m (→References) |
|||
(17 intermediate revisions by the same user not shown) | |||
Line 1: | Line 1: | ||
[[File:Technical information page image.png|100px|right|alt=image]] | [[File:Technical information page image.png|100px|right|alt=image]] | ||
+ | [[File:Pdf image.png|100px|thumb|alt=pdf image|<font size=3>[https://stormwater.pca.state.mn.us/index.php?title=File:Operation_and_maintenance_(O%26M)_of_filter_strips_-_Minnesota_Stormwater_Manual.pdf Download pdf]</font size>]] | ||
[[File:Filter strip before rain garden 1.jpg|300px|thumb|alt=Image of a vegetated filter strip|<font size=3>Image of a vegetated filter strip</font size>]] | [[File:Filter strip before rain garden 1.jpg|300px|thumb|alt=Image of a vegetated filter strip|<font size=3>Image of a vegetated filter strip</font size>]] | ||
Line 19: | Line 20: | ||
Vegetated filter strips require dedicated and regular maintenance to ensure proper and long-lasting operation, and in most cases a vegetated filter strip should be designed to be effective for at least 10 years | Vegetated filter strips require dedicated and regular maintenance to ensure proper and long-lasting operation, and in most cases a vegetated filter strip should be designed to be effective for at least 10 years | ||
− | ([https:// | + | ([https://bwsr.state.mn.us/common-alternative-practice-2-nrcs-filter-strip-standard-mn-393391-practice-standards-public-waters NRCS], 2010). The most frequently cited O&M concerns for vegetated filter strips include |
*flow channelization and erosion, | *flow channelization and erosion, | ||
*insufficient/inadequate vegetative cover, and | *insufficient/inadequate vegetative cover, and | ||
Line 56: | Line 57: | ||
==Construction phase O&M considerations== | ==Construction phase O&M considerations== | ||
Proper construction methods and sequencing play a significant role in reducing O&M problems. Some key items during the construction phase include the following. | Proper construction methods and sequencing play a significant role in reducing O&M problems. Some key items during the construction phase include the following. | ||
− | *Before construction begins | + | *'''Before construction begins''' |
− | **Check the grading where the practice will be placed to enable sheet flow from the level spreader and throughout the filter strip. Grading must be uniformly perpendicular to the direction of flow to prevent channelized | + | **Check the grading where the practice will be placed to enable <span title="Water, usually storm runoff, flowing in a thin layer over the ground surface. A synonym is overland flow."> '''sheet flow'''</span> from the <span title="Level Spreaders are measures that reduce the erosive energy of concentrated flows by distributing runoff as sheet flow to stabilized vegetative surfaces."> '''level spreader'''</span> and throughout the filter strip. Grading must be uniformly perpendicular to the direction of flow to prevent <span title="Water flow focused into individual straight pathways rather than across a broad area (sheet flow)"> '''channelized flow'''</span>. |
− | **Protect the proposed filter strip from the surrounding area by using upstream sediment traps or barriers and diversions to direct stormwater flows from the contributing drainage area away from the practice. | + | **Protect the proposed filter strip from the surrounding area by using upstream <span title="Sediment traps and basins are settling ponds formed by excavation and/or an embankment"> [https://stormwater.pca.state.mn.us/index.php?title=Sediment_control_practices_-_Sediment_traps_and_basins '''sediment traps''']</span> or barriers and diversions to direct stormwater flows from the contributing drainage area away from the practice. |
**Install any needed <span title="Practices designed to prevent or minimize erosion> [https://stormwater.pca.state.mn.us/index.php?title=Erosion_prevention_practices '''erosion''']</span> and <span title="practices designed to prevent or minimize loss of eroded soil at a site"> [https://stormwater.pca.state.mn.us/index.php?title=Sediment_control_practices '''sediment controls''']</span> in your construction site and prepare a [https://stormwater.pca.state.mn.us/index.php?title=SWPPP_Template_for_Small_Construction_Sites storm water pollution prevention plan (SWPPP)]</span>. | **Install any needed <span title="Practices designed to prevent or minimize erosion> [https://stormwater.pca.state.mn.us/index.php?title=Erosion_prevention_practices '''erosion''']</span> and <span title="practices designed to prevent or minimize loss of eroded soil at a site"> [https://stormwater.pca.state.mn.us/index.php?title=Sediment_control_practices '''sediment controls''']</span> in your construction site and prepare a [https://stormwater.pca.state.mn.us/index.php?title=SWPPP_Template_for_Small_Construction_Sites storm water pollution prevention plan (SWPPP)]</span>. | ||
**Designate a stormwater supervisor to make sure someone is responsible for erosion and sediment control. | **Designate a stormwater supervisor to make sure someone is responsible for erosion and sediment control. | ||
**Hold a pre-construction meeting with the designer and the installer to review the construction plans and the sequencing of construction. | **Hold a pre-construction meeting with the designer and the installer to review the construction plans and the sequencing of construction. | ||
− | *During construction | + | *'''During construction''' |
