ABSTRACT
A b s t r a c t The C a r s i n g t o n a q u e d u c t c o n s i s t s o f a s e r i e s o f p i p e l i n e s and t u n n e l s c o n s t r u c t e d i n t h e e a r l y 1 9 8 0 ' s . The a r e a h a s a h i s t o r y o f m i n i n g a c t i v i t e s d a t i n g b a c k t o t h e Romans. E a r l y m i n i n g r e c o r d s r e p o r t e d t h e o c c u r r e n c e o f f i r e d a m p g a s . Methane was d e t e c t e d d u r i n g c o n s t r u c t i o n o f t h e C a r s i n g t o n t u n n e l s , on one o c c a s i o n r e a c h i n g 100% o f L E L . S u r v e y s showed methane t o be p r e s e n t above t h e crown o f a s u b s t a n t i a l l e n g t h o f t u n n e l . When t h e a q u e d u c t was d e w a t e r e d and v e n t i l a t e d n a t u r a l l y , t h e f o r m a t i o n o f a b i o f i l m was o b s e r v e d i n s e c t i o n s o f t h e t u n n e l where methane had been d e t e c t e d . The b i o f i l m d e v e l o p e d a r o u n d p o i n t s o f w a t e r i n g r e s s . I t c o n s i s t e d o f a p i n k s u r f a c e l a y e r c o a t i n g a b l a c k / w h i t e f i b r o u s m a t e r i a l s e v e r a l cm t h i c k . B u b b l e s o f g a s t r a p p e d i n t h e b i o f i l m c o n t a i n e d 27% methane; i n g r e s s w a t e r was i n d e n t i f i e d a s t h e p r i n c i p a l r o u t e by w h i c h methane was e n t e r i n g t h e t u n n e l . M e t h a n e - o x i d i s i n g b a c t e r i a were i n d e n t i f i e d i n i n g r e s s w a t e r and t h e b i o f i l m t o g e t h e r w i t h a r a n g e o f h e t e r o t r o p h i c m i c r o o r g a n i s m s . B a c t e r i a u s i n g methane f o r g r o w t h may r e p r e s e n t t h e f i r s t l i n k i n t h e food c h a i n , w i t h o t h e r m i c r o o r g a n i s m s g r o w i n g a t t h e i r e x p e n s e . P r o l i f i c g r o w th o f b i o f i l m i n t u n n e l s may c a u s e l o c a l d e p l e t i o n o f oxygen, e n r i c h m e n t o f c a r b o n d i o x i d e and s l i p p e r y , h a z a r d o u s c o n d i t i o n s f o r w o r k e r s . Keywords: B i o f i l m , Methane, Aqueduct, T u n n e l , M e t h a n e - o x i d i s i n g b a c t e r i a .
