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subsoiling), can be effectively conducted when the soil material (subsoil or replaced topsoil) is in rainfall infiltration are being restored, a policy limiting all further traffic to permanent travel lanes either a “plastic” or “liquid” state of soil consistency. Pulling the respective implements legs is maintained. through the soil when it is overly moist only results in the “slicing and smearing” of the material or added “squeezing and compression” instead of the necessary fracturing. Ample drying time is The other critical elements, outlined below, are: using the proper implements (deep, heavy-duty needed for a “rippable” soil condition not merely in the material close to the surface, but rippers and subsoilers), and ample pulling-power equipment (tractors); and conducting the practice throughout the material located down to the bottom of the physically compressed zone of the at the appropriate speed, depth and pattern(s) of movement. subsoil. Note that an appropriate plan for the separate practice of establishing a healthy perennial ground The “poor man’s Atterberg field test” for soil cover, with deep rooting to help maintain the restored soil structure, should be developed in plasticity is a simple “hand-roll” method used advance. This may require the assistance of an agronomist or landscape horticulturist. for quick, on-site determination of whether or not the moisture level of the affected soil material is low enough for: effective deep Implements ripping of subsoil; respreading of topsoil in a Avoid the use of all undersize implements. The small-to-medium, light-duty tool will, at best, only friable state; and final decompaction (deep “scarify” the uppermost surface portion of the mass of compacted subsoil material. The term subsoiling). Using a sample of soil material “chisel plow” is commonly but incorrectly applied to a broad range of implements. While a few obtained from the planned bottom depth of may be adapted for the moderate subsoiling of non-impacted soils, the majority are less durable ripping, e.g.: 20 - 24 inches below exposed and used for only lighter land-fitting (see Figure 6). subsoil surface, the sample is hand rolled between the palms down to a 1/8-inch diameter thread. (Use the same test for stored topsoil Fig. 5. Augered from a depth of 19 inches material before respreading on the site.) If the below the surface of the replaced topsoil, respective soil sample crumbles apart in this subsoil sample was hand rolled to a segments no greater than 3/8 of an inch long, by 1/8-inch diameter. The test shows the soil at the time it is rolled down to 1/8 inch diameter, it this site stretches out too far without is low enough in moisture for deep ripping (or crumbling; it indicates the material is in a topsoil replacement), and decompaction. plastic state of consistence, too wet for final Conversely, as shown in Figure 5, if the rolled decompaction (deep subsoiling) at this time. sample stretches out in increments greater than 3/8 of an inch long before crumbling, it is in a “plastic” state of soil consistency and is too wet for subsoil ripping (as well as topsoil replacement) and final decompaction. Fig. 6. A light duty chisel implement, not Fig. 7. One of several variations of an adequate for either the deep ripping or agricultural ripper. This unit has long, rugged Design Guidance shanks mounted on a steel V-frame for deep, decompaction (deep subsoiling) phase. aggressive fracturing through Phase 1. Beyond the above-noted site factors, a vital requirement for the effective Deep Ripping and Decompaction (deep subsoiling), is implementing the practice in its distinct, two-phase process: Use a “heavy duty” agricultural-grade, deep ripper (see Figures 7,9,10 and 11) for the first phase: 1) Deep rip the affected thickness of exposed subsoil material (see Figure 10 and 11), aggressively the lateral and vertical fracturing of the mass of exposed and compressed subsoil, down and fracturing it before the protected topsoil is reapplied on the site (see Figure 12); and through, to the bottom of impact, prior to the replacement of the topsoil layer. (Any oversize rocks which are uplifted to the subsoil surface during the deep ripping phase are picked and removed.) 2) Decompact (deep subsoil), simultaneously through the restored topsoil layer and the upper half Like the heavy-duty class of implement for the first phase, the decompaction (deep subsoiling) of of the affected subsoil (Figure 13). The second phase, “decompaction,” mitigates the partial Phase 2 is conducted with the heavy-duty version of the deep subsoiler. More preferable is the recompaction which occurs during the heavy process of topsoil spreading/grading. Prior to deep angled-leg variety of deep subsoiler (shown in Figures 8 and 13). It minimizes the inversion of the ripping and decompacting the site, all construction activity, including construction equipment and subsoil and topsoil layers while laterally and vertically fracturing the upper half of the previously material storage, site cleanup and trafficking (Figure 14), should be finished; and the site closed off ripped subsoil layer and all of the topsoil layer by delivering a momentary, wave-like “lifting and to further disturbance. Likewise, once the practice is underway and the area’s soil permeability and shattering” action up through the soil layers as it is pulled. 5 6 Page 306 of 1493