Adopt Resolution #20-214 Accepting Quotes and Awarding Contract for 5751 164th Lane Drainage Improvements, Improvement Project #19-17

Purpose:
The purpose of this case is to adopt Resolution #20-214 accepting the quote of and awarding a construction contract to Dryden Excavating, Inc. for 5751 164th Lane Drainage Improvements, Improvement Project #19-17. 

Background:
The property owner at 5751 164th Lane first contacted Staff regarding drainage concerns on May 11, 2019.  According to the property owner, stormwater runoff from the drainage ditch in City right-of-way in front of their house has been flowing directly across their property in a shallow swale for decades without any drainage easements in place.  The property owner claimed that during the winter of 2018/19 the outer edge of the 14-foot by 16-foot floating concrete slab supporting their attached enclosed patio, which is directly adjacent to the drainage swale running across their property, lifted approximately 6-inches.
 
Staff has not been provided with any evidence that the lifting of the slab actually occurred that winter, such as before and after pictures, but the lifting of concrete slabs can occur if the soils underneath a slab are wet and are subjected to numerous freeze-thaw cycles. 
 
After the property owner contacted Staff with their concerns, Staff began working to develop plans to route the stormwater runoff generated and conveyed within public right-of-ways through drainage ditches and storm sewer culverts located within existing City right-of-way and drainage easements, instead of through a swale on private property that is not encumbered by a public drainage easement as currently occurs.
 
After collecting topographical survey and working with private utilities, including Northern Natural Gas who owns and operates two high pressure gas lines that traverse the private property, as well as City right-of-way including the ditches, Staff completed plans and recommends constructing the improvements this fall to help ensure no further claims of damage to private property will be received in the future. 
 
Existing drainage infrastructure includes a culvert crossing under 164th Lane located just west of the driveway to 5751 164th Lane.  Runoff from the south side of 164^th Lane flows though this culvert to the drainage ditch north of 164^th Lane and adjacent to 5751 164th Lane.  Then once the stormwater runoff reaches a certain elevation it starts flowing through the swale on the private property as previously noted.
 
The attached plans show the proposed drainage improvements involve re-grading the ditch on the south side of 164th Lane, replacing the existing driveway culvert at 5800 164th Lane with a new culvert at a lower elevation, and adding a new culvert under 164th Lane at the western lot line of 5751 164th Lane where a drainage and utility easement currently exists and is the intended route for conveying stormwater runoff from this stretch of 164th Lane to the pond to the north.
 
Northern Natural Gas owns two high pressure gas mains that are contained within a 50’ wide easement which diagonally crosses 5751 164^th Lane.  Staff worked with Northern Natural Gas while designing the plans to avoid conflicts with the gas mains.  Northern Natural Gas approved the plans prepared by Staff with some contingencies, which have been built into the plans.
 
When meeting with the property owner on February 13, 2020, the owner requested that the City pay to repair their damaged patio, which they claim occurred as a result of stormwater runoff flowing through the swale.  On May 4, 2020, a claim was filed by the City with the League of Minnesota Cites Insurance Trust.  It is Staff’s understanding that LMCIT has since denied the property owner’s claim, and that the property owner is appealing their decision.  These drainage improvements are proposed to be completed in 2020 to help avoid future damage claims by the property owner.
 
Staff estimated construction costs for this project at $22,000 based on the attached plans.  On August 25, 2020, the City Council authorized Staff to solicit quotes for this work. Staff submitted Requests for Quotes to three local contractors.  Two of the contractors indicated they were too busy to complete the work this year.  Only one contractor, Dryden Excavating, Inc., submitted a quote, which was in the amount of $22,827.78.  Staff believes this is a reasonable quote and recommends that the City accept it and construct the improvements in 2020.
 
City Staff will administer and inspect construction of these improvements.
 
Construction staking is proposed to be provided by Bolton & Menk at a cost not-to-exceed $1,000.
 
Project costs are proposed to be funded using a combination of Stormwater Management and Stormwater Utility Funds.  
 
Once the contractor begins work, the improvements are anticipated to take 5 to 10 days to complete, with completion specified by October 23, 2020.  Final payment will be issued in 2021 after turf is established and all work is approved.   

