DEPARTMENT OF ENVIRONMENTAL QUALITY WATER QUALITY …deq.mt.gov/Portals/112/Water/WQInfo/Documents/MT... · vaults is derived from: regulated storm water, the ammonia unloading containment

DEPARTMENT OF ENVIRONMENTAL QUALITY WATER QUALITY DIVISION

MONTANA POLLUTANT DISCHARGE ELIMINATION SYSTEM (MPDES)

Fact Sheet PERMITTEE: Ash Grove Cement Company PERMIT NO.: MT0000451 RECEIVING WATER: Prickly Pear Creek FACILITY INFORMATION Name: Ash Grove Cement Company – Montana City Plant Location: 100 Highway 518, Clancy, MT

Township 9N, Range 3W, Sections 13 & 17 Jefferson County

Contact: Jeff Briggs, Environmental Manager 100 Highway 518

Clancy, MT 59634 FEE INFORMATION Number of Outfalls: 2 (Industrial -Minor) Type of Outfall: 001 Treated Wastewater and Storm Water 002 Treated Wastewater and Storm Water

I. Permit Status

This action is the renewal of the current Montana Pollutant Discharge Elimination System (MPDES) permit MT0000451 for Ash Grove Cement Company’s Montana City Plant (Ash Grove), which became effective November 1, 2010, and expired on October 31, 2015 (2010-issued permit). Ash Grove submitted a MPDES renewal application to the Department of Environmental Quality (DEQ) on May 5, 2015, and the renewal application fee of $9,000 for three outfalls on May 1, 2015.

Fact Sheet Permit No. MT0000451 August 2018 Page 2 of 32

On June 4, 2015, DEQ issued a notice of deficiency and request for clarification. On July 13, 2015, DEQ received the requested information. The application was considered complete and the existing MPDES permit administratively extended on August 13, 2015, and a refund of $3,000 was made to Ash Grove for overpayment for an unnecessary third outfall.

Ash Grove also maintains a separate storm water authorization MTR000523 under the industrial storm water general permit for three outfalls that contain only non-process storm water.

II. Facility Information

A. Facility Description

Process Description Ash Grove is a Portland Cement manufacturing facility that was constructed in 1962. It employs approximately 80 people. The facility uses the non-leaching wet process (see Section III of this Fact Sheet), using the following process steps:

1. Quarrying and crushing limestone, clay, and silica and the addition of de-zinced slag from the ASARCO smelter as an iron source. Ash Grove uses ammonium nitrate/fuel oil as a blasting agent in some quarry areas.

2. Grinding the crushed raw materials with water in a ball mill to form a slurry at 70 tons per hour. The slurry is stored in one of two 65 foot-diameter concrete tanks until processing in the kiln.

3. Pyroprocessing the slurry in a rotary kiln to form Portland cement clinker at 68 tons per hour. The kiln uses 5.6 billion British thermal units (Btu) per day from a blend of fuels (coal, natural gas, and coke – for high sulfur). Calcium silicate clinker (3CaO.SiO2 and 2CaO.SiO2) can contain aluminum and iron. Ammonia is used in air pollution control equipment.

4. Grinding the clinker with gypsum to produce Portland cement. Gypsum is a mineral classified as a sulfate -- calcium sulfate dehydrate or hydrated calcium sulfate -- with the chemical formula CaSO4 . 2H2O.

Outfall Descriptions Ash Grove has requested to renew MPDES permit coverage for two of the three currently-permitted outfalls discharging to Prickly Pear Creek (see Figure #1):

Outfall 001 – North Wastewater Pond (north pond). Ash Grove can open a valve to discharge from the north pond through Outfall 001 to Prickly Pear Creek at 46º 32' 40"N, 111º 55’ 26"W. The last discharge from Outfall 001 was in 1996; the maximum projected discharge is estimated as 0.0072 million gallons per day (mgd). Wastewater sources to the north pond include:


• Settling Vaults – a series of vaults which settle solids out of the wastewater stream

prior to further treatment in the north pond. The wastewater controlled by the settling vaults is derived from: regulated storm water, the ammonia unloading containment area, and cooling water from the #2, #3, and #4 Kiln Trunnions and the East & West Kiln drive gear box.

• South Wastewater Pond (south pond) – collected wastewater can flow between the north and south ponds, as needed.

• Storm water previously discharged through Outfall 003. The storm water from this area contacts iron slag piles and as a result is subject to federal technology-based effluent limits (TBELs, Section III). This regulated storm water previously drained to a pipe under the road that discharged into Prickly Pear Creek; however, the drain was plugged (sealed with concrete) in 2015. Any storm water from this area now pools on either side of the plant south entrance road and infiltrates or evaporates; Ash Grove is prepared to pump it to the north pond if needed.

Outfall 002 – this outfall had two compliance monitoring points in the 2010-issued permit: an internal monitoring location for TBELs (Outfall 002A) and the final outfall for Water Quality-based Effluent Limits (WQBELs) at the historic location (Outfall 002).

Most wastewater is first settled in the south pond then is pumped up either to a water reclaim tank for re-use or pumped into Pond #3 (Klem Lake) prior to being discharged through Outfall 002. Wastewater sources to the south pond include:

• Mill room pipe – One pipe discharging combination of wastewater from a truck wash pad treated by an oil/water separator, mill room floor clean-up, and storm water;

• Noncontact cooling water – discharge from the New Silos compressor (infrequently);

• North Pond – collected wastewater can flow between the north and south ponds, as needed; and

• Slag Pile Runoff (potentially).

Outfall 002A – internal monitoring location at 46º 32' 43"N, 111º 55’ 16"W (proposed to be removed).

Outfall 002A was added as an internal monitoring point in the 2010-issued permit to demonstrate compliance with TBELs, since it was believed that all the site’s regulated storm water passed through this spot. The sampling point captured the quality of the wastewater pumped from the south pond before it entered Klem Lake, which was thought to be the last place before dilution with ground water or storm water.

Since then, Ash Grove has identified an additional TBEL source that does not receive treatment in Klem Lake – storm water which contacts gypsum storage piles. Furthermore, they have stated that they have observed no significant ground water dilution in Klem Lake. Therefore, DEQ has determined in this renewal that Outfall


002 is the correct monitoring location for TBELs. Internal monitoring requirements at Outfall 002A will be removed.

Outfall 002 – discharge location at 46º 32' 43"N, 111º 55’ 25"W.

Wastewater pumped up from the south pond is either stored in a water reclaim tank until used as dust suppression or is discharged into Klem Lake. Once in Klem Lake the wastewater settles and either infiltrates or flows through an upper vegetated wetlands basin, downhill to a lower vegetated basin, and discharges through a pipe under the road to Prickly Pear Creek (Outfall 002). Ash Grove recently determined that there is a separate storm water path that potentially contacts gypsum storage piles (regulated storm water) before joining the treated discharge in the lower vegetated basin.

The average discharge flow rate recorded for Outfall 002 has decreased from 25 gallons per minute (gpm) noted in 1994 to 17 gpm in 2010 to 3 gpm for the current period of record. The highest monthly average flow from Outfall 002 during the current period of record was 0.0125 mgd (8.7 gpm).

Other Storm water - Storm water that does not contact storage areas for materials “which are used in or derived from the manufacture of cement” is permitted under storm water general permit authorization MTR000523, and therefore is not included in this MPDES permit. This includes storm water that discharges at the following locations:

• SW-001 – Clark Gulch Quarry

• SW-002 – McClellan Creek Quarry

• SW-003 – Main Plant area - southern access road (non-process storm water only)

B. Effluent Characteristics

Outfall 001 There has not been a discharge through Outfall 001 since 1996.

Outfall 002 Ash Grove reported discharge into Prickly Pear Creek for most months between January 2014 through February 2018.

