Loading...
HomeMy WebLinkAboutNC0025453_speculative limits_20000710 State of North Carolina . Department of Environment • and Natural Resources A&41�► Division of Water Quality James B. Hunt,Jr., Governor Bill Holman,Secretary NCDENR Kerr T. Stevens,Director NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES July 10, 2000 Mr. R. Steven Biggs, Town Manager Town of Clayton P.O. Box 879 Clayton, North Carolina 27520 Subject: Speculative Limits for Little River Water Reclamation Facility/ Clayton WWTP NPDES Permit NCO025453 Town of Clayton Johnston County Dear Mr. Biggs: This letter is in response to your request for speculative effluent limits for the proposed expansion (hydraulic re-rating to 2.5 MGD) at the Clayton wastewater treatment plant. This letter will also address Clayton's request to perform minor modifications at the plant in order to obtain better operational flexibility. The Clayton plant currently has a permit to discharge 1.9 MGD of treated municipal wastewater to the Neuse River in the Neuse River Basin. Michael Wicker, Hobbs, Upchurch &Associates, requested updated speculative limits on the Town's proposed re-rating to 2.5 MGD. The NPDES Unit is currently processing the renewal of the Town's permit for 1.9 MGD. We have reviewed the request and provide the following response with the enclosed speculative limits. The speculative limits presented here are based on our understanding of the proposal and of present environmental conditions. The Division of Water Quality (DWQ) cannot guarantee that it will issue the Town an NPDES permit to expand its discharge of treated wastewater into waters of the State. Nor can we guarantee that the effluent limitations and other requirements included in any permit will be exactly as presented here. Final decisions on these matters will be made only after the Division evaluates a formal permit application for the Town's discharge and notices the proposal for public comment. Environmental Assessments of New Projects and Expansions As you are aware, the Town will have to evaluate this project for environmental impacts before applying for a permit modification. Any entity proposing to construct new or expanded waste 1617 Mail Service Center,Raleigh,North Carolina 27699-1617 919 733-5083,extension 510 (fax)919 733-0719 An Equal Opportunity Affirmative Action Employer Susan.A.Wilson@ncmail.net Town of Clayton Speculative Limits for 2.5 MGD 2 treatment facilities using public funds or public (state) lands must first prepare an environmental assessment (EA)when wastewater flows (1) equal or exceed 0.5 MGD or (2) exceed one-third of the 7Q 10 flow of the receiving stream. DWQ will not accept a permit application for a project requiring an environmental assessment until the Division has approved the EA and sent a Finding of No Significant Impact (FONSI) to the state Clearinghouse for review and comment. The Division is aware that Clayton has submitted a draft EA for review. An Environmental Assessment should contain a clear justification for the proposed project. It should provide an analysis of potential alternatives, including a thorough evaluation of non-discharge alternatives. Nondischarge alternatives or alternatives to expansion, such as spray irrigation, water conservation, or inflow and infiltration reduction, are considered to be environmentally preferable to a surface water discharge. In accordance with the North Carolina General Statutes, the preferred alternative must be the practicable waste treatment and disposal alternative with the least adverse impact on the environment. If the EA demonstrates that the project may result in a significant adverse effect on the quality of the environment, you must then prepare an Environmental Impact Statement. Mr. Steve Zoufaly of the Water Quality Planning Branch can provide further information regarding the requirements of the N.C. Environmental Policy Act. You can contact Mr. Zoufaly directly at (919) 733-5083, ext. 566. Speculative Effluent Limits Based on the available information, speculative limits for the proposed discharge of 2.5 MGD flow to the Neuse River are presented in the attached table and are explained below. Flow Limits. The flow limit will be increased to 2.5 MGD as requested by the Town. This limit will be applied as a monthly average. Total Nitrogen. The Nutrient Management Strategy (NMS) rule (adopted December 1997 and revised February 2000) requires that point sources in the Neuse River Basin, including the Little