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Home My WebLink AboutWATERFIELD FOURTH FILING - MAJOR AMENDMENT / PDP - PDP180009 - SUBMITTAL DOCUMENTS - ROUND 2 -September 5, 2018 Blaine Mathisen, Project Engineer Northern Engineering 310 N. Howes Street, Suite 100 Fort Collins, CO 80524 RE: Waterfield Development – Status report on groundwater evaluation. Dear Blaine: This letter provides a brief report and status update on the groundwater monitoring and evaluation which is ongoing at the Waterfield development. The subject development is located between Vine Drive on its south, the Larimer and Weld Canal on its north, and North Timberline Road and Merganser Drive on its east and southeast (Figure 1). Monitoring To Date Numerous temporary geotechnical borings have been conducted at the site in various rounds of drilling, the most recent being January 2018. Some groundwater elevation data has been obtained from those borings. In April 2018, three monitoring wells and two piezometers were installed (Figure 1). Groundwater levels have been measured periodically in those during Summer 2018, including a few with continuous water level recorders (Figure 2). Four to six additional piezometers are schedule to be installed this month. The purpose of those additional piezometers are to fill in some spatial data gaps. In particular, some of those are targeted along the canal slope to provide additional resolution and confirmation of the steep water table gradient south of the canal (Figure 1). (Incidentally, the canal is not necessarily the sole source of that groundwater. Some portion of the site’s groundwater likely comes from the regional aquifer that lies above the site, to the north of the canal.) Figure 1 shows estimated groundwater elevations across the site based on approximated survey elevations and interpolated between monitoring points. An interesting observation from Figure 2 is that groundwater at monitoring well W-1 likely, and unsurprisingly, is influenced by changes in the canal depth, but groundwater at MW-1 does not appear to be influenced by the canal. MW-3, in the southwest corner of the site, may be influenced by the canal, but it is also near the Lake Canal Ditch to its southwest, plus MW-3 is also likely influenced by the flood- irrigated cornfield to its west. Note that groundwater at MW-3 has also shown a season-long rise. We assume it has by now reached, or will soon reach, its peak level here in late summer. WATERFIELD – GROUNDWATER STATUS UPDATE SEPTEMBER 5, 2018 Miller Groundwater Engineering, LLC P a g e | 2 Next Steps Our next steps will be to add the new data points to our preliminary (early 2018) mapping (Figure 3) once the additional piezometers are installed. Then later this month we will conduct in-field permeability tests using the site’s monitoring wells. Once that is completed we will organize the site data in a groundwater flow model to aid us in evaluating depth to water across the site relative to current grade and planned grades. The groundwater flow model will also be used to evaluate subsurface drainage for portions of the development. I would be happy to answer further questions. Sincerely, Calvin Miller, PE, PhD Miller Groundwater Engineering, LLC 4945 4945 4950 4950 4950 4955 4955 4955 4960 4960 4960 4965 4965 4965 4970 4970 oldTH oldTH oldTH oldTH MW-1 MW-2 MW-3 oldTH P-1 P-2 pipe oldTH oldTH oldTH oldTH W-1 P-5 P-6 P-7 P-3 P-4 P-8 205000 205200 205400 205600 205800 206000 206200 206400 206600 206800 207000 207200 207400 207600 207800 208000 208200 208400 easting (feet) 134200 134400 134600 134800 135000 135200 135400 135600 135800 136000 136200 136400 136600 136800 137000 137200 137400 northing (feet) Figure 2018-8-20c: Estimated (interpolated) groundwater surface elevation. existing MWs and PZs in blue (5) -7.5 -7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 4/26 5/3 5/10 5/17 5/24 5/31 6/7 6/14 6/21 6/28 7/5 7/12 7/19 7/26 8/2 8/9 8/16 8/23 8/30 L&W Canal Stage (-1 x feet) Groundwater depth from ground surface (ft) 2018 Date (M/DD) Waterfield: Seasonal water levels, Summer 2018 MW-3 W-1 MW-1 L&W Canal note: canal depth data contains some offset errors due to sensor movement DRAFT 4950 4950 4950 4950 4950 4955 4955 4955 4955 4955 4955 4955 4960 4960 4960 4960 4960 4960 4960 4960 4960 4960 4960 4960 4960 4965 4965 4965 4965 4965 4970 4970 4970 4970 4975 4975 4975 4975 4980 4980 4980 4980 4980 4985 4985 4985 4985 4985 4985 4985 4985 4990 4990 4995 5000 4940 4945 4950 4955 TB-8 6 4954 TB-4? 13.5 4957 TB-14 > 9 4939 TB-9? 7 4956 TB-16? 15.5 4945 TB-2 5.5 4951 lockedMW na TB-7 3 4955 TB-13? 8.5 4950 3127800 3128200 3128600 3129000 3129400 3129800 3130200 3130600 3131000 easting (feet) 1460000 1460200 1460400 1460600 1460800 1461000 1461200 1461400 1461600 1461800 1462000 1462200 1462400 1462600 1462800 1463000 1463200 1463400 northing (feet) wet area irrigation canal irrigation ditch ? ? A A' Project: Waterfield development /Waterfield/Figure1.srf Jan/5/2018 Figure 3. Estimated water table surface (blue contours) and existing ground topography (black/grey contours). Note: preliminary drawings - for illustration only A A' Legend location ID depth to water (ft bgs) on 1/4/2018 TB-8 6 4954 estimated water table elevation NEW PZs in red (6) some of the old test holes in black (some still existing) all locations and basemap are approximate (not surveyed), elevation reference points spotted from topo (not surveyed). Miller Groundwater Engineering, LLC /Waterfield/mapping/NEfiles8-18-18/OtherFigures.srf 8/20/2018