Reverse Osmosis Treatment Facility
Colorado Discharge Permit
Questions and Answers
TOPIC PAGE
Background . . . . . . . . . . . . . . . . 1
Treatment and Discharge Process . . . . . . . . 2
Colorado Ground Water Discharge Permit . . . . . 3
Beebe Draw Alluvial Aquifer & Notes . . . . . . . 4
BACKGROUND
What is ECCV?
The East Cherry Creek Valley Water and Sanitation District (ECCV) provides water and sewer service to approximately 50,000 people in the eastern portions of the City of Centennial and unincorporated Arapahoe County. ECCV is a Colorado Special District governed by Colorado Revised Statute Title 32 and has a Board of Directors that is elected by the registered voters of the District.
What is ECCV’s Northern Project?
The Northern Project is a multi-phase project that brings renewable water to ECCV. The initial phase of the project was completed in 2006 and included the purchase of South Platte River water rights from United Water and Sanitation District and the construction of a 31-mile underground pipeline, storage tanks and two pumping stations to carry renewable water to the District from the Beebe Draw near Barr Lake in Adams County. ECCV is now involved in the second phase of the Project, which includes the purchase of additional water rights and the design, permitting and construction of a reverse osmosis water treatment facility near the Beebe Draw.
Why does ECCV need this water?
The Northern Project provides a renewable surface water source that diversifies the resources of ECCV's system and reduces the District’s dependency on non-renewable groundwater. The majority of ECCV’s water comes from limited-supply aquifers in the Denver Basin—a finite resource that will be depleted over time and become much more expensive to draw in the future when an increasing number of wells are needed to provide the same amount of flow. Northern Project water is needed to provide a reliable water supply for ECCV's customers into the future.
How is ECCV acquiring the water for its Northern Project?
The water rights purchase consists of a three-way arrangement between ECCV, Farmers Reservoir and Irrigation Company (FRICO) and the United Water and Sanitation District (United). The initial agreement included the delivery of about 3,000 acre-feet of water per year from United. The second phase of the water rights acquisition involved the purchase of about 3,000 acre-feet of water from shareholders in FRICO and other agricultural ditch companies. The FRICO agricultural shareholders unanimously approved this concept in November 2002, and reaffirmed this particular project involving ECCV in November 2003.
What is FRICO?
The Farmers Reservoir and Irrigation Company (FRICO) is a mutual ditch company based in Brighton, Colorado, formed in the early 1900’s to provide Front Range farmers with adequate water supplies. The company is governed by a seven-member board of directors elected by its shareholders. FRICO’s system includes five divisions: Barr, with rights to portions of the South Platte River; Milton, also with rights to the South Platte; Marshall, with rights to portions of South Boulder Creek; and Standley, with rights to Clear Creek. The system also includes a municipal division, and has a long history of supplying water for municipal purposes through cooperative agreements for water delivery with the cities of Westminster, Thornton, Northglenn, Louisville, Lafayette, Brighton, Lochbuie and the South Adams County Water & Sanitation District.
TREATMENT AND DISCHARGE PROCESS
What is the ECCV reverse osmosis treatment facility?
It is a facility planned near Brighton as part of ECCV’s Northern Project that will treat water from groundwater wells in the Beebe Draw alluvial aquifer to the northeast of the Barr Lake area for drinking water, which would serve the District’s nearly 50,000 customers. The treatment system has been designed to include reverse osmosis (RO) membranes to efficiently remove natural minerals, and disinfection using chlorination and UV treatment.
What will the treatment process remove from the groundwater?
The treatment process will filter out minerals and other compounds (such as nitrate, sodium, sulfate, chloride and fluorides) that exist naturally in the groundwater in this area. The native groundwater pumped to the treatment facility from the Beebe Draw aquifer has an existing concentration of approximately 700 milligrams per liter (mg/L) of total dissolved solids (TDS).
What is RO return flow?
While water treatment technology has come a long way, it still cannot capture 100% of the dissolved minerals in the Beebe Draw water. ECCV expects that approximately 85% of the water treated will be captured for drinking water use. The remaining 15% of the water after the RO treatment will remain as RO return flow. This water must be returned to the environment in compliance with permit requirements or further treated to be used beneficially.
What does ECCV propose to do with the RO return flow?