During periods with discharge, the average monthly discharge rate ranged from a minimum of 0.0004 mgd to 0.0125 mgd; the maximum daily discharge rate ranged from 0.001 mgd to 0.032 mgd. See Table 1 for a summary of the discharge characteristics as reported on monthly Discharge Monitoring Reports (DMRs).


Table 1. Outfall 002 Effluent Characteristics January 2014 – February 2018

Parameter Units Permit Limit (1)

Minimum Value

Maximum Value

Average Value (2)

Number of

Samples Flow (Monthly Average) mgd NA 0.0004 0.0125 0.004 45 Flow (Daily Maximum) mgd NA 0.0014 0.0317 0.008 45 pH s.u. 6-9 7.6 8.5 -- 45

Oil & Grease Visual Y/N NA No observed oil & grease 45

mg/L NA < 1.0 < 1.0 < 1.0 8 Sulfate, as S mg/L NA 131 827 425 8 Aluminum, Dissolved µg/L NA 1.0 < 30 < 23 8 Arsenic, Total Recoverable µg/L NA 5.0 12 6.9 8 Cadmium, Total Recoverable µg/L NA < 0.08 0.34 < 0.11 8 Copper, Total Recoverable µg/L NA < 1.0 60 < 13 8 Iron, Total Recoverable µg/L NA < 50 430 < 98 8 Lead, Total Recoverable µg/L NA < 0.5 1.3 < 0.6 8 Zinc, Total Recoverable µg/L NA 17 69 42 8

Footnotes: The symbol “<” indicates the detection limit for nondetects; in the case of average values, DEQ used the detection limits for the nondetects.

(1) “NA” indicates no limit in permit; monitoring requirement only. (2) Average value for the months with discharge.

Effluent data was also supplied on EPA Form 2C submitted in 2015. DEQ did not use the Form 2C information on those parameters that were also reported on DMRs, since the DMR dataset is more recent. The following additional data was provided in Form 2C:

• Biochemical oxygen demand (BOD): 2.8 mg/L (sample date 4/10/15) • Chemical oxygen demand (COD): < 5 mg/L (sample date 4/10/15) • Total Suspended Solids (TSS): 15 mg/L maximum (nine samples) • Ammonia: 0.03 mg/L (sample date 4/10/15) • Nitrate-Nitrite, as N: 2.07 mg/L (sample date 4/10/15)

Outfall 002A (Internal Monitoring location identified by DMRs as Outfall 004A, proposed to discontinue) Ash Grove reported flow from the south pond into Klem Lake for most months from January 1, 2014 through January 31, 2018. The average monthly discharge rate into Klem Lake ranged from 0.2 gpm (0.0003 mgd) to 24 gpm (0.035 mgd) and the maximum daily rate ranged from 0.2 gpm (0.0003 mgd) to 87 gpm (0.13 mgd). See Table 2 for a summary of the discharge characteristics as reported on monthly DMRs.


Table 2. Outfall 002A Internal Monitoring Effluent Characteristics

January 2014 – February 2018

Parameter Units Permit Limit (1)

Minimum Value

Maximum Value

Average Value (2)

# Samples

Flow mgd NA 0.0003 0.035 0.014 45 Total Suspended Solids mg/L 50 (3) 1.0 136 16 45 pH s.u. 6 - 9 7.8 8.8 -- 45 Oil & Grease Visual Y/N NA No observed oil & grease 45

Footnotes: (1) “NA” indicates no limit in permit; monitoring requirement only. (2) Average value for the months with discharge. (3) Outfall 002A – the TSS TBEL was applied to this internal outfall on November 1, 2012.

Outfall 003 (discontinued) Ash Grove blocked this outfall in 2015; storm water from this area now pools near the plant entrance and infiltrates or evaporates. If necessary, Ash Grove will pump this water to the north pond.

The most recent discharges through Outfall 003 were during three months in 2011 (Ash Grove discovered a reporting issue that incorrectly reported a discharge in 2016 from Outfall 003; this was mistaken). The 2011 discharges ranged from 0.2 – 4.3 gpm (or 0.0003 – 0.0061 mgd). This regulated storm water had TSS levels above the 50 mg/L effluent limit (625 mg/L and 124 mg/L). In addition, one sample showed elevated metals, including: aluminum at 236 µg/L, arsenic at 19 µg/L, cadmium at 1.5 µg/L, iron at 4,230 µg/L, lead at 7 µg/L, and zinc at 160 µg/L.

C. Compliance History

DEQ personnel conducted two compliance evaluation inspections since the effective date of the previous permit on November 1, 2010 with no violations noted. Based on a review of the administrative file, Ash Grove had several violations of permit conditions -- both at Outfall 002A (internal monitoring location) and Outfall 003 (prior to plugging it). See Table 3:

Table 3. Summary of Violations: November 2011 until November 2017 Outfall Violation Date(s) Parameter Violation Letter 002A January 2011

February 2011 Failure to monitor TSS 4/22/2011

5/21/2011 December 2014 Failure to report flow rate 3/20/2015 July 2017 TSS – 130 mg/L > 50 mg/L 9/15/2017 November 2017 TSS – 136 mg/L > 50 mg/L 1/14/2018

003 2/4/2011 pH – 12.7 su > 9 su TSS – 625 mg/L > 50 mg/L

4/14/2011 & 4/21/2011 5/20/2011

5/20/2011 TSS – 124 mg/L > 50 mg/L 8/18/2011


III. Proposed Technology-based Effluent Limits (TBEL)

A. Scope and Authority

Permits include, at a minimum, Technology-based Effluent Limits (TBELs). TBELs may be based on national standards established by the EPA, or, in some cases, standards established by the permit writer on a case-by-case basis. National Effluent Limitations Guidelines (ELGs) have been promulgated under Subchapter N for the cement manufacturing point source category.

B. Cement Manufacturing ELGs

40 CFR Part 411 identifies ELGs for the Cement Manufacturing Point Source Category. Ash Grove was evaluated for applicability to the three subparts for 40 CFR 411:

1. Subpart A Nonleaching Subcategory is “applicable to discharges resulting from the process in which several mineral ingredients (limestone or other natural sources of calcium carbonate, silica, alumina and iron together with gypsum) are used in the manufacturing of cement and in which kiln dust is not contacted with water as an integral part of the process and water is not used in wet scrubbers to control kiln stack emissions.”

2. Subpart B Leaching Subcategory is “applicable to discharges resulting from the process in which several mineral ingredients (limestone or other natural sources of calcium carbonate, silica, alumina and iron together with gypsum) are used in the manufacturing of cement and in which kiln dust is contacted with water as an integral part of the process or water is used in wet scrubbers to control kiln stack emissions.”

3. Subpart C Materials Storage Piles Runoff Subcategory. This subpart is “applicable to discharges resulting from the runoff of rainfall which derives from the storage of materials including raw materials, intermediate products, finished products and waste materials which are used in or derived from the manufacture of cement under either Subcategory A or B.”

Applicability to Subparts A & B Ash Grove uses up to 125 gpm water for making a slurry in the wet non-leaching cement manufacturing process. This water is consumed in the process or lost as steam from the kiln. It is not discharged. DEQ finds that discharges from Ash Grove’s facility are not process wastewater and not subject to Subparts A and B, as follows:

• storm water (both non-regulated and regulated under Subpart C),

• noncontact cooling water (trunnions, gear box cooler, new silos compressor),

• mill room floor drains, and

• treated vehicle wash pad wastewater.


Furthermore, Ash Grove applies water to the kiln dust to control air emissions; this water is not discharged and is not considered an integral part of the process.

The following definitions were considered in this evaluation:

• Cement “process water” is defined as: “A general term applied to the water used in operations directly related to the manufacture of a product, and sometimes contacting the products or raw materials, as distinguished from cooling water, boiler water, and all other water used in ancillary operations. In cement manufacturing the term is most commonly applied to the slurry water used at wet-process plants.” (Development Document for ELGs and NSPS for the Cement Manufacturing Point Source Category, January 1974, US EPA EPA-440/1-74-005-a).

