Halifax Harbour Cleanup Inc. - Halifax Regional Municipality

Issues 37
25. The Panel recommends that HHCI
reexamine the Project as It applies to Malnland
South and Herring Cove, in the context
of a new Detailed Area Plan for Mainland
South. The development of the Detailed Area
Plan should be immediately initiated by the
City of Halifax through consultation with the
community and HHCI, In order to resolve future
growth projections, servicing, transportatlon,
land use and environmental Issues for
Mainland South and the Backlands.
28. The Panel recommends that the County of
Halifax, Herring Cove residents and HHCI cooperatively
determine the preferred solution
for sewage collection and treatment for the
Herring Cove area, given the low-growth provisions
of the District 5 Municipal Planning
Strategy and desires of the community.
Because raw sewage will continue to be discharged into
Watleys Cove until 1998 or later, and given the impacts on
community life and the environment under the Mainland
South-Herring Cove project as proposed, the Panel feels it is
highly desirable to implement a temporary mitigation
measure.
27. The Panel recommends that HHCI ensure
that discharges at Watleys Cove immediately
receive preliminary treatment. This Interim
solution should be developed under a
time-limited site agreement between HHCI
and the Herring Cove community. This lnterim
measure is to be used only until the
regional system, or an alternative treatment
facility for Mainland South-Herring Cove, is
in place. Likewise, HHCI should examine the
operation of the existing CSO at Roachs
Pond and arrange for Interim mitigation measures.
These mitigation measures should be
installed by HHCI or the appropriate
authority.
4.7.2 Alternative Treatment Technologies
Several participants suggested that alternative sewage-treatment
technologies to those proposed for various
parts of the Project could prove to be less expensive on the
basis of life-cycle costs and which in some cases could provide
a better level of treatment.
One participant suggested using only screens and dynamic
storm separators in conjunction with ultraviolet light treatment
at CSOs, as a preferred alternative to a regional primary treatment
plant. An interest group submitted an extensive report
on alternative sites and treatment technologies. Included were
suggestions to consider rotating biological contactors or solar
aquatics for Halifax Mainland South; a cyclic activated sludge
system (sequencing batch reactor) for the Dartmouth area;
and a multi-story treatment facility for an STP to be located in
pari of the Naval Dockyard parking area in Halifax. These
three technologies would all provide at least secondary level
treatment.
The proposal that an engineered wetland be considered for
the Mainland South area attracted the most interest. After
being collected and conveyed to the proposed site, the wastewater
would be pretreated by screening and grit removal
before being discharged into the designated wetland area. A
number of participants argued that engineered wetlands are a
viable alternative for the Mainland South area, especially
when compared to HHCl’s cost-intensive proposal to install a
deep collection tunnel to transport small volumes of sewage to
the regional STP/OFS facility. Participants proposed that engineered
wetlands would provide a better level of treatment
and offer greater environmental protection at a much lower
cost. Specifically, the wetlands alternative
• +pports the principle of sustainable development; it is an
environmentally responsible means of dealing with sewage
• can be scaled up and expanded without major
consequences
• has substantially higher rates of removal for solids, toxics,
metals and nutrients relative to primary treatment
• removes more than 99% of pathogens in effluent without
disinfection
The Panel also heard a wide range of concerns, from both
HHCI and the public, relative to engineered wetlands in general,
and in the context of its application to Mainland South
specifically. These included concerns about the
• potential accumulation of toxic substances in the biomass .
and sediments of the wetlands
• unknown fate of contaminants in the biomass harvested
from the wetlands
• extent of required land area to achieve’desired result, which
may be substantially greater than anticipated by the review
participants
• ability of the proposed wetlands to function during the cold
and wet seasons
• possibility of contaminating groundwater; given the fractured
granitic geology of the proposed site, an impervious
clay seal would likely have to be installed under the wetland
• suitability of the terrain, which is undulating with large areas
of exposed bedrock
• odour
• ultimate fate and effects of effluent discharged into Mclntosh
Run or to other environments
• local hydrology, particularly the assimilative capacity of Mc-
Intosh Run and the fact that treated sewage effluent might
become the predominant flow in the Run throughout the
year