**Construct any pretreatment devices first. | **Construct any pretreatment devices first. | ||
**Implement soil stabilization measures until permanent vegetation is established. | **Implement soil stabilization measures until permanent vegetation is established. | ||
**Use as much of the existing topsoil on the site as possible to enhance plant growth. | **Use as much of the existing topsoil on the site as possible to enhance plant growth. | ||
− | **Prevent soil compaction by marking boundaries of the practice to ensure no construction traffic occurs on the practice. Foot traffic should be minimized if possible. | + | **Prevent <span title="The compression of soil particles into a smaller volume, which reduces the size of pore space available for air and water."> '''soil compaction'''</span> by marking boundaries of the practice to ensure no construction traffic occurs on the practice. Foot traffic should be minimized if possible. |
**Ensure that the plant and vegetation mix conforms to the vegetation design plan. | **Ensure that the plant and vegetation mix conforms to the vegetation design plan. | ||
**Inspect the practice during construction to ensure that the vegetated filter strip practice is built in accordance with the approved design and standards and specifications. | **Inspect the practice during construction to ensure that the vegetated filter strip practice is built in accordance with the approved design and standards and specifications. | ||
− | *After construction | + | *'''After construction''' |
**Verify that the vegetated filter strip practice was built in accordance with the approved design and standards and specifications. | **Verify that the vegetated filter strip practice was built in accordance with the approved design and standards and specifications. | ||
**Verify that the filter strip area is fully stabilized with vegetation prior to removing any barriers, diversions, or erosion and sediment control measures. | **Verify that the filter strip area is fully stabilized with vegetation prior to removing any barriers, diversions, or erosion and sediment control measures. | ||
**Verify that the practice directs flow as intended over the entirety of the practice. This serves as a verification that the practice is functional at the time of construction. | **Verify that the practice directs flow as intended over the entirety of the practice. This serves as a verification that the practice is functional at the time of construction. | ||
− | **Use a detailed inspection checklists that include sign-offs by qualified individuals at the completion 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 | + | **Use a detailed inspection checklists that include sign-offs by qualified individuals at the completion 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 [https://stormwater.pca.state.mn.us/index.php?title=Operation_and_maintenance_(O%26M)_of_filter_strips#Useful_resources below]. |
**Review and discuss the plant warranty/establishment period with the plant provider to understand the conditions under which failing plants will be replaced. | **Review and discuss the plant warranty/establishment period with the plant provider to understand the conditions under which failing plants will be replaced. | ||
− | **Determine if stormwater should be kept offline from the practice until the seedlings are established. | + | **Determine if stormwater should be kept <span title="A stormwater system in which part or all of the stormwater runoff is diverted from the primary treatment practice. Partial diversion is employed for bypass runoff, which is runoff in excess of the designed treatment volume of the practice. Full offline diversion is employed as a temporary means to divert all runoff from a stormwater practice, typically to avoid erosion of exposed soil or establishment of vegetation."> '''offline'''</span> from the practice until the seedlings are established. |
− | **The design/construction team should provide the O&M team with the following information to be included in the O&M plan | + | **The design/construction team should provide the O&M team with the following information to be included in the O&M plan. |
***The plant warranty. | ***The plant warranty. | ||
− | ***The | + | ***The <span title="As-built refers to a drawing that shows the existing dimensions and conditions of a stormwater structure or device."> '''as-built'''</span> plans of the practice |
