Attachment_1A_-_CMAFS_NPDES_permit_CO-0034762.pdf

Ref: 8WP-CWW

CERTIFIED MAIL

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION 8

1595 Wynkoop Street Denver, CO 80202-1129

Phone 800-227-8917 www.epa.gov/region8

FEB 1 6 2017

RETURN RECEIPT REQUESTED

Jason Cook Deputy Director, 721 st Civil Engineer Squadron 1 NORAD Road, Suite 4102 Cheyenne Mountain AFS, Colorado 80914-8001

Re: Notice of Permit Finalization NPDES Permit No. C0-0034762

Dear Mr. Cook:

Enclosed is the NP DES Permit No. C0-0034762 (and the statement of bas is and response to comments) for the Cheyenne Mountain Airforce Station. This permit shall become effective upon the date specified unless, within thirty (30) days following the date of your receipt of this permit, a petition is received by the Environmental Appeals Board (EAB) to review any condition of the permit pursuant to the provisions of 40 CFR § 124.19. If you decide to file a petition for review with the EAB, the petition must contain all information required by 40 CFR § 124.19(a) . Additional information about EAB requirements is avai lable at the EAB's web site: http://epa.gov/eab/

A petition submitted through the U. S. Postal Service (except by Express Mail) must be addressed to:

C lerk of the Board U.S. Environmental Protection Agency Environmental Appeals Board 1200 Pennsylvania Avenue, NW Mail Code MC 1103M Wash ington, D.C. 20460-000 I

All documents that you hand-carry in person or that you arrange to have delivered by courier, Express Mai l, or a non-U.S. Postal Service carrier (such as Federal Express), must be delivered to :

Clerk of the Board U.S. Environmental Protection Agency Environmental Appeals Board 1201 Constitution A venue, NW WJC East, Room 3334 Washington, D.C. 20004

If you have any questions regarding monitoring requirements, schedules and pem1it limitations, please direct them to Paul Garrison of my staff at (303) 312-6016.

Enclosure(s)

1. NPDES Discharge Pe1mit

Darcy O'Connor, Assistant Regional Administrator Office of Water Protection

2. Statement of Basis Including Response to Comments cc: Erin Scott, Colorado Department of Health and Environment

Original Recipient:

Jason Cook Deputy Director, 721 st Civil Engineer Squadron 1 NORAD Road, Suite 4102 Cheyem1e Mountain AFS, Colorado 80914-8001

CC:

Erin Scott Colorado Department of Health and the Environment 4300 Cherry Creek Dr.

South Denver, Colorado 80246

BCC:

Electronic Copy to

Bill Kennedy Kennedy.william@epa.gov

Paul Garrison ( iarrison. pauJc ci: cpa. gov

PERMITTEE:

FACILITY:

PERMIT NO.:

RESPONSIBLE OFFICIAL:

FACILITY CONT ACT:

LOCATION:

RECEIVING WATERS

PERMIT TYPE:

STATEMENT OF BASIS

United States Department of the Air Force Cheyenne Mountain Air Force Station C0-0034762 Jason Cook Deputy Director, 721 st Civil Engineer Squadron 721 CES/DD, Cheyenne Mountain AFS 1 NORAD Road, Suite 4102 Cheyenne Mountain AFS, Colorado 80914-8001 719-474-3180 E-mail: Jason.Cook@CheyenneMountain.af.mil Wanda Burns Enviromnental Program Manager for CMAFS 719-474-3620 E-mail: wand~!. burns:i0Js.af.mil Mailing address:

Wanda Burns

721 CES I CEIE

1 NORAD Road, Building 321 Cheyenne Mountain AFS, Colorado 80914

In El Paso County, Colorado, at approximate latitude 38.744722° N and longitude I 04.843333° W Unnamed ephemeral tributaries to Fountain Creek Federal Facility, Permit Renewal, Minor Permit

This Statement of Basis is for the renewal of the National Pollutant Discharge Elimination System (NPDES) Permit for the U.S. Air Force's Cheyenne Mountain Air Force Station (CMAFS). The current Pern1it was issued in 201 I with an effective date of March 1, 2011, and an expiration date of December 3 L 2015. The application for permit renewal was dated June 10, 2015 and received June 24, 2015.

Receipt of the application was acknowledged in a letter of July 14, 2015. A letter dated March 30, 2016, stated that the Permit has been administratively extended.

Background Information:

Item XII, Nature of Business, of Form 1 of the permit renewal application contained the following statement.

Cheyenne Mountain Air Force Station is an Air Force installation, located partially within Cheyenne Mountain itself. The complex was initially constructed to house the North American Defense Command Center (NORAD). The complex cmTently serves as an Alternate Command Center for NORAD, and is operated under the 721 st Mission Support Group, and is a geographically separate unit of the 21st Space Wing, located on Peterson Air Force Base.

NOTE: Peterson Air Force Base is located in the nearby City of Colorado Springs, Colorado, and is approximately 9 miles to the northeast of CMAFS.

Statement of Basis/or 2016 permit renewal- USAF-Cheyenne Mountain AFS C0-0034762 Page 2of19

Although the status of the CMAFS has changed to an Alternate Command Center for NORAD, there is still significant activity within the facility. There have been some minor changes to the piping that caJTies the discharge out of the facility. The location of Outfall OOI was moved a short distance because it was necessary to replace part of the outfall line due to damage caused by a massive mudslide that occurred on September I 2, 20 I 3. The location of Internal Outfall 00 I B was moved closer to the entrance of the North Portal of the underground complex. Neither of these changes affect the quantity or quality of the water being discharged. It was learned in an email from the Permittee (April 4, 2016) that all water from the industrial reservoir is now routed to Pit 48 to Pit 52 then into the oil/water separator and then to the pipeline to the Fo1i Carson sanitary sewer system. Accordingly, Internal Outfall 001 C is no longer needed as a control point and will not be used in the renewal Permit. As will be discussed later, a new Internal Outfall 001 D has been added to the renewal Permit and will ultimately replace Internal Outfall 00 I A as a control point.

