OF THE DESTINY BASIN,

WESTERN DESTINY COUNTY, COLORADO

UNITED STATES DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

GEOLOGY, GEOMORPHOLOGY, AND HYDROLOGY

OF THE DESTINY BASIN,

WESTERN DESTINY COUNTY, COLORADO

By

M. R. Osgood, D. L. Yancy, and P. K. Enloe

with a section on Engineering Geology and Hazards by A. S. Corbett

and a section on Economic Geology and Mineral Resources by R. T. Hollis

OPEN-FILE REPORT 88–614

Prepared in cooperation with the

COLORADO GEOLOGICAL SURVEY AND THE DESTINY COUNTY LAND USE DEPARTMENT

Denver, Colorado

1988

DEPARTMENT OF THE INTERIOR

Donald P. Hodel, Secretary

U.S. GEOLOGICAL SURVEY

Dallas L. Peck, Director

For sale by the Books and Open-File Reports Section, U.S. Geological Survey, Denver Colorado.

Any use of trade, product, or firm names in this report is for descriptive purposes only and does not imply endorsement by the U.S. Government.

CONTENTS

Abstract……………………………………………………………………………………………………………..

1. Introduction………………………………………………………………………………………………………………………………….

 Purpose and scope…………………………………………………………………………………………………………………………..

 Previous investigations……………………………………………………………………………………………………………………

 Location and access…………………………………………………………………………………………………………………………

 Physiography and climate………………………………………………………………………………………………………………..

2. Geologic Setting…………………………………………………………………………………………………………………………..

 Precambrian basement rocks……………………………………………………………………………………………………………

 Structural geology…………………………………………………………………………………………………………………………..

 Tertiary and Quaternary history……………………………………………………………………………………………………….

3. Surficial Geology and Glacial History……………………………………………………………………………………………

 Alpine glaciation…………………………………………………………………………………………………………………………….

 Till and moraine deposits…………………………………………………………………………………………………………………

 Periglacial and mass-wasting deposits………………………………………………………………………………………………

4. Geomorphic Evolution of the Basin……………………………………………………………………………………………….

 Erosional benches……………………………………………………………………………………………………………………………

 Stream terraces and incision history…………………………………………………………………………………………………

5. Hydrology and Water Resources……………………………………………………………………………………………………

 Surface water………………………………………………………………………………………………………………………………….

 Ground water………………………………………………………………………………………………………………………………….

 Water quality………………………………………………………………………………………………………………………………….

6. Engineering Geology and Geologic Hazards………………………………………………………………………………….

 Slope stability…………………………………………………………………………………………………………………………………

 Flood hazards………………………………………………………………………………………………………………………………….

 Seismic considerations…………………………………………………………………………………………………………………….

 Foundation and excavation conditions………………………………………………………………………………………………

7. Economic Geology and Mineral Resources……………………………………………………………………………………

 Gold and silver………………………………………………………………………………………………………………………………..

 Molybdenum…………………………………………………………………………………………………………………………………..

 Rare earth elements…………………………………………………………………………………………………………………………

 Resource significance and limitations……………………………………………………………………………………………….

8. Land Use and Development Considerations…………………………………………………………………………………..

9. Summary and Conclusions……………………………………………………………………………………………………………

10. Recommendations for Further Study……………………………………………………………………………………………

Acknowledgments………………………………………………………………………………………………..

References Cited………………………………………………………………………………………………….

Appendix A. Measured Stratigraphic Sections……………………………………………………………………………………

Appendix B. Soil Descriptions………………………………………………………………………………………………………….

Appendix C. Streamflow and Water-Quality Data……………………………………………………………………………..

Appendix D. Selected Well Records………………………………………………………………………………………………….

Appendix E. Description of Map Units……………………………………………………………………………………………..

Appendix F. Glossary of Terms………………………………………………………………………………………………………..

Appendix G. Selected Climate Data………………………………………………………………………………………………….

Appendix H. Index to Aerial Photography…………………………………………………………………………………………

Appendix I. Selected Field Photograph Log……………………………………………………………………………………….

Appendix J. Agencies and Offices Consulted…………………………………………………………………………………….

ILLUSTRATIONS

PLATES

Plate 1. Geologic map of the Destiny basin and adjacent areas……………………………………………………………

Plate 2. Map showing surficial deposits and geomorphic units……………………………………………………………

Plate 3. Map showing geologic hazards and areas of engineering concern……………………………………………

Plate 4. Map showing mineral occurrences and geochemical sample localities…………………………………….

FIGURES

Figure 1. Index map showing location of the Destiny basin, Destiny County, Colo………………………………

Figure 2. Generalized physiographic diagram of the study area…………………………………………………………..

Figure 3. Precambrian basement terrane map, northern Front Range…………………………………………………..

Figure 4. Schematic structural cross section, A–A′…………………………………………………………………………….

Figure 5. Correlation of glacial deposits, Middle St. Vrain drainage……………………………………………………

Figure 6. Photograph of lateral moraine crest near the basin mouth…………………………………………………….

Figure 7. Diagram of erosional bench sequence and inferred formative processes………………………………..

Figure 8. Longitudinal profile of the main stem, Destiny Creek………………………………………………………….

Figure 9. Hydrograph, gaging station 06724500, 1988 water year……………………………………………………….

Figure 10. Piper diagram of ground-water and surface-water chemistry………………………………………………

Figure 11. Slope-stability hazard classification map (schematic)…………………………………………………………

Figure 12. Flood-prone area sketch, lower basin reach……………………………………………………………………….

TABLES

Table 1. Summary of Precambrian rock units…………………………………………………………………………………….

Table 2. Radiocarbon and relative-age control on Quaternary deposits………………………………………………..

Table 3. Streamflow summary statistics, principal gaging stations………………………………………………………

Table 4. Selected ground-water quality analyses………………………………………………………………………………..

Table 5. Engineering properties of surficial map units………………………………………………………………………..

Table 6. Slope-stability classification criteria…………………………………………………………………………………….

Table 7. Summary of selected geochemical sample results…………………………………………………………………

Abstract

The Destiny basin occupies the upper reaches of Destiny Creek, a tributary of the Middle St. Vrain Creek in western Destiny County, Colorado, between the towns of Allenspark and Ward. This investigation documents the regional geology, surficial deposits, geomorphic evolution, hydrology, engineering characteristics, and natural hazards affecting the basin and adjacent uplands. Field investigations conducted during 1986–88 indicate that repeated alpine glaciation, subsequent stream incision, and differential weathering of Precambrian crystalline rocks produced a sequence of erosional benches that now support the majority of human development within the basin. The principal stream of the basin, Destiny Creek, originates at Lake Destiny in the upper basin and flows generally southward through the community of Destiny before leaving the mapped study area at the southern basin boundary and continuing approximately 3.8 mi (6.1 km) downstream to its confluence with the Middle St. Vrain Creek. Throughout this report, the stream is referred to interchangeably as Destiny Creek and the main stem.

Bedrock in the study area consists chiefly of Precambrian biotite gneiss, migmatite, and subordinate bodies of the Boulder Creek Granodiorite, cut by northeast-trending shear zones that exert strong control on drainage orientation and on the distribution of mass-wasting deposits. At least two, and probably three, episodes of alpine glaciation are recorded by nested end and lateral moraines in the lower basin; the extent and relative-age relations of these deposits are broadly correlative with the Bull Lake and Pinedale glaciations recognized elsewhere in the Colorado Front Range.

Surface water in the basin is perennial along the main stem and principal tributaries, with peak discharge typically occurring in late May or early June in response to snowmelt. Ground water is present in fractured bedrock and in unconsolidated valley-fill deposits, and is used locally for domestic and small-scale commercial supply. Water-quality characteristics are generally favorable, though locally elevated concentrations of dissolved iron and manganese are noted in samples from valley-fill wells near the basin axis.

Engineering geologic conditions are strongly influenced by the erosional bench topography described herein. Commercial and residential development is concentrated upon the middle and lower benches, which are underlain by moderately well-drained till and colluvium of generally favorable engineering character; locally, however, steep bench margins are subject to shallow debris slides, and localized channel-margin erosion or inundation may occur in narrow low-lying reaches adjacent to the main stem. A supplemental reconnaissance geochemical survey identified anomalous concentrations of gold and silver associated with shear-zone-hosted quartz veins, a soil-geochemical molybdenum anomaly in the upper basin suggestive of a concealed porphyry-style system, and rare-earth-element enrichment in pegmatite bodies along the western basin divide; these occurrences are of reconnaissance-level interest but have not been evaluated for economic significance. These findings contribute to ongoing geologic mapping and hazard-assessment efforts throughout the northern Front Range.

1. Introduction

Purpose and Scope

This report presents the results of geologic, geomorphic, and hydrologic investigations conducted in the Destiny basin, a small drainage tributary to the Middle St. Vrain Creek in western Destiny County, Colorado. The work was undertaken as part of a cooperative program between the U.S. Geological Survey, the Colorado Geological Survey, and the Destiny County Land Use Department to provide a geologic and hydrologic framework for land-use planning, water-resource management, and hazard mitigation in rapidly developing portions of the montane and subalpine Front Range.

Specific objectives of the investigation were to (1) describe and map the distribution of bedrock and surficial units within the basin; (2) reconstruct the late Quaternary glacial and geomorphic history of the basin, with particular reference to the erosional bench topography upon which most existing development is sited; (3) characterize surface-water and ground-water resources, including seasonal variability and general water-quality conditions; and (4) evaluate geologic hazards, including slope instability, flooding, and foundation conditions, that bear upon existing and anticipated land use.

