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HomeMy WebLinkAboutSW8030108_COMPLIANCE_20041025STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW �3DID� DOC TYPE El CURRENT PERMIT ❑ APPROVED PLANS ❑ HISTORICAL FILE COMPLIANCE EVALUATION INSPECTION DOC DATE YYYYMMDD NCDENR North Carolina Department of Environment and Natural Resources Division of Water Quality Michael F. Easley, Governor William G, Ross, Jr., Secretary Alan W. Klimek, P.E., Director October 25, 2004 CERTIFIED MAIL #7002 1000 0005 2390 8474 RETURN RECEIPT REQUESTED Mr, Jimmy Hatcher, Member Manager Perimae & Associates, LLC Post Office Box 15242 Wilmington, NC 28408 Subject: NOTICE OF VIOLATION Smith Creek Village Stormwater Permit No.SW8 030108 New Hanover County Dear Mr. Hatcher: On October 21, 2004, Wilmington Regional Office personnel performed a Compliance Inspection of the subject project, located at North Kerr Street in Wilmington, New Hanover County, North Carolina, The inspection was performed to determine the status of compliance with Stormwater Pen -nit Number SW8 030108, issued to you on July 23, 2003. The project has been found in violation of Stormwater Permit Number SW8 030108 issued pursuant to the requirements of 15A NCAC 2H.1000, The violations found are: Section I.5- The runoff from all built upon area within the permitted drainage area of this project must be directed into the permitted stormwater control system. A permit mod f cation must be submitted and approved prior to the construction of additional built - upon area from outside of the approved drainage area. (a) The three units located in the southwest corner of the site (behind the stormwater pond) have gutters that drain directly into the stream. All runoff and stormwater from this site must run into & through the stormwater pond. 2. Section II.2- During construction, erosion shall be kept to a minimum and any eroded areas oJ the system shall be repaired immediately. (a) Erosion from behind the pond and around the on -doing bulkhead construction is entering the creek. More silt fences and other erosion control devices must be installed to keep this sediment from entering the stream. To correct these violations you must: 1. Provide a written "Plan of Action" which outlines the actions you will take to correct the violation(s) and a time frame for completion of those actions, on or before November 25, 2004. 2. Direct the runoff flow from the gutters into the stormwater pond. The water must enter the fore -bay so it can benefit from the stormwater pond system. 3. Install more erosion control devices to help contain sediment on -site. If silt fences are used for this, they may have to be doubled up for added protection. Wilmington Regional Office 127 Cardinal Drive Extension, Wilmington, North Carolina 28405 Prone: 910-395-39001 FAX: 910-350-20041 Internet: h2o.enrstate.nc.us An Equal Opportunity/Affirmative Action Employer-- 50% Recycled110% Post Consumer Paper NorthCarolina naturally II Failure to provide the "Plan of Action" by November 25, 2004, or to correct the violations by the date designated in the "Plan of Action", are considered violations of 15A NCAC 2H.1000, and may result in the initiation of enforcement action which may include recommendations for the assessment of civil and criminal penalties, pursuant to NCGS 143-215.6A. By copy of this letter to the New Hanover County Building Inspector, this Office is requesting that the Building Inspector consider withholding building permits and Certificates of Occupancy for this project until this matter is satisfactorily resolved. If you have any questions concerning this matter, please call Gary Beecher at (910) 395-3900 Ext. 222 Sincerely, Rick Shiver Water Quality Regional Supervisor RSS:lghb S:1WQSISTORMWATINOTICE1030108.Oct04 cc: Charles Cazier (Tripp Engineering) New Hanover County Building Inspections Beth Wetherill (New Hanover County Engineering) Gary Beecher (OWQ) Central Office o�CF W r�,9QG Michael F. Easley, Governor William G, Ross, Jr., Secretary North Carolina Department of Environment and Natural Resources p Alan W. Klimek, P.E. Director Division of Water Quality October 4, 2004 Mr. Jimmy Hatcher, Member Manager Perimae & Associates,,LLC PO Box 14242 Wilmington, NC 28408 Subject: Approved Plan Revision Smith Creek Village Stormwater Project No. SW8 030108 New Hanover County Dear Mr. Hatcher: On September 10, 2004, the Wilmington Regional Office received a plan revision for Stormwater Management Permit Number SW8 030108. The revisions include the extention of the twin 48'!