Workshop Item - Jon Haukaas, Director of Public Works
Title
Stormwater Inspection and Maintenance Programs
Executive Summary
The Minnesota Pollution Control Agency (MPCA) issues the City its Municipal Separate Storm Sewer (MS4) Permit and is the regulatory agency that sets criteria for inspection and maintenance activities. Best Practices for stormwater facilities include an annual inspection program and major maintenance on a five-year cycle.
Staff will describe the current activities conducted to meet these requirements and the potential impacts on our residents.
Background
The MPCA issues the City its MS4 permit and is the regulatory agency to which our inspections and maintenance must comply with. Under the rules of the MS4 permit, approximately 20% of pond and outfall inspections must occur each year. To track and achieve this work, the city is divided into five geographical areas. A map of MS4 areas 1-5 is attached.
Workload and Equipment
Pond inspections and the resulting maintenance needs alone typically account for over 500 man-hours annually. Staff uses a wide variety of equipment to service and maintain the pond and ditch system. The four most common are the Vac truck, Excavator, Backhoe and a Dingo mini-loader. These four pieces of equipment are used on everything from clearing a ditch to working on a residential back yard pond outfall.
Some of our pond type infrastructure has special maintenance needs. The Iron Enhanced Sand Filter (IESF) at Centennial Park and the Bio Char filter at Pleasure Creek each need to have the surface scarified 4 times a year. Staff has modified and uses a repurposed old infield ball drag for this work. During tree removal operations, a wood chipper and truck are used. A wide range of power hand tools and compaction equipment is also used. Sometimes the best piece of equipment is the common shovel.
The amount and type of infrastructure in each area is listed in the chart below.
(* indicates MS4 required inspection items.)
|
TYPE |
AREA 1 |
AREA 2 |
AREA 3 |
AREA 4 |
AREA 5 |
COUNT |
|
OUTFALL * |
69 |
112 |
24 |
90 |
13 |
308 |
|
POND * |
113 |
86 |
95 |
89 |
108 |
491 |
|
DITCH MILES |
28.89 |
17.03 |
21.44 |
21.77 |
17.36 |
106.49 |
Ditch System
The ditch system within the city limits is 106.49 miles in total length. There are two major classifications of ditches in Minnesota. The first, Jurisdictional Ditches, are the responsibility of Watershed Districts. Within the City of Blaine these are the Coon Creek Watershed District (CCWD) or the Rice Creek Watershed District (RCWD). Non-Jurisdictional Ditches are labeled as ‘private’ and become the local responsibility and maintained primarily by the City of Blaine. The City of Blaine is responsible for only the private ditches within its jurisdiction that take on drainage from public areas such as our street system. As the Local Government Unit (LGU), the City is responsible to ensure these private ditches keep functioning properly. There are approximately 47 miles of private ditch in the City system. In most but not all cases, the City has drainage and utility easements over these private ditches.
The remaining approximate 60 miles of ditch system is split between Coon Creek and Rice Creek watershed districts. The Coon Creek and Rice Creek watershed districts perform inspections of their ditches and generate a “Ditch Inspection Report” (DIR). The DIR within an area encompasses all ditches, both private (the city’s) and jurisdictional (the watersheds) ditches. This report provides recommendations for what and where maintenance is needed within a particular ditch system. Typical issues found are obstructions, fallen trees, trash and debris, perched outfalls, sand buildup in deltas, and erosion.
|
TYPE |
AREA 1 |
AREA 2 |
AREA 3 |
AREA 4 |
AREA 5 |
MILES |
|
Total Ditch Miles |
28.89 |
17.03 |
21.44 |
21.77 |
17.36 |
106.49 |
|
City (Private) |
15.50 |
6.40 |
6.86 |
10.74 |
7.72 |
47.22 |
|
CCWD/RCWD |
13.39 |
10.63 |
14.58 |
11.03 |
9.64 |
59.27 |
Pond Network
The five MS4 Maintenance Areas are also used for the Pond Inspection and Maintenance program work. Below is a chart that shows the current number of ponds in each area that are inspected on the 5-year rotating schedule. The city expects area 3 and area 4 to have a 20% increase in ponds over the 20 years due to residential and commercial development.
Common issues found during the inspection process include; leaning trees, tree and brush growth on outfalls, sand deltas, plugged inlets/outlets and trash removal.
Structural Treatment Device and Outfall System
Structural Treatment Devices are facilities that capture sediment or other contaminants for mechanical removal from the system. These can be as simple as a pond skimmer that capture floating debris and garbage or more complex capture devices like sump pits, or offline filters.
Flared End Sections (FES) are the point where the City’s network of underground stormwater pipes, ditches, and ponds connect to one another. An FES can be on the inlet/upstream or outlet/downstream end of a reach. These are the most common points for blockages to occur and so extra effort is made to regularly inspect and maintain these sites.
Inspection Programs and Work Order Creation
In addition to the Ditch Inspection Reports generated by our Watershed District partners, Public Works Sewer-Storm Division employees conduct the inspections of storm water treatment devices and facilities located in the pond and ditch systems.