Previous Investigations

Reconnaissance geologic mapping of the northern Front Range crystalline core, including areas adjacent to the present study area, was conducted during the course of regional mapping programs extending from the 1950’s through the 1970’s. Glacial geology of the nearby Wild Basin and Indian Peaks areas has received considerable attention owing to their proximity to Rocky Mountain National Park and the Indian Peaks Wilderness Area, and the present study draws upon established regional correlations for glacial deposits of Bull Lake and Pinedale age. Hydrologic data for the Middle St. Vrain drainage have been collected intermittently at gaging stations operated in cooperation with local water conservancy districts. No previous investigation, however, has specifically addressed the Destiny basin at the scale presented in this report.

Location and Access

The Destiny basin lies in western Destiny County, Colorado, approximately 6 mi (10 km) south of Allenspark and 5 mi (8 km) north-northwest of Ward, within the drainage divide separating tributaries of the Middle St. Vrain Creek from tributaries entering the North St. Vrain drainage to the north. The basin is accessible by way of a paved secondary road (locally designated Route 11) extending southward from its junction with State Highway 7 near Allenspark, and by an improved gravel road (locally designated Route 385) entering the basin from the west. A network of unpaved county and forest roads provides access to outlying portions of the basin, including areas in the vicinity of Hidden Lake and Bark Ranch to the east.

The basin ranges in altitude from approximately 8,400 ft (2,560 m) at its lowest point along the main stem to more than 11,200 ft (3,410 m) along divides shared with Meadow Mountain, St. Vrain Mountain, and unnamed ridges extending toward Taylor Mountain and Coffintop Mountain to the northeast. The community of Destiny, the principal center of population and commerce within the basin, is situated near the confluence of the main stem and its principal western tributary, at an altitude of approximately 8,600 ft (2,620 m).

The principal stream of the basin, Destiny Creek, originates at Lake Destiny in the upper basin and flows generally southward through the community of Destiny before leaving the mapped study area at the southern basin boundary and continuing approximately 3.8 mi (6.1 km) downstream to its confluence with the Middle St. Vrain Creek. Throughout this report, the stream is referred to interchangeably as Destiny Creek and the main stem.

Physiography and Climate

The study area lies within the Southern Rocky Mountain physiographic province, characterized by high-relief crystalline terrane deeply incised by glacial and fluvial processes. Local relief within the basin exceeds 2,800 ft (850 m). Vegetation grades from lodgepole pine and Engelmann spruce–subalpine fir forest at lower and middle altitudes to krummholz and alpine tundra above approximately 11,000 ft (3,350 m).

Climate is typical of the montane to subalpine Front Range, with a pronounced winter snowpack that persists at higher altitudes into early summer. Mean annual precipitation, estimated from regional climate stations and orographic adjustment, is on the order of 24 to 30 in (610 to 760 mm), the greater part of which falls as snow between October and May. Mean annual temperature at the altitude of the Destiny townsite is estimated at approximately 38°F (3°C), with a frost-free season generally shorter than 60 days.

Snowpack accumulation typically begins in late September at the highest altitudes within the basin and by early November at the elevation of the townsite. Maximum snow-water equivalent, estimated by extrapolation from regional snow-course records at comparable altitude and aspect, is on the order of 14 to 18 in (36 to 46 cm) on north-facing slopes near the middle bench and considerably greater in cirque headwalls and lee-slope drift accumulations near the basin divide. Snowmelt is generally complete at the altitude of the townsite by late May, though patches of drifted snow persist in shaded, north-facing localities near the upper bench into June in years of above-average accumulation.

Wind is a significant factor in the redistribution of snow within the basin, particularly along exposed ridges and saddles connecting toward Meadow Mountain and Taylor Mountain, where persistent westerly and northwesterly winds strip snow from windward slopes and deposit it as cornices and drift accumulations on lee slopes. This redistribution has an important, though incompletely quantified, effect on the timing and magnitude of local snowmelt recharge to both surface water and shallow ground water, as discussed further in section 5.

Field Methods

Geologic mapping presented in this report was compiled at a scale of 1:12,000 in the field and subsequently reduced for publication at 1:24,000 (pl. 1, pl. 2). Mapping relied upon a combination of traverse-based field observation, interpretation of 1:24,000-scale, black-and-white aerial photography flown in September 1987 and August 1988, and limited hand-auger and test-pit exposures excavated at selected localities to characterize surficial deposits away from natural exposures. Approximately 40 person-days of field mapping were conducted during the 1987 and 1988 field seasons, supplemented by several days of reconnaissance mapping in the Bark Ranch upland during late 1988.

Streamflow and water-quality data were collected in cooperation with local well owners and with the operator of the partial-record gaging station near the basin mouth; methods of data collection and analysis follow standard procedures for surface-water and ground-water investigations current at the time of the study and are not repeated in detail in this report. Well records presented in appendix D were compiled from driller’s logs on file with the Colorado Division of Water Resources, supplemented by limited field verification of static water level and estimated yield at a subset of wells.

2. Geologic Setting

Precambrian Basement Rocks

Bedrock exposed throughout the study area is entirely of Precambrian age and consists chiefly of banded biotite gneiss and migmatitic gneiss of probable Early Proterozoic age, intruded by tabular to irregular bodies of the Boulder Creek Granodiorite (Early Proterozoic). Subordinate lithologies include amphibolite, biotite schist, and localized pegmatite and aplite dikes associated with the granodiorite intrusive episode. A summary of principal rock units recognized in the study area is given in table 1.

The gneissic rocks display a well-developed foliation that strikes generally northeast and dips moderately to steeply northwest, broadly parallel to the regional structural grain of the northern Front Range. Compositional layering within the gneiss, interpreted as relict bedding or transposed layering of a sedimentary or volcanic protolith, is locally disrupted by boudinage and small-scale isoclinal folds, attesting to a complex Precambrian deformational history involving at least two, and probably three, phases of ductile deformation prior to intrusion of the Boulder Creek Granodiorite.

The Boulder Creek Granodiorite forms a series of elongate, northeast-trending plutons and sills within the study area, weathering to form the more resistant ridges and cliff bands along basin margins, including the prominent bedrock exposures below Meadow Mountain and St. Vrain Mountain. Where deeply weathered, the granodiorite disaggregates to grus, a coarse, sandy saprolite that mantles many gentle slopes and forms an important parent material for surficial deposits described in section 3.

Structural Geology

The dominant structural fabric of the study area is a northeast-striking foliation and associated shear-zone system inherited from Precambrian ductile deformation and subsequently reactivated, at least locally, during Laramide and younger brittle deformation. Several northeast-trending shear zones, ranging from a few feet to several tens of feet in width, are marked by zones of intense fracturing, chloritic alteration, and, locally, thin zones of fault gouge. These shear zones exert a first-order control on the orientation of the main stem and principal tributaries of the Destiny basin, which follow a markedly rectilinear, structurally controlled drainage pattern (fig. 4).

A subordinate set of northwest-trending fractures and small-displacement faults is also present, most conspicuously expressed in the linear valley occupied by Hidden Lake and in the alignment of several short tributary drainages east of the main townsite. No evidence of Holocene displacement was observed on any structure mapped within the study area, and the basin is not known to lie within an active seismic source zone; regional seismic hazard is discussed further in section 6.

Fracture-density measurements made at 14 stations distributed throughout the mapped area indicate a systematic increase in fracture intensity within approximately 50 to 100 ft (15 to 30 m) of mapped shear-zone traces, with fracture spacing commonly less than 2 in (5 cm) immediately adjacent to shear-zone cores and increasing to more than 12 in (30 cm) in unaffected bedrock. This relation is of practical significance in the siting of wells intended to intersect fracture-controlled ground water, discussed further in section 5, and in the evaluation of rock-cut stability discussed in section 6.

Joint sets recognized throughout the study area include, in addition to the shear-zone-related fracture fabric described above, a well-developed set of gently dipping, sheet-like joints attributed to unloading (exfoliation) related to erosional removal of overburden, best developed on broad, domal bedrock exposures near the head of the basin. These exfoliation joints locally control the detachment of large tabular rock slabs, several examples of which were observed as talus blocks on colluvial slopes below cliff exposures of the Boulder Creek Granodiorite.

Tertiary and Quaternary History

Following a lengthy interval of Laramide uplift and subsequent erosion, the northern Front Range was subjected to renewed regional uplift during the late Tertiary, accompanied by deep incision of the ancestral drainage network and establishment of the present major topographic elements of the range. Remnants of a high-altitude, low-relief erosion surface, tentatively correlated with the regional Rocky Mountain (Eocene) or Sherman (early Tertiary) erosion surfaces recognized elsewhere in the Front Range, are preserved on isolated summit areas near Meadow Mountain and along the divide toward Taylor Mountain, though no detailed study of this surface was undertaken as part of the present investigation.

The Quaternary history of the basin is dominated by the effects of repeated alpine glaciation, discussed in detail in section 3, and by subsequent postglacial stream incision that produced the erosional bench sequence described in section 4. This bench sequence forms the principal geomorphic control on the distribution of soils, ground-water occurrence, and land use within the basin.

Metamorphic History

The gneissic rocks of the study area record at least two, and in places three, distinguishable episodes of metamorphic recrystallization, based on cross-cutting relations among foliation-defining minerals, porphyroblast growth, and later retrograde alteration. An early, high-grade event, attaining upper amphibolite facies conditions, is recorded by coarse biotite-sillimanite-garnet assemblages preserved in the cores of larger gneiss bodies away from the influence of later intrusion. This assemblage is locally overprinted by a lower-grade, greenschist- to lower-amphibolite-facies event associated with intrusion of the Boulder Creek Granodiorite and with movement along the northeast-trending shear zones described below, during which chlorite and epidote commonly replace earlier biotite and garnet along shear-zone margins.