It should be noted that much of the material presented in the Background Info1111ation section of this Statement of Basis is from the previous Statement of Basis and is included for information purposes.

NOTE: The Confidential Business Information (CBI) folder of the permit file contains a flow diagram titled "Water Collection and Elimination Schematic, Cheyenne Mountain AS, Colorado," and other diagrams which help in understanding the sources of water and where the water goes. The diagrams were not included in the cuJTent Permit or Statement of Basis because of security concerns by the Air Force.

The CMAFS is located on the slopes of Cheyenne Mountain on the southwest edge of the City of Colorado Springs. The CMAFS complex was initially constructed as the North American Aerospace Defense Command Center (NORAD) and became operational in about 1964. A portion of the complex is located underground in a series of tunnels and chambers that house a self-contained command center.

In addition to various buildings, the underground facilities include a drinking water reservoir, drinking water chlorination system, large diesel powered electric generators, cooling towers, and reservoirs for industrial (cooling) water. Water used in the underground complex normally comes from internal springs and water seepage into the reservoirs and for many years there has been more water than is needed. In addition, water sometimes seeps from the walls and ceilings of the various chambers and tunnels and drains to the floor.

The use of water within the complex includes drinking water, sanitary usage, cooling water for the diesel powered electric generators, and periodic hosing down of the interior rock walls and ceilings of the tunnels and chambers to remove loose rock. The latter is normally done yearly, but can be done more frequently if needed.

The electricity for the underground complex normally is purchased from commercial sources. However, some of the diesel generators are kept on standby status and all are operated periodically to insure their operating capability, for certain practice ale1is, and when electricity is not available from the commercial source(s). When the diesel generators are operated, the cooling water from the generators normally is routed in a closed loop system to heat exchangers and returned to the diesel generators for reuse.

Cooling towers are used to cool the water in the heat exchangers. The water in the cooling tower system is treated with a proprietary system called "Cascade UVOX ultra violet light system."

If the cooling towers cannot be used, the industrial water reservoirs can be used for cooling reservoirs.

When this occurs, the cooling water from the closed loop cooling system is routed to the industrial reservoirs and mixed with the water in the industrial reservoirs. At the same time, water from the

Statement af Basis for 2016 permit renewal - USAF-Cheyenne Mountain AFS C0-0034762 Page 3qf19 industrial reservoirs is pumped into the closed loop cooling system to replace the water routed to the industrial reservoirs. The use of the industrial reservoirs for cooling purposes can occur in emergency situations; when it is necessary to do repairs, maintenance, equipment modifications, etc., that involve the cooling towers, etc.; and during training drills on how to use the industrial reservoirs as cooling reservoirs. According to the Permittee, no chemicals are presently used in the closed loop cooling system. However, there is the potential for metals to be corroded from the cooling system.

The various wastewaters, excess spring water, and drainage from the underground complex at CMAFS are either routed to the sanitary sewer system at nearby F01i Carson via a buried pipeline or discharged under the provisions of a NP DES permit. An exception is that when there is an excess of untreated spring water routed to the drinking water plant storage tanks, the excess flow is diverted to an unnamed tributary of Fountain Creek.

Waters and wastewaters going to the pipeline to the F01i Carson sanitary sewer system include the sanitary wastewaters from the underground complex, cooling tower blowdown, cooling tower basin cleaning wastes, infiltration water from the diesel storage reservoir, overflow from the drinking water reservoir, overflow from the industrial water reservoirs, and water collected in certain floor drains in the underground complex. All of these, with the exception of the sanitary wastewater, are collected in the Main Tunnel Pit 52 and pumped directly to an oil/water separator, which is located outside the underground complex. The effluent from the oil/water separator goes to the pipeline to the Fort Carson sanitary sewer system. The sanitary wastewaters are routed separately to the pipeline. There is a memorandum of understanding (MOU) between CMAFS and Fort Carson concerning the routing of wastewater from CMAFS to Fort Carson.

The current Permit authorizes the discharge from the interior storm drainage system (ISDS) at the CMAFS. After the ISDS leaves the underground complex there are two valves where the flow can be routed to either the oil/water separator via the industrial sewer (and on to the pipeline to the Foti Carson sewer system) or to the discharge line (over-the-hill), which discharges to an urummed tributary to Fountain Creek. The normal operating procedure is to route the flow of the ISDS to the discharge line (and subsequently to surface waters) except when activities and/or conditions within the underground complex have the potential to significantly increase the concentration of pollutants in the· ISDS. When that occurs, the flow is directed to the oil/water separator and on to the pipeline to the F01i Carson sanitary sewer system.

The location of these valves is designated as Internal Outfall 001 B. When the current Permit was issued in 2011, Internal Outfall OOlB was located in a valve box located just to the north of Building P106, which was located where the dtiveway to the North Portal (turu1el) turns off NORAD Road. On September 12, 2013, there were approximately 14 inches of rainfall on Cheyenne Mountain. This resulted in an extensive mudflow which among other things, temporarily blocked the North P01ial (tunnel) to the NORAD facility and affected the discharge line to Outfall 00 I. Starting September 22, 2013 and continuing through August 4, 2015, all flow from the ISDS was directed to the pipeline to the Foti Carson sanitary sewer system. As a result of the mudflow, it was necessary to install a new outfall line and move the control valves. These valves are still designated as Internal Outfall OOIB, but are now located approximately 70 to 80 feet from the p01ial entrance at the north edge of the driveway. The approximate latitude and longitude of the valves are 38.744464° N and 104.846449° W, respectively.

