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HomeMy WebLinkAbout1812_Duke_Marshall_ConstModRequest_DIN26904_20161025526 South Church Street: Mail Code EC13K Charlotte, North Carolina 28202 980-373-5697 October 24, 2016 North Carolina Department of Environmental Quality Division of Waste Management Solid Waste Section 2090 U.S. Highway 70 Swannanoa, North Carolina 28778 Attn: Mr. Larry Frost Re: Industrial Landfill No.1 Cells 3 and 4 Construction Modification Request Permit No.: 1812-INDUS Marshall Steam Station Catawba County Terrell, North Carolina 28682 Dear Mr. Frost, As discussed via phone conversation on October 19, 2016, Duke Energy requests approval for the listed modifications found in the attached letter titled Cell 3 and Cell 4 Construction Plan for Marshall Steam Station’s Industrial Landfill No. 1 (Permit No. 1812-INDUS). An erosion and sediment control plan will be submitted to the Division of Land Quality for approval prior to beginning any land disturbing activities. If there are any questions regarding this request, please contact me at (980) 373-5697. Respectfully Submitted, Tyler Hardin Environmental Services Cc (via e-mail): Ed Mussler, NCDEQ Kyle Baucom, Duke Energy Dan Zakary, Duke Energy Jeff Jones, Duke Energy EX 10/18/2016 Duke Energy – CCP Engineering 400 South Tryon Street Mail Code ST06A Charlotte, NC 28202 Attention: Kyle Baucom, P.E. Tyler Hardin Reference: Cells 3 and Cell 4 Construction Plan Marshall Steam Station Industrial Landfill #1 Permit No: 1812-INDUS 8320 East NC 150 Highway Catawba County, Terrell, North Carolina S&ME Project No. 7235-16-004 Dear Mr. Baucom and Ms. Hardin: The purpose of this letter is to summarize the major differences between the Construction Plans and the Engineering Plans in the Permit to Construct (PTC) Application documents. The major differences are as follows: 1) The bottom elevation of Cell 3 Sump was raised approximately 0.5 feet above the permitted bottom elevation. This was done to meet the minimum post settlement separation requirement of 5 feet above the high groundwater table as required by the EPA's Coal Combustion Residuals (CCR) Rule. The footprint of the sump was modified due to this elevation change and reconfiguration of the side slope risers (see No. 2). The sump capacity as previously permitted was also maintained as a result of these required changes. However, these changes did not impact the subgrade elevations outside of the sump area. 2) The location of the Cell 3 side slope risers were shifted about 10 feet to the northeast, and the southeast side of Cell 3 sump was moved further to the southeast to widen the sump area. This was done to allow for the side slope risers to extend straight into the sump rather than bend 90 degrees as shown on the permit plans to allow for a smoother transition for leachate pump access. 3) A temporary stockpile is proposed to be located adjacent to the south side of Cell 2 for excess soil removed from the construction area (see Figure 1). The general location is the similar to the PTC Application. However, the footprint and proposed grading have been modified. 