Site assessment of residential

Having a comprehensive understanding of site conditions is critical for Screening LID Options

Desktop Analysis of Background Information

A thorough assessment of background information is critical to understanding site conditions for residential lots or neighborhoods. As you begin gathering and reviewing background information, determine any existing infrastructure gaps and planned upgrades, resident concerns, previous community greening efforts, past water usage and past problems with basement flooding. The following should be considered when conducting a desktop analysis:

• Watershed studies
• Subwatershed studies
• Stormwater master plans
• Sewershed delineation
• Areas with identified storm sewer capacity issues
• Areas contributing to combined sewer overflows
• Areas of degraded water quality
• Areas prone to flooding (both urban and riverine)
• Water quality targets
• Flow targets
• Infiltration targets
• The impact of planned development on existing infrastructure and watershed health
• Source water protection plans
• Wellhead protection areas (quantity and quality)
• Surficial Geology
  • Soil characterization
  • Groundwater levels

Local bylaws and regulations

In addition, be sure to know the relevant local bylaws. Some LID features may contravene local regulations. Below are some examples of typical bylaws and their potential impact on LID planning:

Typical Bylaws	General Provisions May Include:	Impacts on LID Options:
Nuisance weeds and tall grass	Designates tall grass and weeds as a public nuisance Defines “tall grass” as grasses over a maximum height (typically 20 – 30 cm) Requires tall grass to be cut to a height not exceeding the maximum Requires all nuisance weeds and weed seeds to be removed from a property by the owner. The municipality may carry out the work to bring properties into Compliance and recovery costs from the land owner	Vegetated LID practices may be in violation of the relevant bylaw, e.g. landscape naturalization with prairie or ornamental grasses.
Property standards	Sets minimum requirements for privately owned properties Restricts low-lying areas, including those that have been excavated and accumulate water, and requires that they be drained, filled and graded so that water drains to a storm sewer or ditch. Requires that all landscaped areas be cut and maintained in a reasonable condition relative to the neighboring environment	Can preclude the some LID practices, such as bioretention facilities designed be both low-lying and including ‘shallow’ surface ponding. Such bylaws can also prohibit other BMPs which rely on naturalizing landscapes.
Sewer use	Although generally limited to sanitary sewers, many municipalities now include storm water within this by-law. It generally requires all storm water be discharged to an approved outlet and regulates the contents of the discharged water.	May not permit direct discharge of roof water to the municipal storm sewer system. This can include overflow from rainwater harvesting tanks and similar devices.
Standing water	Prevents accumulation of water on an individual property within any depression Often in response to mosquito breeding and West Nile Virus concerns. Accumulation is typically defined by a determined period of time (e.g. 48 hours)	Soakaways, subsurface storage facilities, bioretention and bioswales may be prohibited.
Boulevard planting	Regulates the type of vegetation that can be planted within the boulevard area	Bio-swales or vegetated swales may be constrained by plant-type and plant-height restrictions along municipal boulevards
Roof leader policies (often part of property standards bylaws)	Regulates the collection and allowable discharge location of roof drainage May specify outlet distance from building foundation and may prohibit discharge to storm sewers, impervious surfaces and property boundaries	Progressive roof leader policies can encourage the implementation of rain gardens, soakaways, rain barrels, and other LID practices.

Field Reconnaissance

After concluding a desktop analysis, visiting the neighbourhood in question for field reconnaissance may be ideal. Be sure to look for:

• Neighbourhood characteristics – general impressions
• General lot characteristics
  • % of property coverage by house
  • Driveway sizes
  • Driveway types (% of asphalt, gravel, block pavers, etc.)
  • % of property covered by turf
  • % of property covered by alternative landscaping
  • % of property covered by trees
  • Location and general condition of gardens
  • Distribution and coverage of natural vegetation
  • Location of septic systems
  • Fencing style and location
  • Prevalence of irrigation systems
  • Roadside swales
  • % curb
• Drainage characteristics
• Rooftop / drainage characteristics
• Best management practices info

Once the analysis is complete, proceed to developing a list of recommended actions.

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

A long narrow trench or furrow dug in the ground, as for irrigation, drainage, or a boundary line.

Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

The practice of intercepting, conveying and storing rainwater for future use. Captured rainwater is typically used for outdoor non-potable water uses such as irrigation, or in the building to flush toilets.

Water ponded on the ground surface.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

Natural or artificial means of intercepting and removing surface or subsurface water (usually by gravity).

A hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil.

A mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces.

Human application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47