in time that is earlier (by several years) then that which is predicted to be achie ed with a cap alone. Using chromium as an example, this alternative wou d reduce loading t o the surrounding areas from an estimated level of 13.7 po nds per year (at a point in time one year after capping is complete and with ut any pumping) to less than 2.4 pounds per year with pumping. Capping alon would achieve a similar 2.4 pounds per year loading in approximately 8 year$ without pumping. The increased capital cost from alternative 2, fo achievement is $26,700,000. The incremental change in moni operational and maintenance costs from alternative 2 is $1, 1 Time to Implement: 36 months Direct Capital Costs: $55, $30,000 Estimated Annual Costs: $1,394,500 Alternative 3: Corplete Removal and Off-site Disposal This alternative involves the complete excavation and removql of the waste mass from Croton Point and the reestablishment of the area o former prelandfill conditions. A post remediation monitoring plan s' iliar t o but less extensive then alternative 1 is included in this alter ative. An estimated 11,600,000 cubic yards of waste would be excavated from the original and ballfield cells. Underlying soils which are vilsually 4 contaminated would also be removed. Most of the excavated matqrials would be redisposed of in permitted solid waste landfills with a les4er amount being placed in regulated industrial and or hazardous waste laljdfills. Major components of this alternative include cut-off wall constructiqn around the waste mass perimeter to allow dewatering and excavation of thewastes located below river elevations, construction of leachate hand1 treatment systems with discharges to the surrounding waters, o and dust monitoring/controla, dredging of an access channel to the landfill for barges to r e m w e the wastes and to deliver clean backfill aiateriale, and final grading for stormwater management. This alternative is being presented only for comparison purposojs since it is highly unlikely that it would be a viable option for a variety of reasons. Significant health and safety issues would require closing of Wle Croton Point Park for the duration of the project in order to minimize human health impacts. Excavation and removal of materials that took almost 6 0 years-to. accumulate will take far too long to accomplish. Locating a falcility or several facilities willing to accept this volume of material is The final issue which prevents serious consideration of the overall cost estimates. The analysis is included as an understanding of the severe ramifications involved in remove a large heterogenous landfill. - Time to Implement: 6 years (estimated) Direct Capita Cost: $3,946,000,0!I0 Estimated Annpal Costs: $163,500 Alternative 4A: Eastern Uarsh Channel Remediation This alternative was developed to address concerns over the res/llts of the sediment samples from the eastern drainage channel of the Crotoe Marsh. The eastern channel of the marsh is approximately four (4) acres insize and extends from the toe of the landfill out into Croton Bay. The area is essentially dewatered during periods of low tides. The RI data indicated that sediment samples from this area exceeded NYSDEC guidelinesfor protection of aquatic macrobenthic invertebrates and that the c-$mmunity here was less healthy than the other marsh channels. i! The various technologies applicable to remediate this area of c ncern were analyzed. The depth of sediment removal was determined to be be ween two (2) feet and six (6) feet. The actual depth would be determined in he field based upon the results of sediment analysis. These depths when ombined with the four acre area of concern correspond to a range of a minmum of 15,000 cubic yards to a possible high of 45,000 cubic yards. Suction redging or mechanical excavation were selected as the most appropriate mea s t o effect removal of the sediments in question. Sedimentation structures nd siltation control systems would be a required component of either method.Dewatering systems would be needed to insure that the excavated sediments ould be disposed of onsite under the final cap. If the timing of the ex avation were to be delayed and the cap is complete before excavation, then ad off-site disposal location would be required. $ The capital cost estimate for excavation and on-site disposal 04 the sediments is from $2,650,000 (15,000 cubic yards) to $4,435,000 (45,000 cbbic yards). If these materials are disposed of offsite the coets will increase to an estimated total of between $4,150,000 (15,000 yde) and $8,935,000 (45,000 yds). Implementation of this alternative worlld result in a significant short term disturbance of this sensitive habitat. Time to 1mplement:b months Direct Capital CosU: $2,650,000 to $8,935,000 Estimated Annual Costa: None-Monitoring costs are included in Alt.#l Alternative 48: Earntern narsh channel Monitoring This alternative consists of the elements of Alternative 1: no action that involve monitoring and sampling of the Croton Marsh