Fix-It Proposal

Engineer’s Assessment

The most water accumulation on the Putnam Trail occurs in those areas where an organic soil composition is dominant (see soil composition analysis below). Especially problematic are those areas which have been resurfaced with a top soil product (mixture of compost and manure). These areas suffer from chronic ruts caused by vehicles. The bicycle and pedestrian ruts flatten out about a week after rain fall.

Proposed Solutions

We propose to work in conjunction with the Parks Dept’s Trail Crew on one of the major puddle sections in the biggest trouble spot on the trail- just north of the metal bridge across the lake from the golf house. This site suffers from major vehicle ruts. The length of the work site is 106 feet with width varying between 15 and 20 feet. We propose two alternative work plans. Plan 1 involves more digging and creation of two side ditches. Plan 2 involves less digging and is a simpler re-surfacing of the area with mineral soil and stone dust. Both plans are temporary solutions, but of the two, Plan 1 is the more robust. Its drainage features will ensure that the drainage problems are remediated, not simply covered up. We offer Plan 2 as a simpler alternative that will require maintenance in a shorter time span than would Plan 1 but that would still serve to make the spot dry and usable throughout several rainy seasons. Community volunteers can help maintain this patch in the future as needed by the Parks Dept.

Plan 1

We propose to address the drainage issue in this section in two ways: 1- to remove the existing top soil surface and replace it with compacted mineral soil, 2- to construct two French drains out of salvaged materials. (Diagrams A through E)

1-     We can remove soil manually. Given the small scope of the proposed work and the number of volunteers we have, in conjunction with the Trail Crew, the process can be carried out with shovels. We can transport removed top soil to a site selected by the park administration.  The ruts in this area are 2-5 inches deep. We propose digging to a depth of 5 inches throughout the area of the proposed site. The total surface area to be worked on is 1,731 square feet. The total volume of dirt to be removed is 27.5 cubic yards. This will be replaced with an equal volume of salvaged mineral soil plus 7 cubic yards for grade elevation. We add 15% of volume to allow for compaction. Overall, 40 cubic yards of mineral soil are required. We hope to salvage the required mineral soil from other parts of the park (see Materials and Labor Analysis) pointed to by the park’s administration.

2-     The drainage structures which we propose are simplified French drains: a trench dug out under the trail coupled with a side drainage ditch. These structures can be created manually using shovels and salvaged materials (see Materials and Labor Analysis for source of materials).

There are two sites (clearings of 5’ by 5’) adjacent to the trail which we believe would be optimal for side ditches. These sites are piles of dead tree branches. We propose to use a 3’ by 3’ area of each of these sites. There is very little vegetation in and around those sites, so using these sites for side ditches would allow us to avoid disrupting healthy vegetation. The dead wood pieces can easily be moved to a larger wood pile located closer to the parade grounds.

The trenches and ditches will be lined with rocks and gravel salvaged from other areas of the park (see Materials and Labor Analysis for source of materials) under direction of the parks administration. In total about 0.4 cubic yards of gravel and 0.5 cubic yards of rocks (3-4 inches in diameter) are needed. Each of the two French drains will be enhanced by a cross slope across a 30’ area surrounding each drain (see Diagram D). The extra 7 cubic yards of soil outlined in item 1 is for the purpose of creating this cross slope. The tread will be 5 inches lower on the side adjacent to the ditches. For the 20-foot wide tread, this translates to a cross slope of 2%. The grade will be measured with a leveling scope, which can be donated by the volunteers.

The final steps after resurfacing the tread with mineral soil would follow usual practice, which is compaction. This can be done manually with hand tamps, and surfacing with stone dust or mulch. Two cubic yards of either stone dust or mulch is required and can be obtained from either the park trail crew or donated by volunteers.

Summary:

  Volume (yd³)
Top soil removed

27.5

Mineral soil for re-surfacing

40

Gravel

0.4

Rocks

0.5

Stone dust or mulch for surfacing

2

Tools required: shovels, hand tamps, buckets, leveling scope, truck or cart for transporting materials and soil. Work gloves, refreshments, and any of the tools mentioned can be supplemented by volunteers to aid the effort.

