Check Out My Gravel Pit

we've been thinking about crushed rock and gravel lately too, what it is, where it comes from...

the 1/4-minus gravel we used for the pathway we've been documenting here is one of our favorite landscaping materials. it has a great feel underfoot, packs and drains extremely well


we've noticed that there is a good bit of variation in product between suppliers

lets get educated about the sand, gravel and crushed rock business!

from The Production of Granite in the New England States, by A. T. Coons :

-- Crushed stone-The demand for crushed stone began late in the nineteenth century with the introduction of water-bound macadam roads. The use of crushed stone in concrete for foundations and buildings began about 1900, and its effect on the building-stone industry was soon noticeable. By 1907 the value of the crushed stone sold exceeded the combined values of the building and monumental stone. The quarries of New England States were among the first to supply crushed stone, but most of this material was basalt. Few of the New England quarries that supply building and monumental granite furnish crushed stone in any quantity. Massachusetts is the largest producer, and the greater part of the output comes from quarries especially operated and equipped for turning out this product. [...] At present water-bound macadam is being superseded by asphaltic and cement-concrete pavements, in which gravel is used as well as crushed stone for the aggregate. Specially prepared crushed granite is finding considerable favor in terrazzo work for floors and in the better class of concrete exterior construction. In this work the color of the stone, as well as well as its durability, is all importance.

-- some informative discussion of gravel at Dave's Digital Outcrop, in geology field-trip notes of the same Dave Knoblach who educated us as to the geology of the Wilkeson WA area in the preceding post. today we are peeking at field trip notes for an excursion in the Puget Sound area, in the vicinity of Orting, WA.

(from http://students.washington.edu/knoblach/field_trip%232.htm)

[...]

Creek Ridge Glen

This is a controversial site. It is the top of a glacial delta deposit that contains economic quantities of gravel. It is the best gravel resource in the immediate vicinity. The southern portion of this deposit is proposed for mining. However, the pit is facing stiff resistance by local residents. Here, the northern portion of the delta is being developed for residences, causing the gravel deposits to be lost for development as a natural resource.

Gravel is a bulky, low-value product that is very important. Many areas of Puget Sound contain poor soils that turn to mush during the rainy season. Gravel is essential as fill material in the construction of homes, buildings, and roadways. It is the major component used in concrete and asphalt. Even in areas with no growth, gravel is needed for the maintenance of roads and property. Every year, the average Washingtonian uses 14 tons of sand and gravel, 2 tons of concrete, and 1.5 tons of asphalt. The average western Washington home requires 220 tons of aggregates for construction, and the construction of a one-mile section of 4-lane highway requires 8,500 tons of sand, gravel, and crushed rock (Washington's Aggregate Resources, Washington Aggregates and Concrete Association, 1995).

gravel somewhere

The gravel here is a high-quality economic gravel. It can be used for more applications than gravel in the White River because it is make of stronger granitic rocks and sand. Puget Sound is fortunate to have several large gravel deposits left by the glaciers (other areas are not so fortunate--local gravel has been shipped from Puget Sound as far away as Guam). Unfortunately, these local economic deposits are limited. They are found only in delta areas like this (and this is a relatively small deposit). Currently, most gravel deposits in Puget Sound either have been exhausted, are close to exhaustion, or are already lost by residential development.

Note that another gravel pit is located on the north side of Hwy. 410 (two miles east of Sumner). Located outside of the glacial delta area, the pit has limited gravel deposits. However, the expected reserves were further lowered by the geology in that area. The upper portion of the hill contains glacial till. Till contains too much silt to be used as gravel (silt easily turns into mush when wet). Additionally, the till is expensive to remove and hard on equipment because it was packed hard by the glacier. If there were significant gravel deposits under the till, the upper layer of waste could be removed, however below the till is a very thick layer of lahar deposits from Mt. Rainier. The lahar deposits appear very similar to till and are packed hard by the glaciers that moved over them. Because of the location of this gravel pit and the geology of this site, the gravel pit did not produce much gravel. A better location would have been this site.

The cost of moving gravel by roadway is very expensive. It doubles in price quickly as travel distances increase from its source. Moving gravel by roadway also increases traffic, broken windshields, adds wear to roadways (causing more frequent repairs), and increases pollution. Cement batch plants also have to be located near local populations because after mixing, cement hardens very quickly. It is in the best interest to preserve local gravel resources to keep costs low, reduce traffic, and be efficient.

Twenty years from now local and adjacent resources may be exhausted. Large amounts of gravel will be barged across the Pacific Ocean to supply needs of metropolitan areas around the Pacific Rim. Currently, portions of Europe have resorted to dragging the continental shelf for gravel (with an obviously greater environmental impact than mining gravel on land). That is our future. It may be best to delay that future in our part of our world for as long as possible by not wasting our limited local resources.