- pipes. It has been determined that a formal permit modification is not required for the proposed changes. We are forwarding you an approved copy of the revised plan sheet C1 for your files. Please replace the old approved plan sheet with the new one. Please be aware that all terms and conditions of the permit issued on July 23, 2003, remain in full force and effect. Please also understand that the approval of this revision to the approved plans for the subject State Stormwater Permit is done on a case -by - case basis. An.y other changes to this project must be approved through this Office prior to construction. The issuance of this plan revision does not preclude the permittee from complying7..with ail other statutes, rules, regulations or ordinances which may have jurisdiction over the proposed activity, and which may require a permit or approval prior to construction, If you have any questions concerning this matter, please do not hesitate to call me at (910) 395-3900. Sincerely, Linda Lewis Environmental,Engineer RSSlarl: S:IWQSISTORMWATIREVISiON1030108.oct04 cc: Charles Cazier, Tripp Engineering Tony';Roberts, New Hanover County Building Inspections Beth' E. Wetherill, New Hanover County Engineering Linda Lewis Wilmington_Regional- Office Central Files North Carolina Division of Water Quality 127 Cardinal Drive Extension Phone (910) 395-3900 Customer Service 1-877-623-6748 Wiimington Regional Office Wilmington, NC 28405.3845 FAX (910) 350-2004 intemet: h2o enr.state.nc.us One An Equal Opportunity/Affirmative Action Employer— 50% Recycted110% Post Consumer Paper NotihCarolina �Natrrrally oso l 0$ r���q�►10YER C°Gyf� llo� °z' NaRtHCP Beth Easley Wetherill, CPESC New Hanover County Engineering Department 230 Market Place Drive - Suite 160 Wilmington, North Carolina 28403 Phone: (910) 798-7139/Fax: (910)-798-7051 Email: bwetherill@nhcgov.com Soil Erosion Specialist SEDIMENTATION INSPECTION REPORT Project Grading Permit Project: w1LA=L Cnt'eJ.-r- Project Location: k-ei-►rl 'sue Person(s)Financially Responsibte 1, Pictures: Yes (No-) # Weather & Soil Conditions: r7W- O — 2. Is site currently under Notice of Violation: Yes o 3. Is the site in compliance with NHC Soil Erosion & Sedimentation Control Ordinance? Yes Ecircle violations below: 4. Violations: (Circle letter) (A) No approved plan. (B) Failure to follow roved plan. (C) Failure to submit revised plan. (D) Failure to provide adequate ground cover, E sufficient measures to retain sediment on site. (F) Failure to take all reasonable measures. (G) Inadequate buffer zone. (H) Goaded slopes & fills too steep. _ �Tjx lnprotected exposed slopesilure to maintain erosion control measure (K PDES Problems r v� C� Other (describe) s 5. Has off -site sedimentation occurred since last inspection? tes o Degree. Slight oder Severe Contact made with Title: nspectian report giv sent /� 7.•Inspection Report sen o person(s) esponsible: Date sent V> Ct 8. Corrective Actions Needed: _T 1AAAT F7)/A- EY_V iP o r v, c4v1_F �i o .. <11-T- �ort By: aIA LL) ovi 1. Date: f d �� �C� `Z Others present: Timeto Comply: l � cf A 07-a cTz u..e-f�, L 66V✓l.e� �� .L� Gz�ss 'A NEW HANOVER .COUNTY Engineering Department 230 Market Place Drive - Suite 160 Wilmington, North Carolina 28403 TELEPHONE 910-798-7139 Seth Easley Wetherill, C.P.E.S.C. Soil Erosion Specialist AUG I 0 2004 BY:_ July 30, 2004 Perimae & Associates, L.L.C. P.O. Box 15242, Wilmington, North Carolina 28408 CERTIFIED Re: _Notice of Violation of Land Disturbing Activity Gradine Permit Number: G.P. 3-03, Smith Creek Village Location/Description of Violations : The erosion control measures have failed to retain sediment on site 'at Smith Creek Village. You have not followed the approved plan, not submitted revised plans and failed -to properly maintain the erosion control measures. Dear Mr. Jimmy Hatcher: This letter constitutes Notice of Violation of Section 23-236, Section 23-243, Section 23-243.5, Section 23-244, Section 23-245, Section 23-248 (b), Section23- 250 (b), Section 23-251 (a) (1), Section 23-251 (b) and Section 23-252 (a) of the New Hanover County's Soil Erosion and Sedimentation Control Ordinance. Section 23-236 Basic