The URL can be used to link to this page

Home My WebLink AboutNC0004961_ID of New Discharges_20140930 Riverbend Steam Station Ash Basin Plan for Identification of New Discharges NPDES Permit NC0004961 September 30, 2014 Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin REPORT VERIFICATION i Report Verification PROJECT: GROUNDWATER MONITORING PROGRAM RIVERBEND STEAM STATION ASH BASIN NPDES PERMIT NC0004961 TITLE: PLAN FOR IDENTIFICATION OF NEW DISCHARGES This document has been reviewed for accuracy and quality commensurate with the intended application. Prepared by:______ _______________ Date:____________ ______ Checked by:______ _______________ Date:____ ______________ Approved by:_____ ________________ Date:___________________ Project Manager: Brooke Ahrens, PE Professional Engineer Seal: HDR Engineering, Inc. of the Carolinas 440 South Church St., Suite 1000 Charlotte, NC 28202 North Carolina Engineering Firm Number F-0116 Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin TABLE OF CONTENTS ii Table of Contents Page Report Verification ......................................................................................................................... i Table of Contents .......................................................................................................................... ii List of Figures .............................................................................................................................. iii Section 1 - Introduction ................................................................................................................. 1 Section 2 - Site Description ........................................................................................................... 3 2.1 Plant Description ................................................................................................... 3 2.2 Ash Basin Description ........................................................................................... 3 Section 3 - Site Geology and Hydrogeology ................................................................................. 4 3.1 Site Geologic/Soil Framework ............................................................................... 4 3.2 Site Hydrogeologic Framework ............................................................................. 4 Section 4 - Identification of New Discharges ................................................................................ 6 4.1 Purpose of Inspection ............................................................................................ 6 4.2 Seepage ................................................................................................................ 6 4.3 Area To Be Inspected for New Discharges ........................................................... 6 4.4 Inspection Procedure ............................................................................................ 6 Section 5 - References ................................................................................................................. 7 Appendices A – Riverbend Station Ash Basin – Inspection for Identification of New Discharges Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin LIST OF FIGURES iii List of Figures Figure 1 – Site Location Map Figure 2 – Areas To Be Inspected For Seeps Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin SECTION 1 - INTRODUCTION 1 Section 1 - Introduction The purpose of this document is to address the requirements of North Carolina General Statute (GS)130A-309.210 (d) Identification and assessment of discharges; correction of unpermitted discharges, as modified by North Carolina Senate Bill 729, for the Riverbend Steam Station (RBSS) ash basin operated under National Pollutant Discharge Elimination System (NPDES) Permit NC0004961. The following requirements are contained in General statue 130A-309.210: d) Identification of New Discharges. – No later than October 1, 2014, the owner of a coal combustion residuals surface impoundment shall submit a proposed Plan for the Identification of New Discharges to the Department for its review and approval as provided in this subsection. (1) The proposed Plan for the Identification of New Discharges shall include, at a minimum, all of the following: a. A procedure for routine inspection of the coal combustion residuals surface impoundment to identify indicators of potential new discharges, including toe drain outfalls, seeps, and weeps. b. A procedure for determining whether a new discharge is actually present. c. A procedure for notifying the Department when a new discharge is confirmed. d. Any other information related to the identification of new discharges required by the Department. (2) The Department shall approve the Plan for the Identification of New Discharges if it determines that the Plan complies with the requirements of this subsection and will be sufficient to protect public