River WRF/ Clayton WWTP, meet annual mass limits for total nitrogen (TN) beginning with calendar year 2003. Clayton's initial allocation is approximately 21, 400 lb/yr TN. The NMS rule establishes additional requirements for facilities planning to expand beyond their 1995 permitted flows. An expanding facility must acquire any nitrogen allocation it needs for the added discharge before it can apply for the necessary NPDES permit modification. The facility can (1) provide additional treatment in order to meet its original allocation, (2) acquire additional allocation from existing point sources, or (3) acquire additional allocation from nonpoint sources through the Wetlands Restoration Fund. In the last case, the facility must obtain 30 years' allocation prior to permit application. In any event, the facility's total allocation cannot be greater than the annual mass limit equivalent to 3.5 mg/L TN at the expanded flow. Facilities joining a group compliance association are not subject to individual limits but will be responsible as a group for meeting their collective allocation. Clayton has expressed its intent to join such an association, so much of this explanation does not apply directly to its discharge requirements. However, the discussion is still relevant to the Town's nitrogen allocation and the limit the association must meet. Note that the Division expects to complete a more comprehensive modeling effort in early 2001 and will use those results to better define the nitrogen reduction target for the Neuse River estuary. It is not clear from preliminary results whether the target will need to be changed. Be aware that if the target level is lowered, it could lead to further reductions in the point source allocations. To reiterate, design considerations must include the ability to achieve an annual load based on a concentration of 3.5 mg/1 at 2.5 MGD, regardless of the Town's chosen route of compliance. (Please refer to 15A NCAC 2B .0234J Town of Clayton Speculative Limits for 2.5 MGD 3 Total Phosphorus. The NMS rule sets the following phosphorus limits for point source discharges: Existing facilities: 2 mg/L, quarterly average New or expanding: 1 mg/L, monthly average (this if not part of an association, see below) If a discharger is part of a group compliance association, as in Raleigh's case, then it may retain the quarterly limit of 2 mg/L upon expansion. The Division may also establish more stringent limits if necessary to protect water quality standards in localized areas. 1301)5, NH3-N, D.O. The summer limits are 5 mg/1 (BOD5) and 1 mg/l (NH3-N) based on the waste assimilative capacity of the receiving stream at low flow conditions for this size facility(2.5 MGD). This is a reduction from the previous summer limits of 5 &2 at the 1.9 MGD permitted flow. The winter limits of 10 mg/1 (BOD5) and 2 mg/l (NH3-N) are reduced from the previous winter limits of 10 & 4 at the 1.9 MGD permitted flow. The effluent dissolved oxygen will be limited at a minimum of 6.0 mg/l. TSS. The limits for total suspended solids are standard for secondary treatment of municipal wastewater and are the same as in the current permit. Fecal Colifo_rm pH. The limits for fecal coliform bacteria and pH are derived to protect water quality in the receiving stream and remain the same as in the current permit. Chlorine. The Division requires chlorine limits and dechlorination for all new or expanding dischargers using chlorine for disinfection. The process of chlorination/ dechlorination, or an alternate form of disinfection such as ultraviolet radiation, should allow the facility to comply with the total residual chlorine limit. Chronic Toxicity Testing: The Town's effluent must not exhibit chronic toxicity at the 2.5 MGD flow based on a Ceriodaphnia Pass/Fail test at 2.0%. Toxicant Parameters: Estimation of toxicant parameters will not be given with this speculative letter, but will be submitted as appropriate with the draft NPDES permit. Minor Treatment Plant Modifications The letter dated February 21, 2000 also requested approval of minor modifications to the treatment plant in order to improve flexibility and improve operations. By this letter the Division of Water Quality will approve Items (a), (b), (c), (d), (e), (g), (h), (i), 0) listed in the aforementioned letter (attached). Technically, under normal circumstances, the Division would likely require an Authorization to Construct permit at least for Items (g) and 0). However, due to resource