These valves are located at the ground surface at the north edge of the driveway that goes into the North Potial (tunnel). Outfall 001 was moved less than 100 feet to it new location. The approximate latitude and longitude of the new location of Outfall 001 are 38.744862° N and I 04.843419° W, respectively.

Statement of Basis/or 2016 permit renewal - USAF-Cheyenne Mountain AFS C0-0034762 Page 4qf19

The !SOS receives some of the excess spring flow, infiltration collected nnder Building 2000 (not cmTently done), and water from miscellaneous seeps that come out of the stone walls at various places and flow into the ISDS via grates located at numerous points in the complex. This water is relatively clean and can meet permit limitations without treatment. The Permittee is working on separating out more clean water that presently goes to Fort Carson and routing it to the !SOS.

An additional source of water and pollutants that drains to the !SOS comes from the periodic hosing down of the interior rock walls and ceilings of the tunnels and chambers. They are hosed down for safety purposes to remove loose rock. Each area is washed down at approximately yearly intervals or as needed. The water is applied with a hose that is connected to a tank truck and is applied at about normal household tap pressure. The runoff from the washing operations flows to the storm drains in the !SOS.

During the washing operations the road surfaces are also hosed off. Normally a street sweeper is used to keep the interior roads clean. The water from the washing operations has the potential to contain significant quantities of suspended solids, etc. When the washing operations occur, the operating procedure is to direct the flow of the !SOS to the oil/water separator and on to the Fort Carson sanitary sewer system.

Initially, the primary reason for discharging the clean waters directly instead of routing them to Fort Carson was to try to keep to a reasonable minimum the amount of clean water routed to the Fort Carson sanitary sewer system. There is a cost involved in routing water through the sewage treatment plant.

Another factor involves water rights. It is this writer's understanding that the Air Force does not get as much credit for water returned when water from the underground complex is routed to Fo11 Carson as compared to the water being discharged directly to surface waters at CMAFS. Apparently, if too much water is routed to Fort Carson, it might be necessary for the Air Force to provide downstream flow augmentation to meet downstream water rights. An increased emphasis has been placed on complying with water rights since the Supreme Court ruling in favor of the State of Kansas with regards to the Colorado - Kansas Water Compact.

The physical layout of the !SOS and discharge line presents some problems in terms of access for sampling and compliance points. The point where the !SOS enters the discharge line was buried and is located outside of the underground complex. At approximately 7,000 feet elevation, winter temperatures can be very cold at times. The discharge line discharges to the unnamed tributary part way down the slope on the east side of the parking lot at the North P011al. Access to that point can be difficult during dry weather and would be dangerous during inclement weather and/or when there is snow on the ground. Adding a separate pipeline for spring water, etc., within the underground complex would have some advantages, but would be difficult and very expensive due to the granite rock environment.

Primarily for these reasons it was decided to have interior outfalls instead of having the outfall at the final point of discharge to the unnamed tributary.

In the current Permit, a combination of numerical effluent limitations, the requirement to develop and implement a pollution prevention plan (PPP), the prohibition of discharging certain waste streams, and restrictions on the use of the industrial reservoirs for cooling purposes are used to regulate the discharge from the ISDS. Because of the complexity of the system and access problems for monitoring purposes, there was no external Outfall 00 I in the Permit, but there were three internal compliance points in the current Pe1mit.

Internal Outfall 001 A is located at the grate in the !SOS in the main tunnel near the Diesel Maintenance blast door. It includes the grate and the flow meter and sampling tap in the !SOS just upstream of the grate.

Page 5of19

Internal Outfall 00 I B is at the two valves in the pipelines where the flow of the ISDS is either routed to the oil/water separator or routed to the discharge line (over-the-hill). As previously mentioned, the valves were located in a valve box located on the !SOS just to the north of Building PI06, which was located where the driveway to the North Portal (tunnel) turns off NORAD Road. These valves are now located approximately 70 to 80 feet from the portal entrance at the north edge of the driveway. The approximate latitude and longitude of the valves are 38.744464° N and 104.846449° W, respectively. These valves are located at the ground surface at the north edge of the driveway that goes into the North Portal (tunnel).

Internal Outfall OOIC was the discharge from the middle reservoir of the industrial reservoirs. If water were to be drained from the industrial reservoirs to the !SOS, it would come from the middle industrial reservoir and be pumped into the !SOS. In an email dated April 4, 2016, the Pennittee informed this writer that the release of water from the industrial reservoirs is pumped to Pit 48 to Pit 52 to the oil/water separator and the pipeline to the Fort Carson sanitary sewer system. Accordingly 00 IC will not be used as a compliance point in the renewal Permit.

The ctment Permit requires that there be no discharge of sanitary wastes, cooling tower blowdown, wastes from the cleaning of cooling tower basins, water from Pit 48, water from Pit 52, and there shall be no discharge of water from the closed loop cooling system except as the result of the industrial reservoirs being used as cooling reservoirs. The reason for not discharging the sanitary wastes, the cooling tower blowdown, and the wastes from the cleaning of cooling tower basins without treatment is obvious. Waters from pits 48 and 52 have the potential for significant concentrations of pollutants and since there is no treatment of these waters if routed to the !SOS and discharged, these waters should be routed through the oil/water separator and on to the pipeline to the Fort Carson sanitary sewer system for further treatment. The prohibition on the discharge of water from the closed loop cooling system, except as the result of the industrial reservoirs being used as cooling reservoirs, was included to provide a control over where the water was discharged and being able to impose effluent limitations at that point.