***A list of conditions that might cause failure of the practice if not properly maintained. | ***A list of conditions that might cause failure of the practice if not properly maintained. | ||
Line 85: | Line 86: | ||
Some important post-construction considerations are provided below along with recommended maintenance standards. | Some important post-construction considerations are provided below along with recommended maintenance standards. | ||
− | *A site-specific '''Operations and Maintenance Plan''' should be prepared by the designer prior to putting the practice into operation. This plan should provide any operating procedures related to the practices. The plan should also provide clear maintenance expectations, activities, and schedules. Include photos if possible. Be clear about who is responsible for the maintenance and the type of expertise that will be needed for distinct O&M activities. The O&M plan should include an anticipated budget for O&M activities. The O&M plan should also include an example O&M inspection checklist and an example maintenance report. Example O&M plans and checklists are provided in the | + | *A site-specific '''Operations and Maintenance Plan''' should be prepared by the designer prior to putting the practice into operation. This plan should provide any operating procedures related to the practices. The plan should also provide clear maintenance expectations, activities, and schedules. Include photos if possible. Be clear about who is responsible for the maintenance and the type of expertise that will be needed for distinct O&M activities. The O&M plan should include an anticipated budget for O&M activities. The O&M plan should also include an example O&M inspection checklist and an example maintenance report. Example O&M plans and checklists are provided in the [https://stormwater.pca.state.mn.us/index.php?title=Operation_and_maintenance_(O%26M)_of_filter_strips#Useful_resources Useful Resources section]. |
− | *A legally binding and enforceable maintenance agreement should be executed between the practice owner and the local review authority that provides adequate access for the inspection, maintenance, and necessary equipment. Example maintenance agreements are provided in the | + | *A legally binding and enforceable maintenance agreement should be executed between the practice owner and the local review authority that provides adequate access for the inspection, maintenance, and necessary equipment. Example maintenance agreements are provided in the [https://stormwater.pca.state.mn.us/index.php?title=Operation_and_maintenance_(O%26M)_of_filter_strips#Useful_resources Useful Resources section]. |
*Inspection and maintenance activities are distinct and can be done as separate activities or together. Inspection will typically assess the practice for any O&M issues, whereas maintenance will address the O&M issues identified by the inspection. A dedicated inspection effort on a large number of BMPs can help prioritize maintenance activities. | *Inspection and maintenance activities are distinct and can be done as separate activities or together. Inspection will typically assess the practice for any O&M issues, whereas maintenance will address the O&M issues identified by the inspection. A dedicated inspection effort on a large number of BMPs can help prioritize maintenance activities. | ||
*While maintenance is being conducted, ensure that no heavy vehicle traffic occurs on the vegetated filter strip and foot traffic is limited to avoid compaction. | *While maintenance is being conducted, ensure that no heavy vehicle traffic occurs on the vegetated filter strip and foot traffic is limited to avoid compaction. | ||
Line 98: | Line 99: | ||
==Maintenance costs== | ==Maintenance costs== | ||
− | Maintenance costs will vary on a number of factors, including but not limited to | + | Maintenance costs will vary on a number of factors, including but not limited to the following. |
− | *Size of the practice and its contributing drainage area | + | *Size of the practice and its <span title="The total drainage area, including pervious and impervious surfaces, contributing to a BMP"> '''[https://stormwater.pca.state.mn.us/index.php?title=Contributing_drainage_area_to_stormwater_BMPs contributing drainage area]'''</span> |
*Type of plantings used | *Type of plantings used | ||
*Site visit frequency | *Site visit frequency | ||
Line 109: | Line 110: | ||
*Equipment needed | *Equipment needed | ||