health, safety, and welfare; the environment; and natural resources. (3) No later than 30 days from the approval of the Plan for the Identification of New Discharges, the owner shall begin implementation of the Plan in accordance with the Plan. The North Carolina Senate Bill 729 establishes the submittal date of this Plan for Identification of New Discharges no later than October 1, 2014. This bill also modified GS 130A to establish the following submittals that are related to this Plan. GS130A-309.210(a) was modified to require: (2) No later than December 31, 2014, the owner of a coal combustion residuals surface impoundment shall submit a topographic map that identifies the location of all (i) outfalls from engineered channels designed or improved for the purpose of collecting water from the toe of Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin SECTION 1 - INTRODUCTION 2 the impoundment and (ii) seeps and weeps discharging from the impoundment that are not captured by engineered channels designed or improved for the purpose of collecting water from the toe of the impoundment to the Department. The topographic map shall comply with all of the following: a. Be at a scale as required by the Department. b. Specify the latitude and longitude of each toe drain outfall, seep, and weep. c. Specify whether the discharge from each toe drain outfall, seep, and weep is continuous or intermittent. d. Provide an average flow measurement of the discharge from each toe drain outfall, seep, and weep including a description of the method used to measure average flow. e. Specify whether the discharge from each toe drain outfall, seep, and weep identified reaches the surface waters of the State. If the discharge from a toe drain outfall, seep, or weep reaches the surface waters of the State, the map shall specify the latitude and longitude of where the discharge reaches the surface waters of the State. f. Include any other information related to the topographic map required by the Department. The inspection procedures presented in this plan, developed to satisfy the requirements of GS130A-309.210(d), will be used as the basis for developing the topographic map required by GS130A-309.210(a)(2). Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin SECTION 2 - SITE DESCRIPTION 3 Section 2 - Site Description 2.1 Plant Description RBSS is a former coal-fired electricity generating facility which had a capacity of 454 megawatts located in Gaston County, North Carolina, near the town of Mt. Holly (Figure 1). As of April 1, 2013, all of the coal-fired units have been retired. The site is located between the south bank of the Catawba River on Mountain Island Lake and the north side of Horseshoe Bend Beach Road. The surrounding area generally consists of residential properties, undeveloped land, and Mountain Island Lake 2.2 Ash Basin Description The ash basin system consists of a Primary Cell and a Secondary Cell, separated by an intermediate dike. The ash basin at RBSS originally consisted of a single-cell basin commissioned in 1957 and was expanded in 1979. The single basin was divided by constructing a divider dike to form two separate cells in 1986. The ash basin is located approximately 2,400 feet to the northeast of the power plant, adjacent to Mountain Island Lake, as shown on Figure 2. The Primary Cell is impounded by an earthen embankment dike located on the west side of the Primary Cell. The Secondary Cell is impounded by an earthen embankment dike located along the northeast side of the Secondary Cell. The surface area of the Primary Cell is approximately 41 acres with an approximate maximum pond elevation of 724 feet. The surface area of the Secondary Cell is approximately 28 acres with an approximate maximum pond elevation of 714 feet. The full pond elevation of Mountain Island Lake is approximately 646.8 feet. The ash basin system was an integral part of the station’s wastewater treatment system which predominantly received inflows from the ash removal system, station yard drain sump, and stormwater flows. During station operations, inflows to the ash basin were highly variable due to the cyclical nature of station operations. The inflows from the ash removal system and the station yard drain sump are discharged through sluice lines into the Primary Cell. The discharge from the Primary Cell to the Secondary Cell is through a concrete discharge tower located near the divider dike. Although the station is retired, wastewater effluent from other non-ash-related station discharges to the ash basin is discharged from the Secondary Cell, through a concrete discharge tower, to Mountain Island Lake. The concrete discharge tower drains through a 30- inch-diameter corrugated metal pipe into a concrete-lined channel that discharges to Mountain Island Lake. The ash basin pond elevation is controlled by the use of concrete stop logs. Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin SECTION 3 - SITE GEOLOGY AND HYDROGEOLOGY 4 Section 3 - Site Geology and Hydrogeology 3.1 Site Geologic/Soil Framework Riverbend and its associated ash basin system are located in the Charlotte terrane of the Carolina Zone (Pippin et al. 2008), or as described in the older belt terminology, the Charlotte Belt of the Piedmont physiographic province (Piedmont) (North Carolina Geological Survey 1985). The Charlotte terrane is characterized by mostly felsic to mafic plutonic rocks which intrude a suite of mainly metaigneous rocks and minor metasedimentary rocks (Pippin et al. 2008). The soils that overlie the bedrock in the area have generally formed from the in-place weathering of the parent bedrock. The fractured bedrock is overlain by a mantle of unconsolidated material known as regolith. The regolith, where present, includes the soil zone; a zone of weathered, decomposed bedrock known as saprolite; and alluvium. Saprolite, the product of chemical and mechanical weathering of the underlying bedrock, is typically composed of silt and coarser granular material up to boulder size and may reflect the texture of the rock from which it was formed. The weathering products of felsic rocks may be sandy- textured and rich in quartz content while mafic rocks form a more clayey saprolite (LeGrand 2004). 3.2 Site Hydrogeologic Framework Piedmont topography is characterized by gently rounded sloped hills and valleys. Recharge typically occurs on upland areas and slopes while groundwater discharge is concentrated in surface water bodies and lowland areas. LeGrand’s (1988, 2004) conceptual model of the groundwater setting in the Piedmont incorporates the above two medium systems into an entity that is useful for the description of groundwater conditions. That entity is the surface drainage basin that contains a perennial stream or river (LeGrand 1988). Each basin is similar to adjacent basins and the conditions are generally repetitive from basin to basin. Within a basin, movement of groundwater is generally restricted to the area extending from the drainage divides to a perennial stream or river (Slope-Aquifer System; LeGrand 1988, 2004). Rarely does groundwater move beneath a perennial stream or river to another more distant stream (LeGrand 2004). Therefore, in most cases in the Piedmont, the groundwater system is a two-medium system (LeGrand 1988) restricted to the local drainage basin. The groundwater occurs in a system composed of two interconnected layers: residuum/saprolite and weathered rock overlying fractured crystalline rock separated by the transition zone. Typically, the residuum/saprolite is partly saturated and the water table fluctuates within it. Water movement is generally through the fractured bedrock. The near-surface fractured crystalline rocks can form extensive aquifers. The character of such aquifers results from the combined effects of the rock type, fracture system, topography, and weathering. Topography exerts an influence on both weathering and the opening of fractures while the weathering of the crystalline rock modifies both transmissive and storage characteristics. Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin SECTION 3 - SITE GEOLOGY AND HYDROGEOLOGY 5 The aquifer system in the Piedmont typically exists in an unconfined or semi-confined condition in the bedrock zone. Under natural conditions, the general direction of groundwater flow can be approximated from the surface topography. Groundwater moves both vertically down through the regolith and parallel to the bedrock surface to areas where groundwater discharges as seepage into streams, lakes, or other surface water bodies. RBSS is located on a peninsula in the Catawba River on the north side of Horseshoe Bend Beach Road (Figure 2). This road runs generally west to east and is located along a local topographic divide. Based on the slope-aquifer system, groundwater at the site is expected to flow downward from this topographic divide to the ash basins and discharge into Mountain Island Lake (Catawba River). Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin SECTION 4 - IDENTIFICATION OF NEW DISCHARGES 6 Section 4 - Identification of New Discharges 4.1 Purpose of Inspection The purpose of the inspection is to identify new discharges and indicators of potential new discharges, including toe drain outfalls, seeps, and weeps associated with the coal combustion residuals surface impoundment (ash basin). 