Water from the closed loop cooling system can be routed to Fort Carson along with the other wastewaters that go there.

In the cmTent Permit, the numerical effluent limitations on Internal Outfall OOIA are 30 mg/Las a 30 day average and 45 mg/Las a 7-day average on BODs and total suspended solids (TSS), a daily maximum limitation of I 0 mg/L on total petroleum hydrocarbons (TI-IP) instead of a 10 mg/L limitation on Oil and grease, a pl-I limitation of 6.5 - 9.0, and the requirement that there be no discharge of floating solids or foam nor shall there be a visible sheen. The limitations on BO Os and TSS were based on the State of Colorado's Regulations for Effluent Limitations. The state's regulations include a 10 mg/L limitation on oil and grease, but a 10 mg/L limitation on TPI-! was used in the Permit in~tead. The limitation on pl-! was based on the water quality standards of the receiving waters and the fact that the water quality standards do not allow for a mixing zone for pl-!. The requirement that there is to be no discharge of floating solids or foam nor shall there be a visible sheen is based on regional policy and best professional judgement as provided for in Section 402(a)(I) of the Clean Water Act. The effluent limitations and monitoring requirements at Internal Outfall 00 I A do not apply when the valve at Internal Outfall 0018 is closed so that there is no discharge from the !SOS to the discharge line (Outfall 001).

For Internal Outfall 0018, the current Permit requires that the valve be closed whenever any of the following conditions occur:

Statement of Basis for 2016 permit renewal~ USAF-Cheyenne Mountain AFS C0-0034762 Page 6of19

I. When there are "washing" operations (i.e., hosing down of the interior rock walls and ceilings of the tunnels and chambers) occurring within the underground potiion of the complex;

2. When there are known operations within the w1derground portion of the complex that are known to have a reasonable likelihood of causing the effluent limitations at Internal Outfall OO!A to be exceeded; and/or,

3. A spill is known to have occuned within the underground po1iion of the complex and there is a reasonable potential for pollutants from that spill to reach the ISDS.

For Internal Outfall 001 C, the cunent Pe1mit requires that the industrial reservoirs not be used as cooling reservoirs except on an as needed basis. This requirement is intended to minimize the discharge of water from the closed loop cooling system to the industrial reservoirs to the extent practical. The Permit requires that when the industrial reservoirs had been used as cooling reservoirs, water shall not be discharged from the industrial reservoirs to the ISDS when the valve at Internal Outfall 00 I B is open until a sample of the water can meet the following effluent limitations: total petroleum hydrocarbons I 0 mg/L, total residual chlorine (TRC) 0.100 mg/L, pH 6.5 to 9.0, and the water can pass an acute whole effluent toxicity test based on an acute 48-hour static replacement toxicity test using Ceriodaphnia dubia. A grab san1ple is to be taken from either the middle reservoir of the industrial reservoirs or Internal Outfall 001 C and used to demonstrate that the water from the middle reservoir can meet the above effluent limitations. It is this writer's understanding that there are no provisions for collecting a sample from the pipe that conveys water from the middle industrial reservoir to the ISDS, so samples must be collected from the middle reservoir. Since the cmTent Pern1it was issued there has not been a discharge from Outfall 00 IC while the valve at Internal Outfall 00 I B was open, i.e., routing the flow of the ISDS to the external storm drainage system.

The current Permit requires the Permittee to continue to implement a pollution prevention plan (PPP) with the primary objective of minimizing the entry of pollutants into the ISDS when the valve at Internal Outfall 00 I B is open.

In addition to the discharge from the ISDS to the discharge line via Outfall 001 A, the current Pe1mit authorizes discharges from the drain lines from the exhaust stacks that are paii of the ventilation system for the underground complex at CMAFS. Exhaust gases from the generators, vapors from the cooling towers, stale air, etc., are collected and blown out through the exhaust stacks. There are two exhaust stacks, a "no1th stack" and a "south stack". Normally only one exhaust stack is used at a time, with the south stack used most of the time. The exhaust stacks are ve1tical and approximately 12 feet in diameter.

The exhaust comes into the stack from the side near the base of the stack. At the base of each exhaust stack there is a sump for collecting any water that may collect in that portion of the ventilation system. It is this writer's understanding that the temperatures in a stack when it is being used is approximately 160°F, so there should not be any condensation of water from the exhaust gases. However, water can collect in the sumps during heavy precipitation and possibly from groundwater infiltration. Each sump has an overflow drain line that slopes downward and outward, ending at the ground surface in a vertical concrete wall a few feet high. The end of the drain line from the north stack has become covered by loose rock that slid down the slope. The Air Force indicated that it is considering uncovering the end of the drain line, but at this time there are no definite plans to do so. The drain lines from the north stack ai1d south stack were designated Outfall 002 and Outfall 003, respectively.

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Actual discharges from the two drain lines have not been observed. In order to get an idea of how much water could potentially be discharged from a drain line due to precipitation, this writer did calculations using data from the National Oceanic and Atmospheric Administration's (NOAA) Western U.S.

Precipitation Frequency Maps (Atlas 2 published in 1973). For the area of the CMAFS, a I in 100 year, 6-hour precipitation event is approximately 3.6 inches. For an area 12 feet in diameter, that would give approximately 254 gallons of water, assuming there were no evaporation losses. If that water were discharged over the 6-hour period, the average flow rate would be about 0. 7 gallon per minute (gpm). A 1 in 100 year, 24-hour precipitation event is about 5 inches, which would result in about 353 gallons and an average discharge rate of about 0.25 gpm over the 24 hours. It is not known if this water would reach waters of the U.S. as surface flow.