− | Preventative maintenance is key to minimizing major costs associated with repairs. The annual cost of maintaining filter strips (mowing, weeding, inspection, litter removal, etc.) is generally between $100 and $1,400 per acre (based on 2006 cost estimate, PADEP 2006). Maintenance may be higher the first few years, while plants are being established. | + | Preventative maintenance is key to minimizing major costs associated with repairs. The annual cost of maintaining filter strips (mowing, weeding, inspection, litter removal, etc.) is generally between $100 and $1,400 per acre (based on 2006 cost estimate, [http://www.depgreenport.state.pa.us/elibrary/GetFolder?FolderID=4673 PADEP 2006]). Maintenance may be higher the first few years, while plants are being established. |
==Useful resources== | ==Useful resources== | ||
===Additional detailed O&M information=== | ===Additional detailed O&M information=== | ||
− | + | Supplemental information can be found on the page called [[Operation and maintenance of filter strips - supplemental information]]. Supplemental information includes the following. | |
− | + | *Removing sediment and debris buildup | |
− | *Removing sediment debris | + | *Preventing or minimizing <span title"the removal or erosion of material captured by a stormwater device, typically a result of subsequent high flow volumes or rates or inadequate maintenance of the device"> '''washout'''</span> and erosion of the <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> vegetated filter strip |
− | *Preventing or minimizing | ||
*Vegetation establishment | *Vegetation establishment | ||
*Maintaining vegetation | *Maintaining vegetation | ||
− | *Snow | + | *Snow storage |
*Maintenance agreements | *Maintenance agreements | ||
− | *Additional | + | *Additional references |
===Case studies=== | ===Case studies=== | ||
Line 128: | Line 128: | ||
===Maintenance training documents and videos=== | ===Maintenance training documents and videos=== | ||
− | *Chesapeake Stormwater Network: Filter Strips and Grass Channels Webcast Slides | + | *[https://chesapeakestormwater.net/tag/filter-strip/ Chesapeake Stormwater Network: Filter Strips and Grass Channels Webcast Slides] |
− | *UMass Amherst: Vegetative Filter Strips May Deter Pesticide Runoff | + | *[https://www.youtube.com/watch?v=Sw-Aj7ADfWw UMass Amherst: Vegetative Filter Strips May Deter Pesticide Runoff] - YouTube video |
===O&M resource catalog=== | ===O&M resource catalog=== | ||
Line 138: | Line 138: | ||
==References== | ==References== | ||
*PADEP. 2006. [http://www.depgreenport.state.pa.us/elibrary/GetFolder?FolderID=4673 Pennsylvania Stormwater Best Management Practices Manual]. Volume 34. | *PADEP. 2006. [http://www.depgreenport.state.pa.us/elibrary/GetFolder?FolderID=4673 Pennsylvania Stormwater Best Management Practices Manual]. Volume 34. | ||
− | *NRCS, 2010. [https:// | + | *NRCS, 2010. [https://bwsr.state.mn.us/common-alternative-practice-2-nrcs-filter-strip-standard-mn-393391-practice-standards-public-waters Conservation Practice Standard]. |
+ | |||
+ | <noinclude> | ||
+ | |||
+ | ==Related pages== | ||
+ | *[[Overview for pretreatment vegetated filter strips]] | ||
+ | *[[Design, construction, operation and maintenance specifications for pretreatment vegetated filter strips]] | ||
+ | ===Green infrastructure O&M=== | ||
+ | *[[Green Stormwater Infrastructure (GSI) and sustainable stormwater management]] | ||
+ | *Operation and maintenance of green infrastructure practices | ||
+ | **[[Operation and maintenance of bioretention and other stormwater infiltration practices]] | ||
+ | **[[Operation and maintenance of bioretention and other stormwater infiltration practices - supplemental information]] | ||
+ | **[[Operation and maintenance (O&M) of tree trenches and tree boxes]] | ||
+ | **[[Operation and maintenance of tree trenches and tree boxes - supplemental information]] | ||
+ | **[[Operation and maintenance (O&M) of green roofs]] | ||
+ | **[[Operation and maintenance of green roofs - supplemental information]] | ||
+ | **[[Operation and maintenance (O&M) of swales]] | ||
+ | **[[Operation and maintenance of swales - supplemental information]] | ||
+ | **[[Operation and maintenance (O&M) of filter strips]] | ||
+ | **[[Operation and maintenance of filter strips - supplemental information]] | ||
+ | **[[Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices]] | ||
+ | **[[Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices - supplemental information]] | ||
+ | **[[Operation and maintenance (O&M) of stormwater treatment wetland practices]] | ||
+ | **[[Operation and maintenance (O&M) of permeable pavement]] | ||
+ | **[[Operation and maintenance (O&M) of permeable pavement - supplemental information]] | ||
+ | |||
+ | [[Category:Level 3 - Best management practices/Specifications and details/Operation and maintenance]] | ||
+ | </noinclude> |
This page provides guidance for operation and maintenance (O&M) of filter strips. Filter strips are designed to filter suspended solids from runoff as water passes over the filter strip. Most filter strips are vegetated, with grass and perennial native vegetation most widely used.
