Background on Case Studies - Environmental Impact Analysis: Process and Methods - page 368

with the anticipated neighborhood impacts and costs supported the Corps'
concern over implementing an intense solids management operation. However
the U.S. EPA prevailed and the Washington Aqueduct launched a program to
manage the residual solids from their water treatment operations in compli-
ance with the new NPDES permit restricting discharge to the Potomac River.
The Washington Aqueduct's action was subject to NEPA because they were a
federal agency and there was potential impact to the human environment, pri-
marily to traffic and aesthetics in the adjacent neighborhoods. Thus an EIS was
initiated with the primary purpose and need to comply with the NPDES permit
requirements. The purpose and need statement was expanded to support alter-
native development and selection to specify a solids management system which:
r Would not impact current or future production of safe drinking
water reliably supplied to the Washington Aqueduct customers
r Would minimize, if possible, impacts on the neighborhoods and
other stakeholders
r Would be cost-effective in design, implementation, and operation
This illustrates one of the interactions of environmental analysis and per-
mitting as discussed in Section 9.2. The necessity for environmental analysis
was driven by the need to meet an environmental permit condition and then
permit requirements were incorporated into the purpose and need as well as
the comparison of alternatives.
The EIS proceeded in line with the steps and procedures outlined in this
topic. Following the initial scoping, the engineering and environmental anal-
ysis team proceeded to develop, screen, and then analyze alternatives. Twenty
six alternatives were identified and then screened. The screening resulted in a
reasonable range of alternatives with the alternatives that managed the solids
off-site being initially eliminated from detailed evaluation for a variety of
reasons, including:
r Construction of a pipeline to transport the solids slurry would
adversely affect properties on the National Register of Historic
Places (like the Washington Monument).
r The low clearance of bridges across the Potomac River prevented
barge transport of solids slurry offsite.
r Using the sanitary sewerage system to transport solids to the waste-
water treatment plant for processing would exceed the system's
capacity, resulting in sewage overflow to surface waters.
The alternatives screening resulted in a list of alternatives that met the
purpose and need, and although they resulted in some impacts, the environ-
mental analysis team felt they could be successfully mitigated.