Control Objectives states: (1) Identify critical areas. On -site areas which are subject to severe erosion, and off -site areas which are especially vulnerable to damage from erosion and /or sedimentation are to the identified and receive special attention. (2) Limit time of exposure. All land disturbing activity is to be planned and conducted to limit exposure to the shortest feasible time. (3) Limited exposed area. All land disturbing activity is to be planned and conducted to minimize the size of the area to be exposed at any one time. (4) Control surface water. Surface water runoff originating upgrade of exposed areas should be controlled to reduce erosion and sediment loss during the period of exposure. (5) Control sedimentation. All land disturbing activity is to be planned and conducted so as to prevent off -site sedimentation damage. (b) Manage stormwater runoff. When the increase in the velocity of stormwater runoff resulting from a land disturbing activity is sufficient to cause accelerated erosion of the receiving watercourse, plans are to include measures to control the velocity to the point of discharge so as to minimize accelerated erosion of the receiving watercourse, plans are to include measures to control the velocity to the point of discharge so as to minimize accelerated erosion of the site and increased sedimentation of the stream. Section 23-243 Responsibility for maintenance states: During the development of a site; the person conducting the land disturbing activity shall install and/or maintain all temporary and permanent erosion and sedimentation control measures as required by the approved plan or any provision of this article, the act, or any order adopted pursuant to these article or the act. Section 23-243.5 Restoration of areas affected by failure to comply states: The county may require a person who engaged in, a land disturbing activity and failed to retain sediment generated by the activity, as required by G.S. 113-57(3), to restore the waters and land affected by the failure so as to minimize the detrimental effects of the resulting pollution by sedimentation. This authority is in addition to any other civil or criminal penalty or injunctive relief authorized under this article. Section 23-244 Additional measures states. Whenever the county determines that significant sedimentation is occurring as a result of land disturbing activity, despite application and maintenance of protective practices, the person conducting the land disturbing activity will be required to and shall take additional protective action. Section 23-245 Areas not otherwise covered states: Notwithstanding previous provisions when it is determined that severe off -site erosion and/or sedimentation occur as a result of any land disturbing activity, regardless of the size of the site, remedial action shall be taken within a reasonable time period after notification. Notification of violation shall be submitted in writing by the county engineering department and receipted by the owner or agent responsible for the damage. Section 23-248 Erosion and sedimentation control plans states: (b) Persons conduction land disturbing activity on a tract which covers one or more acres shall file three copies of the erosion control plan with the county at least 30 days prior to beginning such activity and shall keep another copy of the approved plan and a posted copy of the permit at the job entrance on the job site before construction begins. After approving the plan, if the county either upon review of such plan or on inspection of the job site, determines that a significant risk of accelerated erosion or offsite sedimentation exists, the county will require a revised plan. Pending the preparation of the revised plan, work shall cease or shall continue under conditions outlined by the appropriate authority. Section 23-250 Inspections and investigations states: (b) If through inspection it is determined that a person engaged in land disturbing activity has failed to comply with the act, this article, or rules or orders adopted or issued pursuant to this article, or has failed to comply with and approved plan, a notice of violation shall be served upon that person by registered or certified mail or other means reasonably calculated to give actual notice. The Notice shall set forth the measures necessary to achieve compliance