Retrograde alteration is most pronounced within and immediately adjacent to mapped shear zones, where original gneissic fabric is progressively transposed into a fine-grained, chlorite-rich mylonitic fabric over zones as much as several tens of feet wide. This retrograde mineral assemblage, being generally softer and more susceptible to weathering than unaltered gneiss, exerts an important control on the distribution of colluvial and talus deposits discussed in section 3, and on the location of several observed slope failures discussed in section 6.

Contact Relations

Contacts between the Boulder Creek Granodiorite and enclosing gneiss are generally sharp, and in most exposures examined during this study are intrusive, marked by a narrow zone, typically less than 3 ft (1 m) wide, of finer-grained, chilled granodiorite and, locally, thin screens of partially assimilated gneiss. Along the margins of several of the larger granodiorite bodies, particularly in exposures near the western basin divide toward Meadow Mountain, a broader zone of migmatitic gneiss, showing evidence of partial melting and injection by granodioritic material, separates unequivocally intrusive granodiorite from unaffected gneiss farther from the contact. This migmatitic zone, mapped separately at a reconnaissance level during this study but not shown as a distinct unit on plate 1, is interpreted to record synmetamorphic partial melting broadly contemporaneous with granodiorite emplacement.

Geochronology

No radiometric age determinations were made specifically for this study; inferred ages for Precambrian units are based on established regional correlations with dated rock units of the northern Front Range described in previous investigations (Braddock and Cole, 1979; Ward and Cole, 1988). On the basis of these regional correlations, the older gneissic rocks of the study area are inferred to be of Early Proterozoic age, broadly correlative with basement rocks dated elsewhere in the Front Range at approximately 1,700 to 1,750 million years, and the Boulder Creek Granodiorite is inferred to be of Early Proterozoic age, broadly correlative with granodiorite bodies dated elsewhere in the range at approximately 1,700 million years. These age assignments should be regarded as provisional pending direct radiometric study of samples from the Destiny basin itself.

Regional Comparison

The Precambrian terrane exposed within the Destiny basin is broadly continuous with, and lithologically similar to, basement rocks mapped in the vicinity of Bald Mountain and Coffintop Mountain to the northeast, and with rocks exposed farther south near the historic mining districts of Jamestown, Gold Hill, and Sunshine. No evidence of past prospecting or mining activity predating the present investigation was observed during fieldwork, and unlike these southern districts the Destiny basin has no documented mining history. Quartz veining associated with the shear zones described above, however, was found on follow-up sampling to be locally accompanied by anomalous concentrations of gold, silver, and, in the upper basin, molybdenum, together with rare-earth-element enrichment in associated pegmatite bodies; these occurrences are described in detail in section 7 (Economic Geology and Mineral Resources).

Unit	Lithologic description	Inferred age
Xbg	Banded biotite gneiss, migmatitic in part; local amphibolite lenses	Early Proterozoic
Ybc	Boulder Creek Granodiorite; medium- to coarse-grained, weakly foliated	Early Proterozoic
Yp	Pegmatite and aplite dikes, generally < 10 ft thick	Early Proterozoic
Xa	Amphibolite, fine-grained, in lenses and layers within Xbg	Early Proterozoic

Table 1. Summary of Precambrian rock units, Destiny basin.

3. Surficial Geology and Glacial History

Alpine Glaciation

The Destiny basin was occupied by alpine glacier ice during at least two, and probably three, distinct glacial episodes during the Pleistocene. The most extensive glaciation, tentatively correlated with the Bull Lake glaciation of regional usage, is recorded by subdued, deeply weathered morainal ridges preserved at and beyond the present basin mouth, near the confluence with the Middle St. Vrain drainage. Deposits of this age are characterized by thoroughly weathered, grus-mantled boulders and a well-developed argillic soil horizon substantially thicker than that developed on younger deposits.

A less extensive, better-preserved glaciation, correlated with the Pinedale glaciation, is recorded by a well-defined sequence of lateral and end moraines extending from the vicinity of Brainard Lake, along the western basin margin, to a terminal position approximately 1.5 mi (2.4 km) upvalley from the present townsite of Destiny. Moraine crests of this age retain a distinctly hummocky, kettled surface morphology and support only weak soil development, consistent with a late Pleistocene age.

A restricted zone of even younger, sharp-crested moraines occupies cirque basins near the head of the drainage, below unnamed ridges connecting toward Taylor Mountain; these deposits are tentatively assigned to a Neoglacial (latest Pleistocene to Holocene) episode of limited ice advance and are not discussed further in this report, as they lie almost entirely above the zone of present-day development.

Till and Moraine Deposits

Till deposits of both principal glaciations consist of poorly sorted, unstratified mixtures of angular to subangular boulders, cobbles, and gravel in a sandy to silty matrix derived from local gneiss and granodiorite bedrock. Till of Pinedale age is generally more permeable and less deeply weathered than till of Bull Lake age, and forms the parent material for soils of generally favorable engineering character described in section 6 and appendix B.

Ground moraine and till-mantled bedrock underlie extensive areas of the middle and lower basin, including much of the ground upon which the Destiny townsite and outlying development are situated. Where till thickness exceeds approximately 15 ft (4.6 m), as inferred from scattered well logs (appendix D), shallow ground water is locally perched within the till above less permeable weathered bedrock or basal till.

Till of the middle bench (unit Qtp) is typically 15 to 40 ft (4.6 to 12 m) thick, on the basis of well and test-pit penetration, and consists of a matrix-supported mixture of subangular boulders and cobbles, commonly 20 to 40 percent by volume, in a sandy silt matrix. Till of the upper bench (unit Qtb), by contrast, is generally thinner where preserved, more discontinuous in distribution, and displays a substantially more developed weathering profile, including a reddish-brown, clay-enriched horizon as much as 3 ft (0.9 m) thick at several localities examined in appendix A. This difference in weathering-profile development is among the principal lines of evidence supporting assignment of the two till sheets to distinct, non-correlative glacial episodes.

Boulder lithology within both till sheets is dominated by locally derived gneiss and granodiorite, with only rare, far-traveled erratics of lithology inconsistent with local bedrock; this observation is consistent with the relatively short transport distance implied by the modest reconstructed length of the Pinedale-correlative glacier discussed later in this section.

Periglacial and Mass-Wasting Deposits

Talus and colluvial aprons derived from periglacial frost-riving of bedrock cliff bands mantle many steep slopes, particularly below exposures of the Boulder Creek Granodiorite. Coarse, poorly sorted colluvium of this type is generally unstable on slopes exceeding about 30 degrees and is a principal consideration in the slope-stability hazard classification presented in section 6.

Small rock-glacier-like deposits, interpreted as relict periglacial features of latest Pleistocene age, are present in several north-facing cirques near the head of the basin. These deposits are not presently active but retain sufficient interstitial ice or ice-cemented sediment in their cores to be treated with caution with respect to any excavation or foundation work in their immediate vicinity, notwithstanding their considerable distance from existing development.

Figure 5. Correlation of glacial deposits, Middle St. Vrain drainage, showing relative-age relations among till units discussed in text. [Figure not reproduced in this file.]

Extent and Thickness of Former Ice

The maximum extent of Pinedale-correlative ice within the basin is delimited by a well-preserved terminal moraine complex approximately 1.5 mi (2.4 km) upvalley from the Destiny townsite, described in the preceding subsection. Reconstructed ice-surface profiles, based on the altitude of lateral moraine crests preserved along the basin walls between this terminal position and the vicinity of Brainard Lake, indicate a former ice thickness on the order of 400 to 550 ft (120 to 170 m) near the equilibrium-line altitude of the glacier, thinning to a few tens of feet near the terminus. The reconstructed Pinedale-correlative glacier is estimated to have had a length of approximately 3.2 mi (5.1 km) and to have occupied essentially the entire upper two-thirds of the present basin above the townsite.

Ice of the older, Bull Lake-correlative glaciation extended at least to, and probably somewhat beyond, the present basin mouth, on the basis of deeply weathered morainal remnants identified beyond the limit of Pinedale ice near the confluence with the Middle St. Vrain drainage. The precise former extent of this older glaciation could not be established with confidence during the present study owing to the discontinuous and deeply weathered character of surviving deposits, and is shown only diagrammatically on plate 2.

Glacial Erratics and Striated Surfaces

Scattered glacial erratics, consisting of granodiorite and gneiss boulders as much as 8 ft (2.4 m) in maximum dimension, are present on bedrock surfaces well beyond the limit of Pinedale-correlative moraine, particularly on gently sloping bedrock benches flanking the lower basin. Several bedrock surfaces exposed beneath thin till cover near the mouth of the basin preserve well-developed glacial striae and grooves, generally trending N. 50°–60° E., parallel to the inferred direction of former ice flow and broadly consistent with the northeast-trending structural grain of the basin described in section 2. Striated surfaces are best preserved on fine-grained gneiss and are largely absent, owing to more rapid post-glacial weathering, on exposures of coarser-grained granodiorite.

Eolian Deposits

A thin, discontinuous mantle of fine-grained eolian sediment, generally less than 12 in (30 cm) thick, was observed locally on gentle, wind-exposed surfaces of the upper and middle benches, most notably on the broad upland east of the main basin near Bark Ranch. This material, tentatively interpreted as loess or reworked loessial silt derived from valley-fill and outwash sources during periods of reduced vegetative cover in the late Pleistocene or early Holocene, was not mapped as a separate unit but locally contributes a silt-enriched surface horizon to soils otherwise developed on till or grus, as noted in appendix B.

