Preservation Matters: Landscape Maintenance- Managing Snow and Ice at Historic Properties

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Many historic properties remain open through winter months; welcoming visitors for interpretive programs and events, supporting staff with ongoing administrative and resource management functions, and engaging educators and students in learning activities. In areas where temperatures dip below freezing, snow and ice management is necessary to safely support these functions. Contemporary expectations for snow and ice management in the United States typically contribute to setting operational standards at historic properties. However, since many commonly used snow and ice management equipment and materials can damage historic features such as original masonry and aged vegetation, alternative techniques that protect these resources should be considered.

Historic image of boardwalk on side of road with horse drawn carriage 
in street.

“View along Warren Street toward Hood’s place”; March 7, 1900. Photograph by John Charles Olmsted, #673-6.
Olmsted National Historic Site Archives, National Park Service, United States Department of the Interior.

Brief History of Snow and Ice Management in North America

Prior to the growth of automobile usage in the early 20th century, snow accumulation on roads was necessary; wheels on horse-drawn carriages and wagons were changed over in winter months to skid-skis which needed a good snow base to glide along effectively. Large, horse-drawn snow packing equipment was used for compacting loose snow on roads to make it more adaptable for pulling skid-skis over it.

In areas where snow removal in walking and working areas
was necessary, it was shoveled. Locations that were challenging to shovel, due to irregular and uneven stone or dirt surfaces, were often covered with boards ahead of the winter to help facilitate snow removal and reduce the need to walk through melting snow, ice and mud.

Icy walking areas were commonly treated with aggregate materials such as sand and coal cinders to minimize potential slipping.

Historic patent image of snow removing device.

Ghel, John. 1939-08-08. Snow-removing device. United States of America, US-2168866-A.

By the 1920s, as automobiles became the primary mode of vehicular transportation, the need for snow and ice removal became important to improve driving safety. Plows replaced snow rollers to remove rather than compact snow on driving surfaces. In 1926, the first snowblower was patented and soon became the primary equipment for removing snow from pedestrian surfaces.

Use of rock salt (sodium chloride) for snow and ice melting greatly increased from the early to mid-20th c. on both roads and pedestrian walkways. In the late 20th c., recognition of environmental impacts resulting from sodium chloride use, such as soil and water contamination, led to greater availability and use of other more sustainable materials. Advancements in equipment have improved snow and ice management to the point where in the 21st c. bare pavement soon after a snowstorm is the common expectation in North America.

Salt damage to shrubs

Joseph LaForest, University of Georgia, Bugwood. org, https://www.forestryimages.org/browse/detail. cfm?imgnum=5025080#, 2006.

Historic Preservation Issues Associated With Snow and Ice Management

Effective snow and ice management at historic properties is important for safety of employees and visitors, access for operational functions and emergency response, protecting resources, and to support on-site events and programs. Contemporary techniques for snow and ice management can be very effective; however, they may also result in damage to historic property resources. Types of adverse impacts that may result from snow and ice management at historic properties include:

Physical damage

» Dislodging, displacement, or breaking of built features by snow removal equipment
» Scratching and wear of surfaces from equipment, sand, and other ice management abrasive materials
» Wounding, breakage, and smothering of vegetation by equipment or piling of snow

Chemical damage

» Deterioration of historic resources that are vulnerable to salt or other ice control
materials
» Staining and discoloration of surfacing materials
» Killing or dieback of plants and turf from salt spray or increased salinity of soils

Integrating Snow and Ice Management with Historic Preservation Objectives

When identifying snow and ice management objectives at historic properties, it is critical to align them with preservation and resource stewardship goals. Considerations such as: types of equipment and chemicals to use; where and how much snow should be stockpiled; pre and post storm resource protection; etc., can have effects on historic features at a property. Approaches to preparing snow and ice management for historic properties should include:

Identifying snow and ice management priorities and objectives

» Determine which areas are critical to keep free of snow and ice for emergency response (fire, law enforcement, medical, etc.)
» Identify areas that are important to keep free of snow and ice to support site operational needs, visitor programming, events, etc.
» Evaluate and identify historic resources that may be impacted by snow and ice management. Determine best options for protecting those resources from
possible damage.
» Acknowledge that some areas that have particularly sensitive resources or are ordinarily used during other seasons may be closed during winter, allowing snow and ice to accumulate rather than removed.

