Water Treatment Bypass
Process
The Converted Advanced Wastewater Treatment Facility, which
operates 24/7, is the cornerstone of Fernald’s Aquifer Restoration
Project (8097D-162).
Introduction
The following section outlines the U.S. Environmental Protection
Agency (EPA) approved process for discharging storm water from
Fernald’s retention basins to the Great Miami River during periods
of heavy precipitation. The section includes a review of cleanup
standards for the treatment and discharge of Fernald’s water
streams, a summary of water treatment bypass days and Fernald’s
compliance to date, along with 2003-2006 bypass data.
Cleanup Standards
The 1996 Operable Unit 5 (OU5) Record of
Decision (ROD) established specific cleanup standards that
govern the remediation of contaminated portions of the Great Miami
Aquifer and the treatment and discharge of wastewater, storm water and
groundwater from the Fernald site. The standards for uranium, the
primary contaminant at the site, are summarized below:
- Total uranium concentration in the Great Miami Aquifer (a
potential drinking water source) should not exceed the maximum
federal drinking water standard established by EPA. The current
standard is 30 parts per billion (ppb). In 1996, DOE sponsored the
installation of a public water supply in the affected areas of the
aquifer so the groundwater would not be used as a drinking water
source in those areas.
- The 30 ppb drinking water standard is also used as a
performance-based discharge limit for controlling the Fernald site’s
wastewater discharge to the Great Miami River. In this application
the 30 ppb performance-based discharge limit is based on a monthly
average concentration.
- Maximum annual mass uranium discharge to the Great Miami River
should also not exceed 600 pounds per year. Both the 600 pounds per
year and 30 ppb performance based discharge limits were established
through the OU5 ROD process.
- Total uranium concentration in the blended discharge to the
Great Miami River should not exceed the
surface
water final remediation level of 530 ppb outside the mixing zone
(the portion of the river where Fernald effluent is completely mixed
with the river water). This standard is considered protective of
human health under the following conservative scenarios: 1.
Consumer of Meat and Milk, derived from cattle subsisting on
river water with a uranium concentration of 530 ppb and eating feed
crops that were irrigated with water containing 530 ppb uranium; and
2. Recreational User, based on one who swims in the river and
occasionally ingests some of the river water. Because the river is
not a recognized source of drinking water, a drinking water scenario
was not adopted.
Two common measurements Fernald uses to evaluate cleanup progress
in the Aquifer Restoration and Wastewater
Project are parts per billion and gallons per
minute. "Parts per billion" measures the concentration of a
constituent, such as uranium, relative to the media in which it is
present, in this case water. One ppb is comparable to 1 cent in $10
million. The rate at which water is processed through Fernald’s
wastewater treatment systems is usually measured in "gallons per
minute" (gpm). At a rate of 694 gpm over a 24-hour period, Fernald can
treat 1 million gallons of water per day, enough water to fill a pool
the size of a football field 2.8 feet deep.
Treatment Bypasses
There are two types of bypass days at the Fernald site: storm water
bypass days and treatment plant maintenance bypass days. During all
treatment bypass days, Fernald must track the uranium mass in the
blended discharge to ensure compliance with the 600 pound per year
mass-based limit, but is not required to include the concentrations in
the monthly average to demonstrate compliance with the 30 ppb limit.
Uranium concentrations must not exceed the surface water final
remediation level of 530 ppb.
Storm Water Bypasses
In the late 1980s, Fernald constructed two storm water retention
basins with a combined 10-million gallon capacity to collect
uranium-contaminated storm water runoff from the former production
area. As the basins fill, Fernald pumps the storm water at a rate of
up to 800 gpm to the site’s wastewater treatment facilities, where the
water is processed so the total uranium concentration and mass in the
blended effluent discharged to the Great Miami River does not exceed
the discharge limits noted above.