• process waste water means any water which, during manufacturing or processing, comes into direct contact with or results from the production or use of any raw material, intermediate product, finished product, by-product, or waste product [40 CFR 401.11(q)].

• noncontact cooling water means water used for cooling which does not come into direct contact with any raw material, intermediate product, waste product or finished product [40 CFR 401.11(n)].

The prohibition on discharging process water will be maintained with this permit renewal.

Applicability to Subpart C Monitoring for compliance with Subpart C Materials Storage Piles Runoff effluent limits must be conducted prior to mixing with any non-regulated discharge such as ground water or non-contact cooling water. Although there is non-regulated discharge into the north and south ponds (mostly noncontact cooling water), Outfalls 001 and 002 are the most representative locations to demonstrate compliance with Subpart C Materials Storage Piles Runoff, for the following reasons:

• These two outfalls are the only locations that include all regulated plant storm water (storm water that contacts storage piles for material used in or derived from the manufacture of cement; specifically: coke, limestone, gypsum, and slag).

• These two locations are the first post-treatment areas that encompass all regulated storm water. There is no other location that accurately represents TSS and pH for regulated storm water after all treatment is complete.

• Storm water is anticipated to be the majority of the wastewater, with less than 20 gpm from non-regulated sources.

Table 4 presents the ELGs contained in Subpart C Materials Storage Piles Runoff. Ash Grove was constructed in 1962 and is considered an existing source (constructed prior to 1974); therefore, best practicable control technology (BPT) and best conventional pollutant control technology (BCT) apply:


Table 4. Cement Manufacturing ELGs (Subpart C)

Effluent Characteristic Effluent Limitations (1) Regulatory Req. Total Suspended Solids Not to exceed 50 mg/L 40 CFR 411.32 BPT &

40 CFR 411.37 BCT pH Within the range of 6.0 to 9.0 Footnotes: (1) Any untreated overflow from facilities designed, constructed and operated to treat the volume of runoff from materials storage piles which is associated with a 10-year, 24-hour rainfall event shall not be subject to the pH and TSS limits.

As noted above, untreated overflow from facilities designed, constructed and operated to treat the volume of runoff from materials storage piles which is associated with a 10-year, 24-hour rainfall event are exempt from pH and TSS limitations. The term 10-year, 24-hour rainfall event means “a rainfall event with a probable recurrence interval of once in ten years as defined by the National Weather Service in Technical Paper No. 40, ‘Rainfall Frequency Atlas of the United States,’ May 1961, and subsequent amendments, or equivalent regional or state rainfall probability information developed therefrom.” The 10-year, 24-hour rainfall event for this area is 2.0 inches [NOAA, Precipitation-Frequency Analysis of the Western United States, 1973].

Historically DEQ has recognized the ‘rainfall event’ exemption for both Outfalls 001 & 002; with this renewal DEQ will continue to do so only for Outfall 001. Ash Grove does not have a storm water treatment facility capable of treating runoff from the gypsum pile. Therefore, the pH and TSS overflow exemption will not apply to Outfall 002. The discharge from Outfall 001 continues to be exempt from the pH or TSS effluent limits for discharges due to overflow during a rainfall event at or greater than 2.0 inches in 24 hours. Ash Grove will be required to submit information on the amount of precipitation in addition to the relevant DMRs, as described in the Special Conditions section.

C. Mass-based Limits

All pollutants limited in permits must have limits expressed in terms of mass except for pH, temperature, or other pollutants which cannot appropriately be expressed by mass, or when applicable standards and limits are expressed in terms of other units of measurement.

As part of the 2010-issued permit DEQ determined that mass limits were not necessary; however, monthly TSS nondegradation load allocations (as lb/day average monthly loads) were calculated for each outfall. With this renewal, the most stringent past or current average monthly mass-based TSS load allocation will be incorporated as an average monthly limit (also see Part III.D).

The current TSS mass-based loads are re-calculated in this Fact Sheet considering the flow changes made as part of this permit renewal (mgd) and the 50 mg/L TSS TBEL.


Outfall 001 Estimated Reasonable Measure of Actual Flow (since no actual flow has occurred): 0.0012 mgd estimated maximum discharge from Outfall 001 (Form 2C) + 0.0060 mgd from Outfall 003 diversion (DMR - maximum average monthly) = 0.0072 mgd

2018 calculated mass-based load (and nondegradation load allocation): 0.0072 mgd x 50 mg/L x 8.34 conversion factor = 3.0 lb/day TSS

Outfall 002 Reasonable Measure of Actual Flow: 0.0125 mgd DMR maximum average monthly flow (2014-2018)

2018 calculated mass-based load (and nondegradation load allocation): 0.0125 mgd x 50 mg/L x 8.34 conversion factor = 5.2 lb/day TSS

D. Nondegradation

Sources that comply with conditions of the permit and do not exceed the limits established in the permit, or as determined from a permit previously issued by DEQ, are not considered new or increased sources. Any increase above this amount is subject to the provisions of the Nondegradation Policy (75-5-303, MCA).

Ash Grove was constructed in 1962 and is an existing source. As part of the 2010-issued permit, DEQ calculated the following mass-based TSS load allocations based on a reasonable measure of actual flow:

Outfall 001: 0.043 mgd x 50 mg/L x 8.34 conversion factor = 17.9 lb/day TSS

Outfall 002: 0.049 mgd x 50 mg/L x 8.34 conversion factor = 20.4 lb/day TSS

Outfall 003: 0.080 mgd x 50 mg/L x 8.34 conversion factor = 33.4 lb/day TSS (Outfall 003 is removed with this permit renewal.)

Actual loads discharged by the facility from Outfall 001 and 002 are based on DMR data for this period of record are compared to the nondegradation load allocations developed in 2010 (Table 5):


Table 5. Comparison of TSS Nondegradation Loads with Actual Loads (1) Outfalls Allocated

Load Average Actual Load

(lb/day) (lb/day) 2011 2012 2013 2014 2015 2016 2017

Outfall 001 17.9 0 0 0 0 0 0 0 Outfall 002 20.4 0.04 0.2 NA (2) Outfall 003 33.4 12.1 ND ND ND NA (3) NA NA

Footnotes: NA = Not applicable. ND = No data. (1) Average actual loads calculated only during times of discharge. (2) In November 2012, the required monitoring for TSS switched from Outfall 002 to Outfall 002A

(internal monitoring point). This internal monitoring location was not subject to nondegradation.

(3) Outfall 003 has had no discharge since it was plugged in 2015.

E. Proposed TBEL Effluent Limitations

The proposed TBELs for Outfalls 001 & 002 are presented in Tables 6 & Table 7:

Table 6. Proposed TBEL Effluent Limitations for Outfall 001 Parameter Units Effluent Limitations

Average Monthly Maximum Daily

Total Suspended Solids mg/L 50 (1) 50 (1) lb/day 3.0 (2) NA

pH s.u. Within the range of 6.0 to 9.0 (1) Footnotes: (1) Ash grove is not subject to these effluent limits contingent on demonstration of an overflow during a

10-year 24-hour rain event. (2) Compliance demonstrated by averaging the calculated daily loads (lb/day), exclusive of eligible

exceptions for rain events.

Table 7. Proposed TBEL Effluent Limitations for Outfall 002 Parameter Units Effluent Limitations


Total Suspended Solids mg/L 50 50 lb/day 5.2 (1) NA

pH s.u. Within the range of 6.0 to 9.0 Footnotes: (1) Compliance with average monthly limits demonstrated by averaging the calculated daily loads

(lb/day).