with the plan, specify a reasonable time period within which such measures must be completed, and warn that failure to correct the violation within the time period will result in additional civil and criminal penalties for a continuing violation. However, not time period for compliance need be given for failure to submit an erosion control plan for approval or for obstructing, hampering or interfering with an authorized representative while in the process of carrying out his official duties. If the person engaged in land disturbing activity fails to comply within the time specified, enforcement action shall be initiated. Section 23-251 Penalties states: (a) Civil penalties. (1) Any person'who violates any of the provisions of this article, or rules or orders adopted or issued pursuant to this article, or order adopted or issued pursuant to this article by the commission, or who initiates or continues a land disturbing activity for which an erosion control plan is required except in accordance with the terms, conditions, and provisions of an approved plan, shall be subject to a civil penalty. The maximum civil penalty for a violation is $5000.00 per clay. A civil penalty may be assessed from the date of violation. Each day of a continuing violation shall constitute a separate violation. The person alleged to be in violation will be notified of the violation by registered or certified mail, return receipt requested, or other means reasonably calculated to give actual notice. The notice shall describe the violation with reasonable particularity, specify a reasonable time period within which the violation must be corrected, and warn that failure to correct the violation within the time period will result in assessment of a civil penalty or other enforcement action. If, after the allotted time period has expired, the violator has not completed corrective action, a civil, penalty may be assessed from the date of the notice of violation. However, no time period for compliance need be given for failure to submit an erosion control plan for approval or for obstruction, hampering or interfering with an authorized representative while in the process of carrying out his official duties. Each day of continuing violation shall constitute a separate violation. (b) Criminal penalties. Any person who knowingly or willfully violates any provision of this article, or rule or order adopted or issued pursuant to this article, or who knowingly or willfully initiates or continues a land disturbing activity for which an erosion control plan is required except in accordance with terms, conditions, and provisions of an approved plan, shall be guilty of a Class 2 misdemeanor which may include a fine not to exceed $5000.00 per calendar day. Section 23-252 Iniunctive relief states: (a) Whenever the governing body has reasonable cause to believe that any person is violating or threatening to violate this article or any rule or order adopted or issued pursuant to this article, or any term, condition, or provision of an approved erosion control plan, it may, either before or after the institution of any other action or proceeding authorized by this article; institute a civil action in the name of the county, for injunctive relief to restrain the violation or threatened violation. The action shall be brought in the superior court of the county. Corrective measure(s)needed and Time to Comp! : Remove all sediment that has been deposited in the offsite creek, stabilize or remove the sediment deposited in the offsite yard, repair the erosion to the adjacent driveway and restore the driveway, with permission from the adjacent property owner, within 1 working day of receipt of this notice. Immediately reinstall all erosion control measures as per the approved plan within 1 calendar day of receipt of the notice of violation. And resubmit plans to show the changes to the plan for the culvert installation and how the velocity will be reduced to eliminate offsite erosion within 1 week of receipt of this notice. You can contact Beth Easley Wetherill, Erosion Control Specialist, Engineering Department, 230 Market Place Drive, Suite 160, Wilmington, North Carolina 28403, (910) 798-7139, regarding the required compliance action. Sincerely, Beth Easley Wetherill Soil Erosion Specialist . New Hanover County cc: Dave Weaver, Assistant County Manager Greg