4.2 Seepage Seepage is considered to be the movement of wastewater from the ash basin through the ash basin embankment, the embankment foundation, the embankment abutments, or through residual material in areas adjacent to the ash basin. A seep is defined in this document as an expression of seepage at the ground surface. A weep is understood to have the same meaning as a seep. Indicators of seepage include areas where water is observed on the ground surface and/or where vegetation suggests the presence of seepage. Seepage can emerge anywhere on the downstream face, beyond the toe, or on the downstream abutments at elevations below normal pool. Seepage may vary in appearance from a "soft," wet area to a flowing "spring." Seepage may show up first as only an area where the vegetation is lusher and darker green than surrounding vegetation. Cattails, reeds, mosses, and other marsh vegetation often become established in a seepage area.1 However, in many instances, indicators of seeps do not necessarily indicate the presence of seeps. 4.3 Area To Be Inspected for New Discharges The areas to be inspected are the areas of the site where water contained in the ash basin might infiltrate into the underlying residual material and be expressed as seepage. This would include the earthen embankment which impounds the ash basin and certain adjacent areas. The extent of the areas to be inspected was determined based on the generalized LeGrand conceptual model and the concept of the slope-aquifer system and the site topography. In this generalization, flow of water from the ash basin would be expected to be located within the slope-aquifer compartment and to be below the full pond elevations of the ash basins. The area to be inspected is shown on Figure 2. 4.4 Inspection Procedure The inspection procedure for identification of new discharges and indicators of potential new discharges associated with the RBSS ash basin system is provided in Appendix A. In addition to the specific requirements for the inspection, Appendix A also provides the general requirements, the frequency of inspections, documentation requirements, and provides a decision flow chart for determining if the potential new discharge is associated with the ash basin. 1 Dam Operation, Maintenance, and Inspection Manual, North Carolina Department of Environment and Natural Resources, Division of Land Resources, Land Quality Division, 1985 (Revised 2007). Duke Energy Carolinas, LLC | Plan for Identification of New Discharges Riverbend Steam Station Ash Basin SECTION 5 - REFERENCES 7 Section 5 - References North Carolina Geological Survey, 1985, Geologic map of North Carolina: North Carolina Geological Survey, General Geologic Map, scale 1:500000. LeGrand, H.E. 1988. Region 21, Piedmont and Blue Ridge, p.201-208, in Black, W., Rosenhein, J.S., and Seaber, P.R., eds., Hydrogeology: Geological Society of America, The Geology of North America, v. O-2, Boulder, Colorado, 524p. LeGrand, Harry, Sr. 2004. A Master Conceptual Model for Hydrogeological Site Characterization in the Piedmont and Mountain Region of North Carolina, North Carolina Department of Environment and Natural Resources. Pippin, Charles G., Chapman, Melinda J., Huffman, Brad A., Heller, Matthew J., and Schelgel, Melissa E. 2008. Hydrogeologic Setting, Ground-Water Flow, and Ground-Water Quality at the Langtree Peninsula Research Station, Iredell County, North Carolina, 2000-2005, United States Geological Survey, Prepared in cooperation with the North Carolina Department of Environment and Natural Resources, Division of Water Quality. Figures 1 MAY 14, 2014 SEPTEMBER 30, 2014 - . , - -, . . .. . � .,�. ., �. - . I :�( . ., - `;' . � . 1, . r a 3r �'`',rrTF l ', tl- �r '-4: r 'it yr':, r' ..•1 . $ .y� * r �y , , . ir , _,t ,P, :� < . )-: y" :r""+r. l: ss:i,. -d-': �.-_ 1 -;.;. 'ti 3 . >Yk 3`�';:� '•_4s ..�� .'-& ,C" r' .�' y '. 4 . r : "K. % r 9Jr .r, . • 9r _ _ 1` {F p, 3 �R C. i R M': r :d r + 54 _�..t .f r• .. . '. r' . 6 r. �s - 4 i f'� I J ` "r . a r @ r. aI � ! 4 ' `r �a+h s , . �n� ? r' { 7P = t Zr �• i t. N r E r� - :' i 'F 'F S � k - } �• is ' 3 x ': , ,. . . . -(.. _ .. 3 y¢ 7^"rf . i - .r,.e. _ _ __ i . rx x. _ ".!),;��- r, yrJ '. n�. ^�r 1%. . L . . %. . . �-,f . - } '� . ,...5 V . �. a.,l(` .lRy _ i�^.!. % . I f. -I - — ,� ., f - - .. •4 '] ' -... yam. ` !' ..' X n 'yam �•' 9 I� t •' +. 1-1 ' Je■ w , ' -r" �, , . � .-,� r.. .,., . . 41'. 1',� �'. " . ,_ '. .� . , � -,� , « ` + _ . *Wi , xr ' 'l. _ r,r".s S �,' ' , " .,.. r - �r a *- t r k z.[ �,. fir: :. • +,y ,'Y i ,�'' ,• fib' •;'� ;' _ '•'� ..':2 " 1. 8•, .µh`<-l: ��WW •'W''. �. Mi . -.l v'::'tl-.=SF,,s '�I TF _ ;:'i'.:J; — yy :. �` , ;. %, . "- '. a z::. ^ x S 4' � 4 'Tr ' ,' " t : yyam[ d j Jr nA, A, , Y+' 1r, �'1 ' � L'ti ` h' l' Y �. >• 1 y ]r ` r ``n . blp' 'A1 ';r K 'Y'*P• L -d '.. .- ,1�, �•i. 4, -t e+ ,k'>"'_ ...� . ° _ a ,£' ;� , w $".: 'i: '4 s. •}� r u `.. Y ,a r : �� ss.. % r. ., r �' 5° 1ri 4 -�L, * -1 •'r.Je a. '.s'. 4„i �` �R`. �Y 'fir •bxAM' .,, } a , r ` �■R4 '. t - N ti r " yy 1t�.', �. 's. C.. ., d I' p' br ,'.: t M ? - T V .. , r, `;. [ \:%t' . �, 1 ram• _ . . x . 11 ` .•- S. :::; x c :y� 'r�'.I ..r - . r Y o .. E 1 e : _ . ' F' .3 ..3 .Y'n .J ! j ii� ti tI. W'' r. r' '�e �;]j{ 4 p1Y A r. y. .'.. :m �" xil - t �'' ,,� 'F" i# t a' T .,K A'.. }� ..+Y• ` '. ..f } 2 - r A P r 1 Lx F c ;�' 9..,T �✓ '.1 f. b' w . ,. - .�. r of .: . d ~ ..4 ,� T S ,� ] ^ham ' �� r>;: y L C c i '.[ .. 4' i •• 9.'