Palmer Lake Preliminary Restoration Study — JDS-Hydro Consultants (April 2015)

JDS-Hydro Consultants was retained by the Palmer Lake Restoration Committee — a 501(c)(3) nonprofit — to evaluate means to restore Palmer Lake. More importantly, the report was commissioned to evaluate alternatives to “hold” water in Palmer Lake while the Committee and Town investigated means to bring ancillary water to the impoundment. In order to evaluate means to hold water in the lake, JDS had to first investigate why the lake was not currently holding water and how water got there in the first place, whether by natural or artificial means.

Afterwards, JDS also had to determine whether the lake could retain water in the future and what steps might be necessary to ensure the lake could hold water going forward. This meant researching the history of the lake, reviewing local geology, reading and analyzing previous engineering and geological reports, commissioning subsurface investigations, monitoring surrounding water levels, interviewing those familiar with the lake, evaluating weather patterns, and participating in actual dredging efforts discussed in the report.

JDS acknowledges a number of peripheral efforts by local entities to help gather data — especially Jeff Hulsmann with the Palmer Lake Restoration Committee, Chris Cummins, Pat Duby, George Halley, Danielle Cummins, and the rest of the UCCS geology department, Dwire Excavating, Mike Archer, Janine Engle, and Roger Davis with the Palmer Lake Historical Society.

Early History

Palmer Lake was first documented by western historians during Colonel Henry Dodge's 1835 Expedition (also known as the 2nd Dragoon Expedition) along the Front Range between the Platte and Arkansas Rivers. In Colonel Dodge's report to the US Senate in 1836, the Expedition noted that a natural lake existed on the Palmer Divide (not so named at the time) measuring approximately one-half mile long and four to five hundred yards wide.

By 1874, an ice house was constructed on the south side of the lake. By 1882, Dr. William Finley Thompson began platting the community of Palmer Lake with substantial investments from foreign interests. Around the same time, the Denver & Rio Grande commissioned Sam Hackett to record the Hackett Ditch water right with Colorado's Clerk and Recorder under a “mechanical, irrigation, and domestic right.” The ditch was used to bring water into Palmer Lake off of North Monument Creek to supplement water for the steam engine. This discharge of water into Palmer Lake was actually a fountain that has been photographed numerous times at different points during the late 1800s into the early 1900s.

Recent History

Since the early 1900s, Palmer Lake remained an important and popular tourist attraction and important train stop / water station for the Denver & Rio Grande Western Railway (D&RGW). The area surrounding Palmer Lake was still dominated by ranches, a couple of tourist-dominated hotels, and farmland. The water stored in the lake continued to be supplemented by diversions off of Monument Creek through the fountain pipeline to support water use for the steam engines.

Two significant developments changed Palmer Lake's water needs by the 1950s:

• Establishment of the United States Air Force Academy (1954) — The construction and initiation of this institution brought large-scale urban development on both sides of the Academy grounds. Though large-scale development at Palmer Lake did not occur until the early 1990s, the presence of the Air Force Academy changed the demographics of the rural-based Palmer Lake community to more of an urban landscape.
• Retirement of D&RGW steam locomotives (mid-1950s) — With the advent of diesel locomotive engines in the 1930s, the D&RGW Rail Company retired all of its steam engines in 1956 and moved to a more powerful and efficient engine, eliminating the need for lake supplementation.

Water levels in Palmer Lake had the potential to be supplemented using the existing water line off of Monument Creek into the 1970s. In 1996, the Town's water department converted the 4” potable line supplementing Palmer Lake into a raw water line by extending the 4” line up to Monument Creek and to make diversions off of the lower reservoir. However, these fills were very small and constrained due to the capacity of the Town's surface water treatment plant and distribution system. By 2002, the Colorado Division of Water Resources determined that the Town of Palmer Lake could no longer make diversions off of Monument Creek into Palmer Lake, citing the Anchor Ditch railroad diversion rights. As of 2013, the lake had been essentially dry.

JDS reviewed and built upon a substantial body of prior work conducted by researchers and volunteers over the preceding decade:

Why It Was Full

It is abundantly clear from the study that Palmer Lake originally was a natural lake kept full via natural means prior to human development and expansion. Palmer Lake's water levels rose and fell with the amount of snowpack experienced in the area. Considering current and historical drought conditions, Palmer Lake is not naturally filled by any reliable, consistent, or developed stream reach — but predominantly by subsurface flows off of the Rampart Range. There are neither any discrete avenues of surface inflow, nor any discharge channels or creeks to either of the South Platte or Arkansas River tributaries.