Inspections of ponds and ditches includes:
• Inlets
• Outlets
• Outfalls / Flared End Sections
• Pollution Control Devices if present
• Embankments and slope for concerns such as:
1) Erosion
2) Sand deltas
3) Encroachments:
• Fences, Sheds, Docks, Landscaping, Retaining Walls
• Vegetation
1) Type (tree, brush, vegetation)
2) Coverage/covered - percent of perimeter (%)
Identification of Work Order Actions
In order to maintain a body of water; 50% access is a minimum requirement size for equipment needed to perform the maintenance. Work Orders to initiate mowing or clearing around ponds are based on staff’s ability to access the site and thereby provide the required level of maintenance:
Ponds:
• Over 50% clear of trees and brush (clear of Encroachments) - No Action need at this time
• Under 50% clear (unable to access most of the perimeter) - Action Required (High, Medium, and Low priority) Service Requests will be generated.
Examples that would require action are as follows:
§ Trees/brush leaning over pond or ditch
§ Flow impediment or restrictions
§ Trees/brush leaning over fences (encroaching adjacent property lines)
§ Dead fall that has entered the pond or ditch
§ Type and/or condition of trees invasive species present.
Flared End Section:
• Clear/free of obstructions - No Action needed
• Has obstructions - Action Required (High, Medium, and Low priority), Service Requests will be generated.
Examples as follows:
§ Tree growth in or close proximity (within 15 ft) of Flared End sections
§ Brushy growth restricting flow and visibility
§ Abundant amount of Cattail/vegetation growth
§ Buildup of sedimentation delta
Pollution Control Devices: Overflow/Skimmer/Weir/RipRap:
• Clear/free of obstructions -No Action needed
• Has obstructions - Action Required (High, Medium, and Low priority) Service Requests will be generated.
Examples as follows:
§ Tree growth in or close proximity (within 15 ft)
§ Brushy growth restricting flow and visibility
§ Abundant amount of Cattail/vegetation growth
§ Buildup of sedimentation at the outflow
§ Fences
Encroachments
§ Applies to Commercial and Residential properties
§ Action Required every time
Examples are but not limited to:
• Docks
• Fences
• Sheds
• Landscaping and gardens
• Fire pits
• Retaining Walls
Maintenance Activities
The current Best Practice is to use the city’s forestry equipment to remove all trees, brush, and vegetation that would obstruct any maintenance of the city’s ponds and ditches. This practice helps to maintain pond volumes, improve the filtering ability of the wetlands, and allows the intricate ditch system to flow properly. Furthermore, this practice of maintenance allows for our larger heavy equipment to reach the water’s edge for maintenance and/or in the event an emergency arises.
Using the Ditch Inspection Report, the Sewer-Storm crew and the ICWC service crew staff have been preforming bench side ditch clearing efforts throughout the city’s 47 miles of ditches. For the past several years, a focused effort has been made to clear the ditches of trees, brush, and vegetation. Past inspections noted a significant amount of large older trees leaning heavily over the ditch channel and other dead trees that had fallen into the channel causing obstructions. These trees and dead branches that have fallen and/or broken off by wind end up plugging culverts which restricts the flow of the storm water. This also causes a buildup of phosphorous levels in the water from decaying leaves which has resulted in many channels to be classified by the MPCA as having impaired water status.
The cooperation between the City and the watershed districts is now making it much easier for city crews to work on private and watershed ditch systems that run through or adjacent to City-owned park or institutional properties. Ditch work over the last few years has significantly reduced the number of emergency response types of maintenance activities related to obstructions and the resultant flooding.
Outreach and Communication
Staff is working to develop a better outreach program to better explain and notify residents of the need to maintain the buffer area around these ponds. The work includes removal of woody vegetation, mowing to manage invasive plants, tree removals, trash removal, and excavation of accumulated sediment.
Upon completion of the inspection activities, a report is generated from the Data Acquisition Software which lists the work needed in any given area in any given year. This report, with a written summary from the Sewer-Storm Supervisor, will then be reviewed by the Deputy Director of Public Works, Engineering, Water Resources, and Communications. They in turn will formulate a public outreach and notification plan in advance of Public Works staff conducting the work outlined in the summary.
The Goal of an improved communication plan is to:
1 Facilitate maintenance in a timely and cost-effective manor
2 Alleviate residential misconceptions
1. Land ownership and rights
2. Drainage and utility easements
3. Sediment pond verses wetland
4. Not all trees are the same
3 Quantify the City liability
1. How much buffer clearing needs to be done
2. Extent of resources needed to complete the clearing
3. Educational materials
4. Advanced notifications
Typical Timelines:
Janurary 1st to March 15th Field inspections and data collections
March 15th to March 21st Supervisor writes summary of work needed and sends report.
March 22nd to May 1st Engineering, Water Resources and Communications review report and commit to an action plan approved by May 1 and make first contact with the residents.
May 1st to July 1st Community Outreach and Notification
July 5th Notice to proceed is given to Public works to start field operations. Field operations will continue to the end of the year.
Strategic Plan Relationship
This project meets the Well-Maintained Infrastructure strategic plan priority.
Board/Commission Review
N/A.
Financial Impact
This work is included in the annual Maintenance and Operations budget in the Stormwater Enterprise Fund.
Public Outreach/Input
The MS4 Permit includes requirements for Public Education and Outreach. Additionally, notices are sent to adjacent property owners in advance of major maintenance work such as brush removal and pond excavation.
Staff Recommendation
Staff is asking for feedback from the City Council on the program.
Attachment List
1) City Council Approval of the Storm Water Pollution Prevention Plan
2) Map of Stormwater Inspection Areas
3) Map of Ditch System
4) Map of Pond System