4. Geomorphic Evolution of the Basin

Erosional Benches

The most distinctive geomorphic feature of the Destiny basin is a flight of at least three, and locally four, erosional benches developed on the valley walls flanking the main stem and its principal tributaries. These benches, informally designated in ascending order as the lower, middle, and upper benches, are interpreted as remnants of former valley floors or glacial trough shoulders that have been progressively abandoned as the main stem incised its channel in response to base-level lowering and differential removal of weathered bedrock and till.

The lower bench, standing approximately 15 to 30 ft (4.6 to 9.1 m) above the present channel of the main stem, is developed almost entirely on Pinedale-age till and outwash and is the most areally restricted of the bench sequence, generally confined to a narrow zone immediately flanking the active floodplain. The middle bench, standing approximately 40 to 70 ft (12 to 21 m) above the channel, is the most extensive of the sequence and is developed on a combination of till, weathered bedrock, and colluvial apron deposits; commercial development within the Destiny townsite is concentrated almost entirely upon this middle bench, which affords a combination of relatively gentle slope, favorable drainage, and reduced exposure to flood hazard relative to the valley floor. The upper bench, standing more than 90 ft (27 m) above the channel in most locations, is developed principally on deeply weathered bedrock and Bull Lake-age till and is less extensively utilized for development, owing in part to steeper access grades and more limited availability of shallow ground water.

The origin of the bench sequence is attributed to a combination of factors, including differential resistance of variably weathered bedrock and till to fluvial and periglacial erosion, minor structural control exerted by the northeast-trending shear-zone fabric described in section 2, and probable episodic base-level adjustments related to the glacial and deglacial history of the trunk Middle St. Vrain drainage. A schematic diagram of the bench sequence and inferred formative processes is presented in figure 7.

Stream Terraces and Incision History

In addition to the bedrock- and till-cored erosional benches described above, a lower flight of fill-cut and fill terraces is developed in unconsolidated valley-fill deposits flanking the present floodplain of the main stem. These terraces record a succession of postglacial aggradation and incision events, probably related to climatically controlled variation in sediment supply and discharge during the latest Pleistocene and Holocene.

The longitudinal profile of the main stem (fig. 8) displays a series of subtle knickpoints coincident with crossings of the northeast-trending shear zones described in section 2, suggesting that structural control, in addition to glacial and climatic factors, has influenced the rate and pattern of postglacial incision. Continued slow incision of the main stem channel is inferred from the height and degree of dissection of the lowest terrace surfaces, and should be considered in the evaluation of long-term stability of streamside structures, as discussed further in section 6.

Knickpoints and Base-Level Control

Three principal knickpoints are recognized along the longitudinal profile of the main stem within the mapped area, at approximately river miles 1.4, 2.6, and 3.9 measured upstream from the basin mouth. Each of these knickpoints coincides closely with the mapped trace of a northeast-trending shear zone, and each is associated with a locally steepened channel gradient and, in two of the three cases, a small bedrock-controlled cascade or series of cascades. No knickpoint of comparable magnitude was observed at localities lacking mapped structural control, supporting the interpretation that differential resistance of sheared versus unsheared bedrock, rather than base-level forcing from the trunk Middle St. Vrain drainage alone, is primarily responsible for the persistence of these features.

The lowermost knickpoint, near river mile 1.4, is interpreted to mark the effective upstream limit of adjustment to postglacial base-level change transmitted from the Middle St. Vrain trunk stream; channel gradient and bench height above the channel both increase gradually but systematically upstream of this point, consistent with a wave of incision that has not yet fully propagated through the upper basin.

Correlation with Adjacent Drainages

A broadly similar, though less well-developed, sequence of erosional benches is recognizable in reconnaissance observations of small tributary drainages entering the Middle St. Vrain from the west, between the Destiny basin and Allenspark, suggesting that the processes responsible for bench formation within the Destiny basin operated at a scale broader than this basin alone, probably in response to regional postglacial adjustment of the Middle St. Vrain trunk drainage following retreat of Pinedale-correlative ice. A more detailed comparison of bench elevations and ages among these adjacent drainages was beyond the scope of the present study and is recommended as a subject for further investigation (see section 10).

Geomorphology of the Bark Ranch Upland

East of the main Destiny basin, beyond the drainage divide separating it from tributaries flowing toward Jamestown, lies a broad, gently rolling upland informally referred to locally as the Bark Ranch upland, underlain chiefly by deeply weathered granodiorite grus (unit Ybc) with a thin, discontinuous eolian mantle discussed in section 3. This upland lacks the well-defined bench sequence developed within the main Destiny basin, and instead displays a more subdued, rounded topography interpreted to reflect its position largely above the limit of Pleistocene alpine glaciation and its correspondingly longer exposure to subaerial weathering and grus-forming processes. Scattered low-relief swales and shallow closed depressions on this upland, some containing small ephemeral ponds, are tentatively interpreted as deflation hollows or solution-widened joint intersections rather than glacial or fluvial features.

5. Hydrology and Water Resources

Surface Water

The main stem of the Destiny basin and its principal tributaries are perennial throughout their lower and middle reaches, sustained during the summer and fall by baseflow derived from bedrock fracture systems and from ground water stored in valley-fill and till deposits. Discharge is strongly seasonal, with peak flows typically occurring during snowmelt in late May or early June and minimum flows occurring during late winter, prior to the onset of snowmelt.

A partial-record gaging station (locally designated station 06724500) has been operated intermittently near the basin mouth since 1979. Summary statistics for the period of record are presented in table 3. Peak instantaneous discharge of record, 340 ft3/s (9.6 m3/s), occurred during snowmelt runoff in June 1983; a period of unusually rapid snowmelt combined with a rain-on-snow event was responsible for this peak, which substantially exceeded flows recorded in other years of the gaging record.

Statistic	Value	Water year(s)
Period of record	1979–88 (intermittent)	—
Mean annual discharge	18.4 ft3/s	1979–88
Maximum peak discharge	340 ft3/s	1983
Minimum daily discharge	1.1 ft3/s	1981
Approx. date of peak flow (typical)	Late May–early June	—

Table 3. Streamflow summary statistics, principal gaging station near basin mouth.

Ground Water

Ground water in the study area occurs under water-table conditions in unconsolidated valley-fill and till deposits and under fracture-controlled conditions in Precambrian bedrock. Yields to domestic wells completed in valley-fill deposits along the middle bench, where the Destiny townsite is situated, typically range from about 3 to 15 gal/min, sufficient for domestic and small-scale commercial supply but generally inadequate for large-scale irrigation or municipal use without well-field development.

Wells completed in fractured bedrock, particularly those intersecting the northeast-trending shear zones described in section 2, locally yield substantially higher rates, in a few cases exceeding 25 gal/min; well yields elsewhere in unfractured gneiss or granodiorite are typically low, commonly less than 2 gal/min. Selected well records are summarized in appendix D.

Water Quality

Surface water and ground water within the basin are generally of the calcium bicarbonate type, consistent with derivation from silicate bedrock with minimal contribution from evaporite or carbonate sources (fig. 10). Dissolved-solids concentrations are low, generally less than 150 mg/L, reflecting short residence time and limited water-rock interaction typical of high-altitude crystalline terrane.

Locally elevated concentrations of dissolved iron and manganese, in some instances exceeding secondary drinking-water standards, were noted in ground-water samples from several wells completed in valley-fill deposits near the basin axis, probably reflecting reducing conditions in organic-rich fine-grained sediment. No sample collected during this investigation exceeded primary drinking-water standards for any constituent analyzed. Selected water-quality analyses are presented in appendix C and table 4.

Seasonal Variation in Streamflow

Streamflow within the basin displays a pronounced and highly repeatable seasonal pattern dominated by snowmelt. Discharge typically begins to rise above winter base-flow levels in early to mid-April, increases rapidly through May, and reaches an annual peak in late May or early June, coincident with the period of most rapid snowmelt at middle and upper altitudes within the basin. Following the snowmelt peak, discharge recedes through a series of minor secondary peaks associated with residual snowmelt at higher altitudes and, in some years, with summer convective precipitation, before declining to a prolonged winter base-flow period extending from approximately November through March. Base flow during this winter period is sustained almost entirely by ground-water discharge from fractured bedrock and valley-fill deposits.

Springs

Numerous small springs, most with estimated discharge of less than 5 gal/min, were noted during fieldwork at the contact between till or colluvium and less permeable underlying bedrock, particularly along the base of the middle and upper bench margins. Several of these springs are used for domestic supply by individual landowners, typically by means of a spring box and buried pipeline rather than a drilled well. Spring discharge was observed to fluctuate seasonally in sympathy with snowmelt recharge, with several of the smaller springs noted during fieldwork to be substantially reduced or intermittent by late summer in years of below-average snowpack.

Ground-Water Recharge

Recharge to the shallow ground-water system is inferred to occur principally by infiltration of snowmelt through till, colluvium, and fractured bedrock during the period of peak snowmelt in May and June, supplemented by infiltration of summer convective precipitation to a lesser degree. The redistribution of snow by wind, discussed in section 1, is inferred to produce a correspondingly uneven distribution of recharge, with drift-accumulation areas on lee slopes contributing disproportionately to local ground-water recharge relative to wind-scoured, snow-poor windward slopes. Quantitative estimation of recharge rates was beyond the scope of the present study.

