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− | + | #REDIRECT [[Operation and maintenance of stormwater infiltration practices]] | |
− | Effective long-term performance of [[Glossary#I|infiltration]] practices requires an | + | |
+ | Effective long-term performance of [[Glossary#I|infiltration]] practices requires an infiltration management plan (''HIGHLY RECOMMENDED'') and performance monitoring (''HIGHLY RECOMMENDED''). | ||
{{alert|Dedicated and routine maintenance schedule with clear guidelines and schedules are ''REQUIRED''|alert-danger}} | {{alert|Dedicated and routine maintenance schedule with clear guidelines and schedules are ''REQUIRED''|alert-danger}} | ||
− | The | + | The infiltration management plan (operation plan) should address the following items: |
− | <p>The monitoring plan should address the following items: inspection and efficiency assessment | + | *periods of inundation; |
− | <p>Elements to be considered for the development of a maintenance plan are broken into the following categories: Design Phase Maintenance Considerations; Construction Phase Maintenance Considerations; and Post-Construction Maintenance Considerations. In general terms, the most frequently cited maintenance concern for | + | *wet/dry cycling of soils; and |
− | * | + | *operating instructions for drawdown valves gates and removable weirs. |
− | *[[Glossary#E| | + | <p>The monitoring plan should address the following items: |
− | * | + | *inspection and efficiency assessment; |
− | + | *water quality monitoring; and | |
+ | *monitoring of groundwater elevations, long-term infiltration capacity and plant tolerances.</p> | ||
+ | <p>Elements to be considered for the development of a maintenance plan are broken into the following categories: | ||
+ | *Design Phase Maintenance Considerations; | ||
+ | *Construction Phase Maintenance Considerations; and | ||
+ | *Post-Construction Maintenance Considerations. | ||
+ | In general terms, the most frequently cited maintenance concern for infiltration practices is clogging caused by organic matter and fine silts. Common operational problems include: | ||
+ | *clogging and sediment deposition; | ||
+ | *[[Glossary#E|erosion]] of contributing land or in channels leading to the practice; and | ||
+ | *maintaining appropriate surface vegetation. | ||
+ | |||
+ | The table below provides a summary of common problems for infiltration trenches and basins.</p> | ||
+ | |||
{{:Infiltration practices cost components}} | {{:Infiltration practices cost components}} | ||
− | + | ==Design phase maintenance considerations== | |
− | + | Implicit in the design guidance in the previous sections is the fact that many design elements for infiltration systems can minimize the maintenance burden and maintain pollutant removal efficiency. | |
− | + | *Open lawn areas are ''RECOMMENDED'' locations for infiltration practices because of their accessibility. | |
− | *Open lawn areas are ''RECOMMENDED'' locations for | + | *It is ''HIGHLY RECOMMENDED'' that every dry well, infiltration trench and subsurface infiltration system design include an observation well consisting of an anchored 6-inch diameter perforated PVC pipe fitted with a cap to facilitate periodic inspection and maintenance. It is also ''HIGHLY RECOMMENDED'' that infiltration [[Glossary#B|basins]] include a draw down device that can be used for winter diversion and to conduct regular maintenance. |
− | + | *It is ''HIGHLY RECOMMENDED'' that a mechanism such as a multi-stage outlet structure be incorporated into the design of the [[Glossary#P|pre-treatment]] and infiltration practices to facilitate draining for maintenance purposes. | |
− | *It is ''HIGHLY RECOMMENDED'' that every dry well, | + | *It is ''RECOMMENDED'' that a minimum of 3 soil borings or pits be dug in the same location as the proposed infiltration practice. |
− | *It is ''HIGHLY RECOMMENDED'' that a mechanism such as a multi-stage outlet structure be incorporated into the design of the [[Glossary#P|pre-treatment]] and | ||
− | |||
− | + | {{alert|It is ''REQUIRED'' that a way to visually verify proper system operation be installed with each infiltration practice.|alert-danger}} | |
− | + | {{alert|Providing easy access (typically 8 feet wide) to infiltration practices for routine maintenance is ''REQUIRED''|alert-danger}} | |
− | |||
+ | ==Construction phase maintenance considerations== | ||
+ | Infiltration practices are particularly vulnerable during the construction phase for two reasons. First, if the construction sequence is not followed correctly, construction sediment can clog the practice. In addition, heavy construction can result in compaction of the soil, which can then reduce the soil’s infiltration rate. For this reason, a careful construction sequence needs to be followed. Critical construction elements for infiltration practices are shown in the following table. | ||
+ | |||
+ | {{:Infiltration Trench - Construction inspection checklist}} | ||
===Avoid excessive compaction=== | ===Avoid excessive compaction=== | ||
− | {{alert|It is ''REQUIRED'' that in order to prevent soil compaction, the proposed | + | {{alert|It is ''REQUIRED'' that in order to prevent soil compaction, the proposed infiltration area be staked off and marked during construction to prevent heavy equipment and traffic from traveling over it.|alert-danger}} |
− | In addition, it is ''HIGHLY RECOMMENDED'' that the side walls of dry wells and | + | In addition, it is ''HIGHLY RECOMMENDED'' that the side walls of dry wells and infiltration trenches be roughened if they have been smeared by heavy equipment. |
− | + | ===Stabilize vegetation before and after construction=== | |
Excessive sediment loadings can occur without the use of proper erosion and sediment control practices during the construction process. | Excessive sediment loadings can occur without the use of proper erosion and sediment control practices during the construction process. | ||
