Halifax Harbour Cleanup Inc. - Halifax Regional Municipality

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38 Issues • limited opportunities to compensate for loss of fish habitat in McIntosh Run, should the wetlands fail • acceptability to area residents Several participants indicated that although engineered wetlands can be effective and work in certain climates, more hydrological, environmental and design information is required before an engineered wetland should be seriously considered as an option. Any proposal for an engineered wetland should be stringently assessed, and should inVolve input from area residents. The Panel is supportive of the engineered wetlands approach as a good sustainable development option for dealing with sewage treatment and disposal in many situations, but has serious reservations about its appropriateness for Mainland South and Herring Cove. Many of the Panel’s reservations parallel those documented above. Solutions that involve discharge to McIntosh Run must be preceded by detailed study of predicted impacts of the effluent on fisheries and freshwater and marine environments, including remediation measures. Any proposed alternative treatment solutions have .to recognize the need for appropriate sludge management. 28. The Panel recommends that, in the context of preparing a new Detailed Area Plan for Mainland South and in seeking alternative soiutions for sewage treatment and disposal for the area, both conventional and alternative approaches be explored. These should include advanced primary or secondary treatments with direct discharge to the ocean, tertiary or equivalent level effluent discharge Into McIntosh Run, and technologies such as englneered wetlands, rotatlng biological contactors and others. Any proposal for englneered wetlands should be seriously examined In light of the stated concerns relating to performance and environmental impacts, and should Include a detailed cost-benefit analysis. 4.8 SEWAGE TREATMENT AND SLUDGE MANAGEMENT FACILITIES 4.8.1 Introduction According to HHCl’s proposal, the sewage that is intercepted and consolidated by the collection system will be transported to a single regional STP/OFS facility which will provide primary treatment and disinfection of the effluent on an artificial island to be constructed at Ives Cove. A diffuser will then discharge the effluent into the Harbour to the west of McNabs Island. The plant will be located on a 9.5-hectare artificial island, “Ives Island,” off the northern end of McNabs Island. The island will require expansion if secondary treatment is to be provided (Figure 9). Fill will be used to create the island. Sources of fill to construct the island were undetermined at the time of the hearings; suggestions included local quarries, the quarry at the Strait of Canso and tunnel spoils. To mitigate concern over siltation entering the marine environment during construction, HHCI has proposed the use of silt curtains to c&fine the sediment plume to the construction site. The site’s main pumping station will lift sewage from the deep-tunnel collection system into the plant. The sewage will then undergo preliminary treatment, consisting of screening, grit removal, and scum and grease removal. Screenings and grit will be barged and trucked away for disposal. Grease and scum will be pumped to the OFS facility. The sewage itself flows through preliminary treatment to the primary clarifiers. Primary clarifiers will remove about 50% of the suspended solids at peak flow and about 85% at average dry weather flow. The plate clarifier system, which was chosen over a conventional clarifier system, comprises a series of individual clarifying chambers operating in pairs. The clarifier plates are inclined and operate at a higher rate of flow than conventional clarifiers, thus allowing a reduction in the size of the tanks and residence time of the sewage. They also reduce space requirements over conventional clarifiers by about 50%. Because plate clarifiers are a relatively new technology, some concern has been expressed that they may prove to be less reliable or cost-effective than conventional clarifiers. The sludge that accumulates in the clarifiers will be moved to the OFS facility for processing. Following primary treatment the wastewater will undergo disinfection by chlorination in a chlorine contact chamber. The effluent will be discharged into the Harbour via a tunnel to the diffuser. To avoid problems with transporting chlorine in either its liquid or gaseous form to the island, chlorine will be generated as sodium hypochlorite from sea water. All solid wastes generated on-site are expected to be transported off, island and disposed of or recycled at approved municipal facilities: land fill, incinerator or recycling depots. Solid wastes from the facilities will consist primarily of screenings and grit, ash from the OFS process, and solid waste generated from administration offices. HHCI has stated that solid-waste disposal must conform to applicable regulations and permitting processes, and the Panel concludes that the provisions set out for solid waste disposal by HHCI are sufficient.
Issues 99 Some of the major issues surrounding the proposed STP/OFS facility relate to its island location, and these have been discussed in Section 4.2, Choosing the Site. Generally, an offshore facility involves greater costs associated with construction, servicing and transportation, and a greater visibility profile from points around the. Harbour, and from McNabs Island. Other issues focusing on treatment level and method, the OFS technology, atid social and environmental impacts are discussed in the following sections. Particular concerns about the impact of the proposed facilities on McNabs Island’s designated parkland is discussed in Section 4.8.9. Ftitur8 Expansion Figure 9 Ives Island Sewage Treatment Plant and Oil-from-Sludge Facility Source: After Halifax Harbour Cleanup Inc.
Page 1 and 2: Halifax Harbour Cleanup Project
Page 3 and 4: CanacEi X NOVA SCOTIA Minister of t
Page 5 and 6: 4.8 SEWAGE TREATMENT AND SLUDGE MAN
Page 7 and 8: Summary 1 1. SUMMARY In November 19
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Page 16 and 17: 10 Halifax Harbour: The Receiving E
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Page 20 and 21: treatment necessary to meet the wat
Page 22 and 23: 16 Issues that were of concern rega
Page 24 and 25: potential for deleterious interacti
Page 26 and 27: 20 Issues Table 3b Advantages Advan
Page 28 and 29: • Stewardship . Full Cost Account
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Page 34 and 35: 26 Issues Association has developed
Page 36 and 37: 30 Issues 2. ldentify key actors an
Page 38 and 39: 32 Issues Those existing outfalls t
Page 40 and 41: 34 issues Table 5 Advantages Advant
Page 42 and 43: • Options for treatment plants we
Page 46 and 47: 40 Issues 4.8.2 Level of Treatment
Page 48 and 49: 42 Issues SLUDGE TREATMENT (06) Fig
Page 50 and 51: 44 Issues 7. Exhaust gases from the
Page 52 and 53: 46 Issues 0 The predesign report fo
Page 54 and 55: 48 Issues Concerns about the visual
Page 56 and 57: 50 Issues r d) the Project agreemen
Page 58 and 59: 52 Issues 4.10 CONSTRUCTION OF THli
Page 60 and 61: 54 Issues . ;, • negative effects
Page 62 and 63: 56 Issues The Panel approves of HHC
Page 64 and 65: of Halifax) may be left in limbo, a
Page 66 and 67: 60 Issues HHCI has provided a listi
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Page 70 and 71: 64 Issues Loss of lobster fishing a
Page 72 and 73: 66 Recommendations 16. The Panel re
Page 74 and 75: 66 Recommendations I) a survey and
Page 76 and 77: 70 Recommendations 71. The Panel re
Page 78 and 79: APPENDIX B MANDATE FOR THE PANEL RE
Page 80 and 81: 74 APPENDIX C TECHNICAL SPECIALISTS
Page 82 and 83: 76 APRIL 1. 1993 APRIL 3,1993 HALIF
Page 84 and 85: kchemlcal oxygen demand (BOW MoWdow

Halifax Harbour Cleanup Inc. - Halifax Regional Municipality

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