Local Water Use

Water use within the basin is presently limited to domestic supply, small-scale commercial use associated with businesses on the middle bench, and incidental stock watering at a small number of outlying properties. No large-capacity municipal or irrigation wells are known to be completed within the basin, and total ground-water withdrawal is judged to be small relative to estimated annual recharge, though no formal water budget was constructed as part of this study. Continued small-scale residential and commercial development within the basin is not expected to substantially affect the general availability of ground water, provided that new wells are sited with regard to the aquifer characteristics summarized in this section and in appendix D.

6. Engineering Geology and Geologic Hazards

Slope Stability

Slope-stability conditions within the study area are strongly dependent upon surficial-deposit type, slope gradient, and the presence or absence of shallow ground water. A three-part hazard classification, summarized in table 6 and shown schematically in figure 11, was developed to characterize relative susceptibility to shallow slope failure. Areas underlain by till or bedrock on slopes of less than about 20 degrees, comprising most of the middle bench upon which commercial development is concentrated, are classified as having generally low susceptibility to slope failure under natural conditions.

Class	Slope condition	Typical materials	Relative hazard
I	< 20°, benches and gentle till slopes	Till, weathered bedrock	Low
II	20°–30°, moderate colluvial slopes	Colluvium, till on bedrock	Moderate
III	> 30°, steep cut slopes and bench margins	Colluvium, talus, oversteepened till	High

Table 6. Slope-stability classification criteria used in this report.

Areas of moderate to high susceptibility include steep colluvial aprons below bedrock cliff bands, oversteepened cut slopes along the margins of Route 11 and Route 385, and the steep, in places nearly vertical, margins of the erosional benches themselves. Several small debris slides and slumps were observed in colluvial material along the margin of the middle bench during the course of fieldwork, generally associated with locally concentrated drainage or with prior disturbance of slope vegetation. Excavation into bench margins for building sites or road cuts should be preceded by site-specific geotechnical evaluation, particularly where cut heights exceed about 10 ft (3 m).

Flood Hazards

The main-stem channel is deeply incised and generally confined to a narrow bedrock- and coarse-alluvium corridor below the lower bench described in section 4. No extensive alluvial floodplain is present within the central basin. Because commercial and residential development is concentrated principally upon the middle bench, flood exposure of existing structures is low. Potential effects of unusually high snowmelt discharge are limited chiefly to culverts, bridge openings, short low-lying road segments, informal camping areas, and isolated channel-margin outbuildings shown schematically in figure 12.

Localized flooding and debris deposition were also noted at the mouths of several steep tributary drainages entering from the east, where alluvial-fan deposits record a history of episodic debris-flow and hyperconcentrated-flow activity, probably triggered by intense, localized summer convective precipitation. Structures sited on or immediately adjacent to these fan surfaces should be evaluated for debris-flow hazard in addition to conventional flood hazard.

Seismic Considerations

No active faults are known within the Destiny basin, and the area lies within a region of generally low historical seismicity relative to other parts of the Rocky Mountain region. Nonetheless, the northern Front Range as a whole is subject to occasional moderate earthquakes of probable intraplate origin, and standard seismic design provisions applicable to the region are considered appropriate for any structure of substantial size or occupancy. Amplification of ground motion in areas of thick, unconsolidated valley-fill deposits, though not specifically evaluated during this investigation, should be considered in the design of critical facilities.

Foundation and Excavation Conditions

Map unit	Typical bearing capacity	Excavation difficulty	Drainage / seasonal water
Till, middle bench (Qtp)	Moderate to good	Moderate (bouldery)	Locally perched, seasonal
Till, upper bench (Qtb)	Moderate	Moderate to difficult	Generally low
Colluvium (Qc)	Poor to moderate	Easy to moderate	Variable, slope-dependent
Grus / weathered bedrock	Moderate	Easy	Low
Valley fill, coarse (Qal)	Good	Easy	Shallow, seasonal high
Valley fill, organic (marsh)	Poor	Difficult (soft/saturated)	High, poorly drained

Table 5. Engineering properties of surficial map units, Destiny basin.

Engineering properties of the principal surficial map units are summarized in table 5. In general, till and colluvial deposits mantling the middle and upper benches afford moderate to good bearing capacity for light structures founded on spread footings, though local concentrations of boulders may complicate excavation and utility trenching. Valley-fill deposits along the basin axis are more variable, ranging from well-drained sandy gravel to poorly drained silt and organic-rich fine-grained sediment associated with beaver-pond and marsh deposits in the vicinity of Hidden Lake; the latter materials are of poor engineering character and are not recommended for conventional foundation support without special design consideration.

Shallow ground water, locally perched within till above less permeable material, was encountered in several test observations at depths of less than 6 ft (1.8 m) below the ground surface on the lower and middle benches, particularly during the period of peak snowmelt recharge in late spring. Basement excavation and below-grade construction in these areas should anticipate the possibility of seasonally high ground-water levels and incorporate appropriate drainage design.

Historical Hazard Events

The largest flood event of record within the basin occurred in June 1983, when unusually rapid ripening and melt of an above-average snowpack coincided with several days of warm, moist southerly airflow to produce sustained high discharge on the main stem, culminating in the peak instantaneous discharge of 340 ft3/s discussed in section 5. Local accounts and physical evidence examined during this study, including scoured vegetation lines and deposited debris above the ordinary high-water mark, indicate that flow remained largely within the established channel. Localized overtopping occurred at several constricted crossings and along short low-lying road segments, but did not extend onto the principal developed surfaces. No damage to structures on the middle bench was reported, consistent with the elevation and substantial channel separation of that surface.

A localized debris-flow event, smaller in scale but of engineering significance, was reported by area residents to have occurred during an intense, short-duration convective storm in late July 1985, originating on the steep alluvial-fan-forming tributary east of the townsite below Bald Mountain. This event deposited a lobe of poorly sorted debris across an unpaved access road at the fan apex, temporarily blocking access, but did not reach any permanent structure. Fresh, unvegetated debris-flow deposits attributable to this event were still identifiable at the time of fieldwork for this report and are reflected in the mapping of unit Qaf on plate 2.

Erosion and Sediment Control

Disturbance of vegetative cover on till- and colluvium-mantled slopes, whether by construction activity, road building, or wildfire, substantially increases susceptibility to surface erosion and, on steeper slopes, to shallow slope failure. Several instances of accelerated gully erosion were observed during fieldwork along informally graded access tracks on the upper bench, where concentration of surface runoff in unlined ditches has locally incised channels more than 2 ft (0.6 m) deep in a few years. Standard erosion-control measures, including maintenance of vegetative cover, avoidance of concentrated flow across erodible till and colluvium, and appropriately sized cross-drainage structures on access roads, are recommended wherever practicable.

Radon Potential

No radon measurements were made during this investigation. However, on the basis of the crystalline, locally pegmatitic character of bedrock within the basin, and by broad analogy with radon-potential assessments completed elsewhere in similar Front Range crystalline terrane, an above-average potential for elevated indoor radon concentrations should be anticipated, particularly in structures with basement or below-grade living space founded directly on bedrock or thin till. Site-specific radon testing is recommended for new construction, consistent with general practice throughout crystalline-terrane portions of the Front Range.

Cut-Slope and Road-Design Considerations

Road cuts observed along Route 11 and Route 385 within the mapped area are generally stable at slope angles of about 1:1 (horizontal to vertical) or flatter in till and colluvium, and somewhat steeper in unweathered bedrock; several short reaches of oversteepened cut slope in weathered bedrock or thick colluvium, however, showed evidence of minor raveling and small rockfall accumulations at the toe of the cut. Design of new road cuts or driveway access within colluvial or till materials should incorporate slope angles flatter than approximately 1.5:1 unless supported by site-specific geotechnical analysis, and should provide for adequate surface- and subsurface-drainage control to reduce the likelihood of saturation-induced instability of the type discussed above.

7. Economic Geology and Mineral Resources

A supplemental reconnaissance geochemical sampling program was conducted within the Destiny basin during 1987–88 to evaluate the mineral-resource potential of the study area, in view of scattered quartz veining noted during geologic mapping (section 2) and of the basin’s structural and lithologic similarity to mineralized terrane exposed in the historic mining districts of Jamestown, Gold Hill, and Sunshine to the south. Stream-sediment, soil, and rock-chip samples were collected at 46 localities distributed throughout the basin and analyzed for gold, silver, molybdenum, and selected rare earth elements (REE). Results, summarized below and in table 7, indicate that the basin hosts several geochemically anomalous zones of reconnaissance-level interest, though no economically proven reserve has been established by the present investigation.

Gold and Silver

Anomalous concentrations of gold and silver are associated with quartz veins and adjacent altered wallrock within and immediately flanking the northeast-trending shear zones described in section 2. Vein material is typically milky white to smoky quartz, locally accompanied by minor pyrite, galena, and sphalerite, in veins ranging from a few inches to locally more than 3 ft (0.9 m) in width. The most strongly anomalous samples, collected from float and outcrop along a shear-zone-hosted vein system exposed intermittently for approximately 2,200 ft (670 m) along the eastern wall of the basin below Bald Mountain, returned gold values as high as 0.31 oz/ton (10.6 g/t) and silver values as high as 4.8 oz/ton (165 g/t) in select grab samples. Sampling density was insufficient to establish continuity of grade along strike or to depth, and the reported values should be regarded as indicative of a mineralized system of exploration interest rather than as representative of any defined tonnage.