constraints and the acknowledgement that such improvements will provide increased operational flexibility at the plant, the Division will not require a permit for this project. Additionally, as stated in the letter from Mr. Wicker, the process units will not change and no treatment units will be added with this modification. The Town of Clayton assumes all risk with implementation of these improvements and no permit for 2.5 MGD may be issued until a FONSI is received and after a draft permit is submitted for public notice. All calculations documenting the ability of the treatment units to accommodate a design flow of 2.5 MGD, along with plans and specifications for any treatment unit modifications or additions, must be submitted at that time. Please note that Item (fl will not, and cannot, be approved without an Authorization to Construct permit. Town of Clayton Speculative Limits for 2.5 MGD 4 Again, as stated previously, this approval is allowed specifically for this case, only, and only for the Town of Clayton. Please inform your consultants that although similar situations may occur at other facilities in the future, the Division may not provide approval in this manner. This written response is offered following the verbal transmission of the speculative limits to Michael Wicker on Friday, June 9, 2000. If you have any additional questions about these limits, feel free to contact Susan Wilson at (919) 733-5083, extension 510. Sincerely, David A. Goodrich, Supervisor NPDES Unit Water Quality Section cc: Raleigh Regional Office/ Water Quality Central Files NPDES Unit Files Michael Wicker, P.E., Hobbs, Upchurch &Associates P.O. Box 1737 Southern Pines, NC 28388 Town of Clayton Speculative Limits for 2.5 MGD 5 A. (1.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS SPECULATIVE ONLY Effluent Characteristics Limits Monitoring Requirements MO y WNW Da#y 111111mmenmW Sample Type Average Average Mwd um Frequency Looaflonl Flow 2.5 MGD Continuous Recording Influent or Effluent BOD,5 day(202C)2 5.0 mg/I 7.5 mg/I Daily Composite Influent& [April 1-October 31] Effluent BOD,5 day(202C)2 10.0 mg/I 15.0 mg/1 Daily Composite Influent& [November 1 -March 311 Effluent Total Suspended Residue2 30.0 mg/I 45.0 mg/I Daily Composite Influent& Effluent NHa as N [April 1-October 31] 1.0 m I Daily composite Effluent NH3 as N[November 1-March 31] 2.0 mg/1 Daily Composite Effluent Dissolved Oxygen3 Daily Grab Effluent Dissolved Oxygen 3/Week Grab Upstream& Downstream Fecal Coliform (geometric mean 2001100 ml 400/100 ml Daily Grab Effluent Fecal Coliform (geometric mean) 3/Week Grab Upstream& Downstream Total Residual Chlorine4 28 µg/I Daily Grab Effluent No Effluent Limit(mg/1) Weekly Composite Effluent Total Nitrogen No Effluent Limit Ib/month (NO2-N+NOs-N+TM<N)5 ( ) Monthly Calculated Effluent 21,400 lb/year(Annual Mass Loading)6 Annually Calculated Effluent Total Phosphorus 7 2.0 mg/L(Quarterly Average) Weekly Composite Effluent Temperature('C) Daily Grab Effluent Temperature(°C) 3/Week Grab Upstream& Downstream Conductivity Daily Grab Effluent Conductivity 3/Week Grab Upstream& Downstream Chronic Toxicity8 Quarterly Composite Effluent H10 6-9 Daily Grab Effluent (Footnotes on next page) Town of Clayton Speculative Limits for 2.5 MGD 6 A. (1.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS SPECULATIVE VE ONLY (Continued) Footnotes: I. Sample locations: E-Effluent, I-Influent, U-Upstream at NCSR 1700, D-Downstream at (1) NC Highway 42 and (2) NCSR 1908. Stream samples shall be grab samples and shall be collected 3/Week during June - September and 1/Week during the remaining months of the year. Instream monitoring is provisionally waived in light of the permittee's participation in the Lower Neuse Basin Association. Instream monitoring shall be conducted as stated in this permit should the permittee end its participation in the Association. 2. The monthly average effluent BOD5 and Total Suspended Residue concentrations shall not exceed 15% of the respective influent value (85% removal). 3. The daily average dissolved oxygen effluent concentration shall not be less than 6.0 mg/l. 4. Total residual chlorine is required only if chlorine is used as a disinfectant (or elsewhere in the process). 5. See Special Condition A.(2.), Total Nitrogen Monitoring. 6. The annual mass loading limit for total nitrogen shall become effective with the calendar year beginning on January 1, 2003 unless it is provisionally waived per Special Condition A.(3.), Annual Limits for Total Nitrogen. 7. The quarterly average for total phosphorus shall be the average of composite samples collected weekly during the calendar quarter (January-March, April-June, July-September, October- December). 8. Chronic Toxicity (Ceriodaphnia dubia) P/F at 2.0 W March, June, September, and December [see Special Condition A.(4)]. Toxicity monitoring shall coincide with any metals monitoring. 9. The pH shall not be less than 6.0 standard units nor greater than 9.0 standard units and shall be monitored daily at the effluent by grab sample. There shall be no discharge of floating solids or visible foam in other than trace amounts. Town of Clayton Speculative Limits for 2.5 MGD 7 A. (2.) TOTAL NITROGEN MONITORING The Permittee shall calculate the annual mass loading of total nitrogen as the sum of monthly loadings, according to the following equations: (1) Monthly Mass Loading (lb/mo) = TN x Q x 8.34 where: TN = the average total nitrogen concentration (mg/L) of the composite samples collected during the month Q = the total wastewater flow discharged during the month (MG/month) 8.34 = conversion factor, from (mg/L x MG) to pounds (2) Annual Mass Loading (lb/yr) = E (Monthly Mass Loadings) for the calendar year The Permittee shall report the total nitrogen concentration for each sample and the monthly mass loading in the appropriate self-monitoring report and the annual mass loading of total nitrogen in the December self-monitoring report for the year. A. (3.) ANNUAL LIMITS FOR TOTAL NITROGEN (a) The Neuse Nutrient Management Strategy rule for point sources (1) provides that annual mass limits for total nitrogen shall be included in the permits for all dischargers with permitted flows (as defined in the Strategy) greater than or equal to 0.5 MGD and that those nitrogen limits, including the limits in this permit, shall become effective with the calendar year beginning on January 1, 2003. (b) The Neuse rule also provides that members of a group compliance association shall not be subject to individual annual mass limits for total nitrogen.At the time of permit issuance, the Permittee had expressed interest in joining such an association. Accordingly, (1) the total nitrogen limit in Condition A(1) of this permit is deemed waived provided that the following conditions are met: (i) a formal agreement between the association and Environmental Management Commission, as outlined in 15A NCAC 2B. 0234, is established and is in effect; and (ii) the Permittee is a party to said agreement; and (iii) the association and the Permittee substantially conform with the agreement. (2) So long as the total nitrogen limit in Condition A.(1.) is waived, the group nitrogen allocation established pursuant to the agreement referenced above and any subsequent amendments is hereby incorporated as an enforceable part of this permit. (c) If the Division determines, at any time during the term of this permit, that these conditions are not being met, it shall notify the Permittee in writing of this determination and of its basis. The consequence of such a determination shall be that the Permittee's annual mass limit for total nitrogen and its effective date shall be reinstated immediately. The Division shall accept and consider written responses received from the Permittee and/or the association within thirty (30) days of the original notice before making a final decision and will provide that decision in writing. Town of Clayton Speculative Limits for 2.5 MGD 8 A. (3.) ANNUAL LIMITS FOR TOTAL NITROGEN (cont'd.) (d) The Permittee shall notify the Division in writing within five (5) working days if, at any time during the term of this permit, the Permittee elects not to join the association, or if it withdraws or otherwise loses its membership in the association. Notification shall be sent to: NC DENR/ Division of Water Quality / NPDES Unit 1617 Mail Service Center Raleigh, NC 27699-1617 Footnote: (1) Neuse River Basin - Nutrient Sensitive Waters Management Strategy: Wastewater Discharge Requirements (15A NCAC 2B. 0234). A. (4.) CHRONIC TOXICITY PERMIT LIMIT (QRTRLY) The effluent discharge shall at no time exhibit observable inhibition of reproduction or significant mortality to Ceriodaphnia dubia at an effluent concentration of 2 %. The permit holder shall perform at a minimum, quarteriu monitoring using test procedures outlined in the "North Carolina Ceriodaphnia Chronic Effluent Bioassay Procedure," Revised February 1998, or subsequent versions or "North