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2014-03-05_REVISION - M2006042
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2014-03-05_REVISION - M2006042
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Last modified
6/15/2021 6:00:18 PM
Creation date
3/7/2014 8:52:29 AM
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Template:
DRMS Permit Index
Permit No
M2006042
IBM Index Class Name
REVISION
Doc Date
3/5/2014
Doc Name
Revision CN01
From
MMM Partnership
To
DRMS
Type & Sequence
CN1
Email Name
PSH
Media Type
D
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No
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SOIL SURVEY <br />The South Platte River flows diagonally through the <br />county in a southwest to northeast direction. It drains the <br />area to the north and west through many intermittent <br />tributaries; the most important are Pawnee Creek, Lewis <br />Creek and Cedar Creek. Areas south and east of the <br />South Platte River dram mainly to the east into the <br />upper Frenchman tributary of the North Republican <br />River. In the northwest and northeast parts of the coun- <br />ty, natural dramageways are well defined, particularly by <br />the creeks that are entrenched into the underlying shale <br />formations and gravelly alluvium. The sandhill area paral- <br />leling the South Platte River on the south side has poorly <br />defined drainageways. <br />The valley of the South Platte River varies in width <br />from 1 mile to 4 miles_ Adjacent to the river are the <br />nearly level bottomlands and low terraces with fluctuat- <br />ing water tables at depths of 20 to 60 inches. The well <br />drained higher terraces, mainly on the north sale of the <br />river, are some of the best irrigated sods in the area <br />The larger tributaries, Pawnee, Lewis and Cedar <br />Greeks, have narrow valleys of loamy alluvial deposits <br />and enter the river from the north. Pawnee creek joins <br />the river near the town of Atwood, Cedar Creek between <br />Sterling and Iliff, and Lewis Creek between Iliff and <br />Proctor. <br />The area along the north side of the valley floor from <br />Sterling to the eastern county line is a nearly level to <br />strongly sloping, high lying old terrace deposit of <br />stratified alluvium mantled with loamy eolian materials. <br />This area is divided by many small drainageways that <br />flow toward the river in a southeasterly direction. <br />In the northern part of the county, the " Peetz Table," <br />as it is known locally, represents a separate physiographic <br />area in the form of a high, gently rolling plateau which <br />slopes eastward. In the southeastern part of the county, <br />the large "Kelley -Leroy Table" is a similar area with <br />respect to geology and topography. These plateaus are <br />underlain by calcareous sandstone and stratified sandy <br />and gravelly old alluvium. Both areas are mantled by a <br />thin loess deposit that has been reworked by water. <br />Bordering the Peetz Table on the southwest are the <br />steep to nearly vertical "Chimney and Lewis Canyons," <br />consisting of sdtstone exposures capped by calcareous <br />sandstone of the Ogallala Formation. Southeast of the <br />" Peetz Table" is a strongly sloping and steep area of red- <br />dish colored gravelly alluvium occurring as ridges and <br />resembling remnants of old high terraces. This is dis- <br />sected by many intermittent drainageways flowing to the <br />southeast. <br />In the northwest part of the county, mainly south of <br />the Chimney and Lewis Canyon area, is a nearly level to <br />moderately sloping area with deposits of materials <br />derived from siltstone and interbedded sandstone and <br />shale. Outcrops of shale and sdtstone are common in this <br />area, especially on ridges bordering intermittent <br />drainageways. <br />North and west of Sterling is a nearly level to <br />moderately sloping area that is mantled by a thin veneer <br />of loess and eolian calcareous sandy materials. <br />Paralleling the south side of the South Platte River is <br />an extensive, thick eolian sand deposit with dunelike <br />topography. This deposit grades into the tableland area in <br />the southeast part of the county. <br />Climate <br />The climate of Logan County is semiarid continental. <br />Because the county is separated from major sources of <br />moisture by large distances and mountain ranges, its cli- <br />mate is characterized by low humidity, wide variations in <br />precipitation and temperature, and abundant sunshine. <br />Logan County is usually warm in summer with <br />frequent hot days. The highest temperature occurs during <br />July and August. In winter, periods of very cold weather <br />are caused by Arctic air moving in from the north or <br />northeast. Cold periods alternate with milder periods that <br />occur often when westerly winds are warmed as they <br />move downslope. Most precipitation falls as rain during <br />the warmer part of the year and is normally heaviest in <br />late spring and early summer. Winter snowfalls are <br />frequent, but snow cover usually disappears during mild <br />periods. <br />The mean annual precipitation in Logan County ranges <br />from 13 inches in the western part to nearly 19 inches in <br />the eastern part. Most of the precipitation occurs during <br />the growing season, commonly as thunderstorms. Not all <br />of this precipitation is effective for plant growth because <br />of high runoff. <br />Table 1 gives data on temperature and precipitation for <br />Logan County, as recorded at Sterling for the period 1951 <br />to 1973. Table 2 shows probable dates of the first freeze <br />in fall and the last freeze in spring. Table 3 provides data <br />on length of the growing season. <br />In winter the average temperature is 27.5 degrees F, <br />and the average daily minimum is 13.7 degrees. The <br />lowest temperature on record, 29 degrees, occurred at <br />Sterling on February 1, 1951. In summer the average <br />temperature is 71 degrees, and the average daily max- <br />imum is 863 degrees. <br />Growing degree days, shown in table 3, are equivalent <br />to "heat units." During the month, growing degree days <br />accumulate by the amount that the average temperature <br />each day exceeds a base temperature. The normal <br />monthly accumulation is used to schedule single or succes- <br />sive plantings of a crop between the last freeze in spring <br />and the first freeze in fall. <br />Of the total annual precipitation, 12.27 inches, or 81 <br />percent, usually falls in April through September, which <br />includes the growing season for most crops. In 2 years <br />out of 10, the April- September rainfall is less than 10 <br />inches. The heaviest 1-day rainfall during the period of <br />record was 4.88 inches on August 15, 1968. Thun- <br />derstorms occur on about 45 days each year, and most <br />occur in June and July. <br />Average seasonal snowfall is 29.9 inches. The greatest <br />snow depth at any one time during the period of record <br />was 20 inches. On the average, 12 days have at least 1 <br />
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