4) Based on the PTC Application, approximately 3,900 feet of force main piping was proposed to be installed to discharge leachate into the ash basin in the vicinity of the existing Cells 1 and 2 leachate discharge location. However, Duke Energy has another project to design and construct an on-site retention basin for handling and treatment of process water flows. Current plans are to develop additional bid documents to temporarily discharge to the ash basin as a location in closer proximity to the proposed Cells 3 and 4 with a future permanent tie-in to the proposed on-site retention basin at a later date. 5) Five (5) chimney drains (as shown on Figure 1) have been added with the construction of Cells 3 and 4. 6) A temporary sediment basin (see Figure 1) is proposed to be located to the south of Cell 4, for stormwater runoff. 7) The size of the side slope risers were increased from 18 inches to 24 inches in diameter to better accommodate leachate pumps. 8) The geotextile weight was increased from 8 oz./sq. yd. to 10 oz./sq. yd. . 9) Testing is being conducted with site specific leachate to evaluate its compatibility with various Geosynthetic Clay Liners (GCL) to evaluate the long-term hydraulic conductivity against the specification requirements. If you have any questions, do not hesitate to contact this office Sincerely, S&ME, Inc. Stephen J Loskota, P.E. Sharon Korleski, P.E. Civil Group Leader Senior Engineer N.C. Registration No. 33606 N.C. 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T I T L E A R C H E 1 F I L E N A M E : 3 0 . 0 " x 4 2 . 0 " D W G T Y P E : J O B N O : D A T E : S C A L E : D E S : D F T R : C H K D : E N G R : A P P D : A S S H O W N D W G 7 2 3 5 - 1 6 - 0 0 4 1 0 / 1 0 / 2 0 1 6 W R H S J L S Y K S J L W R H I S S U E D F O R B I D 0 0 0 C O A S E A L C O N S T R U C T I O N P L A N M A R S H A L L S T E A M S T A T I O N T E R R E L L , N O R T H C A R O L I N A 9 7 5 1 S O U T H E R N P I N E B L V D C H A R L O T T E , N C 2 8 2 7 3 ( 7 0 4 ) - 5 2 3 - 4 7 2 6 E N G I N E E R I N G F I R M L I C E N S E N U M B E R : F - 0 1 7 6 0 7 2 3 5 - 1 6 - 0 0 4 1 0 - 1 0 - 1 6 D E S C : L A N D F I L L R E V J O B N O D A T E P R O J E C T T Y P E C H K D E N G R A P P D D E S D F T R C E L L 3 & C E L L 4 S H E E T N O . M A R _ C 9 0 7 . 0 0 2 . M A R _ C 9 0 7 . 0 0 2 . M A R _ C 9 0 7 . 0 0 2 . N C D E Q P e r m i t t o B i d C h a n g e F i g u r e . d w g P E R M I T T O B I D C H A N G E S R E F E R E N C E : S U R V E Y I N F O R M A T I O N P R O V I D E D B Y W S P G R O U P F R O M A E R I A L L I D A R D A T E D J U N E 2 3 , 2 0 1 6 . H O R I Z O N T A L C O N T R O L S U R V E Y S B A S E D O N N O R T H C A R O L I N A S T A T E P L A N E N A D 8 3 . V E R T I C A L C O N T R O L S U R V E Y S B A S E D O N N A V D 8 8 . A L L A R E A S O F D A S H E D C O N T O U R S M A Y N O T M E E T N A T I O N A L M A P A C C U R A C Y S T A N D A R D S A N D S H O U L D B E F I E L D V E R I F I E D . 0 1 0 0 2 0 0 3 0 0 ( I N F E E T ) G R A P H I C S C A L E 1 " = 1 0 0 ' L E G E N D 5 3 0 5 3 0 L L L C S L D S 3 H : 1 V C D - 1 F I G U R E 1 O H E 8 5 9 . 7 X X X X X X X X M - 4 5 L O D SEE NOTES1 & 2 S E E N O T E 3 S E E N O T E 6 S E E N O T E 5 SEE NOTE 7 N O T E S : 1 . T h e b o t t o m e l e v a t i o n o f C e l l 3 S u m p w a s r a i s e d a p p r o x i m a t e l y 0 . 