Carolina Phase II Chronic Whole Effluent Toxicity Test Procedure" (Revised-February 1998) or subsequent versions. The tests will be performed during the months of March, June, September, and December. Effluent sampling for this testing shall be performed at the NPDES permitted final effluent discharge below all treatment processes. If the test procedure performed as the first test of any single quarter results in a failure or ChV below the permit limit, then multiple-concentration testing shall be performed at a minimum, in each of the two following months as described in "North Carolina Phase Il Chronic Whole Effluent Toxicity Test Procedure" (Revised-February 1998) or subsequent versions. The chronic value for multiple concentration tests will be determined using the geometric mean of the highest concentration having no detectable impairment of reproduction or survival and the lowest concentration that does have a detectable impairment of reproduction or survival. The definition of "detectable impairment," collection methods, exposure regimes, and further statistical methods are specified in the "North Carolina Phase II Chronic Whole Effluent Toxicity Test Procedure" (Revised- February 1998) or subsequent versions. All toxicity testing results required as part of this permit condition will be entered on the Effluent Discharge Monitoring Form (MR-1) for the months in which tests were performed, using the parameter code TGP3B for the pass/fail results and THP313 for the Chronic Value. Additionally, DWQ Form AT-3 (original) is to be sent to the following address: Attention: North Carolina Division of Water Quality Environmental Sciences Branch 1621 Mail Service Center Raleigh, North Carolina 27699-1621 Completed Aquatic Toxicity Test Forms shall be filed with the Environmental Sciences Branch no later than 30 days after the end of the reporting period for which the report is made. Town of Clayton Speculative Limits for 2.5 MGD 9 i A. (4.) CHRONIC TOXICITY PERMIT LIMIT (QRTRLY) (cont'd.) Test data shall be complete, accurate, include all supporting chemical/physical measurements and all concentration/response data, and be certified by laboratory supervisor and ORC or approved designate signature. Total residual chlorine of the effluent toxicity sample must be measured and reported if chlorine is employed for disinfection of the waste stream. Should there be no discharge of flow from the facility during a month in which toxicity monitoring is required, the permittee will complete the information located at the top of the aquatic toxicity (An test form indicating the facility name, permit number, pipe number, county, and the month/year of the report with the notation of"No Flow" in the comment area of the form. The report shall be submitted to the Environmental Sciences Branch at the address cited above. Should the permittee fail to monitor during a month in which toxicity monitoring is required, monitoring will be required during the following month. Should any test data from this monitoring requirement or tests performed by the North Carolina Division of Water Quality indicate potential impacts to the receiving stream, this permit may be re- opened and modified to include alternate monitoring requirements or limits. NOTE: Failure to achieve test conditions as specified in the cited document,such as minimum control organism survival, minimum control organism reproduction, and appropriate environmental controls, shall constitute an invalid test and will require immediate follow-up testing to be completed no later than the last day of the month following the month of the initial monitoring. Hobbs, Upchurch & Associates, P.A. Consulting Engineers 290 S.W.Broad Street • Post Office Box 1737 • Southern Pines,NC 28388 February 21, 2000 Mr. David Goodrich, Supervisor NPDES Unit, Division of Water Quality Post Office Box 29535 Raleigh,North Carolina 27626-0535 2'5 RE: Speculative Li P Expansion Town of Clayton Wastewater lforastewa r Treatment Plant fi NPDES Permit No. NCO025453 HUA No. CT9905 Dear Mr. Goodrich: The Town of Clayton intends to expand its existing 1.9 mgd wastewater treatment plant, including an Environmental Assessment. The purpose of this letter is to request speculative limits for expanded NPDES permit flows of 2.5 mgd. It is assumed that the existing Neuse River Basin Policy, the Neuse River Basin Rules, etc. will result in limits similar to the 5 BOD, 2 Ammonia, 30 TSS limits currently proposed for the 1.9 mgd facility. We