Staff Recommendations
Staff recommends adopting Resolution #20-214 accepting the quote of and awarding a construction contract to Dryden Excavating, Inc. in the amount of $22,827.78 for 5751 164th Lane Drainage Improvements, Improvement Project #19-17, and authorizing Bolton & Menk to stake construction at a cost not-to-exceed $1,000. 
 
Public Works Committee Recommendations
On August 18, 2020, the Public Works Committee unanimously recommended City Council authorization to solicit Requests for Quotes for 5751 164th Lane Drainage Improvements, Improvement Project #19-17.
 
The Committee also asked if Staff had explored the option of grading a berm between the front yard and the back of the drainage ditch at 5751 164th Lane to prevent stormwater runoff from leaving the ditch and draining across this property via the swale.  Staff indicated they did not believe such work could be completed within the existing right-of-way and drainage easement, but that they would review this option and report their findings back to the Committee on September 15th.  Below is a summary of the design options Staff explored, including Staff’s findings and recommendations for each.
 
Option 1:
Grade a berm north of 164^th Lane at back edge of drainage ditch
This option, which was explored at the request of the Public Works Committee, involves construction an earth berm at the back edge of the drainage ditch within City right-of-way (ROW) between the driveway and the high point in the ditch to the west. The controlling factors are the high point in the ditch approximately 40 feet west (875.1) and the edge of the driveway 25 feet to the east (875.6). The berm would be built with a top elevation of (875.1).  The existing culverts under 164^th Lane and the driveway at 5751 164th Lane are slightly buried with flow-line elevations around 874.2.
 
Findings/Recommendations - In heavy storm events, an area of the ditch approximately 65-feet by 15-feet would fill with water to a depth of 0.9-feet (11-inches) and runoff could still overtop the berm and flow through the yard.  During spring thaws this water is likely to freeze.
Staff does not recommended this option.
 
Option 2:
Re-grade ditch and build berm within ROW north of 164^th Lane
This was the preferred option, however, after potholing the two Northern Natural Gas (NNG) pipes only 3 feet of cover was observed. By law, a minimum of 3 feet of cover is required over these pipes. To re-grade the ditch would require approximately 1-foot of cut over the eastern NNG pipe resulting in 2 feet of cover, which by law is not enough cover and would require the pipe(s) to be lowered or relocated.
 
Findings/Recommendations – Lowering/relocating NNG pipes would not be cost-effective.  Staff does not recommended this option.
 
Option 3:
Re-grade ditch south of 164^th Lane, build berm within ROW north of 164^th Lane, replace driveway culvert at 5800 164^th Lane, and add culvert under 164^th Lane
This option is depicted in the attached plans and includes filling in the mouth of the swale at the back edge of ROW north of 164^th Lane. The south invert of the existing 164^th Lane culvert (874.5) will control the depth of water standing in the lowest area of the ditch west of the driveway at 5751 164^th Lane.  The standing water depth will therefore be 0.3-feet or 4-inches, which will disappear in less than 2 days due to evaporation and infiltration allowing the ditch to be regularly maintained.  
 
Findings/Recommendations – This design directs all stormwater runoff south of 164^th Lane through the re-graded ditches and new culvert under 164^th Lane to the existing drainage easement and swale along the west property line of 5751 164th Lane.  The ditch north of 164^th Lane will now only receive runoff from one lane of 164^th Lane, and given there is 7-inches of storage in the low area of the ditch, the risk of runoff entering the swale that runs across the private property is negligible.  However, if runoff does overtop the ditch it will run through the existing swale in the yard since this project only proposes to fill the mouth of the swale, though this would only occur during very large rain events or a significant snow melt event.  The swale would therefore act as an emergency overflow only.
Staff recommends this option.  
 
On September 15, 2020, the Public Works Committee reviewed the quote submitted by Dryden Excavating, Inc. and unanimously recommended that the City Council accept the quote and award a construction contract to Dryden Excavating, Inc. in the amount of $22,827.78 for 5751 164th Lane Drainage Improvements, Improvement Project #19-17, and to authorize Bolton & Menk to stake construction at a cost not-to-exceed $1,000. 

Adopt Resolution #20-214 accepting the quote of and awarding a construction contract to Dryden Excavating, Inc. in the amount of $22,827.78 for 5751 164th Lane Drainage Improvements, Improvement Project #19-17, and authorizing Bolton & Menk to stake construction at a cost not-to-exceed $750.