The current Permit does not contain numerical effluent limitations for the potential discharges from Outfalls 002 and 003. If there were to be a discharge to waters of the U.S., the discharge would most likely be due to heavy precipitation. Part 1.3.5 of the Permit specifies that there are no numerical effluent limitations for Outfalls 002 and 003. Instead, Part 1.4. of the Permit required the Permittee to modify the PPP (developed and implemented under the previous Pe1mit for the ISDS) to include provisions for minimizing the potential for discharging pollutants, via Outfalls 002 and 003, from the sumps located in the air stacks. The Pem1it also required the Permittee to continue to implement the provisions of the PPP that apply to the ISDS. The Permit requires that at least annually, Outfalls 002 and 003 and the immediate areas down gradient from them shall be inspected for signs of sediment, oil and grease, and/or other pollutants having been discharged from either outfall. To the extent practical, the inspections should be conducted within a week after a rainfall event of 1 inch or greater.

Because of the massive mudslide that occurred on September 12, 2013, the outfall line to Outfall 001 was significantly damaged and the control valves at Internal Outfall 0018 were buried. From September 22, 2013, through August 4, 2015, all flow through Internal Outfall 001 B was routed to Fort Carson. Staiiing August 5, 2015, the use of Outfall 001 was resumed after the necessary repairs and changes were made.

Self-Monitoring Data

A summary of the self-monitoring data for April I, 2011, through March 31, 2016, is given below. The flow data that were included in ilie discharge monitoring reports (DMRs) were not included in the summary because the reported data included flow data that occmTed when the flow was being routed to Fort Carson. Instead, the flow data presented in the summary are based on a review by this writer of the daily operational logs that the Pe1mittee was required to maintain.

Paran1eter Minimum Maximum Average pH, s.u. 6.5 8.3 NIA Total suspended Solids, mg/L 0 26 13.7 Total Petroleum Hydrocarbons, mg/L 0 0.53 0.2 Oil and Grease, visual None None NIA BODs, mg/L 0 0.6 0.4 Total Flow Discharned/Calendar Quaiier, gallons a/ 19,305 1,348,400 463,020 Average Flow/Day When Discharging, gpd bl 212 16,246 5,418 Range of Daily Flows, gpd 0 241,900 NIA

<!/ The total amount of water discharged to Outfall 00 I during the calendar quarter when a discharge occurred during the quarter.

S!alement of Basis/or 2016 permit renewal - USAF-Cheyenne Maunlain AFS C0-003./762 Page 8of19

QI The total amount of water discharged during a calendar quarter divided by the number of days the valves were set to allow a discharge to Outfall 00 I. Some days no discharge occurred.

There was no reported discharge from Outfall 001 C, the industrial reservoir, from April I, 2011 through March 31, 2016. Likewise, for Outfalls 002 and 003, it was reported that the inspections found no signs of contaminants being discharged.

Metals Data for Drinking Water System

The Safe Drinking Water Program in the Water Quality Control Division (WQCD) of the Colorado Department of Public Health and Environment (CDPHE) has metals data for the drinking water system at the CMAFS. Although the data is for the drinking water system and not the discharge from Outfall 00 I, most of the data gives an indication of the metals content of the spring water that is the source of most of the water inside the underground facility. All of the samples except for the samples for lead and copper were taken from a tank that stores drinking water for the drinking water system. The samples for lead and copper were taken from the distribution system of the drinking water system, with several samples collected during each sampling event. Stmiing in 1996 there were I 0 samples per sampling event. The 901 h percentile value of lead m1d copper for each sampling event were listed.

To obtain a general idea of the current concentrations of metals in the spring water, the data from 2007 to 2015 were summarized. Below is a listing of the metal mmlyzed for; the detection limits of the analytical methods used, when given; and the maximum concentrations repmied for that metal. For lead and copper, the maximum reported 90'h percentile value is given. The data for lead and copper are for samples that were collected in 2007, 2010, 2012, and 2015 and the data for the other metals are for samples collected in 2007, 2008, m1d 2012. With the exception of the lead and copper values, the data indicate that the spring water has a low mineral content. The concentrations oflead m1d copper should not be considered representative of the quality of the spring water because the samples were collected from the drinking water distribution system, where there is the potential for leaching oflead and copper.

However, as a precautionary measure, the renewal Permit will require monitoring at Outfall 00 I A for lead, copper and hardness. In water with low hardness, the concentrations of lead and/or copper reported for samples from the distribution system would be toxic to aquatic life.

Summary of Metals Data for D1inking Water System Analyte Detection Limit Maximum Value, nw/L mg/L Arsenic c/ 0.001 ND Barium cl NG 0.073 Cadmium c/ 0.001 ND Chromium c/ 0.001 ND Mercury c/ 0.0002 ND Nickel c/ 0.001 ND Selenium cl ? a/ 0.001 a/ Sodium c/ NG 9.9 Antimony, Total c/ 0.003 ND Beryllium, Total c/ 0.0003 ND Thallium Total c/ 0.0003 ND Lead d/ NG el 0.008 bl Conper di NG el 0.17 bl

Stateme/1/ of Basis for 2016 permit renewal - USAF-Cheyenne Mountain AFS C0-0034762 Page 9of19 ijf Two samples had 0.002 mg/L listed as detection limit and zero listed as resultant measure. The third sample had a resultant measure of0.001 mg/L listed and no detection limit given.

