We cannot afford to jeopardize one of the few spaces in our community where there is an opportunity to walk in a peaceful, natural area surrounded by seasonal scents and blooms. Ladd Arboretum is not the north woods, but it is also not a park with only grass and trees. Ladd arboretum needs care and development, but the development it needs is not the addition of concrete and asphalt.

Mr. Smith is a member of the Ladd Arboretum Committee.

What it needs is the addition of more native trees, shrubs and plants that support a healthy ecosystem. The vision for Ladd is what we want it to be a hundred years from now. An inner-city natural space requires commitment and stewardship as exemplified by its founders more than a half century ago. We must respect their vision. It was their vision for our great grand children enjoy. Leadership respects the past, present and the future.

Two other important considerations are the fact that a recently constructed 8 foot wide, lighted asphalt path already exists just a few hundred feet away that is used by bike riders and runners. That path starts and ends at the same place as the Arboretum path but bypasses the Arboretum. That second consideration is the misuse of taxpayer money. This paving project is unneeded and unwanted.

Based on a review of the detailed estimates for the three construction options developed by the City of Evanston Public Works staff, all of them call for a highly intensive construction process resulting in a mile long, 8 foot wide path with 2 additional feet of limestone buffer on each side.  After consultations with U.S. Forest Service and Morton Arboretum staff and local tree experts, we believe none of the current options are suitable for the protection and maintenance of the trees and plantings at the Ladd Arboretum.  Here is a summary of the issues we have identified with the proposed project and an alternative approach we believe will address the intent of the project.

 The current plan calls for:

 

Cubic   yards*

Tons

Earth excavation 

2009 

2812

Removal and disposal of unsuitable material

1507

2110

Top soil hauled in for seeding 

4790

6706

Aggregate base material under asphalt

5080

7112

Crushed lime stone for 2 foot buffer 

1809

2533

* calculated using a conservative conversion factor of 1.4 cu/yd per ton

 

Cubic   yards*

Tons

Total materials excavation, hauling and replacement    

15,728

21,273

Hot mix asphalt 

 

1067

Bituminous materials prime coat – 2032 gallons

Including the 1060 tons of hot mix asphalt, over 22,000 tons of material will be moved under this project.

After careful review of the proposed construction process and material use, we have concluded that the project will result in serious, long-term damage to the Arboretum’s trees and the environment. The following serious impacts should be considered:

1.    Total excavation, removal and replacement of 15,728 cubic yards of material along a 12 foot corridor.  This volume of material is typically transported in large dump trucks with a capacity of 18 to 22 cubic yards.  This would result in 715 to 875 truck loads entering and leaving the arboretum over the course of installation. In order to minimize the damage to tree roots during excavation, the trees in the affected areas would be root pruned so that roots will be cut cleanly rather than broken. Root pruning when done for reasons other than the health of the tree is damaging. 

2.    Replacement of the existing limestone trail with new limestone aggregate as base material. Disturbing the existing base and hauling in fresh limestone will increase soil alkalinity (increase pH), which will be damaging to trees, particularly the mature ones which have adjusted to a stable soil pH over the past 50+ years.

3.    Use of large construction equipment and hauling trucks in the Arboretum. In order to minimize the damage to trees limbs, trucks would travel on specified haul routes. Tree limbs would be pruned to provide access for the 10-ft tall dump trucks that will travel over the same ground over and over again. Limb removal when done for reasons other than the health of the tree is damaging.

4.    Soil compaction from heavy equipment and truck traffic. When the North Shore Channel was excavated 1907 – 1910 the dense clay soil was deposited along each side. The Arboretum sits on this dense impermeable clay soil. The fine clay particles can be compacted as hard and dense as concrete and is not very accommodating to tree roots. Soil compaction not only affects the health of existing trees and shrubs, it also makes it almost impossible to grow anything there in the future.

5.    Replanting of 4 acres of grass seeding requiring 4790 cubic yards of top soil. The extensive need for replanting gives a good estimate for the anticipating auxiliary damage to the arboretum property.

6.    Special concern for installation of 1067 tons of asphalt and 2032 gallons of liquid asphalt due to human and ecosystem exposure to toxic and carcinogenic hydrocarbon compounds, particularly polycyclic aromatic hydrocarbons (PAHs) in the asphalt and sealant, and the presence of these compounds in storm-water runoff.  In addition, dark asphalt would increase the temperature of the microclimate in the vicinity of the path due to heat absorption (the heat island effect). 

Proposed alternative:

The City’s Ladd Arboretum Committee, Parks and Recreation and Public Works Departments can work together on a new plan to repair the path that ensures access, avoids damaging the trees, plants, soil and surrounding ecosystem and avoids burning hundreds of gallons of diesel fuel.  There is a cost-effective, simple way to accomplish this by resurfacing the existing path with new crushed granite. 

The existing trail was well constructed and has a firm base. The old trail, constructed in 1961, was excavated about 8 to 10 inches and filled with about 6 inches of broken limestone and 2 or 3 inches of crushed limestone. The existing trail has been compacted through over 50 years of use and has created an ideal, stable base. Little maintenance of the path has occurred over the past 50+ years and the path does need attention. When the trail has been repaired and dressed with a new top coat of crushed granite, it should be compacted with a roller to insure the surface meets ADA requirements. 

This revised approach will save hundreds of hours of City staff time, tens of thousands (or more) dollars of taxpayers’ funds and minimal damage to the trees and environment.

We welcome further discussion of this proposal and look forward to a renewed commitment to the future of the Ladd Arboretum. As reference, please see the attached photographs of the original plan design.