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Maintenance of Stormwater BMPs: Frequency, effort, and cost

November-December 2008 issue, The Stormwater Newsletter
By Joo-Hyon Kang, Peter T. Weiss, John S Gulliver, Bruce C. Wilson

Although many resources are available to aid in the design and construction of most structural stormwater best management practices (BMPs), few guides exist pertaining to their operation and maintenance. Historically, it seems as though a “build ’em and walk” approach has been commonplace. However, increasing focus upon mass balances, numeric goal setting, and total maximum daily loads (TMDLs) now requires that much more emphasis be placed upon BMP operation and maintenance for permitting and reporting requirements—for example, for the National Pollutant Discharge Elimination System (NPDES) municipal separate storm sewer system (MS4) permit program, and as a part of stormwater pollution prevention plan (SWPPP) reporting.

Typically, we think of structural stormwater BMP operation for optimizing (1) the removal of pollutants and (2) the reduction of runoff volumes/rates via the management of stormwater networks or treatment trains. BMP maintenance is the purposeful management of a BMP to maintain a desired level of performance and efficiency. Maintenance consists of short-term (routine or more frequent), long-term (non-routine or less frequent), and major (rare) actions (Figure 1).

Stormwater BMPs have a lifecycle from their creation (design and construction) through operative stages (functional or not) that is largely dictated by operation and maintenance (O&M) actions. As maintenance involves a significant amount of resources (personnel, equipment, materials, sediment disposal expense, etc.), the more we learn about BMP operation, the more likely we are to maintain optimal performance and improve cost efficiencies. The purpose of this article is to advance short- and long-term maintenance considerations to develop more realistic O&M plans. To do this, we have used a combination of a national literature search for maintenance costs coupled with a detailed municipal public works survey.

Minnesota BMP Maintenance Survey
The statewide survey of Minnesota Municipal Public Works managers to define maintenance needs and guidelines was conducted by the University of Minnesota and partly funded by the Minnesota Pollution Control Agency. Previously, the University of Minnesota produced a manual, Assessment and Maintenance of Stormwater Best Management Practices, which includes source reduction and four levels of assessment (from visual to state-of-the-art monitoring). The manual is available online at www.pca.state.mn.us/water/stormwater/stormwater-research.html or wrc.umn.edu/outreach/stormwater/bmpassessment/index.html.

The specific goals of the survey were to identify and inventory stormwater BMP maintenance in Minnesota. Survey questionnaires focusing on the following questions were sent to 106 cities; we received 27 responses, for a slightly higher than 25% response rate.

How many BMPs are in your watershed?
How often are your BMPs inspected?
What is the average staff-hours spent per routine inspection/maintenance?
How complex is the maintenance of your BMPs?
Which factors most frequently cause the performance deterioration of your BMPs?
What are the costs for non-routine maintenance activities?

We attempted to make the survey as simple as possible, requesting information for typical response ranges of common BMPs. Although the number of respondents was relatively low, we believe that the results will help refine operation and maintenance needs.

Inspection Frequency and Staff-Hours. The required frequency of stormwater BMP maintenance actions and the associated required staff-hours are two key parameters that are necessary to reasonably budget and schedule inspection and maintenance. Frequency and staff-hours vary according to BMP design, climate conditions, accessibility of the BMP, and maintenance strategies of the BMP operators. As part of the survey, cities were asked to provide information regarding their frequency of routine maintenance actions for various kinds of BMPs.
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Fernley Developers Targeted by Canal Proposal

KOLO TV-8
September 5, 2008

FERNLEY, Nev. (AP) - Developers would face new requirements if they build homes or commercial buildings near the aging Truckee Canal in Fernley under a proposal being considered by the Truckee-Carson Irrigation District.

The district board wants to require developers to install an impermeable barrier in any section of the Truckee Canal above new development.

Dave Overvold, TCID project manager, said the barrier would be a vertical concrete wall on the canal's north bank.

A Jan. 5 breach of the canal flooded about 600 Fernley homes. The 31-mile canal, operated and maintained by the irrigation district, sends water from the Truckee River to Fallon-area farmers.

Currently, developers building homes north and downhill of the Truckee Canal are required to widen the canal bank.

Fernley City Councilman Cal Eilrich, former president of the Fernley Builders Association, said he agrees the canal needs to be reinforced, but sees it as more of a public works project than an irrigation district project. He noted that some of worst damage from the January flood occurred a half-mile downstream from the canal breech, and that a concrete wall upstream wouldn't have helped unless it extended the entire length of the canal through Fernley.

"This is an issue that affects all citizens who live in Fernley," said Eilrich, who stressed he was speaking only as a former developer.

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Builders have stricter requirements under Truckee Canal plan

ASSOCIATED PRESS • September 6, 2008
Developers would face new requirements if they build homes or commercial buildings near the aging Truckee Canal in Fernley under a proposal being considered by the Truckee-Carson Irrigation District.

The district board wants to require developers to install an impermeable barrier in any section of the Truckee Canal above new development. Dave Overvold, TCID project manager, said the barrier would be a vertical concrete wall on the canal's north bank.

A Jan. 5 breach of the canal flooded about 600 Fernley homes. The 31-mile canal, operated and maintained by the irrigation district, sends water from the Truckee River to Fallon-area farmers. Currently, developers building homes north and downhill of the Truckee Canal are required to widen the canal bank.

Fernley City Councilman Cal Eilrich, former president of the Fernley Builders Association, said he agrees the canal needs to be reinforced, but sees it as more of a public works project than an irrigation district project. He noted that some of worst damage from the January flood occurred a half-mile downstream from the canal breech, and that a concrete wall upstream wouldn't have helped unless it extended the entire length of the canal through Fernley.

"This is an issue that affects all citizens who live in Fernley," said Eilrich, who stressed he was speaking only as a former developer.

"If a future developer comes in and builds next to the canal, he should be made to pay some amount of money to offset the costs (of building the concrete wall)," Eilrich told the Lahontan Valley News and Fallon Eagle Standard newspaper. Eilrich also noted residential development has essentially stalled in Fernley due to the real estate downturn and it could be another five years before a big development breaks ground.

Martis Dam risks still being studied

Remote control gates priority for flood control
Source: Greyson Howard, North Lake Tahoe Bonanza
February 17, 2008

Field work has temporarily halted on the Martis Dam until the snow melts, but the Army Corps of Engineers is still working to assess the risk the dam poses.

Located three miles east of Truckee in the Martis Valley, the 36-year-old earthen-fill dam has been categorized as an "extremely high risk" by the Corps for seepage issues.

Geologists blame the coarse glacial soil for the seepage that could destabilize the dam, making it one of the six riskiest dams in the nation.

The dam's ranking comes not only from the probability of failure, but also the consequences downstream, which in this case is the flooding of the Truckee River Canyon and a large part of Reno, said Ronn Rose with the Dam Safety Assurance Program last fall.

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