IV. Proposed Water Quality-based Effluent Limits (WQBEL)

A. Scope and Authority

Permits are required to include Water Quality-based Effluent Limits (WQBELs) when TBELs are not adequate to protect state water quality standards. Montana water quality standards define both water use classifications for all state waters and numeric and narrative standards that protect those designated uses. No wastes may be discharged that can reasonably be expected to violate any state water quality standards.

B. Receiving Water

Ash Grove discharges to Prickly Pear Creek. The water use classification for Prickly Pear Creek at the point of discharge is B-1. Waters classified B-1 are to be maintained suitable for drinking, culinary and food processing purposes, after conventional treatment; bathing, swimming and recreation; growth and propagation of salmonid fishes and associated aquatic life, waterfowl and furbearers; and agricultural and industrial water supply. Degradation that will impact established beneficial uses is not allowed.

Prickly Pear Creek is located within the Upper Missouri watershed as identified on United States Geological Survey (USGS) Hydrological Unit Code 10030101. Prickly Pear Creek at the discharge is identified as Montana Stream Segment MT41I006_040 “Prickly Pear Creek, Lump Gulch to County Road Wylie Drive.” This segment is listed on the 2016 and draft 2018 Integrated Reports as not fully supporting drinking water and aquatic life (see Table 8). Probable causes and sources of impairment are:

Table 8. Prickly Pear Creek Probable Causes and Sources of Impairment Cause Probable Sources

Alteration in stream-side or littoral vegetative covers

Highways, Roads, Bridges, Infrastructure (New Construction), Channelization

Arsenic Impacts from Abandoned Mine Lands (Inactive), Acid Mine Drainage, Contaminated Sediments

Cadmium Acid Mine Drainage, Contaminated Sediments, Impacts from Abandoned Mine Lands (Inactive)

Copper Acid Mine Drainage, Impacts from Abandoned Mine Lands (Inactive), Contaminated Sediments

Lead Impacts from Abandoned Mine Lands (Inactive), Acid Mine Drainage, Contaminated Sediments

Physical substrate habitat alterations

Contaminated Sediments, Channelization, Highways, Roads, Bridges, Infrastructure (New Construction), Industrial Point Source Discharge

Sedimentation-Siltation Industrial Point Source Discharge, Highways, Roads, Bridges, Infrastructure (New Construction), Contaminated Sediments

Temperature Water Diversions, Loss of Riparian Habitat Zinc Impacts from Abandoned Mine Lands (Inactive), Contaminated

Sediments, Acid Mine Drainage


DEQ completed the following Total Maximum Daily Load (TMDL) Report for the Lake Helena Planning area, which includes Prickly Pear Creek:

• Water Quality Restoration Plan TMDLs for the Lake Helena Planning Area, Volume I – Watershed Characterization and Water Quality Status Review, December 30, 2004

• Water Quality Restoration Plan TMDLs for the Lake Helena Planning Area, Volume II – Final Report, August 31, 2006.

• Lake Helena Planning Area Metals TMDL Addendum, September 2013 (does not include Prickly Pear Creek).

The 2006 TMDL developed water quality goals for most of the probable causes of impairment (arsenic, cadmium, copper, lead, zinc, and siltation) as well as thermal modification. The specifics will be discussed in Section IV.E.

The closest USGS gaging station on Prickly Pear Creek is station number 06061500 near Clancy, located approximately two miles upstream from Ash Grove. Based on the updated 2015 USGS report, the 7-day average low flow expected to occur on average once in 10 years (7Q10) is 7.75 cfs (5.0 mgd). The seasonal 14-day average low flow expected every five years (14Q5) is 11.8 cfs (7.6 mgd).

Table 9 summarizes the ambient water quality in Prickly Pear Creek, based on data from:

• USGS – USGS station 06061500 (2000 – 2013)

• EPA – Station R8MONTWQ-P-0.5 (2010)

• MDEQ1 – Station MDEQ_WQ_WQX-M09PRPEC01 (2001 – 2014)

• MDEQ2 – Station MDEQ_WQ_WQX-M09PKPRC13 (2012)

• MDEQ3 – Station MDEQ_WQ_WQX-M09PKPRC15 (2012)


Table 9. Prickly Pear Creek- Ambient Water Quality Monitoring Data

Parameter Units 75th Percentile

Number Samples

Monitoring Data Source

Hardness mg/L 71.4 (1) 23 USGS 2000 - 2003, EPA, MDEQ1, MDEQ2

pH s.u. 8.2 24 USGS 2002 - 2003, EPA, MDEQ1, MDEQ2, MDEQ3

Temperature °C 12.0 67 USGS 2007 – 2013, EPA, MDEQ1, MDEQ2, MDEQ3

Aluminum, Dissolved µg/L < 30 (2) 5 USGS 2000- 2001, EPA, MDEQ2 Arsenic, Total Recoverable µg/L 7.0 21 USGS 2000 – 2003, EPA, MDEQ1 Cadmium, Total Recoverable µg/L 0.31 21 USGS 2000 – 2003, EPA, MDEQ1 Copper, Total Recoverable µg/L 5.9 21 USGS 2000 – 2003, EPA, MDEQ1 Iron, Total Recoverable µg/L 305 6 USGS 2000 – 2001, EPA, MDEQ1 Lead, Total Recoverable µg/L 10.0 20 USGS 2000 – 2003, EPA, MDEQ1 Zinc, Total Recoverable µg/L 106 21 USGS 2000 – 2003, EPA, MDEQ1 Sulfate, Dissolved mg/L 51.8 14 USGS 2000 – 2003, MDEQ1 Chloride, Dissolved mg/L 2.6 2 MDEQ1 Nitrate + Nitrite (Dissolved) mg/L 0.13 15 USGS 2000 – 2003 Total Nitrogen as N (summer (3)) mg/L 0.27 5 USGS (2000 – 2003) Total Phosphorus as P (summer(3)) mg/L 0.020 6 USGS (2000 – 2003), MDEQ1 Footnote: ND = nondetect (1) Hardness is the 25th percentile, based on ‘Hardness, Ca, Mg.’ (2) DEQ calculated the 75th percentile using the detection limit as the result for any nondetects. The symbol “<” indicates

the result is based on nondetects. (3) Summer is July 1st – September 30th to conform with the nutrient criteria in Circular DEQ-12A.

C. Applicable Water Quality Standards

Discharges to surface waters classified B-1 are subject to the specific water quality standards of ARM 17.30.623, Department Circulars DEQ-7, DEQ-12A, and DEQ-12B, as well as the general provision of ARM 17.30.635 through 637. In addition to these standards, dischargers are also subject to mixing zones and nondegradation requirements.

Table 10 summarizes the relevant water quality standards for Prickly Pear Creek:


Table 10 – Prickly Pear Creek Water Quality Standards

Parameter Units Acute Aquatic Life Standard

Chronic Aquatic Life Standard

Human Health Standard

(Nutrients) pH, change s.u. 0.5 increase or decrease Temperature, change °F 2° increase or decrease Aluminum, Dissolved µg/L 750 87 NA Arsenic, Total Recoverable µg/L 340 150 10 Cadmium, Total Recoverable µg/L 1.4 (2) 0.6 (2) 5 Copper, Total Recoverable µg/L 10.2 (2) 7.0 (2) 1,300 Iron, Total Recoverable µg/L NA 1,000 NA Lead, Total Recoverable µg/L 53 (2) 2.1 (2) 15 Zinc, Total Recoverable µg/L 90 (2) 90 (2) 7,400 Sulfate (3) mg/L 500 NA 500 Nitrate + Nitrite (NO3 + NO2), Total as N mg/L NA NA 10

Total Nitrogen as N (summer) (4) mg/L NA NA (0.30) Total Phosphorus as P (summer)(4) mg/L NA NA (0.03) Footnotes: (NA = not applicable) (1) Based on 75th percentile of 8.2 s.u. and 12.0° Celsius. (2) Based on 25th percentile of 71.4 mg/L hardness. (3) Sulfate criteria are based on translation of the narrative condition as presented in DEQ’s “Translation

and Guidance on Application of the Montana Narrative Water Quality Criterion for Sulfate,” September 2014. Sulfate criteria expressed as total recoverable.

