Long ago, limestone quarries were small operations with limited production due to the labor-intensive nature of the business and restricted markets for stone. The advent of individual motorized transportation brought a rapid increase in the demand for better roads.

Stone quarries answered the demand with crushed aggregate. This required more and larger quarries, resulting in more disturbed areas. A need was recognized to reclaim land previously mined and that which would be disturbed in the future. Historically, reclamation was limited to replacing removed overburden and revegetating.

This was not always the best solution. Sometimes an area where overburden was stockpiled developed its own ecosystem, which in some cases had been in existence for many years. Destroying a thriving ecosystem to comply with the letter of the law may not be responsible reclamation or very cost effective.

Cessford Construction Co. was in such a situation at its Heinold Quarry, Danville, Iowa. From 1965 to 1985, it produced limestone/dolomite aggregate and agricultural lime. The Bureau of Mines and Minerals under the Iowa Division of Soil Conservation requires compliance with Iowa Code Chapter 208 reclamation statutes before the site can be released from bond and returned to the owner.

Returning disturbed areas to a state capable of supporting vegetation is one condition of acceptance. Cessford figured it would cost more than $98,000 for labor, fuel, machine time and revegetating expense to replace the overburden necessary to comply with these statutes.

The area where overburden had been stockpiled, in some cases for 20 years, had a thriving ecosystem where wildlife found food and cover. Cessford decided to seek an alternate method of reclamation that was acceptable to the state, cost effective and nondestructive to the established ecosystem.

The City of Burlington, Iowa, processes about 6.5 million gallons of wastewater each day, producing 14 tons of sludge (20% solids) or about 1,000 dry tons per year. Don Fitting, treatment plant superintendent, has been providing high-quality aerobically digested biosolids to area farmers for many years. He agreed to provide these same biosolids to Cessford.

The project's focus was to use biosolids as a soil amendment for the stockpile and aglime areas. Biosolids would provide organic content and nutrients for the project's revegetation phase, replacing soil removed during mining operations while leaving the existing ecosystem intact.

The project area included four test plots, each two acres in size. Each test plot would have a different rate of biosolids applied, seed application and vegetation collected for analysis. The plot showing the best results would set the rate of biosolids application for future areas. The other three test plots would have reapplication of biosolids to that level. The project was to be accomplished without ground or surface water contamination. Planners identified successful revegetation and control of erosion as the final goals.

Ground Preparation Initial ground preparation began by pushing a stockpile of aglime, higher than 60 ft, to a nearly horizontal condition with a Caterpillar D7E dozer. The aglime stockpile was reduced to the elevation of surrounding topography and sloped to the east. The fall of the slope was 1 ft vertical in 7 ft horizontal. The dozer operator used an 18-in. ripper blade to plow the stockpile/aglime area with a 3-ft offset on each pass. Blade penetration was about 1 ft below the surface, breaking up hardpan which had formed over the life of the quarry.

Ripping of the stockpile/aglime area began in late March 1997 and was completed the first week of April 1997. With time and equipment in high demand in the spring, work was not continuous.

Application of biosolids The Iowa Department of Natural Resources (IDNR) had to authorize an amendment to the Burlington Wastewater Treatment Plant's permit allowing application in a non-agricultural use before biosolids application and incorporation could begin.

The IDNR consulted with the U.S. Environmental Protection Agency, Region Seven office because the biosolids application rates proposed were much higher than the agronomic uptake for one growing season. On May 15, 1997, the EPA approved Cessford's plan, followed by IDNR approval of the amendment to the wastewater permit on May 23. Shortly thereafter, application of biosolids on the test plots began.

Biosolids application began June 5, 1997, and was completed Aug. 23, 1997. Plot 2 received the first application, due to its proximity to the staging area, followed by 1, 3 and 4. Biosolids were conditioned with a polymer and dewatered at the wastewater treatment plant using two belt-filter presses. Biosolids application rate and area was controlled by the speed of the tractor pulling the material spreader. Spreader throw was about 20 ft, while length of spreading varied with amount of material. Each spreader load was about 8 wet tons. Multiple loads were required for each test plot, but were staged so that incorporation was done prior to the next application.

