PROJ00326

• Contract/PO #: C153498
• Contractor Name: U. S. Geological Survey
• Water District: 0
• County: Boulder
• Bill Number: SB 87-15
• Loan Projects - Doc Type: Contract Documents

CONTENTS

AbslIact ................................................................................................................................................................................ 1
Introduction .......................................................................................................................................................................... 1
Purpose and scope ...................................................................................................................................................... 2
Background ................................................................................................................................................................ 2
Specific-yield and specific-retention estimates from grain-size data ................................................................................... 4
Porosity estimates from geophysical logs ...................................,........................................................................................ 10

Quality-control errors ................................................................................................................................................. 10
Stochastic errors ................,.............................. ................................................ .......................................................... 11
Mean grain-density errors .......................................................................................................................................... II
Rugosity errors ..................................................................... ........... ........................ ................... ................................ 11
Porosity determination ............................................................................................................................................... 12
Specific-yield estimates from geophysical logs .........,............,............................................................................................ 13

Nuclear magnetism log ....... .............................. ......................................................................................................... 13
Effective-porosity log ................................................................................................................................................. 14
Apparent grain-density log ......................................................................................................................................... 15
Summary ................................... .......................................................................................,................................................... 18
References cited ................................................................................................................................................................... 18

FIGURES

1. Map showing location of test site .......................,.................................,................................................................... 3
2-8. Graphs showing:
2. Relations among specific yield, specific retention, porosity, and grain size .................................................. 4
3. Grain-size distribution for sample 57 .......................,..................................................................................... 5
4. Linear regression relation of specific retention on grain-size characteristics ................................................ 7
5. Relation of porosity from core samples and density porosity logs for holes C1 and CIA ............................ 12
6. Linear regression relation of specific yield on effective porosity .................................................................. 15
7. Linear regression relation of specific yield divided by porosity on apparent grain density........................... 16
8. Calculated specific-yield log and related caliper, gamma, resistivity, and porosity logs for a

200-foot interval in well USGS........,............................................................................................................. 17

TABLES

1. Regression equations and statistics for grain-size and specific-retention characteristics ......................................... 6
2. Mean specific retention measured by core analyses and calculated from the grain-size regression model
for a regression and a verification data set.................................................,.............................................................. 9
3. Mean specific yield from laboratory analyses of core, effective-porosity regression,
and apparent grain-density regression.... ,..................... .............................. ................. .... .......................................... 15

CONTENTS III