(4) Total Nitrogen and Total Phosphorus criteria in Circular DEQ-12A (Middle Rockies) applicable during the summer season of July 1st – September 30th.

In addition, DEQ incorporates the TMDL-developed waste load allocations (WLAs) for point sources into the appropriate discharge permits. The Lake Helena Watershed TMDL was completed in 2006. Ash Grove did not receive a site-specific WLA.

D. Mixing Zone

A mixing zone is an area where the effluent mixes with the receiving water and certain water quality standards may be exceeded. No mixing zone will be granted that will impair beneficial uses. In addition, the discharge must comply with the general prohibitions of ARM 17.30.637(1) which require that state waters, including mixing zones, must be free from substances which will:

1. settle to form objectionable sludge deposits or emulsions beneath the surface of the water or upon adjoining shorelines;


2. create floating debris, scum, a visible oil film (or be present in concentrations at or in

excess of 10 milligrams per liter) or globules of grease or other floating materials;

3. produce odors, colors or other conditions that create a nuisance or render undesirable tastes to fish flesh or make fish inedible;

4. create concentrations or combinations of materials which are toxic or harmful to human, animal, plant or aquatic life; and

5. create conditions which produce undesirable aquatic life.

Although certain standards may be exceeded in the mixing zone, an effluent in its mixing zone may not block passage of aquatic organisms nor may it cause acutely toxic conditions. Acute water quality standards may not be exceeded in any portion of the mixing zone unless DEQ finds that allowing minimal initial dilution will not threaten or impair existing uses. Aquatic life acute, aquatic life chronic, and human health standards (HHS) may not be exceeded outside of the mixing zone.

A standard mixing zone may be granted for facilities which discharge less than one mgd. The dilution ratio for Ash Grove is calculated for each outfall as the ratio of the Prickly Pear Creek 7Q10 (5.0 mgd) to the maximum average monthly discharge rate observed during the previous period of record:

• Outfall 001 = 5.0 mgd : 0.0072 mgd = 694 : 1

• Outfall 002 = 5.0 mgd : 0.0125 mgd = 400 : 1.

DEQ did not evaluate a mixing zone previously. Based on the dilution ratio, Ash Grove may qualify for a standard mixing zone with 100% dilution considered for chronic and human health standards; upon receipt of a mixing zone request that includes the required water quality assessment DEQ can evaluate the applicability of a mixing zone and determine the appropriate chronic/human health and acute dilution granted (see Special Conditions Part VII.D. of this fact sheet).

E. Basis and Proposed Water Quality-based Effluent Limitations

DEQ develops WQBELs for any pollutant for which there is Reasonable Potential (RP) to cause or contribute to exceedances of instream numeric or narrative water quality standards, after application of any approved mixing zones. DEQ assesses RP for each pollutant of concern (POC). Pollutants and parameters are identified as POC for one or more of the following reasons: because they have listed TBELs; were identified as needing limits in the previous permit; are identified as present in the effluent through monitoring or otherwise expected present in the discharge; or are pollutants associated with impairment which may or may not have a Wasteload Allocation (WLA) in a TMDL. Table 11 lists the basis for listing each POC for Ash Grove.


Table 11: Identification of Ash Grove Parameters of Concern

Parameter Basis for Identifying as POC

TSS, pH TBELs, Previous Permit Limits, TMDL (sediment) Oil & Grease Expected Present Temperature TMDL Sulfate Known Present Dissolved aluminum; total recoverable iron

Expected Present (calcium silicate clinker can contain aluminum and de-zinced slag is an iron source)

Total recoverable arsenic, cadmium, copper, lead, and zinc

TMDL, Known Present

Nitrate + Nitrite, Total Nitrogen Known Present

WQBELs are required for all pollutants which demonstrate RP to exceed numeric or narrative standards. Based on the method developed in the EPA’s 1991 Technical Support Document for Water Quality-based Toxics Control (TSD), DEQ may use a mass balance equation for both the RP evaluation and WQBEL development (see Equation 1).

QrCr = QsCs + QdCd (Equation 1) Given:

Qr = the resulting receiving water flow after mixing

Cr = the resulting receiving water concentration

Qs = critical receiving water low flow (available dilution of 7Q10 or seasonal 14Q5)

Cs = critical ambient pollutant concentration (Prickly Pear Creek 75th percentile)

Qd = critical discharge rate (for non-POTWs the maximum actual flow)

Cd = critical discharge pollutant concentration (maximum discharge concentration x TSD multiplier)

The critical conditions for Ash Grove that would determine the values for the variables (Qs, Cs, Qd, and Cd) used in Equation 1 are further discussed below.

1. Critical Stream Flow (Qs)

Critical stream flow is based on the available part of the low flow (7Q10 or 14Q5) considering allowable dilution. As discussed in Part IV.B of this fact sheet, DEQ determined the low flows for Prickly Pear Creek are a 7Q10 of 5.0 mgd and a seasonal 14Q5 flow of 7.6 mgd. As discussed in Part IV.D, upon receipt of a mixing zone request that includes the required water quality assessment DEQ can evaluate the applicability of a mixing zone and determine the appropriate chronic/human health and acute dilution granted (see Special Conditions Part VII.D. of this fact sheet).


2. Critical Background Receiving Water Pollutant Concentration (Cs)

The critical pollutant concentration is the 75th percentile concentration for each parameter in the receiving water. The data collected from Prickly Pear Creek are summarized in Table 9. DEQ prefers at least 10 upstream data points that are no more than ten years old.

3. Critical Discharge Flow (Qd)

DEQ uses the maximum 30-day (monthly) average observed for review of the chronic condition, and the maximum daily flow for review of the acute condition as a reasonable approximation of actual flows. For this facility, current Qd values are: • Outfall 001 – 0.0072 mgd chronic and 0.014 mgd acute (estimated) • Outfall 002 – 0.0125 mgd chronic and 0.0317 mgd acute (DMR values 2014-2018)

4. Critical Discharge Pollutant Concentrations (Cd)

The critical discharge concentration is based on the estimation procedures described in TSD to estimate the 95th percentile of the daily values. The critical effluent concentration equals the maximum effluent concentration reported by the facility multiplied by the TSD multiplier. DEQ prefers at least 10 effluent data points that are no more than five years old. There were eight discharge samples for most parameters for Outfall 002 (only one sample for nitrate+nitrite). There was no data for Outfall 001 since there has been no discharge from Outfall 001 since 1996.

Reasonable Potential Analysis Reasonable potential for a pollutant to cause or contribute to an exceedance of a water quality standard can be assessed either numerically or narratively. DEQ evaluates RP numerically using Equation 2:

Cr = QdCd + QsCs (Equation 2) Qd + Qs

The applicable water quality standards that would be used to compare against the critical resulting receiving water concentration (Cr) are summarized in Table 10. Any parameter with Cr > water quality standard has RP.

Calculation of WQBELs The pollutant discharge concentration that may be assimilated without exceeding the applicable water quality standard is referred to as the wasteload allocation (WLA). The acute and chronic WLAs for each parameter may be calculated by setting the receiving water pollutant concentration equal to the water quality standard and re-arranging the mass-balance equation to solve for the allowable effluent concentration as shown in Equation 3:

Cd = CWLA = QrCr - QsCs (Equation 3) Qd


The acute and chronic WLAs would then be translated into average monthly limitations (AMLs) and maximum daily limitations (MDLs) using TSD multipliers.