Incorporation of biosolids began within a few days after further dewatering and continued for a few days or as weather permitted. A roam disc with 18-in. blades pulled by the D7E was used for this purpose. The blades had an effective incorporation depth of approximately 8 in. Several passes were made to ensure proper and complete blending of biosolids and substrate. When the surface had reached an acceptable condition, a small-toothed harrow was pulled over it for leveling.

Test plots 1 and 2, each were harrowed twice. However, when this was done hardpan formed requiring a third harrowing after seed broadcast to ensure proper soil-to-seed contact. Harrowing twice was discontinued in plots 3 and 4 after discovering that surface roughness enhanced seed germination and trapped rain during dry periods.

Determination of the successful application rate for biosolids was a significant part of this operation. The amount of biosolids required to provide adequate nutrients for revegetation of reclaimed areas was an unknown. Table 1 lists the tonnage for each test plot.

These application rates were based on work done previously by coal mine reclamationists. Coal site soil characteristics were completely different due to acid mine drainage and a very low pH, but revegetation was still the desired end result.

Vegetation Originally, the plan was to use a mixture of native grasses for hay forage that would be tolerant to the elevated pH ranges expected in limestone materials. A problem arose in finding native grass species that would survive in this environment. A mixture of 10 lb Kentucky 31 Fescue, 5 lb Brome grass, 5 lb Timothy, 5 lb Linn Perennial Rye and 8 lb Lespedeza per acre was broadcast by a hand-cranked seeder. This mixture was later changed to 100% Kentucky 31 Fescue after initial germination results found only the Fescue and Lespedeza germinated permanently. Since the goal of this program was to revegetate the site, Lespedeza was eliminated because it is an annual. Only plots 1 and 2 have Lespedeza. All plots have Fescue growing vigorously.

The initial plans called for the four test plots to be completely seeded by May 1997. However, IDNR and EPA approval was not received until late May, postponing seeding until the first week of June. The species selected are cool-season grasses and seeding during June was late.

Plot 2 had the most mature growth with seeded species and volunteer species. Many volunteer plant species grew to maturity, including tomatoes, watermelons, cantaloupes, squash, gourds, flowers and weeds. The seeds for these plants came from the biosolids and survived processing to germinate.

Even though most of the plot areas were planted relatively late in the season, vigorous growth was observed. By year's end, the Fescue had far outgrown all other species. In October 1997, each plot had all vegetation harvested from a 1-sq-meter area. The area selected for harvesting was based on what appeared to be average growth. Vegetation was hand-cut, collected, bagged and the fresh weight recorded. The samples were then dried in an oven at approximately 180 degrees F for 8 hours and reweighed (Table 2).

Results indicated a large difference in mass and water content. The vegetation in plots 1 and 2 had smaller masses and water content, even though planted earlier. Vegetation in plots 3 and 4 had approximately 50% greater mass fresh, but were relatively the same dry. This indicates the percentage of water retained by vegetation in plots 3 and 4 was greater than in plots 1 and 2, the difference being the predominant species. It would seem that Fescue is better at retaining water, faster growing and better suited than other species selected for growth in a high-pH environment.

Part of the difference in plant mass also can be attributed to the Lespedeza's life cycle. When the samples were collected, it had already matured and dried. As noted earlier, plots 1 and 2 had a mixture of Fescue and Lespedeza, while plots 3 and 4 had only Fescue. The volunteer species were minor constituents in all four test plots.

Chemistry The growth rate was primarily a factor of available nutrients from the biosolids. Less desirable chemicals also were present, which may present a hazardous situation if found in concentrations higher than state regulations allow and if they migrate to surface or groundwater. Other chemicals are fixed by the interaction of compounds found in the soil.