A second, less well exposed zone of quartz veining, associated with a subordinate shear structure crossing the basin near the head of the main stem, returned more modest but still anomalous gold values, generally in the range of 0.02 to 0.08 oz/ton (0.7 to 2.7 g/t), accompanied by weakly anomalous silver. This zone is less well characterized than the Bald Mountain-area occurrence and would benefit from additional sampling and, if warranted, trenching to evaluate its lateral extent.

Molybdenum

A subtle but persistent soil-geochemical anomaly in molybdenum, defined by values generally in the range of 20 to 85 ppm Mo against a basin-wide background of less than 5 ppm, was outlined over an area of approximately 0.4 mi2 (1.0 km2) centered on the upper basin near the headwaters of the main stem, upslope from the Pinedale-correlative terminal moraine described in section 3. Molybdenite (MoS2) was identified in trace amounts as disseminated grains and thin fracture coatings in float samples of altered, quartz-veinlet-stockwork-bearing granodiorite collected within this anomalous area, suggesting the possible presence of a buried porphyry-style molybdenum system broadly analogous to, though of unknown size relative to, other molybdenite-bearing porphyry systems recognized elsewhere in the Colorado Mineral Belt. No drilling has been conducted within the anomalous area, and the depth, size, and grade of any concealed mineralized body remain entirely speculative on the basis of surface data alone.

Rare Earth Elements

Pegmatite dikes of unit Yp, described in section 2, locally contain accessory monazite, xenotime, and allanite, identified in heavy-mineral concentrates prepared from panned stream-sediment samples collected downslope from several of the larger pegmatite bodies mapped near the western basin divide. Bulk-rock geochemical analyses of pegmatite samples returned total rare-earth-element (REE) concentrations, expressed as the sum of cerium, lanthanum, neodymium, and yttrium, as high as 1,850 ppm in a single sample of coarse, monazite-bearing pegmatite, compared with values generally less than 150 ppm in surrounding gneiss and granodiorite. These occurrences are typical of accessory-mineral REE enrichment common in Front Range pegmatites and are not, on the basis of present data, indicative of a resource of a scale that would be considered economically significant by current industry standards; they are noted here for completeness and as a guide to any future, more detailed exploration program.

Sample locality	Au (oz/ton)	Ag (oz/ton)	Mo (ppm)	REE, total (ppm)
Bald Mountain vein, grab sample	0.31	4.8	<5	110
Bald Mountain vein, chip composite	0.09	1.6	<5	95
Headwater vein zone, grab sample	0.08	0.9	8	70
Upper basin soil, Mo anomaly (avg. of 12)	<0.01	<0.1	54	60
Pegmatite, western divide (monazite-bearing)	<0.01	<0.1	<5	1,850
Basin-wide background (median of 46 samples)	<0.005	<0.1	4	85

Table 7. Summary of selected geochemical sample results, Destiny basin reconnaissance mineral-resource survey, 1987–88.

Resource Significance and Limitations

The occurrences described above establish that the Destiny basin hosts geochemically anomalous concentrations of gold, silver, molybdenum, and rare earth elements at several localities, and that at least two of these occurrences—the Bald Mountain-area vein system and the upper-basin molybdenum soil anomaly—warrant consideration for more detailed follow-up exploration, including systematic soil sampling on a regular grid, trenching of vein exposures, and, in the case of the molybdenum anomaly, geophysical survey and eventually drilling to test for a concealed mineralized body. It is emphasized, consistent with standard practice in the reporting of reconnaissance-level geochemical data, that anomalous sample results of the type presented in table 7 do not by themselves establish the presence of an economically minable resource; grade continuity, tonnage, metallurgical characteristics, and economic factors are all essential considerations not addressed by the present reconnaissance-level study. No mining claims are known to have been located within the study area as of the date of this report, and any future exploration or development activity would be subject to applicable Federal, State, and county regulation, including the geologic-hazard and land-use considerations discussed elsewhere in this report.

8. Land Use and Development Considerations

Existing development within the Destiny basin is concentrated almost entirely upon the middle erosional bench described in section 4, reflecting the combined advantages of relatively gentle slope, favorable foundation conditions, reduced flood exposure, and convenient access afforded by Route 11 and Route 385. Commercial development is concentrated upon the middle erosional bench in the vicinity of the confluence of the main stem and its principal western tributary, with outlying residential and small-acreage development extending along the bench to the north and south.

Limited additional development is present on the lower bench, principally in the form of outbuildings, storage structures, and seasonal-use facilities that are more directly exposed to channel-margin erosion and seasonal high water as discussed in section 6. Development on the upper bench remains sparse, reflecting steeper access grades, more limited availability of shallow ground water, and, in places, more difficult foundation conditions associated with deeply weathered bedrock.

Scattered rural residential development is also present east of the main basin, in the vicinity of Bark Ranch, situated upon a broad, gently sloping upland underlain by deeply weathered granodiorite grus; this area was not mapped in the same detail as the main Destiny basin but is briefly characterized in appendix E for purposes of regional comparison.

Future development within the basin, particularly any proposed expansion onto the upper bench, onto steep bench margins, or onto valley-fill deposits along the basin axis, should be preceded by site-specific geologic and geotechnical evaluation with reference to the hazard classifications and engineering properties summarized in section 6 and table 5 of this report.

Utility Corridors

Water, sewer, and electrical service within the Destiny townsite is generally confined to the middle bench, following the alignment of Route 11 and connecting side streets. Utility trenching in till on the middle bench has generally encountered favorable, if locally bouldery, excavation conditions; trenching along the margin of the lower bench, in contrast, has in places encountered shallow ground water and soft, organic-rich valley-fill material requiring special bedding or dewatering measures. Extension of utility service onto the upper bench or into outlying areas near Bark Ranch would require crossing of steep bench-margin slopes identified as areas of moderate slope-stability concern in section 6, and should be planned in consultation with a qualified engineering geologist.

Access Road Considerations

The two principal access routes serving the basin, Route 11 from the north and Route 385 from the west, both cross terrain mapped as having moderate to high susceptibility to slope failure at several localities, including oversteepened cut slopes and colluvial aprons discussed in section 6. Maintenance of adequate roadside drainage and periodic monitoring of cut-slope condition along these routes is recommended, particularly following years of above-average snowpack or unusually intense summer precipitation. Any substantial widening or realignment of either route should be preceded by geotechnical evaluation of cut and fill slopes consistent with the recommendations of section 6.

Comparison with Regional Settlement Patterns

The concentration of development within the Destiny basin upon a favorable topographic bench finds broad analogy elsewhere in the mining-era settlements of the Front Range foothills and montane zone, including Jamestown, Gold Hill, and Sunshine, each of which likewise occupies a locally favorable bench, terrace, or gently sloping valley-floor site rather than the steeper, less stable terrain immediately surrounding it. Unlike these historic mining settlements, however, the development of the Destiny townsite does not appear to be directly related to any mineral discovery, and the settlement is better interpreted, on the basis of its site characteristics, as having developed primarily in response to the same favorable combination of slope, drainage, and access conditions discussed throughout this report, rather than to proximity to a specific mineral resource.

9. Summary and Conclusions

Geologic, geomorphic, and hydrologic investigations conducted in the Destiny basin during 1986–88 indicate that the present distribution of land use within the basin is fundamentally controlled by a flight of erosional benches produced by repeated alpine glaciation and subsequent differential incision of Precambrian crystalline bedrock and associated till. The middle bench, affording the most favorable combination of gentle slope, foundation conditions, and flood-hazard exposure, supports the great majority of existing commercial and residential development, including the Destiny townsite.

Surface-water and ground-water resources within the basin are adequate for existing domestic and small-scale commercial use, though ground-water yields are locally variable and dependent upon proximity to fracture zones or valley-fill deposits of adequate thickness and permeability. Water quality is generally favorable, with the principal constituents of local concern being dissolved iron and manganese in certain valley-fill ground water.

Geologic hazards within the basin, while generally limited in scope, include shallow slope instability on oversteepened bench margins and colluvial slopes, periodic flooding and debris-flow activity along the main stem and tributary alluvial fans, and locally shallow ground water that may affect below-grade construction. None of these hazards is judged to preclude continued development within the basin, provided that site-specific evaluation is undertaken in areas of identified concern, as outlined in section 6 of this report.

This report is intended to provide a general geologic and hydrologic framework for land-use planning within the Destiny basin. It is not a substitute for site-specific geotechnical investigation, which is recommended for all significant construction projects, particularly those situated on or adjacent to bench margins, alluvial-fan surfaces, or valley-fill deposits identified in this report.

10. Recommendations for Further Study

Several subjects touched upon in this report would benefit from more detailed investigation than was possible within the scope of the present study. Direct radiometric age control on Precambrian units within the Destiny basin, and on till deposits of both recognized glaciations, would substantially strengthen the regional correlations presented in sections 2 and 3, which at present rely upon extrapolation from dated units elsewhere in the Front Range.

A more detailed, quantitative study of bench correlation among the Destiny basin and adjacent tributary drainages of the Middle St. Vrain, briefly discussed in section 4, would help clarify whether bench formation reflects a basin-wide or more localized response to postglacial base-level change. Similarly, quantitative estimation of ground-water recharge rates and of the storage characteristics of valley-fill and till aquifers, only qualitatively addressed in section 5, would improve the basis for long-term water-resource planning within the basin.

Finally, a more detailed slope-stability investigation, incorporating subsurface exploration and laboratory testing of colluvial and till materials at specific sites of proposed development, is recommended in advance of any substantial expansion of development onto the upper bench or onto steep bench-margin slopes identified in this report as areas of moderate to high hazard.

