The plaintiffs witnesses continued in the morning. Cameras were allowed in the courtroom, so there is local news coverage today. Roger Doyle calls David Thompson to the stand for the plaintiffs. He is a PhD Civil Engineer licensed in Nevada who taught as a professor at Texas Tech University. He is widely published. He describes himself as a surface-water hydrology specialist. He said his work in Texas is applicable to Northern Nevada since Texas also has playas and playa lakes similar to here. He was retained by the plaintiffs to determine how much local development and waste water production contributed to the flooding in Swan Lake. He concluded that impervious surfaces resulting from development contributed to the level of Swan Lake. He reviewed a number of reports commissioned by Reno and also water level data from Washoe County and the flow data from RSWRF. He reviewed detailed area maps to determine how impervious-surface areas had changed. He made several trips to the site to see the watershed (slopes that drain to the playa), developments, and detention basins first hand. He was there during a rain storm to see how the runoff flowed. He’s had some conversations with the plaintiffs’ expert Stoner. They take different approaches, but agree on the conclusions. He made a limited model (in a spreadsheet) that effectively “reverse engineered” the impact that development and effluent had on the level of Swan Lake. He was trying to determine the difference that development and effluent made; not a model that tracked all the factors determining the level of Swan Lake. Information in the Quad-Knopf study allowed him to determine the approximate section profile of Swan Lake (it’s not straight-sided like a swimming pool). For example; when 2 feet deep, it spread out to a certain area, but when 4 feet deep, it spread out to a different area. He calculated the volume of Swan Lake in 2017 as 9600 acre-feet. He described a conventional “water year” as running from October 1 to September 30. He considered the increased impervious area due to development between 2005 and 2017. He only considered increased runoff and effluent contributions. He said other contributions were insignificant. He used data from the Stead rain gauge (by the fire house) since it is the only one that is part of a national program. He described the rainfall for 2017 as “large” but not “historic”. He said we get a large rain event about every 10 years. The “frontal” storms are the ones of interest relative to flooding. These are produced by a broad front that brings precipitation to a large area. The “local” storms are largely thunder storms that do not occur frequently during the “water year”. He said that development close to the lake had the most impact in terms of runoff into the lake. He reported that in 1986 there were 1,039 acres that were developed. In 2005 the number had increased to 1,556 and then to 2,033 in 2016. He thinks Reno’s mitigation efforts had negligible effect. Some of the water will dissipate through percolation into the soil or evaporation. Infiltration and inflow to the sewer system is a factor, but it is included in the RSWRF outlet volume data. He calculated that RSWRF contributed 2500 acre feet to Swan Lake raising the level 1.7 feet. He had a key graph (105 Figure 3 – Stage Hydrograph) that showed what the lake level was, what the lake level would have been without the effluent, and what the lake level would have been without the effluent and the extra runoff produced by development. The top line shows the actual recorded level of Swan Lake. The second line down shows the lake level if the effluent from RSWRF had not gone to Swan Lake. The third line indicates the calculated lake level if the effluent were removed and the development had not increased the runoff. Thompson concluded that Pompe Drive would not have flooded absent the effluent and the excess runoff from development. Note the “BFE 4924” line. Reno has a permit to add water to the basin up to the Base Flood Elevation determined by FEMA. The storm of 2017 would not have caused flooding in 1986 because there was less effluent going into Swan Lake and less development to produce excess runoff. Thompson believes his assumptions are conservative and that Reno likely contributed a bigger fraction to the volume of Swan Lake. Thompson asserted that the Quad-Knopf study of 1986 gave specific instructions regarding development (not followed by Reno). “Did the city effectively deal with the increased runoff?” Answer “No.” “Did the city effectively address effluent discharge?” Answer “No.” The impervious surfaces caused by development made the flooding earlier, deeper, and last longer.” Reno’s expert agreed with Thompson as to the causes and effects, but disagreed as to the specific calculations regarding impervious surfaces. The lake level is now 0.7′ below the maximum in 2017, but still 2′ over Pompe Drive. Reno could have implemented effective mitigation that would substantially reduced the flooding, but the city did not follow good engineering practices to provide effective mitigation. Shipman handles the cross-examination. He made the point that Thompson didn’t look at any of the building plans for the developments or for the public infrastructure. They discussed how the impervious surface areas were determined. Thompson’s model doesn’t account for evaporation or percolation. He concedes this, but his objective was to determine how much volume was added by Reno’s actions. It was not to model the history of the lake level. Shipman’s questions were long-winded with dependent clauses so that it was not clear what he was asking. He had to restate many of the questions because Thompson did not understand them. He said his work did not depend on the work done by the previous witnesses DeMartini and Stoner. The flood contribution from Washoe County development was not included. Thompson did not consider runoff from the areas where the soil was undisturbed. He said that including this would not have made a significant difference. Under re-direct-examination, Thompson asserted that Reno contributed about 25% of the volume of the lake raising the level 1.7′. Shipman produced a table under re-cross-examination showing plaintiff properties and their elevations. They seemed to indicate that the properties were above the flood level. Roger asked Thompson about this. Thompson said that he hadn’t seen this information and that the table might show only the highest point on the properties.
This completed the plaintiffs’ case. It’s the turning point in the trial. The defense will now present their witnesses and make their case.
Chanden Sendall called Michael McMahon to the stand. He’s a hydro-meteorologist who had a long career forcasting rain falls for Lockheed and Boeing and then HDR Engineering. He now does consulting for the California Water Resources Board. He does “site specific probable precipitation studies” to determine how much water will likely flow to a dam. He used five rain gauges (NCEP) in the Lemmon Valley area. He used these to verify the results of radar (dual-doppler) images showing rain and snow in the area. The radar gauges gave detailed readings all over the area with measurements every 6 hours. He hopes to be within a 10% margin of error between the two measurement techniques. Some rain maps showed pretty even rain in the area while other times the rain was more concentrated in small areas. His opinion is that the rainfall of 2017 was unprecedented. It was the fact that so much fell in a short period, not the sum total. The area south of 395 received the most rain. His second opinion is that the snowfall is the highest seen in recent years. He used data for snow accumulation at Big Meadows 8 miles southwest of Peavine peak where there is a SNOTEL station providing automated measurements. He claimed this was the highest snow level recorded since 1984. Roger handled the cross examination. McMahon admitted that he had only made a single trip to the area, and it was the day before he gave a deposition. McMahon was reluctant to agree to points that he had made in his previous deposition. He had no personal experience of living in the valley and observing the precipitation first hand. Reviewing his results, Roger indicated that McMahon had three different results for certain areas. Roger asked “Which one is correct?” McMahon had no answer. Roger made the point that the data can be manipulated by picking different ranges of dates. McMahon concurred. Roger made the point that there were no rain gauges south of 395 where the radar showed the highest precipitation. McMahon admitted that there was no way to verify the radar results in this area. McMahon used three rain gauges outside the area for his calibration but didn’t use the one at Stead which is the only one that is part of the national system. Roger pressed on about the fees that McMahon was charging Reno for his services. McMahon did not dispute that it might be over $100,000 including McMahon’s assistants. Sendall’s re-direct examination was mostly repetitive. On re-cross-examination, Roger challenged McMahon’s opinion that the most rain fell in the shortest time in 2017. This is not what the graphs show.
Editorial note: McMahon came across as a little flip and humorous. He had the demeanor of a salesman.
Local TV coverage: