2020-01-22 CC Packet - Laserfiche WebLink

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very well in town and replacement of their filtering media may have no effect on percolation. Some of the storm water ponds have been measured during winter to determine the amount of sedimentation. The ponds that have been measured have not shown any significant change in depth or storage capacity. Municipal Separate Storm Sewer System (MS4) rules indicate a pond is non-functioning if it is below 50% of design capacity. None of our measured ponds are below that level. Even when they are below 50%, the regulations don't require any specific maintenance. Mr. Palzer doesn't believe we should perform much if any maintenance on ponds that are above 70% remaining capacity. It is difficult to determine when city ditches, which don't really have a good definition, need to be dredged or deepened. We did a small dredging job this year with Olson's Sewer Service. The length of the project was 140 feet and the bid was $4,912. That works out to about $35 per foot. That bid was about half of the other bid received, so the cost may not be representative for other projects. Staff has used a price of $40 per foot for estimating ditch maintenance costs. Rain gardens will likely fill up their media with sediment sometime, but we don't have a great handle on how long that happens on average. Since the percolation has been very poor in the rain gardens that have been installed, it may not make sense to reconstruct them. It is staff s understanding that rain gardens will not be required in the future, so we have not budgeted to replace the existing ones. The legal standard regarding when we need to test sediment removed from these water features is when 3,000 cubic yards of material are removed. The testing is to determine if Polycyclic Aromatic Hydrocarbons (PAHs) primarily from coal tar based driveway sealers are present. It is staff s intention to remove less that that amount annually to avoid the necessity of testing. Staff estimates a cost of $2,000 as an average to remove sediment from the inlet and outlet of each pond. We plan to do maintenance to each of the 84 public ponds during a 10 year period. That leads us to a total of $168,000 for all ponds or $16,800 per year. Staff would plan to start a regular pond maintenance program in 2021. Staff estimates a cost of $40 per foot as an average to remove sediment from ditches. We plan to do maintenance to each of the 14 ditches during a 10 year period. That leads us to a total of $277,400 for all ditches or $27,740 per year. Staff would plan to start a regular pond maintenance program in 2021. These assumptions are predicated on not having to completely reconstruct any storm water feature. The standard rule of thumb for a minimum cash balance in an enterprise fund is something between three to six months of operating expenses in reserve. The estimated annual operating expenditures of the fund starting in 2021 are around $90,000. Holding three months of expenses in reserves means $22,500 should be kept for cash flow