Discussion on Topsoil Requirement and Potential Amendments or Alternatives (Project No. 146)

As the Board will recall, a couple months ago, a general discussion on the City's topsoil standard occurred.  The impetus for that discussion (and this case) is a request from a developer/builder that the City revise the topsoil standard by eliminating the specification for Premium Topsoil Borrow.  The request  identified two negative effects of the current topsoil requirement. First, that the topsoil is doing too good of a job in terms of holding water. They acknowledge that many homeowners are not adjusting their irrigation systems to account for the topsoil and are actually contributing to the problem. Secondly, they identified price as a concern compared to the cost of 'regular' black dirt.

As part of that initial discussion, Staff was asked to gather information on what similar peer communities (with similar sandy soils) require and what the purpose of the requirement was (to see if it is an apples to apples comparison).  Additionally, Staff has attempted to compile water usage data for the City over the past ten (10) years or so in an attempt to assess the effectiveness of the current topsoil requirement to reduce water usage.

Review of Peer Communities Topsoil Requirements

Staff contacted multiple communities that are all situated within the Anoka Sand Plain (these would, in general terms, all have sandy 'base' or native soils with less water holding capabilities).  A summary of each communities' standards is attached to this case.  Based on this review, it is clear that Ramsey has a much more stringent approach to topsoil, from how it is defined to our inspection process, than other communities.  It seems that communities that have adopted a topsoil requirement have done so with an intention of reducing demand on groundwater while also assisting with vegetation establishment.

Cost Comparison

Staff has also obtained cost estimates from the builder/developer making the request and others regarding the cost of topsoil meeting the City's current specification and 'normal' black dirt.  The information helps illustrate the cost added to an individual lot (and therefore, passed on to the home buyer) to comply with this standard.  As a reminder, the topsoil requirement is applicable to any lot (commercial/residential/industrial/institutional) being developed with a new, principal building, regardless of whether it is connected to the municipal water system or not.  These costs are representative of the typical lot sizes being developed currently.
 

Approximate Lot Size	Estimated Cost of Premium Topsoil Borrow	Estimated Cost of Regular Black Dirt	Price Difference
6,000 sq. ft. (0.15 acres)	$3,690	$2,250	$1,1440
10,800 sq. ft. (0.25 acres)	$5,740	$3,500	$2,240
43,560 sq. ft. (1 acre)	$10,660	$6,500	$4,160
108,900 sq. ft. (2.5 acres)	$19,000	Unknown	Unknown

Alternatives to Premium Topsoil Specification

As has been noted, the present request is not to entirely eliminate the topsoil requirement, but rather to modify it to something more consistent with surrounding communities.  This would still provide improved soil characteristics (compared to the native/base soil), but at a more cost effective rate.  This could also help eliminate some of the undesirable characteristics that many yards have exhibited, such as oversaturated, spongy/soggy ground (which is also a result of over watering, not just simply due to the topsoil).

Advances in irrigation technology over the past decade have made it easier and more cost effective to conserve water through better sprinkling habits.  Smart controllers can be connected via the internet to local weather information, weather stations, historical precipitation data, etc. to assist with reducing unnecessary waterings.  Also, soil moisture sensors, often available for $150 or less, can be utilized in different parts of a yard (with different growing conditions) to ensure that the irrigation system doesn't turn on that zone unless there is insufficient moisture in the soil.  The message coming out of the U of MN's Extension team is that water efficient irrigation systems, not new turf varieties or soil amendments, have become the most cost effective means to reducing non-consumptive water usage (e.g. irrigation).

City Code now requires any new irrigation system to have a water efficient technology.  However, there are many systems out there that could be retrofitted.  This comes at a higher cost than 'upgrading' a new system.  The City could (should?) consider developing a rebate program that may incentivize owners of existing irrigation systems to retrofit them with newer technology.  Additionally, a simple 'irrigation system tune-up' could also be incentivized to not only ensure that a system is running properly with no leaks or malfunctioning parts, but also, hopefully, results in some homeowner education about how their system works.  The city of Elk River, through their municipal utilities division, has an established rebate program that could be used as a model.  It may also be possible to find grand funds that could be utilized to establish and offer these rebate programs.

Weather/Precipitation/Landscape

The largest factor in water usage has always been and will likely always be the weather, and more specifically, precipitation.  That's one of the greatest advantages of the new technologies now available for irrigation systems, weather can be and is factored into the programed run-times.  The water usage data does show a clear correlation between reduced precipitation and increased water usage. 

Additionally, canopy cover can also play a significant role in watering needs of a yard.  Shady portions of a lawn require much less water than sunny portions.  Again, options such as soil moisture sensors placed in differing growing conditions within a yard, can significantly reduce water usage by restricting which zones actually run on a scheduled day/time.

Recommendation

While topsoil is a beneficial addition, both for water conservation and vegetation establishment, the cost difference of an engineered soil compared to a more standard black dirt is significant.  Focusing more on the irrigation systems and water efficient technologies rather than engineered soils, along with additional educational information on irrigation systems, should be as effective as the current standard regarding reducing demand on groundwater.  It would certainly be accomplished at a lower cost to the future homeowner (and possibly current homeowners if a rebate program were implemented).  Thus, Staff would recommend proceeding with an Ordinance Amendment to modify the definition of topsoil consistent with other peer communities (such as "black dirt composed of unconsolidated material, largely undecomposed organic matter with no more than 35% sand").





 

This case is being handled as part of Staff's regular duties.

Motion to direct Staff to prepare an Ordinance Amendment to revise the definition of topsoil.