. Y . (�y� �. " Y' TS. A' S •�S'r x a` t: d ` ` �. �4 i �. > �" r,rt. } 4 '�y . s 'i _ 1 : F. F 7 t �� ". �$, yr i '-• .^.' ' 'ip .IMF. * - .P L, !. y{..F z- @-: k_4w �'F� ',"- we r' - w` F, . 4 ,i � � �s,�, �.. `• <^' .; I i _ 3 � r:� +� t'i. ya "�]'t ' . 4� r �' 7 � 7 rl" _ _ 'y ` �_ ��. 3 .. J g. ffi` N.ta, Y 'ak.i' ,, t.. . y:.:. ,fit a ! d a w'r L. _ 6 T �F' 7✓- i- •'.i ,.:'.. . �.' .nT K. xJ i 't ti, •: ' • -s s ff c. '.�'' yr A: 1 ' s P• r S , , t1 . - t. •' `Y •. . 4... !.�i' ('1 I. [ .,.Z„ y`. ',is rF i >. 7 ''i` _ s ' . �.. ,� a z # i° r r '�! "'�' 6 C -F 47 s 4 i �, ' i' g .:: 7by' !' < - 4m�. r. - ,.r��.. �t: 1, V-_.,_%._. � ,,�. , ,1�, -, "- - � - . I0-� -,�-I K y ;. 2: t. l }t I- ,C .:fir'' , ,I t +' F .. q■�, r +�' . , A1yf '% . r r _ . S.. Y£ -i F.:. ., : fi' . • .t ......�." �,;� .1 ,.— 14 .. - _�_:z:' .1 . .-, : 1�' — .,.�. ... .I I . .. :...I. ...�., - .1 .. 1, I'., _.,.. I.... . _�,_ %_,.�,�_ _'.....,��;i,.. I . .— , - 11 1. ,�Ll. - 4.. - I,. I,— . . - — - m..., lt)L , . .t . I .. $c .... #_� < <. , 1. 1: : ... � . .:`. 4.$, - . � 0 � "' .. - . - . I _�. I m............. . . . . . . . . . . . . . . ......... t I ....: %.. , : . . I - I r. , . . ... - . . . . . , . 7. . _'.. . . 1. _ , r., r ,':.''i . . .. . .. .... A' .:a „. ,5_ L:x"!.: -,..�:. lam? 3',, s] . 'S e'q�ir' A�� 5, .: A.'•!{,ti' a y'Z 'i'Y 7 w' a�� , .(9 r- ' ., � ,>.' :t Lam . ■ . F' g b• �. $ .. as. M I. �- v f :; k;{ $ fed ;y % � . . . . W_ 0. 7 " I - , �' . �. r. r - -- a s�. r... y ��, , , -- �:`- v. -. __ ") : i it - _ - . -. . i. - '10�- a. A.:. ^ 4< Y - , . el •:/i, n 4- 7. .. - t,iy r r _p.: <.-'�' q I .. " ^f r '%','� yF _� xs .. - ,af '' +z ^ sY., t % .- -,.-. . ; ? � . .. . - . - --, a� , , '.1 It I . . . — . 4 �,� �.��' ,.,.� I, - ;�,+ _.X.... I r, ki- : ,� .,�' x 'EVl, , r; i yIr 'p:7�I . - 'Y e ,r��' I - �• !. d �rdso ' f%"§ '1..Y�,.! Y 4.•-•• ii. YI - . V - g _ f fir. - -} y • '. _ ` .< V .... '"it f I + ,� t Vti. Y Z 'Sy iy ,'. 1' a � r I. . 1 .[! a g. ,] h� a •pw.•' ei a t" _ ' f �. "k " 1`: fy. . ` E.a'�°g ' ,S.rxJ' .y •.xdr 4 . & " +,P_W ` _ a• ar . .a. t za � '` • -'t . 1 r - T I I - . i� J'. .. P .Y '%rt • 'F�yy(p� 7 � ] ¢ 4 . _ 1 .a 'T' s ,Y ��g` �.- • - :K p. .. - ...._ _ t . . rr ,g114 �. / .. --- -� - .y •�[' k .� .7 t' ' -x Wyt �• IK ''� F�� `�r 'off "'ka vY 1. t J b t / n f. a, t 4 1, a % %" g yF: vy,. •"F. . [° e � I �� 1�4 , r L A � '% r �aP I n" l r . 7 Y... w'r' '` kw e . Me 7,A iF 'ma x b p ,, , Y� y�" '{ .. i,F%F r7r ti'' 'y> £. ".��r 5; e.1 i ''lil .!,'.'. LwY ..' Y - .E. '•�. !f!! }. ..1�'.. .t > .t,� M ':, 2. - % . a.'+tir.•= � � T 7'• 1' %5 •�'a fT 'd' a - .., �� ... a ".1- .. e.. �.: .11 . w �" T •:i 3 ',.. , Yx �'�. , „ ;'F• �- ',&. 7 ' ik '. - b•a "� �� '+re, r�s +r x.4-r- y'€o'r;' �, sY,., S� 4. -1 . v .T -•. ./ r '•!' _ e _ T �' 'p'<t!.C"�. eR. - - .t�Y. x a.� ": _ ;S !F r -a- ,t, �i' . • �`.+ye v * • '�' i . i!R •,y�, Sr. e 4'• ,r • ` �'.�, ' ■ ,�' 16�c"t�'• ' { 1r,1f'1.�`.If. .`r •' „� : /.!� } •' } .y '� t-• c . •, "' 'f 'Jr F. k a 2 i"`, . r } yg,�1f�[p,' •- 4' r " - r r ; '? fFfT' y,' Ir•'. t ?* t�•' .ter' e'7 e - .Ee�f. .u' w•i ,y ■ •'F; 7' .. �' C..}• Ii 1.�y.. f r �. a n C : x 's�ZTUI$ a� .1 �.R" r A° � i� - ; re •i� c \ "pw Y, .i $dip l ,. - , _'� .. r Ii i 'i;§' .i ! . ln.., ✓" �' ♦ • R', .� / % , - I \ `S •' J. �a,� t 1 !Q aTG� p L,y ate• x �. % IV ' �y!�� - �'' - Y�<3. �.' fry�}'J$}� �fL E.. '. .�F : irf +d fah.%.. -4f -'i, Y- A�F `:» pp' m % w f . ns": 9�y rf ! t �' $ •-' t. , ` <,,. .%rrid�....,'${.�r ¢ .:7 �'i rb } tie i`','3'Y . I <, ,,, , r-il ,s IN .at d?}k . - . "; 1 Ff.. ,' is % i , ,r 6 • 4 x �z . 1=' K s '. a • _�r r.. .n . A':. nC. ',.,� 3, / �5 d. rY � r e¢ .•i r ,` +1. e l" Pr' ' i'' a '_ ✓ •x "laLY if .% 4�a� . .r.'Y . - ,A*.`— . ... ,r _� ar.4..,a�'i � r. „&, � Y .a �..�� `� ��z� r NOTES: 1. PARCEL DATA FOR THE SITE WAS OBTAINED FROM DUKE ENERGY REAL ESTATE AND IS APPROXI MATE. 2. ASH STORAGE BOUNDARY AND CINDER STORAGE BOUNDARY ARE APPROXIMATE. 3. AS -BUILT MONITORING WELL LOCATIONS PROVIDED BY DUKE ENERGY. 4. SHALLOW MONITORING WELLS (S) - WELL SCREEN INSTALLED ACROSSTHE SURFICIAL WATER TABLE. 5. DEEP MONITORING WELLS (D) - WELL SCREEN INSTALLED IN THE TRANSITION ZONE BETWEEN COMPETENT BEDROCKANDTHE REGOLITH. 6. TOPOGRAPHY DATA FOR THE SITE WAS OBTAINED FROM NC DOT GEOGRAPHIC INFORMATION SYSTEM (GIS)WEBSITE. 7. ORTHOPHOTOGRAPHY WAS OBTAINED FROM WSP (DATEDAPRIL 2014). S. THE COMPLIANCE BOUNDARY IS ESTABLISHED ACCORDING TO THE DEFINITION FOUND IN 15A NCACO2L.0107 (a). SCALE (FEET) 150, 0 /50, S00, /" = 500' ,� �, _',to -�,%� - - .. , -k k .- _p h "o`'% �"W +,, ._k 1. �� O x. ti yam,,. - • - - &,`S 1_�iA , Jl: 'fi t`,. ° v��. wi.-x,4.rir''i,t x•iria,_,.