Supplemental information can be found on the page called Operation and maintenance of filter strips - supplemental information. Supplemental information includes the following.
Vegetated filter strip, also known as buffer strips or buffers, are vegetated land areas between a pollutant source and a surface water body (also called a receiving water). They can be stand-alone practices or used as pretreatment to other practices like bioretention practices or wet ponds. They reduce the flow velocity of water and filter and infiltrate pollutants such as sediment from stormwater. Vegetated filter strips may be subject to high public visibility, trash loads, sedimentation, pedestrian traffic, and even vehicular traffic or loads. Vegetated filter strips can provide ecosystem services such as nutrient cycling and storage, carbon sequestration, climate adaptation, and habitat for bees, butterflies, and other insects and small animals that pollinate.
Vegetated filter strips require dedicated and regular maintenance to ensure proper and long-lasting operation, and in most cases a vegetated filter strip should be designed to be effective for at least 10 years (NRCS, 2010). The most frequently cited O&M concerns for vegetated filter strips include
The sections below describe best practices to prevent or minimize these common problems.
Designers should design these practices in ways that prevent or minimize O&M issues. Examples include the following.
Designers should consult and include any local requirements regarding green infrastructure. O&M considerations often depend on whether the practice is located on public land, private land, or in the public right of way. For example, plantings in the public right of way that conflict with any traffic safety considerations could require increased O&M, such as pruning or complete removal.
Designers should also recognize the need to perform frequent maintenance to remove trash or excess sediment, check for clogging, and if necessary perform practice cleaning. Designers can incorporate design solutions to facilitate maintenance activities. Examples include
The designer should also provide a site-specific O&M plan that includes the following.
For more design information on vegetated filter strips, link here.
Proper construction methods and sequencing play a significant role in reducing O&M problems. Some key items during the construction phase include the following.
Effective short and long-term operation of vegetated filter strips requires a dedicated and routine maintenance plan with clear guidelines, expectations, and schedules. Proper maintenance will not only increase the expected lifespan of the facility but will improve aesthetics and property value. A maintenance plan clarifying maintenance responsibilities should be required for all practices.
Some important post-construction considerations are provided below along with recommended maintenance standards.
Overview and schedule of general maintenance activities for vegetated filter strips
Link to this table
Activity | Frequency | Time period | Level of effort | O&M benefita |
---|---|---|---|---|
Inspect the level spreader for sediment buildup and the vegetation for signs of erosion, bare spots, and overall health. | At least twice after storm events 0.5 inches | Within the first 6 months | 1-2 hours | 1,5 |
Check for evidence of clogging or failing of the inlet, outlet, and bypass pipes. | At least twice after storm events 0.5 inches | Within the first 6 months | <1 hour | 1 |
Remove any stormwater diversion or barriers once seedlings are established. | Once | When plants are sufficiently established | 1-2 hours | 1,2,3,4,5 |
Supplemental watering during drier periods, particularly if keeping stormwater offline until plant seedlings are established. | 1/week initially | During first 2 months | 1-2 hours | 2,3,4,5,6 |
As needed | First growing season | 1-2 hours | 2,3,4,5,6 | |
Mow grass in surrounding area to 3-4 inches | As needed | During growing season | 1 hour | 1,2,3,4,5,6 |
Removal of sediment and debris from the toe of slope or level spreader. | Biannually | In spring and fall | 1-2 hours | 1,5 |
Reseed bare spots as needed. | As needed | First growing season | 2-4 hours | 1,2,3,4,5,6 |
Activity | Frequency | Time Period | Level of Effort per Visit | O&M Benefita |
