[0:01] [Music] [0:06] hi I'm Jeff Dunn with the Vermillion [0:08] River Wershed today we're in Foxboro [0:11] Park west of Cedar and north of Dodd the [0:14] north creek of the Vermillion River [0:16] bisects through this park when the park [0:19] was developed and the land was developed [0:21] in the late '7s there was little if any [0:24] regard or consideration giving to storm [0:27] water runoff around the same time in [0:29] 1979 the state of Minnesota enacted [0:32] legislation for storm water management [0:36] for new development from houses [0:39] driveways streets from areas that were [0:42] undeveloped before that all that [0:44] impervious area created a lot more [0:46] runoff and it caused flooding problems [0:49] it caused bank erosion along the creeks [0:52] stirred up a lot of sediment the city of [0:54] Lakeville started looking at how they [0:57] could retrofit one of these ponds into [0:59] an into the urban landscape and they [1:03] found that Foxboro Park was an ideal [1:05] candidate the city of Lakeville along [1:08] with the Vermillion River Wershed [1:10] submitted for a clean water grant the [1:13] city was awarded [1:15] $350,000 to construct the retrofit or to [1:18] construct the pump the city also [1:20] contributed as well as the Vermillion [1:22] River wershed and Dakota counties let's [1:25] go take a look at the pond and we'll [1:28] talk about some of the components of the [1:30] pond and how they work together to [1:33] manage storm water [1:37] so coming down from the subdivision [1:40] above us is that 220 acres that used to [1:43] drain through the pipe system that's [1:46] underneath my feet and then it would [1:48] discharge about 200 yd down into the [1:52] trees directly into North Creek and it [1:55] was not treated uh they didn't do any [1:57] detention to try to regulate those storm [2:00] water flows so that's kind of what [2:02] started the flooding uh downstream and [2:04] and those issues and the sediment [2:07] loading into the creek this is a [2:09] diversion manhole we dropped this [2:11] manhole over that existing pipe that [2:13] went out that way and then we channeled [2:16] the flows with a pipe directly into the [2:20] pond that was built last year now if the [2:23] water becomes too much flow to get into [2:25] the pond it comes right out of this [2:27] great assembly and goes down to the [2:30] creek like it used to do what you try to [2:32] target is about that 2-year storm for [2:36] water quality treatment and flood [2:38] control because that particular storm [2:41] the ones that happen frequently during [2:44] the summer and the summer afternoons you [2:47] want to try to treat that water to get [2:49] the sediment removal and to do other [2:51] things with it to improve the water [2:53] quality at this location where this pipe [2:55] is is where the water from upstream [2:58] empties into the pond this where the wet [3:00] area is is called a sediment for bay or [3:03] a settling basin and it's designed to [3:06] hold back the storm water so that the [3:09] heavy particullet can settle out of the [3:12] water column if you slow the water down [3:15] then they then the water doesn't have [3:17] enough energy and enough velocity to [3:20] keep carrying the the particles that we [3:23] want to remove from the water column so [3:25] those bigger particles of sediment [3:28] settle out in this big forbay over time [3:31] this cell will dry out because the water [3:34] will either evaporate and in some cases [3:37] it will seep into the ground the we're [3:40] estimating that every year you get about [3:43] 19 tons of sediment that would be about [3:47] two dump truck loads of sediment so [3:50] thinking about how we do our snow [3:53] plowing operations and our deicing and [3:56] winter operations it's it's a good [3:58] testament to how much of that sediment [4:01] that they might be putting down on the [4:03] roadways in order to uh make streets [4:05] safe for driving we're getting rid of it [4:08] a lot of a lot of it here over time that [4:10] sediment will build up and public works [4:14] does a good job um keeping these ponds [4:17] clean for the citizens of Lakeville and [4:20] if you don't keep an eye on the pond and [4:23] do the proper maintenance then it's not [4:25] going to function and in the long run [4:28] it's going to cost more to make things [4:30] right than it would be keeping these [4:32] things maintained frequently and [4:34] monitored this cell the sediment for bay [4:38] also traps a lot of floatables and that [4:41] includes styrofoam plastics pieces of [4:44] wood those are all the types of things [4:47] we'd like to remove from the water [4:49] before we discharge it into North Creek [4:51] so that's another big component of that [4:53] sediment for bay so what I'm standing on [4:56] here is a rock crib um this is basically [4:59] just chain link material and then this [5:03] is rounded river rock here um what this [5:07] does is it provides a barrier between [5:10] this cell which traps a lot of the heavy [5:12] particullet and the trash into another [5:16] portion of the treatment train this sand [5:18] filter bed this provides more or less a [5:21] polishing effect on the storm water [5:24] runoff before it gets to the creek [5:26] itself and so what this does is this [5:29] material is is rather porous um so over [5:34] time water should drain from the [5:38] sediment for bay through this rock [5:40] structure and into the u sand filter bed [5:44] area so now I'm standing in the sand [5:47] filter cell this area has been excavated [5:50] and filled with sand [5:53] underneath it is a network of pipe that [5:57] is [5:57] perforated so this perforated pipe will [6:00] act as an under drain beneath the sand [6:03] bed so that when water flows on top of [6:06] this sandy material it seeps through the [6:09] pore space in the sand and then it's [6:11] filtered out it's discharged through [6:14] this piping system we just call these [6:16] risers these are access points for [6:19] maintenance crews so that they can get [6:21] down into these pipes that are laid down [6:23] along the ground and take a look at them [6:25] make sure they're functioning correctly [6:27] with public works with the city they [6:30] really stay on top of this stuff to make [6:32] sure it's functioning so that we don't [6:34] have to come back and use taxpayer money [6:36] to get things fixed that we could have [6:38] probably figured out beforehand now fun [6:41] fact for this particular pond is that [6:45] it's got enough volume in it to store [6:49] water from three Olympic size swimming [6:52] pools that's a lot of water that can be [6:54] stored in here um and treated and also [6:58] take the edge off those flows so that [7:00] we're not discharging so much in such a [7:03] short period of time so this structure [7:06] is the overflow structure from the pond [7:09] if we get too much water into the pond [7:12] we don't want the embankments on the [7:14] pond to be breached and so this great [7:17] assembly has the capacity to take all [7:20] that water in and down to North Creek [7:23] the rock that you see around it uh [7:27] that's just to prevent erosion and scour [7:30] around the assembly this is basically [7:33] the top of the burm there's a little [7:36] short depression in here that you can't [7:38] see from the grass but that is the [7:40] emergency overflow in case this becomes [7:44] clogged with debris or what have you [7:46] then the water can simply go over the [7:48] top and down to the creek looking down [7:51] into North Creek is where the retrofit [7:54] or the pond discharges into the creek so [7:57] we'll end our discussion today talking [7:58] about the pond let's revisit some of the [8:02] benefits that we're achieving here we [8:04] came in and we built this pond to [8:07] provide two things we wanted to enhance [8:10] the water quality by removing the [8:12] sediment that would have entered the [8:14] stream unchecked making North Creek [8:17] probably a little cloudier and more [8:18] pollutants in it and then also we're [8:21] providing uh a means to mitigate [8:24] flooding and flooding issues downstream [8:28] that include bank erosion and habitat [8:32] loss these things are are the primary [8:35] drivers why we come in and retrofit [8:38] these types of of facilities you can see [8:41] where we are with our projects and what [8:42] we've done if you visit our website [8:44] permillion riverwwaterhed.org [8:48] [Music]