Acknowledgments

The authors thank landowners throughout the Destiny basin for permitting access to their property during the course of this investigation. Well-completion data were generously furnished by the Colorado Division of Water Resources. Aerial photography used in preparation of the accompanying plates was flown for the U.S. Geological Survey in September 1987 and August 1988.

References Cited

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Madole, R.F., and Shroba, R.R., 1979, Till sequence and soil development in North Boulder Creek drainage basin, east slope, Front Range, Colorado, in Ethridge, F.G., ed., Field guide, Front Range and northwest Denver basin, Colorado: Fort Collins, Colorado State University, p. 123–178.

Osgood, M.R., 1987, Reconnaissance geologic map of the Bark Ranch upland, Destiny County, Colorado: Colorado Geological Survey Open-File Report 87–7, scale 1:24,000.

Shroba, R.R., and Birkeland, P.W., 1983, Trends in late Quaternary soil development in the Rocky Mountains and Sierra Nevada of the western United States, in Porter, S.C., ed., Late Quaternary environments of the United States, v. 1, The Late Pleistocene: Minneapolis, University of Minnesota Press, p. 145–156.

Yancy, D.L., and Enloe, P.K., 1988, Selected well records and water-quality data, Destiny basin, Destiny County, Colorado: Colorado Division of Water Resources Basic Data Release 88–2, 61 p.

Appendix A. Measured Stratigraphic Sections

Two representative stratigraphic sections were measured to characterize the surficial deposits mantling the middle and upper benches described in section 4. Sections were measured with hand level and tape and described in the field; unit thicknesses are approximate.

Section A–1. Middle bench, east side of main stem, near river mile 2.1

0–1.2 ft: Sod and organic-rich topsoil, dark grayish brown, abundant roots.

1.2–6.5 ft: Till, unstratified, subangular boulders and cobbles of gneiss and granodiorite in a sandy silt matrix; weak oxidation, no carbonate.

6.5–11.0 ft: Weathered bedrock (grus), disaggregated Boulder Creek Granodiorite, sandy texture, retains relict foliation.

11.0+ ft: Unweathered gneiss and granodiorite bedrock (not fully penetrated).

Section A–2. Upper bench, headwater tributary, near river mile 4.6

0–0.8 ft: Sod and organic litter.

0.8–4.0 ft: Colluvium, poorly sorted angular gneiss fragments in a silty sand matrix; local frost-heave structures.

4.0–9.5 ft: Older till (Bull Lake correlative), deeply weathered, boulders exhibit grussy rinds up to 2 in. thick; strong oxidation throughout.

9.5+ ft: Weathered gneiss bedrock, highly fractured near contact with overlying till.

Section A–3. Lower bench, west side of main stem, near river mile 0.9

0–0.5 ft: Sod and thin organic horizon.

0.5–3.2 ft: Sandy loam, weakly stratified, probable reworked till or proximal outwash; scattered subrounded pebbles.

3.2–8.0 ft: Till (Pinedale correlative), fresh, unweathered, subangular boulders and cobbles in a sandy matrix; no oxidation.

8.0+ ft: Coarse sand and gravel, crudely stratified, interpreted as ice-marginal outwash; water encountered at approximately 7.5 ft during late-May observation.

Section A–4. Valley-fill terrace, basin axis near Hidden Lake

0–1.0 ft: Organic-rich silty topsoil, dark brown, saturated at time of description.

1.0–5.5 ft: Silt and clayey silt, dark gray, laminated, with abundant fine organic matter; interpreted as marsh or pond-margin deposit associated with beaver activity.

5.5–10.0 ft: Sand and gravel, moderately well sorted, probable stream-channel deposit underlying marsh sediment.

10.0+ ft: Till (Pinedale correlative), not fully penetrated in hand-auger hole.

Section A–5. Bark Ranch upland, road-cut exposure

0–1.5 ft: Sod and thin eolian silt cap, pale brown, weakly cohesive.

1.5–7.0 ft: Grus, coarse, sandy, derived from Boulder Creek Granodiorite; relict foliation visible throughout; friable, easily excavated by hand.

7.0–12.0 ft: Grus, coarser and less weathered, grading downward into fractured, partially weathered granodiorite bedrock.

12.0+ ft: Unweathered granodiorite bedrock, moderately fractured.

Section A–6. Terminal moraine, headwater reach near basin divide

0–2.0 ft: Sod, alpine turf, and thin organic horizon.

2.0–14.0 ft: Till (Pinedale correlative), fresh, boulder-rich, matrix-poor, boulders up to 6 ft in maximum dimension; hummocky surface expression, kettle depressions nearby.

14.0+ ft: Not penetrated; inferred to consist of additional till or bedrock on the basis of adjacent natural exposures.

Appendix B. Soil Descriptions

Soils within the study area were examined at a reconnaissance level in support of the engineering and land-use evaluations presented in sections 6 and 7. Soils formed on till and colluvium of the middle and upper benches are generally well-drained, coarse-textured, and of moderate to shallow depth to weathered bedrock or unweathered till. Soils formed on valley-fill deposits along the basin axis are more variable, ranging from well-drained sandy loam to poorly drained, organic-rich material in low-lying marsh and beaver-pond settings, notably in the vicinity of Hidden Lake.

Map symbol	Landform / parent material	Drainage class	Depth to bedrock or till
Db	Middle bench till	Well drained	> 40 in
Dc	Colluvial apron	Well to moderately well drained	20–40 in
Dg	Weathered bedrock (grus)	Well drained	< 20 in
Dv	Valley-fill, coarse	Well drained	> 60 in
Dm	Valley-fill, organic (marsh)	Poorly drained	Variable
Du	Upper bench, older till	Moderately well drained	24–40 in
Dl	Lower bench, reworked till/outwash	Well drained	> 48 in
Dt	Talus and colluvium, steep slopes	Excessively drained	< 12 in
Dr	Alluvial fan deposits	Well to somewhat excessively drained	> 36 in
Do	Eolian-mantled upland (Bark Ranch)	Well drained	20–36 in

Table B–1. Generalized soil map units, Destiny basin.

Soils mapped as unit Db, underlying most of the commercial core of the Destiny townsite, are typically sandy loam to loam in texture, moderately deep to underlying unweathered till, and afford generally favorable conditions for both foundation support and on-site sewage disposal where lot sizes are adequate. Soils of unit Dm, confined to marsh and pond-margin settings near Hidden Lake, are poorly suited to conventional foundation support or to on-site sewage disposal because of high organic content, poor drainage, and seasonally high water table, and development on these soils is not recommended without special engineering design.

Soils of unit Dt, mapped on steep talus and colluvial slopes below bedrock cliff bands, are thin, excessively drained, and highly susceptible to disturbance; removal of vegetative cover on these soils substantially increases susceptibility to surface erosion and shallow raveling failures of the type discussed in section 6.

Appendix C. Streamflow and Water-Quality Data

Selected streamflow and water-quality data collected during 1987–88 at the partial-record gaging station near the basin mouth (station 06724500) and at miscellaneous sampling sites are presented below. These data supplement the summary statistics presented in table 3 and the water-quality discussion in section 5.

Date	Discharge (ft3/s)	Specific conductance (µS/cm)	pH
05-28-87	142	58	7.1
07-14-87	26	84	7.4
09-02-87	9.8	97	7.6
11-15-87	4.1	104	7.5
01-19-88	2.3	112	7.5
03-30-88	3.0	108	7.4
06-03-88	168	52	7.0
06-25-88	97	61	7.1
08-10-88	14	91	7.6
10-05-88	6.2	99	7.5

Table C–1. Miscellaneous streamflow and field water-quality measurements, station 06724500.

Selected laboratory water-quality analyses, from samples collected at wells and springs throughout the basin during 1987–88, are summarized in table C–2. Concentrations are given in milligrams per liter (mg/L) except as noted.

Site	Calcium	Magnesium	Sodium	Iron	Manganese	Dissolved solids
Spring, middle bench	12	3.1	2.4	0.02	<0.01	68
Well D–1	18	4.6	3.8	0.11	0.03	94
Well D–3 (bedrock)	9	2.2	2.0	0.01	<0.01	58
Well D–5 (valley fill)	22	5.9	4.1	0.62	0.18	121
Surface water, station 06724500	8	1.9	1.6	0.03	<0.01	52

Table C–2. Selected laboratory water-quality analyses, Destiny basin, 1987–88.

Appendix D. Selected Well Records

Well no.	Bench / setting	Depth (ft)	Yield (gal/min)
D–1	Middle bench (till)	62	6
D–2	Middle bench (till)	48	4
D–3	Fracture zone, bedrock	210	27
D–4	Upper bench (grus/bedrock)	155	2
D–5	Valley fill, basin axis	35	11
D–6	Middle bench (till)	71	5
D–7	Lower bench (outwash)	44	14
D–8	Fracture zone, bedrock	188	19
D–9	Upper bench (bedrock)	162	1.5
D–10	Bark Ranch upland (grus)	98	3
D–11	Middle bench (till)	55	7
D–12	Valley fill near Hidden Lake	28	9

Table D–1. Selected well records, Destiny basin. Data furnished by Colorado Division of Water Resources.

Static water levels reported at time of well completion ranged from land surface (flowing or near-flowing conditions, well D–12) to as much as 90 ft (27 m) below land surface at well D–9, on the upper bench. Wells completed in valley-fill deposits along the basin axis generally exhibited the shallowest static water levels, typically less than 15 ft (4.6 m), consistent with the near-surface, unconfined character of the valley-fill aquifer discussed in section 5.