- ' -, ea AREAS TO BE INSPECTED FOR SEEPS DUKE ENERGY CAROLINAS, LLC RIVERBEND STEAM STATION NPDES PERMIT NO. NC0004961 GASTON COUNTY, NORTH CAROD NA LEGEND: DUKE ENERGY PROPERTY BOUNDARY ASH BASIN COMPLIANCE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY COINCIDENT WITH DUKE ENERGY PROPERTY BOUNDARY ASH BASIN WASTE BOUNDARY ASH OR CINDER STORAGE AREA BOUNDARY TOPOGRAPHIC CONTOUR (4 FOOT) ASH BASIN COMPLIANCE GROUNDWATER MONITORING WELL LOCATION AREA TO BE INSPECTED FOR SEEPS STREAM DATE N 9/30/2014 FIGURE 2 A RIVERBEND STEAM STATION ASH BASIN INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES Riverbend Steam Station Ash Basin INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES 1 1. Purpose of Inspection The purpose of the inspection is to identify new discharges and indicators of potential new discharges, including toe drain outfalls, seeps, and weeps that arise after the initial submittal of maps required by North Carolina General Statute 130A‐309.210(a)(2)(ii). Seepage is considered to be the movement of wastewater from the ash basin through the ash basin embankment, the embankment foundation, the embankment abutments, or through residual material in areas adjacent to the ash basin. Therefore, a seep is defined in this document as an expression of seepage at the ground surface. A weep is understood to have the same meaning as a seep. If new discharges or indicators of potential new discharges are identified, the decision flow chart (see Figure A‐1) will be used to determine if the potential new discharge is from the ash basin and if notification to the North Carolina Department of Environment and Natural Resources (NCDENR) Division of Water Resources (DWR) is required. 2. General Inspection Requirements 2.1. Inspections are to be performed on areas that are below the ash basin full pond elevation and within the area shown on Figure A‐2. The purpose of the inspection is to identify new discharges and indicators of potential new discharges, including toe drain outfalls, seeps, and weeps associated with the coal combustion residuals surface impoundment (ash basin). 2.2. If required, a larger scale figure showing the locations of outfalls from engineered channels will be developed. If a separate figure showing outfalls from engineered channels is not developed, Figure A‐2 will be revised to show these features. 2.3. Inspections of areas on or adjacent to the ash basin embankments should be performed within two months after mowing, if possible. 2.4. Inspections should not be performed if the following precipitation amounts have occurred in the respective time period preceding the planned inspection: 2.4.1. Precipitation of 0.1 inches or greater within 72 hours or 2.4.2. Precipitation of 0.5 inches or greater within 96 hours 2.5. Record the most recent ash basin water surface elevation. 2.6. Review previous Inspection for Identification of New Discharge report(s) prior to performing inspection. 2.7. Review the most recent previous dam inspections. 2.8. Conduct an interview with the Site Environmental Coordinator prior to performing inspection to inquire about possible changes to site conditions, such as pond elevations, operations, additions or removal of wastewater discharges to the ash basin, changes to site surface water drainage, etc. Riverbend Steam Station Ash Basin INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES 2 3. Frequency of Inspections Inspections will be performed on a semi‐annual basis during the following months: April to May and October to November. 4. Qualifications The inspections shall be performed under the direction of a qualified Professional Engineer or Professional Geologist. 5. Documentation of Inspection The inspection shall be documented by the individual performing the inspection. The report should contain observations and descriptions of the seeps observed, changes in observations compared to previous inspections, estimates of flows quantities, and photographs of seeps and outfalls of engineered channels designed or improved for collecting water from the impoundment. Photographs are to be numbered and captioned. 6. Initial Inspection An initial inspection should be performed to identify features and document baseline conditions including location, extent (i.e., dimensions of affected area), and flow. Seep locations should be recorded using a Global Positioning System (GPS) device. Photographs should be taken from vantage points that can be replicated during subsequent semi‐annual inspections. 7. Inspection For New Seeps at Outfalls From Engineered Channels Inspect the outfalls from engineered channels designed and/or improved (such as through the placement of rip‐rap) associated with the ash basin dikes to identify new seeps or indicators of new seeps. 7.1. Inspect all outfalls from engineered channels designed and/or improved (such as through the placement of rip‐rap) 7.2. Document the condition of the outfall of the engineered channel with photographs. Photographs are to be taken from similar direction and scale as photographs taken during the initial inspection. 7.3. Observe outfall for seepage and for indicators of seeps. 7.4. Compare current seepage location, extent, and flow to seepage photographs and descriptions from previous inspections. 