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Home My WebLink AboutNC0022098_Fact Sheet_20211109Cranbrook Village MHP WWTP – Renewal Fact sheet Page 1 of 7 NCDEQ / DWR /NPDES FACT SHEET FOR RENEWAL PERMIT NC0022098 Table 1 - Facility Information Applicant / Facility Name: Michael Brown, Owner / Paul Smith (ORC) Cranbrook Village MHP Applicant Address: 1150 Hungry Neck Blvd., Suite 359 Mount Pleasant, South Carolina Facility Address: 4309 Old Village Place, Greensboro Permitted Flow: 0.010 MGD Type of Waste / Treatment Summary: 100% Domestic no WET test / tablet disinfection Facility / Permit Status: Biological Grade II WPCS / Renewal County: Gilford County Miscellaneous Receiving Stream: Little Alamance Creek Regional Office: Winston-Salem (WSRO) Stream Class / Stream Index: WS-IV; NSW 16-19-3-(0.5) State / USGS Quad: C19SE / Greensboro, NC Instream Monitoring: No Permittee Contacts: Paul Smith (ORC) 336-932-9347 [smithindustries@bellsouth.net] 303(d) Listed? No Permit Writer: Joe R. Corporon, P.G. Basin: Cape Fear Date: 03Nov2021 Subbasin: 03-06-03 HUC: 030300020102 Drainage Area (mi2): ~ Lat. 36.004 N Long. 79.752 W s7Q10 (cfs) 0.0 w7Q10 (cfs) 0.0 Average Flow (cfs): 0.0 IWC (%): 100% FACILITY SUMMARY Cranbrook Village Mobile Park WWTP services a 100% domestic wastewater discharge generated by ~ 200 residences. Average Annual flow rate for the past two years 0.007 MGD. The treatment system design flow is 0.010 MGD, currently permitted at this capacity (see discharge data summary, Table 3). INSPECTION / CORRESPONDENCE O&M Recommendations, 29May2018 - This treatment system is showing significant signs of age and wear. The ladder to climb on top of the treatment system is severely rusted and potentially unsafe for the operator and inspector. The walkway is also severely rusted. The in -ground digester appears to be caving into some degree. The bar screen fell off the system at some point and has not been replaced, so the operator manually removes solids. These issues should be addressed soon before they impact treatment. Cranbrook Village MHP WWTP – Renewal Fact sheet Page 2 of 7 REASONABLE POTENTIAL ANALYSES (RPA) The permit renewal identified no parameters of concern (POCs) that required a reasonable potential analysis. Table 2 - COMPLIANCE HISTORY -Jan2019-Sep2021 NO INSTREAM MONITORING – receiving steam not impaired: Low permitted flow to named stream; Little Alamance Creek (17-19-3-(0.5) is Supporting; Good-Fair Bioclassification. Currently, no stream monitoring in the permit – no changes recommended. DMR DATA SUMMARY (JAN2018-JUN2021) Table 3 - Conventional Parameters: Effluent Characteristics Minimum Average Maximum Sample Count Flow (MGD) 0.0028 0.0064 0.010 145 BOD, 5-day, 20º C (mg/l) < 2 4.72 44.6 143 pH (standard units) 6.8 7.12 7.3 145 Temperature º C 1 17.78 31 693 Total Suspended Solids (mg/l) 2.1 5.20 16.8 144 Fecal Coliform (per 100 ml) 0.34 16.19 387 144 Total Nitrogen (TN) 1.1 12.26 37.87 9 Total Phosphorus (TP) 0.014 1.94 5.9 9 Total Residual Chlorine (TRC) < 6 6 6 289 Ammonia (NH3 as N) < 0.1 4.49 46.4 150 CORRECTIONS TO AMMONIA LIMITS Previous winter limits for Ammonia (as N) of 24.0 mg/L are incorrect. According to 15A NCAC 2B .0404(c), winter waste-load allocations for oxygen consuming waste shall not be less stringent than 2 times the summer limit. Considering previous summer limits of 3.8 mg/L MA, winter limits are hereby revised from 24.0 mg/L to 7.2 mg/L MA [see section A. (1.)]