)2/ Maximum of the 90111 percentile values reported.

r;/ Data from 2007. 2008, and 2012 samples.

QI Data from 2007, 2010, 2012, and 2015 samples.

~I Detection limit not given.

Receiving Waters

The discharge from Outfall 00 l and the potential discharges from Outfalls 002 and 003 potentially could go to unnamed ephemeral tributaries of Fountain Creek. which is a tributary of the Arkansas River. The discharge from Outfall 001 and the potential discharge from Outfall 002 go lo an unnamed ephemeral tributary that flows to the east for approximately two miles before crossing under state Highway 115, approximately 1/4 ofa mile to the south of O'Connell Blvd, and onto the Fort Carson Military Reservation (FCMR). On the FCMR, the unnamed tributary combines with other unnamed streams and drainageways to form one stream that flows to the southeast into Fountain Creek in Section 6, Tl 6S, R68W near the City of Fountain. The potential discharge from Outfall 003 potentially would go to one of the unnamed tributaries in Limekiln Valley. The drainage from Limekiln Valley flows east onto the FCMR and near Prussman Blvd. it combines with the previously mentioned drainageway that flows into Fountain Creek

Based on simple measurements on a map, this author estimates that it is at least I 0 stream miles from the point of discharge from Outfall 001 to the confluence of the unnamed tributary with Fountain Creek. All but the last 1/4 to 1/2 mile of the unnamed tributaries are in Stream Segment 4 of the Fountain Creek Basin for purposes of stream classifications by the state of Colorado. Streams and reservoirs in Segment 4 are classified for Class 2 Aquatic Life Wann, Class E Recreation, Water Supply and Agriculture and are designated use-protected. The assigned water quality standards include the following:

Physical and Biological Inorganic, mg/L Metals, ug/L

T=TVS(WS-ll) NH1(ac/ch)=TVS B=0.75 As(ac)=IOO CrVl(ac/ch)=TVS Hg(c11)=0.0 I (tot) oc C!,(ac)=0.019 N02=0.5 As( ch)=0.02-10 Cu(ac/ch)=TVS Mo(ch)=l 60(Trec) D.O. = 5.0 C!,(ch)=0.019 N01=IO (TrecjA Fe(ch)=WS(dis) Ni(ac/ch)=TVS mg/L CN=0.005 Cl=250 Cd(ac/ch)=TVS Fe( ch)= I OOO(Trec) Se(ac/ch)=TVS pH= 6.5-9.0 S=0.002 so,=ws Crlll(ac)=50 Pb(ac/ch)=TVS Ag(ac/ch)=TVS E. Coli= P=l 70ug/L (Tree) Mn(ac/ch)=TVS Zn(ac/ch)=TVS

I 26/l 00 mL (totf Cr!Il(ch)=TVS Mn(ch)=WS(dis) Chia= ISO

1110/1112 c

(ac) =acute; (ch)= chronic; (dis)= Dissolved; (Tree)= Total recoverable; TVS= Table Value Standard;

tot= Total; WS =Water supply; WS =Warm Stream Tier II temperature standard A = Whenever a range of standards is listed and referenced to this footnote, the first number in the range is a strictly health-based value, based on the Commission's established methodology for human health-based standards. The second number in the range is a maximum contaminant level, established under the federal Safe Drinking Water Act that has been determined to be an acceptable level of this chemical in public water supplies, taking treatability and laboratory detection limits into account. Control requirements, such as discharge permit effluent limitations shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an '"end-of-pipe" discharge level more restrictive than the second

Stale1nent oj'Basisfor 2016 pern1il reneiva/ - USAF-Cheyenne lvfountain AFS C'0-0034762 Page /Oof/9 number in the range. Water bodies will be considered in attainment of this standard and not included on the Section 303(d) List, so long as the existing ambient quality does not exceed the second number in the range.

c =Total phosphorus and chlorophyll a standards apply only above the facilities listed at 32.5(4) (i.e., Regulation 32 at 32.5(4)).

Stream Segment 5 of the Fountain Creek Basin for purposes of stream classification includes the unnamed tributary from the boundary of Foti Carson to the confluence with Fountain Creek. It is approximately 1/4 to 112 mile in length. Stream segment 5 is classified for Class 1 Aquatic Life Warm, Class N Recreation, and Agriculture and is undesignated. The assigned water quality standards include the following:

Physical and Biological Inorganic, mg/L Metals, ug/L

T=TVS(WS-Jl) NH,(ac/ch)=TVS B=0.75 As(ac)=340 Fe( ch)= I OOO(Trec) Ni(ac/ch)=TVS oc Cb(ac)=0.019 N02=0.5 As(ch)=IOO Pb(ac/ch)=TVS Se(ac/ch)=TVS

0.0.= 5.0 Ch(ch)=0.019 N0,=100 (Tree) Mn(ac/ch)=TVS Ag(ac/ch)=TVS mg/L CN=0.005 P=l70ug/L Cd(ac/ch)=TVS Hg( ch)=O.O 1 (tot) Zn(ac/ch)=TVS pH= 6.5-9.0 S=0.002 (tot) Crlll(ac/ch)=TVS Mo( ch)= I 60(Trec) E. Coli= CrIII( ch)= I 00 630/100 mL (Tree)

CrVl(ac/ch)=TVS Cu(ac/ch)=TVS

(ac) =acute; (ch)= chrome; (Tree)= Total recoverable; TVS= Table Value Standard; (tot)= Total;

(WS-II) =Warm Stream Tier II temperature standard

Water Oualitv Considerations and Antidegradation Review

Based on available information, it is anticipated that the discharges authorized by the renewal permit will not cause a violation of water quality standards in Stream Segments 4, 5 and 2a of Fountain Creek if the conditions of the renewal Permit are met. Section 31.8(2) of the state of Colorado's Basic Standards and Methodologies for Surface Water, specifies that undesignated waters are subject to the antidegradation review provisions of section 31.8(3) of the regulations. Stream segments designated as use-protected are not subject to the provisions of the anti de gradation review process. The antidegradation regulations were effective December 22, 2000. Since the discharge potentially could reach Stream Segments 5 and 2a of the Fountain Creek Basin (in that order) and since those stream segments are undesignated, the discharges are subject to the anti de gradation review provisions of section 31 .8(3). The first step of the screening process for the antidegradation review involves determining if there is a new or increased water quality impact from the discharges. The baseline water quality for purposes of making a comparison is to be based on the ambient water quality as of September 30, 2000.