− | {{alert|It is ''REQUIRED'' that upland drainage areas be properly stabilized with a thick layer of vegetation, particularly immediately following construction, to reduce | + | {{alert|It is ''REQUIRED'' that upland drainage areas be properly stabilized with a thick layer of vegetation, particularly immediately following construction, to reduce sediment loads.|alert-danger}} |
{{alert|If infiltration practices are in-place during construction activities, it is ''REQUIRED'' that sediment and runoff be kept away the infiltration area, such as with diversion berms and soil-stabilizing vegetation around the perimeter of the practice.|alert-danger}} | {{alert|If infiltration practices are in-place during construction activities, it is ''REQUIRED'' that sediment and runoff be kept away the infiltration area, such as with diversion berms and soil-stabilizing vegetation around the perimeter of the practice.|alert-danger}} | ||
===Correctly install filter fabrics=== | ===Correctly install filter fabrics=== | ||
− | Large tree roots should be trimmed flush with the sides of dry wells and infiltration trenches to prevent puncturing or tearing of the filter fabric during subsequent installation procedures. When laying out the geotextile, the width should include sufficient material to compensate for perimeter irregularities in the dry well or trench and for a 6-inch minimum top overlap. The filter fabric itself should be tucked under the sand layer on the bottom of the dry well of infiltration trench, and stones or other anchoring objects should be placed on the fabric at the trench sides to keep the excavation open during windy periods. Voids may occur between the fabric and the excavated sides of the practice. Natural soils should be placed in any voids to ensure fabric conformity to the excavation sides. | + | Large tree roots should be trimmed flush with the sides of dry wells and infiltration trenches to prevent puncturing or tearing of the filter fabric during subsequent installation procedures. When laying out the geotextile, the width should include sufficient material to compensate for perimeter irregularities in the dry well or trench and for a 6-inch minimum top overlap. The filter fabric itself should be tucked under the sand layer on the bottom of the dry well of infiltration trench, and stones or other anchoring objects should be placed on the fabric at the trench sides to keep the excavation open during windy periods. Voids may occur between the fabric and the excavated sides of the practice. Natural soils should be placed in any voids to ensure fabric conformity to the excavation sides. |
===Carefully finish final grading=== | ===Carefully finish final grading=== | ||
Initial infiltration basin excavation should be carried to within 2 feet of the final elevation of the basin floor. | Initial infiltration basin excavation should be carried to within 2 feet of the final elevation of the basin floor. | ||
− | {{alert|It is ''REQUIRED'' that | + | {{alert|It is ''REQUIRED'' that infiltration systems not be excavated to final grade until the contributing drainage area has been constructed and fully stabilized.|alert-danger}} |
The final phase excavation should remove all accumulated sediment and be done by light tracked equipment to avoid compaction of the basin floor and provide a well-aerated, highly porous surface texture. | The final phase excavation should remove all accumulated sediment and be done by light tracked equipment to avoid compaction of the basin floor and provide a well-aerated, highly porous surface texture. | ||
Line 59: | Line 73: | ||
*Inspections during construction are needed to ensure that the infiltration 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 designer. | *Inspections during construction are needed to ensure that the infiltration 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 designer. | ||
− | + | ==Post-construction operation and maintenance== | |
− | |||
− | |||
{{alert|A maintenance plan clarifying maintenance responsibility is ''REQUIRED''.|alert-danger}} | {{alert|A maintenance plan clarifying maintenance responsibility is ''REQUIRED''.|alert-danger}} | ||
− | + | Effective long-term operation of infiltration practices necessitates a dedicated and routine maintenance schedule with clear guidelines and schedules. Some important post-construction maintenance considerations are provided below. | |
*A legally binding and enforceable maintenance agreement should be executed between the practice owner and the local review authority. | *A legally binding and enforceable maintenance agreement should be executed between the practice owner and the local review authority. | ||
− | *Adequate access must be provided for all | + | *Adequate access must be provided for all infiltration practices for inspection, maintenance, and landscaping upkeep, including appropriate equipment and vehicles. |
− | *General | + | *General infiltration trench maintenance activities and schedule are provided in the tables below. |
− | |||
− | |||
{{:Typical maintenance problems for infiltration trenches and basins}} | {{:Typical maintenance problems for infiltration trenches and basins}} | ||
{{:Typical maintenance activities for infiltration trenches}} | {{:Typical maintenance activities for infiltration trenches}} | ||
+ | |||
+ | <noinclude> | ||
+ | ==Related pages== | ||
+ | *[[Overview for Infiltration trench]] | ||
+ | *[[Types of Infiltration trench]] | ||
+ | *[[Design criteria for Infiltration trench]] | ||
+ | *[[Construction specifications for Infiltration trench]] | ||
+ | *[[Operation and maintenance of Infiltration trench]] | ||
+ | *[[Assessing the performance of infiltration trenches and basins]] | ||
+ | *[[Cost-benefit considerations for Infiltration trench]] | ||
+ | *[[External resources for Infiltration trench ]] | ||
+ | *[[References for infiltration]] | ||
+ | |||
+ | [[Category:Level 3 - Best management practices/Specifications and details/Operation and maintenance]] | ||
+ | </noinclude> |
Effective long-term performance of infiltration practices requires an infiltration management plan (HIGHLY RECOMMENDED) and performance monitoring (HIGHLY RECOMMENDED).
