129 



Rc\ien of The U.S. Ein'ironmenial Pioieciioii AgeiiCN^'s Biological Assessmeni: 



Assessment of Potential Impact of the MW'RA 

 Outfall on Endangered Species 



Revie\\ ed by: 



Craig D. Ta\lor 



Associate Scicntisl 



Woods Hole Oceanographic Iiistitiition 



20 June 1993 



111 v.iy opinion the biological assessment submitted by the En\ironniental Protection 

 AgencA- (EPA) is a thorough and convincing document indicating, relati\e to the present 

 outfall in Boston Harbor, that the proposed MAVPv.^ outfall in Massachusetts Bay is not likely 

 to ha\-e an effect on chosen endangered species or the food chain that supports them. 

 Working in fa\or of the outer discharge sire are a) a more fa\'orable effluent dispersion 

 because of input into deeper A%'aters \\a better designed diffusers. b) modest tidal cun"enis that 

 foster local spreading of the eftluent ^^"ithout large directed floA\'s thai \\ould te;id to rapidh 

 iranspon imdisbursed plumes great distances, and c) re!aii\el\ high and \ariable background 

 le\els of nutrients and foreign substances in the receiving ^^■aters that make enriclmient and. 

 hence, potential impact upon the system undetectable after modest dilution of the eftluent. 



W'lih respect to nutrients, the abo\ e conclusions ha^■e been backed in part by use of 

 phN'sical modeling (Blumberg-Mellor model) to establish the dilution field of both the present 

 and proposed discharge sites in order to estimate the aerial magnittide of nutrient enrichment 

 and possible effects Upon primar>' production, on the premise that the maiorin of nitrogen 

 introduced into Boston Harbor \-i3 the present ounall is tuished into Massachusens Ba\'. and 

 similar loading to the outer site \\ould. hence, be experienced. It is m\- understanding from 

 discussions with colleagues that this model is quite good for the purposes intended. It is still 

 m some state of development ^^itll respect to modeling summer-straiified conditions and 

 modeling some of the tlner details, but the preparers of the assessment assen that the overall 

 conclusions ^^■ill not be aflected b\- further refinements of the model. Gi\en the dramatic 

 impro">emenT in the predicted eftluent diluiion at the outer site 1 \\-ould tend to acree. First. I 

 agree that input of nutrients to the outer site \\ill iikeh" be similar to that presenth' input from 

 Boston Harbor as a mechanism of nitrogen removal, denitrificaiion. -\\]\] be a reiati\-eh minor 

 pla\er (buna! in sediments is probabh of similar magninide). Denitrificaiion predominanth- 