Since the wastewater sources are unchanged, the effluent limitations in the renewal Permit will remain essentially the same, and it is unlikely that the discharges will reach Segments 5 and 2a except during wet weather runoff conditions, which will provide dilution, this writer believes that it is highly unlikely that there will be new or increased water quality impacts due to the discharges from this facility.

Therefore, in accordance with the antidegradation regulations and guidance, an antidegradation review is not necessary.

Statement of Basis for 2016 permit renewal - USAF-Cheyenne Mountain AFS C0-0034762 Page II of 19

Addition of New Internal Outfall:

Because of the numerous points where flow and/or pollutants can enter the ISDS downstream ofOOlA, the renewal Permit requires the Permittee to install a new Internal Outfall 00 ID within the North Pmial near the entrance. It is to be located either at the last floor grate in the ISDS before the entrance or in a manhole between the last floor grate and the entrance. It is to be operational as soon as reasonable and practicable, but no later than two (2) years after the effective date of the renewal Permit. Then the effluent limitations and monitoring requirements that apply to Internal Outfall OOlA will apply to Internal Outfall 0010 and will no longer apply at Internal Outfall OOlA. A compliance schedule is not required because the new outfall is to be operational within two years after the effective date of the Permit.

Permit Limitations in Renewal Permit:

The NPDES regulations at 40 CFR Part 122.44(1) require that effluent limitations in a renewal Permit, with certain exceptions, be at least as stringent as the effluent limitations in the previous Permit. The general effluent limitations and prohibitions given in Part 1.3.1.I of the renewal Pe1111it have been changed somewhat in that there is to be no discharge of water from the industrial reservoirs. Because there is to be no discharge from the industrial reservoirs, Internal Outfall 00 IC is no longer needed and will not be used as a control point in the renewal Permit.

The effluent limitations for Internal Outfalls 00 I A and 001 B in the renewal Permit are basically the same as in the current Permit. One exception is changing the I 0 mg/L limitation of total petroleum hydrocarbons to a limitation of 10 mg/L on oil and grease. The change is being made because there is not an approved analytical procedure for total petroleum hydrocarbons list under 40 CFR Part 136 and the concerns of some that the analytical proceeder for total petroleum hydrocarbons giving false positives. The effluent limitations for Internal Outfall 001 A and subsequently to Internal Outfall 001 D are given below.

Effluent Limitation

30-Day 7-Day Daily Effluent Characteristic Average <Ji Average !!,I Maximum <Ji

BOD,, mg/L 30 45 NIA

Total Suspended Solids, mglL 30 45 NIA

Oil and Grease, mglL NIA NIA 10

The pH of the discharge shall not be less than 6.5 or greater than 9.0 in any sample.

There shall be no discharge of floating oil nor shall there be a visible sheen.

<Ji See Definitions, Part 1.1 for the definition of terms.

The limitations on BODs, total suspended solids, and oil and grease are based on the State of Colorado's Regulations for Effluent Limitations. On a practical basis there is not a need for effluent limitations on BODs except as a safeguard. The limitation on pH is based on the water quality standards of the receiving waters and the fact that the Colorado water quality standards do not allow for a mixing zone for pH. Furthermore, there often would not be any dilution water in the stream, so the effluent limitation has to be effective at the point of discharge. The requirement that there is to be no discharge of floating

Statement of Basis for 2016 permit renewal - USAF-Cheyenne Mou/1/ain AFS C0-003-1762 Page 12 of'J9 oil nor shall there be a visible sheen is based on regional policy and best professional judgement as provided for in Section 402(a)(I) of the Clean Water Act.

There will not be any effluent limitations on temperature because the discharge from Outfall 001 goes to an ephemeral stream and there is no evidence that the aquatic life use may be negatively affected by the thermal component of the discharge. See Part 111.2.a of the CWQCD's Procedures for Conducting Assessments for Implementation of Temperature Standards in Discharge Permits, Policy No. WQP-23, July 3, 2008.

The Colorado Water Quality Control Commission (WQCC) established Regulation #85, Nutrients Management Control Regulation (5 CCR 1002-85) effective September 30, 2012. Among other things, Regulation 85 establishes technology based effluent limitations on total inorganic nitrogen and total phosphorus for certain domestic wastewater treatment works (DWWTW) and certain non-domestic wastewater treatment works (i.e., industrial discharges). It also establishes monitoring requirements. The effluent limitations for non-domestic wastewater treatment works that were discharging prior to May 31, 2012, apply to those (A) whose Standard Industrial Classification code is in the Major Group 20 and (B) any other non-domestic discharger for which the Division has determined, based on credible information that the facility is expected, without treatment for nutrients, to discharge total inorganic nitrogen or total phosphorus concentrations to surface waters in excess of the respective effluent limitations in section 85.5(1)(a)(iii). Those effluent limitations are given below.