The following summarizes the RP analyses and WQBELs in this permit.

TSS - The facility provides a significant reduction in solids through settling as required by the TBEL (Section III).

Prickly Pear Creek is listed on the 2016 and Draft 2018 Integrated Reports as impaired for sedimentation-siltation, but the four largest sources for this stream segment were identified as agriculture, streambank erosion, unpaved roads, and timber harvest which cumulatively account for over 90% of the anthropogenic nonpoint siltation load of ~21,000 tons/year. Ash Grove was not specifically identified as a point (or nonpoint) source; the sum of all point sources was estimated at 54 tons/year with no reduction required. DEQ finds that the TBEL for TSS is sufficient; no additional WQBEL will be required.

pH – The current permit restricts effluent pH to between 6.0 – 9.0 s.u. There was no discharge from Outfall 001. The range of pH from Outfall 002 was 7.6 – 8.5 s.u. The facility is required to maintain a pH of 6.0 – 9.0 as part of the TBEL (Section III). In addition, the water quality standard requires that:

the induced variation of hydrogen ion concentration (pH) within the range of 6.5 to 8.5 must be less than 0.5 pH unit. Natural pH outside this range must be maintained without change. Natural pH above 7.0 must be maintained above 7.0.

No additional pH restriction is necessary.

Oil and grease - state surface waters must be free from substances attributable to municipal, industrial, agricultural practices or other discharges that will create floating debris, scum, a visible oil film (or be present in concentrations at or in excess of 10 milligrams per liter), or globules of grease or other floating materials.

The effluent limit for oil and grease in the previous permit was “no discharge which causes visible oil sheen in the receiving stream.” Weekly visual and semi-annual monitoring was required. None of the monitoring showed any oil present in the discharge. However, Ash Grove has various mechanical equipment and trucks that could leak oil or grease. Visual monitoring for oil and grease will be required; if oil and grease is observed Ash Grove will be required to analyze a sample to ensure the discharge concentration is less than 10 mg/L, or discontinue the discharge.

Temperature – a discharge to waters classified as B-1 cannot increase the naturally occurring temperature:

a. By 1 °F when the naturally occurring receiving water is 32-66 °F; b. Above 67 °F when the naturally occurring receiving water is 66-66.5 °F; or c. More than 0.5 °F when the naturally occurring receiving water is 66.5 °F or higher.

Prickly Pear Creek is listed on the 2016 and Draft 2018 Integrated Reports as impaired for temperature, but the sources are identified as water diversions and loss of riparian habitat.


The TMDL (Volume II, 2006) temperature goal for Prickly Pear Creek at the Wylie Drive bridge is 67.0 °F and the current average stream temperature is 69.2 °F; which required a 2.2 °F reduction in stream temperature. However, the TMDL document recognizes that riparian degradation and flow augmentation are the solutions that should be addressed. Therefore, no temperature monitoring or limit was included in the 2010-issued permit and is not proposed for this permit.

Sulfates – Ash Grove stores sulfate-containing (SO4-2) materials (gypsum) which is

exposed to storm water discharged through Outfall 002. Ash Grove monitored the discharge from Outfall 002 for sulfates semi-annually during the previous permit cycle. The sulfate concentration in the discharge ranged from 131 mg/L to 827 mg/L for the eight samples reported on monthly DMRs between January 2014 and February 2018.

DEQ does not have a numeric water quality standard for sulfate in Circular DEQ-7. However, DEQ issued the “Translation and Guidance on Application of the Montana Narrative Water Quality Criterion for Sulfate,” in September 2014 which provides guidance on developing numeric standards for sulfate. For this stretch of Prickly Pear Creek, the water quality criteria are: • Acute aquatic life: 500 mg/L, based on the Guidance and the ambient Prickly Pear

Creek hardness < 100 mg/L and chloride < 5 mg/L. • Chronic aquatic life: None because the ambient hardness is > 50 mg/L. • Human health: 500 mg/L. Ash Grove had only eight effluent samples for sulfate. Furthermore, the ambient sulfate data is over 15 years old and Ash Grove has not made a mixing zone request or submitted a water quality assessment. Because there is no actual effluent data for Outfall 001 and limited data for Outfall 002, and because additional information is needed to consider a mixing zone, DEQ has required additional effluent and upstream sampling and has included Special Conditions to address mixing zones in Part VII.

Nitrate + Nitrite – Nitrate and nitrite are toxic components of total nitrogen. The human health standard for N+N is 10 mg/L. Ash Grove uses ammonium nitrate/fuel oil blasting agents in their quarries, which could be a potential source of N+N in their discharge. However, Ash Grove had only one effluent sample for N+N. Furthermore, Ash Grove has not made a mixing zone request or submitted a water quality assessment. Because there is no actual effluent data for Outfall 001 and limited data for Outfall 002, and because additional information is needed to consider a mixing zone, DEQ has required additional effluent and upstream sampling and has included Special Conditions to address mixing zones in Part VII.

Total Nitrogen – Total nitrogen (TN) is a nutrient which can lead to excessive algal and aquatic vegetation growth. Based on Department Circular DEQ-12A, the TN standard for Prickly Pear Creek is 0.30 mg/L (July 1st – September 30th). The critical ambient concentration for this stretch of Prickly Pear Creek during that timeframe is 0.27 mg/L. Ash Grove uses ammonium nitrate/fuel oil blasting agents in their quarries, which could be


a potential source of TN in their discharge. However, Ash Grove was not previously required to monitor for TN and therefore there is no discharge data. Monitoring will be required for the next permit cycle.

Toxic Metals – Prickly Pear Creek is listed on the 2016 and Draft 2018 Integrated Reports as impaired for total recoverable arsenic, cadmium, copper, lead, and zinc. The TMDL (Volume II, 2006) metals goal for Prickly Pear Creek focused on reductions in abandoned mines; there was no proposal for load reduction for point sources or quarries. Ash Grove was required to monitor semi-annually for the term of this 2010-issued permit for these metals as well as total recoverable iron and dissolved aluminum that were expected to be present due to their presence in raw materials.

Even with limited available information, DEQ was able to eliminate three metals from further evaluation due to the fact that the highest of eight discharge samples and the 75th percentile of the ambient concentrations were below the lowest water quality standard.

Parameter Units Lowest Standard

Maximum Discharge

Value

Number of Discharge Samples

75th percentile Ambient

Number of Ambient Samples

Aluminum, Dissolved µg/L 87 < 30 8 < 30 5 Cadmium, Total Recoverable µg/L 0.6 0.3 8 0.3 21

Iron, Total Recoverable µg/L 1,000 430 8 305 6

The following discusses the four metals that require additional information:

Arsenic - The arsenic concentration for eight discharge samples ranged from 5.0 to 12 µg/L; DEQ prefers to have at least ten samples in order to calculate the critical discharge concentration in accordance with the TSD method. The 75th percentile ambient arsenic concentration was 7.0 µg/L; however, the 21 samples were 14 to 18 years old. Additional monitoring will be required for this permit cycle. In addition, Ash Grove is required to supply the mixing zone assessment information if applying for dilution credit for this parameter.

Copper, Total Recoverable - The copper concentration for eight discharge samples ranged from < 1.0 to 60 µg/L; DEQ prefers to have at least ten samples in order to calculate the critical discharge concentration in accordance with the TSD method. The 75th percentile ambient copper concentration was 5.9 µg/L; however, the 21 samples were 14 to 18 years old. Additional monitoring will be required for this permit cycle. In addition, Ash Grove is required to supply the mixing zone assessment information if applying for dilution credit for this parameter.

Lead, Total Recoverable - The lead concentration for eight discharge samples ranged from < 0.5 to 1.3 µg/L; DEQ prefers to have at least ten samples in order to calculate the critical discharge concentration in accordance with the TSD method. The 75th percentile ambient lead concentration was 10 µg/L; however, the 20 samples were 14 to 18 years old.