Rather, subsurface flows naturally enter Palmer Lake through a series of documented springs on the west and northwest side of the lake. The springs are fed via snow melt off of the Rampart Range moving through the Sundance Mountain area through a large alluvial fan into the lake from the west. In more precipitation years, surface flows off of Sundance Mountain and the Rampart Range probably also contributed water. In many ways, natural water levels in Palmer Lake are representative of the alluvial water levels on the Palmer Divide.

Why It's Empty

The report identifies three contributing factors to the lake's persistent dryness:

• Persistent drought conditions:Given that Palmer Lake's natural water fill source is via subsurface flows from the Rampage Range, the alluvial water flows have diminished over the past 10 years. With historically declining snow levels and historical drought conditions on the Front Range over almost the past two decades, the infiltrating alluvial flows through the alluvial fan to the lake have been substantially reduced. While healthy rainfall in the summer months helps maintain alluvial water levels above ground, it does not normally help sustain alluvial water levels below ground because rainfall (especially in small amounts) tends to runoff on the surface before percolating down into the small cracks and crevices in the soils.
• Lake bed dynamics:CTL's 2005 report seemed to indicate that Palmer Lake's declining effects in the late 1990s may have contributed to the lake drying up. However, Mr. Duby's 2014 geotechnical report indicated the non-native sediment present in the lake bottom may have been acting as a “cap” over the alluvial aquifer. The lake bed subsurface is comprised of non-native sediments, organic muck, clays, and sandstones. A relatively “young” lake that had been developing additional organic growth on its surface had deposited substantial amounts of low-permeability material over time.
• Loss of supplemental water sources:Supplemental fills of the lake using Town of Palmer Lake fully consumable water sources (i.e. Denver Basin Wells or “Greater Basin” wells) occurred since 2002 through using fully consumable water supplied by the Town. However, these fills were very small and sporadic and not supported by Palmer Lake's water department due to finite sources. By 2002, all supplemental diversions from Monument Creek were discontinued by direction of the State of Colorado's Division of Water Resources.

Also noted by JDS: Palmer Lake sits on a Palmer Divide between the South Platte Basin to the north and the Arkansas River Basin to the south. All naturally filled lakes “seep” over time. Being that the railroad track corridor to the south of the lake is actually below the lake bed, natural seepage to the south through this corridor is possible. Monitoring wells T-1 and T-11 were constructed to allow observation of this phenomenon.

Additionally, the Union Pacific Railroad embankments, especially on the northwest side where culverts have been recently realigned, have created difficult water issues with the railroad. Prior to development of this railroad embankment, the rails were a lot lower and allowed surface water flows to naturally accrue to Palmer Lake from the west.

In October 2014, the Committee and Town of Palmer Lake obtained a GOCO grant to help finance surrounding park development, which included allocations for fill dirt. The Committee and Town therefore determined to utilize a small portion of the GOCO funds — along with grassroots community funding — for the non-native sediment removal as a means to re-shape the southern side of the lake into a new park area. The Committee retained the services of Dwire Excavating to complete the non-native sediment removal and re-deposit the “spoils” on the south side of the lake.

Because the lake was essentially dry as a result of the low alluvial water levels, Dwire was able to utilize its heavy equipment to access the lake bed and begin removal of the non-native sediment without the use of a dredging barge. JDS-Hydro, along with Palmer Lake Restoration Committee volunteers, served as construction oversight during the month of December. Removal efforts were conducted between December 4, 2014 to December 18, 2014.

What the Test Pits Revealed

JDS-Hydro had Dwire excavate test pits at three locations:

• North east side of the lake — near the western shore. The test pit dug near the northern shore did not manifest any water, but did reveal quite a bit of clay with very little in the way of sands and gravels.
• Near the western shore — The test pit also revealed a greenish, iron-stained dense vein of clay at around 6’, the previously referenced “clay lens.” The contractor attempted to follow this clay lens. The test pit dug near the western shore had the same soil stratifications including the clay lens, but also manifested water at approximately 6’.
• Near the center “knoll” (Test Pit #3) — The last test pit, dug near the knoll at the center of the lake, revealed quite a massive mixture of clays and sands, including an iron-stained striation of sands indicating historical water content. In addition, water filled the test pit to within 2” of the lake bed surface — the most saturated of all three locations. Water exposed in all test pits was promptly re-covered with native soils.

Source of “springs” confirmed: As indicated in Kim Makower's online post, he theorized that the source of natural groundwater infiltration into the lake was natural springs along the northwest shores. The 2014 excavation confirmed this extensively — a very extensive area of water infiltration was observed along the western shores. This was consistent with some of the surface flows coming into the lake at the northwest corner of the lake near the dock. The loose material comprising alluvium and colluvium, described by Mr. Dunn, allows these subsurface snowmelt flows to run through the alluvium and feed the springs along the northwest shore of Palmer Lake.

