storm drain, the water must be void of color, turbidity, odors,
surface sheens, films, or other unusual condition (e.g., off-gassing, foaming, etc.). No
sampling is required for this type of dewatering, and the PCE does not need to be
recorded. However, if the presence of pollutants are detected, water may not discharge
to storm drain and alternative actions must be taken.
(Created 5/15)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
Attachment 1
NEG671000 General Dewatering Permit
Notice of Intent (NOI). If dewatering under NDEQ’s General Dewatering Permit, a NOI
must be submitted to NDEQ. However the NOI can be submitted after dewatering
activities have been initiated. The NOI form is found in Attachment 1 of the General
NPDES Dewatering Permit. The NOI requires the permittee to determine:
• Whether the receiving water body is a State Resource Water (listed in Appendix B
of the permit; note that discharges to a State Resource Water require prior
approval from NDEQ) or listed lake or impounded water (Title 117, Chapter 6).
On City and East Campuses these are not likely.
• Whether there is likely impact to historic sites by consultation with Nebraska
Historical Society. Again, on City and East Campuses this is unlikely. See
http://www.nebraskahistory.org/histpres/nebraska/index.shtml for a map of
historical places.
• Whether there is likely impact to threatened or endangered species or their habitat
by Consultation with Nebraska Game and Parks. On an annual basis, EHS
obtains a blanket determination for City, East, and Innovation Campuses for this
requirement.
http://outdoornebraska.ne.gov/wildlife/programs/nongame/consultation.asp
Sampling and Discharge Monitoring Reports (DMR). The General Dewatering
permit requires sampling during dewatering activities. Sampling results must be
reported to NDEQ on a DMR and submitted quarterly. The DMR form provided as
Attachment 3 to the General Permit must be used. The DMR must be accompanied by
a Physical Characteristic Examination (PCE) Form (Attachment 4 to the General
Permit). NDEQ’s General Permit specifies monitoring parameters, frequency of
sampling, and type of sample. Sampling parameters include PCE, flow, petroleum
hydrocarbons (if a sheen is present), total suspended solids, and pH. NDEQ may also
require metals and organics, but this is determined on a case-by-case basis (for ongoing discharges). Sampling must occur before the discharge mixes with or reaches a
water of the state (generally at the point where it enters the storm sewer system).
• Sampling Requirements;
o Samples are to be delivered to the NE State Laboratory located at 3630
South 14th Street- 402-472-3935. It is advised to contact the lab prior to
submittal of the samples to ensure personnel are available.
o Sample requirements for lab; this includes holding time, container type
and sample volume requirements:
o pH: 15 minutes, glass/plastic, 100mL.
o TSS: 7 days, glass/plastic, 1 liter.
o Petroleum Hydrocarbons: 7 days, Glass with Teflon-lined cap,
50mL, cool to 4 C.
o Metals and Organics: this is determined by NDEQs requested
analysis.
o Chain of Custody Form: accurately complete COC form and file with
analytical results.
(Created 5/15)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
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Non-Compliance Report (NCR). This is required if the sampling results are not
within permit requirements. NCR is also used when a discharge occurs where a
sample was not taken. EHS is responsible to file NCR reports with NDEQ. NDEQ
must be called within 24-hours of the non-compliance action and a written NCR
submitted within 5 (business) days of the event. Attachment 5 of NDEQ’s General
Permit contains a NCR form.
Notice of Termination: There is no termination form. The permit is discontinued
by requesting termination in the DMR or cover letter to the DMR. Written notice of
termination must be provided to NDEQ within 30 days after discontinuing
dewatering activities.
(Created 5/15)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu