Question 6 of 7: Solid Waste, Sanitary Sewer Overflows and Industrial VOC Discharge

Problem 6: Solid Waste, Sanitary Sewer Overflows and Industrial VOC Discharge (20 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Three EIA issues for the expanding landfill. 1. Leachate generation and groundwater protection. Doubling production doubles the waste volume reaching the landfill, which raises leachate generation and loading on the liner/leachate-collection system; the EIA must confirm the liner design and leachate treatment capacity are sized for the projected post-expansion volume, not just the current one, and must reassess groundwater monitoring well coverage around the expanded footprint. 2. Landfill gas generation and management. Increased organic and putrescible content arriving with a doubled waste stream increases methane generation; the EIA must address gas collection and flaring (or energy recovery) capacity to manage both greenhouse-gas emissions and off-site migration/explosion risk. 3. Remaining site capacity and buffer planning. A doubled waste stream shortens the landfill's remaining service life, so the EIA must present a revised capacity/closure timeline and confirm that odour, vector, noise and traffic buffer distances to neighbouring land uses remain adequate at the higher throughput, not just at today's volume.

(ii) Two SSO-reduction solutions. 1. Sewer rehabilitation to reduce infiltration and inflow (I&I). Cured-in-place pipe (CIPP) lining, manhole sealing and disconnecting private sump pumps/downspouts from the sanitary system reduce the base I&I load that causes the system to surcharge during wet weather. Benefit: addresses the root cause, is cost-effective over the long term, and reduces hydraulic loading on the downstream treatment plant as well as the pumping station. Challenge: high upfront capital cost, disruptive construction in an established neighbourhood, and diminishing returns — eliminating the last increments of I&I in an old system is disproportionately expensive. 2. Pumping station capacity upgrade and wet-weather storage/equalization. Increasing pump/wet-well capacity or adding an off-line storage basin that fills during peak wet-weather flow and drains back once the peak passes directly reduces overflow frequency. Benefit: immediate, reliable reduction in SSO events without waiting for a multi-year rehabilitation program. Challenge: does not address the root cause (I&I still enters the system), and requires capital and land for the storage basin plus higher ongoing pumping/O&M energy cost.

(iii) Technical and non-technical VOC solutions. Taking trichloroethylene (TCE) from a metal-degreasing operation as the common industrial VOC. Technical solution: install a vapour-phase granular activated carbon (GAC) adsorption unit (or a catalytic oxidizer for higher-concentration streams) on the degreaser's exhaust to capture or destroy the TCE before it reaches the atmosphere near the residential community. Non-technical solution: pollution prevention through material substitution — replace the TCE-based solvent with a non-VOC, aqueous-based degreasing agent, eliminating the emission at the source rather than treating it, paired with a community notification and ambient-air monitoring program so residents can verify the substitution's effectiveness.