Hedges and shrubs protected from damage caused by salt spray and snow loads.

Charles Pepper

Protecting historic resources ahead of snow and ice accumulation

» Install markers to identify sensitive resource locations and areas where snow and ice management should be avoided.
» Tie branches of historic shrubs in areas where large amounts of heavy snow may accumulate to minimize damage or breakage due to weight.
» Install protective framing over shrubs, hedges, statuary, and other features that may be damaged by snow and ice weight accumulation (see image on right).
» Cover branches and foliage of shrubs (particularly those of broadleaf and needleleaf) that are sensitive to salt or chemical ice control treatments. Burlap or non-woven polyester fabrics are effective materials that minimize damage from salt and chemical ice control treatments while allowing air circulation around plants. Remove and dispose of coverings in early spring.
» Apply a 1” - 2” layer of organic matter over the root zone area of trees and shrubs in areas where salt and/or chemical ice control treatments may be applied. The layer of organic matter will reduce the amount of salt or chemical ice treatments that permeates the soil below. When applying the organic matter keep the material at least 3” from the stems or trunk of the plants. It is important to remove and dispose of the applied layer of organic material in early spring.
» Identify and mark snow and ice dumping area(s) that are well away from historic structures, built features, and plants.
» Place temporary but durable winter season fencing adjacent to important historic features to prevent accidental physical damage during snow removal operations.
» Install rigid ground protection mats on surfaces that may be adversely impacted by snow removal operations, such as shallow archeological resources; historic turf or ground cover; loose aggregate; decorative, aging and/or deteriorated paving; or irreplaceable features and materials. Ground protection should be slightly elevated 2” – 4” above the height of the surface to allow air circulation. Protective mats should be removed in early spring when the chance of further snowfall is unlikely.

Rubber edge snowplow.

Dodge 3500 1 Ton 4 x 4 Dump with Plow at Gettysburg National Military Park in February 2009, Gettysburg National Military Park, Gettysburg, PA, https://npgallery.nps.gov/ AssetDetail/33ae1007-d720-48f9-a051-dbd7d3c6f0f9#.

Using resource sensitive techniques

» Use a blower or broom to remove snow from walkways, plantings, and other small scale landscape features. If plants and other features have been protected with coverings, framing, or mats, use a blower to remove snow accumulation and reduce the buildup
of weight.
» Use plastic, not metal shovels, on historic surfacing and paving materials that are prone to abrasion and damage (sandstone, slate, decorative materials, etc.).
» Plow snow using a blade edged with rubber or urethane to reduce surface material abrasion and damage.
» Use the smallest equipment necessary to complete the task. Where possible, use a leaf blower instead of a shovel, a shovel instead of a snow blower, a snow blower instead of a plow, etc.
» Raise skids on snow blowers and blades of snowplows by at least 1” above grade to reduce possible scraping and other physical damage of surfacing materials. If the remaining 1” of snow doesn’t melt, apply an aggregate material to increase traction for pedestrians and vehicles.
» While removing snow, avoid blowing and plowing snow toward historic buildings,
features and plantings, particularly when working in areas where surfacing materials,
such as stone aggregate, can be picked up, thrown by equipment, and damage building materials, tree bark, etc.
» Dedicate specific locations for creating snowbanks and dumping areas that are away from historic structures, features, and plantings where the weight of snow accumulation may cause damage or melt run-off may cause water damage.