. Cranbrook Village MHP WWTP – Renewal Fact sheet Page 3 of 7 SUMMARY OF PROPOSED CHANGES • Adjusted winter MA limits for Ammonia from 24.0 to 7.2 mg/L • updated permit format • added to Class WW-II citation [section A. (1.) header] • updated eDMR requirements • updated site map PROPOSED SCHEDULE OF ISSUANCE Draft Permit to Public Notice: 09Nov2021 (est.) Permit Scheduled to Issue: 17Dec2021 (est.) Effective Date 01Feb2022 (est.) NPDES DIVISION CONTACT If you have questions about any of the above information, or on the attached permit, please email Joe R. Corporon, P.G. [joe.corporon@ncdenr.gov]. NAME: DATE: 03NOV20121 NPDES Implementation of Instream Dissolved Metals Standards – Freshwater Standards The NC 2007-2015 Water Quality Standard (WQS) Triennial Review was approved by the NC Environmental Management Commission (EMC) on November 13, 2014. The US EPA subsequently approved the WQS revisions on April 6, 2016, with some exceptions. Therefore, metal limits in draft permits out to public notice after April 6, 2016 must be calculated to protect the new standards - as approved. Table 5. NC Dissolved Metals Water Quality Standards/Aquatic Life Protection Parameter Acute FW, µg/l (Dissolved) Chronic FW, µg/l (Dissolved) Acute SW, µg/l (Dissolved) Chronic SW, µg/l (Dissolved) Arsenic 340 150 69 36 Beryllium 65 6.5 --- --- Cadmium Calculation Calculation 40 8.8 Chromium III Calculation Calculation --- --- Chromium VI 16 11 1100 50 Copper Calculation Calculation 4.8 3.1 Lead Calculation Calculation 210 8.1 Nickel Calculation Calculation 74 8.2 Silver Calculation 0.06 1.9 0.1 Zinc Calculation Calculation 90 81 Cranbrook Village MHP WWTP – Renewal Fact sheet Page 4 of 7 Table 1 Notes: 1. FW= Freshwater, SW= Saltwater 2. Calculation = Hardness dependent standard 3. Only the aquatic life standards listed above are expressed in dissolved form. Aquatic life standards for Mercury and selenium are still expressed as Total Recoverable Metals due to bioaccumulative concerns (as are all human health standards for all metals). It is still necessary to evaluate total recoverable aquatic life and human health standards listed in 15A NCAC 2B.0200 (e.g., arsenic at 10 µg/l for human health protection; cyanide at 5 µg/L and fluoride at 1.8 mg/L for aquatic life protection). Table 2. Dissolved Freshwater Standards for Hardness-Dependent Metals The Water Effects Ratio (WER) is equal to one unless determined otherwise under 15A NCAC 02B .0211 Subparagraph (11)(d) Metal NC Dissolved Standard, µg/l Cadmium, Acute WER*{1.136672-[ln hardness](0.041838)} ∙ e^{0.9151 [ln hardness]-3.1485} Cadmium, Acute Trout waters WER*{1.136672-[ln hardness](0.041838)} ∙ e^{0.9151[ln hardness]-3.6236} Cadmium, Chronic WER*{1.101672-[ln hardness](0.041838)} ∙ e^{0.7998[ln hardness]-4.4451} Chromium III, Acute WER*0.316 ∙ e^{0.8190[ln hardness]+3.7256} Chromium III, Chronic WER*0.860 ∙ e^{0.8190[ln hardness]+0.6848} Copper, Acute WER*0.960 ∙ e^{0.9422[ln hardness]-1.700} Copper, Chronic WER*0.960 ∙ e^{0.8545[ln hardness]-1.702} Lead, Acute WER*{1.46203-[ln hardness](0.145712)} ∙ e^{1.273[ln hardness]- 1.460} Lead, Chronic WER*{1.46203-[ln hardness](0.145712)} ∙ e^{1.273[ln hardness]- 4.705} Nickel, Acute WER*0.998 ∙ e^{0.8460[ln hardness]+2.255} Nickel, Chronic WER*0.997 ∙ e^{0.8460[ln hardness]+0.0584} Silver, Acute WER*0.85 ∙ e^{1.72[ln hardness]-6.59} Silver, Chronic Not applicable Zinc, Acute WER*0.978 ∙ e^{0.8473[ln hardness]+0.884} Zinc, Chronic WER*0.986 ∙ e^{0.8473[ln hardness]+0.884} General Information on the Reasonable Potential Analysis (RPA) Cranbrook Village MHP WWTP – Renewal Fact sheet Page 5 of 7 The RPA process itself did not change as the result of the new metals standards. However, application of the dissolved and hardness-dependent standards requires additional consideration in order to establish the numeric standard for each metal of concern of each individual discharge. The hardness-based standards require some knowledge of the effluent and instream (upstream) hardness and so must be calculated case-by-case for each discharge. Metals limits must be expressed as ‘total recoverable’ metals in accordance with 40 CFR 122.45(c). The discharge-specific standards must be converted to the equivalent total values for use in the RPA