At their Old Middleton Rd construction site, Rawson Construction has had numerous problems. Now, failure to filter runoff flowing into a box culvert will cause additional, unnecessary work.
This is the sole exit for stormwater from a large basin. Rawson neglected to filter stormwater entering this box culvert during recent heavy rains of over 2 inches.
The area around the culvert construction, especially its sides, are heavily disturbed. The only protection between this culvert and Lake Mendota, half a mile away, is one gravel dam. It's quite porous, allowing fine sediment to pass.
During recent storms, a layer of fine sediment 1-2 inches deep was deposited in the culvert.
This sediment will have to be removed before the next rain. Otherwise, it will fill the pool above the gravel dam, and/or pass through the pores in the gravel dam.
If it's not cleaned out before the gravel dam is removed at the end of the project, then obviously it will flush to Lake Mendota in subsequent storms.
There's a significant amount of sediment here. I made a rough estimate--the box culvert now contains from 1/5 to 2/5 of a dump truck of sediment.*
This error could have been avoided if the sides of the pit had been better protected, and if the clear water coming from the creek above had been channeled directly into the culvert (before it picked up sediment).
The bottom line: Poor erosion control can result in costly delays and remedial work.
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Who is responsible for this site
Design Engineer: Lisa Coleman, 266-4093, City Engineering, lcoleman@cityofmadison.com
Construction Engineer: John Fahrney, City Engineering, jfahrney@cityofmadison.com Contractor: Rawson Contractors, Kenneth Servi, President, kservi@rawsoncontractors.com http://www.rawsoncontractors.com/
Permit authority: Tim Troester, (608) 267-1995, ttroester@cityofmadison.com
Erosion Control Permittee: Signed by Robert Phillips, delegated to John Fahrney, City Engineering,(608) 266-9091, jfahrney@cityofmadison.com
Grantor of permit for construction of ponds: DNR Water Management Specialist Cami Peterson, 608-275-3208. No mention was made in the permit of the need to deflect runoff from the ponds under construction.
* Calculations: The culvert is 94' long and 12' wide. The mud inside was estimated at 1-2" deep. A dump truck contains 16 cubic yards.
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