Table 1

Urban Stormwater Management Alternatives for Shirley's Brook/Watts Creek

Stormwater Management	Benefit	Disadvantage	Applicability to Shirley's Brook/ Watts Creek	Life	Cost
Source Control Measures
Disconnection of Roof Leaders

with or without

•	splash pads

•	cisterns

•	ponding

•	soakaway	-decreased runoff quantity to receiving system; increased infiltration

-runoff detainment

-potential for some water quality benefit	-potential for home owner inconvenience (i.e., ponding water, clogging of pond outlet/soakaway pit if implemented)

-difficult to implement in existing development	-roof runoff is relatively clean, the disconnection will reduce the runoff into the watercourses and therefore reduce in-stream erosion potential .

-recommended for new and re-development residential areas on a lot by lot basis, where suitable soils exist.	Long	Low
Disconnection of Foundation Drains	-decreased runoff quantity to receiving system; increased infiltration	-requires sump pump

-difficult to implement in existing developments	-foundation drain runoff is relatively clean, the disconnection will reduce the runoff into the watercourses and therefore reduce in-stream erosion potential.

.-recommended for new and re-development residential areas on a lot by lot basis, where suitable soils exist.	Long	Low
Catch Basin Restrictors/

Control Orifices	-runoff detainment

-potential for limited sediment removal	-potential for clogging

-inconvenience due to ponding water	-new development major-minor system should be designed without the need for catch basin restrictors.

-recommended for retrofit areas	Short	Low
Reduced Lot Grading	-decreased runoff quantity to receiving system; increased infiltration and evapo- transpiration

-runoff detainment

-some water quality benefit	-potential for home owner inconvenience (i.e., longer lot drainage time)

-vulnerable to alterations by home owner, difficult to regulate

-used mainly for new developments where topography permits	-reduced lot grading will increase infiltration and reduce the runoff into the watercourses and therefore reduce in-stream erosion potential.

-recommended for new and re-development residential areas on a lot by lot basis, where suitable soils exist.	Long	Low
Rooftop Storage	-runoff detainment	-difficult to retrofit

-only suitable for flat industrial or commercial roofs	-only feasible for commercial/industrial development. It could reduce the peak runoff into the watercourses and therefore reduce in- stream erosion potential.

-recommended for new commercial and industrial developments.	Med	Med
Parking Lot Storage	-decreased peak flow to receiving system	-more suitable for commercial and industrial areas

-represents potential hazard to motorists and pedestrians	-it could reduce the peak runoff into the watercourses and therefore reduce in-stream erosion potential, also some improvement to water quality.

-recommended, for new and retrofit developments.	Med	Med
Porous Pavement	-decreased runoff quantity to receiving system; increased infiltration	-potential for ground water contamination

-potential for clogging

-not tried in Ontario	-not well tested for Ontario conditions. Suggest that a pilot study should be carried out (not part of this project) to tests its efficiency and feasibility within the study area.	Med	High
Slope Stabilization and Erosion Control Measures	-reduced maintenance of SWMPs

-improved water quality	-will reduce erosion and thereby the amount of sediment entering the watercourses.

-recommended for new and retrofit developments.	Med	Low
Conveyance Control Measures
Road Drainage

•	Grassed Swales	-potential for decreased runoff quantity to receiving system; increased infiltration

-runoff detainment

-improved water quality

-generally preferred over ditches by the public	-mosquito breeding ground

-require more land than conventional ditches	-preferred road drainage alternative, it has some water quality improvement component. Recommended for new and retrofit developments where feasible.	Med	Low
Channel/Outlet Protection	-decreased erosion

-improved water quality (i.e., decreased sediment loading)	-disruption of natural habitat	-recommended for new and retrofit developments, but must not disrupt the local habitat	Long	Med
Pervious Pipe System	-decreased runoff quantity to receiving system; increased infiltration	-potential for ground water contamination

-potential for clogging

-high cost of replacing existing sewer

-specific site requirement	-limited use due to local soil conditions

-not recommended , unless local soil conditions suitable for infiltration	Med	Med

Stormwater Management	Advantage	Disadvantage	Applicability	Life	Cost
End of Pipe Control Measures
Detention/

Retention Facilities

(Dry, Wet and Extended detention ponds)	-water quantity control

-improved water quality

-potential for downstream erosion control

-potential for spill control	-potential for sediment re-suspension (dry ponds)

-potential for thermal warming (extended detention)

-potential for odour, algae, debris and/or mosquitoes (wet ponds)

-potential for outlet clogging

-not suitable/economical for small areas, wet ponds require more land area than dry ponds, although both are land consumptive	-would improve water quality, the efficiency of ponds in settling pollutants should be studied as it may be difficult to settle the fine clay particles present in the local soils.

-wet ponds recommended for new and retrofit developments for area >10 ha, subject to above	Long	High
Underground Storage	-decreased runoff peak

-improved water quality	-difficult to keep clean	-generally used as retrofit in existing developed areas where space is at a premium.	Long	High
Artificial Wetlands	-runoff detainment

-potential for water quantity control

-improved water quality

-potential for downstream erosion control

-effective for spill treatment	-potential for thermal warming

-potential for outlet clogging

-potential for mosquitoes

-not suitable/economical for small areas

-may have plant sustainability

problems where road salts are applied

-requires significant land area	-would improve water quality, the efficiency of wetlands in settling pollutants should be studied as it may be difficult to settle the fine clay particles present in the local soils.

--recommended for new and retrofit developments for area >10 ha, subject to above	Long	High
Infiltration Basins/Trenches	-decreased runoff quantity to receiving system; increased infiltration if allowed to recharge ground water system

-improved water quality if collected and discharged	-potential for clogging/ compaction

-potential for ground water mounding

-potential for ground water contamination

-operation/maintenance problems reported

-pre-treatment suggested

-specific site requirement	-would improve water quality, but it could be difficult to settle the fine clay particles present in the local soils.

-subject to suitable soils, bedrock and water table conditions

- limited use for new or retrofit areas.	Shor t to Med	High
Filter/Buffer Strips	-potential for decreased runoff quantity to receiving system; increased infiltration and evapo-transpiration

-runoff detainment

-improved water quality

-erosion protection	-potential for clogging	-for new or retrofit development areas

< 2 ha

- limited use.	Short	Low
Oil and Grit Separators	-limited runoff detainment

-improved water quality

-spill control	-can only control limited areas

-not suitable for quantity control

-not suitable for soluble pollutants	-mainly suitable for industrial and commercial areas.

-recommended for new and retrofit industrial and commercial area < 2 ha and with other SWM facilities	Med	Med