Specific-capacity data, calculated from driller-reported yield and drawdown at the time of well completion, indicate substantially higher values for wells completed in or near fracture zones (wells D–3 and D–8, table D–1) than for wells completed in unfractured till or bedrock, consistent with the fracture-density relations discussed in section 2. Specific capacity for well D–3, the highest-yielding well inventoried during this study, is estimated at approximately 0.9 gal/min per foot of drawdown, compared with values generally less than 0.15 gal/min per foot of drawdown for wells completed in unfractured till.

Well construction throughout the basin is predominantly by rotary or cable-tool methods, with steel or, in more recent completions, PVC casing; most wells are completed with an open borehole or a simple slotted-casing interval in the producing zone, without gravel packing. No wells inventoried during this study were reported to have required hydrofracturing or other well-stimulation treatment to achieve adequate domestic yield, though several well owners reported a decline in yield during the driest part of the summer in years of below-average snowpack.

Appendix E. Description of Map Units

The following brief unit descriptions supplement the geologic map units summarized in table 1 and the surficial units discussed in section 3, and are provided for reference in areas, such as the Bark Ranch upland east of the main basin, that were examined only at reconnaissance level.

Xbg — Biotite gneiss, undivided. Banded gray to dark-gray biotite gneiss and migmatite; locally garnetiferous.

Ybc — Boulder Creek Granodiorite. Medium-grained, weakly foliated, light-gray granodiorite; forms resistant ridges and cliff bands.

Qtb — Till, Bull Lake correlative. Deeply weathered, oxidized, boulder-rich till of older glaciation; upper bench and basin-mouth deposits.

Qtp — Till, Pinedale correlative. Fresh, hummocky, boulder-rich till of younger glaciation; lower and middle bench deposits.

Qc — Colluvium, undivided. Poorly sorted, angular rock fragments derived from local bedrock; mantles steep slopes and bench margins.

Qaf — Alluvial fan deposits. Poorly sorted sediment at mouths of steep tributary drainages; subject to debris-flow and hyperconcentrated-flow deposition.

Qal — Alluvium, undivided. Sand, gravel, and minor silt of the active floodplain and lowest terraces.

Unit Xbg is the most areally extensive bedrock unit in the study area, underlying the greater part of both the upper bench and the higher ridges and summit areas bounding the basin, including the slopes below Meadow Mountain, St. Vrain Mountain, and the unnamed divide toward Taylor Mountain. Where deeply weathered, this unit grades into a saprolitic mantle similar in engineering character to, though generally finer-grained than, weathered granodiorite (grus) derived from unit Ybc.

Unit Ybc underlies several elongate ridges within the basin and forms the dominant bedrock unit exposed in road cuts along the upper reaches of Route 11. Because of its tendency to weather to grus, this unit commonly presents excavation conditions intermediate between soil and rock, requiring care in the specification of excavation and slope-design parameters for construction projects.

Units Qtb and Qtp together constitute the till sheet that mantles most of the middle and lower benches described in section 4, and are by far the most important surficial units with respect to existing development within the basin. Their engineering properties are summarized in table 5 and discussed further in section 6.

Unit Qaf, mapped at the mouths of several steep, unnamed tributary drainages entering the main stem from the east below Bald Mountain, records a history of episodic debris-flow and hyperconcentrated-flow deposition and is treated as a zone of elevated hazard in section 6.

Appendix F. Glossary of Terms

Bull Lake glaciation — An episode of alpine glaciation recognized throughout the Rocky Mountain region, generally correlated with an early-to-middle Wisconsinan or older age and characterized by deeply weathered, subdued morainal deposits.

colluvium — Unconsolidated material transported chiefly by gravity-driven processes such as creep and slope wash, typically mantling hillslopes below bedrock outcrops.

grus — Coarse, sandy to gravelly material produced by in-place disaggregation (weathering) of granitic or granodioritic bedrock.

moraine — A mound, ridge, or other distinct accumulation of unsorted, unstratified glacial drift, predominantly till.

Pinedale glaciation — The most recent major episode of alpine glaciation in the Rocky Mountain region, generally correlated with a late Wisconsinan age and characterized by fresh, well-preserved morainal topography.

till — Unsorted, unstratified sediment deposited directly by glacial ice, without significant transport or reworking by meltwater.

valley fill — Unconsolidated sediment, typically alluvium and reworked glacial drift, occupying the floor of a valley.

equilibrium-line altitude — The altitude on a glacier, averaged over a period of years, at which annual accumulation of snow and ice is balanced by annual ablation (melting).

erosional bench — A step-like remnant of a former valley floor or trough shoulder, preserved as a topographic bench along a valley wall as a result of subsequent incision of the main channel.

foliation — A planar fabric in metamorphic rock produced by the parallel alignment of platy or elongate minerals, most commonly mica.

hyperconcentrated flow — A sediment-water flow intermediate in character between normal streamflow and a debris flow, transporting a very high concentration of suspended and bed sediment.

knickpoint — A point of abrupt change in the gradient of a stream channel, commonly associated with a resistant rock unit or with a wave of incision propagating upstream from a base-level change.

mylonite — A fine-grained, foliated rock produced by ductile deformation and grain-size reduction along a shear zone.

periglacial — Pertaining to processes, conditions, and landforms associated with cold, non-glacial environments, typically involving frost action.

perched ground water — Ground water occurring above a normal water table, supported by a localized zone of low permeability.

saprolite — Weathered rock that retains the original texture and structure of the parent rock, though softened and, in places, disaggregated.

shear zone — A tabular zone of concentrated ductile or brittle deformation within a rock mass, typically narrower than its length and marked by intense fracturing, foliation development, or mylonitization.

terrace — A relatively flat, elongate surface, commonly underlain by alluvium, that flanks a stream and represents a former level of the valley floor or floodplain.

water-table aquifer — An aquifer that is not confined by an overlying unit of low permeability, in which the upper surface of the saturated zone (the water table) is free to rise and fall.

porphyry — An igneous rock containing conspicuous, relatively large crystals (phenocrysts) in a finer-grained groundmass; many molybdenum and copper deposits are associated with porphyritic intrusive stocks.

stockwork — A three-dimensional network of closely spaced, interconnected veinlets, commonly the setting for disseminated low-grade metallic mineralization such as molybdenite.

pegmatite — A very coarse-grained igneous rock, typically granitic in composition, commonly hosting rare and accessory minerals such as monazite and xenotime.

REE (rare earth elements) — The lanthanide series elements plus yttrium and scandium, commonly hosted in accessory minerals such as monazite, xenotime, and allanite.

assay — A quantitative chemical analysis performed to determine the concentration of one or more elements, typically metals, in a rock, soil, or sediment sample.

Appendix G. Selected Climate Data

Climate data specific to the Destiny basin are not available; the estimates presented in section 1 and summarized below were derived by orographic and altitudinal adjustment of records from regional climate stations at Ward, Allenspark, and Brainard Lake, following standard regional lapse-rate and precipitation-adjustment procedures. These estimates should be regarded as approximate and are provided for general planning purposes only.

Month	Mean temp. (°F)	Mean precip. (in)	Percent as snow
January	18	1.8	95
February	20	1.9	93
March	25	2.6	85
April	32	2.9	70
May	41	3.1	40
June	50	2.2	10
July	57	2.4	0
August	55	2.5	0
September	48	2.0	15
October	38	1.9	45
November	27	1.9	80
December	19	1.8	92

Table G–1. Estimated monthly climate summary, Destiny townsite altitude (approx. 8,600 ft), derived by adjustment of regional station records.

Appendix H. Index to Aerial Photography

Aerial photography used in the preparation of the accompanying plates and in general support of geologic mapping throughout the study area is indexed below. All photography is black-and-white, panchromatic, and was flown under contract to the U.S. Geological Survey.

Flight	Date	Approx. scale	Frames covering study area
DB–87–1	09-14-1987	1:24,000	112–128
DB–87–2	09-14-1987	1:24,000	201–216
DB–88–1	08-22-1988	1:12,000	44–61
DB–88–2	08-23-1988	1:12,000	62–79

Table H–1. Index to aerial photography, Destiny basin study area.

Appendix I. Selected Field Photograph Log

Photographs referenced in the text and figures of this report, and additional representative photographs not separately reproduced, are logged below by roll and frame number. Original photographs and negatives are on file with the Colorado Geological Survey, Denver, Colorado.

Roll–frame	Subject	General location
88–1, 14	Lateral moraine crest	West basin margin, near Brainard Lake divide
88–1, 22	Middle bench, townsite view	Destiny townsite, looking north
88–2, 03	Shear zone exposure	Road cut, Route 11
88–2, 19	Debris slide, colluvial slope	Middle bench margin, east side
87–1, 07	Alluvial fan apex	Tributary below Bald Mountain
87–1, 31	Grus exposure	Bark Ranch upland road cut
87–2, 11	Kettled moraine surface	Headwater reach, near basin divide
87–2, 26	Marsh deposit, beaver pond	Basin axis near Hidden Lake

Table I–1. Selected field photograph log, Destiny basin investigation.

Appendix J. Agencies and Offices Consulted

The following agencies and offices provided data, records, or logistical assistance during the course of this investigation. Individual well owners and landowners who provided access and well-completion information are not listed individually but are thanked collectively in the Acknowledgments section of this report.

Colorado Division of Water Resources, Denver, Colorado — well-completion and permit records.

Colorado Geological Survey, Denver, Colorado — cooperative funding, review, and regional geologic data.

Destiny County Land Use Department, Destiny, Colorado — cooperative funding and land-use planning context.

U.S. Forest Service, Destiny Ranger District — access information and records for National Forest lands adjacent to the study area.

Local water conservancy district office, Allenspark, Colorado — streamflow records and gaging-station access.