The infiltration management plan (operation plan) should address the following items:
The monitoring plan should address the following items:
Elements to be considered for the development of a maintenance plan are broken into the following categories:
In general terms, the most frequently cited maintenance concern for infiltration practices is clogging caused by organic matter and fine silts. Common operational problems include:
The table below provides a summary of common problems for infiltration trenches and basins.
Summary of infiltration practices cost components.
Link to this table
Implementation Stage | Primary Cost Components | Basic Cost Estimate | Other Considerations |
---|---|---|---|
Site Preparation | Tree & plant protection | Protection Cost ($/acre) * Affected Area (acre) | Removal of existing structures, topsoil removal and stockpiling |
Infiltration area protection | Silt fence cost ($/’foot) * Perimeter of infiltration area | ||
Clearing & grubbing | Clearing Cost ($/acre) * Affected Area (acre) | ||
Topsoil salvage | Salvage Cost ($/acre) * Affected Area | ||
Site Formation | Excavation / grading | X-ft Depth Excavation Cost ($/acre) * Area (acre) | Soil & rock fill material, tunneling |
Hauling material offsite | Excavation Cost * (% of Material to be hauled away) | ||
Structural Components | Vault structure (for underground infiltration) | ($/structure) | Pipes, catchbasins, manholes, valves, vaults |
Media (for infiltration trenches) | Media cost ($/cubic yard) * filter volume (cubic yard) | ||
Geotextile | Geotextile cost ($/cy) * area of trench, including walls | ||
inlet structure | ($/structure) | ||
Overflow structure | ($/structure) | ||
Observation well | ($/structure) | ||
Site Restoration | Soil preparation | Topsoil or amendment cost ($/acre) * Area (acre) | Tree protection, soil amendments, seed bed preparation, trails |
Seeding | Seeding Cost ($/acre) * Seeded Area (acre) | ||
Filter strip | Sod cost ($/square foot) * filter strip area | ||
Planting / transplanting | Planting Cost ($/acre) * Planted Area (acre) | ||
Annual Operation, Maintenance, and Inspection | Sediment removal | Removal Cost ($/acre) * Area (acre) * Frequency (1 time per 5 years) | Vegetation maintenance, cleaning of structures |
Debris removal | Removal Cost ($/acre) * Area (acre) * Frequency (2 time per year) | ||
Inspection | Inspection Cost ($) * Inspection Frequency (6 times per year) | ||
Mowing (for some vegetative filters) | Mowing Cost ($) * Mowing Frequency (6 times per year) |
Implicit in the design guidance in the previous sections is the fact that many design elements for infiltration systems can minimize the maintenance burden and maintain pollutant removal efficiency.
Infiltration practices are particularly vulnerable during the construction phase for two reasons. First, if the construction sequence is not followed correctly, construction sediment can clog the practice. In addition, heavy construction can result in compaction of the soil, which can then reduce the soil’s infiltration rate. For this reason, a careful construction sequence needs to be followed. Critical construction elements for infiltration practices are shown in the following table.
Infiltration Trench and infiltration basin - Construction inspection checklists.
Link to this table
To access an Excel version of form (for field use), click here.