Inspect the level spreader for sediment buildup and the vegetation for signs of erosion, bare spots, and overall health. | Annually and after storm events larger than the 10-year return period | After winter and after storm events larger than the 10-year return period | 1-2 hours | 1,5 |
Mow the grass or vegetation only if needed. Avoid mowing when the ground is wet. | As needed | During growing season | 1-2 hours | 1,2,3,4,5,6 |
Inspect for and remove excess sediment in the pre-treatment device and/or in the main treatment area. | Monthly | All year long | 4 hours if removal is needed | 1 |
Remove sediment and debris from the toe of slope or level spreader. | Biannually | In spring and fall | 1-2 hours | 1,5 |
Remove trash and debris from the pre-treatment device and/or in the main treatment area. | Monthly during rainy season | All year long. Cleaning may need to be done more frequently during the summer storm season and less during the drier winter season | 1-2 hours | 1,5 |
Mow grass in surrounding area to 3-4 inches | As needed | During growing season | 1 hour | 1,2,3,4,5,6 |
Weed and remove invasive plants | Twice during growing season | During growing season | 1-2 hours | 2,3,4,5 |
Inspect plant composition and health and replace as needed | Annually | In fall or spring | 4 hours if plant replacement is needed | 2,3,4,5,6 |
Reseed bare spots as needed. | Biannually | In spring and fall | 1-2 hours | 1,2,3,4,5,6 |
Supplemental watering during drier periods, particularly if keeping stormwater offline until plant seedlings are established. | As needed during extended dry periods | Dry periods | 1-2 hours | 2,3,4,5,6 |
Spring cleanup (cut back and remove last year’s material) | Annually | In spring | 2-4 hours | 2,3,4,5 |
Fall cleanup (removed excessive leaf litter, particularly in areas with lots of trees) | Annually | In fall | 2-4 hours | 2,3,4,5 |
Activity | Frequency | Time Period | Level of Effort per Visit | O&M Benefita |
After long term operation of the practice, some occasional and infrequent maintenance activities might be required, such as bigger repairs, soil regeneration, regrading, or redesign of key elements of the practice. | As needed | As needed | Could be significant depending on the activity | 1,2,3,4,5,6 |
Key to Maintenance Benefits:
|
Common problems and how to troubleshoot them for vegetated filter strips
Link to this table
Symptom | Possible Causes | Solution |
---|---|---|
Channelization of flow | Improper grading | Install infiltration trench or level gravel spreader trench upstream of practice |
Erosion | Improper (too steep) grading and/or plant loss | Correct for drainage and flow path issues to make sure flows are evenly distributed. Make sure the flow paths are unobstructed |
Vegetation is not able to establish | Plant selection is inappropriate for the site | Consult with a landscaper or horticulturist. Check that plants are suited to the local conditions. Make sure BMP is protected from snow storage or salt application. |
Maintenance costs will vary on a number of factors, including but not limited to the following.
Preventative maintenance is key to minimizing major costs associated with repairs. The annual cost of maintaining filter strips (mowing, weeding, inspection, litter removal, etc.) is generally between $100 and $1,400 per acre (based on 2006 cost estimate, PADEP 2006). Maintenance may be higher the first few years, while plants are being established.
Supplemental information can be found on the page called Operation and maintenance of filter strips - supplemental information. Supplemental information includes the following.
MPCA has compiled publicly available O&M resources (Excel format) related to green infrastructure. This non-exhaustive catalog is intended as a resource to practitioners.
Example O&M plans, checklists, reports, and maintenance agreements for vegetated filter strips
Link to this table
Document | Link |
---|---|
Operation and maintenance plan | O&M Plan for commercial building in Fairhaven, MA |
Construction phase inspection checklist | Fairfax County, VA |
Virginia DEQ BMP Clearinghouse | |
O&M inspection checklist | MPCA Checklist |
University of Kentucky | |
City of Roseville, CA | |
City of Durham, NC | |
O&M example report | Milwaukee Metropolitan Sewerage District (MMSD) |
Metropolitan St. Louis Sewer District (MSD) | |
Maintenance Agreements | Example Maintenance Agreement 1 |
Example Maintenance Agreement 2 | |
Example Maintenance Agreement 3 |
This page was last edited on 30 December 2022, at 13:37.