calculations. We will generally rely on default translator values developed for each metal (more on that below), but it is also possible to consider case-specific translators developed in accordance with established methodology. RPA Permitting Guidance/WQBELs for Hardness-Dependent Metals - Freshwater The RPA is designed to predict the maximum likely effluent concentrations for each metal of concern, based on recent effluent data, and calculate the allowable effluent concentrations, based on applicable standards and the critical low-flow values for the receiving stream. If the maximum predicted value is greater than the maximum allowed value (chronic or acute), the discharge has reasonable potential to exceed the standard, which warrants a permit limit in most cases. If monitoring for a particular pollutant indicates that the pollutant is not present (i.e. consistently below detection level), then the Division may remove the monitoring requirement in the reissued permit. 1. To perform a RPA on the Freshwater hardness-dependent metals the Permit Writer compiles the following information: • Critical low flow of the receiving stream, 7Q10 (the spreadsheet automatically calculates the 1Q10 using the formula 1Q10 = 0.843 (s7Q10, cfs) 0.993 • Effluent hardness and upstream hardness, site-specific data is preferred • Permitted flow • Receiving stream classification 2. In order to establish the numeric standard for each hardness-dependent metal of concern and for each individual discharge, the Permit Writer must first determine what effluent and instream (upstream) hardness values to use in the equations. The permit writer reviews DMR’s, Effluent Pollutant Scans, and Toxicity Test results for any hardness data and contacts the Permittee to see if any additional data is available for instream hardness values, upstream of the discharge. If no hardness data is available, the permit writer may choose to do an initial evaluation using a default hardness of 25 mg/L (CaCO3 or (Ca + Mg)). Minimum and maximum limits on the hardness value used for water quality calculations are 25 mg/L and 400 mg/L, respectively. If the use of a default hardness value results in a hardness-dependent metal showing reasonable potential, the permit writer contacts the Permittee and requests 5 site-specific effluent and upstream hardness samples over a period of one week. The RPA is rerun using the new data. Cranbrook Village MHP WWTP – Renewal Fact sheet Page 6 of 7 The overall hardness value used in the water quality calculations is calculated as follows: Combined Hardness (chronic) = (Permitted Flow, cfs *Avg. Effluent Hardness, mg/L) x (s7Q10, cfs *Avg. Upstream Hardness, mg/L) (Permitted Flow, cfs + s7Q10, cfs) The Combined Hardness for acute is the same but the calculation uses the 1Q10 flow. 3. The permit writer converts the numeric standard for each metal of concern to a total recoverable metal, using the EPA Default Partition Coefficients (DPCs) or site-specific translators, if any have been developed using federally approved methodology. 4. The numeric standard for each metal of concern is divided by the default partition coefficient (or site-specific translator) to obtain a Total Recoverable Metal at ambient conditions. In some cases, where an EPA default partition coefficient translator does not exist (ie. silver), the dissolved numeric standard for each metal of concern is divided by the EPA conversion factor to obtain a Total Recoverable Metal at ambient conditions. This method presumes that the metal is dissolved to the same extent as it was during EPA’s criteria development for metals. For more information on conversion factors see the June, 1996 EPA Translator Guidance Document. 