To better monitor possible migration of these chemicals, biosolids, soil and water were tested prior to application. An ongoing testing program of post-application levels will continue. The Burlington Wastewater Treatment Plant tests the biosolids monthly for 16 constituents.

Prior to any biosolids application, the stockpile and aglime areas were soil tested for nitrogen, phosphorous, potassium, zinc, percentage of organic material and pH. All nutrient levels were very low, with organic-materials content less than 1% and pH ranging from 8.0 to 8.4.

The substrate was tested for the same constituents as the biosolids. A good database of soil chemistry was necessary to monitor compound and elemental migration from the biosolids to the soil and to ground or surface water.

The same spectrum of tests was performed not only on the soils, but on surface water contained in the lake closest to the outfall and an on-site well. The lake is located approximately 700 ft east of and downstream from the application site; the well is 200 ft south. Water samples were taken prior to application and on a quarterly basis thereafter. Quarterly samples were tested for nitrates and fecal coli only. Test results were well within state regulation limits.

Biologic Testing Biologic testing for fecal coli was performed on samples not only from the water, but the substrate and biosolids. Baseline testing showed values of less than 10 cfu/100 ml of sample, indicating bacterially safe water. Biosolids pre-application test results indicated values from less than 104 to less than 110 cfu/g. An independent laboratory tests Burlington Wastewater Treatment Plant material once a month. Values range from 84,000 to 2.3 million cfu/g. Post-application results will be available this spring.

Test results indicate that, prior to application of biosolids, the stockpile/aglime soil was very poor and inhospitable to vegetation. Post-application soil condition was greatly improved. Nutrients were plentiful and available; pH dropped from 8.0 - 8.4 to 7.4 - 7.65 and permeability and porosity have decreased.

Tests indicate no change in pH range for either surface or well water. Nitrates did rise slightly in the well water, but were still within the infant safety range. A full spectrum chemical analysis was performed this spring. It is expected there will be little or no change in current levels of metallics or compounds due to anion lockup by soil constituents.

The most poignant expression of the results of this program is seen in the growth of vegetation, regardless of species and application rate. The test plots have produced Fescue and vegetables where little grew previously. Even though seeded later, plots 3 and 4 produced the greater mass. In plot 4, Fescue reached a height in excess of 1 ft in less than eight weeks with plant density exceeding 25 stems per sq in. The volunteer species also did well. It is expected that the seeded and volunteer species will continue to thrive in 1999.

Conclusions To date, all water tests indicate little or no migration of chemicals, compounds or elements originating from the biosolids to either surface or ground water. The soil was beneficiated by the addition of biosolids: readily available plant nutrients have increased; soil compaction has been reduced; and water retention has increased. These factors have allowed the vegetation to not only germinate and grow, but to flourish. It is difficult to calculate the percentage of vegetation mass, since it is unknown whether samples taken prior to soil preparation were from one or many growing seasons. Growth was less for plots 1 and 2 than for 3 and 4 due to a lower biosolids application rate.

Recommendations The goals of Phase I have been met. The area was successfully vegetated with no erosion or degradation of surface or ground water. Costs for this phase have been minimal compared to the alternative. The same success can be expected in Phase II of the reclamation program and should be allowed to proceed under the same conditions and parameters as Phase I.

Phase II As a part of Phase II, plots 1 and 2 should have another application of biosolids that would bring the total quantity to the levels of plots 3 or 4 in Phase I, 60 and 80 dry tons, respectively. It is expected the acreage, which is primarily aglime based, should have the same success as Phase I. The area in Phase II is sloped at approximately 1 ft vertical to 7 ft horizontal and will be terraced every 100 ft. After application and incorporation of biosolids the ends of terraces will be closed to prevent migration and runoff. Seeding will begin immediately after closure of the terraces. A berm will be constructed at the base of the slope and perimeter to control runoff water and prevent migration of the toe.

Based on the success of Phase I, it is expected this area will be successfully revegetated by the end of this year. Revegetation will prevent any erosion in this area. All this will be accomplished without degradation of ground or surface water.