7.5. Record flow rate if measureable. Riverbend Steam Station Ash Basin INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES 3 9. Inspection For New Seeps Not Captured by Engineered Channels Inspect areas below the ash basin full pond elevation and within the slope‐aquifer system shown on Figure A‐2 to identify new seeps or indicators of new seeps. Inspect topographic drainage features that potentially could contain new seeps that potentially discharge from the ash basin. 9.1. Previously Identified Seeps a) Inspect previously identified seep locations. Document the condition of the seeps with a photograph. Photographs are to be taken from similar direction and at a similar scale as the photograph documenting original photograph of seep. Describe the approximate dimensions and flow conditions of the seep. b) If flow measurement device is installed at the outfall, record flow. c) Observe seep to determine if changes to location, extent, or flows are present. Document changes to location, extent, and/or flow amount or pattern. 9.2. New Seep or Indicators of Seep a) Mark the location of new seep or indicators of seep using a GPS device. b) Document the condition of the seeps or indicators of seeps with a photograph. c) Describe the approximate dimensions and flow conditions of the seep. d) Map the location of new seep or indicator of seep using GPS coordinate points collected during the site visit. e) If seep or indicator of seep was not caused by changes in surface water drainage and if the location is below the ash basin pond elevation, utilize the decision flow chart to determine if the seep represents a discharge from the ash basin and if notification to DWR is required. 10. Update Maps Identifying Seeps If new seeps are identified during the inspection, Figure A‐2 shall be updated to show the location of the new seeps. All seeps located below the ash basin full pond elevation and within the slope‐aquifer system shown are to be shown on Figure A‐2. 11. Decision Flow Chart The decision flow chart developed to determine whether a new seep discharges from the ash basin is found on Figure A‐1. Riverbend Steam Station Ash Basin INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES 4 12. Procedure for Notifying NCDENR DWR If New Discharge Is Confirmed If it is determined that a newly identified seep is present, Duke Energy will notify the DWR Regional Office by mail within 14 days after the determination. Riverbend Steam Station Ash Basin INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES 5 Notes: 1. If no new seeps are identified, inspection will be documented however no notification to NCDENR DWR is required. 2. If new seeps are identified that do not represent discharge from the ash basin during the same inspection that identifies new seeps that do represent a discharge from the ash basin, a single report will be submitted to NCDENR DWR. - . , - -, . . .. . � .,�. ., �. - . I :�( . ., - `;' . � . 1, . r a 3r �'`',rrTF l ', tl- �r '-4: r 'it yr':, r' ..•1 . $ .y� * r �y , , . ir , _,t ,P, :� < . )-: y" :r""+r. l: ss:i,. -d-': �.-_ 1 -;.;. 'ti 3 . >Yk 3`�';:� '•_4s ..�� .'-& ,C" r' .�' y '. 4 . r : "K. % r 9Jr .r, . • 9r _ _ 1` {F p, 3 �R C. i R M': r :d r + 54 _�..t .f r• .. . '. r' . 6 r. �s - 4 i f'� I J ` "r . a r @ r. aI � ! 4 ' `r �a+h s , . �n� ? r' { 7P = t Zr �• i t. N r E r� - :' i 'F 'F S � k - } �• is ' 3 x ': , ,. . . . -(.. _ .. 3 y¢ 7^"rf . i - .r,.e. _ _ __ i . rx x. _ ".!),;��- r, yrJ '. n�. ^�r 1%. . L . . %. . . �-,f . - } '� . ,...5 V . �. a.,l(` .lRy _ i�^.!. % . I f. -I - — ,� ., f - - .. •4 '] ' -... yam. ` !' ..' X n 'yam �•' 9 I� t •' +. 1-1 ' Je■ w , ' -r" �, , . � .-,� r.. .,., . . 41'. 1',� �'. " . ,_ '. .� . , � -,� , « ` + _ . *Wi , xr ' 'l. _ r,r".s S �,' ' , " .,.. r - �r a *- t r k z.[ �,. fir: :. • +,y ,'Y i ,�'' ,• fib' •;'� ;' _ '•'� ..':2 " 1. 8•, .µh`<-l: ��WW •'W''. �. Mi . -.l v'::'tl-.=SF,,s '�I TF _ ;:'i'.:J; — yy :. �` , ;. %, . "- '. a z::. ^ x S 4' � 4 'Tr ' ,' " t : yyam[ d j Jr nA, A, , Y+' 1r, �'1 ' � L'ti ` h' l' Y �. >• 1 y ]r ` r ``n . blp' 'A1 ';r K 'Y'*P• L -d '.. .- ,1�, �•i. 4, -t e+ ,k'>"'_ ...� . ° _ a ,£' ;� , w $".: 'i: '4 s. •}� r u `.. Y ,a r : �� ss.. % r. ., r �' 5° 1ri 4 -�L, * -1 •'r.Je a. '.s'. 4„i �` �R`. �Y 'fir •bxAM' .,, } a , r ` �■R4 '. t - N ti r " yy 1t�.', �. 's. C.. ., d I' p' br ,'.: t M ? - T V .. , r, `;. [ \:%t' . �, 1 ram• _ . . x . 11 ` .•- S. :::; x c :y� 'r�'.I ..r - . r Y o .. E 1 e : _ . ' F' .3 ..3 .Y'n .J ! j ii� ti tI. W'' r. r' '�e �;]j{ 4 p1Y A r. y. .'.. :m �" xil - t �'' ,,� 'F" i# t a' T .,K A'.. }� ..+Y• ` '. ..f } 2 - r A P r 1 Lx F c ;�' 9..,T �✓ '.1 f. b' w . ,. - .�. r of .: . d ~ ..4 ,� T S ,� ] ^ham ' �� r>;: y L C c i '.[ .. 4' i •• 9.'. Y . (�y� �. " Y' TS. A' S •�S'r x a` t: d ` ` �. �4 i �. > �" r,rt. } 4 '�y . s 'i _ 1 : F. F 7 t �� ". �$, yr i '-• .^.' ' 'ip .IMF. * - .P L, !. y{..F z- @-: k_4w �'F� ',"- we r' - w` F, . 