are also assuming that the TP will be lowered from 2 ppm to 1 ppm and that the Nitrogen limit of 21,400 lbs . per Annum will stay the same. The discharge point to the Neuse River will remain the same as in the current permit. The Town of Clayton wastewater treatment plant discharges to the Neuse River WS-IV, NSW, CA. The wastewater treatment plant operates under NPDES permit No. NC0025453. The attached Quadrangle map shows the location of the treatment facility. A DRAFT EA has been submitted to DWQ for review. The WWTP is approaching 80% capacity at this time and the Town wishes to be proactive in expanding the NPDES permit. A recent re-rating study indicates that the existing WWTP can be re-rated to 2.5 mgd as currently designed. Minor piping and flow control improvements will be added for increased flexibility as a factor of safety. A full 201 study for a 20 year plan will be initiated at a later date to consider further permit increases or other options which will involve additional construction of facilities. The minor changes we are making to the WWTP to improve flexibility are as follows: Design modifications to the following: a. Replace existing extended shaft centrifugal pumps with submersible centrifugal pumps in the dry pit and add variable frequency drives to control pumps in relation to influent flows. b. Improvement to the existing hydraulic split at influent pump station by the addition of a slide gate for diversion to the existing intermediate pump station, which pumps to trickling filter system. Southern Pines, NC • Telephone 910-692-5616 • Fax 910-692-7342 • e-mail:huamain@pinehurst.net Myrtle Beach • Kill Devil Hills • Raleigh Mr. Dave Goodrich February 21, 2000 Page 2 C. Improvements to existing oxidation splitter box by adding slide gates to allow control of flow split to each oxidation ditch. d. Improvements to existing clarifier splitter box by adding slide gates to allow control of flow split to each clarifier. e. Improvements to existing clarifier hydraulics by installation of Stamford Baffles. f. Improvements to oxidation ditch aeration efficiency by replacing existing Carousel aerators or conversion to fine or course bubble aeration system with blowers. g. Duplication of existing WWTP polymer feed system through additional polymer feed piping to the clarifiers and additional polymer pumps for redundancy. h. Separation of RAS/WAS pump piping by additional WAS piping to allow RAS and WAS to operate concurrently. Replacement of the existing RAS pumps with new pumps. i. Replacement of the existing air diaphragm sludge transfer pumps with positive displacement or rotary lobe pumps. j. Rerouting of the existing backwash return piping from oxidation ditch splitter box to the influent headworks to lesson surge.on clarifiers. Additional backwash manhole to increase storage capacity. The above changes will aid the operator to control flow and air and therefore run the WWTP more efficiently. The process units will not change nor are we adding additional units. We do not see that this requires an ATC; however the Town has requested that DWQ confirm this prior to our beginning construction. The Raleigh Regional Office will be contacted in advance of any construction. Design of these improvements has just begun with a start construction date of September 2000 projected. If you have any questions about this matter or if you require additional information, please contact me at(910) 692-5616. Sincerely, Hobbs, Upchurch&Associates,P.A. Michael C. Wicker,P.E. Enclosure Cc: Mr. Steve Biggs, Town of Clayton Mr. Tim Simpson, Town of Clayton Mr. Randy Jones,Raleigh Regional Office Mr. Mike Templeton,DWQ NPDES Group EXAMPLES: FINANCIAL IMPACTS OF NEUSE NSW MANAGEMENT STRATEGY ON POINT SOURCE DISCHARGES Current Conditions Potential Future Conditions - `a) -- (b) T (h) i Flow TN TN Flow TN TN TN Total TN mass over Total Offset (MGD) (mg/l, (mass (MGD) (mg/l, (mass (est. BAT allocation and Payment conc. allocation) cone. allocation) concentration subject to offset equivalent equivalent) &mass equiv.) payment Clayton L9 3.7 mg/1 21,400 2.5 2.8 mg/l 21,400 3.5 mg/1 (73 26,645-21,400 $3,460,000 lbs/yr lbs/yr lbs/day) = 5,245 lbs/yr Less than BAT I = 26,645lbs/yr . Ref. 15A NCAC 2B .0234 Neuse River Basin-NSW Management Strategy: Wastewater Discharge Requirements. Parts (7) and (8) refer to new and expanding facilities, respectively. FOOTNOTES (next page) EXAMPLES: FINANCIAL IMPACTS OF NEUSE NSW MANAGEMENT STRATEGY ON POINT SOURCE