View All Posts

Nov 19

Phosphorus Filter is Here!!!

Posted on November 19, 2019 at 4:19 PM by Ryan Hiniker

Drainage update 11/19/2019


Upcoming Drainage Hearings or Meetings:

  • No upcoming hearings or meetings.                                                                                                           

Project Updates:


  • CD48 (Cambria Twp.)  Checklist items still remain after harvest is completed and things dry up.  Mostly grading and in-take maintenance remaining, some televising also needs to be completed before the project is accepted officially.
  • JD09 (Le Ray Twp.)  The north portion of this improvement project still needs to be televised, but all of the southern portion of the improvement has been completed. 
  • JD34 (Le Ray Twp.)  The contractor should be finishing up all checklist items soon.   
  • CD56 (Garden City Twp.)  Finished… the new phosphorus filter was finished yesterday and started filling with water almost immediately.                                                                                                                                                                                                                              

Phosphorus Filter For Crystal Lake and Ditch 56:

Drum roll please…the long-awaited phosphorus filter is now here.  The filter was finished yesterday late afternoon, November 18.  We have been talking about this filter for over a year, so what’s all the hype about? 

The big reason for the hype is because the filter is one of a very small handful existing in the United States for subsurface tile water treatment.  The other big reason is because phosphorus issues are a growing concern in many of our Minnesota lakes and waterways.  The location for this filter was chosen strategically because of grant funding.  The grant funding was secured back in 2016 for the Lake Crystal area.  It was to help support clean water practices of multiple facets.  Our local Blue Earth SWCD (Soil and Water Conservation District) has used the grant funds to help support education amongst our local growers and landowners to support practices aimed at cleaner water solutions.  Some of those practices include cover crops, erosion control and soil health importance.

This new phosphorus filter is just another chapter to all the previous efforts for clean water in the Lake Crystal area.

Let’s dive into this phosphorus filter, why is this thing so special?  The simple way of explaining how it works and why it’s so special is as follows; water travels from the county tile line into the phosphorus filter.  The filter is full of a material called slag.  Slag is a bi-product from the steel industry.  The slag material is rich in iron and calcium and is positively charged, which attracts the water-soluble phosphorus as it travels through the filter, trapping it inside the filter.  The water comes out of the filter into the open ditch of CD56 cleaner with over 90% of the phosphorus reduced from when it entered.

We have very high hopes for the success of this project and would like to implement this same filter on other drainage systems elsewhere in Blue Earth County depending on these results.  We are hoping for cleaner water in Crystal Lake resulting in fewer algae blooms.  Ideally, this filter will compliment the already outstanding clean-water efforts in the Lake Crystal area that are constantly being made by the local clean-water group, Crystal Waters Project.

The diagram below shows how the water goes through the phosphorus cleaning filter.  The actual filter is 13 feet wide by 30 feet long and is 3 feet deep of slag material.  There is 90 tons of slag media material inside the filter.  There is one tile that feeds the water into the filter and one tile that feeds the clean water out of the tile to the open ditch.  It is a very simple theory in the grand scheme of things, but hopefully very effective. 

One final thanks to all those involved in making this project happen which included; Blue Earth County SWCD, Crystal Waters Project, ISG, Gustafson Drainage, City of Lake Crystal and Sandt Farms.  We all thank you, very much.  Local news station KEYC TV was kind enough to do a very nice news story about our new filter.  Click on link.

phos filter diagram

installing slag media 4

Slag material being installed into filter area.


Recent Drainage Inspections – week of November 11 – November 15:

  • CD35 (Mapleton Twp.)  Televising and repairs to portions of tile on this drainage system where conducted last week.  The televising of tile portion we chose was in bad shape.  The beaver dam has been removed and hopefully water levels continue to drain down before freezing up. 
  • JD48 Bro (Butternut Valley Twp.)  We are hoping that one of our contractors will be able to start with repairs along this ditch system this week.  The cold of last week and now the wet of this week have slowed progress down a bit.
  • CD27 (Lincoln Twp.)  A large sink hole in need of repair. 
  • JD36 Brown (Cambria & Butternut Valley Twps.)  The contractor out making repairs on this drainage system has been making good progress.  Five of the six major repairs have been made, with hopes that the last repair will be completed this week.
  • CD28 (Lincoln Twp.)  Our large ditch bank blow-out will require large amounts of dirt to be hauled into the repair site.  Much of the material moved and excavated from the phosphorus filter sight will be hauled to this system to be used on the repair.  Trucks will start hauling material once the ground freezes up a little bit more.  Things are way too soft and muddy at the moment.   
  • JD28 (Decoria Twp.)  There are two areas of tile blow-outs.  One was an inspection in-take that the cover was damaged and pushed into the tile line.  The other sink hole is an on-going problem area.  We have a larger tile with lots of grade on a bend that flows into a smaller tile that has a flatter grade.  This is not uncommon on tile systems, but with being shallow in the ground and the amount of pressure from the water when the pipe is full, it has been a battle trying to resolve the issue.
  • CD56 (Garden City Twp.)  Besides installing our new phosphorus filter, we have more issues with collapsing tile and sink holes.

We require that all repairs to a county drainage system (tile or open ditch) be authorized by one us in the drainage office, either Craig or myself, before any repairs are made.




Ryan Hiniker

Drainage Management Specialist