Final Environmental Assessment for the Tamarack Managed Groundwater Recharge Project

• Description: relates to the Platte River Endangered Species Partnership ‎(aka Platte River Recovery Implementation Program or PRRIP)‎
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 8/3/1999
• Author: Colorado Division of Wildlife
• Title: Final Environmental Assessment ‎(EA)‎ fo rteh Tamarack Managed Groundwater Recharge Project at Tamarack Ranch State Wildlife Area and Pony Express State Area
• Water Supply Pro - Doc Type: Project Overview

V. ENVIRONMENTAL CONSEQUENCES
SOILS
Construction of the project should have very little if any long -term effects upon soil
conditions. A large portion of the project area is already under cultivation by the CDOW
on the TRSWA. Aside from temporary soil compaction there will be no impacts in those
farmed areas. Excavating pipeline trenches through upland sites will temporarily expose
and compact the soil. To lessen the potential erosion problems, disturbance to native
vegetation will be kept at a minimum. Re- seeding with appropriate grass mixtures will also
hasten the site recovery. Water erosion should not be a problem given the high percolation
and absorption rates for these sandy soils. Pond sites could potentially become blowouts
and should be managed to maintain some type of vegetative cover.
There are no Prime or Unique Farmlands on the TRSWA or the PESWA. A copy of the
NRCS clearance for prime and unique farmlands is included in Appendix D.
HYDROLOGY
The CDOW /CWCB /SPLRG Cooperative Project will elevate water tables in riparian
meadows, will increase groundwater return flows to the sloughs and river channels at the
SWAS's, and will generate open water surfaces at the recharge ponds. In turn, these
hydrological changes will serve to maintain and enhance existing riparian and wetland
habitats at the SWAS's in a manner that will benefit waterfowl and fish species of concern,
and will contribute to creation of needed wetland and wet meadow complexes.
Appendix A (Tab 3A of the Cooperative Agreement) describes the operational details and
the hydrologic analysis for Colorado's Tamarack Plan of managed groundwater recharge,
to which the CDOW /CWCB /SPLRG Cooperative Project will contribute. Groundwater
wells located next to the river at the SWAs will pump during periods of excess river flows.
These periods are defined as periods when flows exceed endangered species target flows
established by the U.S. Fish and Wildlife Service in central Nebraska and when South
Platte Compact requirements are satisfied. When the Tamarack Plan is implemented and
operated as described in Appendix A, Colorado is credited with contributing to the
reduction of water flow shortages in central Nebraska because these Tamarack Plan
operations are estimated to increase flows in the South Platte River at the Colorado -
Nebraska state line during the April through September time period by an average of
approximately 10,000 acre -feet each year over the flows that would otherwise occur during
that period. In addition, wells at the SWAs will also pump to re- regulate or recycle flows
that historically were not available, such as return flows from additional trans -basin
diversions or pumping of non - tributary aquifers to meet future population growth in the
South Platte Basin.
12