5 f e e t a b o v e t h e p e r m i t t e d b o t t o m e l e v a t i o n . T h i s w a s d o n e t o m e e t t h e m i n i m u m p o s t s e t t l e m e n t s e p a r a t i o n r e q u i r e m e n t o f 5 f e e t a b o v e t h e h i g h g r o u n d w a t e r t a b l e a s r e q u i r e d b y t h e E P A ' s C o a l C o m b u s t i o n R e s i d u a l s ( C C R ) R u l e . T h e f o o t p r i n t o f t h e s u m p w a s m o d i f i e d d u e t o t h i s e l e v a t i o n c h a n g e a n d r e c o n f i g u r a t i o n o f t h e s i d e s l o p e r i s e r s ( s e e N o . 2 ) . T h e s u m p c a p a c i t y a s p r e v i o u s l y p e r m i t t e d w a s a l s o m a i n t a i n e d a s a r e s u l t o f t h e s e r e q u i r e d c h a n g e s . H o w e v e r , t h e s e c h a n g e s d i d n o t i m p a c t t h e s u b g r a d e e l e v a t i o n s o u t s i d e o f t h e s u m p a r e a . 2 . T h e l o c a t i o n o f t h e C e l l 3 s i d e s l o p e r i s e r s w e r e s h i f t e d a b o u t 1 0 f e e t t o t h e n o r t h e a s t , a n d t h e s o u t h e a s t s i d e o f C e l l 3 s u m p w a s m o v e d f u r t h e r t o t h e s o u t h e a s t t o w i d e n t h e s u m p a r e a . T h i s w a s d o n e t o a l l o w f o r t h e s i d e s l o p e r i s e r s t o e x t e n d s t r a i g h t i n t o t h e s u m p r a t h e r t h a n b e n d 9 0 d e g r e e s a s s h o w n o n t h e p e r m i t p l a n s t o a l l o w f o r a s m o o t h e r t r a n s i t i o n f o r l e a c h a t e p u m p a c c e s s . 3 . A t e m p o r a r y s t o c k p i l e i s p r o p o s e d t o b e l o c a t e d a d j a c e n t t o t h e s o u t h s i d e o f C e l l 2 f o r e x c e s s s o i l r e m o v e d f r o m t h e c o n s t r u c t i o n a r e a ( s e e F i g u r e 1 ) . T h e g e n e r a l l o c a t i o n i s t h e s i m i l a r t o t h e P T C A p p l i c a t i o n . H o w e v e r , t h e f o o t p r i n t a n d p r o p o s e d g r a d i n g h a v e b e e n m o d i f i e d . 4 . B a s e d o n t h e P T C A p p l i c a t i o n , a p p r o x i m a t e l y 3 , 9 0 0 f e e t o f f o r c e m a i n p i p i n g w a s p r o p o s e d t o b e i n s t a l l e d t o d i s c h a r g e l e a c h a t e i n t o t h e a s h b a s i n i n t h e v i c i n i t y o f t h e e x i s t i n g C e l l s 1 a n d 2 l e a c h a t e d i s c h a r g e l o c a t i o n . H o w e v e r , D u k e E n e r g y h a s a n o t h e r p r o j e c t t o d e s i g n a n d c o n s t r u c t a n o n - s i t e r e t e n t i o n b a s i n f o r h a n d l i n g a n d t r e a t m e n t o f p r o c e s s w a t e r f l o w s . C u r r e n t p l a n s a r e t o d e v e l o p a d d i t i o n a l b i d d o c u m e n t s t o t e m p o r a r i l y d i s c h a r g e t o t h e a s h b a s i n a s a l o c a t i o n i n c l o s e r p r o x i m i t y t o t h e p r o p o s e d C e l l s 3 a n d 4 w i t h a f u t u r e p e r m a n e n t t i e - i n t o t h e p r o p o s e d o n - s i t e r e t e n t i o n b a s i n a t a l a t e r d a t e . 5 . F i v e ( 5 ) c h i m n e y d r a i n s ( a s s h o w n o n F i g u r e 1 ) h a v e b e e n a d d e d w i t h t h e c o n s t r u c t i o n o f C e l l s 3 a n d 4 . 6 . A t e m p o r a r y s e d i m e n t b a s i n ( s e e F i g u r e 1 ) i s p r o p o s e d t o b e l o c a t e d t o t h e s o u t h o f C e l l 4 , f o r s t o r m w a t e r r u n o f f . 7 . T h e s i z e o f t h e s i d e s l o p e r i s e r s w e r e i n c r e a s e d f r o m 1 8 i n c h e s t o 2 4 i n c h e s i n d i a m e t e r t o b e t t e r a c c o m m o d a t e l e a c h a t e p u m p s .