Thompson, PE., County Engineer Kemp Burpeau; Deputy County Attorney Mark Boyer, NHC Public Information' Linda Lewis, DENR Stormwater Noelle Lutheran, DENR Wetlands Jeniffer Frye,.U.S. Corps of Engineers Ron Satterfield, City of Wilmington [IREC�EIVVED S E P 10 Z004 BY: To: %F TRPP ENGL-,N-EERLNG, P.C. 19 Chestnut Street, tiff ilmin�ton. NC ? S 01 Phone: (910) 76-3-5100 • FAX: (910) 763-D-63 1 Email: trinpenacaec. s.com Acte,ncion: Lj--j-DA Lewis Suoiect; St,J 03oti FAX TRANSiM-iiAL: NUMScR Or= RgGSS ?NC_UDSS COV=R i am sending vou: ( ;./-1nts { } TrGcincs ( ) Copv of iet _- ( ) Speci�ications ( ? Ocher C�blcc lier�l NQ. JeSC'l�Cign et These are transmitted as cchec!cer oelow: (✓ Approval ()-, or Your Use ( ) Sicn & Return ( ) Review cc: S, ., "f • r � S i Permit No. �'Y03o/a'V (to be provided by DJVQ) State of North Carolina Department of Environment and Natural Resources Division of Water Quality STORMWATER MANAGEMENT PERMIT APPLICATION FORM WET I)ETENTION BASIN SUPPLEMENT This jbrm may be photocopied for use as an original DWO Stormwater Management Plan Review: A complete stormwater management plan submittal includes a wet detention basin supplement for each basin, design calculations, plans and specifications showing all basin and outlet structure details, and a signed and notarized operation and maintenance agreement. I. PROJECT INFORMATION (please complete the following information): Project Name: Smith Creek Village Contact Person: Charles D. Cazier Phone Number: ( 910) 763-5100 For projects with multiple basins, specify which basin this worksheet applies to: 1 elevations Basin Bottom Elevation 20.5 ft. (floor of the basin) Permanent Pool Elevation 27.0 ft. r (elevation of the orifice) Temporary Pool Elevation 28.5 ft. (elevation of the discharge structure overflow) areas Permanent Pool Surface Area 11,265 sq.ft. (water surface area at the orifice elevation Drainage Area 9.72 ac. (on -site and off -site drainage to the basin) Impervious Area 4.23 ac. (on -site and off -site drainage to the basin) volumes Permanent Pool Volume 38,961 cu.ft. (combined volume of main basin and forebay) Temporary Pool Volume 18.372 cu.ft. (volume detained above the permanent pool) Forebay Volume 8 048 cu.ft. (approximately 20% of total volume) Other parameters SA/DA i Diameter of Orifice Design Rainfall Design TSS Removai2 2.0 (surface area to drainage area ratio from DWQ table) 1.75 in. (2 to 5 day temporary pool draw -down required) 1.0 in. 90 % (minimum 85% required) Form SWU-lot Rev 3.99 Page 1 of 4 A Footnotes: l , When using the Division SA/DA tables, the correct SA/DA ratio for permanent pool sizing should be computed based upon ilic actual impervious % and permanent pool depth. Linear interpolation should be employed to determine the correct valuc for non- standard table entries. 2. In the 20 coastal counties, the requirement for a vegetative filter may be waived if the wet detention basin is designed to provide 90% TSS removal. The NCDENR BMP manual provides design tables for both 85% TSS removal and 90%. TSS removal, I1. REQUIRED ITEMS CHECKLIST The following checklist outlines design requirements per the Stormwater Best Management Practices Manual (N.C. Department of Environment, Health and Natural Resources, February 1999) and Administrative Code Section: 15 A NCAC 2H .1008. Initial in the space provided to indicate the following design requirements have been met and supporting documentation is attached. if the applicant has designated an agent in the Stormwater Management Permit Application Form, the agent may initial below. If a requirement has not been met, attach justification. Applicants Initials _ Q M _ a, The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet). CM b. The forebay volume is approximately equal to 20% of the total basin volume. ( c. The temporary pool controls runoff from the design storm event. d. The temporary pool draws down in 2 to 5 days. Cal e. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations). f. The basin length to width ratio is greater than 3: 1. g. The basin side slopes above the permanent pool are no steeper than 3:1. h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail). LQC i. Vegetative cover above the permanent pool elevation is specified. 0% j. A trash rack or similar device is provided for both the overflow and orifice. L k. A recorded drainage easement is provided for each basin including access to nearest right- of-way. ZOL I. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified to be performed prior to use as a wet detention basin (, m. A mechanism is specified which will drain the basin for maintenance or an emergency. Ill. WET DETENTION BASIN OPERATION AND MAINTENANCE AGREEMENT The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the vegetated filter if one is provided. This system (check one) ❑ does X does not incorporate a vegetated filter at the outlet. This system (check one) ❑ does X does not incorporate pretreatment other than a forebay. Form SWU-102 Rev 3.99 Page 2 of 4 L Maintenance activities shall be performed as follows: After every significant runoff producing rainfall event and at least monthly: a. Inspect the wet detention system for sediment accumulation, erosion, trash accumulation, vegetated cover, and general condition. b. Check and clear the orifice of any obstructions such that drawdown of the temporary pool occurs within 2 to 5 days as designed. 2. Repair eroded areas immediately, re -seed as necessary to maintain good vegetative cover, mow vegetative cover to maintain a maximum height of six inches, and remove trash as needed. 3. Inspect and repair the collection system (i.e. catch basins, piping, swale$, riprap, etc.) quarterly to maintain proper functioning. 4. Remove accumulated sediment from the wet detention basin system semi-annually or when depth is reduced to 75% of the original design depth (see diagram below). Removed sediment shall be disposed of in an appropriate manner and shall not be handled in a manner that will adversely impact water quality (i.e. stockpiling near a wet detention basin or stream, etc.). The measuring device used to determine the sediment elevation shall be such that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the permanent pool depth reads 4.875 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 2.25 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM (fill in the blanks) Permanent Pool Elevation 27.0 Sediment RVni EL24.75J171.o---Sediment Removal Elevation 22.125 Bottomtion 24.0 --------------------------------------------125-31. ---- Bottom Elevation 20.50 FOREBAY MAIN POND 5. Remove cattails and other indigenous wetland plants when they cover 50% of the basin surface. These plants shall be encouraged to grow along the vegetated shelf and forebay berm. 6. If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through the emergency drain shall be minimized to the maximum extent possible. Form SWU-102 Rev 3.99 Page 3 of 4 k 7. All components of the wet detention basin system shall be maintained in good working order. acknowledge and agree by my signature below that I am responsible for the performance of the seven maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Print name: Mr. Jimmy Hatcher Title- Member Manager Address: ^ Perimae & Associates, LLC, P.O. Box 15242, Wilmington, NC 28408 Phone Signat Date Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. 1, Della C. Baird , a Notary Public for the State of North Carolina , County of Pender do hereby certify that _ Jimmy Hatcher personally appeared before me this Z.3 day of December 2002 , and acknowledge the due execution of the forgoing wet detention basin maintenance requirements., Witness my hand and official seal, SEAL My commission expires 10/15/06 Form SWU-102 Rev 3.99 Page 4 of 4 1 f 14l2003 CDC Smith Creek Village Stormwater Calculations 02115 Total Drainage Area sq. ft. acres 423,403 9.72 Impervious Area Land Use s . ft. acres buildings 56,167 1,29 arkin las halt 107,299 2,46 sidewalks 20,749 0,48 Total 184,215 4.23 Stormwater Calculations: Time of Concentration: Hydraulic Length (L) = 1,350 ft. change in Height (H) = 6 ft. Tc = (Ln IH)" 1 128 16.17 min. Flow for 2 year, 6 hour Storm (Q2): QPRE = (CPRO x (Itp) x (Area) 14.29 cis QPosr = (CPosT) x (Ito) x (Area) 32.01 cfs sou btora a capacityuapacity for z year storm: CN = (98)(% imp.) + (60)(1-% imp.) 77 P = 3.30 in. forlyr, 6 hr storm S. = 10001CN - 10 2.99 Depth (D)= [P-(0.2)(S)]2 1 [P+(0.8)(S)] 1.28 in. Time to Peak Fiow: TP = [(43.5)(D)(Area)] 1 Q2,P05T 16.96 min. Detention Pond Design: Pond Size: Elevation ft. Surface Area (sq. ft. Normal Pool 27.00 11,265 Flood Pool 28.50 13,231 Top of Bank 32.50 19,094 Bottom of Pool 20.50 723 J % impervious = 0.435 = 43.5% say 44.0% CPRE = 0.25 CPosr = (% imp.)