In its permit application, the District has proposed using a pipeline to convey the RO return flow approximately four miles north from the treatment facility to the Bowles Seep Ditch. There, the District would blend the return flow with surface water released from Barr Lake into the Bowles Seep Ditch in the Farmers Reservoir and Irrigation Company (FRICO) ditch system. ECCV will blend the RO return flow to meet domestic and agricultural water quality standards for native groundwater in the area. The blended water, anticipated to have approximately 950 mg/L TDS, would then be released from the blending facility into the Bowles Seep Ditch.
Will the RO return flow released to the Bowles Seep Ditch reach a river?
No. The Bowles Seep Ditch works as a natural infiltration ditch, with water seeping into the Beebe Draw alluvial aquifer 60 to 80 feet below, until eventually the Ditch runs dry. This process is known as “recharging” the aquifer. Up to 5 cubic feet per second (cfs) of water can naturally percolate into the aquifer. To further enhance this “recharge”, FRICO has created recharge ponds that would collect the blended water in the Ditch and provide additional area to filter into the alluvial aquifer.
How much RO return flow will the facility produce?
Within the permit, the treatment facility will be targeted to produce approximately 15 cfs of treated water daily at maximum capacity. This would result in a maximum 1.5 cfs of return flow per day being produced and blended in the Bowles Seep Ditch with water released from Barr Lake. ECCV has a current contract with FRICO that limits ECCV’s return flow into the Bowles Seep Ditch to a maximum of 960 acre-feet (AF) per year, as long as ECCV can maintain the blending of its RO return flow with Barr Lake/Bowles Seep Ditch water to meet the permit guidelines for water quality.
How much augmentation water will be needed to blend with the RO return flow?
In order to blend the RO return flow to a mineral concentration that meets the standard for the surrounding native ground water, the blending process is estimated to require approximately 7 parts of water released from Barr Lake for every 1 part of return flow. That would mean that approximately 10 cfs of water released from Barr Lake into the Bowles Seep Ditch would be blended with 1.5 cfs of return flow, if the treatment facility was operating at 100% capacity.
COLORADO GROUND WATER DISCHARGE PERMIT
Why is a discharge permit required?
The Water Quality Control Division (Division) at the Colorado Department of Public Health and Environment (CDPHE) requires permits for discharges to groundwater from wastewater treatment systems, in order to protect water quality and the use of the groundwater for human, livestock and/or agricultural use. While ECCV’s RO facility is not a wastewater facility, but rather a facility to treat groundwater for drinking water purposes, the same permit requirements for a discharge of return flow water still apply.
How does the discharge permit protect water quality?
The permit is drafted to protect ground water quality in the Beebe Draw alluvial aquifer for domestic and agricultural uses. The permit guidelines enforce health-based standards for drinking water quality and use standards for agricultural water use. To view the draft permit, fact sheet and water quality assessment, please visit: http://www.cdphe.state.co.us/wq/permitsunit/publicnotice/publiccomment.html
and scroll down to CO-0047571.
- ECCV will be required to adhere to the state’s stringent standards for ground water quality, as defined in the Division’s Regulations No. 41, 61 and 62, which are protective of human health for use as drinking water.
- In order to ensure the protection of crops irrigated by groundwater from the alluvial aquifer, the State will require that that discharges to the Bowles Seep Ditch not exceed 1,200 miligrams/liter (mg/L) of total dissolved solids, which is the standard for ground water discharges to aquifers used for agriculture. The native groundwater in that area currently ranges from 600 Mg/l TDS to 2,900 mg/l TDS. ECCV intends to operate the treatment facility and blending with Bowles Seep Ditch water so the blended concentration is approximately 950 mg/L TDS, to remain well below this permit limit.
- ECCV will also be required to meet the Division’s concentration limits for three key parameters to protect agricultural use and crop yields—sodium, bicarbonate and electrical conductivity.
Within the permit, who would monitor water quality beyond the discharge point?
ECCV would monitor the concentrations of selected parameters at the treatment facility prior to blending it with Bowles Seep Ditch water, in order to determine how much water released from Barr Lake may be needed for blending. ECCV would also be required to monitor groundwater quality at four “points of compliance” using monitoring wells adjacent to the Bowles Seep Ditch, including one upstream of the RO return flow discharge and three downstream, and submit the data in a monthly report to the Division, along with giving proactive notice of any non-compliance.
Since May 2008, ECCV has also been gathering baseline data with existing monitoring wells for groundwater and surface water quality and hydrology, to support its permit application. If the permit is granted, ECCV will continue to collect baseline data at existing monitoring wells until the treatment facility is operational, anticipated in 2010.