5. The RPA spreadsheet uses a mass balance equation to determine the total allowable concentration (permit limits) for each pollutant using the following equation: Ca = (s7Q10 + Qw) (Cwqs) – (s7Q10) (Cb) Qw Where: Ca = allowable effluent concentration (µg/L or mg/L) Cwqs = NC Water Quality Standard or federal criteria (µg/L or mg/L) Cb = background concentration: assume zero for all toxicants except NH3* (µg/L or mg/L) EPA default partition coefficients or the “Fraction Dissolved” converts the value for dissolved metal at laboratory conditions to total recoverable metal at in-stream ambient conditions. This factor is calculated using the linear partition coefficients found in The Metals Translator: Guidance for Calculating a Total Recoverable Permit Limit from a Dissolved Criterion (EPA 823-B-96-007, June 1996) and the equation: _Cdiss__ = _______1_______________ Ctotal 1 + { [Kpo] [ss(1+a)] [10-6] } Where: ss = in-stream suspended solids concentration [mg/l], minimum of 10 mg/L used, and Kpo and a = constants that express the equilibrium relationship between dissolved and adsorbed forms of metals. A list of constants used for each hardness-dependent metal can also be found in the RPA program under a sheet labeled DPCs. Cranbrook Village MHP WWTP – Renewal Fact sheet Page 7 of 7 Qw = permitted effluent flow (cfs, match s7Q10) s7Q10 = summer low flow used to protect aquatic life from chronic toxicity and human health through the consumption of water, fish, and shellfish from noncarcinogens (cfs) * Discussions are on-going with EPA on how best to address background concentrations Flows other than s7Q10 may be incorporated as applicable: 1Q10 = used in the equation to protect aquatic life from acute toxicity QA = used in the equation to protect human health through the consumption of water, fish, and shellfish from carcinogens 30Q2 = used in the equation to protect aesthetic quality 6. The permit writer enters the most recent 2-3 years of effluent data for each pollutant of concern. Data entered must have been taken within four and one-half years prior to the date of the permit application (40 CFR 122.21). The RPA spreadsheet estimates the 95th percentile upper concentration of each pollutant. The Predicted Max concentrations are compared to the Total allowable concentrations to determine if a permit limit is necessary. If the predicted max exceeds the acute or chronic Total allowable concentrations, the discharge is considered to show reasonable potential to violate the water quality standard, and a permit limit (Total allowable concentration) is included in the permit in accordance with the U.S. EPA Technical Support Document for Water Quality-Based Toxics Control published in 1991. 7. When appropriate, permit writers develop facility specific compliance schedules in accordance with the EPA Headquarters Memo dated May 10, 2007 from James Hanlon to Alexis Strauss on 40 CFR 122.47 Compliance Schedule Requirements. 8. The Total Chromium NC WQS was removed and replaced with trivalent chromium and hexavalent chromium Water Quality Standards. As a cost savings measure, total chromium data results may be used as a conservative surrogate in cases where there are no analytical results based on chromium III or VI. In these cases, the projected maximum concentration (95th %) for total chromium will be compared against water quality standards for chromium III and chromium VI. 9. Effluent hardness sampling and instream hardness sampling, upstream of the discharge, are inserted into all permits with facilities monitoring for hardness-dependent metals to ensure the accuracy of the permit limits and to build a more robust hardness dataset. 10. Hardness and flow values used in the Reasonable Potential Analysis for this permit included: Parameter Value Comments (Data Source) Average Effluent Hardness (mg/L) [Total as, CaCO3 or (Ca+Mg)] N/A Average Upstream Hardness (mg/L) [Total as, CaCO3 or (Ca+Mg)] N/A 7Q10 summer (cfs) N/A 1Q10 (cfs) N/A Permitted Flow (MGD) 0.010 BIMS