 Plan 2

We propose to address the drainage issue in this section in two ways: 1- to remove the existing top soil surface and replace it with compacted mineral soil, 2- to create a cross slope of 2% throughout the 106-foot section. (Diagrams F through G).

Given the small scope of the proposed work and the number of volunteers we have, in conjunction with the Trail Crew, the process can be carried out manually, with shovels. We will need guidance from park administration on where to transport the removed top soil. The ruts in this area are 2-5 inches deep. We will be digging to a depth of 5 inches throughout the area of the proposed site. The total surface area to be worked on is 1,705 square feet. The total volume of dirt to be removed is 27.5 cubic yards. This will be replaced with an equal volume of salvaged mineral soil plus 10 cubic yards for a 2% slope throughout the section. We suggest adding 15% of volume to allow for compaction. Overall, 43 cubic yards of mineral soil are required. An effective top surfacing from our engineer’s view is stone dust for the finished compacted tread, which is used by the trail crew to maintain the paths around the parade grounds. We suggest a measurement of about 2 cubic yards of stone dust for the 106-foot section. We hope to salvage the required mineral soil from other parts of the park (see Materials and Labor Analysis) per above. The final steps after resurfacing the tread with mineral soil would be compaction, per usual practice, and this can be done manually with hand tamps, and surfacing with stone dust or mulch. Two cubic yards of either stone dust or mulch is required and can be obtained from either the park trail crew or donated by volunteers.

 To create the 2% cross slope, we suggest the tread be made 5 inches lower on the side adjacent to the ditches. The grade will be measured with a leveling scope, which can be donated by the volunteers. To reduce uncontrolled puddles at the side of the trail, we can dig a shallow, narrow ditch in several segments (elongated ditches running parallel to the trail- approximately 6 inches deep). This would require the removal of an additional 1-2 cubic yards of soil for a total of approximately 29 cubic yards.

Summary:

  Volume (yd³)
Top soil removed

29

Mineral soil for re-surfacing

43

Stone dust or mulch for surfacing

2

 

Tools required: shovels, hand tamps, buckets, leveling scope, truck or cart for transporting materials and soil. Work gloves, refreshments, and any of the tools mentioned can be donated by volunteers to help supplement the community effort.

Engineer’s analysis of soil composition

Several types of soil composition occur along the Putnam Trail: mineral soil, organic soil (top soil), and clay-like soil.

Sections of the trail where mineral soil is dominant are compact, rough in texture, and have the least puddle accumulation and drain within 24 hours of heavy rainfall. This is due to the excellent drainage properties of the macroscopic particles of mineral soil.

Sections of the trail where organic soil composition dominates suffer from ruts and puddle accumulation. This is due to the nature of intermolecular forces between organic and water molecules. On the macroscopic level, these combined molecular forces translate to sogginess and poor drainage properties of organic soils. On the Putnam Trail, the most problematic soil is the imported top soil material which has been used in an attempt to remediate trouble spots. Samples of this top soil surfacing have a distinct smell of manure. This material is completely unsuitable for trail surfacing and should be removed.

The images below show samples of mineral and organic soils from the Putnam Trail examined on 6/15/13, approximately 24 hours after several days of intermittent heavy rainfall. The images highlight the difference in drainage properties of mineral and organic soils.

  – Margarita Eremeyev

 

A-1

A-2

C-1

D-2

E

F

 

Proposed Work Site

View from the South End

2- View from the North End

 CAD renderings of two Plans

Copyright © 2013 Margarita Eremeyev

*A rail bed is a depression in the ground filled with crushed aggregate stone that is tamped down to be firm enough to support the weight of a multi-ton train but light enough to allow for drainage in all types of weather.  This stone layer or rail ballast is 6″ to 12″ deep.  In many ways a rail trail resembles a stone-dust trail.  The rail ballast or surface on the Putnam Trail has been neglected for 30 years.