FLOOD08628

• County: Costilla
• Community: San Luis
• Stream Name: San Luis area drainageway
• Basin: Rio Grande
• Title: Master Drainage Study Town of San Luis
• Date: 12/1/1988
• Prepared For: San Luis
• Prepared By: WRC Engineering, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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During SCS investigation, the exact cause of the high water table
was not detennined although irrigation to the north of town was
believed to be a heavy contributor along with the high spring
snow melt runoff.

2. Investigation

On April 25 and 26, 1988, under the supervlslon of WRC, Custom Auger
Dri 11 i ng Company of Denver dri 11 ed 13 monitori ng well s at vari ous
locations throughout the Town of San Luis. These wells were
installed to gather base data for analyzing the community's
groundwater problems.

See Figure 3 - LOCATION OF MONITORING WELLS

The wells were drilled to depths of from 10 feet to 27 feet. Soil
logs and depths to ground water at the time of drilling are shown on
Figure 4 - LOGS OF MONITORING WELLS. At the time of drilling ground
water was present in all but three of the wells at depths of from 3
feet to 17 feet below the surface. The three wells that were dry
initially were drilled to a shallower depth then the other to
determine if the irrigation along the north end of town would create
a "perched" water table. Staff of the Costilla Conejos County
Cormnunity Act i on Agency were instructed on procedures for readi ng
the test wells and did so on a daily basis from the week of drilling
through the end of July, 1988. After August 1, readings were taken
on a weekly basis until the end of September, at which time they
were discontinued. The readings were mailed on a weekly basis to
WRC Engineering in Denver. Results of the readings are shown on
Fi gure 5A-5C - "DEPTH TO GROUND WATER - MONITORING WELLS". Twel ve
of the wells were cased with 2" PVC with the length of the
perforated portions of the pipe varying from between 5 feet and 12
feet depending on the depth of the well. In order to perform a
pumping test to detennine the characteristics and properties of the
aquifer, Well No. 10 was cased with 20 feet of 4" PVC 10' slotted
and 10' solid. All wells were cemented near the surZace and capped
with threaded caps. The soil logs indicated that the subsoils north

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