No. 5: FARM LANES
Farm lanes have not received the attention given to other forms of farm property. Improvements have been made in farm structures, materials handling equipment, utility services, manure storage, etc., but the farm lane remains a problem, particularly in the spring.
What caused the lane to fail? It may be from increased use, increased weight of traffic, no attention given to drainage so it is frequently waterlogged; or it may be badly constructed. It is safe to guess that when it was laid down it was intended for horse traffic and less use.
In many cases the farm lane is of the same construction today as a century ago - a bit of gravel on top of original topsoil. Farm lanes were intended originally for horse-drawn vehicles with an occasional threshing machine. Nowadays a farm lane must carry the longer and heavier types of commercial trucks carrying fertilizer, feedstuffs, and transport type milk trucks. On farm equipment such as combines with trailing wagons have all changed the use of the farm lane.
The farmer is usually not faced with building a completely new lane but with the improvement of an existing one. Farm roads and lanes are of two classes. The primary class is the farm lane serving the farmstead and buildings from which the business of the farm is carried on. This lane will carry a greater volume and weight of traffic and should be built with a well-drained dense surface needing minimum maintenance. Livestock should not have access to the lane area.
Secondary lanes are those that serve the fields. The secondary lanes get infrequent use and are usually grassed tracks between fields. Maintenance is filling the potholes as they occur. They are adequate when the weather is dry. No discussion on these lanes is included here.
The cost to renovate or construct a farm lane is affected by the size of the job, the distance to haul materials, the nature of the subsoil and the work that needs to be done, including drainage. Your LICO drainage contractor can give you an estimate of the cost and do the entire job.
Laying Out the Lane
Overhead clearance is very important. Large tree branches, overhead wires and other obstructions need to be considered and possibly changed.
Entrance from the Road
The entrance must be located so there is clear vision for a distance of 600 feet in each direction so the lane traffic does not interfere with safety of other road traffic
The entrance gradient from the road to the lane should not exceed 3 percent whether in cut or in fill situations.
The turning radius off a road must provide that a farm tractor and trailing implement, milk transport, or other large vehicle making a right-hand turn will not have to enter the approaching road lane to enter the farm premises. Most standards require a minimum 25 foot turning radius.
This means the entrance to the lane must be 50 feet wide 11 feet from the centre line of the road (just on the shoulder of the road) and then taper down to a minimum width of 12 feet as measured at the farm gate or when 40 feet from the centre line of the road. The 40-foot distance may need to be reduced if the road right of way is only 66 feet. (See the illustration above).
The minimum width of entrance lane, as measured at the road ditch is 20 feet. The road standard requires a minimum length of culvert of 26 feet. The minimum culvert diameter is 15 inches. Both of these dimensions will be influenced by a local situation. The end treatments of the fill requires at least a 2 to 1 slope at the culvert. The depth of cover over a culvert is 12 inches. The standard also specifies the quality of the road base. This will be discussed below.
Lane Width and Yard
Reconstructing the Lane
It is recommended that you employ a LICO drainage contractor to build the lane. He has the knowledge and proper equipment to do the job. You might consider improving some field drainage at the same time. Most farms do not have equipment that will do a proper job, nor has the farmer time to do it himself.
It is essential that the drainage of the lane be addressed first. It is the native soil that supports the weight of traffic. In a dry state it will carry almost any weight without failing.
However, if there is excess water in the subsoil it quickly reduces its bearing capacity. Muck oozes up from below. Muddy lanes make buildings and livestock dirty. Tile drains can reduce wetness and frost boils in the spring.
Excess water in the subsoil is best removed by tile drains. The tile drain location is site specific. Often a tile line down the centre of the lane is adequate. In other situations a tile on each side of the lane may be needed. A safe outlet must be provided. The drains for the lane can often form part of the field system if barnyard discharge and other pollutants are excluded from the drains.
Many farm lanes are low in the centre and behave like a bathtub with surface water collecting on the lane. Proper surface drains such as a shallow ditch on each side of the lane should be constructed to remove any water falling on the lane or on adjoining land. The surface of the lane should be gradede and cambered to drain the water into the side ditch channels. There must also be some means of having water move from one side of the lane to the other. Ditches should be channelled to a safe disposal area.
Constructing the Farm
The roadbed is the parent soil underlying the lane after removal of top soil. After the needed drainage is in place, excavate the top foot of soil. This material is best shoved to each side of the lane by a bulldozer as it will be used later to bank up the sides of the lane.
Line the subgrade with a woven geotextile fabric. The purpose of this material is to prevent soil separation and for road base stability. Without this material heavy loads shove the sub-base coarse material into the base soil or parent material which causes surface unevenness later. Use of this material also tends to reduce the amount of aggregate by almost one third.
The sub-base is a compacted layer of granular permeable material placed on the geotextile covering the roadbed. In soft subsoils it provides a firmer base. The sub-base also takes out irregularities and forms a smooth bed for the next coarse. It is not primarily there for strength reasons. Size of material used should not more than three quarters of the thickness of the layer. Pit run gravel, or, granular "B" is used often. Spread the gravel evenly and compact it to a uniform thickness. The compacted depth of the sub-base should be about 8 inches.
Compaction of farm lanes is usually done by the farm tractor or by the equipment used to build the lane. It is essential that the compaction be uniform. Try to achieve about 100 pounds per square foot of density.
The purpose of the road base is to spread and transmit the load from the surface to the road bed. If not compacted well ruts will form as the material moves due to imposed loads. The base, more than any other thing, influences the cost of the lane. The base is a compacted layer of granular permeable material providing the main supporting strength of the road structure. The recommended material is 6 inches of 5/8 inch crushed granular "A". Leave a crown over the original grade for proper drainage. Never use top soil in a road bed.
The wearing surface may not be present. It may be fine gravel with a binder or soil cement, or, for short lanes 3 inches of HL3 asphalt, or concrete.
Maintenance and Repair