Additional monitoring will be required for this permit cycle. In addition, Ash Grove is required to supply the mixing zone assessment information if applying for dilution credit for this parameter.

Zinc, Total Recoverable - The zinc concentration for eight discharge samples ranged from 17 to 69 µg/L; DEQ prefers to have at least ten samples in order to calculate the critical discharge concentration in accordance with the TSD method. The 75th percentile ambient zinc concentration was 106 µg/L; however, the 21 samples were 14 to 18 years old. Additional monitoring will be required for this permit cycle. In addition, Ash Grove is required to supply the mixing zone assessment information if applying for dilution credit for this parameter.

Whole Effluent Toxicity (WET) – state waters are required to be free from substances attributable to discharges that create conditions that are harmful or toxic to human, animal, plant or aquatic life. Ash Grove is a minor discharger that discharges dilute wastewater and storm water. Portland cement manufacture is not listed as a primary industrial category. No WET testing will be required in the renewed permit.

V. Final Effluent Limitations

Beginning on the effective date of this permit and lasting through the term of the permit, the quality of effluent discharged by the facility from Outfalls 001 and 002 shall, as a minimum, meet the limits as set forth below in Tables 12 & 13:

Table 12. Proposed Effluent Limitations for Outfall 001 Parameter Units Effluent Limitations


Total Suspended Solids mg/L 50 (1) 50 (1) lb/day 3.0 (2) NA

pH s.u. Within the range of 6.0 to 9.0 (1) Footnotes: (1) These effluent limits are not applicable with demonstration of an overflow during a 10-year 24-hour

rain event. (2) Compliance demonstrated by averaging the calculated daily loads (lb/day), exclusive of eligible

exceptions for rain events.


Table 13. Proposed Effluent Limitations for Outfall 002 Parameter Units Effluent Limitations


Total Suspended Solids mg/L 50 50 lb/day 5.2 (1) NA

pH s.u. Within the range of 6.0 to 9.0 Footnotes: (1) Compliance with average monthly limits demonstrated by averaging the calculated daily loads

(lb/day).

There shall be no discharge of floating solids or visible foam in other than trace amounts.

There shall be no discharge which causes visible oil sheen in the receiving water (or be present in concentrations at or in excess of 10 milligrams per liter).

Ash Grove is not allowed to discharge any wastewater that is defined as “Process Water” under 40 CFR 411 Subpart A without applying for a permit modification.

VI. Monitoring Requirements

Outfalls 001 & 002 Starting with the effective date of the permit and lasting for the duration of the permit cycle, self-monitoring of the effluent shall be conducted at the following locations, unless another location is requested and acknowledged by DEQ in writing:

• Outfall 001 – at the last point of control prior to Prickly Pear Creek, after all regulated storm water inputs (including pumped storm water from the previous Outfall 003 drainage) and treatment has occurred.

• Outfall 002 - at the last point of control prior to Prickly Pear Creek, after all regulated storm water inputs and treatment has occurred.

The permittee shall collect a grab sample within the first thirty minutes of discharge from Outfall 001 or Outfall 002 for any discharges which result from precipitation-related events. In the event storm water is detained at the facility and a discharge is manually released at a later date, the permittee must conduct all monitoring at the time of release, and record the most recent storm event information, including whether the sample was from snowmelt or rainfall, and if rainfall the estimated duration of the event sampled and measurements or estimates (in inches) of the rainfall event.

As an alternative to a single grab sample, the permittee may take a flow-weighted composite of either the entire discharge or the first three hours of the discharge. For flow-weighted composite, only one analysis of the composited aliquots is required. Flow weighted composite samples are not allowed for pH and oil and grease.


All analytical procedures must comply with the specifications of 40 CFR Part 136 and the analyses must have a detection or meet any Required Reporting Values (RRVs) listed in Circular DEQ-7, unless otherwise specified. Samples shall be collected, preserved and analyzed in accordance with approved procedures listed in 40 CFR Part 136. Samples will reflect the nature and effect of the discharge at the frequency presented in Table 14.


Table 14: Outfalls 001 & 002 Monitoring and Reporting Requirements (1)

Parameter Units Sample Type (2)

Min. Sample Frequency Reporting Metric RRV (3)

Flow mgd Instantaneous or Grab 3/Week Daily Maximum

Monthly Average

+/- 10%

Flow Duration days Calculated 3/Week Number of Days 1

Total Suspended Solids mg/L Grab 2/Month Daily Maximum Monthly Average NA

pH s.u. Instantaneous 3/Week Daily Maximum Daily Minimum NA

Oil Sheen Presence Observation 3/Week Present/Absent NA

Oil and Grease mg/L Grab (4) Value NA

Sulfates mg/L Grab 2/Month Daily Maximum Monthly Average NA

Ammonia, Total as N mg/L Grab Quarterly Value 0.07

Nitrate + Nitrite, as N – non-summer mg/L Grab

Quarterly Value 0.020

Nitrate + Nitrite, as N – summer 2/Month (5) Monthly Average 0.020

Total Kjeldahl Nitrogen mg/L Grab 2/Month (5) Monthly Average 0.225

Total Nitrogen, as N (5) mg/L Calculated 2/Month (5) Monthly Average NA

lbs/day Calculated 1/Month (5) Monthly Average NA

Arsenic, Total Recoverable μg/L Grab Quarterly Daily Maximum Monthly Average 1

Copper, Total Recoverable μg/L Grab 1/Month Daily Maximum Monthly Average 2

Lead, Total Recoverable μg/L Grab Quarterly Daily Maximum Monthly Average 0.3

Zinc, Total Recoverable μg/L Grab Quarterly Daily Maximum Monthly Average 8

Footnotes: (1) Monitoring only required during periods with discharge, and must be taken within the first 30 minutes of a discharge which

occurs in response to a rainfall or snowmelt event. See Definition section at end of permit for explanation of terms. (2) Ash Grove may take flow-weighted composite samples in lieu of grab samples. (3) See Circular DEQ-7 or DEQ-12A for more information on the Required Reporting Values (RRVs). Analysis must achieve these,

or lower, reporting limits or be sufficient to detect the parameter. Flow must be measured +/1 10% of actual discharge rates. (4) Oil & grease analysis must be conducted anytime a visual sheen is observed in the effluent. (5) Analysis for Total Nitrogen is twice per month during the summer months of July, August, and September; the samples must be

taken at least one week apart. Total Nitrogen is calculated by the sum of Total Kjeldahl Nitrogen plus Nitrate+Nitrite.


In addition to the above monitoring, Ash Grove must conduct monitoring required by Form 2C Section V to have the required data for the renewal package, including at least one analysis for: Part A - each parameter; Part B - each parameter believed present including Total Phosphorus; and Part C - each parameter believed present at > 10 µg/L.

Upstream

Upstream monitoring will be required as found in Table 15, below. Monitoring must take place at a consistent location upstream and outside the influence of the facility and identified on a topographic map or aerial photo submitted to DEQ.

Upstream monitoring will occur during for the three calendar years 2019, 2020, and 2021, with the sample type, frequency, and RRVs as identified below. The values shall be reported on the facility’s DMRs.

Table 15: Upstream Monitoring and Reporting Requirements (1)

Parameter Units Sample Type

Minimum Sample

Frequency (2)

Required Reporting Value (3)

Arsenic, Total Recoverable µg/L Grab Quarterly 1 Copper, Total Recoverable µg/L Grab Quarterly 2 Lead, Total Recoverable µg/L Grab Quarterly 0.3 Zinc, Total Recoverable µg/L Grab Quarterly 8 Sulfate, Total mg/L Grab Quarterly 1 Hardness, Total as CaCO3 mg/L Grab Quarterly 1 Total Nitrogen mg/L Grab Monthly (4) 0.245 Nitrate + Nitrite (N+N) mg/L Grab Monthly (4) 0.020 Total Kjeldahl Nitrogen (TKN) mg/L Grab Monthly (4) 0.225 Footnotes: (1) See Definition section at end of permit for explanation of terms. (2) Monitoring required for three (3) full years of permit coverage (2019, 2020, and 2021). (3) See Circular DEQ-7 and Circular DEQ-12A for more information on RRVs. Analysis must

achieve these, or lower, reporting limits. (4) Analysis for Total Nitrogen is during the summer months of July, August, and September.

