Supplemental Historical Background for Lake Sangraco and the Kershaw Ditch, Prepared for: Regional Transportation District 1560 Broadway, Suite 700 Denver, Colorado 80202 303-299-2426 Prepared by: Thomas Witt SWCA Environmental Consultants 295 Interlocken Blvd., Suite 300 Broomfield, Colorado 80021 Phone: 303-487-1183 or Fax: 303-487-1245 www.swca.com SWCA Project No. 26452.05 October 1, 2013
TABLE OF CONTENTS Page INTRODUCTION... 1 LAKE SANGRACO (5AM2785)... 1 KERSHAW DITCH (5AM2089)... 6 REFERENCES... 10 LIST OF FIGURES Figure Page 1 1937 aerial photograph showing the Brannan Sand and Gravel Company property. Red line added to show the modern location of Lake Sangraco.... 2 2 1954 aerial photograph of the Brannan Sand and Gravel Company operation showing significant flooding of the quarry site.... 3 3 1955 aerial photograph of Lake Sangraco, showing tree-lined road on the south end of the property.... 4 4 1965 aerial photograph of Lake Sangraco.... 5 5 1972 aerial photograph of Lake Sangraco.... 6 6 1957 USGS quadrangle map showing Lake Sangraco, the access road to the south side of the lake, and the original alignment of the Kershaw Ditch, west of Lowell Boulevard. Red dashed line added to show current alignment of Kershaw Ditch (5AM2089.1).... 7 7 1965 aerial photograph of Lake Sangraco. Red arrows added to show location of Kershaw Ditch west of the property... 8 8 1972 aerial image of Lake Sangraco and the Kershaw Ditch from Google Earth. Blue arrows indicate the alignment of the Kershaw Ditch west of Lake Sangraco and the red arrows show location of trees along the Kershaw Ditch/overflow ditch south of Lake Sangraco.... 9 9 1993 aerial image of Lake Sangraco and the realigned Kershaw Ditch from Google Earth. Arrows added to show location of trees along the Kershaw Ditch.... 10 ii
INTRODUCTION At the request of the Regional Transportation District (RTD), SWCA Environmental Consultants (SWCA) conducted historical research on two previously recorded historic resources, Lake Sangraco (5AM2785) and a segment of the Kershaw Ditch (5AM2089.1), located east of Lowell Boulevard, north of the Union Pacific right-of-way, in the west half of Section 8, Township 3 South, Range 68 West. Of specific interest in this research is the origin of the trees lining both the road leading to the Lake Sangraco facilities from Lowell Boulevard and along the banks of the ditch. SWCA s research focused on aerial photographs of the Denver area from as early as 1937 through the present, historical U.S. Geological Survey (USGS) topographic quadrangles, and existing historical documentation for the two resources. Detailed histories of the Sangraco property and the Kershaw Ditch can be found with the associated site records. The following document provides a brief narrative timeline of the development of the lake and the ditch, and summarizes the overall findings of the research. LAKE SANGRACO (5AM2785) Lake Sangraco was established as a recreational area in 1955, but prior to that date it was part of a gravel operation owned by John W. Brannan, under the name J.W. Brannan Sand and Gravel Company (the Gravel Company). Brannan began his gravel operations in Denver in 1906, but did not acquire the property north of the railroad and east of Lowell Boulevard until the 1920s (known as Pit #8) (Gillan 2011). According to the National Register of Historic Places (NRHP) nomination for 5AM2785, the Gravel Company began mining Pit #8 sometime prior to Brannan s death in 1930 (Gillan 2011). The aerial images from 1937 show minimal development of Pit #8, but there are excavations visible on the property (Figure 1). The road currently on the south side of Lake Sangraco was not yet developed by 1937. Several trees are visible on the south end of the property in the general vicinity of the modern road, but are not related to the trees currently lining the road, as they disappear once the gravel operations begin in the 1940s. 1
Figure 1. 1937 aerial photograph showing the Brannan Sand and Gravel Company property. Red line added to show the modern location of Lake Sangraco. By 1953, the gravel company had excavated a large portion of what would become Lake Sangraco. Access to the property in 1953 appears to be from the east end of the parcel, and the road accessing the property from Lowell Boulevard is not yet present. The trees visible in 1937 on the south end of the property are no longer visible, likely having been removed during the mining operations. In 1954, the quarry appears to flood (Figure 2). The NRHP nomination for Lake Sangraco indicates that the gravel company struck groundwater during the gravel operation, flooding the quarry (Gillan 2011). Aerial imagery from 1954 shows the quarry area partially flooded. This event appears to have ended the quarrying activities on the property. 2