DISCHARGES FOOTNOTES (a) Current permitted/design flow. (b) The concentration equivalent (mg/1) of the total yearly nitrogen mass allocation. This value is calculated as follows (for Clayton): PF* cone. * 8.34 =Allocation/365 d Cone= (21,400 lbs/yr*yr/365 d) / 1.9 * 8.34 =3.7 mg/l (c) The total nitrogen annual mass allocation (this has been set and pre-determined with implementation of the temp. rule). (d) Hypothetical future permitted flow. (e) The concentration equivalent (mg/1) of the total annual nitrogen mass allocation based on the hypothetical permitted future flow. This value is calculated similarly to that shown in (b): PF(future) * cone. * 8.34 =Allocation/365 d Cone. _ (21,400 lbs/yr*yr/365d) / 2.5 * 8.34 =2.8 mg/l M The total nitrogen mass allocation (same as (c)). (g) The Division has made the assumption that at this time 3.5 mg/l TN is Best Available Technology-it's possible a facility may be able to achieve a lesser concentration. However, for this example 3.5 mg/1 TN will be assumed as the proposed minimum treatment technology (and this value is also used in the rule). Should a facility prove that a lesser value is feasible, the offset calculation may be adjusted accordingly. The calculation is as follows: Allocation=PF(future) * 3.5 mg/1* 8.34 =2.5 * 3.5 * 8.34 73 lbs/day* 365d/yr 26,645 lbs/yr (h) The facility must pay the difference between what their present annual mass nitrogen allocation is and what the calculated load at BAT of 3.5 mg/l is. This means paying the difference between the load at 2.8 mg/l (concentration based on allocated load) and 3.5 mg/l for the future flow of 2.5 MGD (in the case of Clayton) Offset load =Load at 3.5 mg/1&2.5 MGD -Allocated load 26,645-21,400 =5245 lbs/year (i) As stated in the rule, the offset cost must be determined based on$11 lb TN/yr for a period of 30 years at 200%. Total offset cost= Offset Load * $11 lb TN/yr* 30 yr* 2 = 5245 * 11 * 30 * 2 _$3,460,000 or$3.46 M 2 State of North Carolina Department of Environment and Natural Resources • Division of Water Quality James B. Hunt, Jr., Governor D E N R Bill Homan, Secretary Kerr T. Stevens, Director February 14,2000 Michael C.Wicker FEB 16 2000 Hobbs,Upchurch, and Associates,PA 290 S.W. Broad Street Post Office Box 1737 Southern Pines, North Carolina 28388 RE: Environmental Assessment(EA)for the Town of Clayton Wastewater Treatment Plant Upgrade Johnston County Dear Mr.Wicker: The Division of Water Quality(Division)has completed it's initial review of the December 29, 1999 Environmental Assessment(EA)for the"Town of Clayton Wastewater Treatment Plant Upgrade" in Johnston County. There are a number of issues that need to be addressed prior to proceeding to the next level of review. These items are identified on the attached pages. Once the EA has been amended to address our concerns,please forward eight copies of the document to me for an internal review by the Department of Environment and Natural Resources. As a first step in revising the document,the Town of Clayton needs to apply to the NPDES Unit for speculative limits for the wastewater treatment plant(WWTP)expansion. The NPDES Unit is aware of the EA and that speculative limits will need to be provided for the EA process to continue. The NPDES Unit is therefore anticipating a speculative limits request from the Town for this project and have figured this request into their upcoming workload. If you need any clarification regarding the comments provided,please contact me at 919-733- 5083,ext. 567. Sincerely, Gloria F.Putnam Environmental Specialist 1617 Mail Service Center, Raleigh, North Carolina 27699-1617 Telephone 919-733-5083 FAX 919-715-5637 An Equal Opportunity Affirmative Action Employer 50%recycled/100%post-consumer paper Division of Water Quality Completeness Review Comments Town of Clayton WWTP Upgrades Environmental Assessment (EA) February 14, 2000 . 1. In the "Existing Environmental Characteristics" section, the EA does an excellent job of identifying the current environmental resources in Johnston County. However, in some of the categories, specific information for the project site and immediate vicinity is either not provided or needs clarification. Please review each category and amend to include the site specific information, as applicable. Also, please provide a vicinity map which clearly depicts the locations of the wastewater treatment plant and service areas, and prominent environmental resources (such as surface waters). Be sure that the map has a scale. It would also be helpful to present the information in the same order under each resource category, such as from county level to site specific. . 