(.95)+(1-% imp.)(.25) 0.56 1, = 5.88 inlhr Its = 6.30 in/hr Flow for 10 year, 6 hour Storm (Qjo): QPflE _ (CPRE) x (125) x (Area) = 15.31 cis Q Posr = (CP=) x (125) x (Area) = 34.29 cfs oon awFa o e-apacny for au year zworm: CN = (98)(% imp.) + (60)(1-% imp.) 77 P = 4.82 in.' for 10 yr, 6 hr storm S= 1000lCN-10 = 2.99 Depth (D)= [P-(0,2)(S)121 [P+(0,8)(S)1 = 2,47 in. Time to Peak Flow: TP = ((43.5)(D)(Area)] I Qto,Pos'r = 30.49 min. State Surface Area Requirement at normalpool: Pond side slopes = 3 :1 Depth below N.P. = 6.5 ft. SAlDA = 0.0200 (Chart for 90% TSS Removal for Wet Detention Pond without Ve etative Filter Required SA = (SAIDA) x (Total Drainage Area) 8.468 s . ft. Provided Stora a Volume: State Volume Required for Storage of first 1" of runoff: Vol. _ [(Normal pool SA + Flood Pool SA) 1 21 Rv = .05+ ,009(% imp) x (F.P. elev. - N.P. elev.) = 0.441574 18,372 cu. ft. V= (Design rainfall)(Rv)(Drainage Area) 15.580 cu.ft. ����►�t [ l [ rruU��� RECEIV"'D :a SEAL JAN 16 2003 17374CL DWQ f PR of # 02115Pond 1 of 3 1/14/2003 Smith Creek Village 02115 CDC Stormwater Calculations Pond Volume: Bottom SA = 723 sq. ft. Normal Pool SA = 11,265 sq. ft. Vol. _ [(N.P. SA+ Bottom SA) 1 21 x (N.P. el. - Bottom el.) ✓ = 38,961 cu. ft. Forebay- Required Volume Vol. = 20% of storage volume 7,792 cu. ft. Outlet Structure Design: Flow for 2-day drawdown: for 1st 1" of stormwater, Q = Required Vol, 1 172,800 sec. (2-days) 0.090 cfs Required Area of Pipe for 2-day drawdown: A= QI[CdxSQRT(2xgxh)] Cd = 0.6 9 = 32.2 ftJs2 h = (F.P, elev.- N.P. elev.)12 0.75 ft. A = 0.0216 sq. ft. Diameter of Pioe for 2-dav drawdown DIA. = SQRT[(A x 4) ! pi1 0.1659 ft. = 1.99 in. 'Use: 1.75 in diameter pipe Outlet Structure Check: Using a 4' x 4' Basin, Perimeter L = 16 ft. Q = CIA C imp.)(.95) + (1-% imp.)(.25) 0.56 1 = 6.30 in. for a 25 yr. Storm A = 9.72 Acres 34.29 cfs Q= CwxLxH"5 H= [Q1(CwxQj- Cw = 3 — 0,80 ft, Peak elevation = flood pool elevation + H 29.30 ft. Provided Volume Bottom SA = 1,689 sq. ft. Normal Pool SA = 3,676 sq. ft. Vol. _ [(N.P. SA + Bottom SA) 121 x (N.P. ei. - Bottc = 8,048 cu. ft. J depth = 3 ft. Flow for 5-dax drawdown: for 1st 1" of stormwater, Q = Required Vol. 1432,000 sec. (5-days) 0.036 C£s Required Area of Pie for 5-day drawdown: A= Q/ [Cd x SQRT(2 x g x h)] Cd = 0.6 g = 32.2 ft.ls2 h = (F.P. elev. - N.P. elev.) 12 0.75 ft. A = 0.0086 sq. ft. Diameter of Pipe for 5-day drawdown: DIA. = SQRT[(A x 4) 1 pi] 0.11149 ft. 1.26 in. 02115Pond 2 of 3 O�OF W A rFRQG Michael F. Easley, Governor y William G. Ross Jr., Secretary North Carolina Department of Environment and Natural Resources Alan W. Klimek, P.E. Director Division of Water Quality Mr. Jimmy Hatcher, Manager Perimae & Associates, LLC P.O. Box 15242 Wilmington, NC 28408 Subject Dear Mr. Hatcher: April 2, 2003 REQUEST FOR ADDITIONAL INFORMATION Stormwater Project No. SW8 030108 Smith Creek Village New Hanover County The Wilmington Regional Office received a Stormwater Management Permit Application for Smith Creek Village on January 16, 2003. A preliminary review of that information has determined that the application is not complete. The following information is needed to continue the storrrlwater review: Please add the nearest intersection of two major roads to the vicinity map. A major road is any 1, 2 or 3 digit NC, US or interstate highway. 2. Please turn off the tree layer on the plans in order to see the spot elevations more clearly. 3. Please provide dimensions for the buildings. 4. Please add a note to the plans that all roof drains must be directed into the detention pond. 5. Please provide contours and dimensioning for the pond. This should include labeling the radii of the curves. Also, please label the permanent pool contour. Please note that this request for additional information is in response to a preliminary review. The requested information should be received by this Office prior to May 2, 2003, or the application will be returned as incomplete. The return of a project will necessitate resubmittal of all required items, including the application fee. #V 9.r N. C. Division of Water Quality 127 Cardinal Drive Extension (910) 395-3900 Customer Service GA Wilmington Regional Office Wilmington, NC 28405 (910) 350-2004 Fax 1 800 623-7748 NCDENR Mr. Hatcher April 2, 2003 Stormwater Project No. SW8 