Figure 2. 1954 aerial photograph of the Brannan Sand and Gravel Company operation showing significant flooding of the quarry site. By May 1955 the quarry area was completely flooded and had been reclaimed by the Brannan family as Lake Sangraco (Figure 3). The lake was reshaped to its current design, and the road leading from Lowell Boulevard was built to access to the lake facilities. Although only faintly visible on the aerial photographs, trees are visible on either side of the road and along the south side of the lake. This corresponds to the information in the NRHP nomination for Lake Sangraco, which states that Brannan built the tree-lined road in 1955 (Gillan 2011). The trees on both sides of the road appear in all of the remaining aerial photographs, growing in size and number (Figures 4 and 5). Although it is difficult to clearly distinguish the trees that are located on the Brannan property from those on the Union Pacific right-of-way, it seems fairly clear that the trees began on the Brannan property along the road and spread southward onto the Union Pacific property and the current project area, supported in recent years by the water flowing through the Kershaw Ditch. 3
Figure 3. 1955 aerial photograph of Lake Sangraco, showing tree-lined road on the south end of the property. 4
Figure 4. 1965 aerial photograph of Lake Sangraco. 5
Figure 5. 1972 aerial photograph of Lake Sangraco. To summarize, the trees along the south side of the Lake Sangraco property were planted sometime between 1955 and 1956 along either side of the access road built around the same time. The trees were initially limited to the area immediately adjacent to the road, but over the years have grown and spread to the south, filling in the space between the road and the modern alignment of the Kershaw Ditch. KERSHAW DITCH (5AM2089) Although the Kershaw Ditch does not appear on USGS topographic maps until 1957 (Figure 6), its initial appropriation date of 1860 suggests that the ditch was present, just not indicated on the maps. The ditch does appear on the earliest available aerial photograph in 1937. The original alignment of the Kershaw Ditch, as indicated on the 1937 aerial photograph and the 1957 USGS map, follows north from Clear Creek along the west side of Lowell Boulevard, flowing west of the Brannan/Sangraco property, and then turning east to the north of the Brannan property and eventually terminating near Federal Boulevard. The alignment of the ditch in 1937, 1957, or 1965 (Figures 1, 6, and 7, respectively) did not follow south of the Brannan/Sangraco property along the Union Pacific right-of-way, as the current alignment of the ditch does. 6
Figure 6. 1957 USGS quadrangle map showing Lake Sangraco, the access road to the south side of the lake, and the original alignment of the Kershaw Ditch, west of Lowell Boulevard. Red dashed line added to show current alignment of Kershaw Ditch (5AM2089.1). 7
Figure 7. 1965 aerial photograph of Lake Sangraco. Red arrows added to show location of Kershaw Ditch west of the property. The ditch along the south side of the Brannan/Sangraco property, through the Union Pacific right-of-way, does not appear clearly on any aerial photographs until 1972, where it appears to be in use as an overflow or return ditch, carrying excess water from the Kershaw Ditch back into Clear Creek (Figure 8). It is around this time, with the addition of the overflow ditch, that trees begin to appear in aerial imagery on the south side of the ditch within the Union Pacific right-of-way. Initially, the vegetation growth along the overflow ditch was fairly small. The main alignment of the Kershaw Ditch continues to flow to the west of Lowell Boulevard until sometime between 1985 and 1999, when that canal way was either rerouted into the overflow ditch south of the Brannan/Sangraco property or piped underneath Lowell Boulevard. In the 1990s, the vegetation along the ditch increases dramatically along its entire length, likely due to the transition of the rerouted ditch alignment from temporary overflow use to full-time use (Figure 9). 8
Figure 8. 1972 aerial image of Lake Sangraco and the Kershaw Ditch from Google Earth. Blue arrows indicate the alignment of the Kershaw Ditch west of Lake Sangraco and the red arrows show location of trees along the Kershaw Ditch/overflow ditch south of Lake Sangraco. 9
Figure 9. 1993 aerial image of Lake Sangraco and the realigned Kershaw Ditch from Google Earth. Arrows added to show location of trees along the Kershaw Ditch. To summarize, the alignment of 5AM2089 that follows to the south of the Brannan/Sangraco property, within the Union Pacific right-of-way, is not the historic alignment of the Kershaw Ditch, but an overflow or return ditch developed in the latter half of the twentieth century. The overflow ditch alignment did not serve as a primary channel for water from the Kershaw Ditch until the late twentieth century when development along the historic Kershaw Ditch way disrupted that original alignment. The trees along the north side of the ditch appear to be volunteer trees resulting from overgrowth from the Brannan property, and trees migrating to the south side through natural vegetative growth. REFERENCES Gillan, Kimberly A. 2011 Brannan Sand and Gravel Pit #8 Sangraco Lake and Boathouse Complex. National Register of Historic Places Registration Form. On file with the United States Department of the Interior, National Park Service. 10