Total Nitrogen is calculated by the sum of TKN plus N+N or by the persulfate method (in which case analysis of TKN and N+N is not required).

The permittee may choose to collect ambient (upstream) data for additional parameters during the permit term. Upstream data will be needed if the permittee will be seeking a mixing zone for that parameter.


VII. Special Conditions

A. 10-year 24-hour Rainfall Event – Outfall 001

If a rainfall event at or above the 10-year 24-hour rainfall event occurs, Ash Grove is not required to meet the TBEL effluent limits for Outfalls 001 (TSS and pH). However, Ash Grove is responsible for submitting, with any DMR that indicates such an occurrence, documentation that the precipitation event did exceed the 10-year 24-hour rainfall event. Acceptable methods of precipitation documentation include on-site rain gauge records or any official rainfall records from the National Weather Service.

B. Storm Water Pollution Prevention Plan (SWPPP) and Best Management Practices (BMPs)

Ash Grove shall maintain and follow a SWPPP to address the two outfalls covered under this permit. The SWPPP must comply with the SWPPP requirements in the most recent Multi-Sector General Permit for Storm Water Discharges Associated with Industrial Activity, Permit Number MTR000000, and address both structural and behavioral BMPs to minimize the discharge of pollutants.

C. Pollutant Source Reduction

Ash Grove shall investigate the source(s) of sulfate and total recoverable arsenic, copper, lead, and zinc and evaluate options for minimizing discharge of these pollutants. The evaluation shall cover both storm water and non-storm water, including settling vaults and holding pond clean out; control of gypsum; minimizing mill room pollutant entrainment in the wastewater; and general housekeeping procedures that could affect the quantity and quality of pollutants entering the wastewater.

Ash Grove shall submit a summary of this evaluation by no later than November 1, 2020, to DEQ. In addition to submittal of the report, Ash Grove may wish to arrange to meet with DEQ to discuss the progress to-date, and proposed future steps.

D. Mixing Zone Evaluation

Ash Grove must determine whether they want to request either a Standard Mixing Zone (ARM 17.30.516) or Source-Specific Mixing Zone (ARM 17.30.518) or do not want to request a mixing zone for the next permit renewal. Ash Grove shall inform DEQ by no later than November 1, 2020 of what actions they intend to take for defending the granting of additional dilution in evaluating RP and any future WQBELs. Ash Grove must submit the mixing zone request and any mixing zone study reports that comply with the requirements in the applicable mixing zone regulations by no later than 180 days prior to the expiration of this permit.


VIII. Public Participation

A. Public Notice

DEQ issued Public Notice No. MT-18-18 dated August 27, 2018. The public notice states that a tentative decision has been made to issue an MPDES permit to the Permittee and that a draft permit, fact sheet and environmental assessment (EA) have been prepared. Public comments are invited any time prior to the close of the business on September 26, 2018. Comments may be directed to:

Department of Environmental Quality Water Protection Bureau

PO Box 200901 Helena, MT 59620

or

[email protected]

All comments received or postmarked prior to the close of the public comment period will be considered in the formulation of the final permit. DEQ will respond to all substantive comments and issue a final decision within sixty days of the close of the public comment period or as soon as possible thereafter.

All persons, including the applicant, who believe any condition of a draft permit is inappropriate or that DEQ's tentative decision to deny an application, terminate a permit, or prepare a draft permit is inappropriate, shall raise all reasonably ascertainable issues and submit all reasonably available arguments supporting their position by the close of the public comment period (including any public hearing).

B. Notification of Interested Parties

Copies of the public notice were mailed to the discharger, state and federal agencies and interested persons who have expressed an interest in being notified of permit actions. A copy of the distribution list is available in the administrative record for this permit. In addition to mailing the public notice, a copy of the notice and applicable draft permit, fact sheet and EA were posted on DEQ’s website for 30 days.

Any person interested in being placed on the mailing list for information regarding this MPDES permit should contact DEQ, reference this facility, and provide a name, address, and email address.

C. Public Hearing

During the public comment period provided by the notice, DEQ will accept requests for a public hearing. A request for a public hearing must be in writing and must state the nature of the issue proposed to be raised in the hearing.


D. Permit Appeal

After the close of the public comment period DEQ will issue a final permit decision. A final permit decision means a final decision to issue, deny, modify, revoke and reissue, or, terminate a permit. A permit decision is effective 30 days after the date of issuance unless a later date is specified in the decision, a stay is granted, or the applicant files an appeal.

The Applicant may file an appeal within 30 days of DEQ’s action to the following address:

Secretary, Board of Environmental Review Department of Environmental Quality

1520 East Sixth Avenue PO Box 200901

Helena, Montana 59620-0901

E. Additional Information

Requests for additional information or questions regarding this permit should be directed to the Water Protection Bureau at 406-444-5546.


VIII. Information Sources

(1) Federal Water Pollution Control Act (Clean Water Act), 33 U.S.C. §§ 1251-1387.

(2) US Code of Federal Regulations, 40 CFR Parts 122-125, 130-133, & 136, and 411.

(3) Montana Code Annotated (MCA), Title 75-5-101, et seq., “Montana Water Quality Act.”

(4) Administrative Rules of Montana Title 17 Chapter 30 - Water Quality

• Subchapter 5 - Mixing Zones in Surface and Ground Water

• Subchapter 6 - Montana Surface Water Quality Standards and Procedures

• Subchapter 12 - MPDES Standards

• Subchapter 13 - MPDES Permits (5) Montana Department of Environmental Quality Circulars/Guidance:

• Circular DEQ-7, Montana Numeric Water Quality Standards, May 2017

• Circular DEQ-12A, Montana Base Numeric Nutrient Standards, July 2014

• Translation and Guidance on Application of the Montana Narrative Water Quality Criterion for Sulfate, September 2014

(6) MPDES Permit Number MT0000451: Administrative Record.

(7) Integrated 303(d)/305(b) Water Quality Report for Montana (2016/draft 2018), and: • Total Maximum Daily Load (TMDL) documents Water Quality Restoration Plan

TMDLs for the Lake Helena Planning Area, Volume I – Watershed Characterization and Water Quality Status Review, December 30, 2004

• Water Quality Restoration Plan TMDLs for the Lake Helena Planning Area, Volume II – Final Report, August 31, 2006.

• Lake Helena Planning Area Metals TMDL Addendum, September 2013; does not include Prickly Pear Creek.

(8) Western U.S. Precipitation Frequency Maps, National Weather Service, 1973 @ http://www.wrcc.dri.edu/pcpnfreq.html

(9) Streamflow characteristics based on data through water year 2009 for selected streamflow-gaging stations in or near Montana: U.S. Geological Survey Scientific Investigations Report 2015–5019–E, 10 p., McCarthy, P.M., 2016 (USGS, 2016)

(10) EPA NPDES Permit Writers’ Manual, EPA-833-B-96-003, September 2010.

(11) EPA. Technical Support Document for Water Quality based Toxics Control EPA/505/2-90-001. March 1991.

Prepared by: Christine Weaver Date: August 2018

http://www.wrcc.dri.edu/pcpnfreq.html

FIGURE 1: Ash Grove Site Outfall Locations

North Pond

South Pond

FIGURE 2: Ash Grove Water Flow