Mile high Business Center Pond maintenance

 With the water removed there was approximately 8” of mud and debris in the outfall’s main chamber. This is the one basin where we were not able to remove all the cattails.  

 The point where three concrete channels converge and discharge into the pond as been underwater with sediment flows coming into the channel that the rip-rap was between the channels was buried and approximately 3 inches of soils and grasses were standing on top of the curb of the concrete channel. As the work was tangential cleaning the channel our crew dug out the rip rap and reset it while cleaning the channel curb. 

With the brush and trees removed from the small velocity control pad and concrete channel located next to 45th Ave. we observed that water had been overflowing the rip rap on the south side of the pad.  This has been contributing to soil erosion.  We were able to move the rip rap along the outfall pipe that will allow excess flow to leave over the top of the berm directly into the channel. 

Once leaf and other debris were moved from the area around the berm a large eroded area was exposed.  The crews were able to move the existing rock to create a better flow pattern.  Additional rocks was gathered from the site and the eroded area was filled to create a reinforced channel.

 This is the one basin where we were not able to remove all the cattails due to standing water.

 With the water removed there was approximately 15” of mud and debris in the outfall’s main chamber. 

 The berm at the end of the main concrete channel was significantly trapping water in the concrete channel.  Yellow line is channel showing debris backed-up for 25+ feet.  

Blue Arrow is point rocks were moved to allow water to flow into the pond.  This contributed to excess soils in this channel and on top of the channel curb.  

Overhead shot shows end of channel rocks displaced to allow water more directly to flow past end of channel.

This should allow flows to enter pond and reduce sediment dropping out of storm flows. 

 One of the additional items included with  the fall proposal was to address the point where water was leaving the large velocity control pad on the South end. While this work was planned, the brush and debris did not allow us to see the full extent of the issue. Once the brush and leaves were removed a larger than expected eroded area was exposed. 

Note 1 indicates outlet to channel.

note 2 indicates where water leaving the structure.

This issue was resolved by moving rocks within the berm to create a channel to allow water to directly discharge into the concrete trickle channel. Once the berm had been adjusted to direct the overflow directly into the concrete channel the eroded area was back-filled with material taken from the channel.  

 With the water removed there was approximately 6” of mud and debris in the outfall’s main chamber. 

 This out-fall channel extended some 36" further into the pond area than expected.  Green line is water level in spring.

Blue line is water level in December.

Red line is the end of the concrete structure. 

Photo of our staff clearing cattails and brush. 

The gray rock represents area regraded and lined with rip rap to prevent overflow from pad continuing to erode soils and contribute to sedimentation in the pond.

For this structure we were able to move existing rock to encourage the overflow to exit directly into the concrete channel (green arrow) instead of eroding an area between the two channels (Blue Arrow).

The orange arrow is the Slope drain rebuilt after installation of a new concrete drain pan in parking lot.  

Note that the Earth X employee in the previous picture is standing slightly right of center behind the small trees. 

Overhead post work.  Note cattail root mass in water indicates  36" of infill sedimentation since the pond was completed in 2007.