4 ,i � � �s,�, �.. `• <^' .; I i _ 3 � r:� +� t'i. ya "�]'t ' . 4� r �' 7 � 7 rl" _ _ 'y ` �_ ��. 3 .. J g. ffi` N.ta, Y 'ak.i' ,, t.. . y:.:. ,fit a ! d a w'r L. _ 6 T �F' 7✓- i- •'.i ,.:'.. . �.' .nT K. xJ i 't ti, •: ' • -s s ff c. '.�'' yr A: 1 ' s P• r S , , t1 . - t. •' `Y •. . 4... !.�i' ('1 I. [ .,.Z„ y`. ',is rF i >. 7 ''i` _ s ' . �.. ,� a z # i° r r '�! "'�' 6 C -F 47 s 4 i �, ' i' g .:: 7by' !' < -01" K y ;. 2: t. lIlk }11. t " . R. ,C .:fir'' , . Q t +' F .. q■�, r %+�' . , A�yf '% . r r _ . S.. Y£ -i F.:. ., : fi' I I. . • .t ......�." �,;� .1 ,.— 14 .. - _�_:z:' .1 . .-, : 1�' — .,.�. ... .I I . .. :...I. ...�., - .1 .. 1, I'., _.,.. I.... . _�,_ %_,.�,�_ _'.....,��;i,.. I . .— , - 11 1. ,�Ll. - 4.. - I,. I,— . . - — - m..., lt)L , . .t . I .. $c .... #_� < <. , 1. 1: : ... � . .:`. 4.$, - . � 0 � "' .. - . - . I _�. I m............. . . . . . . . . . . . . . . ......... t I ....: %.. , : . . I - I r. , . . ... - . . . . . , . 7. . _'.. . . 1. _ , r., r ,':.''i . . .. . .. .... A' .:a „. ,5_ L:x"!.: -,..�:. lam? 3',, s] . 'S e'q�ir' A�� 5, .: A.'•!{,ti' a y'Z 'i'Y 7 w' a�� , .(9 r- ' ., � ,>.' :t Lam . ■ . F' g b• �. $ .. as. M I. �- v f :; k;{ $ fed ;y % � . . . . W_ 0. 7 " I - , �' . �. r. r - -- a s�. r... y ��, , , -- �:`- v. -. __ ") : i it - _ - . -. . i. - '10�- a. A.:. ^ 4< Y - , . el •:/i, n 4- 7. .. - t,iy r r _p.: <.-'�' q I .. " ^f r '%','� yF _� xs .. - ,af '' +z ^ sY., t % .- -,.-. . ; ? � . .. . - . - --, a� , , '.1 It I . . . — . 4 �,� �.��' ,.,.� I, - ;�,+ _.X.... I r, ki- : ,� .,�' x 'EVl, , r; i yIr 'p:7�I . - 'Y e ,r��' I - �• !. d �rdso ' f%"§ '1..Y�,.! Y 4.•-•• ii. YI - . V - g _ f fir. - -} y • '. _ ` .< V .... '"it f I + ,� t Vti. Y Z 'Sy iy ,'. 1' a � r I. . 1 .[! a g. ,] h� a •pw.•' ei a t" _ ' f �. "k " 1`: fy. . ` E.a'�°g ' ,S.rxJ' .y •.xdr 4 . & " +,P_W ` _ a• ar . .a. t za � '` • -'t . 1 r - T I I - . i� J'. .. P .Y '%rt • 'F�yy(p� 7 � ] ¢ 4 . _ 1 .a 'T' s ,Y ��g` �.- • - :K p. .. - ...._ _ t . . rr ,g114 �. / .. --- -� - .y •�[' k .� .7 t' ' -x Wyt �• IK ''� F�� `�r 'off "'ka vY 1. t J b t / n f. a, t 4 1, a % %" g yF: vy,. •"F. . [° e � I �� 1�4 , r L A � '% r �aP I n" l r . 7 Y... w'r' '` kw e . Me 7,A iF 'ma x b p ,, , Y� y�" '{ .. i,F%F r7r ti'' 'y> £. ".��r 5; e.1 i ''lil .!,'.'. LwY ..' Y - .E. '•�. !f!! }. ..1�'.. .t > .t,� M ':, 2. — % . a.'+tir.•= � � T 7'• 1' %5 •�'a fT 'd' a — .., �� ... a ".1- .. e.. �.: .11 . w �" T •:i 3 ',.. , Yx �'�. , „ ;'F• �- ',&. 7 ' ik '. - b•a "� �� '+re, r�s +r x.4-r- y'€o'r;' �, sY,., S� 4. -1 . v .T -•. ./ r '•!' _ e _ T �' 'p'<t!.C"�. eR. - - .t�Y. x a.� ": _ ;S !F r -a- ,t, �i' . • �`.+ye v * • '�' i . i!R •,y�, Sr. e 4'• ,r • ` �'.�, ' ■ ,�' 16�c"t�'• ' { 1r,1f'1.�`.If. .`r •' „� : /.!� } •' } .y '� t-• c . •, "' 'f 'Jr F. k a 2 i"`, . r } yg,�1f�[p,' •- 4' r " - r r ; '? fFfT' y,' Ir•'. t ?* t�•' .ter' e'7 e - .Ee�f. .u' w•i ,y ■ •'F; 7' .. �' C..}• Ii 1.�y.. f r �. a n C : x 's�ZTUI$ a� .1 �.R" r A° � i� - ; re •i� c \ "pw Y, .i $dip l ,. - , _'� .. r Ii i 'i;§' .i ! . ln.., ✓" �' ♦ • R', .� / % , - I \ `S •' J. �a,� t 1 !Q aTG� p L,y ate• x �. % IV ' �y!�� - �'' - Y�<3. �.' fry�}'J$}� �fL E.. '. .�F : irf +d fah.%.. -4f -'i, Y- A�F `:» pp' m % w f . ns": 9�y rf ! t �' $ •-' t. , ` <,,. .%rrid�....,'${.�r ¢ .:7 �'i rb } tie i`','3'Y . I <, ,,, , r-il ,s IN .at d?}k . - . "; 1 Ff.. ,' is % i , ,r 6 • 4 x �z . 1=' K s '. a • _�r r.. .n . A':. nC. ',.,� 3, / �5 d. rY � r e¢ .•i r ,` +1. e l" Pr' ' i'' a '_ ✓ •x "laLY if .% 4�a� . .r.'Y . - ,A*.`— . ... ,r _� ar.4..,a�'i � r. „&, � Y .a �..�� `� ��z� r NOTES: 1. PARCEL DATA FOR THE SITE WAS OBTAINED FROM DUKE ENERGY REAL ESTATE AND IS APPROXI MATE. 2. ASH STORAGE BOUNDARY AND CINDER STORAGE BOUNDARY ARE APPROXIMATE. 3. AS -BUILT MONITORING WELL LOCATIONS PROVIDED BY DUKE ENERGY. 4. SHALLOW MONITORING WELLS (S) - WELL SCREEN INSTALLED ACROSSTHE SURFICIAL WATER TABLE. 5. DEEP MONITORING WELLS (D) - WELL SCREEN INSTALLED IN THE TRANSITION ZONE BETWEEN COMPETENT BEDROCKANDTHE REGOLITH. 6. TOPOGRAPHY DATA FOR THE SITE WAS OBTAINED FROM NC DOT GEOGRAPHIC INFORMATION SYSTEM (GIS)WEBSITE. 7. ORTHOPHOTOGRAPHY WAS OBTAINED FROM WSP (DATEDAPRIL 2014). S. THE COMPLIANCE BOUNDARY IS ESTABLISHED ACCORDING TO THE DEFINITION FOUND IN 15A NCACO2L.0107 (a). SCALE (FEET) 150, 0 /50, S00, /" = 500' ,� �, _',to -�,%� - - .. , -k k .- _p h "o`'% �"W +,, ._k 1. �� O x. ti yam,,. - • - - &,`S 1_�iA , Jl: 'fi t`,. ° v��. wi.-x,4.rir''i,t x•iria,_,.- ' -, ea AREAS TO BE INSPECTED FOR SEEPS DUKE ENERGY CAROLINAS, LLC RIVERBEND STEAM STATION NPDES PERMIT NO. NC0004961 GASTON COUNTY, NORTH CAROD NA LEGEND: DUKE ENERGY PROPERTY BOUNDARY ASH BASIN COMPLIANCE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY COINCIDENT WITH DUKE ENERGY PROPERTY BOUNDARY ASH BASIN WASTE BOUNDARY ASH OR CINDER STORAGE AREA BOUNDARY TOPOGRAPHIC CONTOUR (4 FOOT) ASH BASIN COMPLIANCE GROUNDWATER MONITORING WELL LOCATION AREA TO BE INSPECTED FOR SEEPS STREAM DATE N 9/30/2014 FIGURE A 2