[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]