2. The area to be serviced by this expansion should be'defined and identified on an accompanying map. 3. Please provide a Table of Contents in the document. 4. The EA identifies on page 34 that there are impaired streams due to urban stormwater runoff. A secondary impact of this project will be increased development and therefore increased runoff and surface water impacts. How do Johnston County and Clayton plan to reduce these impacts? Does the Town of Clayton have a growth management plan? If so, it should be referenced and discussed in terms of the secondary and cumulative impacts of this project. 15. The EA should identify whether wetlands exist at the project site and whether there will be impacts to these resources. The document appears to contradict itself with regards to wetlands impacts. Please review and revise to make consistent, the related information on pages 20, 26, 27, and 55. 6. Identify the water classifications in the project area and whether or not they are supporting their designated uses. 7. Identify the"Prime Farmland"in the project service area. 8. At the beginning of the document, defines the following terms and use consistently throughout the document: service area, planning area,project area, and project route. Existing environmental conditions and impacts should be presented according to these areas. 9. Please identify where the WWTP is located, where the discharge is located (one of the maps in the exhibits indicates that there is a"proposed discharge). 10. On page 32, label the table that contains Fecal Coliform data. 11. On pages 36-37, the EA identifies the need for follow-up action on behalf of project sponsors for effective mitigation for water quality impacts. What specific mitigation will be proposed for this project(page 46). 12. On page 38, the document states that impacts from the proposed increased discharge will be insignificant compared to upstream impacts. Please identify if they will be significant on their own accord. 13. For all resource categories, identify impacts (see comment number 10). These impacts should be identified in a consist manner throughout the document. As the EA is currently written, some impacts are identified in the"existing environment" section while others are identified in the section on impacts (and are sometimes not the same in both sections). •14. Page 2 of the EA mentions that all work is to be constructed entirely on the existing site with the exception of any non-potable water lines to off-site reuse locations. Please clarify if there is a reuse component to this project. If there is, this must be included as part of the impact analysis. •15. On page'52, please identify the information source for the statement that"Even the best sediment control measures are only about 70%effective." •16. On page 52, the EA identifies for the first time in the document, that there will be "pipeline construction." Please identify what this is referencing. 17. Support the statements on page 53 that say the proposed discharge will not impair the use of the Neuse River by the Town of Smithfield and Johnston County. 18. The statement in the EA on page 53 which compares the discharge of the Town of Clayton to the discharge from the City of Raleigh should be removed from the document. The purpose of an environmental assessment, as you are aware, is to evaluate the impacts a proposed project will have on the environment, not to evaluate the impacts of a proposed project in comparison to other projects in the area. However, it would not be inappropriate for the EA to evaluate the cumulative natural resource impacts from similar projects in a region. 19. On page 53, please clarify what size buffers are required for high and low density development. .20. The first paragraph on page 53 under the section on wastewater treatment and disposal is more relevant to the need for the project and should be placed in the document accordingly. 21. The EA should reference the location of the appropriate exhibits. 22. In the Exhibits Section,please provide a date on Figure 2.1 of the 201 Facilities Plan. 23. The EA should include a cover sheet with appropriate contact information as indicated on the attached example. 24. On page 44, identify whether there are mollusks downstream of the discharge and what the potential impacts will be from the expansion.