What are the penalties for a ground water discharge permit violation?
Should the discharge exceed the limits for any parameters, ECCV would face monetary penalties and the order to “cease and desist” the discharge.
Is ECCV working to improve the efficiency of its water treatment to eliminate RO return flow?
Yes. ECCV has teamed up with the Colorado Water Conservation Board (CWCB) and the South Metro Water Supply Authority (SMWSA) to conduct a pilot project that is testing “zero liquid discharge” technologies. The pilot project is evaluating systems that capture the return flow from RO and provide further treatment to maximize the output of clean water and further concentrate the minerals in the return flow. The pilot project also is evaluating methods for acceptable disposal of the concentrated minerals. The results from the study, due out next year, may be applied at a larger scale to future stages of the ECCV treatment process and to benefit other water providers.
BEEBE DRAW ALLUVIAL AQUIFER
What is the Beebe Draw Aquifer?
The Beebe Draw Aquifer is a shallow, alluvial aquifer system filled with sand and gravels. Alluvial aquifers are hydraulically connected to stream systems. The Beebe Draw Aquifer is a pre-historic channel of the South Platte River.
Are there domestic wells in the Beebe Draw aquifer?
While there remain some domestic wells in the Beebe Draw aquifer, the existing groundwater in this alluvial aquifer does not meet secondary drinking water standards for TDS and in some locations does not meet primary drinking water standards for nitrates and other compounds. Many domestic wells in the area draw water from the local bedrock aquifers, which are considerably deeper than the Beebe Draw aquifer, and are more reliable and of sufficient quality for drinking water supply.
Will the Beebe Draw aquifer become depleted over time by the Northern Project?
No. ECCV is purchasing renewable surface water rights as part of this project. These rights will be used to make sure there is always water in the Beebe Draw, which is being used as a storage vessel for the Project.
What is the source of water to be blended with the RO return flow?
ECCV is pursuing water rights that will require the District to replace any water that is drawn by wells from the Beebe Draw for treatment. ECCV will replace a portion of these depletions in the alluvial aquifer by releasing its blended RO return flow into the Bowles Seep Ditch and recharge ponds, which naturally filter into the alluvium and recharge the aquifer. In addition, FRICO will also be recharging water to the Beebe Draw via the Bowles Seep Ditch and recharge ponds using existing and pending water rights.
Will ECCV discharge to the Bowles Seep Ditch in the winter months when the flow is low or frozen?
Like most water providers, ECCV sees a drop in customers’ water demand in the winter months (October to March). The RO treatment process will not be necessary in the winter months, because the District will blend a smaller volume of Beebe Draw ground water after disinfection with other deep aquifer groundwater supplies to meet its reduced demand. Therefore, it is not anticipated that return flow will be created or discharged in the winter season.
Will the RO return flow contain any additional compounds that would be discharged to the aquifer?
A minor amount of anti-scalant chemical is added during the RO process. This chemical is acceptable for drinking water. Other than this, the effluent will only contain minerals and other compounds that exist naturally in the alluvial aquifer that are concentrated during reverse osmosis (RO) treatment and then blended with Bowles Seep Ditch water. Any UV and chlorination treatment will only be used on ECCV’s drinking water supply, and not on the RO return flow.
Will the discharge pose any threat to humans, wildlife or livestock?
No. The water discharged to the Bowles Seep Ditch will be blended to a quality that meets ground water standards in the Beebe Draw aquifer for domestic and agricultural use.
NOTES
- Acre Foot (AF): A customary measurement of a volume of needed to cover one acre of surface area to a depth of one foot; equivalent to about 326,000 gallons, or 43,560 cubic feet.
- Cubic Foot Per Second (cfs): A customary measurement of flow rate, equivalent to a volume of one cubic foot flowing every second; equivalent to approximately 2 acre-feet per day or 1.5 million gallons per day
- Milligrams per Liter (mg/L): A measurement of the concentration of a substance in a liquid. It is the approximate equivalent of parts per million.
- Total Dissolved Solids (TDS): The combined content of all inorganic and organic substances in a liquid which are present in a molecular, ionized or micro-granular suspended form; a secondary standard for water quality (with dissolved solids affecting odor and taste).
Click here to review a copy of the ECCV surface water permit to the Bowles Seep
Click here to review a copy of the ECCV deep injection well public notice & permit
