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==='''Post-construction Operation and Maintenance'''=== | ==='''Post-construction Operation and Maintenance'''=== | ||
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+ | '''Recommended Maintenance Activities For Bioretention Areas '''(Source: | ||
+ | adapted from [[References for bioretetnion|EPA]], 1999) | ||
+ | * '''As needed''' | ||
+ | ** Prune and weed to maintain appearance | ||
+ | ** Mulch replacement when erosion is evident | ||
+ | ** Remove trash and debris | ||
+ | ** Mow filter strip | ||
+ | * '''Semi-annually''' | ||
+ | ** Inspect inflow points for clogging (off-line systems) and remove any sediment | ||
+ | ** Inspect filter strip/grass channel for erosion or gullying and re-seed or sod as necessary | ||
+ | ** Trees and shrubs should be inspected to evaluate their health and remove any dead or severely diseased vegetation | ||
+ | |||
+ | * '''Annually''' | ||
+ | ** Inspect and remove any sediment and debris build-up in pre-treatment areas. | ||
+ | ** Inspect inflow points and bioretention surface for build up of road sand associated with spring melt period, remove as necessary and replant areas that have been impacted by sand/salt build up. | ||
+ | |||
+ | * '''2 to 3 years''' | ||
+ | ** Replace mulch over the entire area | ||
+ | ** Replace pea gravel diaphragm or filter fabric if warranted | ||
+ | ** The planting soils should be tested for pH. If the pH is below 5.2, limestone should be applied. If the pH is above 7.0 to 8.0, then iron sulfate plus sulfur can be added to reduce the pH. | ||
+ | |||
+ | {{alert|A maintenance plan clarifying maintenance responsibility is ''REQUIRED''. Effective long-term operation of bioretention practices necessitates a dedicated and routine maintenance schedule with clear guidelines and schedules. Proper maintenance will not only increase the expected lifespan of the facility but will improve asethetics and property value.|alert-danger}} | ||
+ | Mulch Content and Depth - Fresh shredded bark mulch (Mn/DOT Type 6) should be used when possible to maximize nitrogen retention. If aged mulch is used, use the shredded type instead of the “chip” variety to minimize floating action. The mulch layer should not exceed 3” in depth. Too much mulch can restrict oxygen flow to roots. In addition, mulch should not be mounded around the base of plants since this encourages damage from pests and diseases. | ||
{{alert|A maintenance plan clarifying maintenance responsibility is REQUIRED.|alert-danger}} | {{alert|A maintenance plan clarifying maintenance responsibility is REQUIRED.|alert-danger}} | ||
The most frequently cited maintenance concern for bioretention is surface and under-drain clogging caused by organic matter, fine silts, hydrocarbons, and algal matter. Common operational problems include:
Implicit in the design guidance in the previous sections is the fact that many design elements of bioretention systems can minimize the maintenance burden and maintain pollutant removal efficiency. Key examples include: limiting drainage area, providing easy site access (REQUIRED), providing pre-treatment (REQUIRED), and utilizing native plantings.
Proper construction methods and sequencing play a significant role in reducing problems with operation and maintenance (O&M). In particular, with construction of bioretention practices, the most important action for preventing operation and maintenance difficulties is to ensure that the contributing drainage area has been fully stabilized prior to bringing the practice on line.
Inspections during construction are needed to ensure that the bioretention practice is built in accordance with the approved design and standards and specifications. Detailed inspection checklists should be used that include sign-offs by qualified individuals at critical stages of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. An example construction phase inspection checklist is provided here.
BIORETENTION - Construction inspection checklist
Recommended Maintenance Activities For Bioretention Areas (Source: adapted from EPA, 1999)
Mulch Content and Depth - Fresh shredded bark mulch (Mn/DOT Type 6) should be used when possible to maximize nitrogen retention. If aged mulch is used, use the shredded type instead of the “chip” variety to minimize floating action. The mulch layer should not exceed 3” in depth. Too much mulch can restrict oxygen flow to roots. In addition, mulch should not be mounded around the base of plants since this encourages damage from pests and diseases.
Effective long-term operation of bioretention practices necessitates a dedicated and routine maintenance schedule with clear guidelines and schedules. Proper maintenance will not only increase the expected life span of the facility, but will also improve aesthetics and property value. Some important post-construction considerations are provided below along with RECOMMENDED maintenance standards.
Recommended minimum setback requirements. This represents the minimum distance from the infiltration practice to the structure of concern. If the structure is aboveground, the distance is measured from the edge of the permeable pavement to the structure. If the structure is underground, the setback distance represents the distance from the point of infiltration through the bottom of the permeable pavement system to the structure.
Link to this table
Setback from | Minimum Distance [feet] |
---|---|
Property Line | 10 |
Building Foundation* | 10 |
Private Well | 50 |
Septic System Tank/Leach Field | 35 |
* Minimum with slopes directed away from the building. |