Your Lagoon Shouldn't be a Scary Little Secret

Published on Wed, 10/24/2018 - 1:35pm

 Your Lagoon Shouldn't be a Scary Little Secret

 By Bruce Derksen for American Dairymen

 Just like any good horror movie worth its salt, some dairies have their own scary little secrets- usually hidden out back behind the barns, corrals and buildings, and sometimes tucked away beyond a row of unassuming trees.  It’s an essential part of many progressive dairies, even though it’s not usually discussed and if it is, then only in hushed dismissive tones with the intent of moving on to a less awkward conversation.  Yes, it’s the all- important lagoon.

If you are designing and building, do your best to make it right the first time, because it really is more than just a “you know what” hole.  It can be so much more.
To construct a new lagoon economically without using concrete for the floors and embankments, or laying down an artificial liner, a suitable on-site clay soil is required.  Consideration must be given to the volume required to create a good seal as all care must be taken to contain the contents without allowing residual amounts to seep into the groundwater or escape creating pollution.  Be sure to remove all rocks, gravel, roots or other materials that will not be a part of a proper sealant.  Create embankments with a minimum of 5% extra material to allow for settlement, mowing and erosion prevention.  Pack, pack and pack some more throughout the embankment walls and floor to complete the proper seal.  A good rule of thumb is three packer or roller passes for every 6 inches of fill added.  Such amendments as soda ash or bentonite may also be used.  Once a satisfactory seal has been fashioned, cover it with water as soon as possible to discourage drying and cracking.

Concrete floors and polyethylene geomembrane liners are options to create a trustworthy seal and eliminate the worry of seepage over the years.  Potential positives affecting this decision are better control of gas emissions, reduced odor and superior groundwater protection.  Negatives are obvious material and labor costs involved.  Covers can also be added to further reduce odors and emissions along with controlling flies and insect populations.  An increase of approximately 25% in capacity can be achieved by eliminating rainwater, plus the manure quality is enriched by capturing more ammonia resulting in higher nitrogen content.
Position inlets at the center of the longest side and in more than one place if possible, discouraging the accumulation of solids in specific areas.  Include readable markers showing pump out and fill levels.  This simple act will instill confidence in any inspectors or regulatory personnel that a lagoon is being managed properly.  Locate intakes for recycle pumps away from the lagoon inlets to prevent plugging and consider a wet well to house the pumps for easier repair or maintenance access.
Beware that constructing a properly designed lagoon is only half the battle and will be pointless if not managed properly.  For a new lagoon, be sure to fill it to at least a third or half volume level before introducing any manure, to ensure enough dilution is available to establish proper bacterial activity.  If possible, start your lagoon in spring or early summer to build a bacterial population before cold weather and help prevent excessive odors in the upcoming spring.
Once a lagoon is in use, continuous loading is recommended to keep this proper balance allowing the two-stage process of different bacterial cultures to combine, breaking down complex organic compounds into methane and carbon dioxide.  Imbalances can result in overall declines in bacterial populations, and depending on the magnitude, may result in increased odor and/or sludge accumulation.
Be diligent in the pumping and irrigating of the lagoon.  Along with preventing a possible over-flow from excessive rainfall, agitation and pumping removes suspended and dissolved solids delivering a larger overall volume.
Make your lagoon usable, efficient and as pleasing to the eye as possible.  Berms and embankments could feature a clean grass cover for appearance, erosion, mowing and regular maintenance.  If it’s located within public view, consider a row of trees to help block it from sight and possibly deflect winds and odors away. A well-maintained lagoon is less likely to attract attention and cause negative controversy than one with an offensive appearance.  Remember, your dairy’s dirty little secret doesn’t have to be scary, but can be efficient, productive, environmentally friendly and safe.