Parameter Parameter Limitations Annual Median a/ 95t1i Percentile b/

(a) Total Phosphorus 1.0 mg/L 2.5 mg/L

(b) Total Inorganic Nitrogen c/ 15 mg/L 20 mg/L

§/Running Annual Median: The median of all samples taken in the most recent 12 calendar months.

QI The 95'h percentile of all samples taken in the most recent 12 calendar months.

r;j Determined as the sum of nitrates as N, nitrite as N, and ammonia as N.

Based on available information, it appears highly unlikely that the concentrations of either total phosphorus or total inorganic nitrogen in the discharge from Outfall 001 will come close to the above effluent limitations. Therefore, no effluent limitations on nutrients will be put in the renewal Pem1it. If subsequent monitoring indicated that effluent limitations on either nutrient are appropriate, the limitation(s) will be placed in the Petrnit upon renewal.

For Internal Outfall OOIB the renewal Petrnit requires that the valve be closed (i.e., no discharge to surface waters) when certain conditions occur. The conditions are the same as in the current Permit and are given in Part 1.3.1.3 of the Permit.

For Outfalls 002 and 003 the current Permit had no numerical effluent limitations, but instead depended on the development and implementation of a pollution prevention plan to minimize the discharge of pollutants. The renewal Permit has the same requirements. The next section, Pollution Prevention Plan, has more details about what the Pem1it requires regarding the pollution prevention plan. Pat1 4.15.4 that provides for modifying the Permit if inspections and/or other information show that effluent limitations are appropriate for Outfalls 002 and/or 003.

Pollution Prevention Plan

Statement of Basis for 2016 permit renewal - USAF-Cheyenne Mountain AFS C0-003~762 Page 13of19

Staiiing with the Permit issued in 2000. the Permittee was required to develop and implement a pollution prevention plan (PPP) to minimize the entry of pollutants into the interior stmm drainage system during periods when the valve at Internal Outfall 001 B is open. The Pe1mit issued in 2005 required the Permittee to continue to implement the PPP for the interior storm drainage system and to modify the PPP to include provisions for minimizing the potential for discharging pollutai1ts, via Outfalls 002 a!ld 003, from the sumps located in the air stacks. The provisions were to include, but not necessarily be limited to, measures that can be taken to minimize pollutants being discharged from the sumps as the result of repair activities ai1d maintenance activities in the air stacks. Those requirements were continued in the Permit issued in 20 I 0 and will be continued in the renewal Permit.

Paii 1.4 of the renewal Permit requires the Permittee to continue to implement the PPP for the interior storm drainage system and Outfalls 002 and 003 that was developed and implemented as a requirement of previous Penni ts. The PPP must be ainended whenever there is a cha!lge in design, construction, operation, or maintenai1ce at the facility which has a significant effect on the discharge, or potential for discharge, of pollutants from the interior storm drainage system and/or Outfalls 002 and 003. The PPP is also to be amended whenever during an inspection or investigation by the Pennittee or federal officials it is determined that the PPP is ineffective in eliminating or significantly minimizing the dischai·ge of pollutants from the interior storm drainage system and/or Outfalls 002 and 003. The PPP shall be reviewed annually to determine ifit needs to be amended to meet the objectives of the PPP. If appropriate, the PPP shall be amended.

Self-Monitoring Requirements

The self-monitoring requirements in the renewal Permit ai·e given in Part 1.3.2 and are similar to those in the current Pe1mit with the exception of the frequencies for BODs and Oil and Grease for Internal Outfall 001 f\. The self-monitoring data for the current Permit have consistently shown BODs concentrations below the detection level. Thal is not surprising for this type of effluent. During the same period the repo1ied concentrations ofTPH ranged from non-detect to a maximum of 0.53 mg/L, whereas the effluent limitation is I 0 mg/L. The Permit does require that a grab sample be collected and a!lalyzed for oil and grease if a sheen and/or floating oil are observed in the visual monitoring. As in the current Permit, for Internal Outfall OOIA only, the monitoring results obtained when there is a discharge to the discharge line shall be reported on the discharge monitoring report.

In addition to repmiing the monitoring results when there is a discharge to the discharge line, the Permit requires a monthly log to be maintained that at a minimum includes the following: ( 1) the dates when flow is being discharged to Outfall 001; (2) all flow meter readings taken when flow is being directed to Outfall 001; and (3) the total volume of water discharged since the previous meter reading. (NOTE: a format similar to the log used during the previous Permit is acceptable.) The log shall be in the form of a!1 Excel" spreadsheet file. For each repo1iing period (i.e. calendar quarter) a spreadsheet containing the three monthly logs for that reporting period shall be attached to the NetDMR for that reporting period and submitted with the NetDMR.

Routine monitoring for temperature will not be required because the discharge is intermittent, often of low volume, and there is very little thermal input caused by ma!l to the water being discharged. The temperature of the discharge will be primarily determined by the volume a!ld temperature of the infiltrating groundwater and the ambient temperature within the facility. As a check, quarterly monitoring of the temperature of the discharge at Internal Outfall 001 A and subsequently at Internal

Outfall 001 D will be required. This requirement may be deleted when the Permit is reissued in about 2021 if additional temperature data are not considered necessary. lnstream monitoring for temperature will not be required because the receiving water is an ephemeral drainageway and generally there is no flow during dry weather other than from the discharge.

As part of an effort to regulate the discharge of nutrients, the Colorado WQCD established Regulation 85, which establishes technology based effluent limitations and monitoring requirements for total inorganic nitrogen and total phosphorus for discharge from certain domestic wastewater systems (DWWTS) and some…