Applying surface treatments

» Minimize use of salts for ice management. Salts can be corrosive to metal features, hasten deterioration of masonry resources, and adversely impact vegetation. Consider using aggregate alternatives to salt such as sand, fine stone dust, non-clumping kitty litter, wood ash, sawdust, etc. Where possible, select an ice management aggregate material that is compatible with the surfacing material below. For example, if the surfacing material of a pathway is woodchips, apply sawdust for ice management rather than sand, or, if a brick walkway has sand within the joints, apply sand rather than stonedust.
» Consider using electric ice melting mats, particularly in areas leading to historic building entrances where it is preferable to minimize use of aggregates that may be brought in on shoes resulting in abrasion to flooring materials.
» If salts or other chemical treatments must be used for safety purposes, reduce amounts being applied by mixing with sand or other aggregate. Use products made of Calcium Magnesium Acetate or Urea/Carbonyl Diamide which are potentially less damaging to resources than those with Magnesium Chloride, Potassium Chloride, and Sodium Chloride (rock salt).
» Explore using alternative commercially available natural ice management materials such as spreading alfalfa meal. Adding beet juice to brine solutions for ice management can be effective for lowering the freezing temperature of water. Products made of red beet juice are not recommended as they may stain historic masonry and wooden features.

Implementing post-winter recovery actions

» Remove protective coverings, staking, fencing, etc. from the property in the spring as soon as potential for larger storms has diminished.
» Inspect all resources within and adjacent to snow and ice management areas for physical and chemical damage. Look for features that may have been dislodged, uplifted, scraped, dented, broken, etc. Assess plants for broken limbs and branches, foliage dieback, salt accumulations on soil, etc.
» Identify and implement corrective actions as soon as possible. Replace damaged and broken historic features such as brick or fencing, wash away salt accumulations, prune broken branches, remove accumulations of sand and other materials applied for ice management, etc.
» Evaluate and note what worked well and what needs to be improved for snow and ice management at the property. Use these observations for informing operations in
future years.

Conclusion

Snow and ice management is an essential aspect of historic property stewardship. However, it is important to recognize that some commonly used contemporary methods of snow and ice management may adversely impact historic property resources. Adapting and using techniques that recognize the potential sensitivity of these resources can be effectively implemented to meet operational needs and preservation goals at historic properties.

References

“Biobased De-Icers and Anti-Icers Save Roads, Bridges, and the Environment,” BioPreferred©, USDA, https://www.biopreferred.gov/BioPreferred/faces/pages/articles/BioDeicers.xtml

Dodge 3500 1 Ton 4 x 4 Dump with Plow at Gettysburg National Military Park in February 2009, Gettysburg National Military Park, Gettysburg, PA, https://npgallery. nps.gov/AssetDetail/33ae1007-d720-48f9-a051-dbd7d3c6f0f9#.

Ghel, John. 1939-08-08. Snow-removing device. United States of America, US-2168866-A. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/2168866

Janna Beckerman and B. Rosie Lerner. “Salt Damage in Landscape Plants,” Purdue University,

Purdue Extension, April 2009, http://www.extension.purdue.edu/extmedia/ID/ID-412-W.pdf

Joseph LaForest, University of Georgia, Bugwood.org, https://www.forestryimages.org/browse/detail.
cfm?imgnum=5025080#, 2006.

Mergen, Bernard. “Slush Funds: A History of D.C. Snow Management.” Washington History 8, no. 1 (1996): 4–15. http://www.jstor.org/stable/40073184.

“Snow and Ice,” Natural Disasters, EPA, October 30, 2023, https://www.epa.gov/natural- disasters/snow-and-ice

Snow Roller, Poland Spring, c. 1890, MMN 25524, Poland Spring Preservation Society, Poland Spring, ME, https://www.mainememory.net/artifact/25524.

“Sustainable Winter Management Guidelines,” Business Management, Turf Magazine, October 12, 2018, https://turfmagazine.com/sustainable-winter-management-guidelines

“View along Warren Street toward Hood’s place”; March 7, 1900. Photograph by John Charles Olmsted, #673-6. Olmsted National Historic Site Archives, National Park Service, United States Department of the Interior.

Author and Editor

Author: Charles Pepper, Principal, Landscape Preservation Specialists
Series Editor: Kirk A. Cordell, NCPTT Executive Director
Cover Photo: https://www.mainememory.net/artifact/25524.

About NCPTT
The National Center for Preservation Technology and Training (NCPTT) is a research, technology and training center within the National Park Service. NCPTT publishes its Preservation Matters Series to provide easily accessible guidelines for preserving cultural materials.