030108 If you need additional time to submit the information, please mail or fax your request for a time extension to the Division at the address and fax number at the bottom of this letter. The request must indicate the date by which you expect to submit the required information. The Division is allowed 90 days from the receipt of a completed application to issue the permit. The construction of any impervious surfaces, other than a construction entrance under an approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject to enforcement action pursuant to NCGS 143-215.6A. Please reference the State assigned project number on all correspondence. Any original documents that need to be revised have been sent to the engineer or agent. All original documents must be returned or new originals must be provided. Copies are not acceptable. If you have any questions concerning this matter please feel free to call me at (910) 395-3900. - - - - - Sincerely, Laurie Munn Environmental Engineer RSS/:Ism S:IWQSISTORMWATIADDINFO120031030108.apr03.doc cc: Laurie Munn Charles D. Cazier WET DETENTION POND ANALYSIS FILE NAME: #VALUE! PROJECT #: SW8 30108.00 PROJECT NAME: Smith Creek Village REVIEWER: Laurie Munn DATE: 31-Mar-03 Receiving Stream: Un Trib to Spring Branch Class: C-SW Drainage Basin: Cape Fear Index No. Site Area 9.72 acres Drainage Area 423403 20 square feet Area in Acres 9.72 IMPERVIOUS AREAS Rational C 561 Q7.00 OC1'29.00 20749.00 TOTAL SURFACE AREA CALCULATION % IMPERVIOUS 43.49% Des. Depth 6.5 TSS: 90 square feet square feet square feet square feet square feet square feet square feet Rational Cc= 0.11 SAIDA Ratio 1.97% Req. SA 8360 sf Prov. SA 126 sf VOLUME CALCULATION " place a "1" in the box if Rational is used Rational ?* Des. Storm 1 ..O:-. - a inches Rv= 0.441 Bottom 20.5 msl Perm. Pool »:7.00 msl Design Pool 28.5 msl Storage met @elev 28.27 msl Req. Volume':5575:: cf Vol. Prov. at DP ::1:$72: cf FICE CALCULATION FOREBAY Perm. Pool Volume= Req. Forebay Volume= Provided Volume= Percent= Elevation 2T00 28.50 Area 11265,00 13231.00 Inc. Vol. Acc. Vol. 18372.00 18372, 00 Avg. Head = 0.71 ft Q2 Area = 3.19 sq. inches Flow Q2, cfs 0,090 cfs Q5 Area = 1.28 sq. inches Flow Q5, cfs 0.036 cfs Orifice Area 2.41 sq. inches No. of Orifices 0.068 cfs Diameter, inches 1. 75: weir H x W in x in Drawdown days Surface Area @DP = 13231 sq. ft. Falling Head Drawdown = 4.3 days COMMENTS Surface Area , Volume and Orifice are within Design Guidelines, January 15, 2003 Stormwater Narrative Smith Creek Village Wilmington, NC TE 02115 Smith Creek Village is an existing vacant 9.72 acre tract of land. A townhome community of 55 units with asphalt parking, sidewalks and recreational area is proposed. The built upon area consists of 56,167 sf of buildings, 107,299 sf of parking and access area, and 20,749 sf of concrete sidewalks totaling 184,215 sf or 43.5% impervious. The site will be considered high density. Runoff will be treated by wet detention. The pond is designed to treat both the State's 1" and the City's 10-year pre -post requirements. Outflow will be to an unknown tributary of Spring Branch, Classification C-SW. TRIPP ENGINEERING, P.C. 419 Chestnut Street Wilmington, North Carolina 28401 Phone: 910-763-5100 • FAX: 910-763-5631 May 16, 2003 NCDENR Division Water Quality 127 Cardinal Drive Wilmington, NC 28405-3845 Attn: Ms. Laurie Munn Re: Smith Creek Village SW8 030108 New Hanover County, NC TE 02115 Dear Laurie: In response to your correspondence dated April 2, 2003, we offer the following: 1. Vicinity map has been revised. 2. Tree layer has been removed. 3. Building dimensions have been provided, sheet C2. 4. Note regarding roof drains has been added. 5. Contours and dimensioning have been provided for the pond, sheet C2. Please review for approval and contact us with any questions, comments or if you need additional information. Thank you. Sincerely, Tripp Engineering, P.C. Jacqu ine King JK:dcb Enc. O a - 'm E o � � k w Q U o❑❑ CD in } r' 1E N 8 Z cs CC y ®.❑ ❑ ¢ C6 v N m m Q o m o V 'y « ] (} 0 p (+7 a y N -2 O V5 U U a)a ZID Z - M N LC -y O U N 0 Y O a r m co: Q1 N E C E C . 2 y 20 U U O d N w mt o "Y ji d (on Q O ■ ■ ■ ' a N Ir m ru Ln 0 0 0 ['a L7 d Iq ru C3 0 I- CC E m U E 0 O 0 N tm 7 7 Q co co ro a LL c� N0 o m Z a �0�6� iLd�0. .=0-0 p r M. —114N S X 0 N L C a N Lo 2 C 00 L ? N F (� CL cA CD G vz� a �nQ�3 a� c