The site’s wastewater treatment facilities treat storm water until
the storm water retention basins are at a low level to assure storage
capacity is available for the next rain event. The facilities
typically treat over 1 million gallons per day when storm water is
available, then switch to groundwater treatment when the basins are
low.
During periods of heavy precipitation, the Department of Energy
(DOE) and the EPA agreed to allow the direct discharge of storm water
from the retention basins to the Great Miami River for up to 10 days
per year to help prevent the basins from overflowing into a drainage
channel that is in direct contact with the underlying aquifer. The
regulatory agreement to bypass the treatment process when quantities
of storm water threaten to exceed retention and treatment capacities
is established in the OU5 ROD and detailed in the Operations and
Maintenance Master Plan for the Aquifer Restoration and Wastewater
Project (OMMP).
The approved process to account for storm water bypass days
specifies that a bypass day occurs when Fernald’s wastewater treatment
systems are bypassed for over 12 hours per day. In this event, Fernald
must count this day as one of the 10 allowed bypass days (per year).
Bypassing that occurs less than 12 hours per day is called a partial
bypass day. If Fernald exceeds the 30 ppb monthly average uranium
concentration, then it must count partial bypass days that occurred
during the month against the 10-day bypass allotment until the monthly
average concentration is below 30 ppb. If Fernald has not exceeded the
monthly average, then it does not have to count the partial bypass
day.
Treatment Plant Maintenance Bypasses
The OU5 ROD allows relief from the discharge limits to accommodate
scheduled treatment plant maintenance activities that involve the
temporary shut down of treatment facilities or extraction and
reinjection wells. In advance of planned maintenance periods, Fernald
must obtain EPA’s approval of the maintenance action and request that
uranium concentrations in the discharge not be considered in the
monthly average to demonstrate compliance with the 30 ppb total
uranium limit. Fernald makes every effort to prevent storm water
bypass during treatment plant shutdowns for maintenance, including
scheduling maintenance shutdowns when dry weather is expected.
Compliance Summary
The background uranium level in the Great Miami River upstream of
the Fernald site is 1 ppb. Background level refers to concentrations
of substances found naturally in the environment. Based on historic
data, Fernald’s discharge has the potential to increase the uranium
level in the river by approximately 4 to 5 ppb, depending on the
river’s level.
Fernald has been in compliance with the 600 pound annual uranium
limit for site discharges to the river since the OU5 ROD was finalized
in 1996. Since January 1998, when Fernald’s average discharge limit
was 20 ppb (the proposed federal drinking water standard), the site’s
monthly average discharges have been in compliance with the EPA
federal drinking water standard, except during four months. Two months
were due to storm water bypasses and two months were due to treatment
plant upsets. The highest level was 26.1 ppb.
In November 2000, EPA established the final federal drinking water
standard of 30 ppb, a level that was determined to be protective of
human health and the environment. With EPA’s approval, DOE adopted the
30 ppb uranium drinking water standard as the performance-based
discharge limit and the aquifer cleanup level in December 2001. This
slightly higher discharge limit has allowed Fernald to accelerate
cleanup by reducing the quantity of water which requires treatment,
thereby permitting higher pumping rates from the aquifer. Fernald has
not exceeded the 30 ppb discharge standard.
Storm water and treatment plant maintenance bypass data since
calendar year 2003 is summarized in the links below. For each bypass day, total
uranium concentrations discharged to the Great Miami River did not
exceed the EPA-approved surface water final remediation level (530
ppb) to protect human health and the environment.
2003
Storm Water Bypass Evaluation Chart
2003 Maintenance Bypass Evaluation
Chart
2004 Bypasses - NONE
2005
Storm Water Bypass Evaluation Chart
2005 Maintenance Bypass - NONE
2006
Storm Water Bypass Evaluation Chart 2006
Maintenance Bypass - None to date
For More Information
For specific questions about this project contact Gary
Stegner,
Ohio Field Office, at (513) 246-0074,
e-mail:
gary.stegner@ohio.doe.gov.
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