Project: | ||
Location: | ||
Site Status: | ||
Date: | ||
Time: | ||
Inspector: | ||
Construction Sequence | Satisfactory / Unsatisfactory | Comments |
---|---|---|
1. Pre-Construction | ||
Pre-construction meeting | ||
Runoff diverted | ||
Soil permeability verified | ||
Groundwater / bedrock verified | ||
Project benchmark established | ||
Facility location staked out | ||
Temporary erosion and sediment control established | ||
2. Excavation | ||
Size and location per plans | ||
Side slopes stable | ||
Depth adjusted to soil layer with specified soil type and permeability | ||
Sub-soil not adjacent to excavation area and stabilized with vegetation and/ or silt fence | ||
Stockpile location not adjacent to excavation area and stabilized with vegetation and/ or silt fence | ||
3. Filter Fabric Placement | ||
Fabric per specifications | ||
Fabric per specifications | ||
Placed per plan location | ||
4. Aggregate Material | ||
Size as specified | ||
Clean / washed material | ||
Placed properly | ||
5. Observation Well | ||
Pipe size per plans | ||
Under-drain installed per plans | ||
Inlet installed per plans | ||
Pre-treatment devices installed per plans | ||
6. Vegetation | ||
Complies with planting specifications | ||
Topsoil complies with composition and placement in specifications | ||
Permanent erosion control measures in place | ||
7. Final Inspection | ||
Dimensions per plans | ||
Check dams operational | ||
Inlet / outlet operational | ||
Effective stand of vegetation and stabilization | ||
Contributing watershed stabilized before flow is routed to the facility | ||
Comments: | ||
Actions to be taken: |
In addition, it is HIGHLY RECOMMENDED that the side walls of dry wells and infiltration trenches be roughened if they have been smeared by heavy equipment.
Excessive sediment loadings can occur without the use of proper erosion and sediment control practices during the construction process.
Large tree roots should be trimmed flush with the sides of dry wells and infiltration trenches to prevent puncturing or tearing of the filter fabric during subsequent installation procedures. When laying out the geotextile, the width should include sufficient material to compensate for perimeter irregularities in the dry well or trench and for a 6-inch minimum top overlap. The filter fabric itself should be tucked under the sand layer on the bottom of the dry well of infiltration trench, and stones or other anchoring objects should be placed on the fabric at the trench sides to keep the excavation open during windy periods. Voids may occur between the fabric and the excavated sides of the practice. Natural soils should be placed in any voids to ensure fabric conformity to the excavation sides.
Initial infiltration basin excavation should be carried to within 2 feet of the final elevation of the basin floor.
The final phase excavation should remove all accumulated sediment and be done by light tracked equipment to avoid compaction of the basin floor and provide a well-aerated, highly porous surface texture.
It is HIGHLY RECOMMENDED that construction of sediment practices be suspended during snowmelt or rainfall, in order to prevent soil smearing, clumping, or compaction.
Effective long-term operation of infiltration practices necessitates a dedicated and routine maintenance schedule with clear guidelines and schedules. Some important post-construction maintenance considerations are provided below.
Typical maintenance problems for infiltration trenches and basins.
Link to this table
Problem | Practices Applied To | Comments |
---|---|---|
Clogging, sediment deposition | Both | Key issue for infiltration practice. Requires vigilant inspection and maintenance. |
Surface Vegetation | Both | Often important to maintain vigorous growth at the base of infiltration practices (basins). Important to restrict woody vegetation from the surface of infiltration trenches. |
Erosion of contributing land or in channels leading to practice | Both | In these practices, it is important to monitor not only the practice itself, but also upland infiltration to minimize the sediment load. |
Damage to filter fabric | Trench | Infrequent but important maintenance concern. |
Scouring at Inlet | Both | Similar issues to Ponds. Need to promote non-erosive flows that are evenly distributed |
Access Issues | Both | Similar issues to Ponds. Need access for inspection and maintenance. |
Concrete Failure | Basins, if they include a riser structure | Similar issues to ponds and wetlands. |
Problems with the Embankment | Basins | Similar issues to dry ponds. |
Typical maintenance activities for infiltration trenches and infiltration basins.
Link to this table
Activity | Schedule |
---|---|
Replace pea gravel/topsoil and top surface filter fabric (when clogged). | As needed |
Ensure that contributing area, practice and inlets are clear of debris. Ensure that the contributing area is stabilized. Remove sediment and oil/grease from pre-treatment devices, as well as overflow structures. Mow grass filter strips should be mowed as necessary. Remove grass clippings. Repair undercut and eroded areas at inflow and outflow structures |
Monthly |
Inspect pre-treatment devices and diversion structures for sediment build-up and structural damage. Remove trees that start to grow in the vicinity of the trench. | Semi-annual Inspection |
Disc or otherwise aerate basin bottom. De-thatch basin bottom. | Annually |
Scrape basin bottom and remove sediment. Restore original crosssection and infiltration rate. Seed or sod to restore ground cover. | Every 5 years |
Perform total rehabilitation of the trench to maintain design storage capacity. Excavate trench walls to expose clean soil | Upon Failure |
This page was last edited on 15 December 2022, at 02:59.