The resulting reduced surface area approximates the original and natural surface areas developed from the restoration excavation. It is assumed that anywhere from 25 AF to 38 AF of evaporation is possible (depending upon rainfall) assuming that the lake is full.

Railroad Culvert (UPRR)

As mentioned in Section 2.3.2, the natural surface flows coming off of the alluvial fan from Ben Lomand and Sundance Mountain to the west of the lake have probably been significantly altered by development of the Union Pacific Railroad embankments, especially on the northwest side where culverts have been recently realigned. The Town of Palmer Lake has observed sheet flows coming off of Highway 105 and west of the Town during large storm events. Over the past 20 years, the railroad tracks operated and maintained by the Denver & Rio Grande (now Union Pacific and BNSF) have changed alignments and facilitated movement of water away from Palmer Lake. A preliminary survey of the area seemed to indicate that there was sufficient grade available between the UPRR ditch and the lake to convey at least some of the water. Very preliminary construction costs are estimated at $190,000.

Design considerations include: the culvert should be constructed as far to the north as possible to intercept as many surface flows as possible; the culvert should come into the lake at or below the current southern side of the lake (above the crescent); and planning and design of the culvert will take significant interface with Union Pacific Railroad (UPRR), which may require an encased or concrete culvert. JDS notes it is unlikely Union Pacific will be satisfied with a simple RCP “tube” and may require an encased or concrete reinforced structure.

Ben Lomand Surface Flows

Though the Ben Lomand drainage basin directly to the west which historically contributed surface flows to Palmer Lake is significantly smaller than the drainage basin of Sundance Mountain and the Rampart Range, these flows may still prove significant during large runoff events. The drainage area is estimated at roughly 2 square miles (600 acres) producing an estimated 2 AF annually on average. JDS would encourage the Town of Palmer Lake and the Committee to pursue planning, evaluation, design, and surface water re-routing of Ben Lomand into Palmer Lake as a long-term project goal.

From the above developed reports, JDS can state the following opinions:

• Palmer Lake is a Natural Lake: The subsurface flows off the Rampart Range feeding the lake are natural; the lake bed itself is natural sandstone and alluvial materials; and Palmer Lake has been naturally maintained as a lake since at least the early 1800s (and likely much longer).
• Natural water levels in Palmer Lake are representative of the alluvial water levels on the Palmer Divide. If snowpack and rainfall is sufficient, the lake will naturally rise. If not, it will fall. Without any supplemental source of water, none of the proposed solutions would be a viable long-term solution — the lake would eventually dry up again during a sustained drought.
• The removal of non-native sediment in late 2014 has already begun encouraging natural lake fill. As of the field visit on March 16, 2015, the lake was taking on a substantial amount of natural water accruals from alluvial infiltration, especially from the springs located along the west side and the “crescent” in the center of the lake near the knoll. Water levels had already begun filling the bottom of the southern portion of the lake.
• Because the problem is multi-faceted, so is the solution: it is likely that the final solution to keeping Palmer Lake “full” will involve a combination of solutions — including potentially sealing the lake while attempting to maintain the natural means of filling the lake; potentially reducing the size of the lake to reduce impacts of evaporation and exfiltration while minimizing the amount of water required to fill the lake; and potentially securing an additional alternative water source to supplement volume losses due to evaporation and exfiltration.

JDS Primary Recommendation

JDS recommends Alternative 3.4.1 — the provision of a synthetic liner with check valves in a combination approach over the further-reduced Palmer Lake surface area (Alternative 3.2). This alternative provides the best of both worlds: it allows the Town and Committee to reduce liner costs over a further-reduced surface area while allowing the Town to fill and check valve levels and eliminate the need for groundwater supplementation. At the same time, the check valves allow the introduction of alluvial subsurface flows into the lake in the most natural way possible, and the synthetic liner isolates the lake from the negative effects of a lowered groundwater table.

JDS notes that the construction of such a liner system is a major constraining factor and possibly beyond the financial capabilities of the Committee and Town. That being said, JDS's next best recommendation is to go with Alternative 3.2 — reduce the size of the lake as described in that alternative. JDS has some questions as to whether the currently decreed Anchor Ditch water right will be able to keep up with projected evaporation and exfiltration out of the lake.

Lastly, in conjunction with whatever alternative is selected, JDS would encourage the Committee and Town to further evaluate the possibility of constructing the UPRR drainage culvert as depicted in Alternative 4.1. Though the construction of such a culvert may be relatively expensive and time consuming, it could develop into a major benefit for both the Town and the railroad in the long run.